JP2011015593A - Motor control device, and steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device capable of controlling motors by new control systems without using any rotational angle sensors.SOLUTION: The motor is driven by a γ-axis current Iof a γδ coordinate system, namely a virtual rotating coordinate system. The γδ coordinate system is a coordinate system following a control angle θ, namely a rotational angle on control. An assist torque corresponding to a difference (load angle θ) between the control angle θand a rotor angle θis generated. Contrarily, a PI control unit 23 generates an addition angle α to bring the detection torque T closer to an instruction steering torque T. The current value θ(n) of the control angle θis obtained by adding the addition angle α to the last value θ(n-1) of the control angle θ. An addition angle change unit 25 changes the addition angle α as required. An absolute value of a detection steering angle is given to the addition angle change unit 25 via a motor load operation unit 27. When the absolute value of the detection steering angle becomes not less than a prescribed value, the addition angle α is changed to 0.

Description

  The present invention relates to a motor control apparatus for driving a brushless motor and a vehicle steering apparatus including the motor control apparatus. An example of a vehicle steering device is an electric power steering device.

  A motor control device for driving and controlling a brushless motor is generally configured to control the supply of motor current in accordance with the output of a rotation angle sensor for detecting the rotation angle of the rotor. As the rotation angle sensor, a resolver that outputs a sine wave signal and a cosine wave signal corresponding to the rotor rotation angle (electrical angle) is generally used. However, the resolver is expensive, has a large number of wires, and has a large installation space. Therefore, there exists a subject that the cost reduction and size reduction of an apparatus provided with the brushless motor are inhibited.

  Therefore, a sensorless driving method for driving a brushless motor without using a rotation angle sensor has been proposed. The sensorless driving method is a method for estimating the phase of the magnetic pole (electrical angle of the rotor) by estimating the induced voltage accompanying the rotation of the rotor. Since the induced voltage cannot be estimated when the rotor is stopped and when rotating at a very low speed, the phase of the magnetic pole is estimated by another method. Specifically, a sensing signal is injected into the stator, and a motor response to the sensing signal is detected. Based on this motor response, the rotor rotational position is estimated.

JP 2007-267549 Gazette

  The above sensorless driving method estimates the rotational position of the rotor using an induced voltage or a sensing signal, and controls the motor based on the rotational position obtained by the estimation. However, this drive system is not suitable for any use. For example, a brushless motor used as a drive source of an electric power steering apparatus or other vehicle steering apparatus that applies a steering assist force to a steering mechanism of a vehicle. A method for applying to control has not been established yet. Therefore, realization of sensorless control by another method is desired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control device that can control a motor by a new control method that does not use a rotation angle sensor, and a vehicle steering device that includes the motor control device.

In order to achieve the above object, the invention according to claim 1 is a motor control device (5) for controlling a motor (3) including a rotor (50) and a stator (55) facing the rotor. A current driving means (30, 32 to 36) for driving the motor with an axial current value (I _γ ^* ) of a rotating coordinate system according to a control angle (θ _C ) which is a control rotation angle; Control angle calculation means (26) for obtaining the current value of the control angle by adding the addition angle to the previous value of the control angle for each calculation cycle, and motor load calculation means for measuring or estimating the load of the motor (27) and limiting means (25, 28, 31) for limiting the control angle, the addition angle, or the shaft current value when the motor load measured or estimated by the motor load calculating means is greater than or equal to a predetermined value. ) And including a motor A control device. The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.

  According to this configuration, the axis current value (hereinafter “virtual axis”) of the rotating coordinate system (γδ coordinate system, hereinafter referred to as “virtual rotating coordinate system”, the coordinate axis of this virtual rotating coordinate system being referred to as “virtual axis”) according to the control angle. While the motor is driven by the "shaft current value"), the control angle is updated by adding the addition angle every calculation cycle. Thus, the necessary torque can be generated by driving the motor with the virtual axis current value while updating the control angle, that is, while updating the coordinate axis (virtual axis) of the virtual rotation coordinate system. Thus, an appropriate torque can be generated from the motor without using a rotation angle sensor. That is, an appropriate torque is generated by introducing a deviation amount (load angle) between the coordinate axis of the rotating coordinate system (dq coordinate system) and the virtual axis according to the magnetic pole direction of the rotor to an appropriate value.

  In the present invention, the motor load is measured or estimated by the motor load calculating means. When the motor load measured or estimated by the motor load calculation means is equal to or greater than a predetermined value, the control angle, the addition angle, or the shaft current value is limited. When the motor load becomes larger than the maximum output torque of the motor, there is no suitable value of the load angle corresponding to the required torque, and the torque control is impossible (hereinafter referred to as “torque control impossible state”). ) This makes it impossible to generate an appropriate torque from the motor. Therefore, in the present invention, when the motor load is a predetermined value or more, the control load, the addition angle, or the shaft current value is limited to prevent the motor load from becoming larger than the maximum output torque of the motor. Or avoiding the torque control disabled state.

  More specifically, when the motor load is a predetermined value or more, for example, the control angle is limited or the addition angle is made zero so that the control angle does not change. Alternatively, when the motor load is equal to or greater than a predetermined value, the shaft current value is made zero. If the control angle does not change by limiting the control angle or setting the addition angle to zero, the motor is locked. For example, when the motor load increases according to the rotation amount from the reference position of the motor, the motor load does not increase any more when the motor is locked. Therefore, it is possible to avoid the motor load from becoming larger than the maximum output torque of the motor. On the other hand, when the shaft current value is set to zero, the torque control operation of the motor is stopped, so that it is possible to prevent the torque control from being disabled.

