JP2016159701A - Electric power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of alleviating mishandling of a steering wheel on a road of a low coefficient of friction μ and ensuring a sufficient assist force on a road of a high coefficient of friction μ even when a failure occurs in torque detection means.SOLUTION: An electric power steering system includes: an electric motor that applies an assist force to handling of a steering wheel of a vehicle; a torque sensor that detects a steering torque of the steering wheel; steering angle detection means that detects a steering angle which is a rotation angle of the steering wheel; a sensor failure detector 27 that detects a failure of the torque sensor; and a sensor failure-time current determiner 28 that, when the sensor failure detector 27 detects a failure, determines a basic assist force, which serves as a base of the assist force, on the basis of the steering angle detected by the steering angle detection means, and controls the electric motor so that the electric motor can provide the assist force whose basic assist force has been corrected according to the acceleration of the steering angle.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electric power steering apparatus.

In recent years, in an electric power steering apparatus that assists a driver's steering force with the power of an electric motor, even when the detection means (torque sensor) that detects the steering torque cannot detect the steering torque, A technique that makes it possible to apply assist force has been proposed.
For example, the electric power steering device described in Patent Document 1 drives the motor based on the rotation angle detected by the resolver and the assist current characteristics when the abnormality of the torque sensor is detected by the abnormality detection unit. In this case, control is performed so that the assist current for driving the motor decreases as the rotation angular velocity calculated based on the rotation angle increases.

JP 2012-144100 A

Even when a failure occurs in the torque detection means (torque sensor), it is desirable to be able to reduce steering on low μ roads and to secure a sufficient assist force on high μ roads such as asphalt roads.
It is an object of the present invention to provide an electric power steering apparatus that can reduce steering on a low μ road and secure a sufficient assist force on a high μ road even when a failure occurs in the torque detection means. And

  For this purpose, the present invention relates to an electric motor for applying an assisting force to steering of a steering wheel of a vehicle, torque detecting means for detecting a steering torque of the steering wheel, and a rotation angle of the steering wheel. A steering angle estimating means for estimating a steering angle; a failure detecting means for detecting a failure of the torque detecting means; and when the failure detecting means detects a failure, based on the steering angle estimated by the steering angle estimating means. Control means for determining a basic auxiliary force that is a basis of the auxiliary force, and controlling the electric motor so as to be the auxiliary force obtained by correcting the basic auxiliary force according to the acceleration of the steering angle. An electric power steering device characterized by the above.

Here, the control means may correct the basic auxiliary force so that the auxiliary force becomes smaller when the acceleration of the steering angle is larger than a predetermined steering angular acceleration.
Further, the control means may correct the basic auxiliary force so that the auxiliary force becomes smaller when a vehicle speed, which is a moving speed of the vehicle, is higher than a predetermined vehicle speed.
The control means may determine the auxiliary force based on the steering torque detected by the torque detection means when the failure detection means has not detected a failure.

  According to the present invention, even when a failure occurs in the torque detecting means, steering on a low μ road can be reduced and a sufficient assist force on a high μ road can be secured.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of a control apparatus. It is a schematic block diagram of a target current calculation part. It is the schematic of the control map which shows a response | compatibility with steering torque, vehicle speed, and base current. It is a schematic block diagram of a control part. It is a schematic block diagram of the current determination part at the time of a sensor failure. It is a schematic block diagram of the base current calculation part at the time of a sensor failure. It is the schematic of the control map which shows a response | compatibility with the steering angle after absolute value conversion, and the base current at the time of temporary sensor failure. It is the schematic of the control map which shows a response | compatibility with a vehicle speed correction coefficient and a vehicle speed. It is a schematic block diagram of a return correction coefficient setting part. It is the schematic of the control map which shows a response | compatibility with the steering angle after absolute value conversion, and a temporary return correction coefficient. It is the schematic of the control map which shows a response | compatibility with a motor rotational speed and a rotational speed correction coefficient. It is the schematic of the control map which shows a response | compatibility with a vehicle speed and a vehicle speed correction coefficient. It is a schematic block diagram of a steering angular acceleration correction coefficient setting part. It is the schematic of the control map which shows a response | compatibility with the steering angular acceleration after absolute value conversion, and a temporary steering angular acceleration correction coefficient. It is the schematic of the control map which shows a response | compatibility with a vehicle speed correction coefficient and a vehicle speed.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
Electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle, and in this embodiment, an automobile as an example of the vehicle. 1 illustrates the configuration applied to 1.

  The steering device 100 includes a wheel-like steering wheel 101 that is operated by a driver to change the traveling direction of the automobile 1, and a steering shaft 102 that is provided integrally with the steering wheel 101. Yes. The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via the torsion bar 112 in the steering gear box 107. The steering gear box 107 has a steering torque T applied to the steering wheel 101 based on the relative rotation angle between the lower connecting shaft 108 and the pinion shaft 106, in other words, based on the twist amount of the torsion bar 112. A torque sensor 109 is provided as an example of torque detecting means for detecting the torque.

  Further, the steering device 100 includes an electric motor 110 supported by the steering gear box 107 and a speed reduction mechanism 111 that reduces the driving force of the electric motor 110 and transmits it to the pinion shaft 106. The speed reduction mechanism 111 includes, for example, a worm wheel (not shown) fixed to the pinion shaft 106, a worm gear (not shown) fixed to the output shaft of the electric motor 110, and the like. The electric motor 110 applies a driving force for rolling the front wheel 150 to the rack shaft 105 by applying a rotational driving force to the pinion shaft 106. The electric motor 110 according to the present embodiment is a three-phase brushless motor having a resolver 120 that detects the rotation angle of the electric motor 110.

