JP2015189261A - Electric power steering device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of applying assist force on the basis of consideration of a degree of reaction force from a road surface while suppressing a decline in steering feeling.SOLUTION: An electric power steering device includes: a basic target current calculation section for calculating a basic target current that forms the basis of a target current to be supplied to an electric motor on the basis of steering torque; a steering angle speed deviation current calculation section 28 for calculating a steering angle speed deviation current for correcting the target current on the basis of a deviation between target steering angle speed set based on a steering angle and vehicle speed and actual steering angle speed; and a target current determination section for determining the target current on the basis of the basic target current and the steering angle speed deviation current. The steering angle speed deviation current calculation section 28 includes: a standard rack axial force calculation section 283a for calculating standard rack axial force that serves as a standard of axial force generated in a rack shaft on the basis of the steering angle and the vehicle speed; and an actual rack axial force calculation section 283b for calculating actual rack axial force that is actual axial force generated in the rack shaft. Based on a deviation between the standard rack axial force and the actual rack axial force, the target steering angle speed is set.

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 set based on the steering angle and vehicle speed detected by the means and an actual steering angular speed, and the basic target current The target current is determined based on the basic target current calculated by the calculation means and the correction current calculated by the correction current calculation means. A reference current determining means, and the correction current calculating means is a reference for the axial force generated in the rack shaft for rolling the rolling wheels based on the steering angle and the vehicle speed detected by the steering angle detection means; A reference rack axial force calculating means for calculating a reference rack axial force, and an actual rack axial force calculating means for calculating an actual rack axial force that is an actual axial force generated in the rack shaft, and the reference rack shaft In the electric power steering apparatus, the target rudder angular velocity is set based on a deviation between the reference rack axial force calculated by the force calculating means and the actual rack axial force calculated by the actual rack axial force calculating means. is there.

  Here, the correction current calculation means is based on the steering angle detected by the steering angle detection means and the vehicle speed based on a correction coefficient set based on a deviation between the reference rack axial force and the actual rack axial force. The target rudder angular speed may be set by multiplying the base target rudder angular speed that is the base of the set target rudder angular 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 for calculating a correction current for correcting the target current based on a deviation between a target rudder angular speed set based on a steering angle that is a rotation angle of a wheel and a vehicle speed that is a moving speed of the vehicle and an actual rudder angular speed A current calculation function, 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, The correction current calculation function calculates a reference rack axial force 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. A reference rack axial force calculation function, and an actual rack axial force calculation function that calculates an actual rack axial force that is an actual axial force generated on the rack shaft, and the reference rack axial force calculation function calculates A program for realizing setting of the target rudder angular velocity based on a deviation between a reference rack axial force and the actual rack axial force calculated by the actual rack axial force calculation function.

  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 rudder angle and a vehicle speed, and a base target rudder angular speed. It is a control map which shows a response | compatibility with a steering angular velocity deviation and a 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.

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 are detected. 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 rudder angular velocity deviation current calculation unit 28 is a base of a target rudder angular velocity Vrt that is a target rudder angular velocity Vr based on the rudder angle Ra calculated by the rudder angle calculation unit 73 and the vehicle speed Vc detected by the vehicle speed sensor 170. A base target rudder angular velocity calculation unit 281 that calculates a base target rudder angular velocity Vrb and an actual rudder angular velocity calculation unit 282 that calculates an actual rudder angular velocity Vra that is an actual rudder angular velocity Vr. Further, the rudder angular velocity deviation current calculation unit 28 is a rack axial force correction coefficient that is a correction coefficient for correcting the base target rudder angular velocity Vrb calculated by the base target rudder angular velocity calculation unit 281 based on the axial force generated in the rack shaft 105. Based on the rack axial force correction coefficient setting unit 283 that sets Kr, the rack axial force correction coefficient Kr set by the rack axial force correction coefficient setting unit 283, and the base target rudder angular velocity Vrb calculated by the base target rudder angular velocity calculation unit 281. And a target rudder angular speed setting unit 284 for setting the target rudder angular speed Vrt. The steering angular velocity deviation current calculation unit 28 calculates a steering angular velocity deviation ΔVr that is a deviation between the target steering angular velocity Vrt set by the target steering angular velocity setting unit 284 and the actual steering angular velocity Vra calculated by the actual steering angular velocity calculation unit 282. A steering angular speed deviation calculating unit 285 and a steering angular speed deviation current determining unit 286 that determines the steering angular speed deviation current Iv based on the steering angular speed deviation ΔVr calculated by the steering angular speed deviation calculating unit 285 are provided.

