JP3248568B2 - Steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device for turning a steered wheel according to a steering angle.
In particular, the present invention relates to a steering device having a variable gear ratio mechanism and a power assist mechanism.

[0002]

2. Description of the Related Art Conventionally, a steering device having a variable gear ratio mechanism has been known. Variable gear ratio mechanism, parameters representing the operating state (e.g., the vehicle speed v) depending on the aims to change the input angle (steering angle) theta output angle for _h (pinion shaft angle) theta _p ratio . The variable gear ratio mechanism, the output angle target value theta _p ^~ and the output angle theta _p deviation between ^{_{e (= θ p ~ -θ p}} ) is controlled to be zero. In the present specification, the notation “X” is defined to be the same as the notation in which “ ^〜 ” is added above “X”. X is any symbol.

[0003] On the other hand, a power assist mechanism aims to apply a steering assist force in accordance with a steering torque generated by steering a steering wheel.

As described above, since the purpose of the variable gear ratio mechanism and the purpose of the power assist mechanism are different, in a conventional steering apparatus, these mechanisms are independently controlled.

Japanese Patent Laying-Open No. 4-310474 discloses a steering device having a variable gear ratio mechanism and a power assist mechanism. In the steering device described in this publication, switching between a variable gear ratio mechanism and a power assist mechanism is controlled. Therefore, in the steering apparatus described in this publication, only control according to the characteristics of one of the variable gear ratio mechanism and the power assist mechanism can be realized.

[0006]

A conventional steering device having a variable gear ratio mechanism has the following features (1) to (1).
There was the problem (4). Hereinafter, each problem will be described in detail.

(1) Since the reaction force fluctuates according to the vehicle speed,
The driver may feel uncomfortable with operating the vehicle.

[0008] The reaction force is generated between the road surface and the tire. A. Those based on T (self-aligning torque) are dominant. During normal steering (K _v = 1, θ _h
= Reaction force T _SAT occur theta _p) is approximately expressed by the equation (1).

[0009]

(Equation 1) T_SAT= C_SAT・ Θ_h  = C_SAT・ Θ_p Where θ_hIndicates the input angle (steering steering angle),
θ_pIndicates the output angle (pinion axis angle), and C_SATIs prescribed
Indicates a number.

In the variable gear ratio mechanism, control is performed so that the relationship of (Expression 2) is satisfied.

[0011]

(2) where _{θ p = K v · θ h} , K v represents the coefficient representing the variable gear ratio.

From (Equation 1) and (Equation 2), the reaction force T _SAT is
It is obtained by (Equation 3).

[0013]

According to T _SAT = C _SAT · θ _p = C _SAT · K _v · θ _h (Equation 3), the reaction force T _SAT is determined by the coefficient K _v even if the steering angle θ _h is the same. It can be seen that it fluctuates. Since K _v is a function of the vehicle speed v, the reaction force T
_{The SAT} can vary with the vehicle speed v regardless of the driver's steering. This causes the driver to feel uncomfortable with the operation of the vehicle.

(2) The follow-up characteristic of the variable gear ratio actuator may be deteriorated due to the current limitation (torque limitation).

The variable gear ratio control is performed by controlling a current applied to a motor of a variable gear ratio actuator. Such current control is achieved by high-speed voltage switching according to the PWM duty ratio.

(Equation 4) shows the circuit formula of the motor.

[0017]

Equation 4] _{^{V-k θ θ · = LI}} · + RI where, I: motor current, V: motor voltage, k _theta: the counter electromotive force constant, L: inductance, R: resistance, theta ^·: a motor rotation angular speed is there. The symbol “·” indicates differentiation with time. As used herein, the notation ^"X-" is defined as synonymous with the notation given the - on top of the "X". X is any symbol.

[0018] From equation (4), the maximum current I _max at steady state ^(I · = 0) is expressed by equation (5).

[0019]

Equation 5] _{I max = (V max -k θ} θ ·) / R Thus, the current I flowing through the motor is limited by the maximum current I _max. Further, a rated current is determined for the motor drive circuit and the motor in terms of protection of the device.
This also limits the current I flowing through the motor.

With such a current limitation, the position control (e
It may be difficult to generate the torque required for (→ 0) only by the variable gear ratio actuator. If the torque required for the position control is insufficient, the following characteristics of the variable gear ratio actuator deteriorate.

(3) The initial response of the variable gear ratio actuator is poor.

The torque command value T _opt required for position control is
It is obtained according to (Equation 6).

[0023]

T _opt = C _T (s) e where C _T (s) denotes a feedback compensator and e
It indicates the deviation of the output angle target value theta _P ^~ and the output angle theta _P.