  In addition, the steering device 100 includes a control device 10 that controls the operation of the electric motor 110. An output signal from the torque sensor 109 described above is input to the control device 10. In addition, the control device 10 includes a vehicle speed sensor that detects a vehicle speed Vc that is a moving speed of the automobile 1 via a network (CAN) that performs communication for sending signals for controlling various devices mounted on the automobile 1. An output signal from 170 or the like is input.

  The steering device 100 configured as described above drives the electric motor 110 based on the detected torque detected by the torque sensor 109 and transmits the generated torque of the electric motor 110 to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic logic operation circuit including a CPU, a ROM, a RAM, an EEPROM (Electrically Erasable & Programmable Read Only Memory), and the like.
The control device 10 includes a torque signal Td obtained by converting the steering torque T detected by the torque sensor 109 described above into an output signal, and a vehicle speed signal obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal. v, a rotation angle signal θs that is an output signal corresponding to the rotation angle θ of the electric motor 110 from the resolver 120, and the like are input.

  Then, the control device 10 calculates (sets) a target current It necessary for the electric motor 110 to supply based on the torque signal Td, the vehicle speed signal v, and the like, and a target current calculation unit 20. And a control unit 30 that performs feedback control or the like based on the target current It calculated by. Further, the control device 10 calculates the motor rotation speed Vm based on the motor rotation angle calculation unit 71 that calculates the motor rotation angle of the electric motor 110 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. A motor rotation speed calculation unit 72 that performs the operation, and a steering angle calculation unit 73 that calculates a steering angle that is a rotation angle of the steering wheel 101.

Next, the target current calculation unit 20 will be described in detail.
FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 calculates a base current calculation unit 21 that calculates a base current Ib that serves as a reference for setting the target current It, and inertia compensation that calculates an inertia compensation current Is for canceling the inertia moment of the electric motor 110. A current calculation unit 22 and a damper compensation current calculation unit 23 that calculates a damper compensation current Id that limits the rotation of the electric motor 110 are provided. Further, the target current calculation unit 20 determines a temporary target current Itf that is a temporary target current based on the values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. A temporary target current determination unit 25 is provided. In addition, the target current calculation unit 20 includes a phase compensation unit 26 that compensates for the phase of the steering torque T detected by the torque sensor 109.

The target current calculation unit 20 also includes a sensor failure detection unit 27 as an example of a failure detection unit that detects a failure of the torque sensor 109, and the electric motor 110 when the sensor failure detection unit 27 detects a failure of the torque sensor 109. A sensor failure current determination unit 28 that calculates a current that is a base of the target current It to be supplied to. The target current calculation unit 20 includes a final target current determination unit 29 that determines a target current It that is finally supplied to the electric motor 110.
The target current calculation unit 20 receives a torque signal Td, a vehicle speed signal v, a motor rotation speed signal Vms, and the like.

FIG. 4 is a schematic diagram of a control map showing the correspondence between the steering torque T, the vehicle speed Vc, and the base current Ib.
The base current calculation unit 21 calculates a base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170. In other words, the base current calculation unit 21 calculates the base current Ib according to the steering torque T phase-compensated by the phase compensation unit 26 and the vehicle speed Vc. The base current calculation unit 21 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current that are created in advance based on empirical rules and stored in the ROM. The base current Ib is calculated by substituting the steering torque T and the vehicle speed Vc into the control map illustrated in FIG. 4 illustrating the correspondence with Ib.

  The inertia compensation current calculation unit 22 calculates the inertia compensation current Is based on the torque signal Ts and the vehicle speed signal v obtained by phase compensation of the torque signal Td by the phase compensation unit 26. In other words, the inertia compensation current calculation unit 22 calculates the inertia compensation current Is according to the steering torque T phase-compensated by the phase compensation unit 26 and the vehicle speed Vc. Note that the inertia compensation current calculation unit 22, for example, a phase-compensated steering torque T (torque signal Ts) and vehicle speed Vc (vehicle speed signal v) and inertia, which are created based on empirical rules and stored in the ROM in advance. The inertia compensation current Is is calculated by substituting the phase-compensated steering torque T and the vehicle speed Vc into the control map indicating the correspondence with the compensation current Is.

  The damper compensation current calculation unit 23 calculates the damper compensation current Id based on the torque signal Ts, the vehicle speed signal v, the motor rotation speed signal Vms, etc., in which the phase of the torque signal Td is compensated by the phase compensation unit 26. In other words, the damper compensation current calculation unit 23 calculates the damper compensation current Id according to the steering torque T phase-compensated by the phase compensation unit 26, the vehicle speed Vc, and the motor rotation speed Vm. The damper compensation current calculation unit 23 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and motor, which are previously created based on empirical rules and stored in the ROM. By substituting the phase-compensated steering torque T, vehicle speed Vc, and motor rotational speed Vm into a control map indicating the correspondence between the rotational speed Vm (motor rotational speed signal Vms) and the damper compensation current Id, the damper compensation current Id is obtained. calculate.

  The temporary target current determination unit 25 includes a base current Ib calculated by the base current calculation unit 21, an inertia compensation current Is calculated by the inertia compensation current calculation unit 22, and a damper calculated by the damper compensation current calculation unit 23. A temporary target current Itf is determined based on the compensation current Id. For example, the temporary target current determination unit 25 determines the current obtained by adding the inertia compensation current Is to the base current Ib and subtracting the damper compensation current Id as the temporary target current Itf.

The sensor failure detection unit 27 detects, for example, an abnormality such that the output from the torque sensor 109 is fixed to zero (V) or a voltage other than zero to 5 (V) is output. Is determined to have failed, and the failure is output to the sensor failure current determination unit 28 and the final target current determination unit 29.
The sensor failure current determination unit 28 will be described in detail later.

