JP2020179832A - Steering control device - Google Patents

Abstract

To provide a steering control device configured to be able to suppress self-excited vibration from occurring in processing based on a normative model.SOLUTION: A pinion angle command value θp* is calculated in angle command value calculation processing M20 in which axial force Taf is input. A motor is operated based on an angle-side adjustment quantity Tt*, a value determined by subtracting a decrease correction quantity ΔTt* from an angle operation quantity Tt1* that is an operation quantity at which control by which a pinion angle θp is fed back to the pinion angle command value θp* is performed. Axial force Taf is set to a value determined by subtracting the decrease correction quantity ΔTt from the sum of a steering operation quantity Ts* as an operation quantity at which control by which the steering torque Th is fed back to target steering torque Th* by the torque feedback processing and the steering torque Th. When the decrease correction quantity ΔTt is equal to the angle operation quantity Tt1*, elastic modulus K and viscous modulus C in normative model calculation processing M30 are changed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a steering control device for which a steering actuator having a built-in electric motor and steering a steering wheel is operated.

For example, Patent Document 1 describes rolling based on the operation amount of feedback control based on the difference between the target steering torque and the actual steering torque and the operation amount of feedback control based on the difference between the target steering angle and the steering angle. A device for operating an electric motor built in a steering actuator that steers a steering wheel is described. Here, the target steering angle is calculated based on the normative model.

Japanese Unexamined Patent Publication No. 2006-175940

By the way, if the difference between the steering angle and the target steering angle becomes excessively large, the feedback control becomes unstable. Therefore, the inventor stops the feedback control when the difference becomes excessively large. I considered that. However, if the operation amount of the feedback control is not sufficiently reflected in the operation of the electric motor, such as when the feedback control is stopped, self-excited vibration may occur in the processing based on the normative model.

Hereinafter, means for solving the above problems and their actions and effects will be described.
1. 1. The operation amount of the electric motor for steering the steering wheel in order to feedback control the steering torque input by the driver to the target steering torque, targeting the steering actuator having a built-in electric motor and steering the steering wheel. The steering operation amount calculation process for calculating the steering operation amount, which is the operation amount that can be converted into the torque required for the electric motor, and the conversion that can be converted into the steering angle of the steering wheel according to the steering operation amount. The angle command value calculation process for calculating the angle command value, which is the command value for the possible angle, and the operation amount for feedback-controlling the convertible angle to the angle command value, which can be converted into the torque required for the electric motor. The torque of the electric motor is controlled so as to control the torque of the electric motor according to at least one of the two operation amounts of the steering operation amount and the angle operation amount and the angle operation amount calculation process for calculating the angle operation amount which is an amount. The operation process for operating the drive circuit and the value obtained by subtracting the angle operation amount reflected in the operation process from the angle operation amount calculated by the angle operation amount calculation process are adjusted, and the adjusted angle operation amount is adjusted. Steering control for executing the adjustment process of inputting to the operation process and the change process of changing the output relationship of the angle command value calculation process to the input of the angle command value calculation process according to the subtracted value. It is a device.

In the above configuration, by changing the output relationship to the input of the angle command value calculation process according to the subtracted value, the output relationship to the input of the angle command value calculation process is changed according to the magnitude of the subtracted value. The relationship can be changed to an appropriate one in order to improve the stability of the angle command value calculation process.

2. When the magnitude of the value obtained by subtracting the angle manipulation amount reflected in the operation processing from the angle manipulation amount calculated by the angle manipulation amount calculation processing is large, the angle command value calculation processing is the angle more than when it is small. The steering control device according to 1 above, which executes a correction process for correcting the size of an input when calculating a command value.

The angle manipulated variable calculated by the angle manipulated variable calculation process is an appropriate manipulated variable for setting the angle command value. Therefore, if the angle manipulation amount input for the operation processing is insufficient for the angle manipulation amount calculated by the angle manipulation amount calculation processing, the convertible angle may deviate significantly from the angle command value. If the convertible angle deviates significantly from the angle command value, the absolute value of the angle manipulated variable calculated by the angle manipulated variable calculation process becomes excessively large, and deviates from an appropriate value for making the convertible angle the angle command value. Therefore, in the above configuration, the angle command value can be brought closer to the convertible angle by correcting the input of the angle command value calculation process according to the subtracted value, and the absolute value of the angle manipulation amount becomes excessively large. Can be suppressed.

3. 3. The operation process includes a first operation process for operating the drive circuit in order to control the torque of the electric motor at least according to the angle operation amount, and the electric motor according to the steering operation amount regardless of the angle operation amount. The change process includes the second operation process of operating the drive circuit to control the torque of the above, and the change process is the output of the output with respect to the input at the time of executing the first operation process and at the time of executing the second operation process. The steering control device according to 1 or 2 above, which includes a process of changing the relationship.

The angle command value calculation process that can ensure stability for the first operation process is the angle operation amount when the second operation process that controls the torque of the motor according to the steering operation amount is executed regardless of the angle operation amount. Is not reflected, so stability is likely to be impaired. Therefore, in the above configuration, by changing the relationship between the output and the input of the angle calculation process between the first operation process and the second operation process, in each of the two processes of the first operation process and the second operation process, It is possible to ensure the stability of the angle command value calculation process.

4. The steering control device according to 1 or 2 above, wherein the operation process includes a process of controlling the torque of the electric motor according to the angle operation amount regardless of the steering operation amount.
5. The angle command value calculation process includes a process of calculating an elastic force that is a force on the side that reduces the magnitude of the steering angle in proportion to the magnitude of the angle command value, and the elastic force of the steering operation amount. The change process includes a process of calculating the angle command value according to the value reduced by, and the change process changes the proportional coefficient of the elastic force with respect to the magnitude of the steering angle according to the subtracted value. The steering control device according to any one of 1 to 4 above, which includes a process of performing.

In the above configuration, since the angle command value calculation process calculates the angle command value using the elastic force, the stability of the angle command value calculation process can be improved by a simple process by changing the proportional coefficient of the elastic force. The relationship between the output and the input can be changed so that it can be enhanced.