From equation (6), the torque command value T _opt increases in proportion to the magnitude of the deviation e. This means that sufficient torque is not generated in the early stage of steering with a small deviation e. Accordingly, the response of the variable gear ratio actuator tends to be delayed in the early stage of steering.

(4) Since the speed at which the rack collides with the stopper is high, the driver may feel uncomfortable with the operation of the vehicle and may be disadvantageous in terms of vehicle durability.

When the variable gear ratio actuator sufficiently follows (e ≒ 0), the relationship shown in (Expression 7) is established.

[0027]

K _v θ _h −θ _p = 0 By differentiating both sides of (Equation 7), the relation shown in (Equation 8) is established.

[0028]

From the number 8 ^{_{K v θ h · = θ p}} · ( number 8), collision speed θ _p ^· when the rack collides with the stopper, to be a K _v times the speed θ _h ^· of steering angle Understand. For this reason, the driver may feel uncomfortable with the operation of the vehicle, or may be disadvantageous in terms of vehicle durability.

[0029]

[0030] The purpose is of the present invention, the current limit (torque limit)
Accordingly, it is an object of the present invention to provide a steering device in which the following characteristics of the variable gear ratio actuator do not deteriorate.

Another object of the present invention is to provide a steering device having a high response even at the time of initial steering with a small deviation e.

[0032]

[0033]

[0034]

Scan tearing device of the present invention SUMMARY OF THE INVENTION comprises a steering wheel steering angle to the steering angle and the variable gear ratio actuator for varying, and a power assist actuator which applies a steering assist force to a steering device a steering apparatus, the movable required to the steering wheel turning angle control based on the scan tearing steering angle
The torque by the variable gear ratio actuator is
When it is insufficient due to the limitation of the current flowing through the actuator,
A current corresponding to the insufficient torque is supplied to the power assist actuator.
Send the insufficient torque to the power assist
Compensation by the torque generated by the actuator . Thereby, the above object is achieved.

Another steering apparatus according to the present invention is a steering apparatus having a variable gear ratio actuator for varying a steering wheel turning angle with respect to a steering angle, and a power assist actuator for applying a steering assist force to the steering apparatus. The variable gear ratio actuator is feedforward controlled based on the output of the torque sensor and the target current of the power assist actuator. Thereby, the above object is achieved.

[0036]

[0037]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a configuration of a steering apparatus 100 according to Embodiment 1 of the present invention.

The steering device 100 includes a steering wheel 1, an input angle sensor 2, a torque sensor 3,
Variable gear ratio actuator 4, output angle sensor 5, power assist actuator 12, steering wheel turning mechanism 1
0 (rack and pinion type), a vehicle speed sensor 13,
And an EMPS / VGRS controller 17.

Here, EMPS is an abbreviation for an electric motor power steering system, and VGRS is an abbreviation for a variable gear ratio steering system. Controller 17
Controls both systems in an integrated manner.

The input angle sensor 2, the input angle (steering angle) in accordance with the rotation of the steering wheel 1 to detect a theta _h. The output of the input angle sensor 2 is EMPS / VGR
It is supplied to the S controller 17.

The torque sensor 3 detects a steering torque ^TP applied to the steering shaft 1a by the rotation of the steering wheel 1. The output of the torque sensor 3 is EMPS
/ VGRS controller 17.

The variable gear ratio actuator 4 includes a motor 4
a. The rotation of the motor 4a is EMPS / VG
VGRS current I _F output from RS controller 17
Is controlled in accordance with The rotation shaft of the motor 4a is connected to the pinion shaft 7.

The output angle sensor 5 detects an output angle (pinion axis angle) θ _p according to the rotation of the motor 4a. The output of the output angle sensor 5 is output to the EMPS / VGRS controller 17.
Supplied to

The power assist actuator 12 includes a motor 12a and a gear 6. A gear 12b is provided at the tip of the motor 12a. The gear 12b and the gear 6 are arranged so as to mesh with each other. Gear 6
Are arranged coaxially with the pinion shaft 7. Motor 12
Rotation of a is controlled in accordance with EMPS current I _a which is output from the EMPS / VGRS controller 17.

The steering wheel turning mechanism 10 converts the rotation of the pinion shaft 7 into an axial movement of the rack 8 to which the steering wheels FW1, FW2 are connected. Steered wheels FW1, FW2 are connected to rack 8 via tie rods 9a, 9b. In accordance with the rotation of the pinion shaft 7, the rack 8 of the steering wheel turning mechanism 10
Are shifted to the left and right, so that the steered wheels FW1, FW2
Is steered. Due to hardware factors, rack 8
Are predetermined. Stoppers 16a and 16b are provided at the end of the shiftable range.