The motor load calculating means (27) may include a motor load measuring means for measuring the load of the motor, or may include a motor load estimating means for estimating the load of the motor. .
The invention according to claim 2 includes a motor (3) for applying a driving force to the steering mechanism (2) of the vehicle, and a motor control device according to claim 1 for controlling the motor. The vehicle steering apparatus estimates a load of the motor based on a steering angle of a steering member operated for steering the vehicle or a turning angle of a wheel of the vehicle. In this configuration, the motor load is estimated based on the steering angle of the steering member operated for steering the vehicle or the turning angle of the vehicle wheel. When the estimated motor load is equal to or greater than a predetermined value, the control angle, the addition angle, or the shaft current value is limited. Therefore, even in this configuration, it is possible to avoid the motor load from becoming larger than the maximum torque that can be output from the motor, or to prevent the torque control from being disabled.

As the motor load measuring means, for example, an axial force sensor for detecting a force acting on a rack shaft, a tire force sensor for detecting a stress acting on a tire, or the like can be used.
The motor control device includes a torque detection means (1) for detecting a steering torque applied to an operation member operated for steering the vehicle, and an instruction for setting an instruction steering torque as a target value of the steering torque. Steering torque setting means (21), and addition angle calculation means (22,) for calculating the addition angle according to a deviation between the instruction torque set by the instruction torque setting means and the steering torque detected by the torque detection means 23) may be further included.

  According to this configuration, the command steering torque is set, and the addition angle is calculated according to the deviation between the command steering torque and the steering torque (detected value). Thus, the addition angle is determined so that the steering torque becomes the command steering torque, and the control angle corresponding to the addition angle is determined. Therefore, by appropriately determining the instruction steering torque, it is possible to generate an appropriate driving force from the motor and apply it to the steering mechanism. That is, the deviation (load angle) between the coordinate axis of the rotating coordinate system (dq coordinate system) and the virtual axis according to the magnetic pole direction of the rotor is led to a value corresponding to the command steering torque. As a result, an appropriate torque is generated from the motor, and a driving force according to the driver's steering intention can be applied to the steering mechanism.

  In a vehicle steering device (for example, an electric power steering device) in which an operation member and a steering mechanism are mechanically coupled, the driving force of a motor is applied to the steering mechanism as an assist torque (steering assist force). A value obtained by subtracting the assist torque from the motor load (load torque) is the steering torque that the driver should apply to the operation member. When the load torque becomes larger than the maximum assist torque that can be output by the motor, the appropriate value of the load angle does not exist, and the torque control becomes impossible, and appropriate assist torque cannot be generated.

  In the present invention, when the motor load is equal to or greater than a predetermined value, the control angle, the addition angle, or the shaft current value is limited. More specifically, when the motor load is a predetermined value or more, for example, the control angle is limited or the addition angle is made zero so that the control angle does not change. Alternatively, when the motor load is equal to or greater than a predetermined value, the shaft current value is made zero. When the control angle does not change due to the restriction of the control angle or the addition angle, the motor is locked, and the driver cannot operate the operation member any more. More specifically, an operation for increasing the steering angle is restricted. Since the motor load increases as the steering angle increases, the motor load does not increase any more. As a result, it is possible to avoid the motor load from becoming larger than the maximum assist torque that the motor can output. On the other hand, when the shaft current value is set to zero, the steering assist operation is stopped and a so-called manual steer state is set, so that it is possible to avoid a torque control disabled state.

  The motor control device further includes a steering angle detection means (4) for detecting a steering angle of the operation member, and the instruction torque setting means is an instruction steering torque according to a steering angle detected by the steering angle detection means. Is preferably set. According to this configuration, since the instruction steering torque is set according to the steering angle of the operation member, an appropriate torque according to the steering angle can be generated from the motor, and the steering torque applied to the operation member by the driver can be increased. The value can be derived according to the steering angle. Thereby, a favorable steering feeling can be obtained.

  The command torque setting means may set the command steering torque according to the vehicle speed detected by the vehicle speed detection means (6) for detecting the vehicle speed of the vehicle. According to this configuration, since the command steering torque is set according to the vehicle speed, so-called vehicle speed sensitive control can be performed. As a result, a good steering feeling can be realized. For example, an excellent steering feeling can be obtained by setting the command steering torque to be smaller as the vehicle speed is higher, that is, at higher speeds.

1 is a block diagram for explaining an electrical configuration of an electric power steering apparatus to which a motor control device according to an embodiment of the present invention is applied. FIG. It is an illustration figure for demonstrating the structure of a motor. It is a control block diagram of the electric power steering device. It is a figure which shows the example of a characteristic of the instruction | indication steering torque with respect to a steering angle. It is a figure for demonstrating the effect | action of a steering torque limiter. It is a figure which shows the example of a setting of (gamma) axis instruction | indication electric current value. It is a flowchart for demonstrating the effect | action of an addition angle limiter. It is a flowchart which shows the procedure of the addition angle change process by an addition angle change part. It is a flowchart which shows the procedure of the control angle restriction | limiting process by a control angle restriction | limiting part. It is a block diagram for demonstrating the electric constitution of the electric power steering apparatus which concerns on other embodiment of this invention. It is a flowchart which shows the procedure of the command current value change process by a command current value change part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram for explaining an electrical configuration of an electric power steering device (an example of a vehicle steering device) to which a motor control device according to an embodiment of the present invention is applied. This electric power steering apparatus includes a torque sensor 1 for detecting a steering torque T applied to a steering wheel 10 as an operation member for steering the vehicle, and a steering assist force via a speed reduction mechanism 7 to the steering mechanism 2 of the vehicle. The motor 3 (brushless motor) that gives the power, the steering angle sensor 4 that detects the steering angle that is the rotation angle of the steering wheel 10, the motor control device 5 that drives and controls the motor 3, and the electric power steering device are mounted. And a vehicle speed sensor 6 for detecting the speed of the vehicle. The rudder angle sensor 4 detects the amount of rotation (rotation angle) of the steering wheel 10 from the neutral position (reference position) of the steering wheel 10 in both forward and reverse directions. , And the amount of rotation from the neutral position to the left is output as a negative value.

