Description
Vehicle Dynamic Suspension
NOTE:
A = Hardwired; D = High speed CAN (controller area network) bus.
PRINCIPLES OF OPERATION
The ADM uses a combination of information from other system modules and data from the body vertical accelerometers and suspension height sensors to measure the vehicle and suspension states and driver inputs. Using this information, the ADM applies algorithms to control the dampers for the current driving conditions.
The ADM receives the following signals on the high speed CAN (controller area network) bus from the stated system components:
- Brake pressure - ABS (anti-lock brake system) module.
- Brake pressure quality factor - ABS (anti-lock brake system) module.
- Car configuration parameters - CJB (central junction box).
- 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 - CJB (central 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 - ABS (anti-lock brake system) module.
- Rear right wheel speed quality factor - ABS (anti-lock brake system) module.
The ADM 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.
- Front left suspension height - other systems as required.
- Front right suspension height - other systems as required.
- Rear left suspension height - other systems as required.
- Rear right suspension height - other systems as required.
The ADM monitors the input signals and operates the damper solenoids. The input signals are used in control functions and a force required for each damper, for each function, is calculated. An arbitrator monitors the force requirements from each function and apportions a force to a damper. The force is converted to the appropriate current and sent to the damper.
The control functions are as follows:
- Body Control - Uses body vertical accelerometer and CAN (controller area network) 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 attitude. Provides improved body control without loss of ride quality.
- 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. Provides improved control and driver confidence.
- 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. Provides improved control and driver confidence.
- 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. Provides improved ride quality.
- 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. Provides improved ride quality.
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 ADM 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 ADM 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, which are integrated with a conventional coil spring (front suspension) or an air spring (rear suspension) to form the spring and damper assemblies. The dampers are continuously variable, which allows the damping force to be electrically adjusted when the vehicle is being driven. The 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.
In each damper, the 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) valve. 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 separate 526 Hz PWM (pulse width modulation) signal from the ADM. The ADM continuously varies the current of the PWM (pulse width modulation) signals between a minimum of 0 A and a maximum of 1.5 A (i.e. between the maximum firm setting when de-energized and the maximum soft setting when fully energized) to independently increase and decrease the damping of each damper as required.
Sectioned Views of Damper Operating States
BODY VERTICAL ACCELEROMETERS
Three body vertical accelerometers are used in the adaptive dynamics system:
- A front body vertical accelerometer is attached to the body behind the right front wheel, on the front sidemember to dash gusset.
- A rear body vertical accelerometer is installed on each side of the luggage compartment, attached to the related rear quarter panel.
The body vertical accelerometers measure acceleration in the vertical plane and output a corresponding analogue signal to the ADM. The algorithms in the ADM calculate the heave, pitch and roll motions of the vehicle, which are used by the controller to control road induced body motion.
Each body vertical accelerometer is connected to the ADM 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 ± 0.05 v/g.
SUSPENSION HEIGHT SENSORS
NOTE:
Rear sensor shown, front sensors similar.
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 subframe 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.
Each suspension height sensor contains two independent sensors:
- Sensor 1 is used by the air suspension system. For additional information, refer to Rear Suspension Rear Suspension
- Sensor 2 is used by the adaptive dynamics system.
The suspension height sensors measure suspension displacement at each corner of the vehicle and output a corresponding analogue signal to the ADM. The algorithms in the ADM calculate the position, velocity and frequency content of the signals and use the results for individual wheel control.
Each suspension height sensor is connected to the ADM via three wires, which supply ground, 5 V supply and signal return.
Each 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 attached magnet. The signals from each of 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 ADM is installed on the right side of the luggage compartment, in a bracket attached to the rear quarter panel.
System Fault Message
If a fault is detected by the ADM, a message is sent via the high speed CAN (controller area network) to the instrument cluster and the message ADAPTIVE DYNAMICS FAULT is displayed. The ADM also logs an appropriate DTC (diagnostic trouble code). The ADM can be interrogated using a Jaguar approved diagnostic system.
If a fault is detected, the ADM implements a strategy based on the type of fault. If there is an electrical power fault, or the ADM cannot control the dampers, they default to the firm condition. If a sensor fails that only affects one or more control modes an intermediate damper setting is used as the lower threshold. The remaining working modes can demand higher damping as required.