This study investigates sensorless position control of valveless pump-controlled hydraulic actuators for non-road mobile machinery (NRMM). The utilized hydraulic systems are direct driven hydraulics (DDH), a type of electrohydrostatic actuators (EHA), which uses an electric servomotor to drive hydraulic pumps of a single actuator. The advantages of DDH over traditional valve-controlled hydraulics are increased energy efficiency due to elimination of the valve losses and improved controllability. The servomotor driven pumps provides a possibility for sensorless position control of hydraulic cylinders without need for sensors. The sensorless position control was realized by simulating the interaction of DDH units and hydraulic cylinders of a testbed prototype hybrid mining loader. Measured data from a test work cycle was used to test the accuracy of the simulation. The results demonstrated that accuracy with maximum error of about 30 mm could be achieved without and with 1040 kg payload.

In the previous study, we developed a flexible pneumatic cylinder. A wrist rehabilitation device using these cylinders was also proposed and tested. To improve the position control performance of the cylinder, a disturbance observer with time-delay compensation and Smith’s compensator were applied into a built-in tiny embedded controller for position control of a single cylinder. As a result, it was confirmed that 40% improvement of the mean absolute error in experiments was achieved by using the proposed control scheme. In the next step, we aim to apply the improved controller into the attitude control system of the whole wrist rehabilitation device using three cylinders in which there exists an interference among three cylinders. To install the control system, it is necessary to measure lengths of bending cylinders. In this paper, we apply the disturbance observer to the attitude control of the device, and we propose a measuring method of bending tube length by using a twisted wire type linear potentiometer and a simple analytical model. Then, the proposed method is applied to the attitude control of the device.

One of an electrohydrodynamics (EHD) phenomenon is the induced flow of an EHD fluid in the presence of an electric field. In this paper, we describe a small pump in which the flow is generated by such an EHD phenomenon. In the case of pumps based on cylindrical electrodes, which thus far have been the focus of our research on EHD pumps, the total circumference length of the edge of the holes in the electrode that generates the rotational flow is small, leading to a small overall one-directional flow velocity. To investigate the influence of the total circumference length of the edge of the holes in the electrode, the area of the holes and the electric field intensity on pressure-flow rate characteristics, we produced ten different electrode pumps in which the electrode contains multiple holes. We measured the pressure-flow rate characteristics of our pumps and compared their performances.

In a variable displacement pump the swash plate has the ability to oscillate because of the excitation of the piston pressure forces. The odd number of pistons and the alternating piston pressure produce a periodically changing torque load. The resulting swash plate movement alters the piston stroke and therefore interacts with the piston pressure gradient. In this study a simulation model of the dynamics of a variable displacement pump is developed and the interaction between the swash plate movement and the commutation is investigated. The torque load influence of different valve plate designs is analyzed and presented in this paper.

This paper presents a simulation approach for the analysis of the flow in the axial gap of Gerotor pumps. The modeling approach is based on the coupling of a 2D CFD model of the lateral gap with a lumped parameter model for the description of the displacing action realized by the Gerotor unit. The CFD analysis takes advantages of OpenFOAM open source libraries and is performed in co-simulation with the lumped parameter model, previously presented and validated by the authors. Available experimental results are compared against the model predictions, as pertains the flow/pressure characteristic and port flow fluctuations. The paper describes the potentials of the proposed approach for quick predictions of the actual configuration of the lateral gap of the rotors as a function of the geometric clearances.

Hybrid underwater glider (HUG) combines the advantages of traditional autonomous underwater glider (AUG) and autonomous underwater vehicle (AUV), with long range and excellent maneuverability. The hydrodynamic shape of the underwater glider is an important influencing factor on gliding efficiency and maneuverability. In this paper, the hydrodynamic performances of several typical underwater glider body shapes are compared by using Computational Fluid Dynamics (CFD) method, the result shows the Spray glider body has the best hydrodynamic performance, and which is selected the reference body model. The influence of the wing parameters on gliding efficiency and static stability are studied by designing the orthogonal experiments, the sensitivity analysis of the wing parameters is studied by using One-At-a-time (OTA) method. In addition, based on the Whicker formula, the wing parameters are designed in detail: the axial position is located in the buoyancy center (CB), the chord length is 100mm, the aspect ratio is 10 and the sweep angle is 40º.