The motor control device 5 drives the motor 3 according to the steering torque detected by the torque sensor 1, the steering angle detected by the steering angle sensor 4, and the vehicle speed detected by the vehicle speed sensor 6, thereby responding to the steering situation and the vehicle speed. Realize appropriate steering assistance.
In this embodiment, the motor 3 is a three-phase brushless motor. As schematically shown in FIG. 2, the rotor 50 as a field and a U-phase, V arranged in a stator 55 facing the rotor 50, V Phase and W phase stator windings 51, 52, 53. The motor 3 may be of an inner rotor type in which a stator is disposed facing the outside of the rotor, or may be of an outer rotor type in which a stator is disposed facing the inside of a cylindrical rotor.

Three-phase fixed coordinates (UVW coordinate system) are defined in which the U, V, and W axes are taken in the direction of the stator windings 51, 52, and 53 of each phase. Also, a two-phase rotational coordinate system (dq coordinate system) in which the d axis (magnetic pole axis) is taken in the magnetic pole direction of the rotor 50 and the q axis (torque axis) is taken in the direction perpendicular to the d axis in the rotation plane of the rotor 50. The actual rotating coordinate system) is defined. The dq coordinate system is a rotating coordinate system that rotates with the rotor 50. In the dq coordinate system, since only the q-axis current contributes to the torque generation of the rotor 50, the d-axis current may be set to zero and the q-axis current may be controlled according to the desired torque. A rotation angle (rotor angle) θ _M of the rotor 50 is a rotation angle of the d-axis with respect to the U-axis. dq coordinate system is an actual rotating coordinate system that rotates in accordance with the rotor angle theta _M. With the use of the rotor angle theta _M, coordinate conversion may be made between the UVW coordinate system and the dq coordinate system.

On the other hand, in this embodiment, a control angle θ _C representing a control rotation angle is introduced. The control angle θ _C is a virtual rotation angle with respect to the U axis. A virtual axis corresponding to the control angle θ _C is a γ axis, and an axis advanced by 90 ° with respect to the γ axis is a δ axis, and a virtual two-phase rotational coordinate system (γδ coordinate system, virtual rotational coordinate system) is defined. Define. When the control angle θ _C is equal to the rotor angle θ _M , the γδ coordinate system, which is a virtual rotation coordinate system, matches the dq coordinate system, which is an actual rotation coordinate system. That is, the γ-axis as the virtual axis matches the d-axis as the real axis, and the δ-axis as the virtual axis matches the q-axis as the real axis. γδ coordinate system is an imaginary rotating coordinate system that rotates in accordance with the control angle theta _C. Coordinate conversion between the UVW coordinate system and the γδ coordinate system can be performed using the control angle θ _C.

A difference between the control angle θ _C and the rotor angle θ _M is defined as a load angle θ _L (= θ _C −θ _M ).
When the γ-axis current I _γ is supplied to the motor 3 according to the control angle θ _C, the q-axis component of the γ-axis current I _γ (orthographic projection onto the q-axis) contributes to the q-axis current I _q that contributes to the torque generation of the rotor 50. Become. That is, the relationship of the following formula (1) is established between the γ-axis current I _γ and the q-axis current I _q .
I _q = I _γ · sin θ _L (1)
Refer to FIG. 1 again. The motor control device 5 detects a current flowing in a microcomputer 11, a drive circuit (inverter circuit) 12 that is controlled by the microcomputer 11 and supplies electric power to the motor 3, and a stator winding of each phase of the motor 3. And a current detection unit 13.

The current detection unit 13 uses phase currents I _U , I _V , I _W (hereinafter, collectively referred to as “three-phase detection current I _UVW ”) flowing through the stator windings 51, 52, 53 of each phase of the motor 3. To detect. These are current values in the coordinate axis directions in the UVW coordinate system.
The microcomputer 11 includes a CPU and a memory (such as a ROM and a RAM), and functions as a plurality of function processing units by executing a predetermined program. The plurality of function processing units include a steering torque limiter 20, an instruction steering torque setting unit 21, a torque deviation calculation unit 22, a PI (proportional integration) control unit 23, an addition angle limiter 24, and an addition angle change unit. 25, a control angle calculation unit 26, a motor load calculation unit 27, an indicated current value generation unit 30, a current deviation calculation unit 32, a PI control unit 33, a γδ / UVW conversion unit 34, a PWM (Pulse Width) A Modulation) control unit 35 and a UVW / γδ conversion unit 36 are included.

The command steering torque setting unit 21 sets the command steering torque T ^* based on the steering angle detected by the steering angle sensor 4 and the vehicle speed detected by the vehicle speed sensor 6. For example, as shown in FIG. 4, when the steering angle is a positive value (a state of steering to the right), the command steering torque T ^* is set to a positive value (torque to the right), and the steering angle is negative. The instruction steering torque T ^* is set to a negative value (torque in the left direction) when the value is in the state (steered in the left direction). Then, the command steering torque T ^* is set so that the absolute value of the steering angle increases as the absolute value of the steering angle increases (in a non-linear manner in the example of FIG. 4). However, the command steering torque T ^* is set within a predetermined upper limit value (positive value, for example, +6 Nm) and lower limit value (negative value, for example, −6 Nm). Further, the command steering torque T ^* is set such that the absolute value thereof decreases as the vehicle speed increases. That is, vehicle speed sensitive control is performed.

