JP7136031B2 - steering control device - Google Patents

Description

The present invention relates to steering control devices.

Conventionally, in a steering control device for a steer-by-wire system, there has been proposed a technique of presenting a reaction force in consideration of ensuring the driver's ease of driving and steering feeling.

For example, in a vehicle steering system disclosed in Patent Document 1, a dead band is set for an angular reaction force calculated according to the steering wheel angle. Further, in the steer-by-wire steering system disclosed in Patent Document 2, the provisional target frictional reaction torque (Tthp) corresponding to the steering angle is calculated for each direction of change of the steering angle (θs). That is, the hysteresis characteristic is set in the reaction force characteristic according to the steering angle.

Japanese Patent Application Laid-Open No. 4135600 Japanese Patent No. 4186913

Behavior during steering of a vehicle includes non-linear behavior such as when a tire is twisted and then moves while rubbing against a road surface. In presenting a reaction force to the driver in a steer-by-wire system, it is desirable to present a reaction force that reflects such nonlinear behavior, or to present a difference in reaction force due to hysteresis when turning and when steering back. However, from the viewpoint of vehicle-like reaction force presentation, the prior arts of Patent Documents 1 and 2 are not sufficient.

SUMMARY OF THE INVENTION The present invention has been created in view of the above points, and an object of the present invention is to provide a steering control device capable of presenting a vehicle-like reaction force in a reaction force device for a steer-by-wire system.

A steering control device of the present invention is a steering control device for controlling a reaction force device and a steering device in a steer-by-wire system (90) including a reaction force device (70) and a steering device (80). The reaction device includes a reaction rotating electric machine (78) and a reaction power converter (77) for driving the reaction rotating electric machine, and is connected to a steering wheel (91). The steering device includes a steering rotating electric machine (88) and a steering electric power converter (87) that drives the steering rotating electric machine, and steers the wheels (99). The steering control device controls the reaction device and the steering device so that the angle (θt) of the steering device matches the angle (θr) of the reaction device.

This steering control device has a reaction force control section (510), a reference angle calculation section (561), a cut-back determination section (410), and a response torque command calculation section (570). The reaction force control unit calculates a steering torque command value (T ^* st) based on physical quantities (Tt, T ^* t, It, I ^* t) corresponding to the output torque of the steering device.

The reference angle calculator calculates a reference angle (θref) according to changes in steering wheel angle equivalent values (θr, θt) corresponding to the angle of the steering wheel. A cutting and turning back determining part distinguishes between a "cutting state" in which the steering wheel is turned away from the reference angle and a "turning back state" in which the steering wheel is turned back toward the reference angle.

The response torque command calculation unit responds to the displacement amount (Δθ) of the steering wheel angle equivalent value from the reference angle. A steering-back reaction force command value Trf(R) is calculated. In addition, the response torque command calculation section calculates a response torque command (Tresp) based on at least the reaction force command value for turning or the reaction force command value for turning back.

When the absolute value of the displacement (|Δθ|) is greater than a predetermined displacement threshold (Δθth), the reference angle calculator calculates a value equivalent to the steering wheel angle such that the absolute value of the displacement is equal to or less than the displacement threshold. Update the reference angle accordingly.

The response torque command calculation unit calculates a reaction force command value for cutting and a reaction force command value for steering back using a map or a formula. In this map or formula, the rate of change of the cutting reaction force command value with respect to the displacement amount is set so that the absolute value decreases as the distance from the reference angle increases. The rate of change of the steering-back reaction force command value with respect to the displacement amount is set so that the absolute value increases with increasing distance from the reference angle.

The steering control device of the present invention calculates a reference angle according to the angle change up to that point at each position during steering, and calculates a reaction force command value based on the amount of displacement from the reference angle. Also, the characteristics of the reaction force command value with respect to the displacement amount are made different between when turning in and when turning back. Specifically, when turning, the rise of the reaction torque at the start of cutting from the reference angle is increased, and when turning back, the fall of the reaction torque at the start of returning to the reference angle is increased. As a result, in the reaction force device of the steer-by-wire system, it is possible to present a vehicle-like reaction force that reflects non-linear behavior such as tire rubbing, hysteresis of turning back and forth, and the like.

1 is an overall configuration diagram of a steer-by-wire system to which a steering control device of each embodiment is applied; FIG. FIG. 2 is a schematic configuration diagram of a two-system reaction force device and a steering device; FIG. 2 is a block diagram showing a schematic configuration of a steering device control section; FIG. 2 is a block diagram showing a schematic configuration of a reaction force device control section; FIG. 2 is a control block diagram of the steering control device of the first embodiment; 5 is a flowchart of reference angle calculation of the first embodiment (first reference angle calculation of the second embodiment); 4 is a time chart of reference angle calculation according to the first embodiment; FIG. 5 shows (a) a (first) reaction force command value map for cutting, and (b) a (first) reaction force command value map for turning back. 4 is a flowchart of estimated road load calculation; FIG. 5 shows (a) a road load gain map and (b) a vehicle speed sensitive gain map. FIG. 5 is a block diagram of a cut switchback determination calculation according to a modified example of the first embodiment; FIG. 4 is a block diagram of a distribution ratio calculation of reaction force command values for cutting/returning; The control block diagram of the steering control apparatus of 2nd Embodiment. 9 is a flowchart of second reference angle calculation according to the second embodiment; Time charts of first and second reference angle calculations in the second embodiment. FIG. 13 shows (a) a second reaction force command value map for cutting, and (b) a second reaction force command value map for turning back. The control block diagram of the steering control device of 3rd Embodiment. FIG. 17 shows (a) a current limit value map for cutting and (b) a current limit value map for switchback. The control block diagram of the steering control apparatus of 4th Embodiment. 14 is a flowchart of reference angle calculation according to the fourth embodiment; Angle-torque transition diagrams for explaining effects when (a) one reference angle is used and (b) two reference angles are used.

As used herein, "embodiment" means an embodiment of the present invention. A plurality of embodiments of the steering control device of the present invention will be described below with reference to the drawings. This steering control device is a device that controls a reaction device and a steering device in a steer-by-wire system. In multiple embodiments, substantially the same configurations or substantially the same steps in the flowcharts are denoted by the same reference numerals or step numbers, and descriptions thereof are omitted. The following first to fourth embodiments will be collectively referred to as "this embodiment".

FIG. 1 shows the overall configuration of a steer-by-wire system 90 in which the steering mechanism and the steering mechanism are mechanically separated. In FIG. 1, only one side of the wheel 99 is illustrated, and the illustration of the wheel on the opposite side is omitted. The steer-by-wire system 90 includes a reaction force device 70 , a steering device 80 and a torque sensor 94 .

The reaction device 70 includes a reaction rotating electric machine 78 , a reaction power converter 77 that drives the reaction rotating electric machine 78 , and a reaction reduction gear 79 that reduces the output of the reaction rotating electric machine 78 . and is connected to a steering wheel 91 via a steering shaft 92 . The steer-by-wire system 90 does not allow the driver to directly sense the steering reaction force. Therefore, the reaction rotating electric machine 78 rotates the steering wheel 91 so as to apply a reaction force to the steering, thereby giving the driver an appropriate steering feeling.

