JP7222309B2 - vehicle steering system - Google Patents

Description

The present invention relates to a vehicle steering system.

2. Description of the Related Art An electric power steering system (EPS), which is one of vehicle steering systems, applies an assist force (steering assist force) to a steering system of a vehicle using the rotational force of a motor. The EPS applies the driving force of a motor controlled by electric power supplied from an inverter to a steering shaft or a rack shaft as an assisting force through a transmission mechanism including a speed reduction mechanism.

For example, a power steering device is disclosed that gradually increases the steering assist force during low-speed driving such as parking in a garage, and gradually returns the increased steering assist force to the normal steering assist force when parking is completed. (For example, Patent Document 1).

Patent No. 3891275

In general, control is performed to reduce the steering assist force during low-speed driving. However, if the steering assist force is uniformly lowered during low-speed driving, it becomes difficult for the driver to recognize the steering angle at which the steering angle is near zero. In particular, when the vehicle is reversed in order to park the vehicle in a parking area or the like, it becomes difficult for the driver to get a sense of steering when visually confirming the safety behind the vehicle.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle steering system capable of improving steering feel.

In order to achieve the above object, a vehicle steering system according to one aspect of the present invention is a vehicle steering system that assists and controls a steering system of a vehicle by driving and controlling a motor that assists steering force. The vehicle has a first mode and a second mode different from the first mode as operation modes of the vehicle. The rate of change of the target steering torque of the motor is equal to or higher than the first mode in the second mode, and the rate of change of the target steering torque in the second mode is smaller than that in the first mode in regions other than the predetermined region.

As a desirable aspect of the steering system for a vehicle, when a predetermined operation is detected, a determination unit for determining the second mode, and a rate of change gradually increases as the absolute value of the steering angle of the steering wheel increases. generating a first torque signal that increases along a decreasing curve; multiplying a second torque signal generated based on the first torque signal by a correction gain to generate a third torque signal; a target steering torque generation unit that generates the target steering torque by adding a fourth torque signal, the target steering torque generation unit having a positive correction gain of less than 1 in the second mode. and generating a fourth torque signal having a slope larger than that of the first torque signal when the absolute value of the steering angle is zero.

According to the above configuration, the burden on the driver in the second mode can be reduced, and the steering feeling can be improved.

As a preferred aspect of the vehicle steering system, it is preferable that the fourth torque signal in the second mode has a constant value in a region where the steering angle is equal to or greater than a predetermined value.

As a result, the target steering torque in the second mode can be reduced, and the operation of the steering wheel can be lightened.

As a preferred aspect of the vehicle steering system, it is preferable that the target steering torque generator sets the correction gain to 1 and the fourth torque signal to zero in the first mode.

As a result, a target steering torque suitable for the first mode is obtained.

As a desirable aspect of the vehicle steering system, the target steering torque in the second mode is smaller than the target steering torque in the first mode.

This makes it possible to lighten the operation of the steering wheel.

According to the present invention, it is possible to provide a vehicle steering system capable of improving the steering feel.

FIG. 1 is a diagram showing a general configuration of an electric power steering system. FIG. 2 is a schematic diagram showing the hardware configuration of a control unit that controls the electric power steering device. FIG. 3 is a diagram showing an example of an internal block configuration of a control unit in the electric power steering system. FIG. 4 is a structural diagram showing an installation example of the steering angle sensor. 5 is a diagram illustrating an example of an internal block configuration of a control unit according to the first embodiment; FIG. FIG. 6 is an explanatory diagram of the steering direction. 7 is a flowchart illustrating an operation example of the control unit according to the first embodiment; FIG. FIG. 8 is a block diagram showing a configuration example of a target steering torque generator according to the first embodiment. FIG. 9 is a diagram showing a characteristic example of a basic map held by the basic map unit. FIG. 10 is a diagram showing a characteristic example of a damper gain map held by a damper gain map section. FIG. 11 is a diagram showing an example of characteristics of the hysteresis corrector. FIG. 12 is a block diagram showing one configuration example of the steering reaction force correction unit. FIG. 13 is a diagram showing an example of a correction torque map. FIG. 14 is a diagram showing an example of the target steering torque output from the target steering torque generator. 15 is a block diagram showing a configuration example of a twist angle control unit according to the first embodiment; FIG. 16 is a diagram illustrating an example of an internal block configuration of a control unit according to the second embodiment; FIG. FIG. 17 is a block diagram showing a configuration example of a target steering torque generator according to the second embodiment. FIG. 18 is a block diagram showing a configuration example of the SAT information corrector. FIG. 19 is an image diagram showing how torque is generated from the road surface to the steering wheel. FIG. 20 is a diagram showing a characteristic example of the steering torque sensitive gain. FIG. 21 is a diagram showing a characteristic example of the vehicle speed sensitive gain. FIG. 22 is a diagram showing a characteristic example of the steering angle sensitive gain. FIG. 23 is a diagram showing a setting example of the upper limit value and the lower limit value of the torque signal in the limiting section. 24 is a block diagram illustrating a configuration example of a twist angle control unit according to the second embodiment; FIG. FIG. 25 is a diagram showing a configuration example of the SBW system in correspondence with the general configuration of the electric power steering apparatus shown in FIG. 26 is a block diagram showing an internal block configuration of a control unit according to Embodiment 3. FIG. FIG. 27 is a diagram showing a configuration example of a target steering angle generation unit. FIG. 28 is a diagram showing a configuration example of a turning angle control section. FIG. 29 is a flowchart illustrating an operation example of the third embodiment;

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates in detail, referring drawings for the form (henceforth embodiment) for implementing invention. In addition, the present invention is not limited by the following embodiments. In addition, components in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that fall within a so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined as appropriate.

(Embodiment 1)
FIG. 1 is a diagram showing a general configuration of an electric power steering system. An electric power steering system (EPS), which is one of vehicle steering systems, is composed of a column shaft (steering shaft, steering wheel shaft) 2 of a steering wheel 1, a speed reduction mechanism 3, a universal joint in order of transmission of force given by a steerer. 4a, 4b, pinion rack mechanism 5, tie rods 6a, 6b, and hub units 7a, 7b to steerable wheels 8L, 8R. The column shaft 2 having the torsion bar is provided with a torque sensor 10 for detecting the steering torque Ts of the steering wheel 1 and a steering angle sensor 14 for detecting the steering angle θh. 20 is connected to the column shaft 2 via the speed reduction mechanism 3 . A control unit (ECU) 30 that controls the electric power steering apparatus is supplied with power from a battery 13 and receives an ignition key signal via an ignition key 11 . The control unit 30 calculates the current command value of the assist (steering assistance) command based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and compensates the current command value. The current supplied to the motor 20 is controlled by the voltage control command value Vref obtained by applying the

The control unit 30 is connected to an in-vehicle network such as a CAN (Controller Area Network) 40 that exchanges various types of vehicle information. Also, the control unit 30 can be connected to a non-CAN 41 for transmitting/receiving communications other than the CAN 40, analog/digital signals, radio waves, and the like.

The control unit 30 is mainly composed of a CPU (including MCU, MPU, etc.). FIG. 2 is a schematic diagram showing the hardware configuration of a control unit that controls the electric power steering device.

A control computer 1100 constituting the control unit 30 includes a CPU (Central Processing Unit) 1001, a ROM (Read Only Memory) 1002, a RAM (Random Access Memory) 1003, an EEPROM (Electrically Erasable Programmable ROM) 1004, an interface (I/F ) 1005, an A/D (Analog/Digital) converter 1006, a PWM (Pulse Width Modulation) controller 1007, etc., which are connected to a bus.

The CPU 1001 is a processing device that executes a computer program for controlling the electric power steering device (hereinafter referred to as a control program) to control the electric power steering device.

A ROM 1002 stores a control program for controlling the electric power steering device. Also, the RAM 1003 is used as a work memory for operating the control program. The EEPROM 1004 stores control data and the like input/output by the control program. The control data is used in the control computer program developed in the RAM 1003 after the control unit 30 is powered on, and overwritten in the EEPROM 1004 at a predetermined timing.

A ROM 1002, a RAM 1003, an EEPROM 1004, and the like are storage devices that store information, and are storage devices (primary storage devices) that the CPU 1001 can directly access.

The A/D converter 1006 receives signals such as the steering torque Ts, the current detection value Im of the motor 20, and the steering angle θh, and converts them into digital signals.

Interface 1005 is connected to CAN 40 . The interface 1005 is for receiving a vehicle speed V signal (vehicle speed pulse) from the vehicle speed sensor 12 .

