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New Delphi technologies supplied to Land Rover
Release Date: September 13, 2005. Three new technologies from Delphi are helping the new Range Rover Sport achieve levels of dynamic performance and comfort that are widely regarded as setting new standards for a high-performance SUV. The combination of advanced air suspension and a new compact version of Delphi’s Active Stabiliser Bar System (ASBS) has been credited with helping to provide exceptional handling combined with best-in-class ride. The new vehicle is also available with a new generation of Delphi’s Forewarn Smart Cruise Control that will help the driver maintain a driver-selected time gap behind the vehicle ahead at highway speeds.
"Land Rover wanted to define a new niche for an SUV that would combine comfort and sophistication with very high-performance. That’s an ambitious goal in a sector where the quality of competition is already very high," explains Rene Haep, Delphi’s customer director responsible for Land Rover. "There could be no compromise in the brand’s legendary off-road capability and there were other challenges, such as the need to fit 20 inch wheels without sacrificing ride quality. It was a tough challenge that required a fresh approach to several established areas of technology."
Dynamic Response system with Delphi’s new rotary actuators
Delphi’s new rotary actuators replace conventional stabiliser bars to provide an exceptionally compact roll control system that is thought to be the most powerful and most energy efficient in production today. Delphi worked closely with Land Rover’s chassis team, who integrated Delphi ASBS actuators and valve blocks at both the front and rear, making Range Rover Sport the first vehicle to be fitted with this new technology.
A traditional stabiliser bar improves vehicle stability through corners by reducing roll angle and managing the tyre to road interface. Heavy vehicles with a high centre of gravity typically require stiff, large diameter stabiliser bars but these will substantially reduce ride comfort and refinement and can also reduce traction in some conditions. Traditional stabiliser bars also restrict wheel travel, potentially compromising off-road behaviour, and can create an effect known as ‘head toss’ that can be particularly uncomfortable in vehicles where the occupants are seated high. Land Rover’s Dynamic Response system, incorporating Delphi’s ASBS technology, helps minimise all of these issues.
ASBS technology splits the conventional stabiliser bar in the middle. At the intersection of the two roll-bar sections, a computer-controlled actuator applies a variable level of torque. When the vehicle is travelling in a straight line, the system effectively de-couples the stabiliser bars from the vehicle, improving ride comfort and allowing large wheel articulation to increase off-road ability. In a corner, roll-stiffness is instantly increased by applying torque to each end of the bar.
Delphi’s triangulated link ASBS actuators have been available on the Land Rover Discovery from the 1999 model year, giving the vehicle manufacturer considerable confidence in the technology. With the independent suspension configuration required for exceptional on-road performance, however, the Range Rover Sport could not accommodate this system. Being faster and heavier, the new vehicle also required more control torque than the previous generation system could provide. It was therefore decided to take a clean sheet of paper and develop an all-new actuator technology.
The new rotary actuator system uses a carbon steel drum known as a ball screw, which has a spiral ball track on its outer face and a splined channel along its centre axis (see illustration). The balls on the outer face engage with a matching spiral track on the inside of a slightly larger drum attached to one side of the stabiliser bar. The other end of the stabiliser bar is splined and inserted into the channel through the ball screw.
When hydraulic pressure is applied to a piston at the end of the ball screw, forcing it along the splines, the spiral ball race creates a turning movement that applies torque to the bar via the splines on one side and via the outer drum on the other. By modulating the hydraulic pressure based on input from two lateral accelerometers and, primarily, a steering angle sensor, the torque applied to the roll bars can be optimised for any driving condition in 70ms to 250ms.
The new Delphi system provides 88 degrees of articulation and more than twice the torque of its closest rival, all from an exceptionally compact actuator. It is also significantly more efficient than competitor systems, with more than 90 percent of the generated hydraulic pressure creating torque. The efficiency of the system allows a proven pump to be used with a small reservoir and low-cost, easily routed hoses, and helps to make its operation extremely quiet.
