JP2017154632A - Electric power steering device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of controlling drive of an electric motor so as to be capable of rapidly coping with disturbance caused by a varying road surface.SOLUTION: An electric power steering device includes: an electric motor that adds an auxiliary force to steering of a steering wheel of a vehicle; a rack shaft for rolling a rolling wheel of the vehicle; and a control unit that controls a driving force of the electric motor on the basis of a deviation between a rate of change in a standard rack axial force becoming a standard of an axial force generated in the rack shaft and a rate of change in an actual rack axial force becoming an actual axial force generated in the rack shaft.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an electric power steering apparatus and a program.

In recent years, a technique for improving the running stability of a vehicle with respect to a change in road surface in an electric power steering apparatus has been proposed.
For example, the electric power steering device described in Patent Document 1 is configured as follows. That is, a motor that adds power to a steering system that gives a steering angle to a steered wheel, a steering force detection means that detects a manual steering force acting on the steering system, and at least a steering assist force based on the output of the steering force detection means And an electric power steering device used in a rack / pinion type steering device, wherein a reference rack shaft load of a steered wheel is determined from a steering angle and a vehicle speed. And means for detecting the actual rack shaft load of the steered wheel, and the control means sets the steering resistance force according to the deviation between the reference rack shaft load and the actual rack shaft load.

Japanese Patent Laid-Open No. 11-49000

In order to control the assist force of the electric motor based on the standard rack shaft load (rack shaft load) and the actual rack shaft load, and to improve running stability on the changing road surface, It is desirable to control the drive of the electric motor so that it can quickly respond to the disturbance caused by it.
It is an object of the present invention to provide an electric power steering device and a program that can control the driving of an electric motor so as to be able to quickly cope with disturbance caused by a changing road surface.

  For this purpose, the present invention provides an electric motor that applies an assisting force to the steering wheel of a vehicle, a rack shaft that rolls the rolling wheels of the vehicle, and a norm that serves as a norm for the axial force generated on the rack shaft. A control device that controls the driving force of the electric motor based on a deviation between a change rate of the rack axial force and a change rate of the actual rack axial force that is an actual axial force generated on the rack shaft. This is an electric power steering device.

  From another point of view, the present invention provides a computer with a normative change speed calculation function for calculating a change rate of a normative rack axial force, which is a norm of an axial force generated on a rack shaft that rolls a rolling wheel of a vehicle. An actual change speed calculating function for calculating a change speed of an actual rack axial force that is an actual axial force generated on the rack shaft, and a change speed of the reference rack axial force calculated by the reference change speed calculating function and the actual change. And a function of setting a target current to be supplied to the electric motor based on a deviation from the change speed of the actual rack axial force calculated by the speed calculation function.

  ADVANTAGE OF THE INVENTION According to this invention, the drive of an electric motor can be controlled so that it can respond rapidly to the disturbance resulting from the changing road surface.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of a control apparatus. It is a schematic block diagram of a control part. It is a schematic block diagram of a basic target electric current setting part. It is the schematic of the control map which shows a response | compatibility with steering torque, vehicle speed, and base current. It is a schematic block diagram of a correction | amendment electric current setting part. It is the schematic of the control map which shows a response | compatibility with a steering angle and vehicle speed, and a reference | standard rack axial force. It is the schematic of the control map which shows a response | compatibility with correction | amendment electric current and change speed deviation. It is a flowchart which shows the procedure of the correction current setting process which a correction current setting part performs. It is a figure which illustrates the effect | action of a correction | amendment electric current setting part.

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

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

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106. The rack shaft 105, the pinion shaft 106, and the like function as a transmission mechanism that transmits the rotational operation force of the handle 101 as the rolling force of the front wheel 150. The pinion shaft 106 applies a driving force (rack axial force) for rolling the front wheel 150 by rotating to the rack shaft 105 for rolling the front wheel 150.

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

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

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

  The steering device 100 configured as described above drives the electric motor 110 based on the steering torque T detected by the torque sensor 109, and transmits the driving force (generated torque) of the electric motor 110 to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the handle 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
The control device 10 includes a torque signal Td obtained by converting the steering torque T detected by the torque sensor 109 described above into an output signal, and a vehicle speed signal obtained by converting the vehicle speed Vc detected by the vehicle speed detector 170 into an output signal. v, a rotation angle signal θs from the resolver 120, and the like are input.