A PWM controller 1007 outputs a PWM control signal for each UVW phase based on a current command value for the motor 20 .

FIG. 3 is a diagram showing an example of an internal block configuration of a control unit in the electric power steering system. The steering torque Ts and the vehicle speed Vs are input to the current command value calculator 31 . Based on the steering torque Ts and the vehicle speed Vs, the current command value calculation unit 31 refers to a pre-stored lookup table (assist map, etc.) to obtain a current command value Iref1, which is a control target value for the current supplied to the motor 20. to calculate

The compensation signal generator 34 generates a compensation signal CM. The compensation signal generator 34 includes a convergence estimator 341 , an inertia estimator 342 , and a self aligning torque (SAT) estimator 343 . The convergence estimator 341 estimates the yaw rate of the vehicle based on the angular velocity of the motor 20 and estimates a compensation value for improving the yaw convergence of the vehicle by braking the whirling motion of the steering wheel 1 . The inertia estimator 342 estimates the inertia force of the motor 20 based on the angular acceleration of the motor 20, and estimates a compensation value for compensating the inertia force of the motor 20 in order to improve responsiveness. The SAT estimator 343 estimates the self-aligning torque T _SAT based on the steering torque Ts, the assist torque, and the angular velocity and angular acceleration of the motor 20, and uses the self-aligning torque as a reaction force to determine a compensation value for compensating the assist torque. presume. In addition to the convergence estimator 341, the inertia estimator 342, and the SAT estimator 343, the compensation signal generator 34 may include an estimator that estimates other compensation values. Compensation signal CM is obtained by adding the compensation value of inertia estimating unit 342 and the compensating value of SAT estimating unit 343 in addition unit 344, and adding this addition value and the compensation value of convergence estimating unit 341 in addition unit 345. is the added value. In the present disclosure, the self-aligning torque T _SAT estimated by the SAT estimator 343 is also output to the target steering torque generator 200, which will be described later.

In the adder 32A, the compensation signal CM from the compensation signal generator 34 is added to the current command value Iref1. By adding the compensation signal CM, the current command value Iref1 is compensated for the characteristics of the steering system system, and the convergence and Inertia characteristics and the like are improved. Then, the current command value Iref1 passes through the adder 32A to become the current command value Iref2 whose characteristics are compensated, and the current command value Iref2 is input to the current limiter 33. FIG. Current limiter 33 limits the maximum current of current command value Iref2 to generate current command value Irefm. The current command value Irefm is input to the subtraction section 32B, and the deviation I (Irefm−Im) from the current detection value Im fed back from the motor 20 side is calculated by the subtraction section 32B. The deviation I is input to a PI control section 35 for improving steering operation characteristics. Then, the voltage control command value Vref whose characteristics are improved by the PI control unit 35 is input to the PWM control unit 36, and the motor 20 is PWM-driven via the inverter circuit 37 as a motor driving unit. A current detection value Im of the motor 20 is detected by the current detector 38 and fed back to the subtractor 32B. The inverter circuit 37 uses a field effect transistor (hereinafter referred to as FET) as a drive element, and is configured as a FET bridge circuit.

In the assist control of the conventional electric power steering system, the steering torque applied by the driver's manual input is detected by a torque sensor as the torsion torque of the torsion bar, and the motor current is mainly used as the assist current corresponding to the torque. controlling. However, when the control is performed by this method, the steering torque may vary depending on the steering angle due to the difference in road surface conditions (for example, inclination). Steering torque may also be affected by variations in motor output characteristics due to long-term use.

FIG. 4 is a structural diagram showing an installation example of the steering angle sensor.

The column shaft 2 is provided with a torsion bar 2A. A road surface reaction force Rr and road surface information (frictional resistance μ of the road surface) act on the steered wheels 8L and 8R. An upper angle sensor is provided on the handle side of the column shaft 2 with the torsion bar 2A interposed therebetween. A lower angle sensor is provided on the steering wheel side of the column shaft 2 with the torsion bar 2A interposed therebetween. The upper angle sensor detects the steering wheel angle _θ1 and the lower angle sensor detects the column angle _θ2 . The steering angle θh is detected by a steering angle sensor provided above the column shaft 2 . The twist angle Δθ of the torsion bar is expressed by the following equation (1) from the deviation of the steering wheel angle _θ1 and the column angle _θ2 . Also, the torsion bar torque Tt is expressed by the following equation (2) using the twist angle Δθ of the torsion bar expressed by the equation (1). Kt is the spring constant of the torsion bar 2A.

Δθ=θ ₂ −θ ₁ (1)

Tt=−Kt×Δθ (2)

Torsion bar torque Tt can also be detected using a torque sensor. In this embodiment, the torsion bar torque Tt is also treated as the steering torque Ts.

5 is a diagram illustrating an example of an internal block configuration of a control unit according to the first embodiment; FIG.

The control unit 30 includes a target steering torque generation section 200, a twist angle control section 300, a steering direction determination section 400, and a conversion section 500 as internal block configurations.

In this embodiment, the driver's steering is assist-controlled by the motor 20 of the EPS steering system/vehicle system 100 . The EPS steering system/vehicle system 100 includes, in addition to the motor 20, an angle sensor, an angular velocity calculator, and the like.

The target steering torque generation unit 200 generates a target steering torque Tref, which is a target value of the steering torque when performing assist control on the steering system of the vehicle in the present disclosure. Conversion unit 500 converts target steering torque Tref into target twist angle Δθref. The torsion angle control unit 300 generates a motor current command value Iref, which is a control target value for current supplied to the motor 20 .

The torsion angle control section 300 calculates a motor current command value Iref such that the torsion angle Δθ becomes the target torsion angle Δθref. Motor 20 is driven by a motor current command value Iref.

The steering direction determination unit 400 determines whether the steering direction is right turn or left turn based on the motor angular velocity ωm output from the EPS steering system/vehicle system 100, and outputs the determination result as the steering state signal STs. FIG. 6 is an explanatory diagram of the steering direction.

The steering state indicating whether the steering direction is right or left can be obtained from the relationship between the steering angle θh and the motor angular velocity ωm as shown in FIG. 6, for example. That is, when the motor angular velocity ωm has a positive value, it is determined as "right turn", and when it has a negative value, it is determined as "left turn". Instead of the motor angular velocity ωm, an angular velocity calculated by performing a velocity calculation on the steering angle θh, the steering wheel angle _θ1 , or the column angle _θ2 may be used.

Conversion unit 500 converts target steering torque Tref generated by target steering torque generation unit 200 into target twist angle Δθref using the relationship of equation (2) above.

Next, a basic operation example of the control unit of the first embodiment will be described. 7 is a flowchart illustrating an operation example of the control unit according to the first embodiment; FIG.

The steering direction determining unit 400 determines whether the steering direction is right-turning or left-turning based on the sign of the motor angular velocity ωm output from the EPS steering system/vehicle system 100, and uses the determination result as the steering state signal STs to determine the target steering direction. It is output to the torque generator 200 (step S10).

Target steering torque generator 200 generates target steering torque Tref based on vehicle speed Vs, vehicle speed determination signal Vfail, steering state signal STs, steering angle θh, and actual yaw rate γre (step S20).

Conversion unit 500 converts target steering torque Tref generated by target steering torque generation unit 200 into target twist angle Δθref (step S20). The target twist angle Δθref is output to the twist angle control section 300 .

The torsion angle control unit 300 calculates a motor current command value Iref based on the target torsion angle Δθref, the steering angle θh, the torsion angle Δθ, and the motor angular velocity ωm (step S30).

Current control is performed based on the motor current command value Iref output from the torsion angle control unit 300, and the motor 20 is driven (step S40).

FIG. 8 is a block diagram showing a configuration example of a target steering torque generator according to the first embodiment. As shown in FIG. 8, the target steering torque generation unit 200 includes a basic map unit 210, a multiplication unit 211, a sign extraction unit 213, a differentiation unit 220, a damper gain map unit 230, a hysteresis correction unit 240, a SAT information correction unit 250, Multiplication units 260 and 264 , addition units 261 , 262 and 265 and a steering reaction force correction unit 280 are provided. FIG. 9 is a diagram showing a characteristic example of a basic map held by the basic map unit. FIG. 10 is a diagram showing a characteristic example of a damper gain map held by a damper gain map section.

