JP3584315B2 - Control method of vehicle anti-lock brake system - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to control of an anti-lock brake system (ABS) for preventing locking (sticking) of wheels at the time of sudden braking of a vehicle. More specifically, the present invention relates to a road surface friction force or an accurate road surface mixed with a crosstalk amount such as a brake torque. The present invention relates to a road surface μ determination method for performing stable ABS control determination from the start of ABS control using a stress sensor capable of obtaining an output proportional to frictional force and brake torque.
[0002]
[Prior art]
In the control of the conventional anti-lock brake system (ABS), the control is started with an appropriately assumed control method and control set value, and the road surface μ is re-estimated by measuring the frequency of occurrence of wheel slip during the control, When the wheel slip occurs frequently, the control is shifted to a lower μ control, and when the wheel slip does not occur, it is considered that the braking force is insufficient, and the control is switched to a higher μ control. However, when such control is performed, the braking force during a wheel slip on a low μ road surface or the braking force loss while the braking force is set conservatively on a high μ road surface is large, and the braking distance is large. The result is a problem.
[0003]
[Problems to be solved by the invention]
In view of the above-mentioned problems of the conventional example, the present invention provides a hole in the axle or in the vicinity of the axle, embeds a stress sensor formed of a strain gauge in this hole, and directly detects the stress generated in the axle or in the vicinity of the axle by the wheel acting force by the stress sensor. By monitoring the behavior of the road surface frictional force, the road surface μ is determined at the same time as the ABS control is started or before the control is started, and optimal ABS control corresponding to the road surface μ is performed from the beginning of the control. The purpose is.
[0004]
[Means for Solving the Problems]
According to the first aspect of the present invention, a stress sensor is mounted in a hole provided in the axle or in the vicinity of the axle, in which two strain gauges are respectively crossed and attached to two upper and lower opposing surfaces of the substrate, The four strain gauges constituting the stress sensor are assembled in a bridge circuit, and a control method or a control set value of a preset brake pressure is automatically selected according to a peak value of an output of the bridge circuit. I do. According to the present invention, a stress sensor is mounted in a hole provided in the axle or in the vicinity of the axle, in which four strain gauges are attached to each other by crossing two strain gauges on two opposite upper and lower surfaces of the substrate, Four strain gauges constituting the stress sensor are assembled in a bridge circuit, and a preset brake pressure control method or a preset brake pressure corresponding to the output value of the bridge circuit at the time when the first differential value of the output of the bridge circuit reaches a peak or The control setting value is automatically selected. In a third aspect of the present invention, a stress sensor is mounted in a hole provided in the axle or in the vicinity of the axle. The four strain gauges constituting the stress sensor are assembled in a bridge circuit, and from the road surface frictional force value at the time when the second derivative of the output of the bridge circuit changes to a negative value, before the output of the bridge circuit reaches a peak. The present invention is characterized in that a maximum road surface friction coefficient is predicted and a preset brake pressure control method or control set value is automatically selected in accordance with the maximum road surface friction coefficient prediction value.
[0005]
[Action]
According to the first aspect of the present invention, a stress sensor in which four strain gauges are respectively crossed and attached to two opposing upper and lower surfaces of a substrate is mounted in an axle or a hole provided near the axle. By assembling the four strain gauges constituting the stress sensor into a bridge circuit and automatically selecting a preset brake pressure control method or control set value in accordance with the peak value of the output of the bridge circuit. Optimal ABS control adapted to the road surface can be realized from the start of the control. According to the second aspect of the present invention, a stress sensor is mounted in a hole provided in the axle or in the vicinity of the axle. Then, four strain gauges constituting the stress sensor are assembled in a bridge circuit, and a preset brake pressure control is performed in accordance with the output value of the bridge circuit at the time when the first derivative of the output of the bridge circuit reaches a peak. By automatically selecting the method or the control set value, it is possible to perform the ABS control without causing the wheel slip at the control start time due to the control delay. According to the third aspect of the present invention, a stress sensor in which four strain gauges are crossed and mounted on two opposing upper and lower surfaces of a substrate is mounted in an axle or a hole provided near the axle. Then, four strain gauges constituting the stress sensor are assembled in a bridge circuit, and the strain gauges are preset in accordance with the output value of the bridge circuit at the time when the second derivative of the output of the bridge circuit changes to a negative value. By automatically selecting the control method or the control set value of the brake pressure, it is possible to perform the ABS control without causing the wheel slip at the control start time due to the control delay.
[0006]
【Example】
What is shown here is an example of a preferred embodiment, and the claims are not limited to the examples shown here.
An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the measured values of the road surface frictional force F (a, b, c) obtained immediately after the start of the brake pressurization obtained from the stress sensor used in the present invention, and the first derivative F ′ and the second derivative F ″ thereof. 3 shows an example of a time change. The measured values F, a, b, and c correspond to the maximum road surface friction coefficient, respectively, and have a characteristic that the peak signal increases as the road surface has a higher maximum road surface friction coefficient. FIG. 2 shows a functional system diagram.
Immediately after the start of braking at t0 in FIG. 1, the measured value of road surface friction force F measured by the road surface frictional force F detecting means 1 comprising a stress sensor is, as shown in FIG. Then, it increases like c. However, when the frictional force obtained from the road surface reaches the limit, the measured value F peaks at t2 and then decreases. Therefore, the control timing detecting means 3 of FIG. 2 detects t2, which is the moment when the measured value of the road surface frictional force F has reached the peak value. The determining means 4 determines that the F peak value at time t2 is near Pa on a low μ road surface (a road surface having a low maximum road surface friction coefficient), near Pb on a medium μ road surface (a road surface having a medium maximum road surface friction coefficient), and near a high μ road surface ( In the case of a road surface having a large maximum road surface friction coefficient), the road surface changes as in the vicinity of Pc. The control switching means 5 selects a pre-programmed control method or control set value for the brake pressure corresponding to the determined μ, and the ABS control means 6 comprising an actuator controls the ABS control means 6 according to the selected control method or set value. Perform control. The above corresponds to claim 1. The stress sensor of the road surface frictional force F detecting means 1 is provided on the upper and lower surfaces of the substrate disclosed in Japanese Patent Application No. 3-130840 (Japanese Patent Application Laid-Open No. 4-331336) proposed by the present applicant. The one-segment method was adopted in which two strain gauges each having four piezoresistors were crossed and attached, and this stress sensor was attached to the hole provided in the structure, and each strain gauge was assembled into a bridge circuit. The output is processed. The stress applied to the structure is transmitted to each strain gauge of the piezoresistance through the substrate of the stress sensor, and the strain gauge changes its resistance. There is regularity in the resistance change of the strain gauge depending on the direction of the stress, and a logical calculation is performed using this regularity to obtain a shear stress (road surface frictional force F) in a target direction. The calculating means 2, the control timing detecting means 3, the determining means 4, and the control switching means 5 are integrally formed as a computer.
[0007]
However, if the control is started after the road surface friction force F shows a peak, there is a mechanical control delay, so the road surface friction force is reduced by the time the control actually starts to be effective, and the wheel slip is large. turn into. Therefore, the first derivative F 'of the road surface frictional force F value is obtained by the calculating means 2, and the time t1 at which the first derivative F' shows a peak is detected by the control timing detecting means 3. Since the values of the road surface frictional force F at t1 viewed by the judging means 4 are Ya, Yb, and Yc in the cases of a, b, and c, μ of the traveling road surface is predicted from the correspondence between these values and the road surface μ. The control switching means 5 selects a control method or control set value corresponding to the predicted μ, and the ABS control means 6 comprising an actuator performs control according to the selected control method or set value. As described above, the prediction of the road surface μ is completed before the road surface friction force reaches the peak, and the corresponding control is started, so that the optimum ABS control can be performed without increasing the slip of the wheels. The above corresponds to claim 2.
[0008]
It is not possible to predict what the peak value of the first derivative F 'will be. Therefore, in order to recognize that F 'has peaked, it is necessary to keep the value of F' in the past and repeatedly compare it with the newly obtained F '. Therefore, in order to more easily find the peak position t1 of F ', the calculating means 2 obtains F "which is the second derivative of the road surface friction coefficient F, and this second derivative F" is changed from a positive value to a negative value. Is detected by the control timing detection means 3 to determine t1 and make a μ determination. (Corresponding to claim 3) In this method, it is not necessary to hold the past value of the first derivative F ′, and only the moment when the second derivative F ″ becomes zero or less is detected. Become.
[0009]
【effect】
According to the present invention, the μ of the road surface can be predicted before the start of the ABS control, so that a control method or a set value for control can be selected in advance according to the road surface μ. It is possible to obtain an optimal control effect that does not cause wheel slippage or the like from the beginning.
[Brief description of the drawings]
FIG. 1 is a behavior diagram of a road surface frictional force measurement value F, a first derivative value F ′ of F, and a second derivative value F ″ of F immediately after the start of sudden braking.
FIG. 2 is a functional system diagram according to the present invention.
[Explanation of symbols]
F Measured value of road frictional force F 'Second derivative of F F Second derivative of F a Behavior of F on low μ road b Behavior of F on medium μ road c Behavior of F on high μ road F peak value Pb on low μ road surface F peak value Pc on medium μ road surface F peak value Ya on high μ road surface F value at F ′ peak on low μ road surface Yb F value at F ′ peak on medium μ road surface F value Yc F value at the time of F 'peak on high μ road surface t0 At the time of sudden braking start t1 F' peak time t2 At F peak 1 Road surface frictional force F detection means 2 Calculation means 3 Control timing detection means 4 Judgment means 5 Control switching Means 6 ABS control means

