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Improved Control of Open-Center Systems for Haptic Applications

[+] Author Affiliations
M. E. Kontz, J. D. Huggins, W. J. Book

Georgia Institute of Technology

J. G. Frankel

Electro-Scientific Industries, Inc.

Paper No. IMECE2005-81910, pp. 823-831; 9 pages
  • ASME 2005 International Mechanical Engineering Congress and Exposition
  • Dynamic Systems and Control, Parts A and B
  • Orlando, Florida, USA, November 5 – 11, 2005
  • Conference Sponsors: Dynamic Systems and Control Division
  • ISBN: 0-7918-4216-9 | eISBN: 0-7918-3769-6
  • Copyright © 2005 by ASME


The use of haptic interfaces to control mobile hydraulic machinery has several enhancing features over traditional human-machine-interfaces compromising of joysticks/levers. A prohibitive attribute of these systems is cost due to added complexity. One way to limit this cost is to use lower cost hydraulic components such as a constant displacement pumps and proportional directional control valves. In this type of system, a main pressure regulator is needed to supply the other closed-center valves with pressure and dump the additional flow from the pump to tank. An energy-saving solution has a load-sensing pressure regulator that maintains the system pressure a preset margin above the highest active load pressure. With the addition of pressure compensators on each proportional valve, these valves can provide steady-state flow proportional to an input voltage generated from a joystick. Using these valves for haptic applications requires closed-loop control. Applying closed-loop control to these valves can excite instabilities in the valve assembly due to complex interactions and nonlinearities in the load-sensing pressure regulator. This paper describes and analyzes these interactions. It also shows through experimental examples of how these characteristics limit closed-loop performance and destabilize the system. A possible valve modification is presented and closed-loop performance is compared using the original and modified system.

Copyright © 2005 by ASME
Topics: Haptics



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