The steering angle θh and the vehicle speed Vs are input to the basic map portion 210 . Basic map unit 210 uses the basic map shown in FIG. 9 to output torque signal Tref_a0 having vehicle speed Vs as a parameter. That is, basic map unit 210 outputs torque signal Tref_a0 corresponding to vehicle speed Vs.

As shown in FIG. 9, the torque signal Tref_a0 has a characteristic that it increases as the magnitude (absolute value) |θh| of the steering angle θh increases. Also, the torque signal Tref_a has a characteristic that it increases as the vehicle speed Vs increases. In addition, in FIG. 9, the map is configured according to the magnitude |θh| of the steering angle θh, but the map may be configured according to the positive or negative steering angle θh. In this case, the value of the torque signal Tref_a0 takes a positive or negative value, and sign calculation, which will be described later, is unnecessary.

A sign extractor 213 extracts the sign of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. Accordingly, the sign extractor 213 outputs "1" when the sign of the steering angle θh is "+" and outputs "-1" when the sign of the steering angle θh is "-".

The steering angle θh is input to the differentiating section 220 . A differentiating section 220 differentiates the steering angle θh to calculate a steering angular velocity ωh, which is angular velocity information. The differentiation section 220 outputs the calculated steering angular velocity ωh to the multiplication section 260 .

The vehicle speed Vs is input to the damper gain map section 230 . The damper gain map section 230 outputs a damper gain _DG according to the vehicle speed Vs using the vehicle speed sensitive damper gain map shown in FIG.

As shown in FIG. 10, the damper gain _DG has the characteristic of gradually increasing as the vehicle speed Vs increases. The damper gain _DG may be varied according to the steering angle θh.

Multiplying section 260 multiplies steering angular velocity ωh output from differentiating section 220 by damper gain _DG output from damper gain map section 230, and outputs the result to adding section 262 as torque signal Tref_b.

The steering direction determination unit 400 makes determinations as shown in FIG. 6, for example. The steering angle θh, the vehicle speed Vs, and the steering state signal STs, which is the determination result shown in FIG. The hysteresis correction unit 240 calculates the torque signal Tref_c using the following equations (3) and (4) based on the steering angle θh and the steering state signal STs. In the following equations (3) and (4), x is the steering angle θh, y _R =Tref_c and y _L =Tref_c are the torque signal Tref_c. Also, the coefficient a is a value greater than 1, and the coefficient c is a value greater than 0. The coefficient Ahys indicates the output width of the hysteresis characteristic, and the coefficient c indicates the roundness of the hysteresis characteristic.

y _R =Ahys{1-a ^-c(xb) } (3)

y _L =-Ahys {1-a ^c(x-b') } (4)

During right turn steering, the torque signal Tref_c(y _R ) is calculated using the above equation (3). During left-turn steering, the torque signal Tref_c(y _L ) is calculated using the above equation (4). When switching from right-turn steering to left-turn steering, or when switching from left-turn steering to right-turn steering, the final coordinates (x ₁ , y ₁ ) of the previous values of the steering angle θh and the torque signal Tref_c are Based on the value of , a coefficient b or b' shown in the following equation (5) or (6) is substituted into the above equations (3) and (4) after steering switching. As a result, continuity before and after steering switching is maintained.

b=x ₁ +(1/c) log _a {1−(y ₁ /Ahys)} (5)

b′=x ₁ −(1/c) log _a {1−(y ₁ /Ahys)} (6)

The above formulas (5) and (6) can be derived by substituting x ₁ for x and y ₁ for y _R and y _L in the above formulas (3) and (4). .

For example, when Napier's number e is used as the coefficient a, the above formulas (3), (4), (5), and (6) are respectively the following formulas (7), (8), and (9 ) and (10).

y _R =Ahys[1-exp{-c(xb)}] (7)

y _L =-Ahys[{1-exp{c(xb')}] (8)

b=x ₁ +(1/c)log _e {1−(y ₁ /Ahys)} (9)

b′=x ₁ −(1/c)log _e {1−(y ₁ /Ahys)} (10)

FIG. 11 is a diagram showing an example of characteristics of the hysteresis corrector. In the example shown in FIG. 11, in the above equations (9) and (10), Ahys = 1 [Nm], c = 0.3, starting from 0 [deg], +50 [deg], -50 FIG. 10 shows a characteristic example of a hysteresis-corrected torque signal Tref_c when steering is performed by [deg]. As shown in FIG. 11, the torque signal Tref_c output from the hysteresis correction unit 240 has hysteresis characteristics such as the origin of 0→L1 (thin line)→L2 (dashed line)→L3 (thick line).

Ahys, which is a coefficient representing the output width of the hysteresis characteristic, and c, which is a coefficient representing roundness, may be variable according to one or both of the vehicle speed Vs and the steering angle θh.

Further, the steering angular velocity ωh is obtained by a differential operation with respect to the steering angle θh, but is moderately subjected to low-pass filter (LPF) processing in order to reduce the influence of high-frequency noise. Alternatively, the differential operation and LPF processing may be performed using a high-pass filter (HPF) and gain. Furthermore, instead of the steering angle θh, the steering angular velocity ωh may be calculated by performing differentiation and LPF processing on the steering wheel angle θ1 detected by the upper angle sensor or the column angle θ2 detected by the lower angle sensor. . The motor angular velocity ωm may be used as the angular velocity information instead of the steering angular velocity ωh, in which case the differentiating section 220 becomes unnecessary.

Returning to FIG. 8, the multiplication unit 211 multiplies the torque signal Tref_a0 output from the basic map unit 210 by the sign of the steering angle θh output from the sign extraction unit 213, and outputs the torque signal Tref_a to the addition unit 261. Output. Thereby, a torque signal Tref_a corresponding to the positive/negative steering angle θh is obtained.

The torque signal Tref_a, the torque signal Tref_b, and the torque signal Tref_c obtained as described above are added by adders 261 and 262 to obtain the torque signal Tref_e.

The torque signal Tref_a in this embodiment corresponds to the "first torque signal" of the present disclosure. Also, the torque signal Tref_e in the present embodiment corresponds to the "second torque signal" of the present disclosure.

FIG. 12 is a block diagram showing one configuration example of the steering reaction force correction unit. As shown in FIG. 12 , the steering reaction force correction section 280 includes a correction gain generation section 281 , a correction torque map 282 , a sign extraction section 283 and a multiplication section 284 .

The steering reaction force correction unit 280 receives the steering angle θh and the low-speed operation mode signal Pf output from the low-speed operation mode detection unit 15 (see FIG. 1).

Here, the "low speed operation mode (second mode)" will be described. In this embodiment, the "low-speed driving mode (second mode)" refers to, for example, when the vehicle is parked in a parking lot, when the vehicle is moved to a predetermined stop position, or when the vehicle is retreated to return from a dead end. This driving mode is selected when the driver performs a predetermined low-speed driving mode transition operation such as moving the vehicle. That is, the low-speed driving mode (second mode) in the present embodiment is a driving mode for moving the vehicle at low speed when the above-described predetermined low-speed driving mode transition operation is performed.

The low-speed operation mode detection unit 15 is a component that detects that the driver has performed a predetermined low-speed operation mode transition operation and outputs a low-speed operation mode signal Pf. The low-speed driving mode detection unit 15 may detect, for example, that a "parking button" provided on the center console of the vehicle or the like is pushed by the driver, and output the low-speed driving mode signal Pf. . In addition, the low-speed driving mode detection unit 15 selects the position of "reverse (backward)", "parking F (forward)", or "parking B (backward)" by, for example, operating the shift knob of the vehicle by the driver. Alternatively, the low-speed operation mode signal Pf may be output by detecting that it has been turned on. Here, "parking F (forward)" indicates the position selected when moving forward in the low-speed operation mode (second mode), and "parking B (reverse)" indicates the position in which the vehicle moves backward in the low-speed operation mode (second mode). indicates the position to be selected when The means for selecting the low-speed operation mode (second mode) by the driver may be a mode other than the above, and the present invention is not limited by the means for selecting the low-speed operation mode (second mode) by the driver. do not have. In the following description, the normal operation mode when the low speed operation mode (second mode) is not selected is also referred to as "drive mode (first mode)". That is, in the present disclosure, the low-speed operation mode detection unit 15 detects a predetermined low-speed operation mode transition operation, and determines the low-speed operation mode (second mode) different from the drive mode (first mode). ” corresponds to

The correction gain generator 281 outputs a correction gain G (G is a positive value less than 1) according to the low speed operation mode signal Pf in the low speed operation mode (second mode). Specifically, the correction gain generator 281 outputs, for example, a correction gain G=0.3 in the low speed operation mode (second mode). Further, the correction gain generator 281 outputs a correction gain G=1 in the drive mode (first mode). The value of the correction gain G in the low speed operation mode (second mode) is an example, and is not limited to 0.3. The value of the correction gain G in the low speed operation mode (second mode) can be a predetermined positive value less than one.

