Performance Test of an AC Servomotor Drive Valveless Hydraulic Power Steering by Using a Passive Type Electro-hydraulic Load Simulator

Abstract

Recent passenger cars have been equipped with electric power steering (PS) for both energy conservation and safe cruise assistance such as lane maintenance and vehicle distance control. However heavy-duty commercial vehicles are still steered with hydro-mechanical PS because of their greater steering torque. It is necessary to develop high efficient electro-hydraulic control PS for hybrid commercial vehicles in order to conserve battery power. The authors present a new type of AC-servomotor drive pump control valveless PS and demonstrate improved efficiency in power consumption compared to current valve-control PS from 2.5kW to 340W at full slalom steering in 14s of a 4-ton payload vehicle. Following this study, steering feel, restoring performance and insensitivity against kickback torque are examined by using a passive type load simulator with maximum torque capacity of 1500Nm on the basis of the Fiala two-wheel tire model.