Showing papers in "TRANSACTIONS OF THE JAPAN FLUID POWER SYSTEM SOCIETY in 2005"
TL;DR: In this article, the authors developed a portable pneumatic power source applicable to self-powered mobile applications such as wearable actuator and rescue robot etc., using dry ice as a source of power.
Abstract: This study is concerned with the development of a novel portable pneumatic power source applicable to self-powered mobile applications such as wearable actuator and rescue robot etc. Dry ice is chosen as a source of power for the pneumatic power source because it is nonpoisonous, easy to obtain and it expands 750 times in volume after being vaporized into gas. When dry ice is stored in the confined pressure container, it begins to liquefy after the pressure reaches the triple point (0.52[MPa(abs)],-56.6•Ž). In this process the pressure remains constant until all the dry ice melt into the liquid. When the state remains at triple point, the pressure does not decrease even though the gas is released from pressure container. By using this physical property of carbon dioxide, and by controlling the heat transfer from the surroundings into the pressure container, a noiseless, large capacity and portable pneumatic power source is developed.
21 citations
TL;DR: In this paper, the authors developed a safe power assist device that supports hip motion in those people who do not have the full range of such motion using an artificial curved pneumatic rubber muscle and wearable garment.
Abstract: This Study focuses on the development of a safe power assist device that supports hip motion in those people who do not have the full range of such motion using an artificial curved pneumatic rubber muscle and wearable garment. Soft texture and lightness of weight allow the power-assist device to be worn directly on the body similar to a coat. The device is soft and fits easily on the body. The artificial rubber muscle is fixed on the outfit. The device is safe and greatly mitigates the burden to the body. A soft touch-sensor activates the device automatically. The soft touch-sensor consists of fifty silicone rubbers cylinders that are fixed on two acrylic boards. The sensor sets between the garment and the back of the body. A Tilt-angle sensor fixed on the upper part of a link connects with rod of outfit. The angle of torso tilt determines the pressure desired for the artificial rubber muscle. The soft touch-sensor and tilt-angle sensor provide communication between the entire system and the human body. Analyses of the experimental data prove the support efficiency of the proposed power assist device.
11 citations
TL;DR: In this paper, a direct-driven water hydraulic high-speed solenoid valve was proposed for water hydraulics, which has anti-corrosion and low eddy current characteristics.
Abstract: When tap water is used as a pressure medium, the structure and material of an oil hydraulic high-speed solenoid valve can not be used because internal leakage and rust can occur. Accordingly, the authors have proposed a novel water hydraulic high-speed solenoid valve. This study is mainly concerned with the development of direct-driven water hydraulic high-speed solenoid valve. Through the investigation of soft magnetic material which has anti-corrosion and low eddy current characteristic, a solenoid design method using soft magnetic stainless steel instead of soft magnetic iron was established. Furthermore, a high-speed driving circuit, which compulsively imprints over-excitation voltage and demagnetization voltage onto the solenoid, is used in order to reduce the switching time of the water hydraulic high-speed solenoid valve. From the linear characteristics of Duty and mean flow, as well as fast switching time within 1.5ms, the validity of solenoid and direct driven valve design method for water hydraulics is verified.
6 citations
5 citations
TL;DR: In this article, a self-excited oscillation method has been used to estimate the dynamic parameters of the approximated second order transfer function without valuable measuring instruments such as a FFT analyzer.
Abstract: The hydraulic servo actuator system is generally dealt with as a second order delay element. The self-excited oscillation method has the advantage that it enables easy estimation of the dynamic parameters of the approximated second order transfer function without valuable measuring instruments such as a FFT analyzer. This study utilizing the self-excited oscillation method suggests the real-time identification algorithm. In order to demonstrate the method's effectiveness, the proposed method was experimentally compared with the frequency response characteristics. Results indicate that both method shows good coincident. It was also confirmed that when the supply pressure and additional torque are continuously changed in the hydraulic system, the damping coefficient and undamped natural frequency were updated on the PC monitor. In addition, amplitude and frequency correction coefficients are analytically obtained from the describing function considering the phase shift, and compared with the simulation results.
4 citations
TL;DR: In this paper, a new belt type Continuously Variable Transmission (CVT) with a 3.5 liter engine is presented, and the pulley ratio can be controlled by not only step motor but also linear solenoid for line pressure.
