Part 1
Vehicle Dynamic Suspension
COMPONENT LOCATION
Continuously variable damping, known as Adaptive Dynamics, is available on Range Rover. Adaptive dynamics is an electronically controlled suspension system which continuously adjusts the damping characteristics of the suspension dampers in reaction to the current driving conditions.
Application of adaptive dynamics can be either a standard or option fit, dependant on vehicle variant.
The system is controlled by an Adaptive Damping Module (ADM). The ADM receives signals from three accelerometers, four suspension height sensors and from other vehicle systems to determine vehicle state, body and wheel motions and driver inputs. These signals are used by the ADM to continuously control the damping characteristics of each damper to the appropriate level resulting in optimum body control and vehicle ride.
DAMPERS
The adaptive dynamics dampers are monotube, nitrogen gas and oil filled units. 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. To maintain wheel travel, the rear dampers feature an additional external accumulator. This is to provide adequate rebound travel by recovering the volume through the external source. All 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) 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 signal from the ADM. When fully energized, the ADM 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.
ACCELEROMETERS
Three accelerometers are used in the adaptive dynamics system.
Accelerometers locations are as follows
- Front left A pillar area (behind front wing)
- Front right A pillar area (behind front wing)
- Right rear luggage floor
- Center front bulkhead area (below wind shield)
- Right rear luggage area (behind light unit)
- Left rear luggage area (below rear window)
The 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 modes.
Each 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 V/g ± 0.05 V/g.
HEIGHT SENSORS
The four suspension height sensors that are used in the air suspension system also supply input to 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 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 wheel control.
Height Sensor Wiring
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. The graphic below [Fig:9] describes the repetition of the output signal as the sensor is rotated through and beyond 40°
Height Sensor Voltage
Adaptive Damping Module (ADM)
The adaptive damping module (ADM) is located in the RH (right-hand) rear quarter panel.
GENERAL
The air suspension system is a four corner system which is fitted to all models.
The system is electronically controlled by an air suspension control module which controls the air supply unit, reacts to inputs from four height sensors and distributes air around the system via valve blocks.
The main air suspension system components are:
- Air suspension control module
- Air supply unit
- Four height sensors
- Three valve block assemblies
- Reservoir
- Air harness
- Two front struts incorporating air spring damper modules
- Two rear air spring modules.
- Adaptive Damping Module (ADM)
- Air Suspension Switch
The four corner air suspension system maintains the vehicle height under all operating conditions by controlling the mass of air in the air springs. The air suspension control module uses signals from the four height sensors to maintain the correct suspension height, irrespective of vehicle load. Additionally, the system allows the driver to request ride height changes to improve off-road performance or ease access or loading. The system automatically adjusts the ride height to improve the vehicle handling and dynamics when speed increases or decreases. This is achieved by operating pneumatic control valves to increase or decrease the mass of air in the air springs.
The air suspension system has three driver selectable, pre-determined ride heights and an automated high speed ride height. A driver interface indicates the selected ride height and height change movement. Additional information is also relayed to the driver via the instrument cluster message center and by audible warnings also transmitted by the instrument cluster.
Most height changes can only be made when the engine is running and the driver's and passenger doors are closed.
The air suspension can be controlled manually by the driver using a switch on the floor console to select the required height change.
Access height can be selected using a switch on the floor console or a switch on the drivers door.
The system will temporarily inhibit height adjustments when the vehicle is subject to cornering, heavy acceleration or heavy braking. The inhibit function prevents unsettling of the vehicle by increasing the effective spring rates.
Height changes are also restricted for safety reasons, when a door is opened and the vehicle is stationary for example.
The air suspension system fitted to Range Rover is controlled by the air suspension control module which is located behind the RH (right-hand) rear quarter panel. The control module monitors the height of each corner of the vehicle via four height sensors, which are mounted in-board of each road wheel. The control module also performs an 'on-board diagnostic' function to perform 'health checks' on the system. If faults are detected, codes are stored in the control module and can be retrieved using the Land Rover approved diagnostic system.
The suspension geometry changes when moving from off-road to access heights. See the following table for data:
Ride Height Tolerance Control
The air suspension control module has two ride height tolerance bands; normal tolerance and tight tolerance.
The control module considers the vehicle to be at target height if the current height is within the appropriate tolerance band. Height adjustments are not made until the vehicle height falls outside of the tolerance band for a pre-determined time. The time period is different depending on if the vehicle is moving or stationary. The tolerance bands are as follows:
- Normal ± 10 mm
- Tight ± 3 mm.
The tight tolerance band is only used if set by the Land Rover approved diagnostic system for diagnostic purposes or when the vehicle has been stationary for more than 5 minutes.
OPERATING MODES
The driver can manually select, using the air suspension switch, one of four ride states:
- ON-ROAD - this height is the normal operating height of the vehicle
- OFF-ROAD - this height is higher than the on-road height and provides improved ground clearance, approach, departure and breakover angles
- ACCESS - this height is lower than the on-road height and makes entering and exiting the vehicle easier for the occupants
- CRAWL (Locked at access) - this mode allows the vehicle to be driven at the access height at low speeds to provide increased roof clearance in low car parks etc.
HIGH SPEED - A non-selectable, automatic high speed mode is provided which lowers the vehicle height to improve vehicle handling.
NOTE:
Vehicle height changes are restricted if the air suspension control module receives a 'Door Open' signal and the speed is less than 5 mph (8 km/h).
A complete vehicle delivery mode is available but is only selectable using the Land Rover approved diagnostic system. When this mode is active most vehicle systems, in addition to the air suspension, are inhibited or restricted to a minimal functionality. In this mode the air suspension is set to the transportation mode.
If the air suspension control module senses that the vehicle has grounded and lost traction, the control module can temporarily increase and/or redistribute the volume of air supplied to the affected air spring(s) to maximize the available traction. This is known as extended mode and will be indicated to the driver by the lamps on the air suspension switch flashing.
If the air suspension control module senses that the vehicle is prevented from moving upwards or downwards during a height change or leveling correction, the control module will adopt a safe state and further height changes will be suspended.
If a fault is detected by the air suspension control module, the control module will reduce the system functionality dependent on the type and severity of the fault. The control module will also store a fault code which can be retrieved using the Land Rover approved diagnostic system. If a severe fault occurs, the control module will attempt to put the vehicle in a safe condition. A fault is relayed to the driver by the instrument cluster message center and an audible warning emitted from the instrument cluster.
If the detected fault is minor and does not affect vehicle safety, the instrument cluster message center will display the message 'SUSPENSION FAULT' and a chime will be emitted. The fault should be investigated and rectified as soon as possible.
If the detected fault is more serious, the message center will display the message 'SUSPENSION FAULT NORMAL HEIGHT ONLY' and a chime will be emitted. The fault should be investigated and rectified as soon as possible.
If a fault is detected within the DSC (dynamic stability control) the message 'SUSPENSION LOWERED FOR SAFETY' and a chime will be emitted. This is not a fault with the air suspension system. The fault should be investigated and rectified as soon as possible.
If the detected fault is more severe the message center will display the message 'SUSPENSION FAULT MAX SPEED 50KPH' and two chimes will be emitted every thirty seconds if this speed is exceeded. The message will change to 'SUSPENSION FAULT' when the vehicle speed is reduced to less than 31 mph (50 km/h). The vehicle should be driven slowly until the fault is rectified.
All information messages will be displayed for four seconds.