JP6291310B2 - Electric power steering device, program - Google Patents

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.

  Moreover, the electric power steering apparatus described in Patent Document 2 applies a correction current in consideration of the degree of reaction force from the road surface. That is, the electric power steering apparatus described in Patent Document 2 includes a steering angle detection unit, a calculation unit that calculates an actual steering angular velocity, a calculation unit that calculates a base correction steering angular velocity based on the steering angle, and a vehicle speed multiplication based on the vehicle speed. Calculation means for calculating the coefficient value, calculation means for calculating the target steering angular speed by multiplying the base correction steering angular speed by the vehicle speed multiplication coefficient value, and calculating the base correction current value based on the difference between the target steering angular speed and the actual steering angular speed And calculating means for adding a corrected current value to the assist base current value to obtain an assist target current.

Japanese Patent Laid-Open No. 11-49000 JP 2006-123827 A

In performing the control for applying the correction current in consideration of the reaction force degree from the road surface, it is desirable to set the correction current in consideration of the disturbance input. Therefore, in addition to the control for applying the correction current calculated based on the difference between the target rudder angular speed and the actual rudder angular speed, the calculation is based on the deviation between the reference rack axial force and the actual rack axial force in order to consider disturbance input. It is also conceivable to perform control for applying a correction current. However, there is a risk that disturbance input estimation may become unstable output, such as when irregular and continuous disturbance is input, and when it becomes unstable, the steering feeling is lowered.
An object of the present invention is to provide an electric power steering device capable of applying an assist force in consideration of a reaction force degree from a road surface while suppressing a decrease in steering feeling.

For this purpose, the present invention provides an electric motor for applying an assisting force for steering a steering wheel of a vehicle, torque detecting means for detecting a steering torque of the steering wheel, and a steering angle which is a rotation angle of the steering wheel. Rudder angle detecting means for detecting, basic target current calculating means for calculating a basic target current as a basis of a target current supplied to the electric motor based on the steering torque detected by the torque detecting means, and the rudder angle detection Correction current calculation means for calculating a correction current for correcting the target current based on a deviation between a target steering angular speed corresponding to the steering angle and vehicle speed detected by the means and an actual steering angular speed, and the basic target current calculation means A target current decision for determining the target current based on the basic target current calculated by the correction current and the correction current calculated by the correction current calculation means. And the correction current calculation means is a reference rack that serves as a reference for the axial force generated on the rack shaft that rolls the rolling wheels based on the steering angle and the vehicle speed detected by the steering angle detection means. A reference rack axial force calculation unit that calculates an axial force; and an actual rack axial force calculation unit that calculates an actual rack axial force that is an actual axial force generated on the rack shaft. The correction current is changed based on the deviation between the reference rack axial force calculated by the actual rack axial force calculated by the actual rack axial force calculation means , and irregular and continuous disturbance is input. Thus , the electric power steering apparatus is characterized in that the deterioration of the steering feeling is suppressed .

Here, the correction current calculation means calculates a correction coefficient set based on a deviation between the reference rack axial force and the actual rack axial force based on a deviation between the target rudder angular velocity and the actual rudder angular velocity. The correction current may be calculated by multiplying the base correction current that is the base of the correction current.
Further, the correction current calculation means may change the correction current based on the vehicle speed.

From another viewpoint, the present invention provides a computer with a basic target current calculation function for calculating a basic target current that is a basis of a target current supplied to an electric motor based on a steering torque of a steering wheel of a vehicle, and the steering Correction current calculation for calculating a correction current for correcting the target current based on a deviation between a target steering angular speed and an actual steering angular speed according to a steering angle that is a rotation angle of a wheel and a vehicle speed that is a moving speed of the vehicle And a target current determination function for determining the target current based on the basic target current calculated by the basic target current calculation function and the correction current calculated by the correction current calculation function, and the correction current The calculation function is based on the rudder angle and the vehicle speed, and a reference rack axial force that calculates a reference rack axial force that is a reference for the axial force generated in the rack shaft that rolls the rolling wheels. The reference rack calculated by the reference rack axial force calculation function, and an actual rack axial force calculation function for calculating an actual rack axial force that is an actual axial force generated on the rack shaft. The correction current is changed based on the deviation between the axial force and the actual rack axial force calculated by the actual rack axial force calculation function , and the steering feeling is caused by irregular and continuous disturbance input. It is a program that realizes suppressing deterioration .