  The final target current determination unit 29 determines the temporary target determined by the temporary target current determination unit 25 when the sensor failure detection unit 27 does not determine that there is a failure (when a signal indicating failure has not been acquired). The current Itf is determined as the final target current It. On the other hand, when the sensor failure detection unit 27 determines that a failure has occurred (when a signal indicating failure has been acquired), the sensor failure current Ie determined by the sensor failure current determination unit 28 is used as the final target current. It is determined as It. That is, when the sensor failure detection unit 27 determines that there is a failure, the electric motor 110 generates an assist force (auxiliary force) corresponding to the sensor failure current Ie.

  Here, a state in which the torsion bar 112 has a zero twist amount is defined as a neutral state (neutral position), and the steering wheel 101 (lower connection shaft 108) and pinion shaft when the steering wheel 101 rotates clockwise from the neutral state (neutral position). The direction in which the relative rotation angle with respect to 106 changes (the direction in which the relative rotation angle occurs) is positive (the steering torque T is positive). On the other hand, the direction in which the relative rotation angle between the steering wheel 101 (lower connection shaft 108) and the pinion shaft 106 changes when the steering wheel 101 rotates counterclockwise from the neutral state (the direction in which the relative rotation angle occurs) is negative (steering). Torque T is negative). At this time, an output value from the torque sensor 109 when the relative rotation angle between the steering wheel 101 and the pinion shaft 106 is twisted in the clockwise direction from the neutral state (the torsion bar 112 is twisted in the clockwise direction). The sign of a certain torque signal Td is added, and the sign of the torque signal Td from the torque sensor 109 when the relative rotation angle is twisted counterclockwise from the neutral state (the torsion bar 112 is twisted counterclockwise). Negative.

  When the sign of the torque signal Td from the torque sensor 109 is positive, the base current calculation unit 21 calculates the base current Ib so as to rotate the electric motor 110 in one rotation direction, and the base current Ib The direction of flow is positive. That is, as shown in FIG. 4, when the sign of the torque signal Td from the torque sensor 109 is positive and the steering torque T is positive, the base current calculation unit 21 calculates a positive base current Ib, Torque is generated in the direction of rotation in the direction of rotation. On the other hand, when the sign of the torque signal Td from the torque sensor 109 is negative, the base current calculation unit 21 calculates a negative base current Ib, and generates torque in a direction that rotates the electric motor 110 in the other rotation direction.

Next, the control unit 30 will be described in detail.
FIG. 5 is a schematic configuration diagram of the control unit 30.
As shown in FIG. 5, the control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. And a motor current detection unit 33 for detection. Further, the control unit 30 has a feedback current calculation unit 38 that calculates the feedback current If based on the actual current Im detected by the motor current detection unit 33 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. doing.

  The motor drive control unit 31 performs feedback control based on a deviation between the target current It finally determined by the target current calculation unit 20 and the feedback current If calculated by the feedback current calculation unit 38 ( F / B) The control unit 40 and the PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110 are included.

  The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current It finally determined by the target current calculating unit 20 and the feedback current If calculated by the feedback current calculating unit 38, and the deviation is A feedback (F / B) processing unit 42 that performs feedback processing so as to be zero.

The feedback (F / B) processing unit 42 performs feedback control so that the target current It and the feedback current If match. For example, the feedback (F / B) processing unit 42 is proportional to the deviation calculated by the deviation calculating unit 41. Is proportionally processed, integrated by an integral element, and these values are added by an addition operation unit.
The PWM signal generation unit 60 generates a PWM signal for PWM (pulse width modulation) driving of the electric motor 110 based on the output value from the feedback control unit 40 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. Generate and output the generated PWM signal.

  The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.

The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32.
The feedback current calculation unit 38 is based on the arithmetic expression stored in advance in the ROM, the actual current Im detected by the motor current detection unit 33, and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. Is calculated.

The motor rotation angle calculation unit 71 (see FIG. 2) calculates the motor rotation angle θ based on the output signal of the resolver 120.
The motor rotation speed calculation unit 72 (see FIG. 2) calculates the motor rotation speed Vm of the electric motor 110 based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71, and the calculated motor rotation speed Vm is an output signal. The motor rotation speed signal Vms converted into is output.
The steering angle calculation unit 73 (see FIG. 2) is configured such that the rotation angle (steering angle) of the steering wheel 101 and the motor rotation angle θ of the electric motor 110 because the steering wheel 101, the speed reduction mechanism 111, and the like are mechanically coupled. The steering angle is calculated based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. For example, the steering angle calculation unit 73 performs steering based on the integrated value of the difference between the previous value and the current value of the motor rotation angle θ calculated periodically (for example, every 1 millisecond) by the motor rotation angle calculation unit 71. Calculate the corner.
The resolver 120, the motor rotation angle calculation unit 71, and the steering angle calculation unit 73 function as an example of a steering angle estimation unit that estimates the steering angle.

  Here, the sign of the steering angle when the steering wheel 101 is rotated clockwise from zero degree is plus, and the sign of the steering angle when the steering wheel 101 is rotated counterclockwise is minus. Further, the sign of the rotation direction of the electric motor 110 mechanically connected to the steering wheel 101 is added to the rotation direction of the electric motor 110 when the steering wheel 101 is rotated to the right (one rotation direction described above), The rotation direction of the electric motor 110 when the steering wheel 101 is rotated counterclockwise (the other rotation direction described above) is negative.

[Sensor failure current determination unit 28]
Next, the sensor failure current determination unit 28 will be described in detail.
FIG. 6 is a schematic configuration diagram of the sensor failure current determination unit 28.
The sensor failure current determination unit 28 calculates a substitution steering angle θse, which is a steering angle for substitution into a control map described later, based on the calculated steering angle θsc calculated by the steering angle calculation unit 73. A calculation unit 281; a sensor failure base current calculation unit 282 that calculates a sensor failure base current Ieb that is a base of the sensor failure current Ie based on the substitution steering angle θse calculated by the substitution steering angle calculation unit 281; It has. The generated torque of the electric motor 110 corresponding to the base current Ieb at the time of sensor failure is the basic auxiliary force (basic assist force) that is the basis of the auxiliary force (assist force) of the electric motor 110 when the sensor failure detection unit 27 determines that there is a failure. ). In other words, the sensor failure base current calculation unit 282 determines the basic auxiliary force that is the basis of the auxiliary force of the electric motor 110 when the sensor failure detection unit 27 determines that there is a failure.

