Controller for actuation system employing Kalman estimator incorporating effect of system structural stiffness

A controller for use as part of an actuation system including a motor mechanically coupled to a position-controlled element, comprising:

• forward circuitry operative to generate a motor drive control signal as a function of a sum of a position command input signal and a control effort signal, the motor drive control signal controlling a level of power supplied to the motor to cause corresponding motion of the position-controlled element;
• and
• feedback circuitry operative to generate the control effort signal as a function of the motor drive control signal and a measured position signal conveying position information regarding measured position of at least one of the motor and the position-controlled element, the feedback circuitry including:
• a Kalman estimator circuit operative to continually generate a state vector representing an estimate of an operating state of the actuation system, the operating state including position and velocity of the motor, position and velocity of the position-controlled element, and current of the motor, the state vector being generated based on a dynamic model which explicitly includes effects of structural stiffness and damping between the motor and the position-controlled element, the Kalman estimator circuit including (1) a predictor circuit generating a predicted next state based on the state vector and the a control output signal from which the motor drive control signal is derived, and (2) an update circuit updating the state vector based on the predicted next state and the measured position signal;
• and
• a linear quadratic regulator circuit operative to generate the control effort signal by applying a state feedback gain matrix to the state vector, the state feedback gain matrix having a value which minimizes a quadratic cost function representing variance of the control effort signal and/or the measured position signal.