Analysis of Tuning Cables for Reduction of Fluidborne Noise in Automotive Power Steering Hydraulic Lines

A distributed parameter mathematical model of a complete power steering hydraulic transmission circuit has been developed and implemented on a personal computer to analyze the effect of tuning cables on the attenuation of pressure waves generated by the pump. Tuning cables, flexible tubes positioned coaxially inside a length of hose placed at a convenient location in the circuit, reduce fluidborne noise primarily by destructive interference and viscous damping. The model uses a transfer matrix approach that includes two-dimensional viscous flow and three-dimensional fluid-structure interaction. It can be used for sizing and positioning tuning cable devices in power steering as well as other hydraulic systems prior to verification testing of the circuit.