The steering torque limiter 20 outputs the output of the torque sensor 1 to a predetermined upper limit saturation value + T _max (+ T _max > 0. For example, + T _max = 7 Nm) and a lower limit saturation value −T _max (−T _max <0. For example, −T _max = -7 Nm). Specifically, as shown in FIG. 5, the steering torque limiter 20 outputs the detected steering torque T of the torque sensor 1 as it is between the upper limit saturation value + T _max and the lower limit saturation value −T _max . Further, the steering torque limiter 20 outputs the upper limit saturation value + T _max when the detected steering torque T of the torque sensor 1 is equal to or higher than the upper limit saturation value + T _max . Then, the steering torque limiter 20, the detected steering torque T from the torque sensor 1 is equal to or lower than the lower saturation value -T _max, and outputs the lower saturation value -T _max. The saturation values + T _max and −T _max define the boundary of the region (reliable region) where the output signal of the torque sensor 1 is stable. That is, the output signal of the torque sensor 1 is unstable in a section exceeding the upper limit saturation value T _max and a section lower than the lower limit saturation value −T _max and does not correspond to the actual steering torque. In other words, the saturation values + T _max and −T _max are determined according to the output characteristics of the torque sensor 1.

The torque deviation calculation unit 22 is detected by the command steering torque T ^* set by the command steering torque setting unit 21 and the steering torque T detected by the torque sensor 1 and subjected to the limiting process by the steering torque limiter 20 (hereinafter, for distinction). A deviation (torque deviation) ΔT (= T ^* −T) from “detected steering torque T” is obtained. The PI control unit 23 performs a PI calculation on the torque deviation ΔT. That is, the torque deviation calculation unit 22 and the PI control unit 23 constitute torque feedback control means for guiding the detected steering torque T to the command steering torque T ^* . The PI control unit 23 calculates the addition angle α for the control angle θ _C by performing PI calculation for the torque deviation ΔT. Therefore, the torque feedback control means constitutes an addition angle calculation means for calculating the addition angle α.

The addition angle limiter 24 limits the addition angle α obtained by the PI control unit 23. More specifically, the addition angle limiter 24 limits the addition angle α to a value between a predetermined upper limit value UL (positive value) and a lower limit value LL (negative value). The upper limit value UL and the lower limit value LL are determined based on a predetermined limit value ω _max (ω _max > 0. For example, the default value of ω _max = 45 degrees). The predetermined value of the predetermined limit value ω _max is determined based on, for example, the maximum steering angular velocity. The maximum steering angular velocity is a maximum value that can be assumed as the steering angular velocity of the steering wheel 10 and is, for example, about 800 deg / sec.

The change speed of the electrical angle of the rotor 50 at the maximum steering angular speed (the angular speed at the electrical angle. The maximum rotor angular speed) is the maximum steering angular speed, the reduction ratio of the speed reduction mechanism 7, and the rotor 50 as shown in the following equation (2). Given by the product of the number of pole pairs. The number of pole pairs is the number of magnetic pole pairs (pairs of N poles and S poles) that the rotor 50 has.
Maximum rotor angular speed = Maximum steering angular speed x Reduction ratio x Number of pole pairs (2)
The maximum value of the electrical angle change amount of the rotor 50 (the maximum value of the rotor angle change amount) during the calculation (control cycle) of the control angle θ _C is a value obtained by multiplying the maximum rotor angular velocity by the calculation cycle as shown in the following equation (3). It becomes.

Maximum value of rotor angle change = Maximum rotor angular speed x Calculation cycle
= Maximum steering angular velocity x reduction ratio x number of pole pairs x calculation cycle (3)
The rotor angle variation maximum value is the maximum variation of the control angle theta _C that is permitted within one calculation cycle. Therefore, the maximum value of the rotor angle change may be set as a predetermined value of the limit value ω _max . Using the limit value ω _max , the upper limit value UL and the lower limit value LL of the addition angle α can be expressed by the following equations (4) and (5), respectively.

UL = + ω _max (4)
LL = −ω _max (5)
The motor load calculation unit 27 calculates a motor load (load torque) based on the steering angle detected by the steering angle sensor 4. The load torque increases as the absolute value of the steering angle increases. Therefore, the motor load calculator 27 estimates the load torque based on the absolute value of the steering angle detected by the steering angle sensor 4. In this embodiment, the motor load calculation unit 27 gives the absolute value of the steering angle detected by the steering angle sensor 4 to the addition angle changing unit 25 as a value corresponding to the load torque. The addition angle changing unit 25 is also given a steering torque T detected by the torque sensor 1.

The addition angle changing unit 25 changes the addition angle α after the limiting process by the addition angle limiter 24 based on the absolute value of the steering angle given from the motor load calculating unit 27 and the detected steering torque T given from the torque sensor 1. . Specifically, the addition angle changing unit 25 does not change the addition angle α after the limiting process by the addition angle limiter 24 and supplies it to the control angle calculation unit 26 as it is. When the steering angle absolute value exceeds a predetermined threshold value, that is, when the load torque exceeds a predetermined value, the addition angle changing unit 25 sets the addition angle α after the limit processing by the addition angle limiter 24 to zero. Change to The changed addition angle α (= 0) is given to the control angle calculation unit 26. When the addition angle α is changed to zero, the addition angle changing unit 25 monitors the detected steering torque T while maintaining the state. When the absolute value of the detected steering torque T decreases, the addition angle changing unit 25 cancels the state where the addition angle α is zero and returns to the normal state. Details of the process (addition angle changing process) executed by the adding angle changing unit 25 will be described later. In the adder 26A of the control angle calculation unit 26, the addition angle α after the change process by the addition angle changing unit 25 is changed to the previous value θ _C (n−1) (n is the number of the current calculation cycle) of the control angle θ _C. Added (Z ^-1 represents the previous value of the signal). However, the initial value of the control angle θ _C is a predetermined value (for example, zero).

