Yaw Rate Response Research Articles

Two Degree of Freedom/H∞Controller Synthesis for Active Four Wheel Steering Vehicles

SUMMARY This paper proposes an active front and rear wheel steering control system that simultaneously achieves both lateral acceleration and yaw rate responses always desirable regardless of changes in vehicle dynamics. First, this paper describes a method to accurately estimate physical parameters in the four wheel steering vehicle model, including the dynamics of a steering actuator, by applying the maximum likelihood estimation method. Next, the structure of the proposed front and rear steering control system is described. This control system has for its purpose to coincide both the lateral acceleration and yaw rate responses of the vehicle with the responses of the respective desirable reference models, as well as to make it a robust system against changes in vehicle dynamics and external disturbances. To achieve both objectives, a two-degree-of-freedom control system theory is employed. Then the paper shows the viability of the proposed steering control system through computer simulations. Finally, the results of proving ground tests carried out with a test vehicle equipped with a front and rear wheel steering mechanism driven by the digital computer and electric powered actuator are shown. From these results, it was confirmed that the proposed active front and rear wheel steering control system would contribute greatly to the improvement of vehicle handling qualities and preventive safety.

A Tractor Handling Study

SUMMARY Agricultural tractors are relatively slow moving vehicles but a good steer response under all working conditions is generally required. This paper evaluates the effect of ground slope, axle load, ground speed, tyres and ground surface on yaw rate response to steer input.

Steady State Steering Response

SUMMARY The yaw rate response for a two-degree-of-freedom car model requires a family of curves for different degrees of oversteer or understeer. By use of non-dimensional co-ordinates this family is reduced to one single curve. The ordinate ρ is the ratio of yaw rate response to that of a neutral steering car at the same speed and is less than 1 for understeer and greater than 1 for oversteer. Since ρ is also the ratio of the side-slip angle response it is hence, a unique measure of the steady-state steering characteristics.

An Investigation of High-Speed Automobile Steering Response

SUMMARY The significance of the effects of steering compliance and aerodynamic life on high speed automobile's steering response was investigated on two vehicles, a Ford Falcon XW (1969) station-wagon and a GM-Holden Kingswood HQ (1974) sedan. An aerofoil was mounted above the front bumper bar of the Ford Falcon to enable the simulation of vehicles with very degraded aerodynamic characteristics. Mathematical analysis showed the importance of the inclusion of steering compliance effects in determining stability factor, and hence the vehicle's high speed yaw rate sensitivity. Both experiments and theory showed that the actual high speed yaw rate response is not significantly less than that predicted from a low speed skid pad test, however, slight errors were found which are likely to be due to steering system nonlinearity and the effects of aerodynamic lift.