This paper deals with a new type of miniature air compressor which can be set up in a robot arm. It mainly consists of a stepping motor, a pneumatic rotary actuator, and four ON/OFF solenoid valves. Here, ON/OFF valves are suggested to be used as the inlet and outlet valves instead of ordinary check valves. The characteristics of this miniature compressor are experimentally investigated. By using ON/OFF valves as the inlet and outlet valves some advantages are obtained : 1) The miniature compressor has a better volume efficiency because the expansion line is greatly improved. 2) The miniature compressor has lower airflow resistance so it is easier to form a high vacuum. 3) The actuator can work as a compressor or a vacuum pump by controlling the four ON/OFF valves. Finally, the effects of composing a pneumatic energy saving system with this miniature compressor are proved and its ability to driving cylinder is also tested.

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This paper proposes a method to assess consumed energy of compressed air from the available energy of air in pneumatic actuating systems. This will make it possible to investigate the total efficiency of pneumatic actuating systems. The available energy is defined as the maximum work that can be extracted from air as it undergoes a reversible process from a given state to the atmospheric state on surrounding atmosphere. It is clarified that the available energy of air consists of two parts : power transmission energy and expansive energy, which represent pushing work from the upstream and work ability by expansion, respectively. Lastly, the efficiencies of compressors and air cylinders are discussed in terms of available energy, and an experiment on the consumption of available energy in a cylinder actuating system is introduced.

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Power circuit breakers, which are essential to protect electric power equipment and are required to operate at high speed, are usually driven by hydraulic control systems.
The present paper deals with numerical simulation as well as experimental examination of such a system composed of a spool-type 2-position 3-way directional control valve and a cylinder actuated by it. The conventionally used directional valve, in which a spool with two poppet-like collars works to switch the flow direction, has been found incapable of driving the piston fast enough. Numerical simulation of the system's performance predicts that this is caused by the structure of the valve, which allows both high and low pressure ports to be open during the switching motion. A new directional valve designed to avoid this defect was introduced to take the place of the conventional one, to greatly improve the response of the circuit breaker.

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The Intelligent Transport System (ITS), a worldwide research project, is now in progress in many countries. Speed control of the vehicle is one of the key technologies in this research project. Deceleration of vehicles is mainly controlled by brake systems. Air Over Hydraulic (AOH) brake system consists of air tanks, a brake valve (pressure control valve with a brake pedal), transducers, wheel cylinders and pistons, and pneumatic and hydraulic conduits. This system features strong braking force owing to the pneumatic power source and quick response of the hydraulic system, so it is a popular brake system for heavy-duty vehicles in Japan. Because of the compressibility of air, the transient characteristics of the brake pressure are obviously different from those of the passenger cars. Therefore, it is necessary to investigate the transient characteristics of the brake system, so as to develop a speed control system for automated driving of heavy-duty vehicles. The purpose of this study is to investigate the transient phenomena of the AOH brake system, to evaluate the appropriateness of the simulation model, and to reveal the main factor which results in the transient phenomena. By the comparison of simulation and experimental results, the following results have been obtained in the analysis of the transient characteristics of AOH brake system.·A mathematical model to analyze the AOH brake system has been proposed and validated.·It became clear that the transient characteristics of the AOH brake system are subject to the compressibility of air, and the inertia and viscous friction of brake oil in part of hydraulic conduits.

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