The vehicle speed sensor 13 detects a vehicle speed v. The output of the vehicle speed sensor 13 is supplied to the EMPS / VGRS controller 17.

The EMPS / VGRS controller 17 is
The variable gear ratio actuator 4 and the power assist actuator 12 are integrally controlled. Specifically, EMP
The S / VGRS controller 17 determines the vehicle speed v and the input angle θ _h
On the basis of the output angle θ _p and the steering torque T ^∧ and, VGRS
It generates a current I _F and EMPS current I _a.

The output angle θ _p described above is determined for the steered wheels FW 1, F
It is different from the steering angle of W2. However, in the following description, it is assumed that the output angle θ _p and the steered angles of the steered wheels FW1 and FW2 are identified. And controlling the output angle theta _p on the basis of the input angle theta _h, the steering wheel FW on the basis of the input angle theta _h
This is because controlling the steering angle of the FW2 is substantially equivalent. For example, the steering wheel F with respect to the output angle θ _p
When the ratio of the steered angles of W1 and FW2 is constant, controlling the output angle θ _p is equivalent to controlling the steered angles of the steered wheels FW1 and FW2.

[0050] Further, instead of the output angle sensor 5, by using a sensor for detecting the steering angle of the steered wheels FW1, FW2 as the output angle sensor, steering of the steered wheels FW1, FW2 based on the input angle theta _h The angle can be controlled directly. It is also within the scope of the present invention directly controls the steering angle of the steering wheels FW1, FW2 based on the input angle theta _h.

FIG. 2 shows the configuration of the EMPS / VGRS controller 17.

The EMPS / VGRS controller 17 is
Coefficient map unit 18, compensator 19, torque distribution logic unit 27, torque-current conversion units 20, 28, VGR
S motor drive circuit 21 and EMPS motor drive circuit 26
And an EMPS target current calculator 23.

FIGS. 3A to 3C show the procedure of processing executed by the EMPS / VGRS controller 17 having the above-described configuration.

FIG. 3A shows a procedure (steps S110 to S150) of the VGRS system processing among the processing executed by the EMPS / VGRS controller 17. Hereinafter, the processing procedure will be described step by step.

Step S110: The EMPS / VGRS controller 17 determines the input angle θ _h output from the input angle sensor 2 and the output angle θ _p output from the output angle sensor 5,
The vehicle speed v output from the vehicle speed sensor 13 is read.

Step S120: The coefficient map unit 18
To determine the coefficient K _v. For example, the coefficient _Kv is the vehicle speed sensor 1
3 is determined on the basis of the vehicle speed v output from the control unit 3.

[0057] step S130: the output angle target value θ _p ^~ is set. Output angle target value θ _p ^~, the coefficient map 18
Obtained by multiplying the input angle theta _h output from the input angle sensor 2 to the coefficient K _v output from. That is, θ _p ^〜 is obtained according to (Equation 9).

[0058]

Equation 9] where ^{_{θ p ~ = K v θ h}} , K v denotes an output angle target value theta _p ^~ the ratio of the input angle theta _h. As described above, K _v is variable.

[0059] step S140: the deviation e of the output angle target value θ _p ^~ and the output angle θ _p is determined in accordance with (number 10).

[0060]

Equation 10] e = θ _p ^~ - θ _p Step S150: compensator 19, the torque command value to the deviation e to 0 without overshooting T _opt
To determine. Such control is achieved, for example, by appropriately setting the parameters of the PID control according to (Equation 11).

[0061]

T _opt = C _T (s) e where s is a Laplace operator.

Step S150 corresponds to step S150 in FIG. 3C.
Continue to 310.

FIG. 3B shows the procedure (S210 to S220) of the processing of the EMPS system among the processing executed by the EMPS / VGRS controller 17. Hereinafter, the processing procedure will be described step by step.

Step S210: EMPS / VGRS
The controller 17 controls the steering torque T ^# output from the torque sensor 3 and the vehicle speed v output from the vehicle speed sensor 13.
And the output angle θ _p output from the output angle sensor 5 are read.

Step S220: EMPS target current calculation
The unit 23 includes the EMPS target current I_a ^~Is calculated. EMP
S target current I_a ^~Is not related to the essence of the present invention.
I am in charge. The EMPS target current calculation unit 23 can perform any method
EMPS target current I according to _a ^~Can be calculated. Sand
C, I_a ^~Is obtained according to (Equation 12).

[0066]

I _a ^~ = Kia (v, T ^，, θ _p ) where Kia is an arbitrary function.