Claims (3)

In a hole provided in the axle or in the vicinity of the axle, four strain gauges, each having two strain gauges crossed and attached to two opposing upper and lower surfaces of the substrate, are attached, and four strains constituting the stress sensor are mounted. An anti-lock brake system for a vehicle, wherein a gauge is assembled in a bridge circuit, and a preset brake pressure control method or control set value is automatically selected according to a peak value of the output of the bridge circuit. In a hole provided in the axle or in the vicinity of the axle, four strain gauges, each having two strain gauges crossed and attached to two opposing upper and lower surfaces of the substrate, are attached, and four strains constituting the stress sensor are mounted. A gauge is assembled into a bridge circuit, and a preset brake pressure control method or control set value is automatically selected in accordance with the output value of the bridge circuit at the time when the first derivative of the output of the bridge circuit reaches a peak. An anti-lock brake system for a vehicle. In a hole provided in the axle or in the vicinity of the axle, four strain gauges, each having two strain gauges crossed and attached to two opposing upper and lower surfaces of the substrate, are attached, and four strains constituting the stress sensor are mounted. A gauge is assembled in a bridge circuit, and a control method or control set value of a preset brake pressure is set in accordance with an output value of the bridge circuit at the time when a second derivative of the output of the bridge circuit changes to a negative value. An anti-lock brake system for a vehicle, which is automatically selected.

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