In the correction torque map 282, a correction torque corresponding to the magnitude |θh| of the steering angle θh is set. The correction torque map 282 outputs a correction torque signal Tref_p0 corresponding to the magnitude |θh| of the steering angle θh.

A sign extractor 283 extracts the sign of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. Thus, the sign extractor 283 outputs "1" when the sign of the steering angle θh is "+" and outputs "-1" when the sign of the steering angle θh is "-".

The multiplication unit 284 multiplies the correction torque signal Tref_p0 output from the correction torque map 282 by the sign of the steering angle θh output from the sign extraction unit 283, and outputs the result as a correction torque signal Tref_p. Thereby, a correction torque signal Tref_p corresponding to the positive/negative steering angle θh is obtained.

FIG. 13 is a diagram showing an example of a correction torque map. In FIG. 13, the horizontal axis indicates the absolute value |θh| of the steering angle θh, and the vertical axis indicates the torque.

In FIG. 13, an example of the torque signal Tref_a0 is indicated by a dashed line, and a corrected torque signal Tref_p0 is indicated by a solid line. In FIG. 13, the map is formed according to the magnitude (absolute value) |θh| of the steering angle θh, but the map may be formed according to the positive or negative steering angle θh. In this case, the value of the correction torque signal Tref_p0 can take positive and negative values. Correction torque map 282 may be stored in EEPROM 1004 or the like of control computer 1100 constituting control unit 30, or may be held by steering reaction force correction section 280, for example.

As shown in FIG. 13, the correction torque signal Tref_p0 gradually decreases in rate of change as the absolute value |θh| of the steering angle θh increases in a region where the absolute value |θh| It has a characteristic that increases along a curve of Further, as shown in FIG. 13, the correction torque signal Tref_p0 has a constant value |Tc| in a region where the absolute value |θh| of the steering angle θh is equal to or greater than the threshold value |θh_th|. In this embodiment, the slope K2 of the corrected torque signal Tref_p0 at the absolute value |θh|=0 of the steering angle θh is set to a value larger than the slope K1 at the absolute value |θh|=0 of the steering angle θh of the torque signal Tref_a0. . The threshold value |θh_th| and the constant value |Tc| can be arbitrary predetermined values.

The steering reaction force correction unit 280 outputs a correction torque signal Tref_p according to the low speed operation mode signal Pf. The steering reaction force correction unit 280 outputs a correction torque signal Tref_p corresponding to the steering angle θh in the low speed operation mode (second mode). Further, the steering reaction force correction unit 280 outputs a correction torque signal Tref_p=0 in the drive mode (first mode) regardless of the steering angle θh.

Returning to FIG. 8, the multiplication unit 264 multiplies the torque signal Tref_e output from the addition unit 261 by the correction gain G output from the steering reaction force correction unit 280, and outputs the result as a torque signal Tref_f to the addition unit 265. . Addition unit 265 adds correction torque signal Tref_p output from steering reaction force correction unit 280 to torque signal Tref_f output from multiplication unit 264, and outputs the result as target steering torque Tref. That is, the target steering torque Tref can be expressed by the following equation (11).

Tref=(Tref_e)×G+Tref_p
=Tref_f+Tref_p (11)

The torque signal Tref_f in this embodiment corresponds to the "third torque signal" of the present disclosure. Further, the correction torque signal Tref_p in this embodiment corresponds to the "fourth torque signal" of the present disclosure.

FIG. 14 is a diagram showing an example of the target steering torque output from the target steering torque generator. In FIG. 14, the horizontal axis indicates the steering angle θh, and the vertical axis indicates the torque.

In FIG. 14, an example of the target steering torque in the drive mode is indicated by a dashed line, and an example of the target steering torque in the low-speed driving mode is indicated by a solid line.

In the drive mode (first mode), as described above, the torque signal Tref_e (second torque signal) is multiplied by the correction gain G=1, and the correction torque signal Tref_p (fourth torque signal)=0 is added. . As a result, target steering torque Tref=torque signal Tref_e (second torque signal), and target steering torque Tref suitable for the drive mode (first mode) can be obtained.

In the low-speed operation mode (second mode), as described above, the torque signal Tref_e (second torque signal) is multiplied by a positive correction gain G less than 1 (for example, G=0.3) to obtain the torque signal Tref_f. (third torque signal), and the slope of the torque signal Tref_f (third torque signal) at the absolute value |θh|=0 of the steering angle θh is greater than that of the torque signal Tref_a (first torque signal). A correction torque signal Tref_p (fourth torque signal) is added to generate a target steering torque Tref. As a result, as shown in FIG. 14, in the low-speed operation mode (second mode), the target steering torque Tref can be made smaller than in the drive mode (first mode), and the operation of the steering wheel 1 can be lightened. . Further, as shown in FIG. 14, in a predetermined region around the steering angle θh of 0 (the region indicated by the dashed line in FIG. 14), it is possible to increase the change in the steering force with respect to the change in the steering angle θh. . In other words, in a predetermined region where the absolute value |θh| Thus, the change rate of the target steering torque Tref in the low-speed operation mode (second mode) is smaller than that in the drive mode (first mode) in areas other than the predetermined area. This makes it easier for the driver to recognize that the steering angle is zero. Therefore, the burden on the driver can be reduced, and the steering feeling can be improved.

In the example shown in FIG. 8, the torque signal Tref_e (second torque signal) obtained by adding the torque signal Tref_a (first torque signal), torque signal Tref_b, and torque signal Tref_c is multiplied by the correction gain G. to generate the torque signal Tref_f (third torque signal). A mode may be employed in which the torque signal Tref_f (third torque signal) is generated by adding after multiplying by the gain G.

The twist angle control section 300 (see FIG. 5) of the first embodiment will be described below with reference to FIG.

15 is a block diagram showing a configuration example of a twist angle control unit according to the first embodiment; FIG. The torsion angle control unit 300 calculates a motor current command value Iref based on the target torsion angle Δθref, the torsion angle Δθ, the steering angle θh, and the motor angular velocity ωm. The torsion angle control unit 300 includes a torsion angle feedback (FB) compensation unit 310, a speed control unit 330, a stabilization compensation unit 340, an output limiter 350, a steering angle disturbance compensation unit 360, a subtraction unit 361, an addition unit 363, and a deceleration unit. A ratio section 370 is provided.

The target twist angle Δθref output from the conversion unit 500 is added to the subtraction unit 361 . The twist angle Δθ is subtracted and input to the subtractor 361 . The steering angle θh is input to the steering angle disturbance compensator 360 . The motor angular velocity ωm is input to stabilization compensator 340 .

The torsion angle FB compensator 310 multiplies the deviation Δθ0 between the target torsion angle Δθref and the torsion angle Δθ calculated by the subtraction unit 361 by a compensation value CFB (transfer function) so that the torsion angle Δθ follows the target torsion angle Δθref. A target column angular velocity ωref1 is output. The target column angular velocity ωref1 is added and output to the adder 363 . The compensation value CFB may be a simple gain Kpp or a generally used compensation value such as a PI control compensation value.

A steering angle disturbance compensator 360 multiplies the steering angle θh by a compensation value Ch (transfer function) and outputs a target column angular velocity ωref2. The target column angular velocity ωref2 is added and output to the adder 363 .

Adder 363 adds target column angular velocity ωref1 and target column angular velocity ωref2, and outputs the result to speed controller 330 as target column angular velocity ωref. As a result, the influence of changes in the steering angle θh input from the driver on the torsion bar torsion angle Δθ can be suppressed, and the followability of the torsion bar torsion angle Δθ to the target torsion angle Δθref for rapid steering can be improved.

When the steering angle θh changes due to steering by the driver, the change in the steering angle θh affects the torsion angle Δθ as a disturbance, causing a deviation from the target torsion angle Δθref. In particular, for sudden steering, the deviation from the target torsion angle Δθref due to the change in the steering angle θh is remarkable. The basic purpose of the steering angle disturbance compensator 360 is to reduce the influence of the steering angle θh as this disturbance.

Speed control unit 330 calculates a motor current command value Is such that column angular velocity ωc follows target column angular velocity ωref by IP control (proportional leading PI control). As shown in FIG. 15, the column angular velocity ωc may be a value obtained by multiplying the motor angular velocity ωm by the reduction ratio 1/N of the reduction ratio unit 370, which is a reduction mechanism.