The steering device 80 includes a steering rotating electrical machine 88, a steering power converter 87 that drives the steering rotating electrical machine 88, and a steering reduction gear 89 that reduces the output of the steering rotating electrical machine 88. including. Rotation of the steering rotary electric machine 88 is transmitted from the steering reduction gear 89 to the wheels 99 via the pinion gear 96 , the rack shaft 97 , the tie rod 98 and the knuckle arm 985 . Specifically, the rotational motion of the pinion gear 96 is converted into the linear motion of the rack shaft 97, and the tie rods 98 provided at both ends of the rack shaft 97 reciprocate the knuckle arms 99, thereby steering the wheels 99.

The torque sensor 94 detects the driver's steering input applied to the steering shaft 92 based on the torsional displacement of the torsion bar. Detected value T_sns of torque sensor 94 is input to steering control device 200 .

The steering angle of the steering wheel 91 is defined, for example, as positive in the CW direction and negative in the CCW direction in FIG. Correspondingly, the positive and negative of the steering angle of the wheels 99 are defined. Angular velocity is defined with the same sign as angle. Also, the detected value T_sns of the torque sensor 94 when the driver turns the steering wheel 91 in the CW direction is positive.

Furthermore, the output torque of the reaction force device 70 when the steering wheel 91 is turned in the CW direction by the reaction force device 70 is also positive. If the driver holds the steering wheel 91 while the output torque of the reaction force device 70 is acting in the CW direction, the driver applies torque in the CCW direction, so the detected value T_sns of the torque sensor 94 becomes negative.

The steering control device 200 is mainly composed of a microcomputer or the like, and includes therein a CPU, ROM, RAM, I/O (none of which are shown), bus lines connecting these components, and the like. Each process of the steering control device 200 may be software processing by executing a program stored in advance in a substantial memory device such as a ROM (that is, a readable non-temporary tangible recording medium) by the CPU. , hardware processing by a dedicated electronic circuit.

As shown in FIG. 1, in this embodiment, the reaction force device control section 270 and the steering device control section 280 are provided in a physically separated state. The two control units 270 and 280 cooperate to function as the steering control device 200 by communicating information with each other via a vehicle network such as CAN communication or a dedicated communication line.

For example, as indicated by a two-dot chain line, the reaction device 70 is integrally configured with a reaction device control section 270, a reaction power converter 77, and a reaction rotary electric machine 78. As shown in FIG. Similarly, the steering device 80 is configured integrally with a steering device control unit 280, a steering power converter 87, and a steering rotary electric machine 88. As shown in FIG. Such a so-called "integrated electromechanical" motor structure is well known in the field of electric power steering systems.

Next, with reference to FIG. 2, specific configurations of the power converters 77, 87 and the rotating electrical machines 78, 88 in the reaction force device 70 and the steering device 80 will be described. Since the reaction force device 70 and the steering device 80 have the same configuration, the reference numerals in the drawing are used together. In the following description, descriptions of "for reaction force" and "for steering" are omitted, and the reference numerals of the components of the reaction force device 70 are used as representatives. Regarding the steering device 80, the reference numerals will be read and interpreted.

The rotary electric machine 78 of this embodiment is a two-system three-phase brushless motor, and the power converter 77 is a two-system three-phase inverter. The rotary electric machine 78 has a first system winding 781 and a second system winding 782 as two systems of windings. The windings 781 and 782 of the two systems are arranged with their phases shifted by an electrical angle of 30 [deg], for example. The torque Tm output by the rotating electric machine 78 is a combination of the first system torque Tm1 generated by energizing the first system winding 781 and the second system torque Tm2 generated by energizing the second system winding 782. total value.

The power converter 77 includes a first system power converter 771 that energizes the first system winding 781 and a second system power converter 772 that energizes the second system winding 782 . In the example of FIG. 2, the two-system power converters 771 and 772 respectively convert the DC power supplied from the common battery 11 into three-phase AC power. Alternatively, each power converter 771, 772 may be connected to a separate battery.

Next, with reference to FIGS. 3 and 4, schematic configurations of the reaction force device control section 270 and the steering device control section 280 will be described. In this part, before describing the detailed control configuration of each embodiment, the basic configuration and unique configuration of the reaction force device 70 and steering device 80 common to each embodiment will be described. The symbol of the parameter related to the output of the reaction force device 70 is denoted by "r", and the symbol of the parameter related to the output of the steering device 80 is denoted by "t". Hereinafter, descriptions of reference numerals "70" and "80" of the reaction force device 70 and the steering device 80 will be omitted as appropriate.

3 and 4, the values of the angle θr and the angular velocity ωr of the reaction force device, the angle θt of the steering device, etc. are converted by multiplying and dividing the rotation angle of the rotary electric machines 78 and 88 by the reduction ratio of the reduction gears 79 and 89. be the value of First, FIG. 3 shows the basic configuration of the steering device control section 280. As shown in FIG. The angle θr of the reaction force device is input to the angle ratio control section 320 via the bandpass filter (“BPF” in the drawing) 31 . The angle ratio control unit 320 calculates the angle ratio between the reaction force device 70 and the steering device 80 according to the angle θr and the vehicle speed V. FIG.

A deviation calculation unit 361 of the angle control unit 360 calculates an angle deviation Δθ _rt between a value obtained by multiplying the angle θr of the reaction device by an angle ratio and the angle θt of the steering device. The PID controller ₃₆₂ ^adjusts the steering torque command value T ^* t or the current command value I ^* Compute t. The steering device current control unit 380 includes a deviation calculator 381 and a PI controller 382, and controls the current to be supplied to the steering rotary electric machine 88 by feedback control of the steering torque Tt or the current It.

Incidentally, the angular deviation Δθ calculated by the deviation calculator 361 is precisely the difference between “the value obtained by multiplying the angle θr of the reaction device by the angle ratio” and the angle θt of the steering device. However, in this specification, "the value obtained by multiplying the angle θr of the reaction device by the angle ratio" is regarded as the "angle θr of the reaction device", and the "deviation between the angle θr of the reaction device and the angle θt of the steering device ” is referred to as “angular deviation Δθ _rt ”. In short, it is usually possible to compare the angle .theta.r of the reaction device and the angle .theta.t of the steering device using a value obtained by multiplying and dividing the conversion factor. On this premise, it is interpreted that "the steering control device 200 controls the reaction device 70 and the steering device 80 so that the angle θt of the steering device matches the angle θr of the reaction device”.

FIG. 4 shows the basic configuration of the reaction force device control section 270. As shown in FIG. The reaction force control unit 510 calculates the steering torque command value T ^* st based on the "physical quantity corresponding to the output torque of the steering device" and the vehicle speed V. The "physical quantity corresponding to the output torque of the steering device" corresponds to the steering torque Tt, the steering torque command value T ^* t, and the current It or the current command value I ^* t flowing through the rotary electric machine 88 for steering. Hereinafter, the "physical quantity equivalent to the output torque of the steering device" is also abbreviated as "amount equivalent to the steering torque".

An adder 556 adds the response torque command Tresp to the sign-inverted value (-T ^* st) of the steering torque command value T ^* st. Generally, in the reaction force device 70 of the steer-by-wire system 90, the viscosity command value, the inertia command value, the return command value, the end command value, etc., are the sign-inverted value of the steering torque command value T ^* st (-T ^* st ) may be added to Descriptions of other command values are omitted in this specification.

The value after addition by adder 556 is input to steering wheel torque control unit 620 as target value T ^** st based on steering torque command value T ^* st. Based on the target value T ^** st, that is, based on the steering torque command value T ^* st and the response torque command Tresp, the steering wheel torque control unit 620 adjusts the torque command value of the reaction device (hereinafter referred to as the "reaction torque command value"). ) Calculate T ^* r.

