Matti Vilenius’s research while affiliated with Tampere University and other places

Water hydraulics is one of the most rapidly growing areas in the field of fluid power. Environmental and safety aspects have strong effect to the use of water hydraulics. Also high level material technology and intelligent control systems enable better characteristics for water hydraulic components. Computer simulation is very efficient way to get information of the operation of a component and a system before the prototype or the system really exists. Especially in the research of water hydraulic systems simulation is effective, because water hydraulic components are still very expensive. Proportional valves used in water hydraulics are normally ball seat valves, seat valves or spool valves. The latest development is ceramic spool valve, which has a spool made of industrial ceramics. Today the valves are still mainly 2/2-way or 3/2-way valves and the more complex controls must be build by using these basic elements. The control accuracy of the valves can be improved by using electrical position feedback from the control element. In some cases this is also essential for the proper operation of the valve. In this paper the simplified mathematical model for 3/2-way ceramic spool valve is presented and verified. Different control methods for the two-stage throttle valve are examined.

The aim of the work is to develop an on/off valve based trajectory tracking control solution without fast and/or continuous switching of valves. The pulse code modulation method is used to realise stepwise control of inflow and outflow of the actuator. Both inflow and outflow paths have five parallel-connected two-way solenoid valves, each having different flow capacity according to binary series, and a four-way on/off valve is used for changing direction of movement. Cost function based open-loop and closed-loop control solutions are developed and it is demonstrated how the cost function weights can be used to find a reasonable trade-off between tracking performance and pressure surges. Closed-loop results show accurate and reasonably smooth position tracking and simultaneous pressure level control. Achieved control performance is close to that of water hydraulic servo systems.

To carry out a variety of remote handling operations inside the ITER divertor a Water Hydraulic MANipulator (WHMAN) and its control system have been designed and developed at Tampere University of Technology. The manipulator is installed on top of Cassette Multifunctional Mover (CMM) to assist during the cassette removal and installation operations. While CMM is designed to carry heavy components such as cassettes through the service ducts relying on positioning accuracy and repeatability, WHMAN is designed to execute a mix of remote handling operations using position trajectories and master-slave telemanipulation. WHMAN is composed of eight joints: six rotational and two translational. Since a manipulator requires only six joints to acquire the desired position and orientation in operational-space, the two additional joints of WHMAN provide the redundant degrees of mobility. This paper presents how this redundancy of WHMAN can be an advantage to optimize the execution of remote handling tasks. The paper also discusses an effective way to practically exploit the redundancy. The results show that the additional degrees of freedom can be utilized to improve the dynamic behavior of the manipulator.

High system reliability is of utmost importance during the ITER Remote Handling (RH) maintenance operations, as the operational environment is heavily irradiated and populated by fragile and very expensive reactor components and diagnostics equipment. The radiation prevents using live personnel for recovery purposes in the case of equipment malfunction and the fragile environment prevents using brute force to recover malfunctioning equipment. Due to these facts, the concept of Reliability-Centered Maintenance (RCM) for the RH maintenance equipment is exceptionally valid. To improve the RCM concept, probabilistic methods based on the stochastic simulation and reliability mathematics are studied to add a degree of failure prediction. This paper describes the project to improve the reliability of remotely operated Water Hydraulic Manipulator (WHMAN) utilising probabilistic methods. This work was done on an FMECA (Failure Methods, Effects and Criticality Analysis) performed on the WHMAN prior to starting this project. Furthermore, additional considerations regarding maintenance regime derived from the results of this project are presented.

Although the rst water hydraulics applications are already known from 400-500 BC, the rst real modern applications are only known from the end of eighteenth century, as we can see from Figure 16.1. After that, for over one hundred years all hydraulic systems used water as a pressure medium. In the early twentieth century hydraulics came into the picture when pressure medium lubricated pumps and motors and oil-resistant seal materials were developed.

Digital Hydraulics is a recently developed alternative for traditional control with servo or proportional valves. The key principle is to use parallel-connected two-way on/off valves together with intelligent control. This paper studies the energy efficiency of a high inertia cylinder drive. A valve manifold with 4×5 two-way screw-in cartridge valves is used to implement digital hydraulic control of the cylinder. A cost function based control solution is used for online minimization of power losses. Different loading conditions are analyzed and it is shown that the differential connection is essential in reduction of power losses. Switching logic between different flow modes is also studied. Implementation of these ideas requires complex control system. In order to ensure that control system functions as intended, modern techniques for software design and validation (Simulink/Stateflow) are used. The main result of the paper is that energy efficient, cavitation free and high-quality motion control is possible with rather slow response on/off valves. Experimental results with different loads demonstrate 36 percent energy saving in lift-and-lower movements, when compared to traditional load-sensing system.

The energy efficiency of load sensing working hydraulics of mobile machines should be improved. Digital hydraulics is one approach to decrease the losses of cylinder drives and this study concentrates on the design of the control mode selection algorithm for multiactuator system. Measurements are done on a 5-ton wheel loader and the energy consumption of a digital valve system is compared to a traditional load sensing system using simulations.