6. The angle command value calculation process includes a process of calculating a viscous force, which is a force on the side that reduces the magnitude of the steering angle in proportion to the magnitude of the change speed of the angle command value, and the steering operation amount. The change process includes a process of calculating the angle command value according to the value reduced by the viscous force, and the change process is a proportional coefficient of the viscous force with respect to the magnitude of the change rate according to the subtracted value. The steering control device according to any one of 1 to 5 above, which includes a process of changing the above.

In the above configuration, since the angle command value calculation process calculates the angle command value using the viscous force, the stability of the angle command value calculation process can be improved by a simple process by changing the proportional coefficient of the viscous force. The relationship between the output and the input can be changed so that it can be enhanced.

7. One of the above 1 to 6 for executing the target steering torque calculation process for calculating the target steering torque based on the sum of the amounts obtained by converting the steering operation amount and the steering torque into the force acting on the same object. The steering control device according to the above.

Since the steering operation amount can be converted into the torque required for the electric motor, the force applied from the vehicle side to steer the steering wheel is determined by the steering operation amount and the steering torque, and this force is the lateral force. Can be converted to. On the other hand, the target steering torque required to improve the steering feeling by the driver tends to be determined according to the lateral force. Therefore, in the above configuration, by determining the target steering torque based on the above sum, the design of the target steering torque calculation process becomes easy.

The figure which shows the electric power steering apparatus which concerns on 1st Embodiment. The block diagram which shows the process executed by the steering control device which concerns on the same embodiment. The flow chart which shows the procedure of the restriction processing concerning this embodiment. The figure which shows the electric power steering apparatus which concerns on 2nd Embodiment. The block diagram which shows the process executed by the steering control device which concerns on the same embodiment. The flow chart which shows the procedure of the restriction processing concerning this embodiment. The figure for demonstrating the operation of the same embodiment.

<First Embodiment>
Hereinafter, the first embodiment of the steering control device will be described with reference to the drawings.
As shown in FIG. 1, the electric power steering device 10 includes a steering mechanism 20 that steers the steering wheel 12 based on the operation of the driver's steering wheel 22, and a steering actuator 30 that electrically steers the steering wheel 12. It has.

The steering mechanism 20 includes a steering wheel 22, a steering shaft 24 fixed to the steering wheel 22, and a rack and pinion mechanism 27. The steering shaft 24 includes a column shaft 24a connected to the steering wheel 22, an intermediate shaft 24b connected to the lower end of the column shaft 24a, and a pinion shaft 24c connected to the lower end of the intermediate shaft 24b. doing. The lower end of the pinion shaft 24c is connected to the rack shaft 26 via a rack and pinion mechanism 27. Left and right steering wheels 12 are connected to both ends of the rack shaft 26 via tie rods 28. Therefore, the rotational movement of the steering wheel 22, that is, the steering shaft 24 is a reciprocating linear motion in the axial direction (left-right direction in FIG. 1) of the rack shaft 26 via the rack and pinion mechanism 27 including the pinion shaft 24c and the rack shaft 26. Will be converted. The reciprocating linear motion is transmitted to the steering wheels 12 via the tie rods 28 connected to both ends of the rack shaft 26, so that the steering angle of the steering wheels 12 changes. The maximum value of the amount of displacement of the rack shaft 26 in the axial direction is defined by the rack housing 16.

On the other hand, the steering actuator 30 shares the rack shaft 26 with the steering mechanism 20, and also includes an electric motor 32, an inverter 33, a ball screw mechanism 34, and a belt type reduction mechanism 36. The electric motor 32 is a source of power for steering the steering wheel 12, and in the present embodiment, a three-phase surface magnet synchronous motor (SPMSM) is exemplified as the electric motor 32. The ball screw mechanism 34 is integrally attached around the rack shaft 26, and the belt type speed reduction mechanism 36 transmits the rotational force of the output shaft 32a of the electric motor 32 to the ball screw mechanism 34. The rotational force of the output shaft 32a of the electric motor 32 is converted into a force that causes the rack shaft 26 to reciprocate linearly in the axial direction via the belt type reduction mechanism 36 and the ball screw mechanism 34. The steering wheel 12 can be steered by the axial force applied to the rack shaft 26.

The steering control device 40 controls the steering wheel 12, and operates the steering actuator 30 in order to control the steering angle, which is the controlled amount thereof. The steering control device 40 has a steering torque Th, which is a torque detected by the torque sensor 50 and is input by the driver via the steering wheel 22, and a vehicle speed V, which is detected by the vehicle speed sensor 52, when controlling the control amount. Refer to the rotation angle θm of the output shaft 32a detected by the rotation angle sensor 54 and the currents iu, iv, and iwa flowing through the electric motor 32. The currents iu, iv, and iw may be detected as voltage drops in the shunt resistors provided on each leg of the inverter 33.

The steering control device 40 includes a CPU 42, a ROM 44, and peripheral circuits 46, which are connected via a communication line 48. The peripheral circuit 46 includes a circuit that generates a clock signal that defines the internal operation, a power supply circuit, a reset circuit, and the like.

FIG. 2 shows a part of the processing executed by the steering control device 40. The process shown in FIG. 2 is realized by the CPU 42 executing the program stored in the ROM 44.
The base target torque calculation process M10 calculates the base target torque Thb *, which is the base value of the target steering torque Th * that the driver should input to the steering shaft 24 via the steering wheel 22, based on the axial force Taf0 described later. It is a process. Here, the axial force Taf0 is an axial force applied to the rack shaft 26. Since the axial force Taf0 is an amount corresponding to the lateral force acting on the steering wheel 12, the lateral force can be grasped by the axial force Taf0. On the other hand, it is desirable that the torque to be input to the steering shaft 24 by the driver via the steering wheel 22 is determined according to the lateral force. Therefore, the base target torque calculation process M10 is a process of calculating the base target torque Thb * according to the lateral force grasped from the axial force Taf0.

