Digital Control Techniques for High Fidelity Haptic Simulation Systems

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Cleveland, Daniel
Haptic , Control , Digital
Haptic simulation systems allow human users to kinesthetically interact with virtual environment models through a robotic mechanism known as a haptic interface. The sampled-data nature of haptic interfaces limits the range of virtual environment dynamics that can be stably rendered in a haptic simulation system which limits the available performance of haptic systems. A method of increasing the range of stably implementable virtual environment dynamics, and the focus of this thesis, is through the investigation of different discrete virtual environment implementations. The passivity and uncoupled stability criteria are considered the most stringent conditions on the stability of haptic simulations systems. In this thesis, seven different discretizations of a spring-damper virtual environment are derived and studied using the passivity and uncoupled stability criteria. Traditionally, position-sampling is the method by which feedback is acquired from a haptic system, however, in this thesis the effects of sampling velocity and that of sampling both position and velocity are studied. As well, a single degree-of-freedom haptic device was developed with analog circuitry to implement velocity-sampled and position and velocity-sampled haptic simulation systems. Results indicate that a zero-order-hold position-sampled implementation may provide a larger range of implementable dynamics than the benchmark, backward difference. It was found that the sampled-PV implementation shows great potential to increase the range of implementable dynamics over existing position-sampled implementations.
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