Abstract: A new-generation belt type Continuously Variable Transmission ranging up to 3.5 liter class engine is on the market. This CVT contributes to improvement in both efficiency and performance. This article describes a ‘control method’ newly developed for this CVT pulley ratio control. In the former control system, pulley ratio was controlled only by step-motor. Extra margin of line pressure was indispensable compared to primary pressure to accomplish target-ratio. If line pressure was not sufficient for primary pressure, pulley ratio couldn't be controlled accurately, and would be lower. On the other hand, in this new control, characteristics of hydro-mechanical shift system are utilized positively, and pulley ratio can be controlled by not only step-motor but also linear solenoid for line pressure. At this time, the most suitable line pressure is searched for by confirming the relation between command of step-motor and pulley ratio. In the result, line pressure can also be reduced a little less than primary pressure without causing unpleasant pulley ratio hunting.
3 citations
3 citations
TL;DR: In this paper, a model reference adaptive control (MRAC) strategy is used to control the injection molding machine, which can accommodate the unknown plant parameters and tune controller parameters to make output track a desired reference signal.
Abstract: Injection molding machines are widely used in industrial applications. The velocity of injection process and the pressure of dwelling process must be controlled with all products; however, such control is very difficult. In fact, the tuning of the controller parameters needed for high quality or multi-objective production takes a long time and requires a high level skill from the professional field engineer. The tuning can be seen as a pursuit of unknown plant parameters.This study uses a model reference adaptive control (MRAC) strategy to control the injection molding machine. This method can accommodate the unknown plant parameters and tune controller parameters to make output track a desired reference signal. In this first report, we derive the mathematical models and design, separately, adaptive velocity and pressure controllers for the model circuit used to simulate previous two processes. We then performed and evaluated the hybrid MRAC experiment and process MARC. We also examine the robustness of the proposed controller under parameter change, e.g., nozzle clogging, contraction of molded object, etc. The results confirm the proposed method's efficiency and robustness.
2 citations
Journal Article•
TL;DR: In this paper, a high performance control of electrohydraulic actuators for generating near periodic time varying trajectories is presented, which includes a robust feedback control for disturbance rejection, a repetitive control to compensate for periodic signals, and a previewed feedforward control for tracking time varying signals.
Abstract: This paper presents high performance control of electrohydraulic actuators for generating near periodic time varying trajectories. Such type of trajectories can be found in many industrial applications, particularly those involving master-slave type electronic cam-follower motion generation. The control algorithm includes a robust feedback control for disturbance rejection, a repetitive control to compensator for periodic signals, and a previewed feedforward control for tracking time varying signals. The three control actions are numerically solved simultaneously by formulating the control problem as a µ-synthesis problem. The µ-synthesis formulation includes practical design constraints by imposing frequency domain bounds of disturbance rejection, model matching error for tracking, unmodeled dynamics for robust stability, a periodic signal generator in the repetitive control, and a delay filter that corresponds to the preview length of the feedforward compensator. The proposed control design approach is applied to an electrohydraulic actuator to generate cam lobe profiles for cam shaft machining application. Control realization issues including model structure of electrohydraulic actuators, characterization of system model and uncertainty bounds, and controller order reduction for real-time implementation by digital signal processors are discussed. Experimental results are presented to demonstrate the design process and control performance.
2 citations
TL;DR: In this article, the authors examined the noise characteristics of a slit structure by changing it's height and outer diameter and found that when the inner diameter of the slit increases, the noise level increases.
Abstract: This research examines the noise characteristics of a slit structure by changing it's height and outer diameter. The slit structure consists of several disks shaped like round sections cut from a cylinder pipe that have been piled up. Compressed fluid enters the center of the piled-disk cylinder and is exhausted through a slit from the inside region to the outside. Because the pressure reduction is performed by a smooth flow through the slit, very quiet pressure reduction can be performed without causing flow turbulence or generating a shock wave. The relation of the Reynolds number and the noise level was clarified, and the visualization equipment was used to check for existence of a shock wave. The results obtained are summarized as follows. (1) When the height of the slit increases, the noise level increases. But, when upstream pressure is 300KPa or greater, regardless of the height and the outer diameter, there is a silencing effect more than 30dB. (2) When the upstream pressure was 600kPa, it was confirmed with visualization equipment that a shock wave did not occur in the slit type structure. (3) When the Reynolds number at exit increases, the noise level increases. Also the characteristics of the noise level is changed near the 2500 Reynolds number. (4) The noise effect increases, when the height of slit decreases and the outer diameter increases.
