High-performance manipulators and the application of high torque density actuator technology: nonlinear analysis, robust design, and deployment of high-precision robots

Direct-drive actuators are used in high-performance robots. For directly actuated robots and servos, the paper develops a design concept to solve the motion control problem using nonlinear models. The Lagrange equations of motion are used to integrate torsional-mechanical and circuitry dynamics with the corresponding energy conversion and torque production analysis. The derived nonlinear models are applied in analysis and design. Due to open-loop instability and control bounds imposed, parameter variations and unmodeled dynamics, we apply the modified Hamilton-Jacobi theory to synthesize the bounded robust controllers. The admissibility concept is used to perform the analysis of stability needed to solve the motion control problem. By minimizing the nonquadratic performance cost and making use of necessary conditions for optimality, a bounded control law is designed. The sufficient conditions for stability are derived and examined based upon Lyapunov stability theory. Robustness of the resulting closed-loop system with the synthesized controller is studied. The results are verified for a directly actuated robot, and a nonlinear controller is designed, implemented, and thoroughly examined.