Then, the control device 10 calculates (sets) a target current It to be supplied to the electric motor 110, and a control unit that performs feedback control based on the target current It calculated by the target current calculation unit 20. 30.
Further, the control device 10 calculates a motor rotation speed Vm based on the motor rotation angle calculation unit 71 that calculates the motor rotation angle θ of the electric motor 110 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. And a motor rotation speed calculation unit 72 for calculating. In addition, the control device 10 includes a steering angle calculation unit 73 that calculates a steering angle Ra that is a rotation angle of the handle 101 based on the motor rotation angle θ.

First, the target current calculation unit 20 will be described in detail.
The target current calculation unit 20 includes a basic target current setting unit 27 that sets a basic target current Itf that is a basis of the target current It supplied to the electric motor 110 based on the torque signal Td and the vehicle speed signal v. Further, the target current calculation unit 20 includes a correction current setting unit 28 that sets a correction current Ir that corrects the basic target current Itf. The target current calculation unit 20 includes a target current setting unit 29 that finally sets the target current It based on the basic target current Itf and the correction current Ir.
The basic target current setting unit 27, the correction current setting unit 28, and the target current setting unit 29 will be described in detail later.

FIG. 3 is a schematic configuration diagram of the control unit 30.
As shown in FIG. 3, the control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. And a motor current detection unit 33 for detection.
The motor drive control unit 31 is based on a deviation between the target current It finally determined by the target current calculation unit 20 and the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 that performs feedback control, and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.

  The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current It finally determined by the target current calculating unit 20 and the actual current Im detected by the motor current detecting unit 33, and the deviation is A feedback (F / B) processing unit 42 that performs feedback processing so as to be zero.

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

The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32.

The motor rotation angle calculation unit 71 (see FIG. 2) calculates the motor rotation angle θ based on the rotation angle signal θs from the resolver 120.
The motor rotation speed calculation unit 72 (see FIG. 2) calculates the motor rotation speed Vm of the electric motor 110 based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. The motor rotation speed calculation unit 72 outputs a motor rotation speed signal Vms including the absolute value of the motor rotation speed Vm and the rotation direction of the electric motor 110.

  The steering angle calculation unit 73 (see FIG. 2) has a correlation between the rotation angle of the handle 101 and the motor rotation angle θ of the electric motor 110 because the handle 101, the speed reduction mechanism 111, and the like are mechanically coupled. In view of this, the steering angle Ra is calculated based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. For example, the steering angle calculation unit 73 performs steering based on the integrated value of the difference between the previous value and the current value of the motor rotation angle θ calculated periodically (for example, every 1 millisecond) by the motor rotation angle calculation unit 71. The angle Ra is calculated.

[Basic target current setting section]
FIG. 4 is a schematic configuration diagram of the basic target current setting unit 27.
The basic target current setting unit 27 calculates a base current calculation unit 21 that calculates a base current Ib that serves as a base for setting the basic target current Itf, and an inertia compensation current Is that cancels the moment of inertia of the electric motor 110. An inertia compensation current calculation unit 22 and a damper compensation current calculation unit 23 that calculates a damper compensation current Id that limits the rotation of the electric motor 110 are provided. Further, the basic target current setting unit 27 determines a basic target current Itf based on values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. 25. The basic target current setting unit 27 includes a phase compensation unit 26 that compensates for the phase of the steering torque T (torque signal Td) detected by the torque sensor 109.

FIG. 5 is a schematic diagram of a control map showing the correspondence between the steering torque T, the vehicle speed Vc, and the base current Ib.
The base current calculation unit 21 generates a base current based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26, the vehicle speed signal v from the vehicle speed detection unit 170, and the control map illustrated in FIG. Ib is calculated.
The inertia compensation current calculation unit 22 calculates an inertia compensation current Is for canceling the moment of inertia of the electric motor 110 and the system based on the torque signal Ts and the vehicle speed signal v.
The damper compensation current calculation unit 23 calculates a damper compensation current Id that limits the rotation of the electric motor 110 based on the torque signal Ts, the vehicle speed signal v, and the motor rotation speed Vm of the electric motor 110.

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

[Target current setting section]
The target current setting unit 29 sets a value obtained by adding the basic target current Itf set by the basic target current setting unit 27 and the correction current Ir set by the correction current setting unit 28 as the target current It (It = Itf + Ir).

