Method of controlling anti-lock brake system for vehicles and method of finding control point in ABS

Abstract

In an anti-lock brake system mounted on a vehicle wherein when the vehicle is braked in an emergency during running, an increase in the road surface friction force or road surface friction coefficient owing to an increase in the brake pressure is detected by a road surface friction force detecting device or road surface friction coefficient detecting device. The optimum control start point associated with an increase in the signal value of the road surface friction force F or road surface friction coefficient μ provided by the road surface friction force detecting device or road surface friction coefficient detecting device is decided by using a decrease in the wheel speed, i.e., by using the wheel speed ω or dω/dt. Thereafter, from the point where the specified value of control based on F or μ, or dF/dt or dμ/dt, the brake pressure is moved from the pressure increasing mode to the pressure retaining or decreasing mode.

What is claimed is:  
     
         1 . A method of controlling an anti-lock brake system for vehicles wherein when a vehicle having an anti-lock brake system mounted thereon has emergency brake applied thereto, a change in road surface friction force or road surface friction coefficient due to the increased brake pressure is detected by a road surface friction force detecting device or a road surface friction coefficient detecting device, 
 said method being characterized in that to decide the optimum control start point concomitant with the increase of the signal value of road surface friction force F or road surface friction coefficient μ detected by the road surface friction force detecting device or road surface friction coefficient detecting device, use is made of means for eliminating disturbance sources which impede such decision.    
     
     
         2 . A method of controlling an anti-lock brake system for vehicles, wherein when a vehicle having an anti-lock brake system mounted thereon has emergency brake applied thereto, a change in road surface friction force or road surface friction coefficient due to the increased brake pressure is detected by a road surface friction force detecting device or a road surface friction coefficient detecting device, 
 said method being characterized in that the optimum control start point concomitant with the increase of the signal value of road surface friction force F or road surface friction coefficient μ due to the increased brake pressure detected by the road surface friction force detecting device or road surface friction coefficient detecting device is decided by a drop in the wheel speed, that is, by using the wheel speed ω or dω/dt, and then from the point where the specified value of control by F or μ or by dF/dt or dμ/dt is reached, the brake pressure is shifted from the pressure increasing mode to the pressure retaining or decreasing mode, so as to eliminate disturbance sources.    
     
     
         3 . A method of controlling an anti-lock brake system for vehicles wherein when a vehicle having an anti-lock brake system mounted thereon has emergency brake applied thereto, a change in road surface friction force or road surface friction coefficient due to the increased brake pressure is detected by a road surface friction force detecting device or a road surface friction coefficient detecting device, 
 said method being characterized in that the optimum control start point concomitant with the increase of the signal value of road surface friction force F or road surface friction coefficient μ due to the increased brake pressure detected by the road surface friction force detecting device or road surface friction coefficient detecting device is decided by a drop in the vehicle acceleration decided by dV/dt using an acceleration sensor, and then from the point where the specified value of control by F or μ or by dF/dt or dμ/dt is reached, the brake pressure is shifted from the pressure increasing mode to the pressure retaining or decreasing mode, so as to eliminate disturbance sources.    
     
     
         4 . A method of controlling an anti-lock brake system for vehicles wherein when a vehicle having an anti-lock brake system mounted thereon has emergency brake applied thereto, a change in road surface friction force or road surface friction coefficient due to the increased brake pressure is detected by a road surface friction force detecting device or a road surface friction coefficient detecting device, 
 said method being characterized in that the optimum control start point concomitant with the increase of the signal value of road surface friction force F or road surface friction coefficient μ detected by the road surface friction force detecting device or road surface friction coefficient detecting device is decided by both the wheel speed ω or dω/dt and dV/dt, and then from the point where the specified value of control by F or μ or by dF/dt or dμ/dt is reached, the brake pressure is shifted from the pressure increasing mode to the pressure retaining or decreasing mode, so as to eliminate disturbance sources.    
     
