JPH0374279A - Auxiliary steering device of vehicle - Google Patents

Abstract

PURPOSE:To prevent the rapid change of the behavior of a vehicle just after change of standard model by starting the calculation of a target behavior based on the standard model after the change with the target behavior just before the change as an initial value at the time of the change of standard model. CONSTITUTION:A rear wheel steering angle calculating part 6 inputs vehicle speed V and front wheel steering angle, calculates a target behavior of the vehicle according a standard model 21 at the time of steering front wheels, and conducts auxiliary steering of rear wheels 2 to obtain this target behavior by a rear wheel steering angle control part 14 through a self vehicle model 12. When a control constant changing command of the standard model 21 is outputted from a control constant setting part 22, a standard model change control part 23 makes the standard model 21 execute the change content, and also informs a state variable holding part 24 to hold the state variable before the change in the standard model 21. The standard model 21 starts the calculation of the target behavior after the change with the target behavior just before the change as an initial value. Hence, the rapid change of the vehicle behavior just after the change can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an auxiliary steering device for a vehicle that performs auxiliary steering of at least one of a front wheel and a rear wheel during front wheel steering.

(Prior art) This type of device is capable of controlling vehicle behavior (yaw rate, etc.) during front wheel steering.
This system performs auxiliary steering so that the desired behavior is achieved, and Japanese Patent Laid-Open No. 61115 discloses a system that allows the target behavior to be changed manually or automatically depending on preference and driving conditions.
This method has been proposed in Publication No. 776.

This is as shown in Fig. 7, where LL and IR represent left and right front wheels, 2L and 2R represent left and right rear wheels, and the front wheels are steered by a steering wheel 3 via a steering gear 4, and the rear wheels are steered by an actuator 5. Steering. In order to control the steering angle of the rear wheels, a rear wheel steering angle calculating section 6 is provided, which includes a steering angle sensor 7 that detects the steering wheel steering angle θ.
The signals from the vehicle speed sensor 8 and the vehicle speed sensor 8 which detects the vehicle speed V are manually generated.

The calculation unit 6 includes a first calculation unit that determines the target behavior of the vehicle. It consists of a second reference model 9.10, a switching unit 11 for selecting these models, and an own vehicle model 12 for determining the rear wheel steering angle δ to obtain the target behavior. Do this in 13. Both reference models 9°■0 calculate different target behaviors from the steering angle θ and vehicle speed V, and the switching unit 11 selects the target behavior commanded by the knob 13 from among these target behaviors. The dead weight model 12 is the rear wheel steering angle δ to obtain this target behavior.

is calculated, and the rear wheel steering angle control unit 14 steers the rear wheels by δ via the actuator 5, thereby achieving the target behavior of the vehicle.

(Problem to be Solved by the Invention) However, according to the conventional configuration, when the reference model is switched using the knob 13 while driving, the rear wheel steering angle is changed from the rear wheel steering angle based on the reference model before switching to the reference model after switching. The rear wheel steering angle suddenly changes to the base rear wheel steering angle, and the change in vehicle behavior does not occur smoothly and becomes unnatural.

For example, as shown by the solid line in Figure 6, V = 150 km/h
, the reference model is switched at instant 1+ while maintaining θ-30 degrees. Immediately after instant tl, a sudden change in the rear wheel steering angle occurs, and the vehicle's yaw rate (behavior) also smoothly changes to the target after switching. It is not a behavior and is unnatural.

Therefore, as shown in Japanese Patent Application Laid-Open No. 64-43468, a technology is proposed that allows the above switching only when the state variable (behavior change) related to the planar motion of the vehicle is small and does not cause a sudden change in the rear wheel steering angle. has also been proposed previously.

However, in this case, the switching will not be executed unless the above-mentioned permission conditions are met, and there is a problem in that the vehicle behavior as instructed cannot be immediately obtained.

According to the present invention, when changing the reference model, the target behavior immediately before the change is used as an initial value to calculate the subsequent target behavior, so that the change can be executed immediately without causing a sudden change in the auxiliary steering angle. The purpose is to obtain the above-mentioned problems and to solve all the problems mentioned above.

(Means for Solving the Problems) For this purpose, the auxiliary steering device of the present invention provides:
A model change command detection means for detecting a change command of the reference model in a vehicle that performs auxiliary steering of at least one of a front wheel and a rear wheel so as to obtain a target behavior calculated based on a reference model that can be changed in various ways; The present invention is constructed by providing calculation initial value setting means for providing the target behavior immediately before the change to the changed reference model as the target behavior calculation initial value when a change is commanded.

(Function) When steering the front wheels, the target behavior of the vehicle is calculated based on the reference model, and the front and rear wheels are auxiliary steered to achieve this target behavior. Note that when the reference model is changed, the target behavior of the vehicle changes accordingly, and various vehicle behaviors can be obtained by auxiliary steering.

