EE 628 Force Control and Bilateral Teleoperation

This course is designed to equip students with fundamental theories and computational methodologies that are used in (computer aided) analysis and synthesis of force controlled and bilaterally teleoperated systems. By the end of the course a solid understanding of the principles of force/bilateral control in the context of modern classical control and hands on experience with implementation of force/bilateral controllers on modern force feedback devices are aimed. The course is appropriate for students in any engineering discipline with interests in robotics, nonlinear controls, and haptics.

After a short review of MIMO classical control techniques, fundamental limitations of feedback control, and feedback linearization, students will be introduced to the challenges of explicit force control. Alternatives to explicit force control, such as implicit force control, impedance control, and admittance control will be studied. Theory and implementation of reaction force observers and sensor fusion techniques will be exercised. Robust stability and transperancy of general [scaled] teleoperation architecture (4-channel with local force feedback) will be studied in detail and the tradeoff between these two competing criteria will be demonstrated. Fundamentals of virtual environment simulation and haptics rendering will be covered, emphasizing the destabilizing effects of energy leaks introduced due to sampled data effects. Controllers to ensure passivity of the human-in-the-loop sampled data system will be synthesized. Finally, communication/computation delays will be introduced and two approaches to compensate for the time delay, namely, time domain passivity and wave variables, will be illustrated.

The emphasis of this course is not on the excessive mathematical abstraction but rather on an integrated understanding of mechanical design, physical modeling, stability analysis, controller synthesis, and hardware-in-the-loop implementation of force/bilateral control systems. Special attention is paid to the decisions made in the mechanical design process, since closed loop performance of the overall system is directly affected, and in many cases limited, by the physical characteristics of the plant. An intuitive understanding of major nonlinear system analysis tools, such as Lyapunov stability and passivity, is sought, since a solid understanding of concepts help students better appreciate the reasoning behind physical system modeling and controller synthesis. Real-time hardware-in-the-loop implementation of the controllers is also emphasized such that students can experience the control challenges of the real world, such as sensor noise and unmodeled system dynamics.

Primary application areas of force feedback devices (haptic interfaces) and bilateral teleoperators include (but are not limited to) rehabilitation and manual task training (including flight and surgery training). Bilateral teleoperators are also commonly employed as human-machine interfaces for micro/nano manipulators. Addition of force feedback to these interfaces improve sense of immersion in virtual environments and render virtual assistance as well as human capability enhancements possible. “X-by-wire” type concepts are other motivating applications where traditional direct mechanical controllers are replaced by their enhanced electronic implementations.