  ADVANTAGE OF THE INVENTION According to this invention, the assist force which considered the reaction force degree from a road surface can be provided, suppressing the fall of steering feeling.

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 current calculation part. It is the schematic of the control map which shows a response | compatibility with steering torque, vehicle speed, and base current. It is a schematic block diagram of a steering angular velocity deviation electric current calculation part. It is a control map which shows a response | compatibility with a steering angle and a vehicle speed, and a target steering angular speed. It is a control map which shows a response | compatibility with a steering angular velocity deviation and a base steering angular velocity deviation electric current. It is a control map which shows a response | compatibility with a rack axial force deviation and a base rack axial force correction coefficient. It is a control map which shows a response | compatibility with a vehicle speed and a vehicle speed correction coefficient.

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. The structure applied to is illustrated.

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

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106. The rack shaft 105, the pinion shaft 106, and the like function as a transmission mechanism that transmits the rotational operation force of the steering wheel 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 steering wheel 101 based on the relative rotation angle between the lower connecting shaft 108 and the pinion shaft 106, in other words, based on the twist amount of the torsion bar 112. A torque sensor 109 is provided as an example of torque detecting means for detecting the torque.

  Further, the steering device 100 includes an electric motor 110 supported by the steering gear box 107 and a speed reduction mechanism 111 that reduces the driving force of the electric motor 110 and transmits it to the pinion shaft 106. The speed reduction mechanism 111 includes, for example, a worm wheel (not shown) fixed to the pinion shaft 106, a worm gear (not shown) fixed to the output shaft of the electric motor 110, and the like. The electric motor 110 applies a driving force (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 includes a vehicle speed sensor 170 that detects a vehicle speed Vc, which is a moving speed of the vehicle, via a network (CAN) that performs communication for sending signals for controlling various devices mounted on the vehicle. The output signal from is input.

  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 generated torque of the electric motor 110 to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic 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 v obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal. The rotation angle signal θs from the resolver 120 is 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 the motor rotation speed Nm 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. A motor rotation speed calculation unit 72 to calculate, and a rudder angle calculation unit 73 as an example of a rudder angle detection unit that calculates a rudder angle Ra that is a rotation angle of the steering wheel 101 are provided.

First, the target current calculation unit 20 will be described in detail.
The target current calculation unit 20 is a basic target current calculation unit that calculates (sets) a basic target current Itf that is the basis of the target current It supplied to the electric motor 110 based on the torque signal Td and the vehicle speed signal v. A target current calculation unit 27 is provided. The target current calculation unit 20 is a rudder as an example of a correction current calculation unit that calculates a rudder angular velocity deviation current Iv that is a current for correcting the basic target current Itf according to a deviation between the target rudder angular velocity and the actual rudder angular velocity. An angular velocity deviation current calculation unit 28 and a target current determination unit 29 as an example of a target current determination unit that finally determines the target current It based on the basic target current Itf and the steering angular velocity deviation current Iv are provided. .
The basic target current calculation unit 27, the steering angular velocity deviation current calculation unit 28, and the target current determination 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 Nm of the electric motor 110 based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71.

  The steering angle calculation unit 73 (see FIG. 2) is configured such that the steering wheel 101, the speed reduction mechanism 111, and the like are mechanically coupled, so that the rotation angle (steering angle Ra) of the steering wheel 101 and the motor rotation angle θ of the electric motor 110 The steering angle Ra is calculated based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. The rudder angle calculation unit 73 steers based on the integrated value of the difference between the previous value and the current value of the motor rotation angle θ that is calculated periodically (for example, every 1 millisecond) by the motor rotation angle calculation unit 71, for example. The angle Ra is calculated.

FIG. 4 is a schematic configuration diagram of the basic target current calculation unit 27.
The basic target current calculation unit 27 calculates a base current calculation unit 21 that calculates a base current Ib that is 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. The basic target current calculation unit 27 determines a basic target current Itf based on the values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. 25. In addition, the basic target current calculation unit 27 includes a phase compensation unit 26 that compensates for the phase of the steering torque T detected by the torque sensor 109.
The target current calculation unit 20 receives a torque signal Td, a vehicle speed signal v, and the like.

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 calculates a base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170. That is, the base current calculation unit 21 calculates the base current Ib according to the phase-compensated steering torque T and the vehicle speed Vc. The base current calculation unit 21 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current that are created in advance based on empirical rules and stored in the ROM. The base current Ib is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map illustrated in FIG. 5 showing the correspondence with Ib.