The control angle calculation unit 26 includes an adder 26A that adds the addition angle α given from the addition angle changing unit 25 to the previous value θ _C (n−1) of the control angle θ _C. That is, the control angle calculation unit 26 calculates the control angle θ _C every predetermined calculation cycle. Then, the control angle θ _C in the previous calculation cycle is set as the previous value θ _C (n−1), and the current value θ _C (n), which is the control angle θ _C in the current calculation cycle, is obtained.
The command current value generation unit 30 generates a current value to be passed through the coordinate axis (virtual axis) of the γδ coordinate system, which is a virtual rotation coordinate system corresponding to the control angle θ _C that is a control rotation angle, as the command current value. Is. Specifically, a γ-axis command current value I _γ ^* and a δ-axis command current value I _δ ^* (hereinafter referred to as “two-phase command current value I _γδ ^* ”) are generated. The command current value generation unit 30 sets the γ-axis command current value I _γ ^* to a significant value, and sets the δ-axis command current value I _δ ^* to zero. More specifically, the command current value generation unit 30 sets the γ-axis command current value I _γ ^* based on the detected steering torque T detected by the torque sensor 1.

A setting example of the γ-axis command current value I _γ ^* with respect to the detected steering torque T is shown in FIG. A dead zone NR is set in a region where the detected steering torque T is near zero. The γ-axis command current value I _γ ^* rises steeply in a region outside the dead zone NR, and is set to be a substantially constant value above a predetermined torque. Thereby, when the driver is not operating the steering wheel 10, the energization to the motor 3 is stopped, and unnecessary power consumption is suppressed.

The current deviation calculation unit 32 includes a deviation I _γ ^* −I _γ of the γ-axis detected current I _γ with respect to the γ-axis command current value I _γ ^* generated by the command current value generation unit 30 and a δ-axis command current value I _δ ^*. A deviation I _δ ^* −I _δ of the δ-axis detection current I _δ with respect to (= 0) is calculated. The γ-axis detection current I _γ and the δ-axis detection current I _δ are supplied from the UVW / γδ conversion unit 36 to the deviation calculation unit 32.

The UVW / γδ conversion unit 36 converts the three-phase detection current I _UVW (U-phase detection current I _U , V-phase detection current I _V and W-phase detection current I _W ) of the UVW coordinate system detected by the current detection unit 13 to γδ. Two-phase detection currents I _γ and I _{δ in the} coordinate system (hereinafter collectively referred to as “two-phase detection currents I _γδ ”). These are supplied to the current deviation calculation unit 32. For the coordinate conversion in the UVW / γδ conversion unit 36, the control angle θ _C calculated by the control angle calculation unit 26 is used.

The PI control unit 33 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 32 to thereby provide a two-phase command voltage V _γδ ^* (γ-axis command voltage V _γ ^* and δ-axis command to be applied to the motor 3. Voltage V _δ ^* ). This two-phase command voltage V _γδ ^* is _supplied to the γδ / UVW conversion unit 34.
The γδ / UVW conversion unit 34 generates a three-phase instruction voltage V _UVW ^* by performing a coordinate conversion operation on the two-phase instruction voltage V _γδ ^* . The three-phase command voltage V _UVW ^* includes a U-phase command voltage V _U ^* , a V-phase command voltage V _V ^*, and a W-phase command voltage V _W ^* . The three-phase instruction voltage V _UVW ^* is given to the PWM control unit 35.

The PWM control unit 35 includes a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM having a duty corresponding to the U-phase instruction voltage V _U ^* , the V-phase instruction voltage V _V ^*, and the W-phase instruction voltage V _W ^* , respectively. A control signal is generated and supplied to the drive circuit 12.
The drive circuit 12 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 35, so that a voltage corresponding to the three-phase instruction voltage V _UVW ^* becomes a stator winding 51, 52 for each phase of the motor 3. , 53 is applied.

The current deviation calculation unit 32 and the PI control unit 33 constitute a current feedback control unit. By the function of this current feedback control means, the motor current flowing through the motor 3 is controlled so as to approach the two-phase command current value I _γδ ^* set by the command current value generation unit 30.
FIG. 3 is a control block diagram of the electric power steering apparatus. However, in order to simplify the description, the functions of the addition angle limiter 24 and the addition angle changing unit 25 are omitted.

Command steering torque T ^* and the deviation (torque deviation) of the detected steering torque T PI control for the [Delta] T (K _P is a proportionality coefficient, K _I is an integration coefficient, 1 / s is an integration operator.) By the addition angle α Is generated. It is obtained by adding the addition the addition angle alpha control angle theta previous value of _{C θ C (n-1)} , the current value of the control angle _{θ C θ C (n) =} θ C (n-1) + α is Desired. At this time, the deviation between the control angle θ _C and the actual rotor angle θ _M of the rotor 50 is the load angle θ _L = θ _C −θ _M.

Accordingly, when the γ-axis current I _γ is supplied according to the γ-axis command current value I _γ ^* to the γ-axis (virtual axis) of the γδ coordinate system (virtual rotation coordinate system) according to the control angle θ _C , the q-axis current I _q = I _γ sinθ _L This q-axis current I _q contributes to the torque generated by the rotor 50. That is, the value obtained by multiplying the torque constant _{K T} of the motor 3 to the q-axis current _{I q (= I γ sinθ L} ) is, as the assist torque _{T A (= K T · I} γ sinθ L), via a speed reduction mechanism 7 And transmitted to the steering mechanism 2. _A value obtained by subtracting the assist torque TA from the load torque _TL from the steering mechanism 2 is the steering torque T that the driver should apply to the steering wheel 10. As the steering torque T is fed back, the system operates so as to guide the steering torque T to the command steering torque T ^* . That is, in order to make the detected steering torque T coincide with the command steering torque T ^* , the addition angle α is obtained, and the control angle θ _C is controlled accordingly.