The purpose of this study is to develop a manipulator driven by a miniaturized artificial muscle in which a tiny compressor can be installed. Pneumatic actuators, such as pneumatic artificial rubber muscles (PARMs), have been widely used in many industrial and robotic research applications because they are compact and lightweight. However, the compressors driving such actuators are relatively large, and the peripheral devices such as filters and valves also tend to be large. To solve this size problem, the authors have been researching soft actuators driven by gas–liquid phase changes (GLPCs). In this research, a manipulator using an artificial rubber muscle driven by GLPCs was fabricated and a gripping experiment was conducted.

Erosion at the inner walls of hollow cylinders, in which cavitating jets flowed, was investigated experimentally using the jet cavitation erosion tester. Aluminum specimens with the representative size of 20 mm length, 20 mm outer diameter, and 5 mm inner diameter were prepared. The chamfered specimens had chamfers of 0.5, 1, 3, and 5 mm; the tapered specimens had tapers of 2.9°, 5.7°, 11.5°, and 17.2°. The test fluid was hydraulic oil with a viscosity grade of 32 and the oil temperature was maintained at 40°C. The upstream and downstream absolute pressures were 10.1 and 0.2 MPa. The standoff distance from the nozzle outlet and the specimen end surface was 15 mm. The exposure time was 8 hours and they were halved and observed after the experiment. The inner walls of the chamfered specimens were partially eroded at a slightly shorter distance from the chamfered edge of the downstream side, regardless of the chamfer magnitude. The erosion of divergent tapered specimens was not confirmed under the conditions.

The task of tolerance analysis usually addresses the question of the mechanical mountability of an assembly. We extend this viewpoint when talking about directional control valves in a cross-domain tolerance analysis; an analysis whose task is to determine the possible variation in the key product characteristics such as response dynamics, or flow gain, induced by a specific tolerance concept. On the other hand, tolerance synthesis aims at the determination of an optimal tolerance concept resulting in the compliance of the demanded tolerances for key product characteristics. Both issues require a way to identify the noise factors to be toleranced, a mathematical representation of the tolerances and a method to propagate their impact on the key product characteristics.

Laminar flow resistance in a straight pipe is generally used as a representative model for flow resistance because it is convenient to use and often yields reasonable resistance values in a straight pipe under steady state condition. However, the laminar flow resistance model in a straight pipe is not applicable to oil flow passage in a real circuit owing to the complex shape of the flow passage in a real circuit. Furthermore, a mathematical model of the fluid column in a pipe under in an inviscid flow condition is often used as an inertial model while considering dynamic conditions. Under actual operating conditions of an oil-hydraulic circuit, the two abovementioned effects, complex flow passage shape and flow dynamic characteristics, appear in viscous flow condition. Therefore, it is necessary to develop a new model or modeling method for solving these effects reasonably. This study aims to introduce a new modeling method based on the computational fluid dynamics (CFD) theory.

In mobile and stationary applications, axial piston machines are often used as pumps or motors. The paper on hand deals with the pressurization behavior of swash plate axial piston units. The pressurization is influenced amongst others by the pressure on high and low pressure line pHP and pLP and the rotational speed ω, geometric properties, e.g. the dead vol-ume V_dead, the valve plate design and the fluid characteristics (density ρ, viscosity ν, bulk modulus E). In the following a theoretical and an experimental analysis of the pressurization in the piston chamber and the resulting compression work is presented.

