Patent Application
20070267916
The ESC controller 110 of the ESC electronic control system 108 compares the vehicle sensor outputs and calculated parameters to predetermined parameter values obtained empirically or through simulation for a particular vehicle model to determine, in conjunction with vehicle systems such as, but not limited to, ESC, ABS, and traction control, whether vehicle chassis control activity is occurring, as for example a situation in which the operation of the vehicle is unstable. If vehicle chassis control chassis activity is occurring, brake controller 116 is notified via line 118 and selective rear brake controller 112 is notified via line 114.
Otherwise, if vehicle chassis control chassis activity is not occurring, selective rear brake controller 112 is notified via line 114. Selective rear brake controller 112 utilizes vehicle sensor outputs and calculated parameters available from the vehicle microprocessor or ESC system such as, but not limited to, vehicle speed, wheel speeds, steering wheel angle, steering hydraulic assist pressure, wheel slip, yaw velocity, lateral acceleration, gear position, throttle position, master cylinder brake pressure, wheel brake pressure, brake pedal position, and rate of change of wheel brake pressure. The selective rear brake controller 112 utilizes the aforementioned vehicle sensor outputs and calculated parameters in conjunction with predetermined parameter values obtained empirically or through simulation for a particular vehicle model to determine, in conjunction with vehicle systems such as, but not limited to, ESC, ABS, and traction control, whether appropriate vehicle operating conditions exist to actuate the present invention. If appropriate vehicle operating conditions do exist to actuate the present invention, then selective rear brake controller 112 determines appropriate rear brake parameters and selects the appropriate rear brake (the wheel at the inside of the turn) to activate (the rear right brake 122 of the rear right wheel 130 in the example of
Brake controller 116 directs ESC hydraulic brake control unit 124 via line 126 to activate the appropriate rear brake (the rear right brake 122 in the example of
During and after activation of the appropriate rear brake (128 in
The algorithm is initiated at Block 202 and proceeds to Block 204. If the engine is running at Block 204, control passes to Block 206. If the brake pedal induced master brake cylinder pressure at Block 206 is less than NPBRKENABLEPRESS, control passes to Block 208. If there is no chassis control activity, as determined by, for example, the ESC, ABS, or traction control systems, control passes to Block 210. In the case where the engine is not running at Block 204 or the brake pedal induced master brake cylinder pressure at Block 206 is greater than NPBRKENABLEPRESS or a chassis control activity at Block 208 is occurring wherein an electronic control (i.e., ESC, ABS, or traction control systems) of the motor vehicle is sensing a tracking instability for which the electronic control provides a pre-programmed stability control response, control is passed to Block 212. At Block 212, the inside rear brake is released at QNPPRESSURERAMP-DOWNRATE and control then passes to Block 204.
At Block 210, if the time in a forward or reverse gear is greater than NPMINGEARTIME, control passes to Block 214. At Block 214, if the steering wheel position is greater than NPHWPOSITION, control passes to Block 216. At Block 216, if the vehicle speed is between NPMINSPEED and NPMAXSPEED, control passes to Block 218. At Block 218, if the throttle position is between NPMINTHROT and NPMAXTHROT, control passes to Block 220.
However, if at Block 210 the time in a forward or reverse gear is less than NPMINGEARTIME or at Block 214 the steering wheel position is less than NPHWPOSITION or at Block 216 the vehicle speed is not between NPMINSPEED and NPMAXSPEED or at Block 218 the throttle position is not between NPMINTHROT and NPMAXTHROT, control passes to Block 222. At Block 222, the inside rear brake is released at NPPRESSURE-RAMPDOWNRATE and control then passes to Block 204.
At Block 220, the appropriate rear wheel to brake, the inside rear wheel of the turn, is selected using, for example, steering wheel angle position, and control passes to Block 223.
At Block 223, if the wheel slip of the selected rear wheel to brake is greater than NPMAXSLIP, then control passes to Block 222 whereat the inside rear brake is released at NPPRESSURE-RAMPDOWNRATE and control then passes to Block 204; if not, control passes to Block 224. In this regard, “wheel slip” of a wheel during vehicle movement ranges between 100 percent when the wheel is locked (nonrotating) and zero percent when the wheel is freely rotating, and is defined by the expression: (wheel free rotation speed minus actual wheel rotation speed) divided by wheel free rotation speed.
At Block 224, if the wheel slip of the selected rear wheel to brake is not between NPMINSLIP and NPMAXSLIP, then control passes to Block 226.
At Block 226, if the estimated brake pressure is less than NPMAXPRESS, control passes to Block 228. At Block 228, the brake of the selected rear wheel is applied at NPPRESSURERAMPUPRATE. The estimated brake pressure and wheel slip of the selected rear wheel to brake are calculated by the ESC control system. The ESC control system uses the master brake cylinder pressure sensor, valve control information, and wheel speed sensors to continuously estimate these parameters.
At Block 224, if the wheel slip of the selected rear wheel to brake is between NPMINSLIP and NPMAXSLIP, control passes to Block 230 whereat the brake pressure of the selected rear wheel to brake is held at its present level and control then passes to Block 204. At Block 226, if the estimated brake pressure is greater than NPMAXPRESS, control passes to Block 232 whereat the brake pressure of the selected rear wheel to brake is held at NPMAXPRESS and control then passes to Block 204.
To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.
