This paper introduces a new concept for enhancing the handling characteristics and directional stability of trucks and buses during high-speed driving. Generally, the phase lag and gain of a vehicle's handling response increase with vehicle speed. Excessive phase lag will cause delay in the vehicle reaching the driver's intended course, resulting in oversteering, while excessive gain will intensify oversteering, making the vehicle weave. High phase lag will also increase the time required for disturbances, such as road surface roughness, to be transmitted to the driver's hand on the steering wheel, delaying corrective steering and producing steering weave. In the case of trucks and buses, the phase lag magnitude can reach four or five times that of a passenger car. A parallel operating system consisting of conventional hydraulic-assisted mechanical steering and electronic control will decrease phase lag while retaining the increase in gain, while an electronic limited-slip differential will protect against external disturbances and reduce both the phase lag and gain. An integrated system incorporating such steering and differential control reduces the lateral acceleration, yawing and rolling angle, and steering weave during high-speed driving to the equivalent of a speed level 40 km/h lower than the actual vehicle speed.
Abstract