When a command is issued to change the reference model, in response to the model change command detection means that detects this command, the calculation initial value setting means calculates the target behavior immediately before the change into the changed reference model. Give as initial value. Therefore, the changed reference model gradually changes the target behavior from the value immediately before the reference model change to the predetermined value after the change, and the reference model change is immediately executed without causing a sudden change in the auxiliary steering angle. be able to.

(Example) Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention apparatus which performs auxiliary steering of the rear wheels, in which the same parts as in FIG. 7 are designated by the same reference numerals. Therefore, in this example, the reference model is changed by changing the control constants (steady-state gain, time constant, etc.) within one reference model 21, rather than by switching the selection of multiple models. .

For this reason, a control constant setting section 22 is provided to output a command to change the control constants of the reference model 21 manually or automatically. Upon receiving this command, the reference model change control unit 23 causes the reference model 21 to execute the change, and at the same time notifies the state variable (target behavior such as yaw rate) holding unit 24 that there is a change command. The state variable holding unit 24 holds the state variables (target behavior) in the reference model 21 before the change when a change command is issued. Based on the content changed as described above, the reference model 21 starts calculating the target behavior after the change, using the target behavior immediately before the change in the state variable number holding unit as an initial value.

Of course, thereafter, the state variable holding unit 24 holds the calculation result for the next calculation every time the calculation is completed.

The operation of the above embodiment will now be explained based on the flowchart of FIG.

In step 31, the rear wheel steering angle calculation unit 6 calculates the steering angle θ and the vehicle speed V.
, and in step 32 create a normative model 21 from these.
Based on the target yaw rate (target behavior) ψ, calculate the rear wheel steering angle δ□ to obtain the following equation.

Calculate using the following formula... (2) v, =, f LVy - dt Cp = eKp (θ/ N - (Vy+Lp ・ψ)
/V)-(3)CR=(2Lp-Cp I□ ・
ψ) / 2LR (2CF + 2C++) / M −V ・
tpδR=CR/KR+(V, -L1ψ)N...
(6) ...(5) ...(4) Set. In the next step 33, the target yaw rate and the rear wheel steering angle δ to be given, which are determined in this way based on the vehicle model 12 from the target yaw rate, are outputted to the rear wheel steering angle control section 14 in step 34. As a result, the rear wheel steering angle control section 14 steers the rear wheels by the above-mentioned amount δ1 via the actuator 5 to generate the target yaw rate ψ.

In step 35, the above loop is processed every fixed time Δ, and steps 36 to 39 are executed during other times.

In step 36, it is checked whether there is a command to change the reference model 21 by the control constant setting unit 22 [to change τ and C(V) in the above equation (1)], and if there is no change command, step 37 is performed. Do not execute steps 39 to 39.

When there is a command to change the reference model, the current target yaw rate ψ, that is, immediately before the change, is held in the state variable holding unit 24 in step 37. In the next step 38, the normative model 2
1 is the control constant part τ in the above formula (1).

C(V) is rewritten to be as changed by the control constant setting section 22. Then, in step 39, the target yaw rate value immediately before the reference model change held in step 37 is substituted into the initial value ψ(0) used in the calculation of the next target yaw rate using equation (1).

Therefore, when changing the norm model, initially step 32 is based on the norm model 21 rewritten in step 38.
Also, the target yaw rate ψ immediately before the change set in step 39
Using Equation (1) above, the target yaw rate at the beginning of the change is determined, and in steps 33 and 34 the rear wheels are steered so as to obtain this target yaw rate.

Therefore, while the vehicle with the specifications shown in Table 0 is running at a vehicle speed of V=150 km/h, the control constant C(V) of the reference model 21.

As is clear from the dotted line in Figure 6, which shows the simulation results when τ is changed as shown in the table below, after the reference model change command instant t, both the rear wheel steering angle and the vehicle yaw rate are changed from the values immediately before the change to the initial values. It smoothly settles to the predetermined value after the change. Therefore, even at the time of the change, the rear wheel steering angle does not suddenly change, and it is possible to prevent unnatural vehicle behavior from occurring. In addition, since the reference model is immediately changed by unconditionally directing the rear wheel steering angle from the change command instantaneous tl to the predetermined value after the change, it is difficult to know when the target behavior according to the change cannot be obtained. There is no problem that the process continues for a long time.

FIG. 3 shows another example of the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals. In the examples shown in Figures 1 and 2, if the time required to change the standard model 2■ is longer than △t + δ, calculation time + ψ calculation time in steps 32, 33, and 35 in Figure 2, the calculation of δ8 will be performed as set. △ cannot be performed every time, and as a result, the behavior of the vehicle may become unnatural. The example in Figure 3 solves this problem by using the first normative model 2.
1a and a second reference model 21b are provided, and the state variable holding section is also divided into two, a state variable holding section 24a for these models and a state variable holding section 24b for the own vehicle model 12, and the state variable holding section 24b for the own vehicle model 12 is divided into two. Target yaw rate ψ1. from models 21a, 21b. A switching unit 25 is provided that selects ψ2 and sets the selected target yaw rate ψ. This switching section 25
is controlled by the reference model change control section 23 together with the state variable holding sections 24a and 24b. For the above purpose, while one of the reference models 21a or 21b is calculating ψ, the rewriting prohibition unit 26 prevents changes in the reference model during the calculation using a signal from the reference model change control unit 23. It will be prohibited accordingly.