A deviation calculator 621 of the steering wheel torque controller 620 calculates a torque deviation ΔT between the target value T ^** st and the detected value T_sns of the torque sensor 94 . PID controller 622 performs PID control so that torque deviation ΔT approaches zero. In this manner, steering wheel torque control unit 620 calculates reaction force torque command value T ^* r by servo control such that detection value T_sns of torque sensor 94 follows target value T ^** st. The reaction force device current controller 680 includes a deviation calculator 681 and a PI controller 682 . The reaction force device current control unit 680 controls the current to be supplied to the reaction force rotary electric machine 78 based on the reaction force torque command value T ^* r by feedback control of the reaction force torque Tr or the current Ir.

Further, the reaction force device control section 270 of the steering control device 200 of the present embodiment has a cut switchback determination section 410, a reference angle calculation section 561, and a response torque command calculation section 570 as unique configurations. Before explaining the configuration, the terms "steering wheel angle equivalent value" and "steering wheel angular velocity equivalent value" will be explained.

In this specification, the term “steering wheel angle equivalent value” includes the “reaction device angle θr” and the “steering device angle θt” that correlate with the steering angle of the steering wheel 91 . As described above, the angle θr of the reaction force device and the angle θt of the steering device are basically converted values obtained by multiplying and dividing the reduction ratios of the reduction gears 79 and 89, but the angle of the steering wheel 91 is used as a reference. is treated as the "steering wheel angle equivalent value". In the following text, "θr" is used as a representative symbol of the value equivalent to the steering wheel angle, and is written as "value equivalent to the steering wheel angle θr". In the figure, it is written like "θr (or θt)".

Further, in this specification, the "steering angle velocity", which is the time differential value of the steering wheel angle equivalent value, includes the "reaction device angular velocity ωr" and the "steering device angular velocity ωt" that are correlated with the steering angular velocity of the steering wheel 91. wheel angular velocity equivalent value”. In the following text, "ωr" is used as a representative symbol of the steering wheel angular velocity equivalent value, and is written as "steering wheel angular velocity equivalent value ωr". In the figure, it is written as "ωr (or ωt)".
Note that the "steering wheel angular velocity equivalent value" may be expressed in units of angular velocity [deg/s] or may be expressed in units of revolutions [rpm].

Returning to the description of the configuration of FIG. The reference angle calculator 561 calculates the reference angle θref according to the change in the “steering wheel angle equivalent value”. In this embodiment, in the steer-by-wire system 90, the driver is presented with a reaction force reflecting non-linear behavior, such as when the tire moves while rubbing against the road surface after being twisted, or when the rubber bush, suspension, etc. act elastically. Therefore, the concept of "reference angle θref" is used. The details of the reference angle calculation by the reference angle calculator 561 will be described later.

Response torque command calculator 570 acquires reference angle θref and steering wheel angle equivalent value θr. Hereinafter, the amount of displacement of the steering wheel angle equivalent value .theta.r from the reference angle .theta.ref is defined as "the amount of displacement .DELTA..theta.(=.theta.r-.theta.ref)." Based on the displacement amount Δθ, the response torque command calculation unit 570 calculates a “cutting reaction force command value Trf (F)” corresponding to the cutting state and a “returning reaction force command value Trf (F)” corresponding to the turning back state. (R)” is calculated.

Further, the response torque command calculation unit 570 calculates a “response torque command Tresp” based on at least the reaction force command value Trf(F) for turning or the reaction force command value Trf(R) for turning back. In the present embodiment, the reference angle used to calculate the reaction force command value is not fixed, and the reference angle θref calculated according to the change in the steering wheel angle equivalent value θr is used, so that the actual vehicle behavior Realization of reaction force presentation that reflects

The steering wheel 91 is turned away from the reference angle θref, and the steering wheel 91 is turned back toward the reference angle θref. to discriminate. For example, in the configuration shown in FIG. 11, the cutting-back switching determination unit 410 performs cutting-back switching determination calculation based on the displacement amount Δθ of the steering wheel angle equivalent value θr from the reference angle θref and the steering wheel angular velocity equivalent value ωr.

Accordingly, FIG. 4 shows a configuration in which the steering wheel angle equivalent value θr, the reference angle θref, and the steering wheel angular velocity equivalent value ωr are acquired by the cutting/return determination section 410 . However, without being limited to this configuration, the turning state and the turning-back state may be determined by a combination of signs of the steering angle, the steering angular velocity, and the steering torque.

The response torque command calculation unit 570 makes the characteristic of the reaction force command value with respect to the displacement amount Δθ different between the cutting state and the turning back state based on the determination result of the cutting and returning determination unit 410 . As a result, in the steer-by-wire system 90, it is possible to present to the driver the difference in the reaction force due to the hysteresis when turning and when steering back. In addition to the control of "switching between two values", "to make the characteristics of the reaction force command value different" includes the control of "changing continuously or stepwise, including the intermediate value of the two values". . The details will be described later.

Next, the description of each embodiment will be described. Reference numerals of the steering control devices of the first to fourth embodiments are "201" to "204", respectively. The block diagram of each embodiment shows the reaction force device control section 270 up to the point where the response torque command Tresp is input to the adder 556 and the target value T ^** st of the steering torque command value is calculated. The control configuration from the steering wheel torque control unit 620 conforms to FIG.

(First embodiment)
First, the steering control device 201 of the first embodiment will be described with reference to FIGS. 5 to 10. FIG. As shown in FIG. 5, the steering control device 201 of the first embodiment has a reference angle calculation unit 561, a response torque command calculation unit 570, and a cut-back determination unit 410 as components of the reaction force device control unit 270. . While the second embodiment uses two reference angles θref1 and θref2, the first embodiment uses one reference angle θref.

Reference angle calculation by the reference angle calculator 561 will be described with reference to the flowchart of FIG. 6 and the time chart of FIG. In the description of the flow charts below, the symbol "S" means a step. It should be noted that FIG. 6 is commonly referred to as a flowchart of the "first reference angle calculation" of the second embodiment, in which case the symbols of "θref" and "Δθth" in each step are replaced with "θref1" and "Δθth1". be replaced. The case of "reference angle calculation" in the first embodiment is described outside the parentheses, and the case of "first reference angle calculation" in the second embodiment is described in parentheses.

The initial value of the reference angle .theta.ref is 0 or the steering wheel angle equivalent value .theta.r at startup. The displacement amount threshold value Δθth is defined as the upper limit of the absolute value |Δθ| of the displacement amount Δθ of the steering wheel angle equivalent value θr from the reference angle θref. In S11 of FIG. 6, it is determined whether the steering wheel angle equivalent value .theta.r is greater than the sum of the reference angle .theta.ref and the displacement threshold value .DELTA..theta.th, that is, whether the formula (1.1) holds.
.theta.r>.theta.ref+.DELTA..theta.th (1.1)

If YES in S11, in S13 the reference angle calculator 561 updates the reference angle θref to a value obtained by subtracting the displacement amount threshold value Δθth from the steering wheel angle equivalent value θr, that is, “θr−Δθth”. If NO in S11, the process proceeds to S12. In S12, it is determined whether the steering wheel angle equivalent value .theta.r is greater than the value obtained by subtracting the displacement threshold value .DELTA..theta.th from the reference angle .theta.ref, that is, whether equation (1.2) holds.
θr<θref−Δθth (1・2)

If YES in S12, in S14 the reference angle calculator 561 updates the reference angle θref to a value obtained by adding the displacement amount threshold Δθth to the steering wheel angle equivalent value θr, that is, “θr+Δθth”. If NO in S12, the reference angle θref is maintained at the previous value in S15.