For example, the EMPS target current calculator 23 calculates
To calculate: EMPS target current I _a ^~ based on the "basic assist section" and "return and damper control section". The “basic assist term” is obtained, for example, according to the steering torque T ^# . "Return and damper control section", for example, determined by calculating in accordance with the vehicle speed v and the output angle theta _p, (proportional to the theta _p ^·) viscous component and returning the component (proportional to the theta _p) Can be

Step S220 corresponds to step S220 in FIG. 3C.
Continue to 370.

FIG. 3C is a processing procedure for integrating the EMPS system and the VGRS system (steps S310 to S3).
80). Hereinafter, the processing procedure will be described step by step.

Step S310: The torque distribution logic unit 27 calculates an ideal reaction force _Fopt . Ideal reaction force F _opt
Is obtained by multiplying the torque command value T _opt by the transfer function W (s). That is, F _opt is ( _Equation 13)
It is asked according to.

[0071]

F _opt = W (s) T _opt Here, the transfer function W (s) is a filter for removing high-frequency noise.

FIG. 4 shows the relationship between the frequency of the transfer function W (s) and the gain. In FIG. 4, f indicates a predetermined frequency. By using such a transfer function W (s), the ideal reaction force F _opt can be made smooth.
Accordingly, even if the coefficient K _v abruptly changes the reaction force is prevented from being rapidly changed. As a result, the feeling of strangeness in the steering feeling is eliminated.

[0073] Step S320: the torque distribution logic unit 27 determines the ^~ VGRS torque command value ^F. That is, F ¹ is determined according to (Equation 14).

[0074]

Equation 14] _{^{F ~ = T opt (| F}} opt | ≧ | T opt | if) ^F ~ = F _opt According to _{(| F opt | <| |} T opt cases) (number 14), the deviation e = 0, F ^~ = 0
Becomes When the deviation e = 0, T _opt = C _T (s) e =
0, and | F _opt | ≧ | T _opt | = 0 holds. Therefore, during steering, the variable gear ratio actuator 4 is controlled so as not to generate torque.

Step 330: The torque distribution logic unit calculates the EMPS distribution torque DT. EMPS distribution torque DT is obtained by subtracting the VGRS torque command value ^{F ~} from the torque command value T _opt. That is, DT is obtained according to (Equation 15).

[0076]

DT = T_opt-F^~= T_opt-W (s) T_opt  = (1-W (s)) T_opt As described above, the torque distribution logic unit 27 includes the compensator 19
Command value T determined by_optThe variable gear ratio
The actuator 4 and the power assist actuator 12
Distribute to That is, the torque distribution logic unit 27
Torque command value T_optOf the VGRS torque command value F^~
Is supplied to the torque-current converter 20 as a torque command value.
T_optOf the remainder as the EMPS distribution torque DT
The current is supplied to the current converter 28.

Step S340: torque-current converter 2
0 indicates that the VGRS torque command value F is changed ^{to the} VGRS target current I
_F to convert ^~ to.

[0078] Step S350: VGRS motor drive circuit 21, current flowing in the motor 4a drives the motor 4a so as to approach the ^~ VGRS target current I _F.

Step S360: torque-current converter 2
8, the EMPS distribution torque DT is added to the additional target current DI _a
Convert to

[0080] Step S370: EMPS target EMPS target current I _a ^~ a torque output from the current calculator 23 - additional target current DI output from the current conversion unit 28
_a is added. As a result, it EMPS target current (updated value) I _a ^~~ is obtained. That is, I _a ^~
6).

[0081]

Equation 16] _{^{I a ~~ = I a ~ +}} DI a step S380: EMPS motor drive circuit 26, current flowing in the motor 12a is EMPS target current (updated value)
So as to approach the I _a ^~~ driving the motor 12a.

In step S310, the ideal reaction force F _opt may be calculated according to ( _Equation 17).

[0083]

[Equation 17] F_opt= M₁θ_h+ M_Twoθ_h ^・+ M_Threeθ_h ^{・ ・}+ M_Four Where M₁~ M_FourIndicates a predetermined coefficient. M₁~ M_FourIs
F_optThe reaction force that best matches the human steering feeling
Determined by experiment as indicated. According to (Equation 17)
If the reaction force F_optIs the coefficient K_vIrrelevant and required. This
As a result, the coefficient K _vEven if changes suddenly,
A sudden change in force is prevented. As a result, steering
The feeling of discomfort is eliminated.

FIG. 5 shows the configuration of the compensator 19. The compensator 19 includes a proportional gain 19a, a differentiator 19b, a differential gain 19c, an integrator 19d, and an integral gain 19e. The compensator 19 determines the torque command value T _{opt according} to ( _Equation 18).

