Power assisted braking system

A method of controlling a retarder brake system of a vehicle comprising the steps of:

• determining an operator braking input indicative of a desired vehicle deceleration, said step of determining including the step of determining a brake mode value selected from at least a first and second mode wherein said first mode corresponds to a higher desired vehicle deceleration rate for a given brake pedal treadle than said second mode;
• generating a desired retarder torque value (DT) corresponding to said desired vehicle deceleration value;
• determining a wheel speed value for each wheel of said vehicle;
• detecting a brake pedal treadle value indicative of whether an operator has depressed the vehicle brake pedal;
• generating a rear-to-front wheel slip (RFS) value indicative of rear wheel spin as a function of said wheel speed values;
• generating a retarder torque (ATR) value as a function of said RFS value;
• generating a desired retarder torque command (TC) corresponding to said retarder torque value when said brake pedal treadle value is zero;
• and
• controlling said retarder as a function of said retarder torque value to achieve said desired vehicle deceleration.

A method of controlling a driveline retarder brake system of a vehicle comprising the steps of:

• determining an operator braking input indicative of a desired vehicle deceleration;
• generating a desired retarder torque value (DT) corresponding to said desired vehicle deceleration value;
• determining a wheel speed value for each wheel of said vehicle;
• generating a front-to-rear wheel slip (FRS) value indicative of rear wheel lockup as a function of said wheel speed values;
• generating a retarder torque reduction (TR) value as a function of said FRS value;
• generating a desired retarder torque command (TC) as a function of said DT and TR values;
• and
• controlling said retarder as a function of said retarder torque command to achieve said desired vehicle deceleration.

A method of controlling a driveline retarder brake system of a vehicle comprising the steps of:

• determining a wheel speed value for each wheel of said vehicle;
• detecting a brake pedal treadle value indicative of whether an operator has depressed the vehicle brake pedal;
• generating a rear-to-front wheel slip (RFS) value indicative of rear wheel spin as a function of said wheel speed values;
• generating a retarder torque (ATR) value as a function of said RFS value;
• generating a desired retarder torque command (TC) corresponding to said ATR value when said brake pedal treadle value is zero;
• and
• controlling said retarder as a function of said retarder torque command to achieve said desired vehicle deceleration.