The subtraction unit 333 calculates the difference (ωref−ωc) between the target column angular velocity ωref and the column angular velocity ωc. The integrator 331 integrates the difference (ωref−ωc) between the target column angular velocity ωref and the column angular velocity ωc, and adds the integration result to the subtractor 334 .

The torsional angular velocity ωt is also output to the proportional section 332 . The proportional section 332 performs proportional processing with the gain Kvp on the column angular velocity ωc, and subtracts and inputs the result of the proportional processing to the subtraction section 334 . The result of subtraction by the subtractor 334 is output as the motor current command value Is. Note that the speed control unit 330 performs PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model reference control, instead of IP control. The motor current command value Is may be calculated by a commonly used control method such as control.

The output limiter 350 is preset with an upper limit value and a lower limit value for the motor current command value Is. The motor current command value Iref is output by limiting the upper and lower limits of the motor current command value Is.

Note that the configuration of the torsion angle control unit 300 in the present embodiment is an example, and a configuration different from the configuration shown in FIG. 15 may be used. For example, the torsion angle control section 300 may be configured without the steering angle disturbance compensation section 360 and addition section 363 and the reduction ratio section 370 .

(Embodiment 2)
16 is a diagram illustrating an example of an internal block configuration of a control unit according to the second embodiment; FIG. In addition, the same code|symbol is attached|subjected to the same structure part as the structure demonstrated in Embodiment 1 mentioned above, and the overlapping description is abbreviate|omitted. A control unit (ECU) 30a according to the second embodiment differs from that of the first embodiment in the configurations of a target steering torque generator 201 and a twist angle controller 300a.

In addition to the steering angle θh, the vehicle speed Vs, and the vehicle speed determination signal Vfail, the steering torque Ts and the motor angle θm are input to the target steering torque generator 201 .

The torsion angle control unit 300a calculates a motor current command value Imc that makes the torsion angle Δθ equal to the target torsion angle Δθref. Motor 20 is driven by motor current command value Imc.

FIG. 17 is a block diagram showing a configuration example of a target steering torque generator according to the second embodiment. As shown in FIG. 17, the target steering torque generator 201 of the second embodiment includes a SAT information corrector 250 and an adder 263 in addition to the configuration described in the first embodiment.

The steering angle θh, vehicle speed Vs, steering torque Ts, motor angle θm, and motor current command value Imc are input to the SAT information correction unit 250 . The SAT information correction unit 250 calculates a self-aligning torque (SAT) based on the steering torque Ts, the motor angle θm, and the motor current command value Imc, and further performs filtering, gain multiplication, and limiting processing to obtain a torque signal Tref_d. to calculate

FIG. 18 is a block diagram showing a configuration example of the SAT information corrector. The SAT information correction section 250 includes an SAT calculation section 251 , a filter section 252 , a steering torque sensitive gain section 253 , a vehicle speed sensitive gain section 254 , a steering angle sensitive gain section 255 and a limiting section 256 .

Here, the state of torque generated between the road surface and the steering will be described with reference to FIG. FIG. 19 is an image diagram showing how torque is generated from the road surface to the steering wheel.

Steering torque Ts is generated by the driver steering the steering wheel, and the motor 20 generates assist torque (motor torque) Tm according to the steering torque Ts. As a result, the wheels are steered and a self-aligning torque T _SAT is generated as a reaction force. At that time, the column shaft conversion inertia (inertia acting on the column shaft by (the rotor of) the motor 20, the speed reduction mechanism, etc.) J and friction (static friction) Fr generate a torque that acts as a resistance to steering. Furthermore, the rotational speed of the motor 20 produces a physical torque (viscous torque) expressed as a damper term (damper coefficient D _M ). From the balance of these forces, the equation of motion shown in Equation (12) below is obtained.

J× _αM +Fr×sign( _ωM )+ _DM × _ωM =Tm+Ts+ _TSAT (12)

In the above equation (12), ω _M is the motor angular velocity converted to the column axis (converted into a value with respect to the column axis), and α _M is the motor angular acceleration converted to the column axis. Then, when the above equation (12) is solved for T _SAT , the following equation (13) is obtained.

T _SAT =−Tm−Ts+J× _αM +Fr×sign( _ωM )+D _M × _ωM (13)

As can be seen from the above equation (13), the column axis conversion inertia J, the static friction Fr, and the damper coefficient DM are determined in advance as constants, so that the motor angular velocity ω _M , the motor angular acceleration α _M , the assist torque Tm, and the steering torque Ts The self-aligning torque T _SAT can be calculated from the above. Note that the column axis conversion inertia J may be a value converted to the column axis using a simple relational expression between the motor inertia and the speed reduction ratio.

The steering torque Ts, the motor angle θm, and the motor current command value Imc are input to the SAT calculator 251 . The SAT calculator 251 calculates the self-aligning torque T _SAT using the above equation (13). The SAT calculator 251 includes a converter 251A, an angular velocity calculator 251B, an angular acceleration calculator 251C, a block 251D, a block 251E, a block 251F, a block 251G, and adders 251H, 251I, and 251J.

Motor current command value Imc is input to conversion unit 251A. Conversion unit 251A calculates column-axis converted assist torque Tm by multiplying a predetermined gear ratio and a torque constant.

The motor angle θm is input to the angular velocity calculator 251B. The angular velocity calculator 251B calculates the column-axis-converted motor angular velocity ω _M by differential processing and multiplication by the gear ratio.

The motor angular velocity ω _M is input to the angular acceleration calculator 251C. The angular acceleration calculator 251C differentiates the motor angular velocity ω _M to calculate a column-axis-converted motor angular acceleration α _M .

Then, using the input steering torque Ts and the calculated assist torque Tm, motor angular velocity _ωM , and motor angular acceleration _αM , block 251D, block 251E, block 251F, block 251G, adders 251H, 251I, and By 251J, the self-aligning torque T _SAT is calculated based on Equation 8 with the configuration shown in FIG.

The block 251D receives the motor angular velocity ω _M output from the angular velocity calculator 251B. Block 251D functions as a sign function and outputs the sign of the input data.

The block 251E receives the motor angular velocity ω _M output from the angular velocity calculator 251B. Block 251E multiplies the input data by the damper coefficient D _M and outputs the result.

Block 251F multiplies the input data from block 251D by static friction Fr and outputs the result.

The block 251G receives the motor angular acceleration _αM output from the angular acceleration calculator 251C. A block 251G multiplies the input data by the column axis equivalent inertia J and outputs the result.

The adder 251H adds the steering torque Ts and the assist torque Tm output from the conversion section 251A.

Adder 251I subtracts the output of block 251G from the output of adder 251H.

Adder 251J adds the output of block 251E and the output of block 251F and subtracts the output of adder 251I.

With the above configuration, the above equation (13) can be realized. That is, the configuration of the SAT calculation section 251 shown in FIG. 18 calculates the self-aligning torque T _SAT .

If the column angle can be directly detected, the column angle may be used as angle information instead of the motor angle .theta.m. In this case, column axis conversion becomes unnecessary. Instead of the motor angle .theta.m, a signal obtained by converting the motor angular velocity .omega.m from the EPS steering system/vehicle system 100 into the column axis may be input as the motor angular velocity _.omega.M , and the differentiation process for the motor angle .theta.m may be omitted. Furthermore, the self-aligning torque T _SAT may be calculated by a method other than the above, and a measured value may be used instead of the calculated value.

In order to utilize the self-aligning torque T _SAT calculated by the SAT calculation unit 251 and appropriately convey the feeling of steering to the driver, the filter unit 252 extracts information to be conveyed from the self-aligning torque T _SAT and calculates the steering feeling. A torque sensitive gain section 253, a vehicle speed sensitive gain section 254, and a steering angle sensitive gain section 255 adjust the amount to be transmitted, and a limiting section 256 adjusts upper and lower limits. Note that in the present disclosure, the self-aligning torque T _SAT calculated by the SAT calculator 251 is also output to the target steering torque generator 201 .

The filter unit 252 receives the self-aligning torque T _SAT from the SAT calculation unit 251 . The filter unit 252 filters the self-aligning torque T _SAT using, for example, a bandpass filter, and outputs SAT information T _ST 1.

The SAT information T _ST 1 output from the filter unit 252 and the steering torque Ts are input to the steering torque sensitive gain unit 253 . A steering torque sensing gain unit 253 sets a steering torque sensing gain.