Specifically, the base target torque calculation process M10 is a process of calculating the absolute value of the base target torque Thb * to a smaller value than when the vehicle speed V is small even if the absolute value of the axial force Taf0 is the same. Is. This is done by the CPU 42 in a state where map data having the lateral acceleration and vehicle speed V grasped from the axial force Taf0 or the axial force Taf0 as input variables and the base target torque Thb * as output variables is stored in the ROM 44 in advance. This can be achieved by performing map calculation of the base target torque Thb *. Here, the map data is a set of data of discrete values of input variables and values of output variables corresponding to the values of the input variables. In the map calculation, for example, when the value of the input variable matches any of the values of the input variable of the map data, the value of the output variable of the corresponding map data is used as the calculation result, whereas when they do not match, the map is used. The processing may be performed on the value obtained by interpolating the values of a plurality of output variables included in the data as the calculation result.

The hysteresis processing M14 calculates the hysteresis correction amount This that corrects the base target torque Thb * based on the rotation angle (pinion angle θp) of the pinion shaft 24c, which is a convertible angle that can be converted into the steering angle of the steering wheel 12. It is a process to output. Specifically, the hysteresis processing M14 identifies the turning time and the turning back time of the steering wheel 22 based on the change of the pinion angle θp and the like, and the absolute value of the target steering torque Th * at the cutting time is compared with that at the turning back time. A process of calculating the hysteresis correction amount Thys so as to be larger is included. Specifically, the hysteresis process M14 includes a process of variably setting the hysteresis correction amount Thys according to the vehicle speed V.

The addition process M12 is a process of calculating the target steering torque Th * by adding the hysteresis correction amount Thys to the base target torque Thb *.
The steering operation amount calculation process M16 is a process of calculating the steering operation amount Ts *, which is the operation amount for feedback-controlling the steering torque Th to the target steering torque Th *. The steering operation amount Ts * is an amount including an operation amount for feedback-controlling the steering torque Th to the target steering torque Th *, but may include a feedforward term. The amount of operation for feedback control is, for example, the magnitude of the required torque for the motor 32 when the signs of the steering torque Th and the target steering torque Th * are both positive and the steering torque Th is larger than the target steering torque Th *. It is an amount to increase (absolute value). The steering operation amount Ts * is an amount corresponding to the required torque Td for the electric motor 32 for feedback-controlling the steering torque Th to the target steering torque Th *. However, in the present embodiment, the steering operation amount Ts * is , It is an amount converted into the torque applied to the steering shaft 24.

The axial force calculation process M18 is a process of calculating the axial force Taf0 by adding the steering torque Th to the steering operation amount Ts *. Since the steering torque Th is the torque applied to the steering shaft 24, the axial force Taf0 in the present embodiment is a value obtained by converting the force applied in the axial direction of the rack shaft 26 into the torque applied to the steering shaft 24. ..

The subtraction process M20 is a process of calculating the axial force Taf by subtracting the reduction correction amount ΔTt * from the axial force Taf0.
The normative model calculation process M30 is a process of calculating the pinion angle command value θp *, which is the command value of the pinion angle θp, based on the axial force Taf. Specifically, the normative model calculation process M30 is a process of calculating the pinion angle command value θp * using the model formula expressed by the following formula (c1).

Taf = K ・ θp * ＋ C ・ θp *'+ J ・ θp *''… (c1)
The model expressed by the above equation (c1) is a model of the value indicated by the pinion angle θp when a torque equal to the axial force Taf is input to the steering shaft 24. In the above equation (c1), the viscosity coefficient C is a model of the friction of the electric power steering device 10, and the inertia coefficient J is a model of the inertia of the electric power steering device 10. The coefficient K is a model of specifications such as suspension and wheel alignment of a vehicle on which the electric power steering device 10 is mounted. This model is not a model that accurately represents the actual electric power steering device 10 or the vehicle on which the electric power steering device 10 is mounted, but is designed to make the behavior of the steering angle with respect to the input ideal. It is a normative model. In this embodiment, the steering feeling can be adjusted through the design of the normative model.

The integration process M40 is a process for calculating the integrated value Inθ of the rotation angle θm of the electric motor 32. In the present embodiment, the steering angle of the steering wheel 12 when the vehicle travels straight is set to "0", and the integrated value Inθ when the steering angle is "0" is set to "0". The conversion process M42 is a process of calculating the pinion angle θp by dividing the integrated value Inθ by the reduction ratio Km from the steering shaft 24 to the electric motor 32. The pinion angle θp indicates that the direction is straight when it is “0”, and it is the turning angle on the right turning side or the turning angle on the left turning side depending on whether it is positive or negative. Indicates whether it is.

The angle manipulated variable calculation process M50 is a process of calculating the angle manipulated variable Tt1 *, which is the manipulated variable for feedback-controlling the pinion angle θp to the pinion angle command value θp *. The angle manipulation amount Tt1 * is an amount corresponding to the required torque Td for the electric motor 32 for feedback-controlling the pinion angle θp to the pinion angle command value θp *, but in the present embodiment, it is a torque applied to the steering shaft 24. It is the converted amount.

In addition to the angle manipulated variable Tt1 * and the steering torque Th, the angle manipulated variable calculation process M50 includes a disturbance observer M52 that estimates a torque affecting the pinion angle θp as a disturbance torque and uses this as the estimated disturbance torque Tlde. In the present embodiment, the estimated disturbance torque Tlde is converted into the torque applied to the steering shaft 24.

The disturbance observer M52 uses a three-row, one-column matrix L that defines the inertial coefficient Jp, the estimated value θpe of the pinion angle θp, the angle manipulation amount Tt0 *, and the observer gains l1, l2, and l3 in the following equation (c2). The estimated disturbance torque Tlde and the estimated value θpe are calculated. The inertia coefficient Jp is a model of the inertia of the electric power steering device 10, and is a value that expresses the inertia of the actual electric power steering device 10 with high accuracy as compared with the inertia coefficient J. ..

The differential calculation process M54 is a process of calculating the pinion angular velocity command value by the differential calculation of the pinion angular velocity command value θp *.

The feedback term calculation process M56 is a differential term according to the difference between the pinion angle command value θp * and the estimated value θpe, and the differential value according to the difference between the differential value of the pinion angle command value θp * and the differential value of the estimated value θpe. This is a process of calculating the feedback manipulated amount Ttfb, which is the sum of the terms.

