Hemant Melkote

Modeling and adaptive nonlinear control of electric motors

1 Introduction.- 2 Dual-Axis Linear Stepper (Sawyer) Motors.- 3 Modeling of Stepper Motors.- 4 Stepping.- 5 Feedback Linearization and Application to Electric Motors.- 6 Robust Adaptive Control of a Class of Nonlinear Systems.- 7 Robust Adaptive Control of Stepper Motors.- 8 Current Control of Stepper Motors Using Position Measurements Only.- 9 Voltage Control of Stepper Motors Using Position and VelocityMeasurements.- 10 Voltage Control of PM Stepper Motors Using Position Measurement Only.- 11 Brushless DC Motors.- 12 Induction Motor: Modeling and Control.- 13 Adaptive Control of Induction Motors.- 14 Passivity-Based Control of Electric Motors.- 15 Torque Ripple Reduction for Step Motors.- 16 Friction Compensation in Servo-Drives.- A Fundamentals of AC Machines.- B.1 Case of Position-Only Dependent Transformations.- C Torque Maximization with Current and Voltage Constraints (Field Weakening).- C.1 Low-Speed Range.- C.2 High-Speed Range.- C.3 Intermediate-Speed Range.- C.4 Transition Speeds.- D Stable System Inversion.- E Lyapunov Stability Theorems.- F Backstepping.- G Input-to-State Stability and Nonlinear Small Gain.

Nonlinear adaptive control of direct-drive brushless DC motors and applications to robotic manipulators

Robust adaptive nonlinear control of brushless DC (BLDC) motors is considered. A controller is designed for the plant that is robust to parametric and dynamic uncertainties in the entire electromechanical system. These uncertainties are shown to be bounded by polynomials in the states. In addition, the controller can reject any bounded unmeasurable disturbances entering the system. A model for the motor incorporating magnetic saturation is used to design voltage-level control inputs for the motor. The design methodology is based on our earlier work on adaptive control of nonlinear systems. The overall stability of the system is shown using Lyapunov techniques. The tracking error is shown to be globally uniformly bounded. The design procedure is shown to be also applicable to multilink manipulators actuated by BLDC motors. The performance of the controller is verified through simulations and comparisons with a proportional-integral-derivative-type controller are made.

Robust adaptive control of variable reluctance stepper motors

Robust adaptive nonlinear control of variable reluctance motors is considered. Utilizing a model for the motor that incorporates magnetic saturation, an adaptive controller is designed for the plant that is robust to parametric and dynamic uncertainties in the entire electromechanical system. A robust torque profile is first designed for the motor. Thereafter, a commutation strategy is applied to define desired currents that would produce the desired torque signals. The desired currents then become the tracking objective for the electrical subsystem. Voltage level control inputs are designed using backstepping and the robust control design methodology to track the desired currents. The overall stability of the system is shown using Lyapunov techniques. The tracking error is shown to be globally uniformly bounded. The control design is shown to be applicable to other motor models wherein the flux linkage is modeled as separable products of functions of the rotor position and winding currents. Simulation results are illustrated to show the performance of the controller.

Advanced control system design for high speed ultra accurate manufacturing systems

In this paper we describe the application of a robust adaptive control design to an ultra accurate (sub-micron) linear and planar step motor known as the Sawyer motor (1969). Simulation results presented show promising improvement in performance with the advocated controller.

Closed-loop control of a base XY stage with rotational degree-of-freedom for a high-speed ultra-accurate manufacturing system

Modeling and control of a high-speed ultra-accurate XY stage used in manufacturing systems is considered in this paper. The base XY stage is a two dimensional linear stepper (Sawyer) motor including a rotational (yaw) degree-of-freedom. Manufacturing systems based on Sawyer motors are widely used in wafer probing applications and in automated assembly. A Sawyer sensor is being integrated for measuring the motors position, velocity and yaw rotation for closed-loop control purposes on our testbed at the CRRL. Utilizing results on robust control of nonlinear systems, an adaptive current-level controller is designed for the motor that renders the closed-loop system robust to a variety of uncertainties and disturbances. A detailed model of the motor that takes into account the significant uncertainties of the motor is used in the control design. The tracking error is shown to asymptotically converge to the origin. Simulation studies are presented to validate the controller performance.

Nonlinear output feedback control for stepper motors: a robust adaptive approach

Nonlinear adaptive output feedback control of stepper motors is considered. Utilizing the phase currents as inputs, an adaptive controller is derived for permanent magnet and variable reluctance stepper motors that achieves robustness to parametric and dynamic uncertainties, such as friction, load torque or cogging torque in the motor dynamics. The controller utilizes only the rotor position for feedback and achieves global uniform boundedness of the tracking error. The design methodology is based on our earlier work (1997) on robust adaptive control of nonlinear systems. The stability of the system is proved through Lyapunov techniques. Simulation results are depicted to illustrate the performance of the controller.

Closed-loop control of a three degree-of-freedom ultra accurate linear stepper motor

In this paper, we present a robust adaptive control system designed for three degree-of-freedom linear motion ultra accurate (Sawyer) stepper motors. Such motors are commonly used in the semiconductor industry for wafer-probing and in automated assembly. A detailed model of the motor is developed. A controller is designed for the motor that is robust to parametric uncertainties in the model and achieves good tracking performance in the presence of disturbances while compensating for the undesirable effects of yaw rotation of the motor in the platen plane. The proposed current level controller utilizes all the states for feedback. The stability of the closed-loop system is shown using Lyapunov techniques. The tracking errors are shown to be globally uniformly bounded. Simulation studies are carried out to show the efficacy of the proposed control design methodology.

Output feedback control of a three degree-of-freedom linear stepper motor with position measurements only

In this paper, an adaptive current-level controller is designed for two-dimensional linear stepper motors that renders the closed-loop system robust to a variety of uncertainties and disturbances prevalent in the motor dynamics. The controller uses only the motor position and the yaw angle for feedback. The tracking error is shown to be globally uniformly bounded. Simulation studies are presented to validate the controller performance.

Adaptive variable structure torque ripple cancellation for permanent magnet stepper motors

Torque ripple compensation for permanent magnet stepper motors is considered. The control design methodology is based on our earlier work on adaptive variable structure control (1997). A current-level controller is derived for a detailed model of the motor which achieves asymptotic tracking of a reference trajectory while compensating for uncertainties in the mechanical dynamics of the motor. The proposed robust nonlinear controller requires the use of only one adaptation parameter. The control design methodology is of variable structure type with a smooth control action. Simulation results for position and for constant velocity tracking show the efficacy of the proposed control design.

A unified approach to adaptive nonlinear control of stepper motors

In this paper, a robust adaptive nonlinear controller for various types of stepper motors is presented. The control design is applicable to both variable reluctance and permanent magnet stepper motors. It is also shown that the methodology is applicable to other peculiar configurations of stepper motors (e.g. Sawyer motors). Furthermore, the motors may be either rotary or linear. To this end, a general electromechanical model of stepper motors is utilized. The model is comprised of the mechanical dynamics and electrical dynamics of the motor including the effects of cogging, viscous friction, winding resistance or other uncertainties. The robust adaptive design is based on our earlier work (1997) and does utilizes backstepping in the case that voltage level control is used rather than current controls. Simulation studies are presented to show the efficacy of the control design approach.