FIG. 20 is a diagram showing a characteristic example of the steering torque sensitive gain. As shown in FIG. 20, the steering torque responsive gain section 253 sets the steering torque responsive gain so that the sensitivity is high near the on-center, which is the straight running state. A steering torque sensing gain section 253 multiplies the SAT information T _ST 1 by a steering torque sensing gain set according to the steering torque Ts, and outputs SAT information T _ST 2 .

In FIG. 20, the steering torque sensing gain is fixed at 1.0 when the steering torque Ts is Ts1 (for example, 2 Nm) or less, and is a value smaller than 1.0 when the steering torque Ts is Ts2 (>Ts1) (for example, 4 Nm) or more. An example is shown in which the steering torque Ts is fixed and is set to decrease at a constant rate between Ts1 and Ts2.

The vehicle speed sensitive gain section 254 receives the SAT information T _ST 2 output from the steering torque sensitive gain section 253 and the vehicle speed Vs. A vehicle speed sensitive gain unit 254 sets a vehicle speed sensitive gain.

FIG. 21 is a diagram showing a characteristic example of the vehicle speed sensitive gain. As shown in FIG. 21, the vehicle speed sensitive gain unit 254 sets the vehicle speed sensitive gain so that the sensitivity during high speed running is high. Vehicle speed sensitive gain section 254 multiplies SAT information T _ST 2 by a vehicle speed sensitive gain set according to vehicle speed Vs, and outputs SAT information T _ST 3 .

In FIG. 21, the vehicle speed sensitive gain is fixed at 1.0 when the vehicle speed Vs is Vs2 (eg, 70 km/h) or higher, and is less than 1.0 when the vehicle speed Vs is Vs1 (<Vs2) (eg, 50 km/h) or lower. , and the vehicle speed Vs is set to increase at a constant rate between Vs1 and Vs2.

The SAT information T _ST 3 and the steering angle θh output from the vehicle speed sensitive gain section 254 are input to the steering angle sensitive gain section 255 . A steering angle sensitive gain section 255 sets a steering angle sensitive gain.

FIG. 22 is a diagram showing a characteristic example of the steering angle sensitive gain. As shown in FIG. 22, the steering angle sensitive gain section 255 sets the steering angle sensitive gain so that it starts acting at a predetermined steering angle and the sensitivity increases when the steering angle is large. A steering angle sensitive gain section 255 multiplies the SAT information T _ST 3 by a steering angle sensitive gain set according to the steering angle θh, and outputs a torque signal Tref_d0.

In FIG. 22, the steering angle responsive gain is a predetermined gain value Gα when the steering angle θh is θh1 (for example, 10 degrees) or less, and is fixed at 1.0 when the steering angle θh is θh2 (for example, 30 degrees) or more. An example is shown in which θh1 and θh2 are set to increase at a constant rate. To increase the sensitivity when the steering angle .theta.h is large, G.alpha. should be set in the range of 0.ltoreq.G.alpha.<1. If it is desired to increase the sensitivity when the steering angle θh is small, Gα may be set in the range of 1<Gα (not shown). If it is desired not to change the sensitivity due to the steering angle θh, Gα=1 may be set.

The torque signal Tref_d0 output from the steering angle sensitive gain section 255 is input to the limiting section 256 . The limiter 256 is set with an upper limit value and a lower limit value of the torque signal Tref_d0.

FIG. 23 is a diagram showing a setting example of the upper limit value and the lower limit value of the torque signal in the limiting section. As shown in FIG. 23, the limiting unit 256 is preset with an upper limit value and a lower limit value for the torque signal Tref_d0. The lower limit value is output as the torque signal Tref_d, otherwise the torque signal Tref_d0 is output.

Note that the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may have curvilinear characteristics instead of linear characteristics as shown in FIGS. Further, the settings of the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be appropriately adjusted according to the steering feeling. Also, if there is no possibility that the magnitude of the torque signal will increase or if it is suppressed by other means, the limiter 256 may be omitted. The steering torque sensitive gain section 253, the vehicle speed sensitive gain section 254, and the steering angle sensitive gain section 255 can also be omitted as appropriate. Also, the installation positions of the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be exchanged. Further, for example, the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be obtained in parallel, and the SAT information T _ST 1 may be multiplied by one component.

That is, the configuration of the SAT information correction unit 250 in this embodiment is an example, and may be different from the configuration shown in FIG.

Also in the present embodiment, the steering reaction force correction section 280 described in the first embodiment is provided in the target steering torque generation section 201, so that the same effect as in the first embodiment can be obtained.

Specifically, torque signal Tref_a (first torque signal), torque signal Tref_b, torque signal Tref_c, and torque signal Tref_d are added in adders 261, 262, and 263 to obtain torque signal Tref_e (second torque signal). be done.

Further, the multiplication unit 264 multiplies the torque signal Tref_e (second torque signal) output from the addition unit 261 by the correction gain G output from the steering reaction force correction unit 280 to obtain the torque signal Tref_f (third torque signal). signal) to the addition unit 265 . Addition unit 265 adds correction torque signal Tref_p (fourth torque signal) output from steering reaction force correction unit 280 to torque signal Tref_f (third torque signal) output from multiplication unit 264 to obtain a target Output as steering torque Tref.

In the drive mode (first mode), as in the first embodiment, the torque signal Tref_e (second torque signal) is multiplied by a correction gain G=1 to obtain a correction torque signal Tref_p (fourth torque signal)=0. to add. As a result, target steering torque Tref=torque signal Tref_e (second torque signal), and target steering torque Tref suitable for the drive mode (first mode) can be obtained.

In the low-speed operation mode (second mode), as in the first embodiment, the torque signal Tref_e (second torque signal) is multiplied by a positive correction gain G less than 1 (for example, G=0.3) to obtain torque. A signal Tref_f (third torque signal) is generated, and the slope at the absolute value |θh|=0 of the steering angle θh is greater than the torque signal Tref_a (first torque signal) with respect to the torque signal Tref_f (third torque signal). is added to generate the target steering torque Tref. As a result, as in the first embodiment, the target steering torque Tref can be made smaller than in the drive mode (first mode), and the operation of the steering wheel 1 can be lightened. Further, as in the first embodiment, in the region where the steering angle θh is around 0 (the region indicated by the dashed line in FIG. 14), the change in the steering force can be increased with respect to the change in the steering angle θh. It becomes easy to recognize the steering angle of zero. As a result, the burden on the driver can be reduced, and the steering feeling can be improved.

The twist angle control section 300a of the second embodiment will be described below with reference to FIG.

24 is a block diagram illustrating a configuration example of a twist angle control unit according to the second embodiment; FIG. The torsion angle control section 300a calculates a motor current command value Imc based on the target torsion angle Δθref, the torsion angle Δθ, and the motor angular velocity ωm. The torsion angle control unit 300a includes a torsion angle feedback (FB) compensation unit 310, a torsion angular velocity calculation unit 320, a speed control unit 330, a stabilization compensation unit 340, an output limiter 350, a subtraction unit 361, and an addition unit 362. .

The target twist angle Δθref output from the conversion unit 500 is added to the subtraction unit 361 . The twist angle Δθ is subtracted and input to the subtractor 361 and also input to the torsional angular velocity calculator 320 . The motor angular velocity ωm is input to stabilization compensator 340 .

The torsion angle FB compensator 310 multiplies the deviation Δθ0 between the target torsion angle Δθref and the torsion angle Δθ calculated by the subtraction unit 361 by a compensation value CFB (transfer function) so that the torsion angle Δθ follows the target torsion angle Δθref. A target torsional angular velocity ωref is output. The compensation value CFB may be a simple gain Kpp or a generally used compensation value such as a PI control compensation value.

The target torsional angular velocity ωref is input to velocity control section 330 . The torsion angle FB compensating section 310 and the speed control section 330 allow the torsion angle Δθ to follow the target torsion angle Δθref, thereby realizing a desired steering torque.

The torsion angular velocity calculation unit 320 performs differential operation processing on the torsion angle Δθ to calculate a torsion angular velocity ωt. The torsional angular velocity ωt is output to velocity control section 330 . The torsional angular velocity calculator 320 may perform pseudo-differentiation using the HPF and the gain as the differential calculation. Further, the torsion angular velocity calculator 320 may calculate the torsion angular velocity ωt using another means or other than the torsion angle Δθ, and output it to the velocity controller 330 .

Speed control unit 330 calculates a motor current command value Imca1 such that torsional angular velocity ωt follows target torsional angular velocity ωref by IP control (proportional leading PI control).