The operation of this embodiment will now be explained based on the flowcharts of FIGS. 4 and 5.

FIG. 4 shows the calculation process of the target rear wheel steering angle which is repeatedly executed by interrupting every predetermined time Δ, and in step 41, the steering angle θ and the vehicle speed V are read. In the next step 42, it is checked from the flag FLG whether the switching section 25 has selected the first reference model 21a or the second reference model 21b.

If the first reference model is being selected, the target yaw rate φ is calculated from the steering angle θ and the vehicle speed V based on this in step 43, and if the second reference model is being selected, the steering angle is determined based on this in step 44. The target yaw rate is determined from θ and the vehicle speed V. These φ1. The switching unit 12 selects ψ2 in steps 45 and 46 to set it as the target yaw rate ψ to be used this time. In the next step 47, the rear wheel steering angle δ that provides the target yaw rate ψ obtained as described above is calculated based on the own vehicle model 12, and in step 48, the rear wheel steering angle control unit Output to. After performing the above processing, control returns to the main routine shown in FIG.

In the main routine shown in FIG. 5, first, in step 51, it is determined whether or not there is a command to change the standard model, that is, whether or not the control constant setting unit 22 has been operated to instruct the standard model change control unit 23 to change the standard model. do. This determination is continued until a change command is issued, and when a change command is issued, the reference model is rewritten as follows.

That is, first in step 52, from the flag FLG to the switching unit 25
It is determined whether the user selects the first reference model 21a or the second reference model 21b. If the first reference model is being selected, in step 53, the reference model change control unit 23 (control constant setting unit 22
), the unselected second reference model 21b is rewritten, and rewriting of the first reference model 21a is substantially prohibited. Then, in step 54, the target yaw rate ψ2 is calculated based on the second reference model rewritten in this way.
．． At this time, in step 54, the target yaw rate ψ immediately before the standard model change, that is, φ1, is held and set as the initial value φ2(0) of the calculation. Next step 1. At step 56, the flag FLG is reset to O so that the switching unit 25 selects the second reference model 21b based on the start of the calculation.

If it is determined in step 52 that the second reference model is being selected, in steps 57 to 59 the first reference model 21 that is not selected is
The same process as described above is performed on H, and rewriting of the second reference model 21b being selected is prohibited, and step 60
Then, the switching unit 25 sets the flag FLG to 1 so that the first reference model 21a is selected.

Therefore, in this example, as in the above-mentioned example, when a reference model change command is issued, execution of the change can be started immediately, and sudden changes in behavior can be prevented when the change is made. . In addition, in this example, the two reference models 21a and 21b are selectively used to calculate the target yaw rate, and when a reference model change command is issued, the unselected reference models are rewritten in accordance with the change command. Since the selected reference model is prohibited from being rewritten, the calculation of the rear wheel steering angle corresponding to the target yaw rate can be reliably performed every calculation cycle Δ in Figure 4, and the behavior of the vehicle can be improved. It can prevent it from becoming unnatural.

(Effects of the Invention) Thus, as described above, the auxiliary steering system of the present invention is configured so that when the reference model is changed, the calculation of the target behavior based on the changed reference model is started using the target behavior immediately before the change as the initial value. It is possible to prevent the vehicle behavior from suddenly changing immediately after the change, and therefore there is no need to wait until the sudden change stops occurring before executing the change, and the change can be started immediately upon command.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing one embodiment of the auxiliary steering device of the present invention; Fig. 2 is a functional flowchart of the same example; Fig. 3 is a system diagram similar to Fig. 1 showing another example of the present invention; 4 and 5 are functional flowcharts of the same example, FIG. 6 is a time chart showing a comparison of the rear wheel steering angle and yaw rate between the device of the present invention and the conventional device, and FIG. 7 is a system diagram of the conventional device. LL, IR...front wheel 2L, 2R...rear wheel 3...steering wheel 4...steering gear 5...rear wheel steering actuator 6...rear wheel steering angle calculation unit 7...steering Angle sensor 8・
...Vehicle speed sensor 12... Own vehicle model 21, 21
a, 21b - Normative model 22... Control constant setting section 23... Normative model change control section 24, 24a, 24b... State variable holding section 25...
・Switching part 26... Rewriting prohibited part 7 @3 Figure 74279 (7) Figure 7

Claims (1)

[Claims] 1. In a vehicle that performs auxiliary steering of at least one of the front wheels and rear wheels so that a target behavior calculated based on a variously changeable standard model is obtained when the front wheels are steered, the standard model is changed. The present invention is characterized by comprising a model change command detection means for detecting a command, and a calculation initial value setting means for giving the target behavior immediately before the change to the changed reference model as the target behavior calculation initial value when the change command is issued. Vehicle auxiliary steering device.