In this way, while a current is passed through the γ axis, which is a virtual axis for control, the control angle θ _C is updated with the addition angle α obtained according to the deviation ΔT between the command steering torque T ^* and the detected steering torque T. by going, the load angle theta _L is changed, the torque corresponding to the load angle theta _L is adapted to generate from the motor 3. As a result, a torque corresponding to the command steering torque T ^* set based on the steering angle and the vehicle speed can be generated from the motor 3, so that an appropriate steering assist force corresponding to the steering angle and the vehicle speed can be applied to the steering mechanism 2. Can be given. That is, the steering assist control is executed such that the steering torque increases as the absolute value of the steering angle increases, and the steering torque decreases as the vehicle speed increases.

In this way, an electric power steering apparatus that can appropriately control the motor 3 without using a rotation angle sensor and perform appropriate steering assistance can be realized. Thereby, a structure can be simplified and cost reduction can be aimed at.
FIG. 7 is a flowchart for explaining the operation of the addition angle limiter 24. The addition angle limiter 24 compares the addition angle α obtained by the PI control unit 23 with the upper limit value UL (step S1), and when the addition angle α exceeds the upper limit value UL (step S1: YES), The upper limit value UL is substituted for the addition angle α (step S2). Therefore, the upper limit value UL (= + ω _max ) is added to the control angle θ _C.

If the addition angle α obtained by the PI control unit 23 is equal to or smaller than the upper limit value UL (step S1: NO), the addition angle limiter 24 further compares the addition angle α with the lower limit value LL (step S3). If the addition angle α is less than the lower limit value (step S3: YES), the lower limit value LL is substituted for the addition angle α (step S4). Therefore, the lower limit LL (= −ω _max ) is added to the control angle θ _C.

The addition angle α obtained or lower than the lower limit LL or the upper limit UL by the PI control unit 23: if (step S3 NO), the addition angle α is used as is added to the control angle theta _C.
In this way, the addition angle α can be limited between the upper limit value UL and the lower limit value LL, so that the control can be stabilized. More specifically, even if a control unstable state (a state where the assist force is unstable) occurs when the current is insufficient or the control is started, the transition from this state to the stable control state can be promoted.

  FIG. 8 is a flowchart showing the procedure of the addition angle changing process executed by the addition angle changing unit 25. The addition angle changing unit 25 determines whether or not the absolute value of the steering angle given from the motor load calculating unit 27 is equal to or greater than a predetermined threshold A (A> 0) (step S11). This threshold A is set to the absolute value (for example, 400 deg) of the steering angle corresponding to the load torque that is smaller than the maximum assist torque that can be output by the motor 3 by a predetermined amount. As described above, the load torque increases as the steering angle absolute value increases. When the absolute value of the steering angle is less than the threshold value A (step S11: N0), the addition angle changing unit 25 does not change the addition angle α, and the addition angle α after the limiting process by the addition angle limiter 24 is performed. Are output as they are (step S12). Therefore, the addition angle α after the limiting process by the addition angle limiter 24 is given to the control angle calculation unit 26. In normal times, the addition angle α after the limit processing by the addition angle limiter 24 is supplied to the control angle calculation unit 26 as it is.

  If the steering angle absolute value is greater than or equal to the threshold value A in step S11 (step S11: YES), the addition angle changing unit 25 changes the addition angle α after the limiting process by the addition angle limiter 24 to zero. (Step S13). Therefore, the addition angle α given to the control angle calculation unit 26 is zero. Thereafter, the addition angle changing unit 25 determines whether or not the absolute value of the detected steering torque T has decreased (step S14). Specifically, the addition angle changing unit 25 uses the absolute value | T (n) | of the steering torque detected last time from the absolute value | T (n) | of the steering torque detected this time by the torque sensor 1. It is determined whether or not the deviation (| T (n) | − | T (n−1) |) obtained by subtracting the value is equal to or smaller than a predetermined value C smaller than zero.

  When the absolute value of the detected steering torque T has not decreased (step S14: NO), that is, when the deviation (| T (n) | − | T (n−1) |) is larger than the predetermined value C. Returns to step S13. That is, if the absolute value of the detected steering torque T does not decrease after the addition angle α is changed to zero in step S13, the processes in steps S13 and S14 are repeated. For this reason, the state where the addition angle α is zero is maintained.

  When the detected steering torque T decreases (step S14: YES), that is, when the deviation (| T (n) | − | T (n−1) |) becomes equal to or smaller than a predetermined value C, the addition angle changing unit 25 The state where the addition angle α is zero is canceled, and the addition angle α after the limit processing by the addition angle limiter 24 is output as it is (step S12). As a result, the addition angle α after the limit processing by the addition angle limiter 24 is given to the control angle calculation unit 26. That is, the normal state is restored.

The load torque of the motor 3 increases as the absolute value of the steering angle increases. When the load torque becomes larger than the maximum assist torque that can be output by the motor 3, the appropriate value of the load angle does not exist, and therefore torque control becomes impossible and appropriate assist torque cannot be generated. In this embodiment, when the absolute value of the detected steering angle becomes greater than or equal to a threshold value A (for example, 400 deg) (step S11: YES), the addition angle α is changed to zero and the state is maintained (steps S13 and S14). ). When the addition angle α is zero, the control angle theta _C is not changed, the motor 3 is locked, the driver will not cut the steering wheel 10 more. As a result, it is possible to avoid the load torque from becoming larger than the maximum assist torque that the motor 3 can output.

  Thereafter, for example, when the driver gives up turning the steering wheel 10 further and loosens the steering force applied to the steering wheel 10, the absolute value of the detected steering torque T decreases. When the absolute value of the detected steering torque T decreases, YES is returned in step S14, and the normal state is restored. That is, the addition angle α after the limiting process by the addition angle limiter 24 is given to the control angle calculation unit 26. Thereby, the locked state of the motor 3 is released. In this way, the operable range of the steering wheel 10 is limited to a steering angle range in which the load torque of the motor 3 is not excessive.

