Description
Vehicle Dynamic Suspension
NOTE:
A = Hardwired; D = High speed CAN (controller area network) bus
PRINCIPLES OF OPERATION
The adaptive damping module 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 adaptive damping module applies algorithms to control the dampers for the current driving conditions.
The adaptive damping module receives signals on the high speed CAN (controller area network) bus from the following system components:
- Brake Pressure - ABS (anti-lock brake system) module.
- Brake Pressure Quality Factor - ABS (anti-lock brake system) module.
- Car Configuration Parameters - AJB (auxiliary junction box).
- Center Differential Range Actual - ECM (engine control module).
- Engine Speed - ECM (engine control module).
- Engine Speed Quality Factor - ECM (engine control module).
- Engine Torque Flywheel Actual - ECM (engine control module).
- Engine Torque Flywheel Actual Quality Factor - ECM (engine control module).
- Gear Position Target - TCM (transmission control module).
- Lateral Acceleration - ABS (anti-lock brake system) module.
- Power Mode (Ignition Signal) - CJB (central junction box).
- Power Mode Quality Factor - CJB (central junction box).
- Roll Stability Control Mode - ABS (anti-lock brake system) module.
- Steering Wheel Angle - ABS (anti-lock brake system) module.
- Steering Wheel Angle Speed - ABS (anti-lock brake system) module.
- Steering Wheel Angle Status - ABS (anti-lock brake system) module.
- Terrain Mode Requested - JaguarDrive selector.
- Torque Converter Slip - TCM (transmission control module).
- Vehicle Information Parameters HS - AJB (auxiliary junction box)
- Vehicle Speed - ABS (anti-lock brake system) module.
- Vehicle Speed Quality Factor - ABS (anti-lock brake system) module.
- Front Left Wheel Speed - ABS (anti-lock brake system) module.
- Front Left Wheel Speed Quality Factor - ABS (anti-lock brake system) module.
- Front Right Wheel Speed - ABS (anti-lock brake system) module.
- Front Right Wheel Speed Quality Factor - ABS (anti-lock brake system) module.
- Rear Left Wheel Speed - ABS (anti-lock brake system) module.
- Rear Left Wheel Speed Quality Factor - ABS (anti-lock brake system) module.
- Rear Right Wheel Speed Quality Factor - ABS (anti-lock brake system) module.
- Rear Right Wheel Speed - ABS (anti-lock brake system) module.
The adaptive damping module also outputs information on the high speed CAN (controller area network) bus for use by other systems as follows:
- Fault Message - instrument cluster.
- Terrain Mode Change Status - JaguarDrive selector.
- Terrain Mode - JaguarDrive selector.
The adaptive damping module monitors the input signals and operates the damper solenoids. The input signals are used in control modes and a force required for each damper for that mode is calculated. An arbitration mode monitors the force requirements from each mode and apportions a force to a damper. The force is converted to the appropriate current and sent to the damper.
The control modes are as follows:
- Body Control - Uses CAN (controller area network) and accelerometer inputs. Calculates road induced body motions 100 times a second and sets each damper to the appropriate level to maintain a flat and level body.
- Roll Rate Control - Uses CAN (controller area network) 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 (controller area network) 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 and CAN (controller area network) inputs. Monitors the position of the wheel 500 times a second and increases the damping rate as the damper approaches the end of its travel.
- Wheel Hop Control - Uses suspension height sensor and CAN (controller area network) inputs. Monitors the position of the wheel 500 times a second and detects when the wheel is 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 dampers are set to the firm condition to reduce power consumption.
The adaptive damping module receives its power supply via a relay and fuse 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 DTC (diagnostic trouble code) relating to adaptive dynamics system faults.
DAMPERS
The 'Adaptive Dynamics' dampers are monotube, nitrogen gas and oil filled units, manufactured by Bilstein. The dampers are continuously variable, which allows the damping force to be electrically adjusted when the vehicle is being driven. The variable dampers provide the optimum compromise between vehicle control and ride comfort.
The dampers have an electrical connector on the end of the piston rod, in the center of the top mount (the dampers look identical to those on the Computer Active Technology Suspension (CATS) system of 4.2L supercharged vehicles, but have a different part number).