  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. That is, the inertia compensation current calculation unit 22 calculates the inertia compensation current Is according to the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v). Note that the inertia compensation current calculation unit 22 generates, for example, the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the inertia compensation current Is, which are previously created based on empirical rules and stored in the ROM. The inertia compensation current Is is calculated by substituting the steering torque T (torque signal Ts) and the vehicle speed Vc (vehicle speed signal v) into the control map indicating the correspondence between the two.

  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 Nm of the electric motor 110. That is, the damper compensation current calculation unit 23 calculates the damper compensation current Id according to the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the motor rotation speed Nm of the electric motor 110. The damper compensation current calculation unit 23 generates, for example, the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the motor rotation speed Nm, which are previously created based on empirical rules and stored in the ROM. The damper compensation current Id is calculated by substituting the steering torque T (torque signal Ts), the vehicle speed Vc (vehicle speed signal v), and the motor rotation speed Nm into the control map indicating the correspondence with the damper compensation current Id.

  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.

Next, the rudder angular velocity deviation current calculation unit 28 will be described in detail.
FIG. 6 is a schematic configuration diagram of the rudder angular velocity deviation current calculation unit 28.
The steering angular velocity deviation current calculation unit 28 is based on a base steering angular velocity deviation current calculation unit 281 that calculates a base steering angular velocity deviation current Ivb that is a base of the steering angular velocity deviation current Iv, and a base steering angular velocity based on the axial force generated in the rack shaft 105. A rack axial force correction coefficient setting unit 282 that sets a rack axial force correction coefficient Kr that is a correction coefficient for correcting the base rudder angular velocity deviation current Ivb calculated by the deviation current calculation unit 281. Further, the rudder angular velocity deviation current calculation unit 28 is based on the base rudder angular velocity deviation current Ivb calculated by the base rudder angular velocity deviation current calculation unit 281 and the rack axial force correction coefficient Kr set by the rack axial force correction coefficient setting unit 282. And a steering angular velocity deviation current determining unit 283 for determining the steering angular velocity deviation current Iv.

First, the base rudder angular velocity deviation current calculation unit 281 will be described.
Based on the steering angle Ra calculated by the steering angle calculation unit 73 and the vehicle speed Vc detected by the vehicle speed sensor 170, the base steering angular speed deviation current calculation unit 281 calculates a target steering angular speed Vrt that is a target steering angular speed Vr. A target rudder angular velocity calculation unit 281a to be calculated and an actual rudder angular velocity calculation unit 281b to calculate an actual rudder angular velocity Vra that is an actual rudder angular velocity Vr are provided. The base rudder angular velocity deviation current calculation unit 281 calculates a rudder angular velocity deviation ΔVr that is a deviation between the target rudder angular velocity Vrt calculated by the target rudder angular velocity calculation unit 281a and the actual rudder angular velocity calculation unit 281b. And a base steering angular speed deviation current determination unit 281d that determines a base steering angular speed deviation current Ivb based on the steering angular speed deviation ΔVr calculated by the steering angular speed deviation calculation unit 281c.

FIG. 7 is a control map showing the correspondence between the steering angle Ra, the vehicle speed Vc, and the target steering angular speed Vrt.
The target rudder angular velocity calculation unit 281a calculates a target rudder angular velocity Vrt according to the rudder angle Ra calculated by the rudder angle calculation unit 73 and the vehicle speed Vc detected by the vehicle speed sensor 170. The target rudder angular velocity calculation unit 281a is, for example, a control map illustrated in FIG. 7 illustrating the correspondence between the rudder angle Ra, the vehicle speed Vc, and the target rudder angular velocity Vrt, which is previously created based on an empirical rule and stored in the ROM. Then, the target rudder angular velocity Vrt is calculated by substituting the rudder angle Ra and the vehicle speed Vc.

The actual rudder angular velocity calculation unit 281b calculates an actual rudder angular velocity Vra that is a change speed with respect to the actual rudder angle Ra based on the rudder angle Ra calculated by the rudder angle calculation unit 73. The actual rudder angular velocity calculation unit 281b calculates the actual rudder angular velocity Vra at the rudder angle Ra by performing time differentiation on the rudder angle Ra calculated by the rudder angle calculation unit 73.
The steering angular velocity deviation calculation unit 281c calculates the steering angular velocity deviation ΔVr by subtracting the actual steering angular velocity Vra calculated by the actual steering angular velocity calculation unit 281b from the target steering angular velocity Vrt calculated by the target steering angular velocity calculation unit 281a.