  In the above embodiment, when the steering angle is equal to or greater than the threshold value A, the control angle is prevented from changing by setting the addition angle α given to the control angle calculation unit 26 to zero. The control angle may be directly limited so that the control angle does not change when the threshold value A is exceeded. Specifically, as shown by a broken line in FIG. 1, a control angle limiting unit 28 is provided instead of the addition angle changing unit 25. The control angle restriction unit 28 is provided at the subsequent stage of the control angle calculation unit 26. The absolute value of the steering angle detected by the steering angle sensor 4 is given to the control angle limiting unit 28 via the motor load calculation unit 28. Further, a steering torque T detected by the torque sensor 1 is given to the control angle limiter 28.

Control angle limiting unit 28, based on the detected steering torque T provided from the steering angle absolute value and the torque sensor 1 applied from the motor load calculating section 27, limiting the control angle theta _C calculated by the control angle calculation unit 26 To do. Specifically, the control angle restriction unit 28 does not change the control angle θ _C calculated by the control angle calculation unit 26 in a normal state, and does not change the coordinate conversion unit (γδ / UVW conversion unit 34 and UVW / to the γδ converter 36). When the absolute value steering angle exceeds a predetermined threshold, i.e., when the load torque exceeds a predetermined value, the control angle limiting unit 28 is not changing the control angle theta _C. For example, the control angle limiting unit 28 fixes the control angle theta _C to give the coordinate conversion unit 34, the value of the control angle theta _C gave the coordinate conversion unit 34, 36 the previous computation cycle. Thereafter, the control angle limiter 28 monitors the detected steering torque T of the torque sensor 1. When the absolute value of the detected steering torque T is decreased, the control angle limiting unit 28, a control angle theta _C to release the state to a constant value, revert to normal.

FIG. 9 is a flowchart illustrating a procedure of processing (control angle limiting processing) executed by the control angle limiting unit 28. The control angle limiting unit 28 determines whether or not the steering angle absolute value given from the motor load calculation unit 27 is equal to or greater than a predetermined threshold value A (step S21). This threshold value is set to an absolute value of the steering angle (for example, 400 deg) corresponding to a load torque that is smaller than the maximum assist torque that can be output by the motor 3 by a predetermined amount. If the absolute value steering angle is less than the threshold value A (step S21: N0), the control angle limiting unit 28, without limiting the control angle theta _C, calculated by the control angle calculation unit 26 in the calculation cycle The control angle θ _C (n) is output as it is (step S22). That is, the control angle θ _C (n) calculated by the control angle calculation unit 26 in the current calculation cycle is given to the coordinate conversion units 34 and 36. In normal times, the control angle θ _C (n) calculated by the control angle calculation unit 26 is supplied to the coordinate conversion units 34 and 36 as it is.

If the absolute value of the steering angle is greater than or equal to the threshold value A in step S21 (step S21: YES), the control angle limiter 28 sets the current value θ _C (the control angle to be output in the current calculation cycle. n) is replaced with the previous value θ _C (n−1) which is the previous output value (step S23). As a result, the control angle θ _C output from the control angle limiter 28 does not change. That is, the control angle θ _C given to the coordinate conversion units 34 and 36 is fixed to a value immediately before the steering angle absolute value becomes equal to or greater than the threshold value A.

Thereafter, the control angle limiter 28 determines whether or not the absolute value of the detected steering torque T has decreased (step S24). As a specific determination method, the method described in step S14 in FIG. 8 can be used. If the absolute value of the detected steering torque T has not decreased (step S24: NO), the process returns to step S23. That is, after the control angle theta _C is fixed at the step S23, when the absolute value of the detected steering torque T is not reduced, the processing of step S23 and step S24 are repeated.

When the detected steering torque T is reduced (step S24: YES), the control angle limiting unit 28, the control angle theta _C releases the state of being fixed to a constant value, the control angle theta _C calculated by the control angle calculation unit 26 (N) is output as it is (step S22). As a result, the control angle θ _C (n) calculated by the control angle calculation unit 26 is given to the coordinate conversion units 34 and 36. That is, the normal state is restored.

If the absolute value of the detected steering angle is the threshold value A (e.g., 400 deg) or more (step S21: YES), because the control angle theta _C is fixed to a constant value, the control angle theta _C does not change (step S23, S24). When the control angle θ _C does not change, the motor 3 is locked, and the driver cannot turn off the steering wheel 10 any more. As a result, it is possible to avoid the load torque from becoming larger than the maximum assist torque that the motor 3 can output.

Thereafter, for example, when the driver gives up turning the steering wheel 10 to the steering angle or more and loosens the steering force applied to the steering wheel 10, the absolute value of the detected steering torque T decreases. When the absolute value of the detected steering torque T decreases, the result in step S24 is YES, and the normal state is restored. That is, the control angle θ _C (n) calculated by the control angle calculation unit 26 is given to the coordinate conversion units 34 and 36.

FIG. 10 is a block diagram for explaining the configuration of an electric power steering apparatus according to another embodiment of the present invention. 10, portions corresponding to the respective portions in FIG. 1 are denoted by the same reference numerals as those in FIG.
In this embodiment, the addition angle changing unit 25 and the control angle limiting unit 28 shown in FIG. 1 are not provided. In this embodiment, an instruction current value change unit 31 that changes an instruction current value generated by the instruction current value generation unit 30 is provided as a function processing unit of the microcomputer 11.

The command current value changing unit 31 is given the absolute value of the steering angle detected by the steering angle sensor 4 as a value corresponding to the motor load (load torque) via the motor load calculating unit 27. The command current value change unit 31 changes the command current value generated by the command current value generation unit 30 based on the steering angle absolute value given from the motor load calculation unit 27. In this embodiment, the command current value changing unit 31 changes the γ-axis command current value I _γ ^* .