When products requiring careful handling such as semiconductor wafers and food (hereinafter called “workpieces”) are transported in manufacturing processes, problems can occur due to malfunctions that degrade sanitary conditions during the transport of workpieces through contact. An excellent device for transporting workpieces is a pneumatic non-contact holder (hereinafter called “holder”). However, this device has a disadvantage in that, although the vertical force on the workpiece can be controlled, it is not possible to control the horizontal force. As such, the workpiece is sometimes unstable and slides away from the holder. We changed the shape of the diffuser in the holder, and observed the behavior of the workpiece held by the holder. We measured the holding force and the pressure distribution for several holders in order to determine the influence of the diffuser shape on the behavior of the workpiece.

Understanding of friction characteristics of pneumatic cylinders may contribute to efficient design of a pneumatic cylinder system. However, friction behaviors of pneumatic cylinders have not completely been elucidated. In this paper, the steady-state and dynamic friction characteristics of three types of pneumatic cylinders are investigated in detail, and the effects of rod and piston packings on friction characteristics are also investigated using two types of lubricants, grease and oil. It is shown that the steady-state friction characteristic of the pneumatic cylinders with a good low speed performance is somewhat complicated compared to that of a standard type cylinder but can be expressed by a usual friction model with two velocity-range dependent parameters. It is also shown that the friction characteristics are dominated by piston packing and are strongly affected by lubricant type.

The fluid film behavior in the lubricating gap between piston and cylinder bore in axial piston machines is the main focus of this paper. The thermal behavior of the compressible viscous flow in the thin lubricating film formed between piston and cylinder bore plays a critical role on the interface performance and energy dissipation, therefore, deserves a thorough analysis. The temperature distribution in the fluid domain, as well as the heat flux from the fluid domain to the solid domain, follow the first, and the second laws of thermodynamics, however, are difficult to solve due to the constantly changing boundary conditions. The proposed fluid domain thermodynamic model calculates temperature distribution in the gap flow and the heat flux to the solid parts with a higher accuracy than the currently used fluid domain heat transfer model.

Micromouse contest is a kind of world popular competition for micro-mobile robots. Due to excellent mechanical performance, the electro-rheological (ER) brake has a great potential to realize smooth and rapid turning of the micromouse in the maze. A small-scale disc type ER brake is proposed and developed in this paper. Aiming to predict the performance of the ER brake, the mathematical model of the braking torque is established based on the constitutive model of one particle type ER fluid (ERF). The static and dynamic braking characteristics of the ER brake under different applied voltages are simulated and tested. The braking effect is verified by the good agreement between the simulated and tested results.

The demand for community wind turbines is increasing to fulfill local requirements and make the grid more stable. A turbine with a hydrostatic transmission is more reliable and cost effective than a conventional gearbox turbine making it an attractive alternative for community wind turbines. A power regenerative test platform has been built at the University of Minnesota to understand the performance of a hydrostatic transmission in a wind turbine. The design of the test bed is described in detail in this paper. The testbed emulates the rotor torque including the effects of the blade dynamics and pitch in a hardware-in-the-loop configuration. This test platform provides a powerful tool to investigate the performance of new components, controllers, fluids and energy storage methods on the hydrostatic wind turbine transmission.

This paper presents the effects on the fluid film temperature distribution and performance of the cylinder block/valve plate interface due to compression heating/cooling effects on the fluid film. The fluid film temperature distribution plays a major role in the solution of the non-isothermal fluid flow in the lubricating interface due to the change in fluid properties and heat fluxes to the surrounding solid bodies. The heat fluxes result in a modified temperature distributions and thermal deflections of the solid bodies. The changing fluid properties and the heat generation make this a complex numerical problem. For this purpose, a thermo-elastohydrodynamic model was developed which solves for the pressure and temperature distributions in the fluid film, the temperature distribution in the solid bodies and its elastic deformations due to pressure and thermal effects. The developed model is utilized to predict the fluid film temperature distributions in a 130 cc stock hydraulic unit.