  The sensor failure current determination unit 28 includes a return correction coefficient setting unit 283 that sets a return correction coefficient Kr for correcting the sensor failure current Ie so that the steering wheel 101 is turned back down. The return correction coefficient for calculating the return-corrected base current Iebr by multiplying the sensor-failure base current Ieb calculated by the sensor-failure base current calculation section 282 and the return correction coefficient setting section 283. A multiplication unit 284.

  In addition, the sensor failure current determination unit 28 includes a rotation speed correction coefficient setting unit 285 that sets a rotation speed correction coefficient Km according to the motor rotation speed Vm, and a return-corrected base calculated by the return correction coefficient multiplication unit 284. A rotation speed correction coefficient multiplying unit 286 that calculates a rotation speed corrected base current Iebv by multiplying the current Iebr by the rotation speed correction coefficient Km set by the rotation speed correction coefficient setting unit 285;

  In addition, the sensor failure current determination unit 28 includes a steering angular acceleration correction coefficient setting unit 287 that sets a steering angular acceleration correction coefficient Ks corresponding to the steering angular acceleration θa, and a rotation calculated by a rotation speed correction coefficient multiplication unit 286. A steering angular acceleration correction coefficient multiplication unit 288 that calculates a post-steering angular acceleration corrected base current Iebs by multiplying the post-speed correction base current Iebv and the steering angular acceleration correction coefficient Ks set by the steering angular acceleration correction coefficient setting unit 287; It is equipped with.

  Further, the sensor failure current determination unit 28 includes a limit processing unit 289 that performs a limit process on the steering angular acceleration corrected base current Iebs calculated by the steering angular acceleration correction coefficient multiplication unit 288, and a limit processing unit 289. And an encoding processing unit 290 that performs encoding processing on the post-limit processing base current Il that is the base current Iebs after steering angular acceleration correction after the limit processing.

  In addition, the sensor failure current determination unit 28 includes a fade processing unit 291 that applies a fade process to the post-limit processing base current Il that has been encoded by the encoding processing unit 290 based on the vehicle speed Vc. .

Next, elements constituting the sensor failure current determination unit 28 will be described in detail.
<Substituted steering angle calculation unit 281>
The substitution steering angle calculation unit 281 calculates the zero degree by integrating the difference between the previous value and the current value of the calculated steering angle θsc periodically (for example, every 1 millisecond) calculated by the steering angle calculation unit 73 from zero degree. The rotation angle from is calculated, and this calculated value is set as the substitution steering angle θse. When a predetermined reset condition is satisfied, the substitution steering angle θse is reset to zero. The reset condition may be any condition as long as the difference in rotation angle (steering angle) of the steering wheel 101 can be grasped to be zero. For example, the target current It or the motor current set by the target current calculation unit 20 can be used. A case where the actual current Im detected by the detection unit 33 becomes zero or near the zero value can be exemplified.

<Sensor Failure Base Current Calculation Unit 282>
FIG. 7 is a schematic configuration diagram of the sensor failure base current calculation unit 282.
The sensor failure base current calculation unit 282 is converted into an absolute value by the absolute value conversion unit 282a that converts the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 into an absolute value and an absolute value conversion unit 282a. A temporary base current calculation unit 282b that calculates a temporary sensor failure base current Ieba that is a temporary sensor failure base current Ieb based on the absolute steering angle | θse |. The sensor failure base current calculation unit 282 includes a vehicle speed correction coefficient setting unit 282c that sets the vehicle speed correction coefficient Kv based on the vehicle speed signal v, and a temporary sensor failure base current calculated by the temporary base current calculation unit 282b. A vehicle speed correction coefficient multiplication unit 282d that calculates the sensor failure base current Ieb by multiplying Ieba by the vehicle speed correction coefficient Kv set by the vehicle speed correction coefficient setting unit 282c. The sensor failure base current calculation unit 282 calculates the sensor failure base current Ieb periodically (for example, every 1 millisecond).

(Absolute part 282a)
The absolute value converting unit 282a calculates the absolute value of the steering angle θse for substitution having a plus or minus sign. The value calculated by the absolute value converting unit 282a is the steering angle | θse | after the absolute value conversion.

(Temporary base current calculation unit 282b)
FIG. 8 is a schematic diagram of a control map showing the correspondence between the steering angle | θse | after absolute value conversion and the base current Ieba at the time of temporary sensor failure.
The temporary base current calculation unit 282b is illustrated in FIG. 8 that shows the correspondence between the steering angle | θse | after absolute value and the base current Ieba at the time of failure of the temporary sensor, which are created based on empirical rules and stored in the ROM in advance. By substituting the steering angle | θse | after the absolute value into the control map, the base current Ieba at the time of temporary sensor failure is calculated.