     
         5 . A method of controlling an anti-lock brake system for vehicles as set forth in claims  1  through  4 , characterized in that in the pressure decreasing mode subsequent to the retaining mode or after moving to the pressure decreasing mode, the brake pressure is shifted from the pressure decreasing mode to the pressure increasing mode by a pressure decreasing threshold value, a set value of a specified value of elapsed time or a decision circuit or by a combination of two or more of such factors, so as to eliminate disturbance sources.  
     
     
         6 . A method of controlling an anti-lock brake system for vehicles, characterized in that during travel of a vehicle having an anti-lock brake system, the first brake pressure control is effected by using any of the control methods described in claims  1  through  4 , and then at the point of time when the control method described in    claim 5    is completed, the control is continuously repetitively effected by using any of the control methods described in claims  1  through  4  or the control method described in    claim 5    until the vehicle stops or in and after the second time the control is continuously repetitively effected by using F or μ, or dF/dt or dμ/dt alone and the control method described in    claim 5    until the vehicle stops, thus eliminating disturbance sources.  
     
     
         7 . A method of controlling an anti-lock brake system for vehicles wherein when a vehicle having an anti-lock brake system mounted thereon has emergency brake applied thereto, a change in road surface friction force or road surface friction coefficient due to the increased brake pressure is detected by a road surface friction force detecting device or a road surface friction coefficient detecting device, 
 said method being characterized in that after the maximum value of the signal value of road surface friction force F or road surface friction coefficient μ detected by the road surface friction detecting device or road surface friction coefficient detecting device has been ascertained, fixed lower limits are provided for the approximate maximum F value or approximate maximum μ value and the maximum F value or maximum μ value and the brake pressure is controlled such that F or μ is stably retained in the range, thus eliminating disturbance sources.    
     
     
         8 . A method of controlling an anti-lock brake system for vehicles wherein when a vehicle having an anti-lock brake system mounted thereon has emergency brake applied thereto, a change in road surface friction force or road surface friction coefficient due to the increased brake pressure is detected by a road surface friction force detecting device or a road surface friction coefficient detecting device, 
 said method being characterized in that after the maximum value of the signal value of road surface friction force F or road surface friction coefficient μ detected by the road surface friction detecting device or road surface friction coefficient detecting device has been ascertained, fixed lower limits are provided for the approximate maximum F value or approximate maximum μ value and the maximum F value or maximum μ value and the brake pressure is controlled by being increased or decreased in the range in which F or μ is retained, thus eliminating disturbance sources.    
     
     
         9 . A method of controlling an anti-lock brake system for vehicles, characterized In that in claims  7  and  8 , variations in F or μ with respect to brake pressure are monitored and when the upper limit of brake pressure in a preset control range is reached, if F or μ exceeds the previous maximum F or maximum μ, the brake pressure is further increased to ascertain the maximum μ again, whereafter the above-mentioned brake pressure control is effected, thus eliminating disturbance sources.  
     
     
         10 . A method of controlling an anti-lock brake system for vehicles, characterized in that in claims  7  and  8 , variations in F or μ with respect to brake pressure are monitored and if the F value or μ value decreases with respect to the brake pressure in a preset brake pressure control range, the brake pressure is rapidly decreased to ascertain the maximum μ again, thus effecting control to eliminate disturbance sources.  
     
     
         11 . A method of controlling an anti-lock brake system for vehicles, characterized in that in the case where the maximum value of the signal value of road surface friction force F or road surface friction coefficient μ detected by the road surface friction force detecting device or road surface friction coefficient detecting device can hardly be ascertained, quasi-F or quasi-μ is found between the maximum F value or maximum μ value and the minimum F value or minimum μ value within a given period of time, and the brake pressure control is effected corresponding to such quasi-F or quasi-μ, thus eliminating disturbance sources.  
     