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

The actual rudder angular velocity calculation unit 282 calculates an actual rudder angular velocity Vra that is a change speed of the actual rudder angle Ra based on the rudder angle Ra calculated by the rudder angle calculation unit 73. The actual rudder angular velocity calculating unit 282 calculates the actual rudder angular velocity Vra by differentiating the rudder angle Ra calculated by the rudder angle calculating unit 73 with respect to time.
The rack axial force correction coefficient setting unit 283 and the target rudder angular velocity setting unit 284 will be described in detail later.
The steering angular velocity deviation calculation unit 285 calculates the steering angular velocity deviation ΔVr by subtracting the actual steering angular velocity Vra calculated by the actual steering angular velocity calculation unit 282 from the target steering angular velocity Vrt set by the target steering angular velocity setting unit 284.

FIG. 8 is a control map showing the correspondence between the steering angular speed deviation ΔVr and the steering angular speed deviation current Iv.
The steering angular speed deviation current determination unit 286 calculates a steering angular speed deviation current Iv corresponding to the steering angular speed deviation ΔVr calculated by the steering angular speed deviation calculation unit 285. The rudder angular velocity deviation current determining unit 286, for example, in the control map illustrated in FIG. The steering angular velocity deviation current Iv is calculated by substituting the steering angular velocity deviation ΔVr.

  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.

Next, the rack axial force correction coefficient setting unit 283 will be described.
As shown in FIG. 6, the rack axial force correction coefficient setting unit 283 is a normative rack shaft as an example of a normative rack axial force calculation unit that calculates a normative rack axial force Frm that is a normative axial force generated in the rack shaft 105. A force calculation unit 283a and an actual rack axial force calculation unit 283b 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 283 is a rack axis that is a deviation between the standard rack axial force Frm calculated by the standard rack axial force calculation unit 283a and the actual rack axial force Fra calculated by the actual rack axial force calculation unit 283b. A rack axial force deviation calculation unit 283c for calculating the force deviation ΔFr is provided. Further, the rack axial force correction coefficient setting unit 283 sets 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 283c. A base rack axial force correction coefficient setting unit 283d and a rack axial force correction coefficient determination unit 283e that determines the rack axial force correction coefficient Kr based on the base rack axial force correction coefficient Krb set by the base rack axial force correction coefficient setting unit 283d. And.

  The reference rack axial force calculation unit 283a 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 283a 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 283a is, for example, a control map or calculation indicating the correspondence between the steering 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 283b 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 283c subtracts the reference rack axial force Frm calculated by the reference rack axial force calculation unit 283a from the actual rack axial force Fra calculated by the actual rack axial force calculation unit 283b, thereby making 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 283d 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 283c. The base rack axial force correction coefficient setting unit 283d, for example, shows the correspondence between the rack axial force deviation ΔFr and the base rack axial force correction coefficient Krb that has been created based on empirical rules and stored in the ROM in advance, as shown in FIG. 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.

  The rack axial force correction coefficient determination unit 283e determines a value obtained by adding 1 to the base rack axial force correction coefficient Krb calculated by the base rack axial force correction coefficient setting unit 283d as the rack axial force correction coefficient Kr ( Kr = 1 + Krb).

  The target rudder angular velocity setting unit 284 is a value obtained by multiplying the rack axial force correction coefficient Kr set by the rack axial force correction coefficient setting unit 283 and the base target rudder angular velocity Vrb calculated by the base target rudder angular velocity calculation unit 281. Is set as the target rudder angular velocity Vrt (Vrt = Vrb × Kr).

  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. Therefore, in such a case, the target rudder angular velocity Vrt is set to be increased, the rack axial force deviation ΔFr is increased, the rudder angular velocity deviation current Iv is corrected to be increased, and the target current It is increased. 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. growing. Therefore, in such a case, the target rudder angular velocity Vrt is set to be small, the rack axial force deviation ΔFr is decreased, the rudder angular velocity deviation current Iv is corrected to be small, and the target current It is decreased.

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 set 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). 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 steering angular velocity deviation current Iv calculated by the correction current calculation function A target current determination function for determining the target current It based on the control angle, the correction current calculation function, the steering angle Ra and the vehicle Based on 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 in the rack shaft 105 that rolls the rolling wheels, and an actual axial force generated in the rack shaft 105. An actual rack axial force Fram 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 the setting of the target rudder angular velocity Vrt based on the deviation.

  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 target rudder angular velocity calculation unit, 282 ... actual rudder angular velocity calculation unit, 283 ... rack axial force correction coefficient setting unit, 284 ... target rudder angular velocity setting unit, 285 ... steer angular velocity deviation Calculation unit, 286 ... rudder angular velocity deviation current determination unit

Claims (3)

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 detection 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 set based on 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
The target rudder angular velocity is set 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. Power steering device. The correction current calculation means sets a correction coefficient set based on a deviation between the reference rack axial force and the actual rack axial force based on the steering angle and the vehicle speed detected by the steering angle detection means. The electric power steering apparatus according to claim 1, wherein the target rudder angular speed is set by multiplying a base target rudder angular speed that is a base of the target rudder angular 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 current for correcting the target current is calculated based on a deviation between a target steering angular speed set based on 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. Correction current calculation function to
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
A program for realizing setting of the target rudder angular velocity 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.

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