In this paper we show how three-dimensional virtual reality models can be used in teaching the structures and functions of hydraulic components. This technique allowed the teacher to show exactly how a slide moved inside a valve and how it affected on the opening of flow orifices thus increasing or decreasing the flow. Students were taken on a tour inside components to examine the critical points in component behaviour. The use of virtual reality benefits the students in learning hydraulic phenomenon faster and more accurately. In this paper the techniques and use of virtual reality system in teaching and research are presented.

The goal of the paper is to study the properties of a teleoperated mobile machine and produce a simulation model of the machine for later use. In this paper there are introduced a prototype of the teleoperated mobile machine and a simulation model of that machine. The challenge in teleoperation is to have a smooth and accurate control of the machine, because the operator can not feel any force. The machine is valve controlled and because of that the influence of different type of valves can be significant for the control of the machine. By means of the simulation model it is possible to test new components and hydraulic solutions for power transmission of mobile machine. The new computer controlled prototype of the teleoperated mobile machine is electrically controlled with proportional valves has been developed. The simulation model of the machine is verified with the measurements. The goal is that the main properties of computer controlled and teleoperated mobile machine are at least at the same level than in normal mechanically controlled machine, but controllability must be better because of the teleoperation. In this paper there is also introduced the principle of the automatic virtual gearbox. The prototype is equipped with two constant displacement pumps, electrically controlled pressure relief valve and supply pressure and LS pressure sensor. Therefore the information of load pressure is available and supply pressure can be controlled with the rotational speed of diesel engine and pressure relief valve. In teleoperated mobile machine the rotational speed of diesel engine is controlled with electric gas. With these components and a computer control it is possible to set supply pressure level according to the needed load pressure level.

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Abstract-Attachments and their controls can be connected to hydraulic mobile machines in different ways. The traditional approach is to install hydraulic valves of the attachment close to the operator. Thereby levers of the valves can be reached from the operator seat. This, however, restricts the size and number of the valves and can be inconvenient for the operator. A more advanced and ergonomic way is to use electronic control which allows installing the valves more freely on the attachment. The operator can then control the attachment with a joystick, for example. Usually there is a microcontroller unit in an electronically controlled mobile machine. One solution is to use this unit to read the joysticks and output control signals to the valves of the attachment. However, if there is a microcontroller in the attachment as well, the wiring can be minimized and the attachment can perform intelligent functions, for example positioning, as the machine sends simple commands. The data transfer between the microcontrollers can be realized flexibly and reliably using a serial bus such as CAN.A hydraulically operated excavator for a hydraulic mobile machine is discussed as an example. The excavator has four PWM controlled spools in a sandwich type proportional mobile valve. A suitable microcontroller is chosen to interface the valves of the excavator to the CAN bus of the mobile machine. Different command sets and levels of intelligence are deliberated. Adding different types of sensors to the excavator is concerned. The sensors are used to achieve more accurate, independent and safe operation. The microcontroller unit is designed to have extra interfaces for future research with different sensors. The unit is designed, built and installed to the excavator. The design of electronics and software is presented in this paper. The excavator is attached to the hydraulically operated mobile machine and the performance of the system is tested. The test arrangement is described. The results are presented and discussed. IndexTerms-CAN, intelligence, mobile machine, proportional valve. O. I. Karhu is with the Institute

A small general-purpose teleoperated hydraulic mobile machine is studied at the Institute of Hydraulics and Automation at the Tampere University of Technology. Thanks to teleoperation, the operator of the machine is able to be in safe place during the driving when necessary. However, the actions of the machine can be dangerous for the people or the objects in the environment if problems appear for instance in the control system. On that account, safety issues must be considered carefully. Special attention has to be paid to stop the machine and start the engine again once the machine has recovered from an error situation. The goal of this paper is to describe the design and implementation of different kind of solutions to start and stop the machine wirelessly. The emergency stop can be activated through the wireless connection by the operator or by the automatic diagnostic system of the hydraulic mobile machine. The control system monitors the state of several hydraulic components such as hydraulic valves and motors by means of sensors during the operations of machine. The machine is teleoperated by using WLAN (Wireless Local Area Network) connection. The developed wireless starting system and emergency stop is totally independent of the WLAN link. In the first prototype of the wireless starting system and emergency stop, the wireless connection is carried out by using commercial, cost effective RF (Radio Frequency) modules. The data transfer protocol which is used by the modules is designed for this application. Protocol implementation is carried out with microcontrollers. Another version of the wireless starting system and emergency stop is carried out by using radio modems. The modems have better properties than the cost effective RF modules used in the first prototype due to their higher RF output power. Programmatically carried out automatic emergency stop, which stops the machine, if the WLAN connection between the control station and the machine breaks, is discussed. In that case, the independent wireless emergency stop connection is not needed. Implementations of the system are introduced in this paper. Also, some testing results and user experiences are described. Properties of these different implementations are compared: cost of the system, range, reliability and complexity of the implementation. By means of the studied results the most suitable solution to start the engine and stop the actions of the machine is chosen.