2 citations
TL;DR: In this article, an alternative method for obtaining the flow rate characteristics of all types of pneumatic components is presented, which is able to achieve a shorter measurement time and less air consumption than the ISO discharge method.
Abstract: This paper presents an alternative method for obtaining the flow rate characteristics of all types of pneumatic components. The proposed method determines flow rate characteristics by measuring pressure response in an Isothermal Chamber during discharge into the atmosphere. Expansive flow rate expression is used to satisfy various pneumatic components including valve, silencer, speed controller, etc. The paper also establishes a practical calculation technique for flow rate characteristics. Measurement results show the effectiveness of the proposed method. In addition, the proposed method is able to achieve a shorter measurement time and less air consumption than the ISO discharge method. The proposed method has the same precision as the ISO discharge method but it offers higher productivity.
TL;DR: In this article, the authors used the present simulation model that the self-excited vibration is caused by the interaction of the hydraulic and mechanical (structural) dynamics of the vehicle, which can be represented decisively by the phase lag of frequency response characteristics of hydraulic impedance of the supply line at the servo valve end.
Abstract: A hydraulic power steering system uses a hydro-mechanical bilateral servo mechanism to assist the driver in applying steering input commands to the vehicle. A violent self-excited vibration accompanied with sound, known as "judder", can occur during rapid steering maneuvers. It is explained explicitly using the present simulation model that the self-excited vibration is caused by the interaction of the hydraulic and mechanical (structural) dynamics of the vehicle. It is demonstrated that the main factors inducing the self-excited vibration are the response delay of wave propagation in the supply line, which can be represented decisively by the phase lag of frequency response characteristics of hydraulic impedance of the supply line at the servo valve end, as well as the sensitivity of the servo valve. Some specific analytical results that reveal the interaction of the hydraulic/mechanical dynamics are examined and compared with the experimental results performed on the bench test apparatus. Analytical results agree well with the test results. It is also explained that even if the system is dynamically unstable in substance the self-excited vibration can not occur owing to the coulomb friction acting on the rack bar, not when the vibration is excited over some threshold value. The proposed numerical simulation technique will be found to be very useful in searching the optimum parameters for steering design.
TL;DR: In this article, a high speed and accurate computing method for simulating the friction in transient laminar pipe flow in the method of characteristics was proposed, which consists of approximating W. Zielke's weighing function as a sum of impulse responses of first order lag systems.
Abstract: To accurately calculate the transient response in laminar flow, it is necessary to use frequency-dependent friction considering the velocity distribution. We developed a high speed and accurate computing method for simulating the friction in transient laminar pipe flow in the method of characteristics. This method consists of approximating W. Zielke's weighing function as a sum of impulse responses of first order lag systems. This method is normally well-understood. However, it is not usually applied to other calculating methods except the method of characteristics. Because the method of characteristics has a limit to its unique relation between discrete time and space, it is difficult to apply it to complicated pipe systems that include branches. In this paper, we propose application of the high speed and accurate calculating method of frequency-dependent friction to the CIP method. This proposed method has a higher flexibility than the method of characteristics in terms of the relation between discrete time and space. We measured transient response in the single, series, branch and complex pipelines. The results of the numerical calculation agree well with that of the experiment. These results show the effectiveness of the proposed method.
TL;DR: In this paper, the main poppet of a two-stage water hydraulic high speed solenoid valve using Hardware-in-the-Loop Simulation (HILS) is analyzed.
Abstract: This study is concerned with the dynamic analysis of the main poppet of two-stage water hydraulic high speed solenoid valve using Hardware-in-the-Loop Simulation (HILS). Since the behavior of a main valve of a two-stage water hydraulic high speed solenoid valve is difficult to measure, HILS technology is applied as an efficient and a precise method for the analysis of dynamic characteristics of this valve. In order to apply HILS to this valve, a dynamic modeling of the main valve is derived. From the results of HILS analysis, it is confirmed that the dynamic characteristic of the main valve is satisfactory. Furthermore, the validity of HILS analysis of this study is verified by experiment.