[0085]

Equation 18] where _{T opt = G P e + G} D e · + G I ∫edt, G P is a proportional gain, G _D is the differential gain, G _I shows the integral gain.

[0086] This ensures that, variable gear ratio actuator 4
And the control of the power assist actuator 12 can coexist in an integrated manner.

Embodiment 2 Hereinafter, a steering device 200 according to Embodiment 2 of the present invention will be described. The steering device 200 includes the steering device 10 shown in FIG.
0 has the same configuration.

FIG. 6 shows the configuration of the EMPS / VGRS controller 17. 6, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

Among the processing executed by the EMPS / VGRS controller 17, the processing procedure of the EMPS system and the processing procedure of the VGRS system are shown in FIGS. 3A and 3B.
Is the same as the processing procedure shown in FIG. Therefore, the description is omitted here.

FIG. 7 is a flowchart showing a procedure for integrating the EMPS system and the VGRS system (steps S710 to S78).
0). Hereinafter, the processing procedure will be described step by step.

Step S710: This step corresponds to FIG.
It is executed after step S150 of A is executed. The torque-current converter 20 converts the torque command value T _opt into VGR
Converting S target current I _F ^~ a.

Step S720: Current saturation processing section 29
Performs current saturation processing on the VGRS target current I _F ^~. Thus, VGRS target current I _F ^~ is limited so as not to exceed a predetermined upper limit value I _0, VGRS target current I _F ^~ is limited so as not to fall below a predetermined lower limit value (-I _0). I ₀ is, for example, the rated current of the device. Results of the current saturation, VGRS target current I _F ^~ is, VGRS
Target current (updated value) are converted to I _F ^~~. That is,
I _F ^~~ is determined according to equation (19).

[0093]

[Number 19] ^{_{I F ~~ = I 0 (I}} 0 < In the case of I _F ^~) (case of ^{_{-I 0 ≦ I F ~ ≦ I}} 0) I F ~~ = I F ~ I F ~~ = -I ₀ (the case of I _F ^~ <-I ₀₎ step S730: VGRS motor drive circuit 21, current flowing in the motor 4a is VGRS target current (updated value) I
So as to approach the _F ^~~ drives the motor 4a.

[0094] Step S740: the current detector 30, current actually flowing through the motor 4a (actual current) is detected I _F ^∧.

Step S750: VGRS target current I _F
By actual current I _F ^∧ is subtracted ^from, the current shortage [Delta] I _F is calculated. That is, ΔI _F is given by (Equation 20)
Is required in accordance with

[0096]

Equation 20] ^{_{ΔI F = I F ~ -I F}} ∧ Step S760: VGRS current -EMPS current converter 31, EM current shortage [Delta] I _F as VGRS current
It is converted into the PS current ΔI _a.

Step S770: This step corresponds to FIG.
It is executed after step S220 of B is executed. E
A current [Delta] I _a output from EMPS target current I _a ^~ a VGRS current -EMPS current converter 31 which is outputted from the MPS target current calculating unit 23 is added. As a result, E
MPS target current (updated value) I _a ^~~ is obtained. That is, I _a is obtained according to ( ^Equation 21).

[0098]

Equation 21] _{^{I a ~~ = I a ~ +}} ΔI a step S780: EMPS motor drive circuit 26, current flowing in the motor 12a is EMPS target current (updated value)
So as to approach the I _a ^~~ driving the motor 12a.

[0099] In this way, the variable gear ratio actuator 4
Variable gear ratio actuator required to by Ri position location control the current is limited to flow in the motor 4a of (e → 0)
Even if a shortage of torque due to over motor 4, Torr torque shortfall by the power assist actuator 12
Can compensate for the problem. As a result, it is possible to prevent the following characteristic of the variable gear ratio actuator 4 from deteriorating due to current limitation (torque limitation).

(Embodiment 3) Hereinafter, a steering device 300 according to Embodiment 3 of the present invention will be described. The steering device 300 includes the steering device 10 shown in FIG.
0 has the same configuration.

FIG. 8 shows the configuration of the EMPS / VGRS controller 17. 8, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

Among the processing executed by the EMPS / VGRS controller 17, the processing procedure of the EMPS system and the processing procedure of the VGRS system are shown in FIGS. 3A and 3B.
Is the same as the processing procedure shown in FIG. Therefore, the description is omitted here.

FIG. 9 is a flowchart of a process for integrating the EMPS system and the VGRS system (steps S910 to S95).
0). Hereinafter, the processing procedure will be described step by step.

