In this study, the force and velocity control of hydraulic cylinders was performed using a single proportional-type valve with a built-in overlap-type 4-way spool valve. In the case of the velocity control, the valve opening value of a proportional-type valve was calculated by mean of a personal computer to the desired flow rate flowing into the hydraulic cylinder. For the purpose of determining the valve opening, the pressure value in the hydraulic circuit was detected using pressure sensors and a characteristic restrictor equation was employed. Thus, the control method to keep the constant flow rate, which is not affected by a load, was considered.
In the force control of hydraulic cylinders, the pressure control of a cylinder chamber was carried out when the flow rate running into the cylinder was nearly equal to zero for such cases as a fastening body and a loading one. For pressure control on-off operation to a proportional-type valve method was adopted, and the desired force of the cylinder was controlled by taking a little flow in and out of the cylinder.
In this paper, the above-mentioned control methods are proposed and the control characteristics are reported.

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In order to clarify the buffer action of fluid films on impulse and vibration, the behavior is examined experimentally by using a model of normally impacting two bodies. The model consists of fluid film, impacting objects (a cylinder and sphere) and a cantilever. Fluid film thickness, initial height and mass of the cylinder and sphere, and deflection of a cantilever are used as parameters. By estimating the buffer action with the coefficient of rebound, for the case where the impacting velocity is relatively small and film thickness is comparatively large, the coefficient of rebound becomes small, that is, the buffer action is clearly recognized. For the case of the same value of the momentum before the impact, the area-contacting is able to obtain a larger buffer action than point-contacting. The comparison with and the discussion about the theoretical results are also presented.

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Pneumatic cylinders are used widely as low-cost actuators in various automatic assembly machines. Recently, high-speed driving of pneumatic cylinders have become an important subject of research, since these machines must be driven at high-speeds.
The authors have analyzed dynamic behavior of a pneumatic cylinder driven at a high-speed. It was found that the velocity response of the piston as well as the pressure response of the air in the cylinder chamber showed an oscillatory behavior when the pneumatic cylinder was driven at a high-speed, especially in the meter-out circuit. From an application of this oscillatory behavior, a new method of driving a pneumatic cylinder at a high-speed has been proposed. In this new driving method, the piston will be driven ideally, meaning that the response will be fast while the velocity at the end of the cylinder will be low, and the impact will be at an acceptable level.
In this report, the basic equations expressing the dynamic characteristics of pneumatic cylinders are normalized, and generalized conditions are derived for high-speed driving of the pneumatic cylinders with the proposed method. These conditions mean the generalized optimum relations between the adjustable orifice and load. From these relations, it is possible to adjust the optimum orifice areas for high-speed driving of pneumatic cylinders.

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