Ph.D. Proposal Presentation by Matthew Kontz
Monday, March 28, 2005
(Dr. Wayne Book, Chair)
"Haptic Control of Hydraulic Machinery using Proportional Valves"
Applying haptic or force feedback to hydraulic machinery such as excavators has the potential to increase operator capabilities. Haptic robotic human-machine-interfaces enable several enhancing features including: coordinated motion control and programmable haptic feedback. Coordinated or resolved motion control supplies a more intuitive means of specifying the equipment's motion. Haptic feedback can be used to relay meaningful information back to the user in the form of force signals. This adds to the cost of the product by increasing the number of sensors, the required computing power and the complexity of the human-machine-interface. In order to make this technology economically viable, the benefits must offset the additional cost associated with implementation.
One way to offset this cost is to not use high-end hydraulic components. The tractor mounted backhoe used in this research uses low-end components including: a constant displacement pump, proportional valves and pressure sensor based force estimation. All of these items tend to limit system performance. Characteristics that limit the performance of the system include: valve spool bandwidth, valve dead-band, delay and noisy force estimation from pressure sensors. Stability is also an issue. An advanced haptic control technique, similar to ones used to deal with time-delayed teleoperation, will be used to maintain stability during haptic teleoperation. Modeling and control of the real test-bed will then be used to develop a virtual excavator for human-in-the-loop testing. Using a virtual model for human testing is desirable from a safety point of view and allows for key parameters to be varied instantaneously. This tool will be used to measure the enhancement in operator control and evaluate the limitations due to system characteristics such as valve dead-band and bandwidth. Use of this virtual excavator will be designed to enhance testing on the real machinery rather than replace it. Not only will the virtual simulator be modeled after HEnRE, but the control algorithm used in the simulator will be tested on the actual hardware. The end-goal of this project is to incorporate haptic control algorithms that work on low-cost systems and maximize the enhancement of operator capabilities.