The second-order differential process M58 is a process for calculating the second-order time derivative value of the pinion angle command value θp *. The feedforward term calculation process M60 is a process of calculating the feedforward manipulated variable Ttff by multiplying the output value of the second-order differential process M58 by the inertia coefficient Jp. The two-degree-of-freedom manipulated variable calculation process M62 is a process of subtracting the estimated disturbance torque Tlde from the sum of the feedback manipulated variable Ttfb and the feedforward manipulated variable Ttff to calculate the angle manipulated variable Tt0 *.

The steering torque compensation process M66 is a process of subtracting the steering torque Th from the angle manipulated variable Tt0 * to calculate the angle manipulated variable Tt1 * which is the output of the angle manipulated variable calculation process M50.
The limiting process M70 is a process of calculating the reduction correction amount ΔTt * based on the angle manipulation amount Tt1 *, and a process of changing the parameters of the norm model calculation process M30 according to the reduction correction amount ΔTt *.

The subtraction process M72 is a process of calculating the angle manipulation amount Tt * by subtracting the reduction correction amount ΔTt * from the angle manipulation amount Tt1 *.
The addition process M74 is a process of adding the steering operation amount Ts * and the angle operation amount Tt * to calculate the required torque Td for the electric motor 32. The required torque Td is the torque required to be generated by the electric motor 32 converted to the torque of the steering shaft 24.

The conversion process M76 is a process of dividing the required torque Td by the reduction ratio Km to convert the required torque Td into the torque command value Tm *, which is the command value of the torque for the electric motor 32.

The operation signal generation process M78 is a process of generating and outputting the operation signal MSt of the inverter 33 for controlling the torque of the electric motor 32 to the torque command value Tm *. The operation signal MSt is actually an operation signal for each arm of each leg of the inverter 33.

FIG. 3 shows the procedure of the restriction process M70. The process shown in FIG. 3 is realized by the CPU 42 repeatedly executing the program stored in the ROM 44, for example, at a predetermined cycle. In the following, the step number of each process is represented by a number prefixed with "S".

In the series of processes shown in FIG. 3, the CPU 42 first determines whether or not the fail flag F is “1” (S10). When the fail flag F is "1", it indicates that the controllability of the electric motor 32 based on the angle manipulated variable calculation process M50 is equal to or less than a predetermined value, and when it is "0", it indicates that it is not. Shown. When the CPU 42 determines that it is "0" (S10: NO), it determines whether or not the logical sum of the following conditions (a) to (c) is true (S12).

Condition (a): The logical product of the condition that the pinion angle θp is larger than the predetermined value θphthH and the condition that the value obtained by subtracting the pinion angle θp from the pinion angle command value θp * is larger than the predetermined value Δθpthe is true. It is a condition to the effect that. The predetermined value θphthH is set to the pinion angle θp when the amount of axial displacement of the rack shaft 26 reaches the upper limit of the amount of axial displacement of the rack shaft 26 defined by the rack housing 16. This condition is a condition that the further displacement of the rack shaft 26 in the axial direction is restricted by the rack housing 16, and the absolute value of the pinion angle θp cannot be further increased.

Condition (a): The condition that the pinion angle θp is smaller than the value of “-1” times the predetermined value θphthH, and the value obtained by subtracting the pinion angle θp from the pinion angle command value θp * are the predetermined values Δθpthen “-1”. It is a condition that the logical product with the condition that it is smaller than the double value is true. This condition is a condition that the further displacement of the rack shaft 26 in the axial direction is restricted by the rack housing 16, and the absolute value of the pinion angle θp cannot be further increased.

Condition (c): It is a condition that the absolute value of the difference between the pinion angle command value θp * and the pinion angle θp is equal to or more than the predetermined value ΔθphthH. The predetermined value ΔθphthH is the maximum value that is expected to occur as the absolute value of the difference between the pinion angle command value θp * and the pinion angle θp when the angle control by the angle manipulation amount calculation process M50 is normally performed. Is also set to a large value.

When the CPU 42 determines that the logical sum is true (S12: YES), the CPU 42 determines that the controllability of the electric motor 32 based on the angle manipulation amount calculation process M50 is equal to or less than a predetermined value, and sets the fail flag F to "1". Is substituted (S14). Then, the CPU 42 substitutes the value obtained by adding a predetermined amount Δp smaller than “1” to the gain α and the smaller of “1” to the gain α (S16). This process is a process of gradually increasing the gain α from “0” to “1”. The initial value of the gain α is “0”.

On the other hand, when the CPU 42 determines that the fail flag F is "1" (S10: YES), the CPU 42 determines whether or not the logical product of the following condition (d) and condition (e) is true (S18). ).

Condition (d): It is a condition that the magnitude (absolute value) of the pinion angle θp is equal to or less than the predetermined value θpsL. The predetermined value θphthL is a value smaller than the predetermined value θphthH.
Condition (e): The condition that the absolute value of the difference between the pinion angle command value θp * and the pinion angle θp is equal to or less than the predetermined value ΔθphthL. The predetermined value ΔθphthL is a value smaller than the predetermined value ΔθphthH, and occurs as an absolute value of the difference between the pinion angle command value θp * and the pinion angle θp when the angle control by the angle manipulation amount calculation process M50 is normally performed. Is set to the expected value.

When the CPU 42 determines that the logical product is false (S18: NO), the CPU 42 shifts to the process of S16. On the other hand, when the CPU 42 determines that the logical product is true (S18: YES), the CPU 42 fails, assuming that the controllability of the electric motor 32 based on the angle manipulation amount calculation process M50 has returned from the predetermined state or less. Substitute "0" for the flag F (S20). When the processing of S20 is completed or when a negative determination is made in the processing of S12, the CPU 42 determines the larger of the value obtained by reducing the gain α by a predetermined amount Δm smaller than “1” and “0”. Substitute for gain α (S22). This process is a process of gradually reducing the gain α from “1” to “0”.

