This paper deals with investigations on propagation and attenuation characteristics of fluidborne pressure pulsation generated by a pump in a complete power steering hydraulic transmission circuit. Emphasis is placed on the accurate measurement of transfer matrix parameters, and hence, transmission loss of the resonator hose, a kind of hydraulic silencer, consisting of a reinforced hose and spiral tubes positioned coaxially inside it, for the purpose of obtaining basic data for developing a satisfactory mathematical model for the attenuation characteristics in future. Experimental results show that the pulsation attenuation characteristics of resonator hose (i.e., transmission loss) is remarkably affected by the resonance of longitudinal vibration of finite-length hose wall as well as its visco-elastic properties. It is also shown that the predicted pressure pulsations from measured transfer matrix parameters of system components, including resonator hose and measured pump source characteristics in any position in a real complete power steering hydraulic circuit, agree well with the measured results over a wide frequency range up to around 1.5 kHz in interest. These satisfactory test results will assist engineers in the modeling and design of resonator hoses, and hence, should provide a means for designing a quieter automotive power steering hydraulic system.

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This paper deals with a new method for optimal control of pneumatic cylinders with a disturbance observer. The pneumatic cylinder has been used as an industrial actuator, because it is simple, small and economic. The PID or I-PD controller is used for position control of the cylinder, because its performance is excellent. However it is difficult to decide precisely the position of piston rod, owing to air compression and friction of the device itself. Furthermore, the dynamic response of these controllers depend on their control gains. Therefore these gains should be adjusted properly when the controlled object is changed. So, we consider the variation of the controlled object as a disturbance, and try to make compensation for its inference. We compose a better robust system from the disturbance observer with LQI controller. The experimental result shows that the proposed method has a better performance than the conventional LQI controller.

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This paper proposes a PWM (pulse-width-modulation) control of a pneumatic single-rod cylinder positioning system. In the system, the rod chamber pressure of the cylinder remains constant, and the head chamber pressure is controlled by two solenoid valves. The valves are under PWM mode control. In synthesizing the PWM servomechanism, the solenoid valves are characterized by a static characteristic equation incorporating the nonlinear elements caused by the switching time of the valve. The proposed PWM method can assign the steady-state duty ratios of the valves to the desired locations of their flow characteristics, which makes it possible for the system to avoid the dead-zone or the nonlinear region caused by the PWM solenoid valves. Also, a threshold near the desired position is set up so that the valves are closed at steady state. An experimental study of the proposed system is performed. These experiments verify the theoretical design work, and indicate that the proposed control system is feasible for pneumatic positioning.

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Improvement in the pump flow control performance in the low pressure side for the hydraulic variable displacement piston pumps using a sensor by making use of the variable gain method in the minor feedback system.
Variable gain method, in which the pressure monitoring signal of load pressure in the minor feedback system is added to the feedback system of flow control as the feedback compensation and flow gain of control amplifier is changed to the variable gain from the fixed gain.
As a result, the following improvements were achieved by this change.
1. In the low pressure side, the hysteresis performance was improved by 30% and repeatability was also enhanced.
2. Good results could be obtained from the flow response performance, especially the downward response in the minimum loaded pressure.
3. Concerning the pressure flow curve performance up to 5 MPa.the fluctuation of the controlled flow was decreased by using the dual gain amplifier method.

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