Here, the state in which the torsion bar 112 has a twist of 0 is defined as a neutral state (neutral position), and the handle 101 (lower connection shaft 108) and the pinion shaft 106 when the handle 101 is rotated clockwise from the neutral state (neutral position) The direction in which the relative rotation angle changes (the direction in which the relative rotation angle occurs) is positive (the steering torque T is positive). Further, the direction in which the relative rotation angle between the handle 101 (lower connection shaft 108) and the pinion shaft 106 changes when the handle 101 rotates counterclockwise from the neutral state (the direction in which the relative rotation angle occurs) is negative (the steering torque T is negative). ).
When the handle 101 rotates to the right, a rack axial force is generated on the rack shaft 105 to roll the front wheel 150 to the right. When the handle 101 rotates to the left, the front wheel 150 rotates to the left on the rack shaft 105. The rack axial force to move is produced. Hereinafter, the sign of the rack axial force that rolls the front wheel 150 generated on the rack shaft 105 in the right direction is plus, and the sign of the rack axial force that rolls the front wheel 150 generated on the rack shaft 105 in the left direction is minus. Further, the rotation direction of the electric motor 110 that generates a positive rack axial force on the rack shaft 105 is positive, and the rotation direction of the electric motor 110 that generates a negative rack axial force on the rack shaft 105 is negative.
When the steering torque T detected by the torque sensor 109 is positive, the base current calculation unit 21 calculates the base current Ib so as to rotate the electric motor 110 in the positive direction, and the base current Ib The sign is positive. That is, as shown in FIG. 4, when the steering torque T is positive, the base current calculation unit 21 calculates a positive base current Ib, and generates torque in a direction that rotates the electric motor 110 in the positive direction. When the steering torque T is negative, the base current calculation unit 21 calculates a negative base current Ib and generates torque in a direction that rotates the electric motor 110 in the negative direction.
Further, the sign of the steering angle Ra when the steering wheel 101 is rotated in the right direction from the state where the steering angle Ra that is the rotation angle of the handle 101 is 0 degree is positive, and the sign of the steering angle Ra when the steering wheel 101 is rotated in the left direction. Is negative.

[Correction current setting section]
Next, the correction current setting unit 28 will be described in detail.
FIG. 6 is a schematic configuration diagram of the correction current setting unit 28.
The correction current setting unit 28 is a deviation between the changing speed of the reference rack axial force Frm, which is a reference of the axial force generated on the rack shaft 105, and the changing speed of the actual rack axial force Fra that is the actual axial force generated on the rack shaft 105. Based on the above, the correction current Ir is set.

  The correction current setting unit 28 includes a steering state grasping unit 280 that grasps the steering state of the handle 101. Further, the correction current setting unit 28 includes a reference rack axial force calculation unit 281 that calculates the reference rack axial force Frm, and an actual rack axial force calculation unit 282 that calculates the actual rack axial force Fra. Further, the correction current setting unit 28 is a norm as an example of a normative rack axial force change rate calculation unit that calculates a normative force change rate Vfrm that is a change speed of the normative rack axial force Frm calculated by the normative rack axial force calculator 281. A force change speed calculation unit 283 is provided. Further, the correction current setting unit 28 is an actual force change as an example of an actual rack axial force change speed calculation unit that calculates an actual force change speed Vfra that is a change speed of the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282. A speed calculation unit 284 is provided. Further, the correction current setting unit 28 calculates a change speed deviation ΔVfr that is a deviation between the reference force change speed Vfrm calculated by the reference force change speed calculation unit 283 and the actual force change speed Vfra calculated by the actual force change speed calculation unit 284. A change speed deviation calculation unit 285 is provided. The correction current setting unit 28 also includes a correction current calculation unit 286 that calculates the correction current Ir based on the change speed deviation ΔVfr calculated by the change speed deviation calculation unit 285.

  The correction current setting unit 28 includes a steering state grasping unit 280, a reference rack axial force calculation unit 281, an actual rack axial force calculation unit 282, a reference force change speed calculation unit 283, an actual force change speed calculation unit 284, and a change speed deviation calculation. The unit 285 and the correction current calculation unit 286 calculate (set) the correction current Ir by repeatedly executing processing to be described later at predetermined time intervals (for example, 1 millisecond).