(Vehicle speed correction coefficient setting unit 282c)
FIG. 9 is a schematic diagram of a control map showing the correspondence between the vehicle speed correction coefficient Kv and the vehicle speed Vc.
The vehicle speed correction coefficient setting unit 282c substitutes the vehicle speed Vc into the control map illustrated in FIG. 9 that shows the correspondence between the vehicle speed correction coefficient Kv and the vehicle speed Vc, which is created in advance based on empirical rules and stored in the ROM. Thus, the vehicle speed correction coefficient Kv is calculated.
In the control map illustrated in FIG. 9, the vehicle speed correction coefficient Kv when the vehicle speed Vc is zero (km / h) is 1, and the vehicle speed correction coefficient Kv when the vehicle speed Vc is approximately 1 (km / h). 0.5. Further, the vehicle speed correction coefficient Kv when the vehicle speed Vc is approximately 5 (km / h) is set to approximately 0.3, and the vehicle speed correction coefficient Kv is changed while the vehicle speed Vc changes from approximately 1 to approximately 5 (km / h). It is gradually decreasing. Further, the vehicle speed correction coefficient Kv when the vehicle speed Vc is about 40 (km / h) is set to about 0.4, and the vehicle speed correction coefficient Kv is changed while the vehicle speed Vc changes from about 5 to about 40 (km / h). It is gradually rising. The vehicle speed correction coefficient Kv is gradually decreased as the vehicle speed Vc increases from approximately 40 (km / h).

(Vehicle speed correction coefficient multiplier 282d)
The vehicle speed correction coefficient multiplication unit 282d multiplies the temporary sensor failure base current Ieba calculated by the temporary base current calculation unit 282b by the vehicle speed correction coefficient Kv set by the vehicle speed correction coefficient setting unit 282c, thereby causing a sensor failure. The time base current Ieb is calculated, and the calculated sensor failure time base current Ieb is output to the return correction coefficient multiplier 284.

<Return correction coefficient setting unit 283>
FIG. 10 is a schematic configuration diagram of the return correction coefficient setting unit 283.
The return correction coefficient setting unit 283 includes an absolute value converting unit 283a that converts the calculated steering angle θsc calculated by the steering angle calculating unit 73 into an absolute value, and an absolute value converted into an absolute value by the absolute value converting unit 283a. A temporary return correction coefficient calculation unit 283b that calculates a temporary return correction coefficient Kra, which is a temporary return correction coefficient Kr, based on the rear steering angle | θsc |. The return correction coefficient setting unit 283 includes a first selection unit 283c that selects the temporary return correction coefficient Kra calculated by the temporary return correction coefficient calculation unit 283b or a predetermined value according to the vehicle speed Vc. . Further, the return correction coefficient setting unit 283 turns the steering wheel 101 based on the calculated steering angle θsc calculated by the steering angle calculation unit 73 and the substitution steering angle θse calculated by the substitution steering angle calculation unit 281. A determination unit 283d is provided for determining whether it is inserted or cut back. Further, the return correction coefficient setting unit 283 includes a second selection unit 283e that selects a value selected by the first selection unit 283c or a predetermined value according to the steering situation determined by the determination unit 283d. .

(Absolute part 283a)
The absolute value converting unit 283a calculates the absolute value of the calculated steering angle θsc having a plus or minus sign. The value calculated by the absolute value converting unit 283a is the steering angle | θsc | after the absolute value conversion.

(Temporary return correction coefficient calculation unit 283b)
FIG. 11 is a schematic diagram of a control map showing the correspondence between the steering angle | θsc | after absolute value conversion and the provisional return correction coefficient Kra.
The provisional return correction coefficient calculation unit 283b is illustrated in FIG. 11 illustrating the correspondence between the absolute value steering angle | θsc | and the provisional return correction coefficient Kra, which is created based on an empirical rule and stored in the ROM in advance. The temporary return correction coefficient Kra is calculated by substituting the steering angle | θsc | after absolute value into the control map.
In the control map shown in FIG. 11, when the absolute steering angle | θsc | is equal to or smaller than the predetermined lower steering angle θd, the provisional return correction coefficient Kra is zero, and the absolute steering angle is obtained. When | θsc | is equal to or greater than a predetermined upper steering angle θu, the provisional return correction coefficient Kra is 1. When the absolute steering angle | θsc | is between the lower steering angle θd and the upper steering angle θu, the provisional return correction coefficient Kra gradually increases from zero to one.

(First selection unit 283c)
The first selection unit 283c selects the temporary return correction coefficient Kra calculated by the temporary return correction coefficient calculation unit 283b when the vehicle speed Vc is equal to or higher than a predetermined vehicle speed Vcd, and when the vehicle speed Vc is less than the predetermined vehicle speed Vcd. Selects 1 which is a predetermined value. The predetermined vehicle speed Vcd can be exemplified as 1 km / h.

(Determination unit 283d)
The determination unit 283d multiplies the calculated steering angle θsc calculated by the steering angle calculation unit 73 by the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 (= θsc × If θse) is greater than or equal to zero, it is determined that the cut is made, and if the multiplication value is less than zero, it is determined that the cut is made.

(Second selection unit 283e)
The second selection unit 283e selects 1 which is a predetermined value when it is determined that the determination unit 283d has been cut, and the second selection unit 283e has a first value when it has been determined that the determination unit 283d has been cut back. The temporary return correction coefficient Kra selected by the 1 selection unit 283c is selected. Then, the second selection unit 283e outputs the selected value as a return correction coefficient Kr.

  With the configuration described above, the return correction coefficient setting unit 283 sets the return correction coefficient Kr periodically (for example, every 1 millisecond). Then, the return correction coefficient setting unit 283 sets the correction coefficient Kr to 1 when the steering wheel 101 is cut. Further, the return correction coefficient setting unit 283 sets the correction coefficient Kr to 1 when the vehicle speed Vc is less than the predetermined vehicle speed Vcd even when the steering wheel 101 is turned back. Further, the return correction coefficient setting unit 283 is configured such that when the steering wheel 101 is turned back and the vehicle speed Vc is equal to or higher than the predetermined vehicle speed Vcd, the post-absolute steering angle | θsc | is equal to or higher than the upper steering angle θu. In some cases, the correction coefficient Kr is set to 1. On the other hand, when the steering wheel 101 is turned back and the vehicle speed Vc is equal to or higher than the predetermined vehicle speed Vcd, the return correction coefficient setting unit 283 has a steering angle | θsc | after the absolute value is less than the upper steering angle θu. In some cases, a correction coefficient Kr corresponding to the steering angle | θsc | after the absolute value is set.