In each damper, the continuous damping adjustment is achieved by a solenoid operated variable orifice, which opens up an alternative path for oil flow within the damper. When de-energized the bypass is closed and all the oil flows through the main (firm) piston. When energized, the solenoid moves an armature and control blade, which work against a spring. The control blade incorporates an orifice which slides inside a sintered housing to open up the bypass as required. In compression, oil flows from the lower portion of the damper through a hollow piston rod, a separate soft (comfort) valve, the slider housing and orifice and into the upper portion of the damper, thereby bypassing the main (firm) valve. In rebound the oil flows in the opposite direction.
In the firm setting, oil flows through the main (firm) valve only, but when the bypass is opened by any amount the oil flows through both valves in a pressure balance. When fully energized the solenoid moves the armature and therefore the slider to the maximum extension and opens the orifice completely. The damper operates continuously between these two boundary conditions.
The solenoid in each damper is operated by a 526 Hz PWM (pulse width modulation) signal from the adaptive damping module. When fully energized, the adaptive damping module applies a 1.5 A current to operate the damper in the soft setting. When de-energized (0.0 A) the damper is in the firm setting. The current varies continuously as required to increase and decrease the damping individually in each of the dampers.
Sectioned Views of Damper Operating States
ACCELEROMETERS
Three accelerometers are used in the adaptive dynamics system. The accelerometers are located as follows:
- One each on the rear edge of the radiator support panel.
- One in the luggage compartment, in the rear LH (left-hand) corner adjacent to the rear lamp assembly.
The accelerometers measure acceleration in the vertical plane and output a corresponding analogue signal to the adaptive damping module. The algorithms in the adaptive damping module calculate the heave, pitch and roll motions of the vehicle, which are used by the module to control road induced body modes.
Each accelerometer is connected to the adaptive damping module via three wires, which supply ground, 5 V supply and signal return.
The sensing element comprises a single parallel plate capacitor, one plate of which moves relative to the other dependant on the force (acceleration) applied. This causes the capacitance to change as a function of applied acceleration. This capacitance is compared with a fixed reference capacitor in a bridge circuit and the signal is processed by means of a dedicated integrated circuit to generate an output voltage that varies as a function of applied acceleration. The sensors output a signal voltage of approximately 1 V/g ± 0.05 V/g.
SUSPENSION HEIGHT SENSORS
Four suspension height sensors are used in the adaptive dynamics system, two for the front suspension and two for the rear suspension. A front suspension height sensor is attached to each side of the front subframes and connected by a sensor arm and sensor link to the related lower lateral arm of the front suspension. A rear suspension height sensor is attached to each side of the rear subframe and connected by a sensor arm and sensor link to the related upper control arm of the rear suspension. On each suspension height sensor, the sensor arm and sensor link convert linear movement of the suspension into rotary movement of the sensor shaft.
The sensors are also used for the static dynamic headlamp leveling system on vehicles fitted with xenon headlamps.
The suspension height sensors measure suspension displacement at each corner of the vehicle and output a corresponding analogue signal to the adaptive damping module. The algorithms in the adaptive damping module calculate the position, velocity and frequency content of the signals and use the results for wheel control.
Each suspension height sensor is connected to the adaptive damping module via three wires, which supply ground, 5 V supply and signal return.
The sensing element consists of an array of Hall effect devices arranged to measure the direction of the magnetic field of a small magnet attached to the end of the sensor shaft. As the sensor shaft rotates, so do the lines of magnetic flux from the magnet. The signals from the Hall effect elements are processed by means of a dedicated integrated circuit to generate an output voltage that varies as the sensor shaft is rotated. The sensor has a measurement range of ± 40° around its nominal position and the nominal sensitivity is 57 mV/° of shaft rotation.
ADAPTIVE DAMPING MODULE
The adaptive damping module is installed on the floor pan, below the RH (right-hand) front seat.
System Fault Message
The adaptive damping module has a high speed CAN (controller area network) connection to the instrument cluster. If a fault is detected by the adaptive damping module, a message is sent to the instrument cluster and the message 'ADAPTIVE DYNAMICS FAULT' is displayed. The adaptive damping module also logs an appropriate DTC (diagnostic trouble code). The adaptive damping module can be interrogated using an approved Jaguar diagnostic system.
When a fault is detected, the adaptive damping module implements a strategy based on the type of fault. If there is an electrical power fault, or the adaptive damping module cannot control the dampers, they default to the firm condition. If a sensor fails that only affects one or more control modes then an intermediate damper setting is used as the lower threshold and the remaining working modes can demand higher damping as required.