Today’s machine tools are equipped with cooling systems for various subsystems of the machine. Due to higher cutting speeds and higher accuracy demands, cooling is necessary. Cooling systems for today’s machine tools are typically driven by pumps operating at a constant speed. The pumps deliver a constant amount of coolant regardless of the current state of the machine tool. The total energy consumption of the fluidic cooling system is between 20 - 30 % of the total energy consumption of the machine tool. This paper presents a variable volume flow cooling system and evaluates it at a real five axes machine through displacement measurements at a test workpiece.

In Japan, pipe inspection robots are required in many kinds of pipes for water supply, nuclear reactor and so on. A flexible and slim robot is desirable for traveling inside complex pipe. To improve mobility in pipes and facilitate recovering, a slim straight-shaped pipe inspection robot when it is not pressurized is required. In this study, a slim pipe inspection robot using extension type flexible pneumatic actuator with axial elastic/rigid fiber restraint was proposed and tested. The analytical model of the robot for coiling motion was also proposed and tested. As a result, it could be confirmed that the tested robot could travel in the pipe with about ten times diameter of the robot by coiling and extension motions like a snake.

The ongoing electrification of mobile machinery puts new demands on the hydraulic systems - they must become more efficient and quieter. One way to make them more efficient is to incorporate energy recovery. That often means that hydraulic pumps must also be able to work as motors. Efficient system solutions also need flow control for the pump. Traditionally, displacement control is used, but electrification makes speed control more relevant than ever before. All this increases the number of modes of operation for the hydraulic pump/motor, making commutation problematic. Commutation is crucial for both efficiency and noise. One feature sometimes used in pumps to facilitate commutation is the so-called ripple chambers. In this paper, the influence of such solutions is examined in simulation for different modes of operation. The results show that ripple chambers can be feasible for multi-mode operation.

In a typical pneumatic system to drive soft actuators, a control valve is the most heavy and expensive device. Therefore, a compact and inexpensive control valve has been desired. To solve such a problem, not only improving the valve itself but also reducing the number of valves can be considered. In this study, to decrease the number of valves to drive a complex pneumatic actuator with many chambers, a slide-gate mechanism type multi-port servo valve that can switch multiple ports and adjust the flow rate of many actuators simultaneously was proposed and tested. The tested valve consists of a rotational cam, multi-port, two servo motors for switching and adjusting, and so on. In this paper, the construction and operating principle of the tested valve are described. Furthermore, the radial bending/extension type flexible robot arm driven by the tested valve is also reported.

A newly conceived fully synchronized and full power-shift Output Coupled transmission for agricultural tractors was designed, based on the hypothesis of ideal components. This first version was simulated in a lumped parameter environment, including all the components of the transmission, the real hydraulic machines efficiencies, and a finite state machine based control system, to command hydraulic machines displacement and engagement/disengagement of clutches and synchronizers. The hydraulic transmission considered in the work, is subjected to challenging operating conditions, which cause deviations from the ideal command profiles due to volumetric and hydromechanical efficiencies. In the second phase, the parameters of the transmission are optimized, obtaining an upgraded design. The new set of parameters substantially increase the performances of the hydrostatic units, moving the operating points to favourable conditions. The latter design is finally compared to the first one, focusing on the performance of both the hydrostatic units and the overall interconnected system.

This study proposes a model capable of estimating the pump pressure pulsation damping effect changes, extending to previously unaddressed low-speed operating conditions in hydraulic elevators, all based on design parameters. The piping and muffler were modeled using 1D CFD, with the input side focusing on pulsation damping characteristics and neglecting pump internal impedance for flow input. The output side modeled the cylinder using a pipe model and a fixed throttle. The pressure pulsation in the pipe under conditions with and without a muffler was measured and compared with the estimated values from the proposed model. The results confirmed that the damping effect can be estimated with a maximum error of -9.1 dB, achieving the target error of less than 10 dB. This innovative approach provides a practical and accurate method for predicting and optimizing the performance of mufflers in hydraulic elevator systems.

