Tapio Virvalo

Hardware-in-the-loop environment for servo system controller design, tuning and testing

Abstract The paper analyses the possibility to replace the hydraulic and mechanical parts of a hydraulic position servo with a real-time simulation model. The aim is to test the controller hardware against the simulation model that includes the dynamics of the servo system as well as the feedback sensors and amplifier card. The requirements caused by this hardware-in-the-loop (HIL) approach are analyzed. A special attention is paid to the correct modeling of incremental encoders that are widely used as a feedback sensor. Experimental results show that there is no remarkable difference between the responses of the real system and HIL model and so the HIL model can replace the real system.

Energy-efficient motion control of a hydraulic manipulator

In this paper a novel hydraulic closed-loop motion control system has been proposed, designed and implemented on a heavy-duty 2-DOF hydraulic manipulator. A new unconventional hydraulic drive is introduced to remove the complex nonlinear interconnection between cylinder pressure levels, supply pressure and load force. The remaining nonlinear coupling of force and velocity is then removed by nonlinear controller design. New hardware combined with this proposed controller design is able to improve the controllability of the load with lower supply pressure values than conventional controllers. This leads to improved energy efficiency and is therefore of great practical and economic importance. This is a significant result since energy efficiency of closed-loop controlled hydraulics is generally known to be very low and improvements very difficult to obtain.

Development of fuzzy state controller and its application to a hydraulic position servo

Abstract By combining control theory and fuzzy set theory, a new kind of state controller is proposed. Full order feedback and membership functions, which utilize the experience of experts, are used in the design of the state controller which we call a fuzzy state controller. Hydraulic position servos with a nonsymmetrical cylinder are commonly used in industry. This kind of system is nonlinear in nature and generally difficult to control. For different ending position, moving direction, strokes, and load the system dynamics is totally different. Once the above-mentioned parameters of the system are known, it is relatively straightforward to tune the gains of state controller to obtain good dynamic response. But when these parameters change, especially in case of the load, using the same gains will cause overshoot or even loss of system stability. Adaptive control is not applicable in this case due to the complexity of the algorithm, its rate of convergence, and the fast response characteristic of the system. The fuzzy state controller has been successfully applied to a hydraulic position servo. The system shows excellent robustness against variations of system parameters.

The hierarchy of communication networks in the programmable assembly cell: an experimental framework

The concept of the programmable assembly cell is introduced. The idea of the distribution is adopted at machine level, and the use of independent intelligent actuators is described. The novel types of communication problems caused by this high-level distribution are examined. A hierarchical communication subsystem consisting of in-cell and in-machine communication networks is presented as a solution. Laboratory equipment built to study these problems is described.<<ETX>>

Distributed motion control in hydraulics and pneumatics

Abstract Motion control systems are also coming into common use in hydraulics and pneumatics. There are still some problems to be solved. System characteristics in hydraulics, and especially in pneumatics differ, quite extensively from those in electromechanical systems. A new idea in motion control applications is distributed control. In this paper, the motion control, its problems and possible solutions in hydraulics and pneumatics, including distributed motion control, are discussed.

The distributed control system - A world of new possibilities

Abstract Distributed control of machine automation is one of the main research areas of the Institute of Hydraulics and Automation at Tampere University of Technology in Finland. In this paper, the idea of distributed control is discussed. As a closely related subject, technological aspects of independent actuators and in-machine communication are presented. Transmission delays of in-machine communication are discussed as a possible application dependent source of problems. In the Conclusions, the further studies are also presented.

Developing intelligent actuator systems: experimenting with Bitbus and the 8096

Abstract The paper discusses the concept of a programmable mechatronic actuator system and gives system requirements. A distributed intelligent independent actuator (IIA) system is presented as a flexible solution to the growing need for better performance and distribution. The processing and communication capabilities of the IIA units and the IIA developing system concept are discussed in detail.

New solution of motion control problem in mechatronic system

Abstract Distributed motion control in machine automation is one of the main research areas of Institute of Hydraulics and Automation in Tampere University of Technology in Finland. In this paper the idea of an independent actuator as a mechatronic solution to motion control problem is discussed. As a closely related subject technological aspects of system control and in-machine communication are shortly presented. Connection methods are presented for some alternative machine controllers, like PLC, CNC and PC. Transmission delays of in-machine communication are discussed as a possible application dependent source of problems. In the conclusion chapter the further studies are also presented.

In-machine communication-a general solution for interconnecting independent intelligent actuators

The independent intelligent actuator is a new building block at the lowest level of manufacturing automation. To facilitate the combination of these actuators to form machines, a fast and economical communication method should be developed. In-machine communication is therefore discussed along with the demands made on it. It is shown that real-time and very reliable operation is needed. A practical solution based on the commercial Bitbus interconnection is then examined. Results show that the implementation is also acceptable for fast manipulators with path-control capability.<<ETX>>

ITER Divertor Maintenance: Development of a Control System for the Remote Handling of the Divertor Cassette Mover

Remote handling devices are being used to carry out the maintenance tasks in the divertor area of the ITER. One of the main challenging operations is the installation and transportation of Divertor Cassettes in and out from the vessel. This paper deals with the development of the control system for such remotely operated devices, with special emphasis on the tools, mock-ups and virtual prototypes employed to develop the high level control software and the water-hydraulics position servos controllers. Preliminary studies showing the effect of irradiation in hydraulic cylinder seals are also presented.