Specifically, the command current value changing unit 31 generates the command current value generating unit 30 when the absolute value of the steering angle is less than a predetermined threshold value, that is, when the load torque is less than the predetermined value. The γ-axis command current value I _γ ^* to be performed is not changed and is supplied to the current deviation calculation unit 32 as it is. On the other hand, when the steering angle absolute value is equal to or greater than the predetermined threshold value, that is, when the load torque becomes equal to or greater than the predetermined value, the command current value changing unit 31 generates γ generated by the command current value generating unit 30. The shaft command current value I _γ ^* is changed to zero. The changed γ-axis command current value I _γ ^* is given to the current deviation calculation unit 32.

FIG. 11 is a flowchart showing the procedure of the instruction current value changing process executed by the instruction current value changing unit 31. The command current value changing unit 31 determines whether or not the steering angle absolute value given from the motor load calculating unit 27 is equal to or greater than a predetermined threshold value A (step S31). This threshold value is set to an absolute value of the steering angle (for example, 400 deg) corresponding to a load torque smaller than the maximum assist torque that can be output by the motor 3. When the steering angle absolute value is less than the threshold value A (step S31: N0), the command current value changing unit 31 does not change the command current value I _γ ^* and the command current value generating unit 30 generates the command current value. The γ-axis command current value I _γ ^* to be output is output as it is (step S32). Therefore, the γ-axis command current value I _γ ^* generated by the command current value generation unit 30 is given to the current deviation calculation unit 32.

In step S31, when the steering angle absolute value is equal to or greater than the threshold value A (step S31: YES), the command current value changing unit 31 generates the γ-axis command current value I generated by the command current value generating unit 30. _γ ^* is changed to zero (step S33). Therefore, the γ-axis command current value I _γ ^* given to the current deviation calculation unit 32 is zero. As a result, the steering assist force (assist torque) is stopped. Thereafter, when the steering angle absolute value becomes less than the threshold value A, the command current value changing unit 31 outputs the γ-axis command current value I _γ ^* generated by the command current value generating unit 30 as it is (step S31). , S32).

The load torque of the motor 3 increases as the steering angle increases. When the load torque becomes larger than the maximum assist torque that can be output by the motor 3, the appropriate value of the load angle does not exist, so that the torque control becomes impossible and the appropriate assist torque cannot be generated. In this embodiment, when the absolute value of the detected steering angle becomes greater than or equal to a threshold value A (for example, 400 deg) (step S31: YES), the γ-axis command current value I _γ ^* is changed to zero (step S33). When the γ-axis command current value I _γ ^* is set to zero, the steering assist operation is stopped and a so-called manual steer state is established, so that it is possible to avoid a torque control disabled state.

  As mentioned above, although several embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the motor load calculation unit 27 estimates the motor load (load torque) from the steering angle detected by the steering angle sensor 4, but the steering wheel that is steered by the steering mechanism 2. The motor load may be estimated from the turning angle. The steering angle of the steering wheel can be obtained by multiplying the steering angle detected by the steering angle sensor 4 by the gear ratio, or can be directly detected by detecting the displacement of the rack shaft, for example. it can. Further, as the motor load calculation unit, a unit for measuring the motor load (motor load measuring unit) may be used in addition to the unit for estimating the motor load (motor load estimating unit) as described above. As the motor load measuring means, for example, an axial force sensor for detecting a force acting on the rack shaft, a tire force sensor for detecting a stress acting on the tire, or the like can be used.

Furthermore, in the above-described embodiment, the addition angle α is obtained by the PI control unit 23. However, instead of the PI control unit 23, the addition angle α is obtained using a PID (proportional / integral / derivative) operation unit. You can also
In the above-described embodiment, the configuration in which the motor 3 is driven exclusively by sensorless control without the rotation angle sensor has been described. However, the rotation angle sensor such as a resolver is provided, and when the rotation angle sensor fails, as described above. It is good also as a structure which performs a sensorless control. Thereby, since the drive of the motor 3 can be continued even when the rotation angle sensor fails, the steering assist can be continued.

In this case, when the rotation angle sensor is used, the command current value generation unit 30 may generate the δ-axis command current value I _δ ^* according to a predetermined assist characteristic according to the steering torque and the vehicle speed.
Further, in the above-described embodiment, the example in which the present invention is applied to the electric power steering apparatus has been described. However, the present invention is not limited to the motor control for the electric pump type hydraulic power steering apparatus or the power steering apparatus. It can be used for control of a brushless motor provided in a steer-by-wire (SBW) system, a variable gear ratio (VGR) steering system and other vehicle steering devices. Of course, the motor control device of the present invention can be applied not only to the vehicle steering device but also to control a motor for other purposes.

  In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 3 ... Motor, 5 ... Motor control apparatus, 10 ... Steering wheel, 11 ... Microcomputer, 23 ... PI control part, 26 ... Control angle calculating part, 50 ... Rotor, 51, 52, 53 ... Stator winding Wire, 55 ... stator

Claims (2)

A motor control device for controlling a motor including a rotor and a stator facing the rotor,
Current driving means for driving the motor with an axial current value of a rotating coordinate system according to a control angle that is a control rotation angle;
Control angle calculation means for obtaining the current value of the control angle by adding the addition angle to the previous value of the control angle for each predetermined calculation cycle;
Motor load calculating means for measuring or estimating the load of the motor;
A motor control apparatus comprising: a limiting unit that limits the control angle, the addition angle, or the shaft current value when a motor load measured or estimated by the motor load calculating unit is equal to or greater than a predetermined value. A motor for applying a driving force to the steering mechanism of the vehicle;
A motor control device according to claim 1 for controlling the motor;
Vehicle steering, wherein the motor load calculating means estimates the motor load based on a steering angle of a steering member operated for steering the vehicle or a steering angle of a wheel of the vehicle. apparatus.

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