Entrained air bubbles in hydraulic oils for fluid power transmission systems affect the dynamic behavior of the system. In this study, the dynamic behavior of air bubbles in oil was elucidated by visualization during compression, holding under high pressure, and decompression processes. The effect of the difference in the holding time and pressure on the state of the bubbles after decompression was experimentally investigated. In addition, the volume change ratio and pressure change of the trapped oil with entrained air bubbles was experimentally measured, and changes in the tangent bulk modulus was calculated. The relationship between the observed volume change ratio and pressure changes in the oil exhibited a characteristic behavior with hysteresis depending on the compression and decompression processes. The mathematical model of the equivalent bulk modulus was modified by considering the dissolved air. The modified mathematical model demonstrated good agreement with the experimental results for the compression and decompression processes.

Over the past few decades, the design criteria for hydraulic systems and components have increasingly focused on enhancing overall performance while simultaneously reducing power losses, weight, and physical dimensions. Indeed, modern hydraulic systems have exhibited a consistent rise in both flow rate output and maximum operating pressures. As a result, the ongoing demand for higher power density and stricter safety standards has driven the development of innovative, miniaturized components that integrate multiple functions into a single unit. In this context, the present study explores the key design features of an innovative combined hydraulic valve intended for high-pressure washing applications. The investigation was carried out through a combination of lumped and distributed numerical simulations, supported by experimental validation. Initially, a comprehensive lumped and distributed numerical model of the combined valve was created, emphasizing the mechanical interactions among internal components and the hydraulic pathways within the valve body. Subsequently, the predictive accuracy of the numerical model was clearly assessed through an extensive comparison between simulated and experimental results, covering a broad spectrum of operating conditions and geometrical parameters. Finally, the validated numerical model was employed to analyze the impact of sealing clearances on the valve’s operational behavior, performance efficiency, and internal leakages, during a representative working cycle.

A valve using the viscosity-temperature relationship and/or the phase change of liquids is developed. It has a simple structure; it is a metallic block with a straight tube serving as the flow path and is equipped with a temperature controller (Peltier module). The viscosity of hydraulic oil and the phase of municipal water within the tube can be altered by adjusting the temperature. Our findings are summarized as follows: Cooling the valve body reduced the flow rate of both liquids, eventually halting the flow entirely in the case of municipal water due to freezing. Conversely, heating the valve body increased the flow rate, allowing the liquid to resume its flow. This cooling and heating cycle enabled the valve to function as an on-off control mechanism. Notably, the effective configuration of the flow path differed between oil and water.

Multi-stable solenoids are novel energy-efficient actuators for holding any armature position powerless. Power is only needed for changing the position. Such solenoids combine the continuous adjustability of proportional solenoids with the energy efficiency of polarised magnetic circuits. A disadvantage is the sensitivity to unknown load forces that influence the remanent position. For compensating such forces, the actual position must be known. Information about position can be made available by self-sensing position determination, which is only based on electrical measurements.

This paper deals with a demonstration of self-sensing position determination on multi-stable solenoids for use in load force compensation. The basis is a demonstrator, which is investigated concerning its multi-stable behaviour at various load forces to illustrate the drawback. Based on its electro-magnetic behaviour, a suitable position observation method is derived, implemented and investigated. The method is applied for compensating unknown load forces, in order to demonstrate a potential use case.

A self-propelled hydraulic robot is currently being developed for use in teleoperation within nuclear power plants. In this paper, we proposed a new communication and control method that uses a water pressure supply tube instead of signal lines for signal transmission to improve the robot mobility by eliminating some of the numerous electrical signal lines in the robot cable. We evaluated the method using a hydraulic drive circuit simulating an actual robot and reached the following conclusions. 1) Adding pulse signals to the drive pressure caused delays due to tube expansion. 2) Setting the regulator set pressure higher than the target pulse height and controlling the pressurization time with a solenoid valve reduced expansion effects. The transmission time was 190 ms and the number of possible transmission signal patterns was 18; these results confirmed applicability of the method to controlling an 8-degrees of freedom arm of a teleoperated hydraulic robot.