FIG. 8 is a control map showing the correspondence between the steering angular velocity deviation ΔVr and the base steering angular velocity deviation current Ivb.
The base rudder angular velocity deviation current determining unit 281d calculates a base rudder angular velocity deviation current Ivb corresponding to the rudder angular velocity deviation ΔVr calculated by the rudder angular velocity deviation calculating unit 281c. The base rudder angular velocity deviation current determining unit 281d, for example, is a control illustrated in FIG. 8 showing the correspondence between the rudder angular velocity deviation ΔVr and the base rudder angular velocity deviation current Ivb, which is previously created based on empirical rules and stored in the ROM. The base steering angular speed deviation current Ivb is calculated by substituting the steering angular speed deviation ΔVr into the map.

Next, the rack axial force correction coefficient setting unit 282 will be described.
As shown in FIG. 6, the rack axial force correction coefficient setting unit 282 is a reference rack shaft as an example of a reference rack axial force calculation unit that calculates a reference rack axial force Frm, which is a reference axial force generated in the rack shaft 105. A force calculation unit 282a and an actual rack axial force calculation unit 282b as an example of an actual rack axial force calculation unit that calculates an actual rack axial force Fra that is an actual axial force generated on the rack shaft 105 are provided. The rack axial force correction coefficient setting unit 282 is a rack axis that is a deviation between the standard rack axial force Frm calculated by the standard rack axial force calculation unit 282a and the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282b. A rack axial force deviation calculation unit 282c that calculates a force deviation ΔFr, and a base rack axial force correction coefficient Krb that is a base of the rack axial force correction coefficient Kr based on the rack axial force deviation ΔFr calculated by the rack axial force deviation calculation unit 282c. A base rack axial force correction coefficient setting unit 282d, a vehicle speed correction coefficient setting unit 282e for setting the vehicle speed correction coefficient Kv to correct the base rack axial force correction coefficient Krb based on the vehicle speed Vc, and a base rack axial force correction A rack axial force correction coefficient determination unit 282f that determines the rack axial force correction coefficient Kr based on the coefficient Krb and the vehicle speed correction coefficient Kv. ing.

  The reference rack axial force calculation unit 282a calculates a reference rack axial force Frm based on the steering angle Ra calculated by the steering angle calculation unit 73 and the vehicle speed Vc detected by the vehicle speed sensor 170. That is, the reference rack axial force calculation unit 282a calculates the reference rack axial force Frm according to the steering angle Ra and the vehicle speed Vc. The reference rack axial force calculation unit 282a is, for example, a control map or calculation indicating the correspondence between the rudder angle Ra and 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 angle Ra and the vehicle speed Vc into the equation.

The actual rack axial force calculation unit 282b 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 type 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 applied to the pinion shaft 106 Calculation is based on Tp. 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 from the driver via the steering wheel 101 and the motor torque Tm applied from the output shaft torque To of the electric motor 110 (Tp = T + Tm). .

The steering torque T can be grasped 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 the ROM in advance. 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.

  The rack axial force deviation calculation unit 282c subtracts the reference rack axial force Frm calculated by the reference rack axial force calculation unit 282a from the actual rack axial force Fra calculated by the actual rack axial force calculation unit 282b, thereby obtaining the rack axial force deviation ΔFr. Is calculated (ΔFr = Fra−Frm).

FIG. 9 is a control map showing the correspondence between the rack axial force deviation ΔFr and the base rack axial force correction coefficient Krb.
The base rack axial force correction coefficient setting unit 282d calculates a base rack axial force correction coefficient Krb corresponding to the rack axial force deviation ΔFr calculated by the rack axial force deviation calculation unit 282c. The base rack axial force correction coefficient setting unit 282d is, for example, shown in FIG. 9 showing the correspondence between the rack axial force deviation ΔFr and the base rack axial force correction coefficient Krb that has been previously created based on empirical rules and stored in the ROM. The base rack axial force correction coefficient Krb is calculated by substituting the rack axial force deviation ΔFr into the illustrated control map.