TL;DR: In this paper, a novel hydraulic actuator with built-in compound control function of displacement and thrust, and a method to improve the dynamic performance of an actuator were studied.
Abstract: A novel hydraulic actuator with built-in compound control function of displacement and thrust, and a method to improve the dynamic performance of an actuator were studied. Fundamental experiments and numerical analysis were conducted to examine the dynamic characteristics of the prototype hydraulic actuator. A sleeve orifice was introduced to improve the response of spool valve and a cylinder orifice was introduced to improve stability of the system, then their effectiveness was investigated by simulation study. From the experimental results with orifices, it was confirmed that the response of spool valve in thrust and displacement control and the stability of the system in displacement control were improved by orifices. Furthermore, the experimental results showed that adjusting the orifices was also effective in improving precision of the hydraulic actuator.
TL;DR: In this paper, the authors proposed a fluid switching transmission system (FST) that could be a solution for energy saving and developed a highly precise model of the FST system in order to analyze performance by simulation.
Abstract: As a continuously variable transmission, authors proposed a fluid switching transmission system (FST) that could be a solution for energy saving. In this study, a highly precise model of the FST system was developed in order to analyze performance of the FST system by simulation. It was imperative to carry out detailed analysis of the energy loss of components, such as oil motor, oil pump, flywheels, hoses and joints, etc. Thermal dynamics determine oil temperature and viscosity which influence energy loss. Simulation results showed a good agreement with experimental results. A technique for building a highly precise simulation model of the FST system was established.
TL;DR: In this article, a hydraulic actuator with built-in compound control function of displacement and thrust was used for compliance control of a stepping motor shaft and body, and their feedback weight parameters separately.
Abstract: Compliance control by a novel hydraulic actuator with built-in compound control function of displacement and thrust, and its applications have been studied. It was realized by measuring the rotational angles of stepping motor shaft and body, and adjusting their feedback weight parameters separately. The explanation of the compliance control function and analysis of static and dynamic characteristics were conducted. Through the preliminary experiments, it is confirmed that the actuator is very effective in the compliance control. Furthermore, as an application, experiment of grasping and lifting a ball was conducted. It was clear that the actuator can be used for the control of displacement, thrust and compliance.
TL;DR: In this article, the authors developed a proportional poppet type water hydraulic valve, which uses leakage from the clearance between the main Poppet and sleeve as initial flow to stabilize the initial operation of main POppet by taking advantage of characteristics of water that has low viscosity.
Abstract: This study concerns the development and fundamental characteristic analysis of a novel proportional poppet type water hydraulic valve. In this study, we developed a novel proportional poppet type water hydraulic valve which uses leakage from the clearance between the main poppet and sleeve as initial flow to stabilize the initial operation of main poppet by taking advantage of characteristics of water that has low viscosity and thereby leaks easily. The experiment verified that the relation between the main flow rate and pilot flow rate of the developed valve is linear and that the developed valve is suitable for the PWM control. Furthermore, it is also demonstrated that a decline in control chamber pressure that follows the change of pilot flow is caused by the occurrence of cavitation around the main poppet, and that fundamental characteristics of the developed valve remain unaffected by this event.
TL;DR: Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented in this paper, which can compensate the disturbances including nonlinear friction torque, leakage flow and load force.
Abstract: This paper studied the robust position control of cylinder using hydraulic transformer connected to constant pressure system. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation and experimental results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and the good positioning accuracy is obtained. It shows that the proposed controller is effective.
TL;DR: In this article, an air consumption measuring system for pneumatic elements, using an isothermal chamber and a laminar flow meter, was developed, and the characteristics of the measuring system components and presented the design specifications of the developed measuring system.
Abstract: Measurement and monitoring of air consumption in pneumatic elements are very important as countermeasures to environmental problems. However, it has been very difficult to measure the unsteady air flow and air consumption of such elements, with high degree of speed or accuracy. In this paper, we developed an air consumption measuring system for pneumatic elements, using an isothermal chamber and a laminar flow meter. We then evaluated the characteristics of the measuring system components and presented the design specifications of the developed measuring system. Moreover, we examined the frequency response and the transient response of this system. Finally, we practically tested the device to measure the air consumption of a pneumatic air tool. As a result, we confirmed the high usefulness.