Step S910: This step corresponds to FIG.
It is executed after step S220 of B is executed. Feedforward compensator 32, the steering torque output from the torque sensor 3 T ^∧ and EMPS target current calculating section 23
Based on EMPS target current I _a ^~ and output from,
The position control feedforward torque _Tff is calculated. That is, T _ff is obtained according to ( _Equation 22).

[0105]

Equation 22] _{T ff = H 1 (s)} T ∧ + H 2 (s) αI a ~ Here, H ₁ (s) is determined in accordance with equation (23).
H ₂ (s) is obtained according to (Equation 24). s is a Laplace operator. α is a torque constant.

[0106]

Equation 23] _{H 1 (s) = {K} v (I p s 2 + C p s + K p)}
_{/ {(K v I p +} I h) s 2 + (K v C p + C h) s + K
_p K _v ｝

[0107]

Equation 24] _{H 2 (s) = - (} I h s 2 + C h s) / {(K v
^{_{I p + I h) s 2}} + (K v C p + C h) s + K p K v} Note that the meaning of the symbols in the equation (23) and (Equation 24), see Figure 10 described later.

Step S920: The position control feedback torque T _fb (= T _opt ) output from the compensator 19 and the position control feed forward torque T _ff output from the feed forward compensator 32 are added. As a result, a torque command value F ¹ is obtained. In other words, ^{F ~} is,
It is obtained according to (Equation 25).

[0109]

Equation 25] ^F ~ = T _ff + T _fb Step S930: Torque - current converter 20 converts the ^~ torque command value ^F to VGRS target current I _F ^~.

[0110] Step S940: VGRS motor drive circuit 21, current flowing in the motor 4a drives the motor 4a so as to approach the ^~ VGRS target current I _F.

[0111] Step S950: EMPS motor driving circuit 26, the current flowing through the motor 12a drives the motor 12a so as to approach the ^~ EMPS target current I _a.

FIG. 10 shows the spring-mass of the steering system.
3 shows a damper model. With reference to FIG. 10, the calculation of (Equation 23) and (Equation 24) described above will be described.

The model is separated at the variable gear ratio actuator 4. The equation of motion for the steering shaft 1a is shown in (Equation 26). Pinion shaft 7 to rack 8
The equation of motion for the steered wheels FW1, FW2 is (Equation 2)
It is shown in 7). In the steady state, the variable gear ratio actuator 4 satisfies the condition of (Equation 28).

[0114]

[Number 26] ^{_{T ∧ -T VGRS = I h θ}} h ·· + C h θ h ·

[0115]

T _VGRS + T _EMPS = I _p θ _p ^·· + C _p θ _p ^· + K _p θ _p

[0116]

K _v θ _h −θ _p = 0 The Laplace transform equation of (Equation 26) is shown in (Equation 29).
The Laplace transform equation of (Equation 27) is shown in (Equation 30).
By substituting (Equation 29) and (Equation 30) into (Equation 28), the torque T _VGRS is given by (Equation 31).

[0117]

[Number 29] ^{_{θ h = (T ∧ -T VGRS}} ) / (I h s 2 + C h s)

[0118]

Equation 30] _{θ p = (T VGRS + T} EMPS) / (I p s 2 + C p s + K p)

[0119]

Equation 31] _{T VGRS = H 1 (s)} T ∧ + H 2 (s) T EMPS wherein, H ₁ (s) and H ₂ (s), as shown in (Expression 23) and (Equation 24) It is.

The power assist actuator 12
In the relationship between ^~ torque T _EMPS and the current I _a is shown in equation (32).

[0121]

By substituting T _EMPS = αI _a ^~ (Equation 32) into (Equation 31), (Equation 3)
3) is obtained.

[0122]

In Equation 33] _{T VGRS = H 1 (s)} T ∧ + H 2 (s) αI a ~ present embodiment, (the number 33) into consideration, the variable gear ratio position control feedforward torque T _ff of the actuator 4 Is defined as shown in (Equation 22).

As described above, according to the steering device 300, the motor 4a of the variable gear ratio actuator 4 is driven based on the position control feedforward torque _Tff and the position control feedback torque _Tfb . The position control feedforward torque _Tff is determined depending on the steering torque T ^# output from the torque sensor 3. The torque sensor 3 calculates a second derivative θ of the steering angle.
It has the response of the _h ^{·· (acceleration).} Thus, by utilizing the output of the torque sensor 3 (steering torque T ^∧) to the position control of the motor 4a, quick response than the response of the deviation e can be obtained. As a result, a quick response can be realized even in the early stage of steering with a small deviation e.