"The torques involved are huge, so we paid particular attention to fatigue and other aspects of long-term durability," says Tony Horne, UK operations manager for Delphi Energy & Chassis Systems and a key member of the team working with Land Rover. "Finite Element Analysis was invaluable and we’ve spent a lot of time helping our suppliers introduce advanced processes such as laser welding, all with in-line quality control to provide high efficiency no-fault-forward production processes."
Delphi’s portfolio of ASBS technologies includes systems suitable for all classes of vehicle, including performance cars, allowing increased ride comfort alongside outstanding cornering control. The company also supplies a wide range of other chassis control technologies to other vehicle manufacturers including electronic stability systems, variable damping control systems and antilock braking systems.
Advanced Air Suspension
The blend of talents required by the suspension of a Range Rover Sport is considerable. As well as safely managing the 385 bhp and 550 Nm of the supercharged engine option it must provide the 2,572 kg vehicle with sportscar handling, limousine ride quality and world-class off-road ability.
Land Rover chose air suspension because it allows low spring rates (providing good ride quality) without compromising the ability to maintain ride height when loaded or trailering. Air suspension also allows the ride height to be increased when travelling over difficult terrain. Delphi already supplies compact air suspension modules for the new Discovery (called LR3 in the US) and the current Range Rover, so was a logical choice to as a key suspension supplier for the new Range Rover Sport.
When designing its air spring technology, Delphi chose a modular approach to allow fast adaptation to new applications. For the Range Rover Sport, the system uses high-pressure monotube gas shock absorbers to provide high damping forces and excellent high frequency control. The air springs are stiffened and a new type of single point top mounting has been developed to reduce the transmission of road noise into the vehicle body. The new gas shock absorbers have an 18mm shaft diameter, thought to be the largest in production for a passenger vehicle, and fit into the existing air sleeve without any modification.
The new air spring modules allow Delphi to meet Land Rover’s tough targets for performance, comfort, packaging and durability and, compared with conventional coil springs, also reduce vehicle weight by nearly 7kg. The units are designed to withstand the most demanding burst pressure and temperature range requirements set by any vehicle manufacturer.
Innovative design and electronic control allows all versions of the vehicle (four engine options, two suspension options and a vast number of accessory combinations) to be accommodated with just two versions of the air suspension module. As well as simplifying production and logistics for both Delphi and Land Rover, this helped significantly shorten the development time.
Fourth Generation Smart Cruise Control
The Range Rover Sport is also one of the first vehicles to be fitted with Delphi’s fourth-generation Smart Cruise Control (SCC) which helps the driver maintain a selected time gap behind the vehicle ahead. At highway speeds, if the lane ahead is clear, the system will maintain the cruising speed set by the driver. When slower traffic is detected in front of the vehicle, the system will automatically maintain a driver-selected headway (the time gap between the vehicles, adjustable between 1.0 and 2.2 seconds) using throttle control and limited braking. If the closing speed is sufficient to require manual intervention, audible and visual warnings are given.
At the heart of Delphi’s SCC is a mechanically scanning 76GHz microwave radar sensor, integrated with a yaw sensor in an easily packaged housing that in the Range Rover application is mounted behind a polymer body panel in the nose of the vehicle. A separate Electronic Control Unit processes the radar data to calculate the range (distance), rate (closing speed) and azimuth (lateral deviation) of targets up to 150m ahead and delivers appropriate control signals to the engine and brake control systems via the vehicle’s CAN bus.
Delphi’s narrow-beam radar system provides greatly improved angular accuracy and target discrimination compared with rival multi-beam fixed sensor systems. The wide angle view (up to 15 degrees) provides early warning of vehicles entering the lane ahead and superior tracking in tight curves. It also allows an automatic alignment feature to compensate for installation tolerances and for changes in sensor alignment during the vehicle's life, reducing fitting costs for the vehicle manufacturer and increasing system reliability.
The Delphi Forewarn system also includes a Forward Alert feature that the driver can set to provide audible and visual alerts if braking is required due to slower-moving vehicles ahead. Drivers can adjust system sensitivity to adapt alert levels to their preferred driving style. The system will also warn the driver if mud, snow or other material is blocking the sensor.