<Rotation speed correction coefficient setting unit 285>
The rotation speed correction coefficient setting unit 285 sets a rotation speed correction coefficient Km corresponding to the motor rotation speed Vm.
FIG. 12 is a schematic diagram of a control map showing the correspondence between the motor rotation speed Vm and the rotation speed correction coefficient Km.
The rotation speed correction coefficient setting unit 285 adds a motor map to the control map illustrated in FIG. 12 that shows the correspondence between the motor rotation speed Vm and the rotation speed correction coefficient Km, which is previously created based on empirical rules and stored in the ROM. The rotational speed correction coefficient Km is calculated by substituting the rotational speed Vm.
In the control map shown in FIG. 12, when the motor rotational speed Vm is equal to or lower than the predetermined rotational speed Vm0, the rotational speed correction coefficient Km is 1, and when the motor rotational speed Vm is larger than the rotational speed Vm0. The rotational speed correction coefficient Km is a value that gradually decreases from 1 to zero as the motor rotational speed Vm increases.

FIG. 13 is a schematic diagram of a control map showing the correspondence between the vehicle speed Vc and the vehicle speed correction coefficient Kc.
The rotational speed correction coefficient setting unit 285 corrects the motor rotational speed Vm to be substituted into the control map shown in FIG. 12 using the vehicle speed correction coefficient Kc set based on the control map and the vehicle speed Vc shown in FIG. (Motor rotation speed Vm to be substituted into the control map shown in FIG. 12 = motor rotation speed Vm × Kc calculated by the motor rotation speed calculation unit 72).
In the control map illustrated in FIG. 13, the vehicle speed correction coefficient Kc when the vehicle speed Vc is from zero to the first vehicle speed V1 is 1, and the vehicle speed correction coefficient Kc is approximately 0 when the vehicle speed Vc is greater than the second vehicle speed V2. .3. Further, the vehicle speed correction coefficient Kc is set to a value that gradually decreases from 1 to 0.3 while the vehicle speed Vc increases from the first vehicle speed V1 to the second vehicle speed V2. It can be illustrated that the first vehicle speed V1 is approximately 15 (km / h) and the second vehicle speed V2 is approximately 35 (km / h).

  With the configuration described above, the rotation speed correction coefficient setting unit 285 sets the rotation speed correction coefficient Km periodically (for example, every 1 millisecond). Then, the rotational speed correction coefficient setting unit 285 sets the rotational speed correction coefficient Km to a value smaller than 1 in order to suppress excessive cutting when the motor rotational speed Vm is high, in other words, when the steering angular speed of the steering wheel 101 is high. Set to. However, in order to secure the assist force necessary for avoiding danger when the vehicle speed Vc is high, when the vehicle speed Vc is higher than the second vehicle speed V2, the motor rotation speed Vm substituted into the control map shown in FIG. Correct so that On the other hand, when the vehicle speed Vc is lower than the first vehicle speed V1, no correction is made to reduce the motor rotation speed Vm that is substituted into the control map shown in FIG.

<Steering angular acceleration correction coefficient setting unit 287>
FIG. 14 is a schematic configuration diagram of the steering angular acceleration correction coefficient setting unit 287.
The steering angular acceleration correction coefficient setting unit 287 includes a steering angular acceleration calculation unit 287a that calculates a steering angular acceleration θa based on the calculated steering angle θsc calculated by the steering angle calculation unit 73, and a steering angular acceleration calculation unit 287a. And an absolute value converting unit 287b that converts the calculated steering angular acceleration θa into an absolute value. Further, the steering angular acceleration correction coefficient setting unit 287 is a temporary steering angular acceleration that is a temporary steering angular acceleration correction coefficient Ks based on the absolute value-converted steering angle | θa | converted into an absolute value by the absolute value converting unit 287b. A provisional steering angular acceleration correction coefficient calculation unit 287c for calculating the correction coefficient Ksa is provided. Further, the steering angular acceleration correction coefficient setting unit 287 includes a vehicle speed correction coefficient setting unit 287d that sets the vehicle speed correction coefficient Ka based on the vehicle speed signal v, and a temporary steering angle calculated by the temporary steering angular acceleration correction coefficient calculation unit 287c. A vehicle speed correction coefficient multiplier 287e that calculates a steering angular acceleration correction coefficient Ks by multiplying the acceleration correction coefficient Ksa by the vehicle speed correction coefficient Ka set by the vehicle speed correction coefficient setting unit 287d.

(Steering angular acceleration calculation unit 287a)
The steering angular acceleration calculation unit 287a first calculates the difference between the previous value and the current value of the calculated steering angle θsc calculated periodically (for example, every 1 millisecond (sampling time)) by the steering angle calculation unit 73 as a sampling time. And the previous steering angular velocity θvn−1 obtained by dividing the difference between the previous value and the previous value of the calculated steering angle θsc by the sampling time. Then, the steering angular acceleration calculation unit 287a calculates the steering angular acceleration θa by dividing the difference between the current steering angular velocity θvn and the previous steering angular velocity θvn−1 by the sampling time.

(Absolute value conversion unit 287b)
The absolute value converting unit 287b calculates the absolute value of the steering angular acceleration θa having a plus or minus sign. The value calculated by the absolute value converting unit 287b is the steering angular acceleration | θa | after the absolute value conversion.