This paper presents an experimental evaluation of fault detection and fault-tolerant control (FTC) for a water hydraulic robotic arm driven by an Air-Hydro Servo Booster (AHSB), a new type of pneumatically operated water-based hydrostatic transmission (HST). This HST incorporates a redundant sensor system consisting of water hydraulic pressure, pneumatic pressure, and piston displacement sensors. In this study, we derive the mathematical model of the controlled plant, then employ a Kalman Filter-based residual generation approach combined with Mahalanobis distance for anomaly scoring to leverage sensor redundancy for effective fault identification and isolation. The failures in this study are assumed to be: 1) disconnection of one of the sensors; 2) fluctuation of the internal friction in the hydraulic cylinder section; and 3) disturbance torque to the arm. However, it is assumed that no multiple failures occur simultaneously. The experimental evaluation is conducted on a single-axis water-hydraulic arm focusing on detecting and managing common failures, such as sensor disconnection and the application of external disturbance torque during the position tracking task. The results demonstrate that the proposed system can detect sensor faults, and make the transition to a sensorless control mode, maintaining sustained position control. Although the scope is limited to a simple one-joint robot, this paper is the first experimental report on FDI/FTC on HST-based and/or pneumatically operated water-hydraulic robots.

In caring for the elderly and people with disabilities, the periodic repositioning of the patient’s body is essential to prevent bedsores. These complex works put excessive mental and physical strain on caregivers. In the previous study, a soft actuator developed for wrist rehabilitation was used to develop a prototype active mattress to prevent bedsores. However, conventional actuators have the problem of being inflexible under vertical loads. Therefore, in this study, a Spring-Supported Flexible pneumatic Actuator (SSFA) with a coil spring as a part of the structure is proposed and investigated with the aim of developing a vertically flexible soft actuator. Specifically, the Crossed-Located Support Type SSFA and the Hemispherical Arrangement Support Type SSFA with vertical flexibility and capable of bending motion and vertical extension motion are developed. In addition to radial bending and vertical extension, the development of 3-Pillar Parallel Link Type SSFA and 6-Pillar Parallel Link Type SSFA capable of generating rotational motion around a vertical axis is proposed and investigated. The basic static characteristics of these actuators are also examined. The developed 6-Pillar Parallel Link Type SSFA is expected to be applied to health support devices that require multi-action movements, such as rehabilitation equipment. This is due to its ability to achieve both vertical flexibility and a high degree of freedom in movement.

The performance limits, efficiency and lifetime of axial piston machines are primarily depending on the performance of their tribological contacts. Those are influenced not only by the choice of material, but also by the respective contact’s geometric design. Based on a design study, this publication discusses the influence of various design features of axial piston machine slippers on their kinematic behavior and tribological performance. For that, an analytical study is used to show the influence of higher-level pump-design variables, such as the swivel angle and the case pressure on the slipper’s operating behavior. Finite element simulations are then used to show the influence of detailed geometric variables, such as the number and arrangement of slipper lands. Due to legal requirements and environmental protection the lead-containing brass alloys normally used for the slipper shall be replaced in future. Therefore, it is shown how the use of plastic affects the slipper’s deformation.

The rate of elderly population is growing rapidly in Japan, so that the shortage of young workforce is a serious problem. Many workers in the nursing field and other industries field experience back pain. In the lifting motion, there are roughly 2 types that are the squat method and the stoop one. The squat method is recommended because the burden on the waist is lowered than the stoop one. Many types of power assist devices are developed at research institutes around the world. However, most of them are wearable types, and they promote the stoop method from their mechanical property. In a previous study, we developed a non-wearing type pneumatic power assist device, which is an active type assist device, that takes the squat method into consideration and evaluated a lifting motion with the control system. In addition, we developed a passive type assist device as well as active one. However, we have only been able to evaluate unilateral support using the assist devices, so we have not confirmed in detail the influence of one-sided support and other support methods. In this study, we evaluate the support effect of the non-wearing type power assist device by measuring the muscle burden and the posture in a simple lifting motion for both one-sided and dual sided support. Additionally, we analyzed muscle activity using a musculoskeletal simulator.