The subtractor 333 calculates the difference (ωref-ωt) between the target twist angular velocity ωref and the twist angular velocity ωt. The integrator 331 integrates the difference (ωref−ωt) between the target torsional angular velocity ωref and the torsional angular velocity ωt, and adds the integration result to the subtractor 334 .

The torsional angular velocity ωt is also output to the proportional section 332 . The proportional section 332 performs proportional processing with the gain Kvp on the torsional angular velocity ωt, and subtracts and inputs the proportional processing result to the subtraction section 334 . The subtraction result of the subtraction unit 334 is output as the motor current command value Imca1. Note that the speed control unit 330 performs PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model reference control, instead of IP control. The motor current command value Imca1 may be calculated by a commonly used control method such as control.

Stabilization compensator 340 has compensation value Cs (transfer function), and calculates motor current command value Imca2 from motor angular velocity ωm. If the gains of the torsion angle FB compensator 310 and the speed controller 330 are increased in order to improve the followability and disturbance characteristics, a controllable high-frequency oscillation phenomenon occurs. As a countermeasure, a transfer function (Cs) necessary for stabilizing the motor angular velocity ωm is set in the stabilization compensator 340 . This makes it possible to stabilize the entire EPS control system.

Addition unit 362 adds motor current command value Imca1 from speed control unit 330 and motor current command value Imca2 from stabilization compensation unit 340, and outputs the result as motor current command value Imcb.

The output limiter 350 is preset with an upper limit value and a lower limit value for the motor current command value Imcb. Output limiter 350 limits the upper and lower limits of motor current command value Imcb and outputs motor current command value Imc.

Note that the configuration of the torsion angle control section 300a in the present embodiment is an example, and a configuration different from the configuration shown in FIG. 24 may be used. For example, the torsion angle control section 300a may be configured without the stabilization compensation section 340. FIG.

(Embodiment 3)
In Embodiments 1 and 2, the present disclosure is applied to a column type EPS as one of vehicle steering devices, but the present disclosure is not limited to upstream types such as column types, and downstream types such as rack and pinions. It is also applicable to EPS. Furthermore, in terms of performing feedback control based on the target torsion angle, it is also applicable to a steer-by-wire (SBW) reaction force device or the like that includes at least a torsion bar (arbitrary spring constant) and a torsion angle detection sensor. An embodiment (embodiment 3) in which the present disclosure is applied to an SBW reaction force device having a torsion bar will be described.

First, the entire SBW system including the SBW reaction force device will be described. FIG. 25 is a diagram showing a configuration example of the SBW system in correspondence with the general configuration of the electric power steering apparatus shown in FIG. In addition, the same code|symbol is attached|subjected to the same structure as the structure demonstrated by Embodiment 1, 2 mentioned above, and detailed description is abbreviate|omitted.

The SBW system does not have an intermediate shaft that is mechanically coupled to the column shaft 2 at the universal joint 4a shown in FIG. System. As shown in FIG. 25, the SBW system includes a reaction device 60 and a drive device 70, and a control unit (ECU) 50 controls both devices. The reaction force device 60 detects the steering angle θh with the steering angle sensor 14, and at the same time, transmits the motion state of the vehicle transmitted from the steered wheels 8L, 8R to the driver as reaction torque. The reaction torque is generated by the reaction force motor 61 . In addition, in the present disclosure, the steering torque Ts is detected by the torque sensor 10, but it is not limited to this. Also, the angle sensor 74 detects the motor angle θm of the reaction force motor 61 . The driving device 70 drives a driving motor 71 in accordance with the steering of the steering wheel 1 by the driver, applies the driving force to the pinion rack mechanism 5 via the gear 72, and passes through the tie rods 6a and 6b to drive the driving motor 71. The direction wheels 8L and 8R are steered. An angle sensor 73 is arranged near the pinion rack mechanism 5 to detect the turning angle θt of the steered wheels 8L, 8R. In order to cooperatively control the reaction force device 60 and the driving device 70, the ECU 50 controls the vehicle speed Vs and the like from the vehicle speed sensor 12 in addition to information such as the steering angle θh and the turning angle θt output from both devices. A voltage control command value Vref1 for driving and controlling the reaction force motor 61 and a voltage control command value Vref2 for driving and controlling the driving motor 71 are generated.

A configuration of a third embodiment in which the present disclosure is applied to such an SBW system will be described.

FIG. 26 is a block diagram showing the configuration of the third embodiment. Embodiment 3 performs control over the torsion angle Δθ (hereinafter referred to as “torsion angle control”) and control over the steering angle θt (hereinafter referred to as “turning angle control”). control, and the driving device is controlled by steering angle control. Note that the driving device may be controlled by other control methods.

In the torsion angle control, the torsion angle Δθ follows the target torsion angle Δθref calculated through the target steering torque generation unit 202 and the conversion unit 500 using the steering angle θh and the like by using the same configuration and operation as in the second embodiment. such control. The motor angle θm is detected by the angle sensor 74 , and the motor angular velocity ωm is calculated by differentiating the motor angle θm by the angular velocity calculator 951 . A steering angle θt is detected by an angle sensor 73 . Further, in the first embodiment, detailed description is not given as processing in the EPS steering system/vehicle system 100, but the current control unit 130 includes the subtraction unit 32B, the PI control unit 35, and the PWM control unit shown in FIG. 36 and the inverter circuit 37, based on the motor current command value Imc output from the torsion angle control unit 300a and the current value Imr of the reaction force motor 61 detected by the motor current detector 140, Current control is performed by driving the reaction force motor 61 .

In the steering angle control, the target steering angle θtref is generated based on the steering angle θh in the target steering angle generation section 910, and the target steering angle θtref is input to the steering angle control section 920 together with the steering angle θt. , the steering angle control unit 920 calculates a motor current command value Imct that causes the steering angle θt to become the target steering angle θtref. Then, based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940, the current control unit 930 controls the drive motor 71 with the same configuration and operation as the current control unit 130. 71 is driven to perform current control. In the present disclosure, the motor current command value Imct calculated by steering angle control section 920 is also output to target steering torque generation section 202 .

FIG. 27 is a diagram illustrating a configuration example of a target steering angle generation unit. The target steering angle generator 910 includes a limiter 931 , a rate limiter 932 and a corrector 933 .

A limiting unit 931 limits the upper and lower limits of the steering angle θh and outputs the steering angle θh1. Similar to the output limiter 350 in the torsion angle control unit 300a shown in FIG. 24, the upper limit and lower limit of the steering angle θh are preset and limited.

A rate limiter 932 limits the amount of change in the steering angle θh1 by setting a limit value to avoid a sudden change in the steering angle, and outputs a steering angle θh2. For example, if the amount of change is the difference from the steering angle θh1 one sample before, and the absolute value of the amount of change is greater than a predetermined value (limit value), the steering angle The steering angle .theta.h2 is output by adding or subtracting .theta.h1. If the steering angle .theta.h2 is equal to or less than the limit value, the steering angle .theta.h1 is directly output as the steering angle .theta.h2. Instead of setting a limit value for the absolute value of the amount of change, an upper limit value and a lower limit value may be set for the amount of change to limit the amount of change. You may make it restrict|limit with respect to a rate.

A correction unit 933 corrects the steering angle θh2 and outputs a target steering angle θtref. For example, using a map that defines the characteristics of the target steering angle θtref with respect to the steering angle θh2 magnitude |θh2|, the target steering angle θtref is obtained from the steering angle θh2. Alternatively, the target steering angle θtref may be obtained simply by multiplying the steering angle θh2 by a predetermined gain.

FIG. 28 is a diagram showing a configuration example of a turning angle control section. The steering angle control section 920 has the same configuration as the configuration example of the torsion angle control section 300a shown in FIG. A steering angle feedback (FB) compensator 921, a steering angular velocity calculator 922, a speed controller 923, an output limiter 926, and a subtractor 927 input a target steering angle θtref and a steering angle θt instead of the angle Δθ. have the same configurations as the torsion angle FB compensator 310, the torsion angular velocity calculator 320, the velocity controller 330, the output limiter 350, and the subtractor 361, and perform the same operations.

In such a configuration, an operation example of the third embodiment will be described with reference to the flowchart of FIG. FIG. 29 is a flowchart illustrating an operation example of the third embodiment;

When the operation starts, the angle sensor 73 detects the steering angle θt, the angle sensor 74 detects the motor angle θm (step S110), the steering angle θt is sent to the steering angle control unit 920, and the motor angle θm is the angular velocity. They are input to the calculation unit 951 respectively.