(Temporary steering angular acceleration correction coefficient calculation unit 287c)
FIG. 15 is a schematic diagram of a control map showing correspondence between the steering angular acceleration after absolute value conversion | θa | and the provisional steering angular acceleration correction coefficient Ksa.
The provisional steering angular acceleration correction coefficient calculation unit 287c indicates the correspondence between the absolute steering angle acceleration | θa | and the provisional steering angular acceleration correction coefficient Ksa that are created based on empirical rules and stored in the ROM in advance. The temporary steering angular acceleration correction coefficient Ksa is calculated by substituting the absolute steering angle acceleration | θa | into the control map illustrated in FIG.
In the control map shown in FIG. 15, when the steering angular acceleration after the absolute value | θa | is equal to or smaller than the predetermined steering angular acceleration θa0, the provisional steering angular acceleration correction coefficient Ksa is 1, and the absolute value is obtained. When the rear steering angular acceleration | θa | is larger than the steering angular acceleration θa0, the temporary steering angular acceleration correction coefficient Ksa is a value that gradually decreases from 1 to zero as the steering angular acceleration | θa | after the absolute value is increased. Become.

(Vehicle speed correction coefficient setting unit 287d)
FIG. 16 is a schematic diagram of a control map showing the correspondence between the vehicle speed correction coefficient Ka and the vehicle speed Vc.
The vehicle speed correction coefficient setting unit 287d substitutes the vehicle speed Vc into the control map illustrated in FIG. 16 that shows the correspondence between the vehicle speed correction coefficient Ka and the vehicle speed Vc, which is created in advance based on empirical rules and stored in the ROM. Thus, the vehicle speed correction coefficient Ka is calculated.
In the control map shown in FIG. 16, the vehicle speed correction coefficient Ka is 1 when the vehicle speed Vc is equal to or lower than the predetermined vehicle speed Vc0, and the vehicle speed correction coefficient Ka is when the vehicle speed Vc is higher than the vehicle speed Vc0. As the vehicle speed Vc increases, the value gradually decreases from 1 to zero.

(Vehicle speed correction coefficient multiplier 287e)
The vehicle speed correction coefficient multiplication unit 287e multiplies the temporary steering angular acceleration correction coefficient Ksa calculated by the temporary steering angular acceleration correction coefficient calculation unit 287c and the vehicle speed correction coefficient Ka set by the vehicle speed correction coefficient setting unit 287d. To calculate the steering angular acceleration correction coefficient Ks, and outputs the calculated steering angular acceleration correction coefficient Ks to the steering angular acceleration correction coefficient multiplier 288.

  With the configuration described above, the steering angular acceleration correction coefficient setting unit 287 sets the steering angular acceleration correction coefficient Ks periodically (for example, every 1 millisecond). Then, the steering angular acceleration correction coefficient setting unit 287 sets the steering angular acceleration correction coefficient Ks to a value smaller than 1 when the absolute value of the steering angular acceleration θa is large. When the vehicle speed Vc is high, the steering angular acceleration correction coefficient Ks is corrected to be a value smaller than 1.

<Limit processing unit 289>
When the base current Iebs after the steering angular acceleration correction calculated by the steering angular acceleration correction coefficient multiplying unit 288 is larger than a predetermined upper limit value, the limit processing unit 289 sets the upper limit value to the base current Il after the limit processing. When the calculated steering angular acceleration corrected base current Iebs is equal to or lower than the upper limit value, the calculated steering angular acceleration corrected base current Iebs is output as it is as the post-limit processing base current Il.

<Encoding processing unit 290>
When the sign of the substitution steering angle θse calculated by the substitution steering angle calculation section 281 is positive, the encoding processing section 290 adds a plus sign to the post-limit processing base current Il output from the limit processing section 289. Is attached. On the other hand, when the sign of the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 is minus, the encoding processing unit 290 minus the limit processed base current Il output from the limit processing unit 289. The symbol is attached.

  The return correction coefficient multiplication unit 284, the rotation speed correction coefficient multiplication unit 286, the steering angular acceleration correction coefficient multiplication unit 288, the limit processing unit 289, and the encoding processing unit 290 described above are periodically (for example, every 1 millisecond). Perform each process. Therefore, the encoding processing unit 290 outputs the post-limit processing base current Il to which the code is attached to the fade processing unit 291 periodically (for example, every 1 millisecond).

<Fade processing unit 291>
When the sensor failure detection unit 27 detects a failure of the torque sensor 109 in processing periodically (for example, every 1 millisecond), the fade processing unit 291 determines a value determined based on the vehicle speed Vc when the sensor failure occurs. When the current Ie is determined and no failure of the torque sensor 109 is detected, the sensor failure current Ie is determined to be zero.
Then, when the sensor failure detection unit 27 detects a failure of the torque sensor 109 and determines the sensor failure current Ie based on the vehicle speed Vc, the fade processing unit 291 controls the vehicle speed Vc as illustrated in FIG. As shown in the map, when the vehicle speed correction coefficient Kv has a magnitude other than between zero and approximately 1 (km / h) (a speed greater than 1 (km / h)), the sensor malfunctions. The current Ie is determined as the rotation speed-corrected base current Iebv to which the code is assigned by the encoding processing unit 290. On the other hand, when the vehicle speed Vc is 1 (km / h) or less, it takes a predetermined period from the current Ie at the time of sensor failure to the base current Iebv after the rotational speed correction, which is provided with a sign by the current encoding processing unit 290. Gradually change. For example, when the vehicle speed Vc is decelerating from 1 (km / h), the base after rotation speed correction, which is encoded by the current encoding processing unit 290 from the previous sensor failure current Ie in 1 second A value that changes to the current Iebv is determined as a sensor failure current Ie periodically (for example, every 1 millisecond). On the other hand, when the vehicle speed Vc is accelerating from zero, in 0.5 seconds, the current Ie at the time of sensor failure is changed to the base current Iebv after rotation speed correction that is signed by the current encoding processing unit 290. The changing value is determined as the sensor failure current Ie periodically (for example, every 1 millisecond).

