Description
Vehicle Dynamic Suspension
NOTE:
A = Hardwired D = High speed CAN bus
Adaptive Damping System
Adaptive Damping System
The adaptive damping module uses a combination of information from other system modules and data from the accelerometer to measure the vehicle motion and driver inputs. Using this information, the module applies algorithms to control the dampers for the existing driving conditions.
The adaptive damping module receives signals on the high speed CAN (controller area network) bus from the following system components:
- Vehicle speed - ABS (anti-lock brake system) module
- Brake switch status - ECM (engine control module)
- Brake pressure - ABS module
- Gear position - TCM (transmission control module)
- Lateral acceleration - ABS module
- Throttle pedal position - ECM
- Power mode - CJB (central junction box) via the instrument cluster gateway
- Steering wheel angle - Steering angle sensor via ABS module
- Steering wheel speed - Steering angle sensor via ABS module
- Engine speed - ECM
- Engine running status - ECM
- Car Configuration File Data - auxiliary junction box via instrument cluster gateway
- Master configuration identification - auxiliary junction box via instrument cluster gateway
- Vehicle information parameters - auxiliary junction box via instrument cluster gateway.
The adaptive damping module also outputs information for use by other systems as follows:
- Computer Active Technology Suspension (CATS) fault - instrument cluster
- Front left damper status - ECM
- Front right damper status - ECM
- Rear left damper status - ECM
- Rear right damper status - ECM.
When the vehicle is stationary with the engine running, the dampers are set to the soft setting. With the vehicle in motion the adaptive damping module monitors the input signals and operates the damper solenoids appropriately. The input signals are compared against algorithms within the adaptive damping module and preset speed thresholds. The gear position signal is also used to determine longitudinal detection and, along with the speed signal, is compared against algorithms to select the appropriate 'soft' or 'firm' damper setting.
The adaptive damping module receives its power supply via a relay in the CJB (central junction box). The relay remains energized for a period of time after the ignition is off. This allows the adaptive damping module to record and store any fault codes relating to the adaptive damping system faults.
Adaptive Damping System Fault Message
The adaptive damping has a CAN connection to the instrument cluster. If a fault is detected by the adaptive damping module, a message is sent to the instrument cluster and a message 'CATS SYSTEM FAULT' is displayed.
When this message is displayed a fault has been detected and an appropriate DTC (diagnostic trouble code) will be logged in the module. The faults can be interrogated using the recommended Jaguar Diagnostic System.
When a fault is detected, the module stops outputs to the active dampers and the dampers operate continually on their default 'hard' setting until the fault is corrected.
Adaptive Damping System
Dampers
The adaptive dampers are nitrogen-gas and oil-filled monotube units. The dampers have a two-stage adjustment which allows the damping force to be electrically adjusted when the vehicle is being driven. The two-stage dampers provide the optimum compromise between performance handling and ride comfort.
The adaptive dampers can be easily identified by an electrical connector on the end of the piston rod, in the center of the top mount.
The two-stage adjustment is achieved by a solenoid controlled valve. When the solenoid valve is de-energized, the damper is on its firm setting and oil flow is restricted to a controlled rate through orifices in the damper piston. The restricted oil flow stiffens the damper action improving the handling when braking, accelerating and cornering.
The solenoid is connected to a by-pass valve which allows additional oil flow through the damper. When the solenoid is energized, the valve is lifted from its seat, allowing oil to flow through a hollow piston rod in the center of the damper piston and out through additional orifices. The increased oil flow softens the damper action providing a more comfortable ride quality.
The solenoid is operated by a 400 Hz PWM (pulse width modulation) signal from the adaptive damping module. When energized, the module applies a 1.3 ampere push current for 75 milliseconds to move the valve and then applies a 0.5 ampere hold current to operate the damper in the 'soft' setting.
Vertical Accelerometer
Two accelerometers are used by the adaptive damping system:
- a front accelerometer attached to the bracket of the right-hand engine oil cooler,
- a rear accelerometer mounted in the luggage compartment, in the rear left-hand corner next to the rear lamp assembly.
The accelerometers measure acceleration in the vertical plane and output a corresponding analogue signal to the adaptive damping module. Each accelerometer is connected to the adaptive damping module via three wires which supply: ground, 5 volt supply and signal return.
The accelerometers are of the capacitive type. The sensing element comprises two parallel plate capacitors. The capacitors alter the peak voltage which is generated by an internal oscillator when the accelerometer is subjected to acceleration. Detection circuits within the accelerometer measure the peak voltage and pass an analogue output signal to the adaptive damping module. The accelerometers output a signal voltage of approximately 1 V/g ± 0.05 V/g.