Formulas (1.1) and (1.2) are summarized as formula (1.3). That is, when the absolute value of the displacement |Δθ| is larger than the displacement threshold Δθth, the reference angle calculator 561 calculates the steering wheel angle equivalent value so that the absolute value of the displacement |Δθ| is equal to or smaller than the displacement threshold Δθth. The reference angle θref is updated according to θr.
|Δθ|=|θr−θref|>Δθth

After the reference angle θref is updated in S13 or S14, the process may be terminated as indicated by the dashed line, or steps S16 and S17 may be further performed. In S16, it is determined whether or not the cutting state has changed to the return state. If YES in S16, in S17 the displacement amount threshold value Δθth is reduced from the value in the cutting state, and the reference angle θref is updated based on the displacement amount threshold value Δθth.

Next, refer to the time chart in FIG. A thick solid line indicates the steering wheel angle equivalent value θr, and a thick dashed line indicates the reference angle θref. A thick one-dot chain line indicates a map value θ _MAP for reference of the displacement amount threshold Δθth. Step numbers S11 to S14 in the description correspond to FIG. Note that S16 and S17 in FIG. 6 are not reflected in FIG. 7, but are reflected in FIG. 15 of the second embodiment.

The steering wheel angle equivalent value θr reciprocates between the upper limit position and the lower limit position, that is, between the positive and negative ends in a triangular wave shape at a substantially constant speed. The map value θ _MAP changes in a trapezoidal waveform while maintaining constant values at the upper and lower limits for a predetermined period. The period during which the map value θ _MAP goes from 0 to the upper or lower limit and the period during which it is maintained at the upper or lower limit is the cutting period, and the period during which the map value θ _MAP returns from the upper or lower limit to 0 is the cut period. This is the switchback period.

At the initial stage t0, the steering wheel angle equivalent value .theta.r is 0 (that is, the neutral position), and the reference angle .theta.ref is also set to 0. The reference angle θref is maintained at 0 from the initial time t0 until the time ta when the map value _θMAP reaches the upper limit. The map value θ _MAP is constant at the upper limit value during the cut period from time ta to time tb when the steering wheel angle equivalent value θr reaches the upper limit end. During this period, the reference angle θref gradually increases with the steering wheel angle equivalent value θr due to the processing of S13 based on the YES determination in S11. The map value θ _MAP starts decreasing from time tb, crosses zero at time tc, and reaches the lower limit at time td. During this period, the reference angle θref is maintained at a constant value by the processing of S15 based on the NO judgments of S11 and S12.

The map value θ _MAP is constant at the lower limit value from time td to time te when the steering wheel angle equivalent value θr reaches the lower limit end. During this period, the reference angle θref gradually decreases with the steering wheel angle equivalent value θr due to the processing of S14 based on the YES determination in S12. The map value θ _MAP starts increasing from time te, crosses zero at time tf, and reaches its upper limit at time tg. During this period, the reference angle θref is maintained at a constant value by the processing of S15 based on the NO judgments of S11 and S12.

From time tg until time th when the steering wheel angle equivalent value θr reaches the upper limit end, the map value θ _MAP is constant at the upper limit value. During this period, the reference angle θref gradually increases with the steering wheel angle equivalent value θr due to the processing of S13 based on the YES determination in S11.

Returning to FIG. 5, the configuration of the reaction force calculation section 571 in the response torque command calculation section 570 of the first embodiment will be described. The reaction force calculator 571 has a cutting reaction force calculator 573F, a steering-back reaction force calculator 573R, and a switch 576, and calculates a cutting reaction force command value Trf(F) and a steering-back reaction force command. Switch between two values of the value Trf(R). However, in an intermediate state between the turning-in state and the turning-back state, it is more preferable to use the average value of the map or an added value according to the "state quantity σ" described later as a modified example as the torque command. This point also applies to the following embodiments.

The cutting reaction force calculator 573F stores in advance a cutting reaction force command value map that defines the relationship between the displacement amount Δθ and the cutting reaction force command value Trf(F). The steering-back reaction force calculator 573R stores in advance a steering-back reaction force command value map that defines the relationship between the displacement amount Δθ and the steering-back reaction force command value Trf(R). The reaction force calculators 573F and 573R use these maps to calculate the reaction force command values Trf(F) and Trf(R).

In the cutting reaction force command value map shown in FIG. 8A, the rate of change of the cutting reaction force command value Trf(F) with respect to the displacement amount Δθ is set so that the absolute value decreases as the distance from the reference angle θref increases. ing. Therefore, when cutting, the rise of the reaction torque at the start of cutting from the reference angle θref is large, and the change is small at a position away from the reference angle θref.

In the steering-back reaction force command value map shown in FIG. 8B, the rate of change of the steering-back reaction force command value Trf(R) with respect to the displacement amount Δθ is such that the absolute value increases as the distance from the reference angle θref increases. is set. Therefore, when the steering wheel is returned, the fall of the reaction torque at the start of returning to the reference angle θref becomes large, and the change becomes small at a position away from the reference angle θref. 8A and 8B are commonly referred to as the configuration of the first reaction force command section 571 of the second embodiment. In that case, as in FIG. 6, the symbols in parentheses correspond.

The switch 576 switches between the cutting reaction force command value Trf(F) and the turning back reaction force command value Trf(R) based on the signal from the cutting/returning determination unit 410 and outputs it. The output of the switch 576 of the reaction force calculator 571 may be directly input to the adder 556 to calculate the target value T ^** st of the steering torque command value. However, in the configuration shown in FIG. 5, the output of the reaction force calculator 571 is further multiplied by the road surface load gain Krs and the vehicle speed gain Kv to calculate the final response torque command Tresp. Therefore, the output of the reaction force calculation unit 571 is described as "primary response torque command Tresp_p" for distinction.

In addition to a reaction force calculator 571, the response torque command calculator 570 shown in FIG. 595. The estimated road load calculation unit 591 calculates an estimated road load based on the steering torque equivalent amount. The flowchart of FIG. 9 shows the estimated road load calculation by the road load gain calculator 592 . Here, the average current Iave is used as the physical quantity reflecting the estimated road load. The initial value of the average current Iave is 0 or the current It when the steering device 80 is started, and "a" is a dimensionless number between 0 and 1.

In S31, it is determined whether or not the absolute value |θref| of the reference angle is greater than a predetermined value A. If YES in S31, in S32, the current value of the average current Iave is updated according to Equation (2) based on the previous value of the average current Iave and the current It of the steering device. If NO in S31, the average current Iave is maintained at the previous value.
Iave=a×Iave+(1−a)×It (2)

The road load gain calculator 592 calculates the road load gain Krs according to the average current Iave. As shown in the road load gain map of FIG. 10(a), the road load gain Krs is set such that the absolute value of the rate of change with respect to the average current Iave decreases as the absolute value of the average current Iave increases.

A vehicle speed sensitive gain calculator 593 calculates a vehicle speed gain Kv according to the vehicle speed V. FIG. As shown in the vehicle speed gain map of FIG. 10(b), the vehicle speed gain Kv is constant at 1 in the low speed range, decreases as the vehicle speed V increases in the medium speed range, and becomes 0 in the high speed range. A first multiplier 594 and a second multiplier 595 sequentially multiply the primary response torque command Tresp_p by the road load gain Krs and the vehicle speed gain Kv to calculate the response torque command Tresp.