According to the steering device 100 configured as described above, normal assist control is performed using the target current It determined based on the steering torque T detected by the torque sensor 109 when the torque sensor 109 has failed as an assist current. Even when it cannot be performed, the assist control at the time of failure can be performed based on the output value from the resolver 120.
When performing the assist control at the time of failure, the vehicle speed correction coefficient Kv is set to 1 based on the control map illustrated in FIG. 9 when the vehicle has a large static friction force, so the assist force is greater than when the vehicle speed Vc is greater than zero. Becomes larger. As a result, even in the case of assist control at the time of failure, handling characteristics at the time of parking and stopping are ensured. On the other hand, when the vehicle speed Vc is greater than approximately 1 (km / h) and the vehicle moves to the dynamic friction force region, the vehicle speed correction coefficient Kv is set to 0.5 or less based on the control map illustrated in FIG. Since the assist force is suddenly weakened, it is adjusted so that there is no excessive assist. Further, in a region where the vehicle is turning and the vehicle speed Vc is larger than about 10 (km / h), the steering force tends to increase. At this speed, the vehicle speed correction coefficient Kv is about 5 (km / h). The assist power increases because it is higher than that. However, since the vehicle speed correction coefficient Kv is set small in a region where the vehicle speed Vc is greater than approximately 40 (km / h), the assist force is weakened. Thereby, the wobbling of the vehicle at a high vehicle speed is suppressed.
Further, even when the vehicle speed correction coefficient Kv changes greatly between zero and approximately 1 (km / h), the assist force is gradually changed by the fade processing unit 291, so that the assist force changes abruptly. The deterioration of the steering feeling due to this is suppressed.

  Further, in the assist control at the time of failure, excessive rotation when the steering angular speed of the steering wheel 101 is large is suppressed by the rotational speed correction coefficient Km set by the rotational speed correction coefficient setting unit 285. However, since the rotational speed correction coefficient Km is set so as to increase when the vehicle speed Vc is higher than the second vehicle speed V2 (see FIGS. 12 and 13), assistance necessary for avoiding danger when the vehicle speed Vc is high. Power is secured. Further, when the vehicle speed Vc is lower than the first vehicle speed V1, the rotational speed correction coefficient Km is set so as to be small (see FIGS. 12 and 13), so that the steering is taken even during low-μ road low speed traveling. Is suppressed. Further, the steering catch when the vehicle is stopped is suppressed.

  Further, in the assist control at the time of failure, the steering angular acceleration correction coefficient Ks set by the steering angular acceleration correction coefficient setting unit 287 is corrected so that the assist force is reduced when the steering angular acceleration of the steering wheel 101 is large. Therefore, even if the steering wheel 101 is taken while traveling on a low μ road, the assist force is reduced. Therefore, according to the control device 10 according to the present embodiment, steering (or steering) can be suppressed, and steering stability can be ensured. On the other hand, when traveling on a high μ road such as a leveled asphalt road, the steering angular acceleration set by the steering angular acceleration correction coefficient setting unit 287 is taken into consideration that steering is unlikely to occur (the steering angular acceleration is small). The correction coefficient Ks is configured to be set to 1. Therefore, the assist force is not corrected so as to be reduced. As a result, the control device 10 according to the present embodiment can ensure a sufficient assist force on the asphalt road (high μ road).

  As described above, according to the steering device 100 according to the present embodiment, it is possible to apply the assist force according to the use state of the vehicle and the road surface change even during the assist control at the time of failure. That is, it is possible to realize the provision of assist force for avoiding danger and also to provide assist force for general travel. As a result, even after a failure occurs in the torque sensor 109, it is possible to go to the home or the nearest dealer, and the safety of the driver can be ensured.

  In the embodiment described above, the fade processing unit 291 fades the sensor failure current Ie output from the sensor failure current determination unit 28 in accordance with the vehicle speed Vc. Also good. For example, the base current Iebs after the steering angular acceleration correction input to the limit processing unit 289 may be faded before the limit processing unit 289. As a result, the steering feeling is prevented from deteriorating due to the abrupt change of the assist force.

  In the above-described embodiment, the sensor failure current Ie is determined using the rotation angle (steering angle) of the steering wheel 101 calculated by the steering angle calculation unit 73 based on the output signal from the resolver 120. However, it is not particularly limited to such an embodiment. For example, a steering angle sensor that detects the rotation angle of the steering wheel 101 may be provided, and the sensor failure current Ie may be determined based on the steering angle detected by the steering angle sensor.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 28 ... Current determination part at the time of sensor failure, 30 ... Control part, 100 ... Electric power steering apparatus, 109 ... Torque sensor, 110 ... Electric motor, 120 ... Resolver

Claims (4)

An electric motor for applying an assisting force to the steering wheel of the vehicle;
Torque detecting means for detecting a steering torque of the steering wheel;
Steering angle estimating means for estimating a steering angle which is a rotation angle of the steering wheel;
Failure detection means for detecting a failure of the torque detection means;
When the failure detecting means detects a failure, a basic auxiliary force serving as a basis of the auxiliary force is determined based on the steering angle estimated by the steering angle estimating means, and the basic assistance force is determined according to the acceleration of the steering angle. Control means for controlling the electric motor so that the auxiliary force is corrected to the auxiliary force;
An electric power steering apparatus comprising: The said control means correct | amends the said basic auxiliary force so that the said auxiliary force may become small when the acceleration of the said steering angle is larger than the predetermined predetermined steering angular acceleration. Electric power steering device. The said control means correct | amends the said basic auxiliary force so that the said auxiliary force may become small when the vehicle speed which is the moving speed of the said vehicle is larger than the predetermined predetermined vehicle speed. Electric power steering device. 4. The control unit according to claim 1, wherein the control unit determines the auxiliary force based on a steering torque detected by the torque detection unit when the failure detection unit has not detected a failure. The electric power steering apparatus according to Item 1.

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