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.

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A new bilateral master-slave control system for the large-scale manipulator is proposed. The aim of the system is to cope with its large payload capability and achieve the dexterity to accomplish its assembling and the deburring tasks. To achieve this goal, three new control methods were introduced, i.e. the new bilateral servomechanism combined with the symmetric type and the force reflection type, the variable compliance control and the disturbance force compensation. In the first report, the preceding test results for the simple single joint-model were described. The promising results of those preceding tests motivated the authors to fabricate a 6-DOF prototype manipulator. In this paper, the results from the working property evaluation of this prototype model are reported.

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The offset of secondary pressure is a recurring problem in pressure regulators. In conventional pressure regulators, reduction of the offset requires increase of loop gain, which deteriorates pressure control stability. This paper proposes a new pressure regulator that reduces the offset without loss of stability. The pressure regulator is composed of a pilot valve, a Venturi tube for flow rate detection and a main valve. The pressure at the throat of Venturi is fed back to the pilot valve, which reduces the offset of the regulating pressure. Simulation was carried out for the proposed system, and design parameters were determined thereby. A prototype of the designed pilot valve was manufactured and experimented upon. The experimental results revealed the effectiveness of the proposed design.

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