The pneumatic cylinder has internal rubber seals. When the piston moves toward the desired position, the seal sticks and slides and then attaches itself to the cylinder wall or piston rod, near the final position. Therefore the viscoelastic formation of the seal occurs, witch has effects on control performances, such as positioning accuracy, stability and settling delay in this region. Combination of stick and slide mode control models is necessary to execute highly stable and accurate control of a pneumatic cylinder, but these modes can not be observed directly.
In this report, a method is proposed for discriminating whether the seal sticks or slides in real time and for its control by choosing and switching between slide or stick modes. The control performance is specified experimentally.

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In order to improve the vibration isolation performance and to decrease the energy consumption of an active suspension with a pneumatic cylinder, a frequency dependent control, an energy regenerating control and so on have already been developed. In this study, to build up a stand-alone type active suspension which reconciles vibration isolation performance and energy savings, a driving system comprising a small sized compressor and an energy regeneration circuit is proposed. From some experiments, the control performance of the proposed system is investigated. The results show the feasibility of the proposed system.

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Dual-layered parallel impedance control is proposed for a hydraulic master-slave system. It has the characteristic of constructing two layers at both the master and the slave site. In each layer, two parallel subsystems are introduced, and impedance matching between the two parallel subsystems is accomplished. Stability condition of the master-slave system is also discussed. The major contribution of this paper is a realization of new human-centered maneuverability in a hydraulic master-slave system by tailoring the virtual impedance of the master to suit the operator for a given task. The proposed control architecture is applied to a hydraulic master-slave system and its validity is proved by the experimental results.

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This paper deals with active noise control of a variable displacement swash plate type axial piston pump. The primary cause of noise generation of a piston pump is the exciting force due to sudden pressure change in the rotor cylinders. We tried a new method to compensate the pump exciting force by activating two built-in control cylinders using an electro-hydraulic servo valve and sinusoidal signals synchronous with the pump rotation. This method is not to suppress the exciting force itself but to prevent it from vibrating the pump and consequently to reduce the peak level of frequency components of the pump noise. Through the experiments, the exciting force compensation has been verified to be effective for noise reduction of a pump. The noise level could be reduced, for example, to 68 dB from 74 dB for the pump equipped with rubber vibration isolators, and to 70 dB from 82 dB without isolators.

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