Control of Electrical Drives with Elastic Transmission, Friction, and Backlash

Controlled electrical drives needs to satisfy high requirements on their static and dynamic behavior. From the standpoint of control, imperfections of the electrical drive transmission are manifested in occurrence of compliance, friction, and backlash. Negative influence of these effects on the controlled drive performance can be reduced by extending the classical cascade structure of electrical drive control with appropriate compensation algorithms.

The influence of the transmission compliance can be compensated by applying a state speed controller instead of the traditional PI speed controller. Different types of the state controller have been designed and compared. These are full-order or reduced-order state controller, polynomial controller of the motor or load speed, and a controller based on inner acceleration loop. The superimposed position controller is of proportional type. A full-order or reduced-order feedforward controller has been designed for a tracking system.

Different types of friction compensator have been designed and compared. These are a friction compensator based on the static Karnopp friction model, a compensator based on a Dahl dynamic friction model, gain scheduling-based compensator, and a compensator based on the inner acceleration loop. A fuzzy logic-based backlash compensator has also been considered.

The developed control strategies have been examined on an experimental setup of a controlled electrical drive with the capability of independent adjustment of the load torque, inertia ratio, transmission stiffness, friction, and backlash.