When the processing of S16 and S22 is completed, the CPU 42 substitutes the value obtained by multiplying the angle manipulation amount Tt0 * by the gain α into the reduction correction amount ΔTt * (S24). Next, the CPU 42 determines whether or not the gain α is “1” (S26). Then, when it is determined that the value is not "1" (S26: NO), the normal value K0 is substituted for the elastic modulus K and the normal value C0 is substituted for the viscosity coefficient C (S28). The normal values K0 and C0 are adapted to values that stabilize the normative model calculation process M30 when the angle manipulated variable calculation process M50 is reflected in the control of the steering angle. On the other hand, when the CPU 42 determines that the value is "1" (S26: YES), the CPU 42 substitutes the change value K1 into the elastic modulus K used for calculating the pinion angle command value θp * by the norm model calculation process M30 and the viscosity. The change value C1 is substituted into the coefficient C (S30). The changed values K1 and C1 are adapted to values that stabilize the normative model calculation process M30 when the angle manipulated variable calculation process M50 is not reflected in the control of the steering angle.

When the processes of S28 and S30 are completed, the CPU 42 temporarily ends the series of processes shown in FIG.
Here, the operation and effect of this embodiment will be described.

The CPU 42 calculates the pinion angle command value θp * according to the axial force Taf0, which is the sum of the steering operation amount Ts *, which is the operation amount for feedback-controlling the steering torque Th to the target steering torque Th *, and the steering torque Th. To do. Then, the angle manipulated variable calculation process M50 calculates the angle manipulated variable Tt1 *, which is the manipulated variable for feedback-controlling the pinion angle θp to the pinion angle command value θp *. Then, the CPU 42 operates the electric motor 32 according to the sum of the steering operation amount Ts * and the angle operation amount Tt * corresponding to the angle operation amount Tt1 *.

Here, when the CPU 42 determines that the controllability of the electric motor 32 based on the angle manipulation amount calculation process M50 is equal to or less than a predetermined value, the reduction correction amount ΔTt * is set to the angle manipulation amount by setting the gain α to “1”. Let it be Tt1 *. As a result, the angle manipulated variable Tt * that is the input of the addition process M74 can be set to "0". Therefore, when the controllability of the motor 32 based on the angle manipulated variable calculation process M50 is equal to or less than a predetermined value, the angle manipulated variable The torque control of the electric motor 32 by the calculation process M50 can be invalidated. As a result, the torque of the electric motor 32 is controlled only according to the steering operation amount Ts *, which is the operation amount for feedback-controlling the steering torque Th to the target steering torque Th *.

Further, when the angular manipulated variable Tt * becomes "0", the CPU 42 substitutes the change value K1 for the elastic modulus K and substitutes the change value C1 for the viscosity coefficient C. Here, the changed values K1 and C1 are adapted to values that can ensure the stability of the normative model calculation process M30 when the angle operation amount calculation process M50 is not reflected in the operation of the electric motor 32. Therefore, when the angle manipulation amount Tt * is “0”, it is possible to prevent the absolute value of the difference between the pinion angle command value θp * and the pinion angle θp from becoming large. Therefore, the control of the steering angle by the angle manipulated variable calculation process M50 can be smoothly restarted. On the other hand, when the normal values K0 and C0 are used even when the angle manipulated variable Tt * is "0", the normative model calculation process M30 is not stable and the pinion angle command value θp * vibrates. Therefore, the absolute value of the difference between the pinion angle command value θp * and the pinion angle θp may fluctuate greatly. In that case, it becomes difficult to restart the control of the steering angle by the angle manipulation amount calculation process M50.

According to the present embodiment described above, the effects described below can be further obtained.
(1) The CPU 42 subtracts the reduction correction amount ΔTt *, which is the value obtained by subtracting the angle manipulation amount Tt * from the angle manipulation amount Tt0 *, from the axial force Taf0, and sets the axial force Taf as the input of the normative model calculation process M30. To do. As a result, it is possible to prevent the estimated disturbance torque Tlde from becoming excessively large. That is, the angle manipulated variable Tt1 * calculated by the angle manipulated variable calculation process M50 is an appropriate manipulated variable for setting the pinion angle θp to the pinion angle command value θp *. Therefore, when the value obtained by subtracting the angle manipulated variable Tt * from the angle manipulated variable Tt1 * is not "0", the pinion angle θp deviates greatly from the pinion angle command value θp *, and thus the magnitude of the estimated disturbance torque Tlde. May become excessively large. In that case, since the angle manipulation amount Tt1 * deviates from an appropriate value for setting the pinion angle θp to the pinion angle command value θp *, when the angle manipulation amount Tt * is shifted to the angle manipulation amount Tt1 *, The controllability of the pinion angle θp may decrease.

(2) The pinion angle command value θp * was calculated by the norm model calculation process M30 based on the above equation (c1) expressing the norm model, and the pinion angle θp was controlled to the pinion angle command value θp *. As a result, the steering characteristics can be adjusted by the normative model.

(3) The target steering torque Th * was set according to the sum of the steering operation amount Ts * and the steering torque Th. Here, the target steering torque Th * required to improve the steering feeling by the driver tends to be determined according to the lateral force. On the other hand, since the sum of the steering operation amount Ts * and the steering torque Th can be converted into the lateral force of the vehicle, the target steering torque Th * can be calculated by determining the target steering torque Th * based on the above sum. Easy to design.

<Second embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

FIG. 4 shows the configuration of the electric power steering device 10 according to the present embodiment. Of the members shown in FIG. 4, the members corresponding to the members shown in FIG. 1 are designated by the same reference numerals for convenience.

In the present embodiment, the pinion shaft 24c is provided with a clutch 60 capable of interrupting the transmission of power to and from the steering wheel 22. That is, the pinion shaft 24c is connected to one side of the clutch 60, and the input shaft 24d connected to the steering wheel 22 is connected to the other side of the clutch 60. In this embodiment, the input shaft 24d and the pinion shaft 24c are referred to as a steering shaft 24.

The power of the electric motor 72 is applied to the input shaft 24d via the speed reducer 70. The voltage of the inverter 74 is applied to each terminal of the electric motor 72. The drag actuator 80 is composed of an input shaft 24d, a speed reducer 70, an electric motor 72, and an inverter 74. In the present embodiment, the steering control device 40 refers to the rotation angle (steering angle θh) of the steering wheel 22 detected by the steering angle sensor 82.

FIG. 5 shows a part of the processing executed by the steering control device 40 according to the present embodiment. The process shown in FIG. 5 is realized by the CPU 42 executing the program stored in the ROM 44. In FIG. 5, the same reference numerals are given to the processes corresponding to the processes shown in FIG. 2 for convenience.

