Hydraulic hoses having a tuning cable, called 'Resonator hoses', are frequently used to attenuate any pressure pulsation in a hydraulic system to reduce the noise inside an automobile. To optimize on the design of resonator hoses, a number of models have been developed in the frequency domain. However, a suitable model has yet to be found for simulating the complex configurations and non-linear phenomena in the pipelines including resonator hoses.
This paper describes a time-domain simulation technique for resonator hoses and deals with the effects of the inner tube (tuning cable) as regards pulsation damping.
In the modelling of a resonator hose, the hydraulic characteristics of the inner tube were studied using experiments. According to the experimental results, the leakage flowing through the inner-tube wall and the stiffness of the inner-tube were determined in the model. To simulate complex pipelines, the model of the resonator hose was added to the system simulation program (PAP) in which the method of characteristics was used. The simulated results were compared to the experimental ones to confirm accuracy.
Using this simulation model, the effects of the stiffness and leakage characteristics of the inner-tube could be obtained by the transmission losses calculated from the simulated results. In addition, the transmission losses for the various combinations of the resonator hoses were discussed.

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In order to reduce fuel consumption and exhaust gases of vehicles in city traffic, it has been considered technically feasible to recover vehicle's kinetic energy that is otherwise lost as heat during braking. An energy recovery system using a rotating flywheel seems to be effective for vehicle applications due to its high energy density. The authors propose a Constant Pressure System (CPS) which is a simple hydraulic drive system for engine-flywheel hybrid vehicles. CPS can easily realize power transmission and vehicle traction control. In this study, analytical modeling and simulations of the hybrid vehicle using CPS are presented to evaluate its fuel saving potential. Simulations were performed based on the experimental efficiency data of an FFC (Fluid Force Couple) type pump/motor. Simulation results indicate that it is possible to improve fuel economy in urban traffic cases.

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The time delay control (TDC) method has been applied to a force control system of an electrohydraulic servo mechanism with spring and inertial loads. The modeling error and the disturbance of the system can be estimated and compensated through the use of the TDC method. Two types of a simple linear model of the controlled object are used to discuss the effects of modeling. As the state variable, design model-1 uses cylinder force and design model-2 uses cylinder force together with piston velocity. Simulation and experimental results show that the TDC system with design model-2 is more effective for the case of rapid change of piston speed.
The results of this research show that robust control of an electrohydraulic force control servo mechanism can be realized with simple control a system by TDC.

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This paper describes a new design scheme of a discrete-time control for a pneumatic servo system with an adaptive time delay compensator. The control scheme given in the paper is capable of accommodating changes in time delay of pneumatic servo systems and similar linear systems with unknown or varying time delays and parameters. In addition, this control scheme rejects load disturbances without requiring an estimate of the disturbance and not producing an offset in the output. The derivation of the control scheme is based on a discrete formulation of the modified Smith time delay compensator and adaptive pole-placement strategy. The paper shows simulation results where the plant has a varying time delay and external disturbances and the laboratory experimental results where the pneumatic servo system has a system internal disturbance such as stick friction and additive load force in varying moving distance and load mass. The experimental results clearly show its superior performance and disturbance rejection.

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In the spot wedling, the electrode force is usually kept constant during a short welding time because of a too low response speed of the air cylinder and it can not satisfy the developing requirements of spot welding technology. A new motion and force compound control cylinder has been developed to control the electrode force at a high speed. It is composed of a motion control piston and force control piston on the same rod.
The optimal structural parameters and operating conditions of the cylinder are analyzed in the paper. Experiments indicate that the response time of the system for a step input is improved from 0.2 [s] for the conventional cylinder to 0.010 [s] for the cylinder developed here, and the bandwidth is improved from 10 to about 100 [Hz]. It will be possible with using this cylinder to avoid spattering during spot welding and to reduce the welding defects, and increase the welding strength. It can also be applied in other fields of fast control.

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