Press Release
Page 1: Overview
Page 2: Powertrain
Page 3: Dynamics
Page 4: Safety
Page 5: Comfort
Dynamics
The Lexus Ls 600h features an all-wheel drive transmission, relying on a 3-differential configuration and a propeller shaft, coupled directly to the hybrid transmission. a permanently engaged mechanical transfer system distributes drive power with a ratio of 40% to the front wheels and 60% to the rear. a centre limited-slip differential optimises grip, traction and vehicle handling on all-road conditions. Nevertheless, the aWD system has been developed to deliver typical rear wheel drive characteristics, essential to a dynamic, premium segment sedan. Traction and grip characteristics are further enhanced by the vehicle’s advanced stability control system, Vehicle Dynamics integrated Management.
Vehicle Dynamics Integrated Management (VDIM) ThenewLs600hisequippedwiththelatestgenerationofLexus’state-of-the-art Vehicle Dynamics integrated Management (VDiM) system, to enhance traction control and vehicle stability. With comprehensive status data provided by sensors throughout the vehicle, V DiM integrates the Ls 600h’s Electronically Controlled Braking (ECB), anti-Lock Brakes (aBs), Electronic Brakeforce Distribution (EBD), Traction Control (TrC) and Vehicle stability Control (VsC) active safety systems with the adaptive Variable suspension (aVs), Electric Power steering (EPs), and Variable Gear ratio steering (VGrs)
Unique to the Lexus flagship, the Ls 600h drive-train’s Driving response and acceleration Management system (DraMs) also affords VDiM unprecedented interaction with both engine and transmission, employing engine and motor output to effect a faster, smoother and more precise response to situations involving the possibility of a loss of traction, such as mid-corner gear changes.
Whereas conventional active safety systems are only activated immediately after a limit of the vehicle’s performance envelope has been reached, VDiM progressively engages before that limit is realised. as a result, VDiM offers smoother vehicle behaviour at this threshold through less obtrusive intervention and, hence, a more pleasurable drive.
Air Suspension with Active Stabilisers, AVS and vehicle posture control The Ls 600h’s air suspension utilises new pneumatic springs operating in co-operation with an improved adaptive Variable suspension system (aVs). This features a vehicle posture control to synchronise vehicle roll and pitch when cornering, for maximum passenger comfort. The Lexus hybrid flagship further benefits from active stabilisers to reduce body roll when cornering and, hence, improve the Ls 600h’s dynamic abilities.
The active stabiliser system features an actuator centrally located on both front and rear anti-roll bars. The actuator comprises a DC brushless motor with attendant reduction gear, capable of applying torque to both left and right hand sections of the stabiliser bar. a system ECU calculates the twist torque output required based on sensor-fed steering angle and vehicle velocity information. The twist force applied to both front and rear stabiliser bars controls vehicle roll motion, reducing body roll angle to promote improved vehicle stability, superior cornering performance and improved agility through enhanced steering response.
Adaptive Variable suspension (aVs) allows the driver to fine tune the Ls 600h’s ride characteristics with a choice of three damper settings activated via a switch adjacent to the gear lever; ‘Normal’ mode, an intermediate level for everyday driving, ‘COMF’, for improved comfort on more degraded roads, and ‘sPOrT’ mode, for improved body control
and precise responses to steering input whilst cornering. in either mode, aVs automatically adjusts the performance of the suspension at all four wheels independently, monitoring data from numerous sensor locations to continuously optimise the damping force of each shock absorber through 9 incremental steps.
Selecting the aVs system’s ‘sPOrT’ mode automatically increases the difference between inner and outer shock absorber damping through corners by approximately 20% to further reduce vehicle roll. simultaneously, VGrs automatically reduces the steering gear ratio by approximately 0% whilst the Electric Power steering (EPs) simultaneously increases steering assist torque. These measures combine to minimise body roll, sharpen vehicle handling and optimise steering feel for true sports sedan driving.
A new vehicle posture control damping force control logic is incorporated within the active Variable suspension system to minimise the phase difference between body roll and pitch angles during cornering. research by Lexus engineers has revealed that a large phase difference between roll and pitch angles can cause passenger discomfort by exacerbating the perception of vehicle body roll whilst cornering.
The new control logic estimates both pitch and roll angles from the G-sensor value on the sprung mass, computing a target pitch angle from the resulting roll angle. Via the air springs, vehicle posture control applies feedback control to minimise differences between target and actual pitch angle, which, in turn, minimises the phase difference between roll and pitch angles. This phase synchronisation elicits a smooth, controlled roll whilst cornering, with a well-matched vehicle response to steering, yaw and roll, and an enhanced perception of rear tyre grip.
