Micromanipulators actuated by micromotors

Abstract

The paper studied micromanipulators actuated by permanent-magnet stepper micromotors. Design concepts to synthesize the bounded control algorithms for micromotors in order to attain the desired performance level (accuracy, robustness, settling time, etc.) are introduced. These brushless micromotors are uniquely suited to be used as servo-actuators in robots due to high torque density, high performance, reliability, cost, etc. Open-loop servos with stepper motors cannot satisfy the requirements imposed on high-performance micromanipulators due to the steps missing feature in the presence of disturbances which results to low accuracy and inability to attenuate disturbances. Therefore, the design of closed-loop systems is an important problem to guarantee the spectrum of the specifications imposed on tracking accuracy, disturbance attenuation, stability in the full operating envelope, robustness to parameter variations, steady-state and dynamic performance, etc. To implement the control algorithms, the angular velocity and rotor displacement must be measured or estimated. The key feature is that robots and actuators are nonlinear dynamic systems. In order to derive the lumped parameter model of manipulators with actuators, the Lagrange equations of motion are used. Using a nonlinear manipulator dynamics, control algorithms are synthesized. This paper outlines a new control a procedure. Using the Lyapunov second method, it is shown that bounded robust controllers can be synthesized using the criteria imposed on the Lyapunov pair. Nonquadratic Lyapunov functions are applied, and nonlinear controllers with nonlinear error and feedback maps are designed. The design technique proposed is feasible and straightforward. An illustrative example is examined in detail to demonstrate the efficiency of the control procedure and effectiveness of the control algorithm designed.