JP2548293B2 - Vehicle drive controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle running control device including a four-wheel steering control mechanism and a front-rear wheel driving force distribution control mechanism for four-wheel drive.

(Prior Art) For a vehicle using this type of conventional vehicle travel control device, for example, Japanese Patent Application No. 63-226 is available for four-wheel steering (4WS).
There is one described in specification No. 86, 4 wheel drive (4WD)
The driving force distribution control of the vehicle is described in, for example, Symposium of the Society of Automotive Engineers of Japan "Application of control theory and vehicle control" P41 (published in 1986) and installed in the Nissan Cue-X.
There is one described in Japanese Patent Application No. 63-33892. The former is a torque-split 4WD vehicle that uses an electronic control system and uses a full-time 4WD with a hydraulic multi-plate clutch in the middle of the front-wheel drive shaft. Since the torque capacity of the hydraulic multi-plate clutch is almost proportional to the applied hydraulic pressure, the hydraulic multi-plate clutch is used as a torque limiting device by changing the applied hydraulic pressure in various ways. That is, if the torque capacity of the hydraulic multi-disc clutch is Tc and the transmission output torque is T, the torque distribution to the front wheels and the rear wheels is approximately Tc: (T-Tc), so the torque T (or (According to this) and adjust the applied oil pressure to properly set Tc, that is, if the vehicle running state is identified and selected based on the information from the wheel rotation speed sensor and the accelerator opening sensor, the desired Tc Torque distribution is obtained. However, since the rear wheel drive system has no hydraulic clutch and is directly connected, it cannot be changed to the FF vehicle state.

(Problems to be Solved by the Invention) The vehicle running control device employing the 4WS system or the 4WD system described above performs electronic or mechanical running control in consideration of running stability independently of the system when the system fails. Some have a fail-safe function. However such 4WS system or 4WD
In a vehicle that adopts the system, the characteristics are based on the assumption that both the 4WS and 4WD systems operate normally.Since the effect on the other system when one system fails was not considered, one system If the fail-safe function operates when the vehicle fails, there is a problem that the running stability is impaired as the operation of the entire vehicle in combination with the operation of the other normal system.

(Means for Solving the Problem) The present invention is a vehicle running control device for controlling a 4WS or 4WD system, which intends to solve the above-mentioned problem by taking in system fail information. In a vehicular travel control device for a vehicle having a front and rear wheel drive type distribution control mechanism for four-wheel drive, when one of the four-wheel steering control mechanism and the front and rear wheel drive distribution control mechanism fails, based on fail information. It is characterized in that the other control mechanism during normal operation is operated so as to adjust the steering characteristic in the understeer direction.

(Operation) When a vehicle equipped with a four-wheel steering control mechanism and a four-wheel drive front / rear wheel drive force distribution control mechanism is running normally with both control mechanisms operating and one of them fails. Fails information is input to the vehicle travel control device. Based on this, the vehicle travel control device operates the other normally operating control mechanism so as to adjust the steering characteristics in the understeer direction.Therefore, a fail-safe function that secures traveling stability as an operation of the entire vehicle is provided. It is possible to realize an extremely safe vehicle travel control device.

(Example) Hereinafter, the Example of this invention is described in detail based on drawing.

FIG. 1 is described in the above-mentioned Japanese Patent Application No. 63-33892 and shows a wheel drive system and a rear wheel auxiliary steering system of a vehicle used for implementing the device of the present invention. 1L, 1R in the figure are front wheels, 2L,
2R is a rear wheel and 3 is a steering wheel.

First, a wheel drive system will be described. Reference numeral 4 denotes an engine, 5 denotes a transmission, and transmission power from the engine 4 through the transmission 5 always reaches the rear wheel differential gear 7 through the propeller shaft 6.
Drives rear wheels 2L and 2R. On the other hand, the speed change power from the transmission 5 appropriately reaches the front wheel differential gear 10 via the propeller shaft 9 by the front wheel drive clutch 8 and is used for driving the front wheels 1L, 1R.

Next, in order to explain the steering system of the vehicle, the front wheels 1L and 1R are respectively operated by the steering wheel 3 as usual in the steering gear.
Steering is possible via 11, and the rear wheels 2L and 2R are steerable by a rear wheel steering actuator 12.

The actuator 12 is a spring center type hydraulic actuator, and the rear wheels 2L and 2R are respectively auxiliary-steered to the right by a steering angle proportional to the pressure when the hydraulic pressure is supplied to the chamber 12R, and are proportional to the pressure when the hydraulic pressure is supplied to the chamber 12L. It is assumed that the rear wheels 2L and 2R are auxiliary steered to the left by the steering angle.

An electromagnetic proportional rear wheel steering control valve 13 for controlling the hydraulic pressure to the actuator chambers 12L, 12R is provided, and this valve 13 has a variable throttle 13a,
13b, 13c, 13d are connected by a bridge, and a pump 14, a reservoir 15 and an actuator chamber 12L,
Oil lines 16 and 17 from 12R are connected respectively. The valve 13 is further provided with solenoids 13L and 13R.When these solenoids are OFF, the variable throttles 13a, 13b and 13c and 13d are fully opened to make both actuator chambers 12L and 12R non-pressurized (equilibrium state). Variable throttle when ON by the current value I _L or I _R of
13c, 13d or 13a, 13b and shall be squeezed into opening corresponding to the current value to supply the hydraulic pressure corresponding to the current value I _L or I _R to an actuator chamber 12L or 12R. As described above, the hydraulic pressure assists the rear wheels in the corresponding direction by an angle corresponding to the value.