  In the control map shown in FIG. 9, the base rack axial force correction coefficient Krb increases as the rack axial force deviation ΔFr increases in the positive direction, in other words, as the actual rack axial force Fra is larger than the reference rack axial force Frm. It is set to increase in the positive direction. In the control map shown in FIG. 9, the base rack axial force correction coefficient Krb increases as the rack axial force deviation ΔFr increases in the negative direction, in other words, as the reference rack axial force Frm is larger than the actual rack axial force Fra. It is set to increase in the negative direction.

FIG. 10 is a control map showing the correspondence between the vehicle speed Vc and the vehicle speed correction coefficient Kv.
The vehicle speed correction coefficient setting unit 282e sets a vehicle speed correction coefficient Kv corresponding to the vehicle speed Vc. For example, the vehicle speed correction coefficient setting unit 282e sets the vehicle speed Vc on the control map illustrated in FIG. 10 that shows the correspondence between the vehicle speed Vc and the vehicle speed correction coefficient Kv, which is previously created based on an empirical rule and stored in the ROM. By substituting, the vehicle speed correction coefficient Kv is calculated.

  The rack axial force correction coefficient determination unit 282f is obtained by multiplying the base rack axial force correction coefficient Krb calculated by the base rack axial force correction coefficient setting unit 282d and the vehicle speed correction coefficient Kv calculated by the vehicle speed correction coefficient setting unit 282e. A value obtained by adding 1 to the obtained value is determined as the rack axial force correction coefficient Kr (Kr = 1 + Krb × Kv).

The rudder angular velocity deviation current determining unit 283 multiplies the base rudder angular velocity deviation current Ivb calculated by the base rudder angular velocity deviation current calculating unit 281 by the rack axial force correction coefficient Kr set by the rack axial force correction coefficient setting unit 282. Is determined as the steering angular velocity deviation current Iv (Iv = Ivb × Kr).
The steering angular velocity deviation current determining unit 283 stores the steering angular velocity deviation current Iv calculated by the above-described method in a storage area such as a RAM.

  Then, the target current determination unit 29 uses the basic target current Itf calculated by the basic target current calculation unit 27 and the steering angular velocity deviation current Iv calculated by the steering angular velocity deviation current calculation unit 28, which are stored in a storage area such as a RAM. The added value is determined as the target current It.

  In the target current calculation unit 20 according to the present embodiment configured as described above, the steering angular velocity deviation current Iv corresponding to the deviation between the target steering angular velocity Vrt and the actual steering angular velocity Vra is added to the target current It. . This steering angular velocity deviation current Iv is a current that takes into account the degree of reaction force from the road surface. When the reaction force from the road surface is small, the steering angular velocity deviation current Iv is small, and when the reaction force from the road surface is large, the steering Angular velocity deviation current Iv is set to be large.

  In addition, in the target current calculation unit 20 according to the present embodiment, the rack axial force correction coefficient Kr increases as the actual rack axial force Fra generated in the rack shaft 105 becomes larger than the reference rack axial force Frm. The target current It is increased by correcting the angular velocity deviation current Iv to be large. On the other hand, when the actual rack axial force Fra generated in the rack shaft 105 is smaller than the reference rack axial force Frm, the smaller the actual rack axial force Fra becomes smaller than the reference rack axial force Frm, the smaller the rack axial force correction coefficient Kr is in the minus direction. Since it becomes large, it correct | amends so that the steering angular velocity deviation electric current Iv may become small, and the target electric current It reduces.

Therefore, according to the target current calculation unit 20 according to the present embodiment, it is possible to set the value in consideration of the disturbance input when performing the control of adding the steering angular speed deviation current Iv in consideration of the reaction force degree from the road surface. it can. According to such a configuration, even when the disturbance input estimation becomes unstable and the rack axial force deviation ΔFr becomes an unstable output, such as when an irregular and continuous disturbance is input, the steering angular speed deviation current Iv increases or decreases. The effect of adding a correction current according to the deviation between the target rudder angular velocity Vrt and the actual rudder angular velocity Vra is only increased or decreased. Therefore, for example, the correction current is calculated according to the deviation between the actual rack axial force Fra and the normative rack axial force Frm, and compared with a case where the calculated correction current is added to the target current It, it is irregular and continuous. It is possible to suppress the deterioration of the steering feeling due to the input of a general disturbance.
As described above, according to the steering device 100 according to the present embodiment, it is possible to apply the assist force in consideration of the reaction force degree from the road surface while suppressing the deterioration of the steering feeling.

