Dimitris Hristu
Division of Engineering & Applied Sciences
Harvard University

Motion Control with Limited Communication

Control and communication issues are traditionally decoupled in discussions of decision and control problems because this simplifies the analysis and generally works well for classical models. This fundamental assumption deserves re-examination as control applications spread into areas where lack of time on a network shared by sensors, actuators and the controller is as important as lack of computational power. Such areas include the coordinated control of robots, aerial vehicles (UAVs), MEMS devices and other settings, where many systems must share the attention of a decision-maker. An example of such a system is the HRL planar manipulator. The manipulator includes 2-DOF fingers, tactile sensors and a visual tracking system, all controlled from a centralized computer. Because the communication bus connecting the controller to the manipulator has limited capacity:
* Communication with the controller occurs at discrete times
* The controller must choose which actuators/sensors to update/read at a particular time.
These constraints lead to the need for a theory of sampled-data systems where communication and control are intrinsically coupled. In this talk, I will outline such a theory and use it to solve tracking and stabilization problems as well as to quantify "attention" in the context of control systems with limited communication. I will discuss applications of the theory to trajectory tracking problems involving the HRL manipulator and present results showing typical performance improvements that can be achieved in manipulation experiments.