الموضوع: Vehicle Stability Assist (VSA) - Honda

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Vehicle Stability Assist Development Objectives

Tokyo, July 2, 1997 --- From the early days, Honda has looked atmeans to increase active safety. It was the first to offer a four-wheelanti-lock brake (ABS) system in Japan, and the first in the world tosuccessfully develop a traction control system for front wheel drivevehicles.

The Vehicle Stability Assist (VSA) system we are introducingtoday adds side slip control to ABS and TCS systems. This new system controlssudden changes in vehicle behavior, giving the driver the time to keep controlof the situation. When driving in the rain or on snow, the system stabilizes thevehicle, reducing counter-productive driver tension.

In order not to spoil driving pleasure we have devised a uniquesystem based on the concept of "vehicle stabilization through control of thefront wheels". VSA is a simple, reliable system enhancing performance anddriving pleasure.

- the rear wheels slip sideways, resulting in a sudden change inheading toward the inside (spin) = oversteer.

- the front wheels slip sideways, resulting in a wider corneringline = understeer

1) Oversteer control:

By braking the outer front wheel, an outward moment isgenerated. The cornering force at the front is thus reduced, decreasing the spingenerating moment and stabilizing vehicle behavior

* Detection and Control

The yaw rate intended by the driver (target yaw rate) iscalculated according to lateral acceleration, steering angle and vehicle speed. If the actual yaw rate exceeds the target, the VSA system brakes the outsidefront wheel to reduce yaw. Brake Application to Outer Front Wheel = Oversteer Control

2) Understeer control when cornering under power

When the car's cornering line widens under excessive throttleapplication, the system intervenes by reducing engine torque and, if necessary, by braking the inside front wheel. This creates an inward moment helping the cartrace the line originally intended by the driver

Detection and Control

The yaw rate intended by the driver (target yaw rate) iscalculated using steering angle and vehicle speed. If the actual yaw rate isbelow target, the system intervenes to reduce engine power and increase yawrate. If necessary, the system will also brake the inner front wheel.

Engine Torque Reduction + Inner Front Wheel Braking = Understeer Control When Cornering Under Power

3) Standing Start Slip Control

When accelerating on a split surface with different gripcoefficients, engine torque is usually transmitted to the wheel with the lowestgrip level, resulting in traction loss. By braking the wheel with the lowestgrip, greater torque is provided to the wheel on the other side, ensuring quick, powerful acceleration

4) Braking control under cornering

When high cornering forces are detected, ABS automaticallyswitches to the 4-channel mode (3-channel mode when in a straight line or whencornering at lower speeds). Taking advantage of the weight transfer duringcornering, the system applies a higher brake pressure on the outer rear wheel, improving braking performance

System Configuration and Principal of Operation

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أحمد سامي