(Steering condition grasping part)
The steering condition grasping unit 280 is based on the steering angle Ra calculated by the steering angle calculating unit 73 and the steering angle deviation obtained by subtracting the previous value from the current value of the steering angle Ra calculated by the steering angle calculating unit 73. To grasp the steering state of the handle 101. For example, the steering state grasping unit 280 has the handle 101 cut when the sign obtained by multiplying the sign of the steering angle Ra calculated by the steering angle calculating part 73 and the sign of the steering angle deviation is positive. And grasp. On the other hand, when the sign obtained by multiplying the sign of the steering angle Ra calculated by the steering angle calculating part 73 and the sign of the steering angle deviation is negative, the steering state grasping part 280 turns back the handle 101. And grasp. In addition, the steering state grasping unit 280 grasps that the steering state is maintained when the steering angle deviation is zero. The steering condition grasping unit 280 is (1) the steering angle Ra is positive and the turning direction, (2) the steering angle Ra is positive and the turning direction, (3) the steering angle Ra is negative and the turning direction, (4) steering The angle Ra is minus, and it is grasped whether the turning-back direction or (5) the steering maintained state.

(Standard rack axial force calculation unit)
FIG. 7 is a schematic diagram of a control map showing the correspondence between the steering angle Ra and the vehicle speed Vc and the reference rack axial force Frm.
The reference rack axial force calculation unit 281 calculates a reference rack axial force Frm according to the steering state of the handle 101 and the vehicle speed Vc. The reference rack axial force calculation unit 281 is exemplified in FIG. 7 showing the steering state of the handle 101 and the correspondence between the vehicle speed Vc and the reference rack axial force Frm, which is created based on an empirical rule and stored in the ROM in advance. The reference rack axial force Frm is calculated by substituting the steering state of the handle 101 and the vehicle speed Vc into the control map or the calculation formula.

  Consider a case where the reference rack axial force calculation unit 281 calculates the reference rack axial force Frm using the control map illustrated in FIG. In the control map illustrated in FIG. 7, even if the steering angle Ra and the vehicle speed Vc are the same, the value of the reference rack axial force Frm differs between when the steering wheel 101 is cut and when it is turned back. . Therefore, the reference rack axial force calculation unit 281 is based on, for example, the reference rack axial force based on the steering angle Ra calculated by the steering angle calculation unit 73 and the state of steering of the handle 101 grasped by the steering situation grasping unit 280. Frm is calculated. When the handle 101 is cut, the reference rack axial force calculation unit 281 calculates the reference rack axial force Frm by substituting the steering angle Ra and the vehicle speed Vc into the control map when the handle 101 is cut. calculate. On the other hand, when the handle 101 is turned back, the reference rack axial force calculation unit 281 calculates the reference rack axial force Frm by substituting the steering angle Ra and the vehicle speed Vc into the control map when the handle 101 is turned back. calculate. Further, the reference rack axial force calculation unit 281 sets the reference rack axial force Frm to 0 when the handle 101 is being steered.

(Actual rack axial force calculation unit)
The actual rack axial force calculation unit 282 includes the steering torque T detected by the torque sensor 109, the motor rotation angle θ calculated by the motor rotation angle calculation unit 71, and the actual torque detected by the motor current detection unit 33. The actual rack axial force Fra is calculated based on the current Im.
Here, since the steering device 100 according to the present embodiment is a pinion assist device, the actual rack axial force Fra is assumed to be equal to the axial force applied from the pinion shaft 106, and the pinion torque Tp applied to the pinion shaft 106 Calculate based on The actual rack axial force Fra is a value obtained by dividing the pinion torque Tp by the pitch circle radius rp of the pinion 106a (Fra = Tp / rp).

The pinion torque Tp can be estimated as a torque obtained by adding the steering torque T applied by the driver via the handle 101 and the motor torque Tm applied by increasing the output shaft torque To of the electric motor 110 by the speed reduction mechanism. (Tp = T + Tm).
The steering torque T can be detected based on the torque signal Td from the torque sensor 109.
The motor torque Tm is a value obtained by multiplying the output shaft torque To by the reduction ratio (gear ratio) N of the reduction mechanism 111 (Tm = To × N).
For the output shaft torque To, the motor rotation angle θ calculated by the motor rotation angle calculation unit 71 and the actual current Im detected by the motor current detection unit 33 are substituted into a calculation formula stored in advance in the ROM. This can be calculated. Instead of using the motor rotation angle θ calculated by the motor rotation angle calculation unit 71, a motor rotation angle θ calculated from a motor back electromotive force by a predetermined formula may be used.