FIG. 11A shows the output angle θ by the conventional control.
_p is showing how to follow the output angle target value θ _p ^~. FIG. 11B
Is that the output angle θ _p becomes the output angle target value θ _p by the control of the present invention.
^The following is shown. In FIG. 11A, the deviation e (= θ
As _p ^~ _{-θ p)} of generator while the output angle theta _p rises gently, in FIG. 11B, since the control input in response to the rising of the torque sensor 3 is generated, even in the initial steering stage deviation e is less output It can be seen that the angle θ _p rises quickly.

(Embodiment 4) Hereinafter, a steering device 400 according to Embodiment 4 of the present invention will be described. The steering device 400 includes the steering device 10 shown in FIG.
0 has the same configuration.

FIG. 12 shows the configuration of the EMPS / VGRS controller 17. 12, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and
The description is omitted.

Among the processing executed by the EMPS / VGRS controller 17, the processing procedure of the EMPS system and the processing procedure of the VGRS system are shown in FIGS. 3A and 3B.
Is the same as the processing procedure shown in FIG. Therefore, the description is omitted here.

FIG. 13 is a flowchart showing a procedure for integrating the EMPS system and the VGRS system (steps S1310 to S1310).
1350). Hereinafter, the processing procedure will be described step by step.

Step S1310: This step is executed after step S150 in FIG. 3A has been executed.
The reaction force increase logic unit 33 includes an additional EMPS target current D
Calculate _Ia . DI _a is determined in accordance with equation (34).

[0130]

[Number 34] _{DI a = G (s) (} θ p - · -θ p ·) (| θ p |> θ case of _{pe -ε pe) DI a = 0} (| θ p | ≦ θ pe -ε pe Here, θ _p indicates the output angle. θ _p- ^· is the stopper 16a
The target value of the output angular velocity near (or 16b) is shown. θ _p ^· indicates the output angular velocity. θ _pe indicates the maximum output angle (maximum steering angle) when the rack 8 collides with the stopper 16a (or 16b). θ _pe > 0. ε _pe indicates a predetermined constant. _Let ε _pe > 0. G (s) indicates a feedback compensator.

According to (Equation 34), DI _a = 0 in an area other than the vicinity of the maximum steering angle. This is to prevent the steering wheel 1 from becoming heavy due to lack of assist torque in a region other than the vicinity of the maximum turning angle.

Ε _pe can be determined, for example, as shown in ( _Equation 35).

[0133]

３５ _pe = max (θ _p ^· ) · max (T _pe ) where max (θ _p ^· ) indicates the maximum value of the output angular velocity θ _p ^· , and max (T _pe ) indicates the feedback compensator G. (S) indicates the maximum value of the response time _Tpe required to be controlled as θ _p ^{− ·} −θ _p ^· → 0.

The feedback compensator G (s) is given by (Equation 3)
As shown in 6), it can be configured by appropriately taking the parameters of the PID control.

[0135]

[Expression 36] DI_a= G (s) (θ_p ^-・−θ_p ^・)  = G_P(Θ_p ^-・−θ_p ^・) + G_I∫ (θ_p ^-・−θ_p ^・) Dt + G
_D(Θ_p ^-...−θ_p ^{・ ・}) Where G_PIs the proportional gain, G_DIs the differential gain, G_IIs the product
Indicates the minute gain. Here, the target value θ of the output angular velocity_p ^-・Is
For example, stearin without a variable gear ratio actuator
Θ means that the speed is about the same as that of the_h ^・Becomes equal to
It may be set as follows. Also, the rack 8 is
a constant value that does not give an excessive impact when colliding with
May be.

[0136] in only at the time of the cut of the steering wheel 1 θ _p ^{- ·} = target value of the output angular velocity in such a way that θ _h ^· θ _p ^- may be set ^-. During the return of the steering wheel 1, it is not necessary to particularly control the output angular velocity theta _p ^·. Here, it can be determined by the one time back at either the steering wheel 1 cuts the steering wheel 1, which compares the sign of the output angular velocity theta _p ^· a sign of the output angle theta _p. sign (θ _p ^· ) = sign (θ _p )
Indicates that the steering wheel 1 is being turned. sign (θ _p ^· ) ≠ sign (θ _p )
Indicates that the steering wheel 1 is being returned.

[0137] Step S1320: the EMPS target current EMPS target current is output from the calculation unit 23 I _a ^~ and additional output from the AF increase logic unit 33 EMPS target current DI _a is added. As a result, it EMPS target current (updated value) I _a ^~~ is obtained. That is, I
_{a to} are determined according to ( ^Equation 37).

[0138]

Equation 37] _{^{I a ~~ = I a ~ +}} DI a step S1330: EMPS motor drive circuit 26,
Current flowing through the motor 12a drives the motor 12a so as to approach the EMPS target current (updated value) I _a ^~~.