Thus, the response torque command calculation unit 570 configured in FIG. 5 changes the primary response torque command Tresp_p calculated by the reaction force calculation unit 571 based on the reaction force command value Trf, according to the road load and vehicle speed. As a result, it is possible to present a vehicle-like reaction force according to the road surface load and vehicle speed. Although not shown in FIGS. 13, 17, and 19 of the second to fourth embodiments, as in FIG. 5, the configuration for changing the response torque command Tresp by the road load gain Krs and the vehicle speed gain Kv is appropriately combined. may

(Modified example of the first embodiment)
Next, with reference to FIG. 11 and FIG. 12, the cutting switchback determination calculation according to the modified example of the first embodiment will be described. Since the switch 576 shown in FIG. 5 switches between the two states of the steering state and the steering back state, the characteristics change discontinuously when the steering state is switched. On the other hand, in the modified example, the characteristics are switched via the intermediate state or the steering holding state by using the "state quantity σ" that continuously or stepwise indicates the steering state from the turning state to the returning state.

For example, when the state quantity σ is set in the range of -1 to 1, dividing the entire range into the resolution levels of the arithmetic unit means "continuous". Means "gradual". Strictly speaking, since even the resolution level is a finite number, it can be said to be "stepwise", but the maximum number of steps included in practical "stepwise" is should be interpreted.

As shown in FIG. 11 , a cut-back determination unit 410 of the modification includes a displacement amount sensitivity map 411 , an angular velocity sensitivity amount map 412 and a multiplier 413 . The displacement amount response map 411 takes the displacement amount Δθ (=θr−θref) as an argument and calculates the displacement amount response σ _Δθ which is a dimensionless number between −1 and 1. In the region where the displacement Δθ is negative, the displacement sensitivity σ _Δθ gradually increases from −1 to 0 as the displacement Δθ approaches zero. In the region where the displacement Δθ is positive, the displacement sensitivity σ _Δθ gradually increases from 0 to 1 as the displacement Δθ increases from 0.

The angular velocity response map 412 uses the angular velocity ωr of the reaction device or the angular velocity ωt of the steering device, which is the "value equivalent to the steering wheel angular velocity", as an argument, and calculates the angular velocity response σω, which is a dimensionless number between -1 and 1. do. In the following text, only "ωr" is used as the sign of angular velocity. In the region where the angular velocity ωr is negative, the angular velocity sensitivity σω gradually increases from −1 to 0 as the angular velocity ωr approaches zero. In the region where the angular velocity ωr is positive, the angular velocity sensitivity σω gradually increases from 0 to 1 as the angular velocity ωr increases from 0. A multiplier 413 multiplies the displacement response amount σ _Δθ and the angular velocity response amount σω to calculate the state quantity σ. The state quantity σ indicates a cutting state when σ=1, and indicates a steering back state when σ=−1. In addition, when -1<σ<1, it indicates an intermediate state or a held steering state.

As shown in FIG. 12, the reaction force calculation unit 571 calculates the primary response torque command Tresp_p by calculating the distribution ratio based on the state quantity σ. 12 has a state quantity converter 574S, distribution ratio multipliers 574F and 574R, and a distribution value adder 575 instead of the switch 576 in the configuration shown in FIG. Other configurations of the cutting reaction force calculator 573F and the steering-back reaction force calculator 573R are the same as those in FIG. 5, so description thereof will be omitted.

The state quantity converter 574S calculates a cutting allocation value “(1+σ)/2” and a steering back allocation value “(1−σ)/2”. When σ=1 in the cutting state, the cutting distribution value is 1 and the steering back distribution value is 0. When σ=−1 in the return state, the cut distribution value is 0 and the return distribution value is 1. The cutting side distribution ratio multiplier 574F multiplies the cutting reaction force command value Trf(F) by the cutting distribution value. The return-side distribution ratio multiplier 574R multiplies the reaction force command value Trf(R) for return-to-return by the return-to-return distribution value. The distribution value adder 575 adds the output of the distribution ratio multiplier 574F on the turning side and the output of the distribution ratio multiplier 574R on the return side to calculate the primary response torque command Tresp_p.

In this manner, the response torque command calculation unit 570 of the modified example changes the distribution ratio between the cutting reaction force command value Trf(F) and the steering-back reaction force command value Trf(R) according to the state quantity σ. do. When the state quantity σ is "σ=1 or σ=-1", the configuration in FIG. 12 is substantially the same as the configuration in FIG. However, in the case of "-1<σ<1", the primary response torque command Tresp_p changes continuously or stepwise according to the distribution ratio of the intermediate state or the steering held state. Therefore, it is possible to avoid a discontinuous change in the characteristic of response torque command calculation when the steering state is switched.

(Second embodiment)
Next, a steering control device 202 of a second embodiment will be described with reference to FIGS. 13 to 16. FIG. As shown in FIG. 13, the steering control device 202 of the second embodiment includes a first reference angle calculator 561 that calculates a first reference angle θref1 according to changes in the steering wheel angle equivalent value θr, and a steering wheel angle It has a second reference angle calculator 562 that calculates a second reference angle θref2 different from the first reference angle θref1 in accordance with a change in the equivalent value θr. The first reference angle calculator 561 is substantially the same as the reference angle calculator 561 of the first embodiment.

Reference angle calculation by the first and second reference angle calculators 561 and 562 will be described with reference to the flowchart of FIG. 14 and the time chart of FIG. The initial values of the first reference angle θref1 and the second reference angle θref2 are both 0 or the steering wheel angle equivalent value θr at startup. Here, regarding the calculation of the first reference angle, the terms and symbols such as the reference angle θref and the displacement amount threshold Δθth in the first embodiment are simply replaced with “first reference angle θref1”, “first displacement amount threshold Δθth1”, and the like. is.

In the flowchart of FIG. 6, the expressions in parentheses in each step correspond to the first reference angle calculation expressions. When the absolute value |Δθ1| of the first displacement amount is greater than a predetermined first displacement threshold value Δθth1, the first reference angle calculator 561 determines that the absolute value |Δθ1| of the first displacement amount is equal to or less than the first displacement threshold value Δθth1 The first reference angle θref1 is updated according to the steering wheel angle equivalent value θr so that

The flowchart of FIG. 14 shows the process of calculating the second reference angle. S21 to S25 are the same as S11 to S15 of the first reference angle calculation. However, the second displacement threshold Δθth2 is set larger than the first displacement threshold Δθth1. When the absolute value of the second displacement amount |Δθ2| is greater than the second displacement threshold value Δθth2, the second reference angle calculator 562 sets the absolute value of the second displacement amount |Δθ2| to the second displacement threshold value Δθth2 or less. , the second reference angle θref2 is updated according to the steering wheel angle equivalent value θr. After the second reference angle θref2 is updated in S23 or S24, it is determined in S26 whether or not steering back is being performed. If YES in S26, the second reference angle θref2 is updated to the same value as the first reference angle θref1 in S27.