(Nominal force change speed calculation part)
The normative force change rate calculation unit 283 calculates the normative force change rate Vfrm by time-differentiating the normative rack axial force Frm calculated by the normative rack axial force calculator 281. For example, the normative force change speed calculation unit 283 obtains a value obtained by subtracting the previous value Frm (n−1) from the current value Frm (n) of the normative rack axial force Frm calculated by the normative rack axial force calculation unit 281. The reference force change speed Vfrm is calculated by dividing by the deviation time Δtm between the time when Frm (n) is calculated and the time when the previous value Frm (n−1) is calculated (Vfrm = (Frm (n) −Frm). (N-1)) / Δtm).

(Ability change rate calculation part)
The actual force change speed calculation unit 284 calculates the actual force change speed Vfra by differentiating the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282 with time. For example, the actual force change speed calculation unit 284 subtracts the previous value Fra (n−1) from the current value Fra (n) of the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282 to obtain the current value Fra. The actual change speed Vfra is calculated by dividing by the deviation time Δta between the time when (n) is calculated and the time when the previous value Fra (n−1) is calculated (Vfra = (Fra (n) −Fra (n -1)) / Δta).

(Change rate deviation calculator)
The change speed deviation calculation unit 285 calculates a change speed deviation ΔVfr by subtracting the reference force change speed Vfrm calculated by the reference force change speed calculation unit 283 from the actual force change speed Vfra calculated by the actual force change speed calculation unit 284 ( ΔVfr = Vfra−Vfrm).

(Correction current calculation unit)
FIG. 8 is a schematic diagram of a control map showing the correspondence between the correction current Ir and the change speed deviation ΔVfr.
The correction current calculation unit 286 calculates a correction current Ir corresponding to the change rate deviation ΔVfr calculated by the change rate deviation calculation unit 285. The correction current calculation unit 286 calculates the correction current Ir by substituting the change rate deviation ΔVfr calculated by the change rate deviation calculation unit 285 into, for example, the control map illustrated in FIG. 8 or a predetermined calculation formula. In the control map illustrated in FIG. 8, the correction current Ir increases in the positive direction as the change speed deviation ΔVfr increases in the positive direction, and the correction current Ir increases in the negative direction as the change speed deviation ΔVfr increases in the negative direction. It is set to be. That is, as the actual force change speed Vfra is smaller than the reference force change speed Vfrm, in other words, for example, the steering wheel 101 is taken when the right rotation direction is cut, and the change speed of the steering angle Ra is rapidly increased in the plus direction (right rotation direction). The correction current Ir is set so as to increase in the minus direction (the direction in which the right rotation of the handle 101 is suppressed) as the value increases. On the other hand, as the actual force change speed Vfra is larger than the normative force change speed Vfrm, in other words, for example, the steering wheel 101 is taken when the left turn direction is cut, and the change speed of the steering angle Ra suddenly decreases in the minus direction (left turn direction). The correction current Ir is set so as to increase in the positive direction (the direction in which the left rotation of the handle 101 is suppressed) as it increases.

  However, the correction current calculation unit 286, when there is a change in the steering state of the steering wheel 101, the change speed deviation ΔVfr becomes a value in one of the plus direction and the minus direction from the state of 0, While the value in one direction continues, the correction current Ir corresponding to the change speed deviation ΔVfr is calculated. On the other hand, the correction current calculation unit 286 sets the correction current Ir to 0 without calculating the correction current Ir according to the change speed deviation ΔVfr when the value is switched from one direction to the other direction in the same steering situation. To do. This is due to the following reason. When the change speed deviation ΔVfr is changed from 0 to either the plus direction or the minus direction, the handle 101 is moved to the steering angle Ra not intended by the driver due to the handle 101 being taken. It is considered that the vehicle is rotating, but when the vehicle is subsequently switched from one direction to the other, it is considered that the driver is trying to return the handle 101 taken by the driver. When the steering wheel 101 is rotated to the steering angle Ra not intended by the driver due to the steering wheel 101 being taken, it is desirable to give a correction current Ir in a direction to suppress the steering wheel, but driving This is because it is not desirable to provide the correction current Ir in a direction that suppresses the operation of the handle 101 in the returning direction when the person is trying to return the handle 101 taken by the person.

