Land Rover Discovery: Vehicle Dynamic Suspension - Component location

1. Rear right adaptive shock absorber
2. Rear right spring
3. Rear right height sensor
4. Rear left spring
5. Rear left adaptive shock absorber
6. Rear left height sensor
7. Suspension Control Module (SUM)
8. Front left adaptive shock absorber and spring assembly
9. Front left height sensor
10. Front right height sensor
11. Front right adaptive shock absorber and spring assembly

OVERVIEW

Some vehicles are fitted with an adaptive damping system, an electronically controlled suspension system that continuously adjusts the damping characteristics of the suspension shock absorbers in reaction to the current driving conditions.

The system is controlled by the Suspension Control Module (SUM). The SUM receives signals from 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 SUM to continuously control the damping characteristics of each damper to the appropriate level, to give the optimum body control and vehicle ride.

DESCRIPTION

Adaptive shock absorbers

1. Front adaptive shock absorber and spring assembly
2. Rear adaptive shock absorber

The adaptive damping shock absorbers are inverted monotube dampers that contain a magneto rheological fluid; the flow properties of the fluid change when it is subjected to a magnetic field. This allows the damping force to be electrically adjusted to provide the optimum compromise between vehicle control and ride comfort.

The fluid consists of suspended iron particles in a base fluid of synthetic hydrocarbon. When the fluid is not magnetized, the iron particles are dispersed randomly to give the fluid a mineral-oil-like consistency for low damping forces. When the fluid is magnetized, the iron particles align to form fibrous structures and make the fluid more viscous to increase the damping forces. The fluid can change from the mineral-oil-like consistency used for low damping through to a fibrous consistency for high-damping forces, depending on the strength of the magnetic field.

The magnetic field is produced by two coils integrated into the shock absorber piston and connected to the SUM via a fly-lead and an external electrical connector. When energized by the SUM, the coils produce magnetic fields in the fluid as it flows through passageways in the shock absorber piston from the high pressure side to the low pressure side. The coils are energized by a 30 kHz Pulse Width Modulation (PWM) signal from the SUM. The SUM continuously varies the signals to independently increase and decrease the damping of each shock absorber as required. The current is varied between 0 Amp (lowest damping force) and 5 Amp (highest damping force).

Sectioned View of Shock Absorber (front shock absorber shown)

1. Dividing piston
2. Damper piston
3. Rod
4. Seal pack
5. Bump plate
6. Electrical connector
7. Spring aid
8. Reservoir tube
9. Solenoids
10. Strut rod

Suspension Height Sensors

Four suspension height sensors are used in the adaptive damping system, two for the front suspension and two for the rear suspension. A front suspension height sensor is attached to a bracket on each side of the front subframe and connected by a sensor arm and sensor link to the related lower arm of the front suspension. A rear suspension height sensor is attached to a bracket on each side of the rear subframe and connected by a sensor arm and sensor link to the related rear transverse link 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 are single track units, except on vehicles with automatic headlamp levelling, where the right sensors are twin track units.

NOTE:

Vehicles without adaptive damping, but with automatic headlamp levelling, only have two suspension height sensors, which are single track units.

The suspension height sensors measure suspension displacement at each corner of the vehicle and output a corresponding analogue signal to the SUM. The algorithms in the SUM calculate the position, velocity and frequency content of the signals and use the results for individual wheel control.

The suspension height sensors measure suspension displacement at each corner of the vehicle and output a corresponding analogue signal to the SUM. The algorithms in the SUM 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 SUM via three wires, which supply ground, 5 Volt 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 +- 40º around its nominal position and the nominal sensitivity is 57 mV/º of shaft rotation.

Suspension Control Module

The Suspension Control Module (SUM) is installed on the left side of the luggage compartment, behind the access panel in the trim.

SYSTEM FAULT MESSAGE

If a fault is detected by the SUM, a CAN bus message is sent to the Instrument Cluster (IC), which illuminates the yellow general warning indicator and displays the message Adaptive Damping Fault. Since the SUM is connected to the high speed CAN Chassis bus, and the IC is connected to the high speed CAN Powertrain bus, the message is transmitted through the Gateway Module (GWM). The SUM also logs an appropriate Diagnostic Trouble Code (DTC ). The SUM can be interrogated using a Land Rover approved diagnostic system.

If a fault is detected, the SUM implements a strategy based on the type of fault. If there is an electrical power fault, or the SUM cannot control the shock absorbers, they default to the soft damping condition. If a sensor fails that only affects one or more control modes an intermediate shock absorber setting is used as the lower threshold. The remaining working modes can demand higher damping as required.

Vehicle Dynamic SuspensionVehicle Dynamic Suspension - Operation

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