Description And Operation: Operation: Notes
The SUM 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 SUM applies algorithms to control the shock absorbers for the current driving conditions.
The SUM receives the following signals on the HS CAN bus from the stated system components:
- Brake Pressure - ABS module
- Brake Pressure Quality Factor - ABS module
- Brake Pressure Quality Factor - ABS module
- Centre Differential Range Actual - ECM
- Engine Speed - ECM
- Engine Speed Quality Factor - ECM
- Engine Torque Flywheel Actual - ECM
- Engine Torque Flywheel Actual Quality Factor - ECM
- Gear Position Target - TCM
- Lateral Acceleration - ABS module
- Power Mode (Ignition Signal) - CJB
- Power Mode Quality Factor - CJB
- Roll Stability Control Mode - ABS module
- Steering Wheel Angle - ABS module
- Steering Wheel Angle Speed - ABS module
- Steering Wheel Angle Status - ABS module
- Terrain Mode Requested - TCS
- Torque Converter Slip - TCM
- Vehicle Speed - ABS module
- Vehicle Speed Quality Factor - ABS module
- Front Left Wheel Speed - ABS module
- Front Left Wheel Speed Quality Factor - ABS module
- Front Right Wheel Speed - ABS module
- Front Right Wheel Speed Quality Factor - ABS module
- Rear Left Wheel Speed - ABS module
- Rear Left Wheel Speed Quality Factor - ABS module
- Rear Right Wheel Speed - ABS module
- Rear Right Wheel Speed Quality Factor - ABS module.
The SUM also outputs information on the HS CAN bus for use by other systems as follows:
- Fault Message - IC.
- Terrain Mode Change Status - transmission control switch.
- Terrain Mode - transmission control switch.
The SUM 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 CAN 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 Control - Uses CAN inputs. Predicts vehicle roll rate due to driver steering inputs 100 times a second and increases damping to reduce roll rate.
- 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.
- Bump Rebound Control - 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 Control - Uses suspension height sensor and CAN 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 SUM receives its power supply via a relay and fuse in the CJB. The relay remains energized for a period of time after the ignition is off. This allows the SUM to record and store any DTC relating to adaptive damping system faults.