The front wheel drive clutch 8 directs a torque corresponding to the clutch pressure P _C to the front wheels, and the clutch pressure P _C is controlled by the electromagnetic proportional pressure regulating valve 18. The valve 18 normally keeps the clutch pressure P _C at zero, and as the drive current I _C of the solenoid 18a increases, the pressure of the pump 14 is directed to the clutch 8 to increase the clutch pressure P _C.

The drive currents I _L , I _R , and I _C of the solenoids 13L, 13R, and 18a are controlled by a controller 19, respectively, and a signal from a steering angle sensor 20 that detects a steering angle θ and a wheel are supplied to the controllers.
In addition to the signals from the wheel rotation sensors 21L, 21R, 22L, 22R that detect the rotation speeds ω _f1 , ω _f2 , ω _r1 , and ω _r2 of 1L, 1R, 2L, 2R, the vehicle speed V
The signal from the vehicle speed sensor 23 for detecting the above and the signal from the throttle opening sensor 24 for detecting the throttle opening TH are respectively input. Based on these input information, the controller 19 functions as shown in FIGS. 3 and 4 at regular intervals Δt to control the solenoid drive current I _C (front wheel drive force control, that is, front and rear wheel drive force distribution control) and solenoid drive current. I _L , I _R control (rear wheel auxiliary steering) shall be performed.

The controller 19 has a 4WS controller 19a and a 4WD controller 19b as shown in detail in FIG.
S Sail signal, 4WD fail signal) shall be exchanged. Although the controllers 19a and 19b are separate types here, they may be integrated controllers.

First, the flow chart of the front and rear wheel drive force distribution control of the four-wheel drive shown in FIG. 3 will be described. In step 51, the normal drive force distribution control, that is, the read steering angle .theta. By the method described in the specification of 63-33892, 4WD control is performed to determine the optimum front / rear wheel driving force distribution ratio according to the running conditions and road surface conditions. Next in step 52 it is determined whether or not the 4WS system is failing by the presence or absence of a 4WS fail signal, and if it is determined that it is 4WS fail, after correcting the driving force distribution ratio so that the driving force of the front wheels is increased in step 53, Control proceeds to step 55. If it is determined in step 52 that the 4WS is operating normally, step 5
After the correction value is set to zero in 4 to determine the driving force distribution ratio, the control proceeds to step 55.

In step 55, the sensors required to control the 4WD system,
Whether or not the 4WD system has failed is determined depending on whether or not the solenoid has failed. If it is determined that the 4WD system has failed, in step 56 it is decided to stop the 4WD control, and in step 5
7 outputs a 4WD fail signal to the 4WS controller 19a.

On the other hand, when it is determined in step 55 that the 4WD is in normal operation, in step 58, the front and rear wheel drive forces are duty-controlled so that the drive force distribution ratio obtained in step 53 or 54 is obtained. The drive current I _C is output to the solenoid 18a of the proportional pressure regulating valve 18. Step 57,
After 58, control returns to step 51 for repeated execution.

With the above-mentioned 4WD control, the 4WS system fails with 4W.
When the D system is operating normally, 4WD control is performed to increase the driving force of the front wheels, so the clutch 8 transmits an appropriate torque to the front wheels by the clutch pressure P _C controlled to a corresponding value, and The steering characteristics can be adjusted in the understeer direction by making the driving force distribution appropriate, and the running stability of the vehicle can be improved.

Next, the flow chart of the four-wheel steering control of FIG. 4 will be described. In other words, in step 71, the steering angle θ of the steering wheel and the vehicle speed V are read, and in the next step 72, the normally ideal motion performance of the vehicle is obtained. Then, the yaw rate gain characteristic with respect to the steering frequency becomes flat, that is, the rear wheel proportional constant K and the rear wheel differential constant τ are set so that the yaw rate is generated in proportion to the front wheel steering without phase delay regardless of the steering speed. Calculate from the vehicle speed V, and then calculate the time constant Tr for the rear wheels Calculate with.

Next, at step 73, it is determined whether or not the 4WD system is failing based on the presence or absence of the 4WD fail signal. If it is determined as 4WD fail, the proportional constant K is set to K = K + ΔK at step 74.
As the correction of increasing the in-phase control, the correction of decreasing the differential constant τ to τ = τ−Δτ, or the correction of τ = 0, the control proceeds to step 76.
If it is determined in step 73 that the 4WD is operating normally, in step 75 the correction value is set to zero and the constants K, τ and Tr are determined, and then
Control proceeds to step 76.