Next, the procedure of the correction current setting process performed by the correction current setting unit 28 will be described using a flowchart.
FIG. 9 is a flowchart showing the procedure of the correction current setting process performed by the correction current setting unit 28.
The correction current setting unit 28 repeatedly executes the correction current setting process, for example, every predetermined period (for example, 1 millisecond).
First, the correction current setting unit 28 grasps the steering state of the handle 101 (the value of the steering angle Ra, whether it is the cutting direction or the switching back direction) (S101). The process of S101 is a process performed by the steering state grasping unit 280.
Next, the correction current setting unit 28 calculates a reference rack axial force Frm (S102). The process of S102 is a process performed by the reference rack axial force calculation unit 281.
Next, the correction current setting unit 28 calculates the actual rack axial force Fra (S103). The process of S103 is a process performed by the actual rack axial force calculation unit 282.
Next, the correction current setting unit 28 calculates the normative force change speed Vfrm (= (Frm (n) −Frm (n−1)) / Δtm) (S104). The process of S104 is a process performed by the normative force change speed calculation unit 283.
Next, the correction current setting unit 28 calculates an ability change speed Vfra (= (Fra (n) −Fra (n−1)) / Δta) (S105). The process of S105 is a process performed by the ability change speed calculation unit 284.
Next, the correction current setting unit 28 calculates a change speed deviation ΔVfr (= Vfrm−Vfra) (S106). The process of S106 is a process performed by the change speed deviation calculation unit 285.
Next, the correction current setting unit 28 determines whether or not the steering state of the handle 101 grasped in S101 has changed from the previous time (S107). The process of S107 is a process performed by the steering status grasping unit 280.
When there is no change in the steering state of the steering wheel 101 (YES in S107), the correction current setting unit 28 determines whether or not the sign of the change speed deviation ΔVfr calculated in S106 has changed from the previous time (S108). ). The process of S108 is a process performed by the correction current calculation unit 286.
Then, when there is no change in the sign of the change speed deviation ΔVfr (YES in S108), the correction current setting unit 28 calculates a correction current Ir corresponding to the change speed deviation ΔVfr calculated in S106 (S109). . The process of S109 is a process performed by the correction current calculation unit 286. On the other hand, when there is a change in the sign of the change speed deviation ΔVfr (NO in S108), the correction current setting unit 28 sets the correction current Ir to 0 (S110).
On the other hand, when there is a change in the steering state of the steering wheel 101 (NO in S107), the correction current setting unit 28 calculates a correction current Ir corresponding to the change speed deviation ΔVfr calculated in S106 (S109).

(Operation of correction current setting unit)
FIG. 10 is a diagram illustrating the operation of the correction current setting unit 28.
For example, consider a case where the handle 101 is taken in the clockwise direction when the handle 101 is cut in the clockwise direction (when the steering angle Ra is a positive value and gradually increases). .
In this case, the reference rack axial force Frm calculated by the reference rack axial force calculation unit 281 gradually increases as shown by a two-dot chain line in FIG. On the other hand, the actual rack axial force Fra calculated by the actual rack axial force calculating unit 282 temporarily decreases because the handle 101 is taken in the rotational direction, as shown by the solid line in FIG. The handle 101 that has been taken is enlarged to return to the original position. The standard force change rate Vfrm calculated by the standard force change rate calculation unit 283 becomes 0 (see the two-dot chain line in FIG. 10B), whereas the actual force change rate Vfra calculated by the actual force change rate calculation unit 284 is obtained. As shown by the solid line in FIG. 10 (b), it temporarily becomes negative due to the handle 101 being taken, and then temporarily becomes positive and returns to zero. Then, the change speed deviation ΔVfr calculated by the change speed deviation calculating unit 285 also temporarily becomes negative as shown by the solid line in FIG. As a result, the correction current calculator 286 calculates a negative correction current Ir corresponding to the change speed deviation ΔVfr when the change speed deviation ΔVfr calculated by the change speed deviation calculator 285 is negative. On the other hand, the correction current calculation unit 286 sets the correction current Ir to 0 when the change speed deviation ΔVfr changes from minus to plus (NO in S108). In FIG. 10B, the amount proportional to the correction current Ir set by the correction current setting unit 28 in the above process is indicated by hatching.

