AVS tech info
12-17-06, 09:46 AM
#1
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AVS tech info
IMO, the adaptive variable suspension is a 'must have' on the LS460. It does a WHOLE LOT MORE than just give you a button for 'normal' and 'sport'. It interacts with many other systems in the car. It will make the car more controlled AND MORE COMFORTABLE under ALL circumstances. Here's some great info I dug up (from the UK).
Air Suspension System with AVS and Vehicle Posture Control
The LS 460’s suspension utilises new pneumatic springs operating in co-operation with an improved Adaptive Variable Suspension system (AVS), which features Vehicle Posture Control to synchronise vehicle roll and pitch when cornering, for enhanced stability feel. The Lexus flagship’s new suspension system reduces body roll by a substantial 30%.
The dynamic characteristics of the new pneumatic springs have been enhanced through a 20% increase in air pressure, affording the LS 460 sharper handling and better system response to changing road conditions. A revised design features a metal cylinder that limits air bellow expansion, reducing pneumatic hysteresis and improving high frequency ride comfort. Movement of the sprung mass has been further controlled by the optimisation of the bound stopper clearance.
Adaptive Variable Suspension (AVS) allows the driver to choose the LS 460’s ride characteristics with a choice of two damper settings activated via a switch adjacent to the gear lever: ‘Normal’ mode, for a flat ride, 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, receiving data from numerous sensors to continuously optimise the damping force of each shock absorber. Data from an engine rpm sensor, wheel speed sensor, steering sensor, stop lamp sensor, front and rear vehicle height sensors, and three vertical acceleration, G-force sensors is interpreted by a control computer. This later activates the appropriate actuator within each shock absorber, continuously adjusting the damping force through nine incremental steps via a compressor located in front of the right front tyre.
Hence, in response to driving operation, vehicle body motion and road surface conditions, AVS activates the adjustable damping force shock absorbers to fulfill a wide range of specific control functions: ‘vehicle speed-sensitive control’ gradually increases the damping force as speeds rise, combining low speed comfort with high speed driveability and stability. ‘Anti-dive control’ increases front end damping force under braking to reduce front end dive. ‘Anti-squat control’ increases rear end damping force to minimise squat during acceleration. ‘Roll control’ optimises vehicle posture and stability by adjusting the damping force to both inner and outer shock absorbers through a bend. Unique to the LS 460, a new Vehicle Posture Control damping force control logic is incorporated within the Adaptive 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 adjustable dampers, feedback control is applied 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 and yaw, to which adds an enhanced perception of rear tyre grip.
In addition to Vehicle Posture Control, the AVS system’s ‘Non-linear H∞ Control’ provides independent control of all four shock absorbers to optimise damping force in response to changing road surfaces. ‘Rugged sensitive control’ reduces the degree of damping force when driving on rough roads, to effect a smooth, comfortable ride. ‘Vibration control of the unsprung mass’ increases the damping force as appropriate when resonance is detected in the unsprung mass, to minimise road surface transmitted NVH under all conditions. And ‘VDIM cooperative control’ adjusts the damping force in conjunction with the vehicle’s stability control system to maximise its efficiency.
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 10% whilst the Electric Power Steering (EPS) simultaneously increases steering assist torque by some 4%. These measures combine to minimise body roll, sharpen vehicle handling and optimise steering feel.
Air Suspension System with AVS and Vehicle Posture Control
The LS 460’s suspension utilises new pneumatic springs operating in co-operation with an improved Adaptive Variable Suspension system (AVS), which features Vehicle Posture Control to synchronise vehicle roll and pitch when cornering, for enhanced stability feel. The Lexus flagship’s new suspension system reduces body roll by a substantial 30%.
The dynamic characteristics of the new pneumatic springs have been enhanced through a 20% increase in air pressure, affording the LS 460 sharper handling and better system response to changing road conditions. A revised design features a metal cylinder that limits air bellow expansion, reducing pneumatic hysteresis and improving high frequency ride comfort. Movement of the sprung mass has been further controlled by the optimisation of the bound stopper clearance.
Adaptive Variable Suspension (AVS) allows the driver to choose the LS 460’s ride characteristics with a choice of two damper settings activated via a switch adjacent to the gear lever: ‘Normal’ mode, for a flat ride, 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, receiving data from numerous sensors to continuously optimise the damping force of each shock absorber. Data from an engine rpm sensor, wheel speed sensor, steering sensor, stop lamp sensor, front and rear vehicle height sensors, and three vertical acceleration, G-force sensors is interpreted by a control computer. This later activates the appropriate actuator within each shock absorber, continuously adjusting the damping force through nine incremental steps via a compressor located in front of the right front tyre.
Hence, in response to driving operation, vehicle body motion and road surface conditions, AVS activates the adjustable damping force shock absorbers to fulfill a wide range of specific control functions: ‘vehicle speed-sensitive control’ gradually increases the damping force as speeds rise, combining low speed comfort with high speed driveability and stability. ‘Anti-dive control’ increases front end damping force under braking to reduce front end dive. ‘Anti-squat control’ increases rear end damping force to minimise squat during acceleration. ‘Roll control’ optimises vehicle posture and stability by adjusting the damping force to both inner and outer shock absorbers through a bend. Unique to the LS 460, a new Vehicle Posture Control damping force control logic is incorporated within the Adaptive 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 adjustable dampers, feedback control is applied 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 and yaw, to which adds an enhanced perception of rear tyre grip.
In addition to Vehicle Posture Control, the AVS system’s ‘Non-linear H∞ Control’ provides independent control of all four shock absorbers to optimise damping force in response to changing road surfaces. ‘Rugged sensitive control’ reduces the degree of damping force when driving on rough roads, to effect a smooth, comfortable ride. ‘Vibration control of the unsprung mass’ increases the damping force as appropriate when resonance is detected in the unsprung mass, to minimise road surface transmitted NVH under all conditions. And ‘VDIM cooperative control’ adjusts the damping force in conjunction with the vehicle’s stability control system to maximise its efficiency.
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 10% whilst the Electric Power Steering (EPS) simultaneously increases steering assist torque by some 4%. These measures combine to minimise body roll, sharpen vehicle handling and optimise steering feel.
12-17-06, 03:14 PM
#3
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I assume your car then does not have AVS.
12-17-06, 06:31 PM
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The AVS/air suspension is an option only available on the 460L and not available on the SWB model, for some reason. Hopefully some of the L options will be available in the future on the SWB as not everyone needs or wants the added length. The AVS was a "must have" for me which led me immediately to the L version, even though the SWB would have been fine for my needs, and then I found the Touring package and jumped on that the same day I test drove it. It also has the above mentioned VGRS as part of the Touring package.
12-17-06, 08:27 PM
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hendjaz - yes, too bad AVS isn't available in the U.S. on the SWB. Not sure, but it seems like in the UK AVS is standard on all LS.
Even though the SWB might have been fine I'm sure you like the extra space in the back even if for only having lots of room for a bag without sticking it in the trunk.
Anyway, you've got the one I'd buy if I was in the market!
How's the ride with the 19's? Any noticeable tire noise? Also, what tires do you have on those 19's? Are they run flats? Congrats and thanks.
Even though the SWB might have been fine I'm sure you like the extra space in the back even if for only having lots of room for a bag without sticking it in the trunk.
Anyway, you've got the one I'd buy if I was in the market!
How's the ride with the 19's? Any noticeable tire noise? Also, what tires do you have on those 19's? Are they run flats? Congrats and thanks.
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