Chassis Control Module

The Chassis Control Module (CHCM) receives the power supply via a relay and a fuse in the Rear Junction Box (RJB). The relay remains energized for a period of time after the ignition is switched OFF (Power Mode 4). This allows the CHCM to record and store any Diagnostic Trouble Code (DTC) relating to Adaptive Damping (AD) system faults.

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

Under normal road conditions when the vehicle is stationary and the engine is running (Power Mode 7), the adaptive shock absorbers are set to the lowest damping condition.

The CHCM uses the data from the accelerometers and the height sensors to measure the vehicle and suspension states. The CHCM also uses a combination of information from other system modules to detect driver inputs.

The main input signal for the CHCM is the steering wheel angle signal. This signal is used to predict vehicle behavior and in many of the control functions listed below. The steering angle sensor located in the Steering Wheel Module (SWM), which sends the signal input to the CHCM on the HS CAN chassis systems bus.

The steering angle offset calibration must be updated, if the SWM is replaced or reinstalled. The calibration must be done using the Jaguar Land Rover (JLR) approved diagnostic equipment.

Using this information, the CHCM applies algorithms to control the adaptive shock absorbers for the current driving conditions.

The CHCM uses the following control algorithms for the AD system control:

• Body control - The CHCM uses HS CAN chassis systems bus and height sensor inputs. The CHCM calculates the road induced body motions 200 times a second. The CHCM sets each adaptive shock absorber to the appropriate level to maintain a flat and level body attitude. This provides improved body control without loss of the ride quality.
• Roll rate control - The CHCM uses HS CAN chassis systems bus inputs. The CHCM predicts the vehicle roll rate due to driver steering inputs 200 times a second. The CHCM increases the damping force to reduce the roll rate. This provides improved control and driver confidence.
• Pitch rate control - The CHCM uses HS CAN chassis systems bus inputs. The CHCM predicts the vehicle pitch rate due to driver throttle and braking inputs 200 times a second. The CHCM increases the damping force to reduce the pitch rate. This provides improved control and driver confidence.
• Bump rebound control - The CHCM uses HS CAN chassis systems bus and height sensor inputs. The CHCM monitors the suspension displacement at each corner of the vehicle 500 times a second. The CHCM increases the damping rate as the adaptive shock absorber approaches the end of its travel. This provides improved ride quality.
• Wheel control - The CHCM uses HS CAN chassis systems bus, height sensor and accelerometer inputs. The CHCM monitors the suspension displacement at each corner of the vehicle 500 times a second. This provides the appropriate level of the damping force for the suspension velocity.
• Dynamic program - The CHCM uses HS CAN chassis systems bus inputs. The dynamic program uses an alternative calibration for the control algorithms listed above, to give a tighter, sportier driving feel.
• Off road modification - The CHCM uses HS CAN chassis systems bus, height sensor and accelerometer inputs. The CHCM evaluates the road surface roughness and appropriately adapts the level of the damping force demanded from the various control algorithms. For example, body and wheel control, roll and pitch rate control, and the bump rebound control.

The CHCM uses the input signals to calculate the damping force necessary at each adaptive shock absorber. The CHCM also calculates the adaptive shock absorber velocity and the required valve current to deliver the target damping force. Then the CHCM outputs the appropriate current to each adaptive shock absorber.