As shown in FIG. 5, in the present embodiment, the command value of the steering angle (steering angle command value θh *) is calculated in place of the pinion angle command value θp * in the norm model calculation process M30. On the other hand, the steering angle ratio variable processing M90 adjusts the adjustment amount Δa for making the steering angle ratio variable, which is the ratio of the target value of the steering angle (pinion angle command value θp *) to the steering angle command value θh *, as the vehicle speed. This is a process of variably setting according to V. Specifically, the adjustment amount Δa is set so that the change in the steering angle with respect to the change in the steering angle is larger than when the vehicle speed V is low and high. The addition process M92 sets the pinion angle command value θp * by adding the adjustment amount Δa to the steering angle command value θh *.

The drag calculation process M94 is a process of calculating the torque command value Tr * of the electric motor 72 as an operation amount for feedback-controlling the steering angle θh to the steering angle command value θh *. The operation signal generation process M96 is a process of outputting operation signals MSs to the inverter 74 to operate the inverter 74 in order to control the torque of the electric motor 72 to the torque command value Tr *.

In this embodiment, the steering torque compensation process M66 is not provided, and the angle manipulated variable Tt1 *, which is the output of the angle manipulated variable calculation process M50, is equal to the angle manipulated variable Tt0 *. Further, in the present embodiment, the angle manipulated variable Tt1 * is the required torque Td. That is, in the present embodiment, the torque command value Tm * is calculated only from the angular manipulated variable Tt1 *.

FIG. 6 shows the procedure of the restriction process M70 according to the present embodiment. The process shown in FIG. 6 is realized by the CPU 42 repeatedly executing the program stored in the ROM 44, for example, at a predetermined cycle. The same step numbers are assigned to the processes corresponding to the processes shown in FIG. 3 in FIG. 6 for convenience.

In the series of processes shown in FIG. 6, the CPU 42 first has a condition (a) that the vehicle speed V is equal to or less than the specified speed Vth and a condition that the magnitude (absolute value) of the steering torque Th is equal to or less than the specified value Tth. It is determined whether or not the logical product of (a) and the condition (c) that the magnitude (absolute value) of the steering speed ωh is equal to or less than the specified speed ωth is true (S40). This process is a process of determining whether or not the vehicle is stopped at an intersection or the like and the driver does not operate the steering wheel 22. Here, the specified speed Vth is a value for determining whether the vehicle is stopped or almost stopped, and is a small value close to "0". Further, the specified value Tth is a value for determining that the driver is not operating the steering wheel 22, and is a value close to "0". Further, the specified speed ωth is a value for determining that the driver is not operating the steering wheel 22, and is a value close to “0”. Incidentally, the steering speed ωh is the amount of change in the steering angle θh per unit time, and is calculated by the CPU 42.

When the CPU 42 determines that the logical product is true (S40: YES), it shifts to the process of S16, while when it determines that the logical product is false (S40: NO), it shifts to the process of S22. Then, when the processes of S16 and S22 are completed, the CPU 42 executes the processes of S24 to S30 and temporarily ends the series of processes shown in FIG.

Here, the operation and effect of this embodiment will be described.
FIG. 7 shows the relationship between the steering angle θh and the torque command value Tr * for applying drag to the steering wheel 22.

As shown in FIG. 7, when the steering angle θh increases from the state where the steering angle θh is “0”, the torque command value Tr * increases along the curve d1. After that, when the driver stops the vehicle at an intersection or the like and stops the operation of the steering wheel 22 at the steering angle θh at the point P in FIG. 7, the magnitude of the steering torque Th becomes small. When the magnitude of the steering torque Th becomes smaller, the magnitude of the steering angle command value θh * becomes smaller than the magnitude of the steering angle θh, and the steering wheel 22 is returned to the neutral position side. As a result, the torque command value Tr * becomes smaller as the magnitude of the steering angle θh decreases along d2 in FIG. 7, and when the steering angle θh becomes “θa”, the torque command value Tr * becomes “”. It becomes "0". However, the pinion angle command value θp * set in response to this is not necessarily an angle that is maintained even if the torque of the electric motor 32 is “0”. For example, when the steering angle command value θh * when the steering angle θh becomes “θb” is an angle at which the pinion angle θp is maintained as it is even if the torque of the electric motor 32 is “0”, the angle operation amount Tt By *, the pinion angle θp is maintained at the pinion angle command value θp *. When the driver actually puts his hand on the steering wheel 22, the steering torque Th is not necessarily "0", and in that case, the steering angle θh is different from "θa", but in that case, Even if there is, the pinion angle command value θp * set in response to this is not necessarily an angle that is maintained even if the torque of the electric motor 32 is “0”.

Therefore, when the vehicle is stopped, the electric current may continue to flow unnecessarily through the electric motor 32. Therefore, the CPU 42 reduces the angular manipulated variable Tt * to "0" when the logical product of the above conditions (a), (b), and condition (c) is true. As a result, the torque command value Tm * can be reduced to "0". Therefore, it is possible to prevent an unnecessary current from continuing to flow in the electric motor 32.

<Correspondence>
The correspondence between the matters in the above embodiment and the matters described in the column of "Means for Solving the Problem" is as follows. In the following, the correspondence is shown for each number of the solution means described in the column of "Means for solving the problem". [1, 5, 6] The convertible angle corresponds to the pinion angle θp. The angle command value calculation process corresponds to the norm model calculation process M30 of FIG. 2, the norm model calculation process M30 of FIG. 7, the steering angle ratio variable process M90, and the addition process M92. The operation process corresponds to the addition process M74, the conversion process M76 and the operation signal generation process M78 of FIG. 2, and the conversion process M76 and the operation signal generation process M78 of FIG. The change process corresponds to the processes of S26 to S30. The drive circuit corresponds to the inverter 33. [2] The correction process corresponds to the subtraction process M20. [3] The first operation processing corresponds to the processing when the magnitude of the reduction correction amount ΔTt * is smaller than the magnitude of the angle manipulation amount Tt1 *, and the second operation processing corresponds to the processing when the magnitude of the reduction correction amount ΔTt * is smaller. It corresponds to the processing when it is equal to the magnitude of the angular manipulated variable Tt1 *. [4] Corresponds to the process of FIG. [7] The target steering torque calculation process corresponds to the base target torque calculation process M10, the addition process M12, and the hysteresis process M14.

