(Dr. Wayne Book, advisor)
"Internet Based Teleoperation"
he Internet provides a free means of communication for a host of applications ranging from email, web surfing, to live audio and video streaming; eliminating the need for dedicated communication lines and thus reducing costs. The objective of this research is to exploit the Internet as a free source of communication for remotely controlling robotic devices. The challenge of this research is to establish bilateral control of teleoperators over the Internet in a robust fashion with good performance characteristics. Bilateral teleoperation is the ability to remotely control a robot, where contact information (force feedback) is communicated from the slave to the master and thus giving the operator a sense of telepresence. The stability and performance of such a teleoperator is highly dependent on the amount of time delay present in the control loop. This problem is further complicated given the fact that for network based communication the time delay is itself varying and unpredictable.
In this research existing techniques based on passivity (wave variables) and scattering theory are extended to establish Internet based teleoperation, particularly for systems with multiple degrees of freedom (MDOF). In conventional wave-based techniques stability comes at the expense of degrading system performance with increasing time delay. In order to enhance performance, prediction techniques similar to the Smith Predictor and its various modified variations are employed to cut down the lag felt by the user, while simultaneously improving the settling time. The underlying controller is shown to be very robust to model mismatches since passivity is explicitly enforced by an energy regulator.
In an alternative scheme the use of a time forward observer derived from conventional state-space analysis to ensure stability under a varying delay is made. It is shown that the observer is easy to implement and has performance characteristics superior than passivity based formalisms. However the observer is not robust to model mismatches and is unable to reflect remote forces back to the master at steady state conditions while in hard contact.
The two main ideas developed in this thesis were experimentally validated on a 2-degrees of freedom bilateral teleoperator. The loop was closed over the Internet, with the closed-loop distance comparable to the circumference of Earth.