In step 76, the constant K obtained in steps 71, 74, and 75,
Based on τ and Tr, rear wheel auxiliary steering angle δ _r Calculate with. Here, the formula (2) is a formula showing an example of the rear wheel auxiliary steering angle calculation formula, but instead δ _r = Kθ (proportional control), δ _r = (K−τ · S) θ (first-order advance control), (Front / rear wheel actual steering ratio primary / as described in Japanese Utility Model Publication No. 62-23773)
Primary control, but B _f , B _r , τ _f , τ _r are functions of vehicle speed, and δ _f is a front wheel steering angle) or the like.

In the next step 77, the sensor necessary for controlling the 4WS system, the presence or absence of the failure of the 4WS system is determined by whether or not the solenoid is failing, and when it is determined that the 4WS failure is determined to stop the 4WS control in step 78, In step 79, the 4WS fail signal is output to the 4WD controller 19b.

On the other hand, if it is determined in step 77 that the 4WS is operating normally, the rear wheels are controlled by the rear wheel auxiliary steering angle δ _r obtained in step 76 based on the correction value in step 74 or 75 in step 80. Driving currents I _L and I _R are output to solenoids 13L and 13R of an electromagnetic proportional rear wheel steering control valve 13 that operates a rudder actuator 12, respectively. After steps 79 and 80, the control returns to step 71 and is repeatedly executed.

With the 4WS control described above, the 4WD system fails at 4W.
When the S system is operating normally, the steering characteristics are adjusted in the understeer direction by performing 4WS control such that the rear wheel auxiliary steering angle δ _r is increased and the in-phase control amount is increased. It is possible to improve the sex.

The above-mentioned 4WD control and 4WS control will be qualitatively described.

First of all, the 4WD control is described in "Basic Automotive Engineering (Part 2)" P29-39 (written by Masaichi Kondo, June 1979).
As described in, the static stability dM / dβ (where M; static restoring moment,
β; posture change angle). This value dM / dβ is (However, T: total vehicle driving force, α: front wheel driving force distribution,
l ₁ , l ₂ , C ₁ , C ₂ ; constant determined by vehicle specifications) If so, stable (corresponding to understeer tendency), If so, it becomes unstable (corresponding to oversteer tendency). Therefore, when the driving force T is positive, the static stability dM / dβ increases as the front wheel driving force distribution α increases, and the static stability also increases (understeer tendency).

Next, regarding 4WS control, for example, Nissan Cue-X
Then, when the 4WD system fails and the clutch is off,
The vehicle drive force type becomes FR (rear wheel drive force distribution 100%), which reduces vehicle stability. In this case 4W
If the proportional constant K is increased by the S control, the steady gain of yaw rate and the yaw rate phase delay are reduced from the solid line in the figure to the dotted line as shown in the steering response characteristic diagram of four-wheel steering in FIG. 4WD because it improves
It is possible to obtain vehicle characteristics with improved stability that compensate for the effects of system failures. Also, by reducing the gain by decreasing the differential constant τ to τ = τ-Δτ or τ = 0 by 4WS control, the vehicle characteristics with similarly improved stability can be obtained (however, the steering response gain is slightly reduced. To).

If the 4WS system fails and becomes 2WS control, the understeer tendency weakens and the steering response gain increases as shown by the alternate long and short dash line in FIG. 5, which may cause the driver to feel uncomfortable. The problem can be solved by the effect of increasing the front wheel drive distribution of the 4WD control.

(Effect of the invention) Thus, the vehicle travel control device of the present invention is as described above.
Since the fail information of one control mechanism of the four-wheel steering control mechanism and the front-rear wheel drive distribution control mechanism of four-wheel drive is fetched and the other normal control mechanism is operated so as to adjust the steering characteristics in the understeer direction. Thus, it is possible to realize an extremely safe vehicle travel control device having a fail-safe function for ensuring traveling stability as an operation of the entire vehicle.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a vehicle used in an embodiment of the device of the present invention, FIG. 2 is a diagram showing details of a traveling control device of this embodiment, and FIGS. 3 and 4 are four-wheel steering respectively. FIG. 5 is a flow chart showing control and front-rear wheel driving force distribution control of four-wheel drive, and FIG. 5 is a characteristic diagram showing steering response characteristics of four-wheel steering. 1L, 1R …… front wheel, 2L, 2R …… rear wheel 3 …… steering wheel 4 …… engine 5 …… transmission 6 …… propeller shaft 7 …… rear wheel differential gear 8 …… front wheel drive latch, 9… … Propeller shaft 10 …… Differential gear for front wheels 11 …… Steering gear 12 …… Rear wheel steering actuator 13 …… Electromagnetic proportional rear wheel steering control valve 14 …… Pump, 18 …… Electromagnetic proportional pressure regulating valve 19 …… Controller , 20 …… Steering angle sensor 21L, 21R, 22L, 22R …… Wheel rotation sensor 23 …… Vehicle speed sensor 24 …… Throttle opening sensor

Claims (1)

(57) [Claims] 1. A vehicle running control device for a vehicle, comprising a four-wheel steering control mechanism and a front-rear wheel drive force distribution control mechanism for four-wheel drive, comprising: A vehicle running control device characterized in that, when one fails, the other control mechanism during normal operation is operated so as to adjust the steering characteristic in the understeer direction based on the fail information.