<Other Embodiments>
In addition, this embodiment can be implemented by changing as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

・ "About change processing"
In the above embodiment, the process of changing the elastic modulus K and the viscosity coefficient C is executed only when the angular manipulated variable Tt * is set to “0”, but the present invention is not limited to this. For example, when the value obtained by dividing the angular manipulated variable Tt * in FIG. 2 by the angular manipulated variable Tt1 * is equal to or less than a predetermined ratio, a process of changing the elastic modulus K or the viscosity coefficient C may be executed.

The change process for changing the relationship between the pinion angle command value θp *, which is the output to the axial force Taf, which is the input of the norm model calculation process M30, is not limited to the process of changing the elastic coefficient K and the viscosity coefficient C, for example. The process of changing only one of the two coefficients may be performed. In addition, for example, as described in the column of "Angle command value calculation process" below, when changing the normative model, neither the elastic modulus K nor the viscosity coefficient C is changed, but another parameter is changed instead. You may.

・ "Required torque Td"
In FIG. 2, the sum of the angle operation amount Tt * and the steering operation amount Ts * is defined as the required torque Td, but the present invention is not limited to this. For example, the angle manipulated variable Tt * may be the required torque Td.

In the process of FIG. 5, the angle manipulated variable Tt * is set to the required torque Td, but the present invention is not limited to this. For example, the sum of the angle manipulated variable Tt * and the steering manipulated variable Ts * may be the required torque Td.
・ "About angle command value calculation process"
In the above embodiment, the pinion angle command value θp * and the steering angle command value θh * are calculated by inputting the axial force Taf, but the present invention is not limited to this, and for example, the steering operation amount Ts * may be input. In the above embodiment, the axial force Taf is input and the pinion angle command value θp * and the steering angle command value θh * are calculated based on the above equation (c1) and the like. However, the pinion angle command value θp * and the steering angle command value are calculated. The logic (model) for calculating θh * is not limited to this.

Further, for example, in the process of FIG. 5, the steering angle ratio variable process M90 and the addition process M92 may be deleted, and the output of the norm model calculation process M30 may be set to the steering angle command value θh * and the pinion angle command value θp *.

・ "About the disturbance observer"
In the above embodiment, the disturbance observer is configured by a simple model in which the torque acting on the steering wheel 12 is balanced with the torque proportional to the angular acceleration of the steering angle, but the present invention is not limited to this. For example, the disturbance observer may be configured by using a model in which the torque acting on the steering wheel 12 is balanced with the sum of the torque proportional to the angular acceleration of the steering angle and the torque proportional to the angular velocity of the steering angle.

The method for calculating the estimated disturbance torque Tlde is not limited to the one illustrated in the above embodiment. For example, in the processing of FIG. 2, the angle manipulation amount Tt * and the steering manipulation amount Ts * are obtained from the second-order time differential value of the pinion angle command value θp * or the second-order time differential value of the pinion angle θp multiplied by the inertia coefficient Jp. And may be calculated by subtracting the steering torque Th.

・ "About angle manipulation amount calculation processing"
In the above embodiment, the feed forward operation amount Ttff is calculated based on the second-order time derivative value of the pinion angle command value θp *, but is not limited to this, and is calculated based on, for example, the second-order time derivative value of the pinion angle θp. , It may be calculated based on the second-order time derivative value of the estimated value θpe.

In the above embodiment, the feed forward term is calculated by modeling the electric power steering device 10 with a simple model in which the torque acting on the steering wheel 12 is balanced with the torque proportional to the angular acceleration of the steering angle. However, it is not limited to this. For example, the feed forward term may be calculated using a model in which the torque acting on the steering wheel 12 is balanced with the sum of the torque proportional to the angular acceleration of the steering angle and the torque proportional to the angular velocity of the steering angle. .. This is, for example, the value obtained by multiplying the second-order time derivative value of the pinion angle command value θp * by the inertial coefficient Jp and the value obtained by multiplying the first-order time derivative value of the pinion angle command value θp * by the viscosity coefficient Cp. This can be realized by setting the sum as the feed forward operation amount Ttff. Here, the viscosity coefficient Cp, which is a proportional coefficient of the angular velocity, is different from the viscosity coefficient C used in the normative model calculation process M30 in that the aim is different, and the actual behavior of the electric power steering device 10 is modeled with as high accuracy as possible. It is desirable to make it.

The feedback control amount in the input of the feedback term calculation process M56 is not limited to the estimated value θpe and its first-order time derivative value. For example, instead of the estimated value θpe or its first-order time derivative value, the pinion angle θp or its time derivative value itself may be used.

The feedback term calculation process M56 is not limited to the process of outputting the sum of the output values of the proportional element and the differential element. For example, the output value of the proportional element may be output, or the output value of the differential element may be output, for example. Further, for example, it may be a process of outputting the sum of at least one of the output value of the proportional element and the output value of the differential element and the output value of the integrating element. When using the output value of the integrating element, it is desirable to delete the disturbance observer. However, it is not essential to use the disturbance observer when the output value of the integrating element is not used.

・ "About convertible angle"
In the above embodiment, the pinion angle θp is used as the convertible angle, but the present invention is not limited to this. For example, it may be the steering angle itself of the steering wheel 12.

・ "About steering operation amount"
In the above embodiment, the steering operation amount Ts * is converted into the torque of the steering shaft 24, but the present invention is not limited to this. For example, it may be the torque of the electric motor 32. However, in that case, for example, the sum of the value obtained by dividing the steering torque Th by the reduction ratio Km and the steering operation amount Ts * is set to the axial force Taf0, or the value obtained by multiplying the steering operation amount Ts * by the reduction ratio Km and the steering torque Th. The sum of and is taken as the axial force Taf0.

・ "About angle manipulation amount"
In the above embodiment, the angular manipulated variable Tt * is converted into the torque of the steering shaft 24, but the present invention is not limited to this. For example, it may be the torque of the electric motor 32. However, for example, when the steering operation amount Ts * is converted into the torque of the steering shaft 24, the required torque Td is the sum of the angle operation amount Tt * multiplied by the reduction ratio Km and the steering operation amount Ts *. To do.

