Sensorless control of motor velocity in two-mass actuator systems with load sensing using extended state observer

Two-mass actuator systems require the motor velocity feedback for stabilizing the controlled motion of load. At this a sensorless control of motor velocity can be both cost- and space-saving and therefore attractive for multiple mechatronic and robotic applications. This paper proposes and evaluates experimentally a sensorless control of the motor velocity based on an extended state observer. The available load-side sensing of two-mass actuator system drives the unknown nonlinear disturbance state. The latter augments the identified fourth-order linear system while assuming zero-order eigendynamics of disturbances. The observed motor velocity is used in a standard feedback loop manner, however without motor sensing. The detailed analysis of dynamics of the estimated states yields the analytic expressions for designing the observer gains. Also the inherent gain boundaries of observer-based feedback control, due to the time delays of the load sensing, are explicitly addressed. The designed and evaluated observer provides a robust feedback control over a large-varying operation range.