PIN AS 1043465 - Caterpillar

Brake Pedal Modulation
The software uses the stored calibration value to create a brake pedal modulation map. When the brake pedal is depressed beyond the pedal sensor deadband range, the brake pressure will drop from high fully retracted pressure to a pressure just above the calibrated touch-up pressure. The pressure above touch-up calibration pressure will be approximately 138 kPa (20 psi) for the D8T and D9T, and approximately 34 kPa (5 psi) for the D10T tractors. This pressure increase is a result of a fixed offset programmed into the software. The offset was derived subjectively using operator feedback on good brake feel after a touch-up calibration.Several operators have expressed dissatisfaction with the brake modulation and have attempted to adjust the calibration value manually to improve the feel of the brakes. Often the result is poor braking. While the practice of experimenting with CAL values is acceptable, the operator should understand the cause and effect relationship between the brake calibration and the feel of the brake. To explain this relationship, divide the braking strategy into three segments: Engage, Modulate, and Fully Applied. When an operator first applies the brakes, the operator first enters the Engagement segment. During Engagement, applying the brakes smoothly and gradually from zero torque to a moderate amount of torque that could be used for fine controls such as inching is desirable. Proper brake response in the engagement range allows good inching capability and a smooth application of the brakes. During the Modulation range of operation, the operator should be able to easily modulate an infinite range of brake torques with ease using the foot pedal. During the Fully Applied range, the brake pressure continues to modulate, however the brakes are generating enough torque that fine modulation is not as important as earlier. The fully applied range ends when the secondary dump solenoid dumps off all remaining pressure near the end of pedal travel.
Illustration 1 g01377923
Illustration 1 is an example of brake application on the D9T.
The CAL value establishes the starting point for brake modulation, and therefore also sets the slope of the brake pedal/brake pressure relationship. Setting the CAL value too low will result in a harsh initial engagement of the brakes, but also a good modulation of the brakes after the brakes are engaged. Setting the CAL value too high will result in soft (spongy) application of the brakes during the first part of the pedal engagement, but will also result in poor modulation (grabby) braking after the brakes are engaged. The calibration value established using the calibration procedure is intended to result in the optimal brake map, responsive during initial engagement and good modulation after engagement. If the brake application is unacceptable to the operator, first follow the calibration procedure. If the procedure does not yield acceptable results, assess whether the complaints occur at the beginning of brake application or later in the modulation. If the brakes are too harsh for the operator during initial pedal movement, try increasing the CAL value and decreasing for