Dynamic analysis and stability of a power assist steering system

This paper presents dynamic analysis of a power assist steering system with emphasis on system stability. The transfer functions that describe assisted steering system responses, and driver feel of the road are obtained in analytical form. To determine torque-speed requirements of the assist actuator we chose zero and low speed parking, and high speed random steer conditions to investigate worst case loads. A high level of steering assist can be a source of instability of the plant that results in vibration of a steering column and undesirable vehicle performance. Stability requirements are determined and critical parameters of assist design are obtained as a solution of the nonlinear equation that describes the boundary of stability