Next, refer to the time chart of FIG. The upper part of FIG. 15 shows the first reference angle calculation similar to FIG. 7, and the lower part of FIG. 15 shows the second reference angle calculation. A thick solid line common to the upper and lower figures indicates the steering wheel angle equivalent value θr. The thick long dashed line in the upper diagram indicates the first reference angle θref1, and the thick dashed line indicates the reference map value _θMAP1 for the first displacement amount threshold Δθth1. A thick short dashed line in the lower diagram indicates the second reference angle θref2. A thin two-dot chain line in the upper diagram and a thick two-dot chain line in the lower diagram indicate map values θ _MAP2 for reference of the second displacement amount threshold Δθth2. A two-dot chain line reflects S16 and S17 in FIG.

Of the time symbols, t0, tb, tc, te, tf, and th, which are common to the upper and lower figures, conform to FIG. The times ta1, td1, and tg1 at which the map value θ _MAP1 for the first reference angle calculation reaches the upper limit or the lower limit are substantially the same as the times ta, td, and tg in FIG. Therefore, the first reference angle θref1 is calculated in the same manner as the reference angle θref of the first embodiment.

In the second reference angle calculation, the second displacement amount threshold Δθth2, which is the upper limit of the absolute value of the second displacement amount Δθ2, is set larger than the first displacement amount threshold Δθth1, which is the upper limit of the absolute value of the first displacement amount Δθ1. there is Therefore, the times ta2, td2, and tg2 at which the map value θ _MAP2 for the second reference angle calculation reaches the upper limit or the lower limit are slightly later than the times ta1, td1, and tg1 for the first reference angle calculation, respectively.

Further, when the cutting state is shifted to the steering back state at times tb and te, the second reference angle calculator 562 changes the second displacement amount threshold value _Δθth2 based on the map value θMAP2 to a smaller value to update the second reference angle θref2. do. As a result, the second reference angle calculator 562 sets different values of the second displacement amount Δθ2 corresponding to the same steering wheel angle equivalent value θr between the turning state and the turning back state. The time at which the second reference angle θref2 begins to fall is coincident with the lower limit arrival time _td2 of the map value θMAP2. On the other hand, the time tg*2 at which the second reference angle θref2 begins to rise is different from the upper limit reaching time _tg2 of the map value θMAP2.

Returning to FIG. 13, the response torque command calculator 570 of the second embodiment includes two reaction force calculators 571 and 572 corresponding to the two reference angles θref1 and θref2. The first reaction force calculation unit 571 is substantially the same as the reaction force calculation unit 571 of the first embodiment shown in FIG. "1" is added to the symbol of the force command value.

The first reaction force calculator 571 includes a first cutting reaction force calculator 5731 F, a first steering reaction force calculator 5731 R, and a first switch 5761 . The first cutting reaction force calculator 5731F calculates the cutting reaction force command value Trf1(F) using the first cutting reaction force command value map shown in FIG. 8(a). The steering-back first reaction force calculator 5731R calculates the steering-back reaction force command value Trf1(R) using the steering-back first reaction force command value map shown in FIG. 8(b). The first switch 5761 switches between the first reaction force command value for cutting Trf1 (F) and the first reaction force command value for turning back Trf1 (R) based on the signal from the cutting-return determination unit 410 . Note that, instead of the first switch 5761, a configuration for calculating the distribution ratio based on the state quantity σ may be adopted according to the modification of the first embodiment.

Similarly, the second reaction force calculator 572 includes a second reaction force calculator for cutting 5732F, a second reaction force calculator for switchback 5732R, and a second switch 5762 . The second cutting reaction force calculator 5732F stores in advance a map that defines the relationship between the second displacement amount Δθ2 and the second cutting reaction force command value Trf2(F). The steering-back second reaction force calculator 5732R stores in advance a map that defines the relationship between the steering-back second reaction force command value Trf2(R) and the second displacement amount Δθ2.

Each of the second reaction force calculators 5732F and 5732R uses a map to calculate a second reaction force command value Trf2(F) for cutting and a second reaction force command value Trf2(R) for steering back. The second switch 5762 switches between the second reaction force command value Trf2(F) for cutting and the second reaction force command value Trf2(R) for turning back based on the signal from the cutting switchback determination unit 410 . Note that, instead of the second switch 5762, a configuration for calculating the distribution ratio based on the state quantity σ may be adopted according to the modification of the first embodiment.

In the second cutting reaction force command value map shown in FIG. 16A, the rate of change of the second cutting reaction force command value Trf2(F) with respect to the second displacement amount Δθ2 is the absolute value of the second displacement amount |Δθ2 | is set substantially constant in a region equal to or larger than the absolute value |Δθ1| of the first displacement amount. The second cutting reaction force command value Trf2(F) is set to substantially zero in a region where the absolute value of the second displacement amount |Δθ2| is less than the absolute value of the first displacement amount |Δθ1|. Therefore, during cutting, reaction torque corresponding to the second displacement amount Δθ2 is further added.

In the steering-return second reaction force command value map shown in FIG. 16(b), the steering-return reaction force command value Trf2(R) is set to substantially 0 in the entire region of the second displacement amount Δθ2. Therefore, the reaction torque according to the second displacement amount Δθ2 is not added at the time of steering back.

(Third embodiment)
Next, a steering control device 203 of a third embodiment will be described with reference to FIGS. 17 and 18. FIG. As shown in FIG. 17, the steering control device 203 of the third embodiment uses two reference angles θref1 and θref2 in the same manner as in the second embodiment, and includes a viscosity addition calculation unit 597, a current limit calculation unit 610 and a limit angle θref2. It further has a part 613 . Conceptually, the viscosity addition calculation unit 597 is provided inside the response torque command calculation unit 570, and the current limit calculation unit 610 and the current limit calculation unit 613 are provided outside the response torque command calculation unit 570. may not be divided into

The viscosity addition calculation unit 597 calculates a viscosity addition torque Tva proportional to the steering wheel angular velocity equivalent value ωr as an “addition amount”. Further, the addition value of the output of the first reaction force command section 571 and the output of the second reaction force command section 571 by the adder 578 is referred to as a basic response torque command Tresp_b in the sense of "the basic value of the response torque command". The basic response torque command Tresp_b is a command calculated based on the turning reaction force command value Trf(F) or the turning-back reaction force command value Trf(R). An adder 598 calculates a response torque command Tresp by adding the viscosity addition torque Tva to the basic response torque command Tresp_b.

A current limit calculation unit 610 calculates a current limit value Ilim that has different characteristics for the displacement amount Δθ between the turning state and the turning back state. Specifically, the current limit calculation unit 610 includes a cutting current limit calculation unit 611F, a switch-back current limit calculation unit 611R, and a switch 612 .

A steering wheel angle equivalent value θr and a second reference angle θref2 having a wider angle range are input to the turning current limit calculation unit 611F and the turning back current limit calculation unit 611R. As shown in FIG. 16B, the second reaction force command value for switchback is approximately 0, so the first reference angle θref1 may be input to the switchback current limit calculator 611R.

The cutting current limit calculation unit 611F and the reversing current limit calculation unit 611R calculate the cutting current limit value Ilim(F) and the reversing current limit value Ilim(R) based on the second displacement amount Δθ2. As shown in FIGS. 18(a) and 18(b), the current limit value map for cutting and the current limit value map for turning back are respectively the reaction force command value map for cutting shown in FIG. It has the same characteristics as the steering-back reaction force command value map shown in b).

The switch 612 switches between the cutting current limit value Ilim(F) and the switching back current limit value Ilim(R) based on the signal from the cutting switchback determination unit 410, and outputs the current limit value Ilim. Note that, instead of the switch 612, a configuration for calculating the distribution ratio based on the state quantity σ may be adopted according to the modification of the first embodiment.