[0139] Step S1340: Torque - current converter 20 converts the torque command value T _opt VGRS target current I _F ^~ a.

[0140] Step S1350: VGRS motor drive circuit 21, current flowing in the motor 4a drives the motor 4a so as to approach the ^~ VGRS target current I _F.

As described above, according to the steering device 400, the EMPS target current I near the maximum turning angle is obtained.
_a current DI _a is added to the ^~. Thus, as the rack 8 approaches the stopper 16a (or 16b) (that is, as the steered wheel steering angle approaches the maximum steering angle).
Assist torque is reduced so that the output angular velocity θ _p ^· is reduced. As a result, the rack 8 is moved to the stopper 16a (or 1
The impact when colliding with 6b) is reduced.

[0142]

According to the steering apparatus of the present invention, since the variable <br/> current flowing through the motor of the variable gear ratio actuator is based on a squirrel tearing steering angle by be limited steerable wheel turning angle control Gear ratio actuator required for
Even if by the torque is insufficient, it is possible to compensate the torque of the shortfall by the torque by the power assist actuator. As a result, it is possible to prevent the following characteristic of the variable gear ratio actuator from being deteriorated due to the current limitation (torque limitation).

According to another steering apparatus of the present invention, the variable gear ratio actuator is feedforward controlled based on the output of the torque sensor and the target current of the power assist actuator. As a result, a quick response can be realized even in the early stage of steering with a small deviation e.

[0144]

[Brief description of the drawings]

FIG. 1 shows a steering device 10 according to a first embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a zero.

FIG. 2 is a diagram showing a configuration of an EMPS / VGRS controller 17 according to the first embodiment.

FIG. 3A is a control flowchart showing a procedure of a process of a VGRS system among processes executed by an EMPS / VGRS controller 17;

FIG. 3B is a control flowchart showing a procedure of processing of the EMPS system among the processing executed by the EMPS / VGRS controller 17;

FIG. 3C is a control flowchart illustrating a procedure of a process for integrating the EMPS system and the VGRS system.

FIG. 4 is a diagram illustrating a relationship between a frequency of a transfer function W (s) and a gain.

FIG. 5 is a diagram showing a configuration of a compensator 19;

FIG. 6 is a diagram showing a configuration of an EMPS / VGRS controller 17 according to the second embodiment.

FIG. 7 is a control flowchart showing a procedure of a process for integrating the EMPS system and the VGRS system.

FIG. 8 is a diagram showing a configuration of an EMPS / VGRS controller 17 according to the third embodiment.

FIG. 9 is a control flowchart showing a procedure of a process for integrating the EMPS system and the VGRS system.

FIG. 10 is a view showing a spring-mass-damper model of a steering system.

FIG. 11A is a diagram showing a state in which an output angle θ _p follows an output angle target value θ _p ^〜 by conventional control.

FIG. 11B is a diagram showing a state in which the output angle θ _p follows the output angle target value θ _p ^〜 by the control of the present invention.

FIG. 12 is a diagram showing a configuration of an EMPS / VGRS controller 17 according to a fourth embodiment.

FIG. 13 is a control flowchart showing a procedure of a process for integrating the EMPS system and the VGRS system.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 input angle sensor 3 torque sensor 4 variable gear ratio actuator 4a VGRS motor 5 output angle sensor 6 gear 7 pinion shaft 8 rack 9a, 9b tie rod 10 steering wheel turning mechanism 12 power assist actuator 12a EMPS motor 12b gear 13 vehicle speed sensor 16a, 16b Stopper 17 EMPS / VGRS controller 100 Steering device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B62D 125: 00 B62D 125: 00 137: 00 137: 00 (56) References JP-A-5-77751 (JP, A) JP JP-A-6-336164 (JP, A) JP-A-5-105103 (JP, A) JP-A-3-239670 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 5 / 00 B62D 6/00

Claims (2)

(57) [Claims] A variable gear ratio actuator as 1. A variable steering wheel steering angle to the steering angle, a steering system and a power assist actuator which applies a steering assist force to a steering system, based on the scan tearing steering angle the torque due to the variable gear ratio actuator required to the steering wheel steering angle control
By limiting the current flowing through the variable gear ratio actuator
When the power is insufficient, a current corresponding to the insufficient torque is supplied to the power.
-The insufficient torque is passed to the assist actuator
By the torque by the power assist actuator
Steering device to compensate . 2. A steering device comprising: a variable gear ratio actuator for varying a steering wheel turning angle with respect to a steering angle; and a power assist actuator for applying a steering assist force to the steering device. A steering device that is feedforward controlled based on an output of a torque sensor and a target current of the power assist actuator.