The angular velocity calculator 951 differentiates the motor angle θm to calculate the motor angular velocity ωm, and outputs it to the twist angle controller 300a (step S120).

Thereafter, the target steering torque generator 202 performs the same operations as steps S10 to S40 shown in FIG. 7 to drive the reaction force motor 61 and perform current control (steps S130 to S160).

On the other hand, in steering angle control, the target steering angle generator 910 inputs the steering angle θh, and the steering angle θh is input to the limiter 931 . The limiting unit 931 limits the upper and lower limits of the steering angle θh with preset upper and lower limits (step S170), and outputs the steering angle θh1 to the rate limiting unit 932 . The rate limiter 932 limits the amount of change in the steering angle θh1 with a preset limit value (step S180), and outputs it to the correction unit 933 as the steering angle θh2. The correction unit 933 corrects the steering angle θh2 to obtain the target turning angle θtref (step S190), and outputs the target turning angle θtref to the turning angle control unit 920 .

The turning angle control unit 920, which receives the turning angle θt and the target turning angle θtref, calculates the deviation Δθt0 by subtracting the turning angle θt from the target turning angle θtref in the subtraction unit 927 (step S200). ). The deviation Δθt0 is input to the turning angle FB compensator 921, and the turning angle FB compensator 921 compensates for the deviation Δθt0 by multiplying the deviation Δθt0 by a compensation value (step S210), and converts the target turning angular velocity ωtref into the speed. Output to the control unit 923 . The steering angular velocity calculator 922 receives the steering angle θt, calculates the steering angular velocity ωtt by differential calculation with respect to the steering angle θt (step S 220 ), and outputs it to the speed controller 923 . Speed control unit 923 calculates motor current command value Imcta by IP control in the same manner as speed control unit 330 (step S 230 ), and outputs it to output limiting unit 926 . The output limiter 926 limits the upper and lower limits of the motor current command value Imcta by preset upper and lower limits (step S240), and outputs the motor current command value Imct (step S250).

The motor current command value Imct is input to the current control unit 930 , and the current control unit 930 controls the drive motor 71 based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940 . 71 is driven to perform current control (step S260).

Note that the order of data input and calculation in FIG. 29 can be changed as appropriate. Further, like the speed control unit 330 in the torsion angle control unit 300a, the speed control unit 923 in the steering angle control unit 920 does not perform IP control, but PI control, P control, PID control, PI control, P control, and PI control. It is possible to implement control such as control, and any one of P, I and D control may be used.Furthermore, follow-up control by the steering angle control unit 920 and the twist angle control unit 300a is generally used. It may be done with a control structure that has The turning angle control unit 920 is used in a vehicle device if it has a control configuration in which the actual angle (here, the turning angle θt) follows the target angle (here, the target turning angle θtref). The control configuration is not limited, and for example, a control configuration used in industrial positioning devices, industrial robots, etc. may be applied.

In the third embodiment, as shown in FIG. 25, one ECU 50 controls the reaction device 60 and the driving device 70. However, an ECU for the reaction device 60 and an ECU for the driving device 70 are provided. can be In this case, the ECUs transmit and receive data through communication. The SBW system shown in FIG. 25 does not have a mechanical connection between the reaction force device 60 and the drive device 70. However, when an abnormality occurs in the system, the column shaft 2 and the steering mechanism are connected by a clutch or the like. The present disclosure is also applicable to SBW systems that include a mechanical torque transmission mechanism that mechanically couples at . In such an SBW system, when the system is normal, the clutch is turned off to disengage mechanical torque transmission, and when the system is abnormal, the clutch is turned on to enable mechanical torque transmission.

The torsion angle control units 300 and 300a in Embodiments 1 to 3 described above directly calculate the motor current command value Imc and the assist current command value Iac. The motor current command value and the assist current command value may be calculated after calculating the torque (target torque). In this case, in order to obtain the motor current command value and the assist current command value from the motor torque, the generally used relationship between the motor current and the motor torque is used.

Also in the present embodiment, the steering reaction force correction section 280 described in the first embodiment is provided in the target steering torque generation section 202, so that the same effect as in the first embodiment can be obtained.

Note that the diagrams used above are conceptual diagrams for qualitatively explaining the present disclosure, and are not limited to these. In addition, although the above-described embodiment is an example of the preferred implementation of the present disclosure, it is not limited to this, and various modifications can be implemented without departing from the gist of the present disclosure. Also, any mechanism having an arbitrary spring constant between the handle and the motor or reaction motor may be used without being limited to the torsion bar.

1 steering wheel 2 column shaft 2A torsion bar 3 reduction mechanism 4a, 4b universal joint 5 pinion rack mechanism 6a, 6b tie rod 7a, 7b hub unit 8L, 8R steering wheel 10 torque sensor 11 ignition key 12 vehicle speed sensor 13 battery 14 steering angle sensor 15 low-speed operation mode detection unit (judgment unit)
20 motor 30, 30a, 50 control unit (ECU)
60 reaction force device 61 reaction force motor 70 drive device 71 drive motor 72 gear 73 angle sensor 100 EPS steering system/vehicle system 130 current control unit 140 motor current detector 200, 201, 202 target steering torque generation unit 210 basic map Section 211 Multiplication Section 213 Sign Extraction Section 220 Differentiation Section 230 Damper Gain Map Section 240 Hysteresis Correction Section 250 SAT Information Correction Section 251 SAT Calculation Section 251A Conversion Section 251B Angular Velocity Calculation Section 251C Angular Acceleration Calculation Section 251D, 251E, 251F Blocks 251H, 251I , 251J adder 252 filter unit 253 steering torque sensitive gain unit 254 vehicle speed sensitive gain unit 255 steering angle sensitive gain unit 256 limiting unit 260, 264 multiplication unit 261, 262, 265 addition unit 280 steering reaction force correction unit 281 correction gain generation unit 282 correction torque map 283 sign extraction unit 284 multiplication unit 300, 300a torsion angle control unit 310 torsion angle feedback (FB) compensation unit 320 torsion angular velocity calculation unit 330 speed control unit 331 integration unit 332 proportional unit 333, 334 subtraction unit 340 stabilization Compensating unit 350 Output limiting unit 360 Steering angle disturbance compensating unit 361 Subtracting unit 362, 363 Adding unit 370 Reduction ratio unit 400 Steering direction determining unit 500 Converting unit 910 Target turning angle generating unit 920 Turning angle control unit 921 Turning angle feedback (FB) Compensator 922 Steering angular velocity calculator 923 Speed controller 926 Output limiter 927 Subtracter 930 Current controller 931 Limiter 933 Corrector 932 Rate limiter 940 Motor current detector 1001 CPU
1005 interface 1006 A/D converter 1007 PWM controller 1100 control computer (MCU)

Claims (5)

A vehicle steering apparatus that assists and controls a steering system of a vehicle by driving and controlling a motor that assists steering force,
As the driving mode of the vehicle,
low speed mode and
a drive mode when the low-speed operation mode is not selected;
has
In a predetermined region where the absolute value of the steering angle of the steering wheel is zero or more, the change rate of the target steering torque of the motor in the low-speed operation mode is equal to or higher than the drive mode , and in regions other than the predetermined region, the low-speed operation mode . the rate of change of the target steering torque in the drive mode is smaller than that in the drive mode. a determination unit that determines the low-speed operation mode when a predetermined operation is detected;
A first torque signal is generated that increases along a curve whose rate of change gradually decreases as the absolute value of the steering angle of the steering wheel increases, and a correction gain is applied to the second torque signal generated based on the first torque signal. a target steering torque generation unit that multiplies to generate a third torque signal, adds a fourth torque signal to the third torque signal, and generates the target steering torque;
with
The target steering torque generation unit
Generating the positive correction gain of less than 1 and generating the fourth torque signal having a greater slope than the first torque signal when the absolute value of the steering angle is zero in the low-speed operation mode. 2. The vehicle steering system according to 1. 3. The vehicle steering system according to claim 2, wherein the fourth torque signal in the low speed operation mode has a constant value in a region where the steering angle is equal to or greater than a predetermined value. The target steering torque generation unit
4. The vehicle steering system according to claim 2, wherein in the drive mode , the correction gain is set to 1 and the fourth torque signal is set to zero. The vehicle steering system according to any one of claims 1 to 4, wherein the target steering torque in the low speed operation mode is smaller than the target steering torque in the drive mode .

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