Chassis Control Module

The Chassis Control Module (CHCM) uses a combination of information from other system modules and data from the accelerometers and suspension height sensors to measure the vehicle and suspension states and driver inputs. Using this information, the CHCM applies algorithms to control the adaptive shock absorbers for the current driving conditions.

The CHCM receives input signals on the High Speed (HS) Controller Area Network (CAN) chassis systems bus from various vehicle systems.

The CHCM monitors the input signals and operates the adaptive shock absorber solenoids. The input signals are used in control functions and a force required for each adaptive shock absorber, for each function, is calculated. An arbitrator monitors the force requirements from each function and apportions a force to a shock absorber. The force is converted to the appropriate current and sent to the adaptive shock absorber.

The control functions are as follows:

• Body contr. Uses HS CAN chassis systems bus and accelerometer inputs. Calculates road induced body motions 100 times a second and sets each shock absorber to the appropriate level to maintain a flat and level body.
• Roll rate contr. Uses HS CAN chassis systems bus inputs. Predicts vehicle roll rate due to driver steering inputs 100 times a second and increases damping to reduce roll rate.
• Pitch rate contr. Uses HS CAN chassis systems bus inputs. Predicts vehicle pitch rate due to driver throttle and braking inputs 100 times a second and increases damping to reduce pitch rate.
• Bump rebound contr. Uses suspension height sensor inputs. Monitors the position of the wheel 500 times a second and increases the damping rate as the shock absorber approaches the end of its travel.
• Wheel hop contr. Uses suspension height sensor and HS CAN chassis systems bus inputs. Monitors the position of the wheel 500 times a second and detects when the wheel begins to vibrate at its natural frequency and increases the damping to reduce vertical wheel motion.

Under normal road conditions when the vehicle is stationary with the engine running, the shock absorbers are set to the firm condition to reduce power consumption.

The CHCM receives a fused power supply from the Rear Junction Box (RJB). The CHCM also receives an ignition signal from the BCM/GWM. The CHCM remains energized for a period of time after the ignition is off. This allows the CHCM to record and store any Diagnostic Trouble Code (DTC) relating to adaptive damping system faults.