Vehicle Dynamic Suspension (G2181021): Operation

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

The CHCM receives the following signals on the High Speed (HS) Controller Area Network (CAN) chassis systems bus from the stated system components:

• Brake pressure - Anti-lock Brake System (ABS) control module.
• Brake pressure quality factor - ABS control module.
• Car configuration parameters - Body Control Module/Gateway Module (BCM/GWM).
• Engine speed - Powertrain Control Module (PCM).
• Engine speed quality factor - PCM.
• Engine torque flywheel actual - PCM.
• Engine torque flywheel actual quality factor - PCM.
• Gear position target - Transmission Control Module (TCM) - automatic transmission vehicles only.
• Lateral acceleration - ABS control module.
• Power mode (ignition signal) - BCM/GWM.
• Power mode quality factor - BCM/GWM.
• Roll stability control mode - ABS control module.
• Steering wheel angle - ABS control module.
• Steering wheel angle speed - ABS control module.
• Steering wheel angle status - ABS control module.
• Terrain mode requested - JaguarDrive Switchpack (JDS).
• Torque converter slip - TCM - automatic transmission vehicles only.
• Vehicle information parameters HS - BCM/GWM.
• Vehicle speed - ABS control module.
• Vehicle speed quality factor - ABS control module.
• Front left wheel speed - ABS control module.
• Front left wheel speed quality factor - ABS control module.
• Front right wheel speed - ABS control module.
• Front right wheel speed quality factor - ABS control module.
• Rear left wheel speed - ABS control module.
• Rear left wheel speed quality factor - ABS control module.
• Rear right wheel speed - ABS control module.
• Rear right wheel speed quality factor - ABS control module.

The CHCM also outputs information on the HS CAN  chassis systems bus for use by other systems as follows:

• Fault message - Instrument Cluster (IC).
• Terrain mode change status - JaguarDrive Switchpack (JDS).
• Terrain mode - JaguarDrive Switchpack (JDS).

The CHCM monitors the input signals and operates the shock absorber solenoids. The input signals are used in control functions and a force required for each 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 shock absorber.

The control functions are as follows:

• Body Control - Uses suspension height sensors and CAN  bus inputs. Calculates road induced body motions 200 times a second and sets each shock absorber to the appropriate level to maintain a flat and level body attitude. Provides improved body control without loss of ride quality.
• Roll Rate Control - Uses CAN  inputs. Predicts vehicle roll rate due to driver steering inputs 100 times a second and increases damping to reduce roll rate. Provides improved control and driver confidence.
• Pitch Rate Control - Uses CAN  inputs. Predicts vehicle pitch rate due to driver throttle and braking inputs 100 times a second and increases damping to reduce pitch rate. Provides improved control and driver confidence.
• Bump Rebound Control - Uses suspension height sensor and CAN  inputs. Monitors the position of the wheel 1, 000 times a second and increases the damping rate as the shock absorber approaches the end of its travel. Provides improved ride quality.
• Wheel Control - Uses suspension height sensor and CAN  inputs. Monitors the position of the wheel 1, 000 times a second and provides the appropriate level of damping for the suspension velocity.
• Dynamic program - Uses suspension height sensor and CAN  inputs. The Dynamic program uses a completely separate tune from the normal control, an alternative set-up for the body, wheel, roll rate, pitch rate and bump/rebound control to give a tighter, sportier driving feel.
• Off road modification - Uses suspension height sensors and CAN  inputs. Evaluates the road surface roughness and appropriately adapts the level of damping control demanded from the various functions: body, wheel, roll rate, pitch rate and bump/rebound control.

Under normal road conditions, when the vehicle is stationary with the engine running, the dampers are set to the lowest damping condition to reduce power consumption.

The CHCM has a constant power supply, and an ignition power feed from the Rear Junction Box (RJB). The ignition power feed relay is energized by the BCM/GWM. The relay 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.