A limiting unit 613 limits the response torque command Tresp by the current limit value Ilim. The response torque command Tresp_lim after being limited by the limiting unit 613 is input to the adder 556, and the target value T ^** st of the steering torque command value is calculated. Note that the limiting unit 613 may limit the response torque command Tresp by performing torque limitation instead of current limitation. By limiting the current, the basic response torque command Tresp_b is relatively reduced when the torque due to the viscosity addition calculation is large, thereby preventing the response torque command Tresp from becoming too large.

(Fourth embodiment)
Next, a steering control device 204 according to a fourth embodiment will be described with reference to FIGS. 19 and 20. FIG. As shown in FIG. 19, the steering control device 204 of the fourth embodiment uses one reference angle θref, and the response torque command Tresp after addition of the viscous additional torque Tva is fed back to the reference angle calculator 561. be done. Further, similarly to the third embodiment, the response torque command Tresp is limited by the limiter 613 by the current limit value Ilim calculated by the current limit calculator 610 . The post-limiting response torque command Tresp_lim is input to an adder 556 to calculate the target value T ^** st of the steering torque command value.

The flowchart of FIG. 20 shows the reference angle calculation of the fourth embodiment. S11 to S14 are substantially the same as in FIG. "(θref−Δθth)≦θr≦(θref+Δθth)", and when NO is determined in S11 and S12, the process proceeds to S41.

In S41, it is determined whether the displacement amount Δθ is positive, ie, "θr>θref", and whether the response torque command Tresp is smaller than zero. If YES in S41, the reference angle calculator 561 updates the reference angle θref1 to the steering wheel angle equivalent value θr in S43. If NO in S41, the process proceeds to S42.

In S42, it is determined whether or not the displacement amount Δθ is negative, ie, "θr<θref" and the response torque command Tresp is greater than zero. If YES in S42, the reference angle calculator 561 updates the reference angle θref1 to the steering wheel angle equivalent value θr in S44. If NO in S42, the reference angle θref is maintained at the previous value in S45.

In the fourth embodiment, for example, when the response torque command Tresp crosses zero due to the addition of the viscous additional torque Tva, that position is taken as the reference angle θref. That is, the reference angle calculation unit 561 determines whether to cut or return based on the response torque command Tresp, and can generate a continuous reaction force even when the torque due to the viscosity addition calculation is large.

[Action and effect of the present embodiment]
(1) The steering control device 200 (201 to 204) of the present embodiment calculates a reference angle θref according to the angle change up to that point at each position during steering, and reverses the displacement amount Δθ from the reference angle θref. A force command value Trf is calculated. Also, the characteristics of the reaction force command values Trf(F) and Trf(R) with respect to the displacement amount Δθ are made different between when turning and when turning back. As a result, the reaction force device 70 of the steer-by-wire system 90 can present a vehicle-like reaction force that reflects non-linear behavior such as tire rubbing and hysteresis of turning back.

Here, with reference to FIG. 21, the effects of this embodiment will be described. The horizontal axis of FIG. 21 is the steering angle, and the vertical axis is the reaction torque. FIG. 21(a) corresponds to the first embodiment and the like using one reference angle θref, and FIG. 21(b) corresponds to the second embodiment and the like using two reference angles θref1 and θref2. As indicated by the cut and return arrows, the angle and torque at each position transition with hysteresis. In FIGS. 21(a) and 21(b), [1] shows the characteristics when starting cutting from the neutral position, and [2] shows the characteristics when switching from the cutting state to the return state.

In the present embodiment, the rate of change of the cutting reaction force command value Trf(F) with respect to the displacement amount Δθ is set so that the absolute value decreases as the distance from the reference angle θref increases. The rate of change of the force command value Trf(F) is set such that the absolute value increases with increasing distance from the reference angle θref. Therefore, it is possible to obtain the effect of increasing the rise of the reaction torque at the start of cutting from the reference angle θref when turning, and increasing the fall of the reaction torque at the start of returning to the reference angle θref when turning back.

(2) In the fourth embodiment, the reference angle calculation unit 561 operates when the displacement amount Δθ is positive and the response torque command Tresp is smaller than 0, or when the displacement amount Δθ is negative and the response torque command Tresp is 0. When it is larger, the reference angle θref is updated to the steering wheel angle equivalent value θr. As a result, when the response torque command Tresp crosses zero due to the influence of the viscosity addition calculation, a continuous reaction force can be presented without hunting.

(3) The response torque command calculator 570 of the third and fourth embodiments adds a viscous additional torque Tva proportional to the steering wheel angular velocity equivalent value ωr to the basic response torque command Tresp_b calculated based on the reaction force command value Trf. is added to calculate the response torque command value Tresp. As a result, it is possible to present a vehicle-like reaction force that reflects the viscosity.

(4) The limiting unit 613 of the third and fourth embodiments limits the response torque command Tresp by the current limit value Ilim having different characteristics for the displacement amount Δθ between the turning state and the turning back state. As a result, it is possible to reflect the hysteresis at the time of turning and at the time of steering back, and to present a continuous reaction force even when there is a reaction force other than the hysteresis.

(5) The response torque command calculation unit 570 of the present embodiment stores in advance a reaction force command value map for cutting and a reaction force command value map for steering back in the reaction force calculation units 571 and 572 . This makes it possible to reduce the computational load compared to a configuration in which the reaction force command values Trf(F) and Trf(R) are calculated using formulas.

(6) The steering/return determining unit 410 according to the modification of the first embodiment continuously or stepwise indicates the steering state from the steering state to the steering/return state based on at least the steering wheel angular velocity equivalent value ωr. Calculate σ. The response torque command calculation unit 570 changes the distribution ratio of the reaction force command value Trf(F) for cutting and the reaction force command value Trf(R) for steering back in the response torque command Tresp according to the state quantity σ. As a result, the characteristic changes continuously or stepwise when the steering state is switched, so that a smooth steering feeling can be obtained.

(7) In the control shown in S16 and S17 in FIG. 6 and in FIG. 15, when the cutting state shifts to the returning state, the reference angle calculation unit 561 reduces the displacement amount threshold Δθth from the value in the cutting state. to update the reference angle θref. Then, the reference angle calculator 561 sets different values of the displacement amount Δθ corresponding to the same steering wheel angle equivalent value θr in the turning state and the turning back state. As a result, it is possible to present a vehicle-like reaction force that reflects the hysteresis at the time of turning and at the time of turning back.

(8) In the second and third embodiments, the response torque command Tresp is calculated using two reference angles θref1 and θref2. The absolute value of the first displacement amount |Δθ1| is updated to be equal to or less than a predetermined first displacement threshold value Δθth1, and the absolute value of the second displacement amount |Δθ2| is set larger than the first displacement threshold value Δθth1. is updated to be equal to or less than the second displacement amount threshold value Δθth2. The second reaction force command value map for cutting and the second reaction force command value map for steering return have characteristics as shown in FIGS. This makes it possible to present vehicle-like reaction forces that reflect multiple non-linear behaviors due to factors such as the suspension in addition to the tires.

(Other embodiments)
(a) In the steer-by-wire system 90, the reaction force device 70 or the steering device 80 may not include the reaction force reduction gear 79 or the steering reduction gear 89 shown in FIG. Also, the steer-by-wire system 90 may not include the torque sensor 94 .

