Pilot-pressure supply circuit of construction machinery consumes 2-3% of engine's horsepower. A method of improving energy efficiency is studied by many researchers. Switched Inertance Hydraulic Converters (SIHC) which is one type of digital hydraulic circuit has been proposed as a solution to reduce throttling loss through control valve in a hydraulic circuit. A digital-hydraulic pressure reducing circuit is an example of SIHC which may show high energy efficiency because it does not use a throttling orifice. It can obtain output flowrate larger than supply flowrate. This paper aims to apply the digital-hydraulic pressure reducing circuit to pilot-pressure supply circuit of construction machinery. A control method of the pilot pressure to follow demanded pilot pressure is proposed. A simulation model is experimentally verified. The proposed control method is validated. Controllability and loss reduction effect are investigated by simulation based on transient pressure and flowrate data of an actual construction machinery in operation.
Recently wearable power assist robots have been developed in order to solve labor shortage and reduce work load. It is desirable that the wearable power assist robots should be lightweight and flexible from the viewpoint of reducing burden on wearers and maintaining safety. Pneumatic actuators are used in various wearable power assist devices because of high power-weight ratio and flexibility. The authors had developed the portable air supply system for retrieving and re-compressing exhausted air using the variable volume tank constructed with elastic material. In addition, the authors had developed the hollow cylindrical-shaped variable volume tank with the reduced internal volume to downsize and improve energy characteristics. The purpose of this study is to construct deformation model to design the hollow cylindrical-shaped variable volume tank with desired characteristics. The effectiveness of the proposed model is verified by comparing the results of the calculated and the measured values. Finally, the proposed model is applied to the multi-layered hollow cylindrical-shaped variable volume tank.
In recent years, model-based development (MBD), a system development method that incorporates simulation technology, has been increasingly adopted in the design of valve-box hydraulic circuits for automatic transmissions. This method has various advantages in terms of development cost and time. On the other hand, hydraulic vibration, response delay, and pressure over/undershoot may occur in actual machine under development that were not easily predicted in the simulation. Although it is necessary to understand the characteristics of the actual machine in order to analyze these problems, the measurement technology has not yet been established. The objective of this research is to develop a measurement technique for hydraulic impedance, which represents the frequency characteristics in the valve box of an automatic transmission, and to identify the parameters. This will not only enable us to evaluate the response and stability of the actual machine, but also to analyze the causes of actual phenomena and improve the accuracy of the model. It will lead to an improvement in design accuracy.
In this paper, the sealing characteristics of the piston ring of the piston in a bent axis type axial piston motor are clarified. In order to clarify the sealing mechanism of the piston ring, a test rig was developed and the behavior of the piston ring was visualized and measured. Next, the measured piston ring behavior was modeled and fluid structure interaction analysis was performed to analyze the leakage flow rate of the piston ring. The effect of the number and arrangement of piston rings on the leakage flow rate of the piston rings was also investigated. Comparison of experimental and analytical leakage flow rates indicated that the 2nd piston ring may have lower sealing performance than the 1st piston ring. The leakage flow rate from the piston ring gap was modeled by the flow between parallel plates and estimated the ratio of the leakage flow rate from that to the total leakage flow rate. The results showed that cross section profile of piston ring gap may affects the leakage flow rate.
The purpose of this research is a development of simulation models of pneumatic steady flow through straight uniform tubes with heat transfer and wall friction. Assuming that the tube wall temperature and the inlet air temperature are constant, the air temperature inside the tube approaches to the tube wall temperature along the flow direction and the effect of the heat transfer becomes negligibly small at the downstream region far from the entrance. We developed the two models which simulate the flow in the heat transfer region and in the adiabatic region respectively. They are serially connected to model the whole flow in the tube. We made use of feedback control techniques to solve the equations which described the two models. In the experiment the compressed air was supplied from the constant temperature tank to the copper tube which was set in the water jacket to adjust the wall temperature. The pressure at both ends of the tube and the mass flowrate were measured. The usefulness of the newly developed models was verified by comparing the simulation results with the experimental results.
A robot hand is required to generate a large grasping force. Furthermore, it is required that one finger should possess multiple degrees of freedom and the fingertips should be positioned freely to grasp and manipulate objects of various sizes and shapes. A function to adjust the stiffness is also required to control the force and realize stable grasping. The development of a hand with these functions at a high level is a technical problem. We propose a multi-degree-of-freedom finger module that uses pneumatic cylinders and a parallel link mechanism. The proposed hand has adjustable stiffness while maintaining high grasping force-to-weight ratio. In addition, the proposed hand was able to estimate the external force acting on the fingertip from the differential pressure and a kinematics model. By using the estimated external force for control, adjustable stiffness was realized without using a force sensor. This paper also describes the design method of the finger module. We experimentally confirmed that the proposed hand was able to satisfy various target specifications. In addition, it was able to realize multiple functions of a hand using a compact mechanism.
The liquid inside the McKibben Artificial Muscle is extracted using the elasticity of the expanding body. Therefore, in order for the muscles to contract, a large pressure exceeding the elastic force of the expanding body is required. In addition, the calculation of the contractile force exerted by artificial muscles is extremely complicated and difficult to predict. In this study, we proposed and developed a new artificial muscle (The EHD artificial muscle) with an EHD pump driving source that can generate bi-directional flow by applying the EHD phenomenon. By using the EHD pump as the driving source, the muscle can be relaxed without the elasticity of the expanding body. In addition, the structure of the EHD artificial muscle is simpler than that of the McKibben type, and it is easier to calculate the contraction force to be output.
This paper discusses an identification input for nominal hydraulic arms. First, we focus on an input-output nonlinearity which exists even in the absence of nonlinear friction and prevents us from observing and measuring the input-output behaviors. Second, we propose a new identification input based on the physical parameters of hydraulic arms via the special nondimensionalization technique. Third, we show the effectiveness of the new identification input experimentally. Finally, we show an application of the proposed new identification input to observe and measure the input-output behaviors. Especially, in the frequency domain, we identify the uncertainty that was impossible for the conventional identification input.
This paper presents the effect of the rotational speed of a check ball in a hydraulic L-tube on the translational motion caused by the Magnus effect. A spring-driven ball check valve is one of the most important components of a hydraulic system and controls the position of the ball to prevent backflow. To simplify the structure, the springs must be eliminated. To this end, it is necessary to clarify the flow pattern of the check ball in an L-shaped pipe and the rotational and translational behaviors of the ball. In this study, the position of the inlet pipe and the availability of the check were determined using Computer Aided Engineering (CAE) tools. By moving the position of the inlet pipe from the top to the bottom of the housing, the direction of the rotation of the ball was reversed, and the behavior changed significantly. It was found that the Magnus force, which causes the ball to levitate by rotating it in the opposite direction to the flow, acts to shorten the floating time.