・ "About target torque calculation process"
The base target torque calculation process is not limited to the process of calculating the base target torque Thb * according to the axial force Taf0 and the vehicle speed V. For example, the process may be a process of calculating the base target torque Thb * based only on the axial force Taf0.

It is not essential to correct the base target torque Thb * with the hysteresis correction amount Thys.
・ "About the steering control device"
The steering control device is not limited to the one provided with the CPU 42 and the ROM 44 to execute software processing. For example, a dedicated hardware circuit (for example, ASIC or the like) for hardware processing of at least a part of the software processed in the above embodiment may be provided. That is, the steering control device may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processing according to a program and a program storage device such as a ROM that stores the program are provided. (B) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing are provided. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, there may be a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the processing may be executed by a processing circuit including at least one of one or more software processing circuits and one or more dedicated hardware circuits.

・ "About electric motors and drive circuits"
The electric motor is not limited to SPMSM, and may be IPMSM or the like. Further, the machine is not limited to the synchronous machine and may be an induction machine. Further, for example, it may be a DC motor with a brush. In that case, an H-bridge circuit may be adopted as the drive circuit.

・ "About steering actuator"
The steering actuator is not limited to the one illustrated in the above embodiment. For example, a so-called dual pinion type may be provided, which is provided with a second pinion shaft for transmitting the power of the electric motor 32 to the rack shaft 26 in addition to the pinion shaft 24c. Further, for example, the output shaft 32a of the electric motor 32 may be mechanically connected to the steering shaft 24. In that case, the steering actuator shares the steering shaft 24 and the rack and pinion mechanism 27 with the steering mechanism.

·"others"
For example, in FIG. 4, the clutch 60 may be deleted, and instead, the input shaft 24d may be mechanically connected to the pinion shaft 24c via a gear ratio variable mechanism that makes the gear ratio variable. Even in that case, the same processing as that illustrated in the case of steer-by-wire can be realized.

10 ... Electric power steering device, 12 ... Steering wheel, 16 ... Rack housing, 20 ... Steering mechanism, 22 ... Steering wheel, 24 ... Steering shaft, 24a ... Column shaft, 24b ... Intermediate shaft, 24c ... Pinion shaft, 24d ... Input shaft, 26 ... Rack shaft, 27 ... Rack and pinion mechanism, 28 ... Tie rod, 30 ... Steering actuator, 32 ... Electric motor, 32a ... Output shaft, 33 ... Inverter, 34 ... Ball screw mechanism, 36 ... Belt type reduction mechanism , 40 ... Steering control device, 42 ... CPU, 44 ... ROM, 46 ... Peripheral circuit, 48 ... Communication line, 50 ... Torque sensor, 52 ... Vehicle speed sensor, 54 ... Rotation angle sensor, 60 ... Clutch, 70 ... Reducer , 72 ... electric motor, 74 ... inverter, 80 ... reaction actuator, 82 ... steering angle sensor.

Claims (7)

The operation target is a steering actuator that has a built-in electric motor and steers the steering wheel.
Steering operation that is the amount of operation of the electric motor for steering the steering wheel so that the steering torque input by the driver is feedback-controlled to the target steering torque, and is the amount of operation that can be converted into the torque required for the electric motor. Steering operation amount calculation process to calculate the amount and
An angle command value calculation process for calculating an angle command value, which is a convertible angle command value that can be converted into a steering angle of the steering wheel according to the steering operation amount, and
The angle operation amount calculation process for calculating the angle operation amount, which is the operation amount for feedback-controlling the convertible angle to the angle command value and is the operation amount that can be converted into the torque required for the electric motor.
An operation process of operating the drive circuit of the electric motor in order to control the torque of the electric motor according to at least one of the two operation amounts of the steering operation amount and the angle operation amount.
Adjustment processing that adjusts the value obtained by subtracting the angle operation amount reflected in the operation process from the angle operation amount calculated by the angle operation amount calculation process, and inputs the adjusted angle operation amount to the operation process. When,
A steering control device that executes a change process for changing the relationship between the output of the angle command value calculation process and the input of the angle command value calculation process according to the subtracted value. When the magnitude of the value obtained by subtracting the angle manipulation amount reflected in the operation processing from the angle manipulation amount calculated by the angle manipulation amount calculation processing is large, the angle command value calculation processing is the angle more than when it is small. The steering control device according to claim 1, wherein a correction process for correcting the size of the input when calculating the command value is executed. The operation process includes a first operation process for operating the drive circuit to control the torque of the electric motor at least according to the angle operation amount, and the electric motor according to the steering operation amount regardless of the angle operation amount. Including a second operation process for operating the drive circuit to control the torque of
The steering control device according to claim 1 or 2, wherein the change process includes a process of changing the relationship between the output and the input when the first operation process is executed and when the second operation process is executed. The steering control device according to claim 1 or 2, wherein the operation process includes a process of controlling the torque of the electric motor according to the angle operation amount regardless of the steering operation amount. The angle command value calculation process includes a process of calculating an elastic force that is a force on the side that reduces the magnitude of the steering angle in proportion to the magnitude of the angle command value, and a steering operation amount of the elastic force. Including the process of calculating the angle command value according to the value reduced by
The steering control device according to any one of claims 1 to 4, wherein the change processing includes a processing of changing the proportional coefficient of the elastic force with respect to the magnitude of the steering angle according to the subtracted value. .. The angle command value calculation process includes a process of calculating a viscous force, which is a force on the side that reduces the magnitude of the steering angle in proportion to the magnitude of the change speed of the angle command value, and the steering operation amount. Includes a process of calculating the angle command value according to the value reduced by the viscous force.
The steering control device according to any one of claims 1 to 5, wherein the change process includes a process of changing the proportional coefficient of the viscous force with respect to the magnitude of the change rate according to the subtracted value. Any one of claims 1 to 6 for executing the target steering torque calculation process for calculating the target steering torque based on the sum of the amounts obtained by converting the steering operation amount and the steering torque into the force acting on the same object. The steering control device described in the section.