(b) The steering control device 200 is not limited to the electromechanical integrated structure shown in FIG. good. In that case, the two control units 270 and 280 may not be physically separated, and may be configured as an integral steering control device 200 . Alternatively, one of the reaction force device 70 and the steering device 80 may be configured as an electromechanical integrated system including a comprehensive control section, and may be configured to transmit and receive signals to and from the other device.

(c) The cut/return reaction force command value and the like may be calculated by a formula instead of a map. Each of the illustrated maps may be interpreted as a graph of calculated values using mathematical formulas. In addition, specific characteristics such as reaction force command values based on maps and formulas are not limited to those shown in the drawings. Any characteristic map or mathematical expression may be used as long as the same effects as those of the above embodiment can be obtained as a result.

(d) The driving configuration of the reaction force device 70 is limited to the configuration in which the steering wheel torque control unit 620 performs servo control using the sum of the steering torque command value T ^* st and the response torque command Tresp as the target value T ^** st. do not have. For example, the sum of the steering torque command value T ^* st and the response torque command Tresp may be directly used as the current control command value, or may be converted by the torque constant and used as the current control command value.

(e) In the first embodiment, the average current Iave was used as the physical quantity reflecting the estimated road load, but the inertia component proportional to the acceleration may be used for correction. The average current Iave is updated when the absolute value of the reference angle |θref| is greater than the predetermined value A. However, in addition to the absolute value of the reference angle |θref| The average current Iave may be updated.

The present invention is not limited to such embodiments, and can be embodied in various forms without departing from the scope of the invention.

The control apparatus and techniques described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by the computer program. may be Alternatively, the controller and techniques described in this disclosure may be implemented by a dedicated computer provided by configuring the processor with one or more dedicated hardware logic circuits. Alternatively, the control apparatus and techniques described in this disclosure can be implemented by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may also be implemented by one or more dedicated computers configured. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium.

200 (201 to 204) ... steering control device,
410... Cut switchback determination section, 510... Reaction force control section,
561... (first) reference angle calculator, 562... second reference angle calculator,
570 ... Response torque command calculation unit,
70... Reaction force device, 77... Reaction power converter, 78... Reaction rotating electric machine,
80... Steering device, 87... Power converter for steering, 88... Rotating electric machine for steering,
90 Steer-by-wire system,
91... steering wheel, 99... wheel.

Claims (10)

a reaction device (70) including a reaction rotating electric machine (78) and a reaction power converter (77) for driving the reaction rotating electric machine (78) and connected to a steering wheel (91);
a steering device (80) for steering a wheel (99), including a steering rotating electrical machine (88) and a steering power converter (87) for driving the steering rotating electrical machine;
In a steer-by-wire system (90) comprising There is
a reaction force control unit (510) for calculating a steering torque command value (T ^* st) based on physical quantities (Tt, T ^* t, It, I ^* t) corresponding to the output torque of the steering device;
a reference angle calculator (561) for calculating a reference angle (θref) according to changes in steering wheel angle equivalent values (θr, θt) corresponding to the angle of the steering wheel;
A cut-back determination unit (410) for discriminating between a cut-back state in which the steering wheel is cut in a direction away from the reference angle and a cut-back state in which the steering wheel is turned back toward the reference angle. When,
According to the amount of displacement (Δθ) of the steering wheel angle equivalent value from the reference angle, a turning reaction force command value (Trf(F)) corresponding to the turning state and a turning force command value (Trf(F)) corresponding to the turning back state A response torque command for calculating a return reaction force command value (Trf(R)) and calculating a response torque command (Tresp) based on at least the cutting reaction force command value or the steering back reaction force command value. a calculation unit (570);
has
The reference angle calculation unit performs the above updating the reference angle according to the steering wheel angle equivalent value;
The response torque command calculation unit calculates the reaction force command value for cutting and the reaction force command value for steering back using a map or a formula, and in the map or formula,
The rate of change of the reaction force command value for cutting with respect to the displacement amount is set so that the absolute value decreases as the distance from the reference angle increases,
A steering control device, wherein a rate of change of the reaction force command value for steering return with respect to the displacement amount is set such that an absolute value thereof increases with increasing distance from the reference angle. The reference angle calculation unit
when the displacement amount is positive and the response torque command is smaller than 0, or
When the displacement amount is negative and the response torque command is greater than 0,
2. A steering control device according to claim 1, wherein said reference angle is updated to said steering wheel angle equivalent value. The response torque command calculation unit
A steering wheel angular velocity equivalent value (ωr, 3. The steering control device according to claim 1, wherein the response torque command is calculated by adding an additional amount (Tva) proportional to .omega.t). The steering according to any one of claims 1 to 3, further comprising a limiter (613) for limiting the response torque command by a limit value having different characteristics with respect to the displacement amount between the turning state and the steering back state. Control device. The response torque command calculation unit
A cutting reaction force command value map that defines the relationship of the cutting reaction force command value with respect to the displacement amount, and a steering-back reaction force command value that defines the relationship of the steering-back reaction force command value with respect to the displacement amount The steering control device according to any one of claims 1 to 4, wherein the map is stored in advance. The steering wheel turning back determination unit continuously or stepwise changes the steering state from the steering wheel turning state to the steering wheel back state based on at least a steering wheel angular velocity equivalent value (ωr, ωt) corresponding to the angular velocity of the steering wheel. Calculate the state quantity shown,
6. The response torque command calculator according to any one of claims 1 to 5, wherein the response torque command calculation unit changes a distribution ratio between the cutting reaction force command value and the steering back reaction force command value in accordance with the state quantity. steering control device. When shifting from the cut state to the return state,
The reference angle calculation unit updates the reference angle by reducing the displacement threshold value from the value in the cutting state,
The steering control device according to any one of claims 1 to 6, wherein the displacement amount corresponding to the same steering wheel angle equivalent value is different between the turning state and the turning back state. Assuming that the reference angle is a first reference angle (θref1) and the reference angle calculation section is a first reference angle calculation section, a second reference angle different from the first reference angle is obtained in accordance with a change in the steering wheel angle equivalent value. further comprising a second reference angle calculator (562) for calculating the angle (θref2),
The response torque command calculation unit
A first reaction force command value for cutting and a first reaction force command value for turning back calculated based on a first displacement amount (Δθ1) that is a displacement amount of the steering wheel angle equivalent value from the first reference angle, and , the second reaction force command value for turning and the second reaction force command value for steering back calculated based on the second displacement amount (Δθ2) that is the displacement amount of the steering wheel angle equivalent value from the second reference angle Calculate the response torque command based on
The absolute value of the first displacement amount is updated to be equal to or less than a predetermined first displacement threshold value (Δθth1), and the absolute value of the second displacement amount is set larger than the first displacement threshold value. updated to be equal to or less than the second displacement threshold (Δθth2),
In the map or formula used to calculate the second reaction force command value for cutting and the second reaction force command value for steering back,
The rate of change of the second reaction force command value for cutting with respect to the second displacement is set constant in a region where the absolute value of the second displacement is equal to or greater than the absolute value of the first displacement,
The steering control device according to any one of claims 1 to 7, wherein the steering-back second reaction force command value is set to 0 in the entire region of the second displacement amount. The response torque command calculation unit
The steering control according to any one of claims 1 to 8, wherein the response torque command calculated based on the reaction force command value for steering or the reaction force command value for steering return is changed according to a road load. Device. The response torque command calculation unit
The steering control device according to any one of claims 1 to 9, wherein the response torque command calculated based on the reaction force command value for steering or the reaction force command value for steering return is changed according to vehicle speed. .

Images