Speed measurement algorithms for low-resolution incremental encoder equipped drives: a comparative analysis

Abstract

Precise motion control requires high-accuracy and highbandwidth feedback speed information, often calculated by direct measurement of the rotor position available through the incremental encoder equipping the drive. The resolution of the encoder heavily affects the cost of the drive and the accuracy and bandwidth of the calculated speed. The limitations introduced by a low resolution encoder can be partially reduced by a proper speed calculation (or estimation) algorithm, that therefore plays a key role in modern drive systems. In this paper a comparative analysis of state-of-art speed measurement and estimation algorithms suitable for low-resolution incremental encoder equipped drives is presented, aiming at highlighting the specific feature of each one, both from the performance point of view, and from the computational requirements needed for actual implementation. The paper proposes itself as a guide for engineers in the complex choice of the best solution for each application.

Implementación en DSPIC de un algoritmo óptimo para la estimación de velocidad de giro<br />Implementation of an optimal algorithm for the estimation of angular speed in DSPICS

“…2, donde la parte superior presenta el resultado del método, mientras la de abajo presenta el error relativo, se observa que el error no supera el 15%, el cual se presenta a velocidades altas. La tendencia del error es a aumentar conforme la velocidad aumenta, según se espera teóricamente, como se afirma en [13]. …”

Simulation of MRAC based speed control of brushless DC motor with low-resolution hall-effect sensors

“…1 [15]. Because the rotor of a BLDC motor is permanent magnet, the back EMFs are proportional to the electric speed of the rotor e a =-e b = k e r (5) where ke is back EMF coefficient and is a constant. According to (4) and (5) …”

“…All the observer-based methods share the feature of providing high accuracy of the speed estimation with satisfactory dynamic performance. But they suffer from the dependence on system parameters and need heavy computation [5]. A model free enhanced differentiator is proposed for improving velocity estimation at low speed [6], [7].…”

Automatic tracking of MTPA trajectory in IPM motor drives based on AC current injection

“…In order to get a better speed feedback, a moving average processing of the position samples (e.g. encoder pulses when incremental encoder is adopted) can be implemented or by means of more accurate algorithms [6] [7]. For this reason a low frequency injected current perturbation (i.e.…”