  For the purpose of comparison with the correction current setting unit 28 according to the present embodiment, the reference rack axial force Frm calculated by the reference rack axial force calculation unit 281 and the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282 are calculated. Consider the case where the correction current Ir is set according to the deviation. A solid line shown in FIG. 10C indicates a deviation (= Fra−) obtained by subtracting the reference rack axial force Frm calculated by the reference rack axial force calculation unit 281 from the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282. Frm). An amount proportional to the correction current Ir set in accordance with this deviation is indicated by the oblique lines shown in FIG.

  Comparing the oblique line shown in FIG. 10B with the oblique line shown in FIG. 10C, the oblique line shown in FIG. 10B is the oblique line shown in FIG. 10C. This indicates that more correction current Ir is set more quickly because it is larger quickly. Therefore, according to the steering device 100 having the correction current setting unit 28 according to the present embodiment, for example, the correction current Ir in a direction to suppress the steering wheel can be given quickly. As a result, it is possible to quickly respond to disturbance caused by the changing road surface, and thus it is possible to improve the running stability on the changing road surface.

<Description of the program>
Further, the processing performed by the control device 10 described above can be realized by cooperation of software and hardware resources. In this case, the CPU inside the control computer provided in the control device 10 executes a program that realizes each function of the control device 10 and realizes each of these functions.

  Therefore, the processing performed by the control device 10 includes a computer, a norm change speed calculation function for calculating a change speed of the normative rack axial force Frm, which is a norm of the axial force generated in the rack shaft 105 that rolls the rolling wheels of the vehicle, and a rack. An actual change speed calculation function for calculating a change speed of an actual rack axial force Fra that is an actual axial force generated on the shaft 105; a change speed of the reference rack axial force Frm calculated by the reference change speed calculation function; and the actual change speed. It can also be understood as a program that realizes a function of setting a target current to be supplied to the electric motor 110 based on a deviation from the change speed of the actual rack axial force Fra calculated by the calculation function.

  The program for realizing the present embodiment can be provided not only by communication means but also by storing it in a recording medium such as a CD-ROM.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 21 ... Base current calculation part, 27 ... Basic target current setting part, 28 ... Correction current setting part, 29 ... Target current setting part, 30 ... Control part, 100 ... Electric power Steering device, 110 ... electric motor, 280 ... steering state grasping unit, 281 ... standard rack axial force calculation unit, 282 ... real rack axial force calculation unit, 283 ... standard force change speed calculation unit, 284 ... actual force change speed calculation unit, 285 ... change speed deviation calculation unit, 286 ... correction current calculation unit

Claims (5)

An electric motor for applying an assisting force to the steering wheel of the vehicle;
A rack shaft for rolling the rolling wheels of the vehicle;
The driving force of the electric motor based on the deviation between the change speed of the reference rack axial force that is a reference of the axial force generated on the rack shaft and the change speed of the actual rack axial force that is the actual axial force generated on the rack shaft A control device for controlling
An electric power steering apparatus comprising: The control device is configured to generate a target current based on a basic target current that is a basis of a target current that is supplied to the electric motor that is set based on a steering torque of the steering wheel, and a correction current that is set based on the deviation. The electric power steering apparatus according to claim 1, wherein The control device includes a basic target current setting unit that sets a basic target current that is a basis of a target current supplied to the electric motor based on a steering torque of the steering wheel;
A correction current setting unit for setting a correction current based on the deviation;
A target current setting unit for setting the target current based on the basic target current set by the basic target current setting unit and the correction current set by the correction current setting unit;
The electric power steering apparatus according to claim 1 or 2, further comprising: The correction current setting unit includes a reference rack axial force change rate calculation unit that calculates a change rate of the reference rack axial force;
An actual rack axial force change speed calculation unit for calculating a change speed of the actual rack axial force;
A correction current is calculated based on a deviation between the change rate of the reference rack axial force calculated by the reference rack axial force change rate calculation unit and the change rate of the actual rack axial force calculated by the actual rack axial force change rate calculation unit. A correction current calculation unit for calculating,
The electric power steering apparatus according to claim 3, comprising: On the computer,
A reference change speed calculation function for calculating a change speed of a reference rack axial force that is a reference of an axial force generated in a rack shaft that rolls the rolling wheels of the vehicle;
An actual change speed calculation function for calculating a change speed of an actual rack axial force that is an actual axial force generated in the rack shaft;
A target current to be supplied to the electric motor is set based on a deviation between the change speed of the reference rack axial force calculated by the reference change speed calculation function and the change speed of the actual rack axial force calculated by the actual change speed calculation function. Function to
A program that realizes

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