     
         12 . A method of controlling an anti-lock brake system for vehicles, characterized in that in    claim 11   , in the case where the value between the maximum F value or maximum μ value and the minimum F value or minimum μ value within a given period of time varies beyond the allowable range, the individual values are measured again within a given period of time to newly find quasi-F or quasi-μ and the brake pressure control is effected corresponding to such quasi-F or quasi-μ, thus eliminating disturbance sources.  
     
     
         13 . A method of controlling an anti-lock brake system for vehicles, characterized in that in claims  11  and  12 , in the case where the maximum μ can be ascertained, control is effected according to the control methods described in claims  7  through  10 , thus eliminating disturbance sources.  
     
     
         14 . A method of detecting the control point in an ABS having a stress sensor which provides an output proportional to the road surface friction F or road surface friction coefficient μ having mixed therein a crosstalk component, such as brake torque T, and to the brake torque T, said method being characterized in that it uses adjusting means for making adjustment from the rise of the brake start such that detected signals of F or μ and T are adjusted in ratio or made equal in value, and decision means for deciding the control point by a change in said ratio or in adjustment coefficient, wherein the timing of the control point is detected by the size of a change in the ration of detected signals of F or μ and T or in adjustment coefficient.  
     
     
         15 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or adjustment coefficient substantially stops changing is decided to be the control timing.  
     
     
         16 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, during brake pressure decreasing control, becomes substantially equal to the value obtained upon completion of the preceding brake pressure decreasing control is decided as the completion of the brake pressure decreasing control, said point of time being decided to be the optimum control timing for ABS.  
     
     
         17 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, during the brake pressure decreasing control, becomes above the value obtained during the first brake pressure decreasing control is decided to be the completion of the brake pressure decreasing control, said point of time being decided to be the optimum control timing for the ABS.  
     
     
         18 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, during the brake pressure decreasing control, starts to increase is decided to be the completion of the brake pressure decreasing control, said point of time being decided to be the optimum control timing for the ABS.  
     
     
         19 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, except during the brake pressure decreasing control, becomes just above the value obtained during the first brake pressure decreasing control is decided as the start of brake pressure decreasing control, said point of time being decided to be the optimum control timing for the ABS.  
     
     
         20 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, during the brake pressure retaining control, becomes greater than the value obtained during the first brake pressure decreasing control is decided to be the start of brake pressurization control, said point being decided to be the optimum control timing for the ABS.  
     
     
         21 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, during the brake pressure retaining control, becomes smaller than the value obtained during the first brake pressure decreasing control and becomes further smaller is decided to be the start of brake pressure decreasing control, said point being decided to be the optimum control timing for the ABS.  
     
     
         22 . A method of detecting the control point in an ABS, characterized in that in the decision means of    claim 14   , the point of time when the ratio of F or μ and T or the adjustment coefficient, during the brake pressure retaining control, becomes smaller than the value obtained during the first brake pressure decreasing control and is stabilized is decided to be continuation of brake pressure retention or the start of control of gentle increase of pressure, said point of time being decided to be the optimum control timing for the ABS.  
     
     
         23 . A method of detecting the control point in an ABS having a stress sensor which provides an output proportional to the road surface friction F or road surface friction coefficient μ having mixed therein a crosstalk component, such as brake torque T, and to the brake torque T, said method being characterized in that it uses adjusting means for adjusting the ratio of detected signals of F or μ and T, and decision means for deciding the control point by a change in F−T value from its value after adjustment, wherein the timing for the control point is detected by said change in the F−T value.  
     
     
         24 . A method of detecting the control point in an ABS having a stress sensor which provides an output proportional to the road surface friction force F or road surface friction coefficient μ and the brake torque T, said method being characterized in that the timing for the control point is detected by a change in the F−T value during brake control.  
     
     
         25 . A method of detecting the control point in an ABS, characterized in that in the decision means in claims  23  and  24 , a threshold value for the F−T value is provided to decide the control point in control.  
     
     
         26 . A method of detecting the control point in an ABS, characterized in that in the threshold value of    claim 25   , a change in the F−T threshold value is corrected as the road surface friction coefficient changes, thereby detecting the timing for the control point.