<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 basic target current calculation function for calculating a basic target current Itf that is a basis of the target current It supplied to the electric motor 110 based on the steering torque T of the steering wheel 101 of the vehicle. Based on the deviation between the target rudder angular velocity Vrt calculated based on the rudder angle Ra which is the rotation angle of the steering wheel 101 and the vehicle speed Vc which is the moving speed of the vehicle, and the actual rudder angular velocity (actual rudder angular velocity Vra). Based on the correction current calculation function for calculating the steering angular velocity deviation current Iv as an example of the correction current for correcting the current It, the basic target current Itf calculated by the basic target current calculation function, and the correction current calculated by the correction current calculation function A target current determining function for determining a target current, and the correction current calculating function is based on the steering angle Ra and the vehicle speed Vc. A reference rack axial force calculation function for calculating a reference rack axial force Frm, which is a reference for the axial force generated on the rack shaft 105 that rolls the rolling wheels, and an actual rack axial force Fra that is an actual axial force generated on the rack shaft 105. An actual rack axial force calculation function for calculating the reference rack axial force Frm calculated by the reference rack axial force calculation function and an actual rack axial force Fra calculated by the actual rack axial force calculation function. It can also be understood as a program that realizes changing the correction current.

  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 calculation part, 28 ... Steering angular velocity deviation current calculation part, 29 ... Target current determination part, 30 ... Control part, 100 ... Electric power steering device, 110 ... electric motor, 281 ... base rudder angular velocity deviation current calculation unit, 282 ... rack axial force correction coefficient setting unit, 283 ... rudder angular velocity deviation current determination unit

Claims (4)

An electric motor for applying an assisting force to the steering wheel of the vehicle;
Torque detecting means for detecting a steering torque of the steering wheel;
Rudder angle detecting means for detecting a rudder angle which is a rotation angle of the steering wheel;
Basic target current calculation means for calculating a basic target current that is the basis of the target current supplied to the electric motor based on the steering torque detected by the torque detection means;
Correction current calculation means for calculating a correction current for correcting the target current based on a deviation between a target steering angular speed according to the steering angle and vehicle speed detected by the steering angle detection means and an actual steering angular speed;
Target current determining means for determining the target current based on the basic target current calculated by the basic target current calculating means and the correction current calculated by the correction current calculating means;
With
The correction current calculation means includes
Based on the rudder angle detected by the rudder angle detecting means and the vehicle speed, normative rack axial force calculating means for calculating a normative rack axial force that serves as a norm for the axial force generated on the rack shaft that rolls rolling wheels;
An actual rack axial force calculating means for calculating an actual rack axial force which is an actual axial force generated on the rack shaft;
Have
Changing the correction current based on a deviation between the reference rack axial force calculated by the reference rack axial force calculating unit and the actual rack axial force calculated by the actual rack axial force calculating unit ;
An electric power steering apparatus characterized by suppressing deterioration of steering feeling due to input of irregular and continuous disturbances . The correction current calculation means calculates a correction coefficient set based on a deviation between the reference rack axial force and the actual rack axial force based on a deviation between the target rudder angular velocity and the actual rudder angular velocity. The electric power steering apparatus according to claim 1, wherein the correction current is calculated by multiplying a base correction current as a base. The electric power steering apparatus according to claim 1, wherein the correction current calculation unit changes the correction current based on the vehicle speed. On the computer,
A basic target current calculation function for calculating a basic target current that is a basis of a target current supplied to an electric motor based on a steering torque of a steering wheel of a vehicle;
A correction for calculating a correction current for correcting the target current based on a deviation between a target steering angular speed corresponding to a steering angle that is a rotation angle of the steering wheel and a vehicle speed that is a moving speed of the vehicle and an actual steering angular speed. Current calculation function,
A target current determination function for determining the target current based on the basic target current calculated by the basic target current calculation function and the correction current calculated by the correction current calculation function;
With
The correction current calculation function is
Based on the rudder angle and the vehicle speed, a reference rack axial force calculation function that calculates a reference rack axial force that is a reference for the axial force generated in the rack shaft that rolls the rolling wheels;
An actual rack axial force calculation function for calculating an actual rack axial force that is an actual axial force generated on the rack shaft;
Have
Changing the correction current based on a deviation between the reference rack axial force calculated by the reference rack axial force calculation function and the actual rack axial force calculated by the actual rack axial force calculation function ;
A program for realizing that the steering feeling is prevented from deteriorating due to the input of irregular and continuous disturbances .

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