FPGA-based implementation of the back-EMF symmetric-threshold-tracking sensorless commutation method for Brushless DC-machines

Abstract

Abstract-The operation of brushless DC permanent-magnet machines requires information of the rotor position to steer the semiconductor switches of the power-supply module which is commonly referred to as Brushless Commutation. Different sensorless techniques have been proposed to estimate the rotor position using current and voltage measurements of the machine. Detection of the back-electromotive force (EMF) zero-crossing moments is one of the methods most used to achieve sensorless control by predicting the commutation moments. Most of the techniques based on this phenomenon have the inherit disadvantage of an indirect detection of commutation moments. This is the result of the commutation moment occurring 30 electrical degrees after the zero-crossing of the induced back-emf in the unexcited phase. Often, the time difference between the zero crossing of the back-emf and the optimal current commutation is assumed constant. This assumption can be valid for steadystate operation, however a varying time difference should be taken into account during transient operation of the BLDC machine. This uncertainty degrades the performance of the drive during transients. To overcome this problem which improves the performance while keeping the simplicity of the back-emf zero-crossing detection method an enhancement is proposed. The proposed sensorless method operates parameterless in a way it uses none of the brushless dc-machine parameters. In this paper different aspects of experimental implementation of the new method as well as various aspects of the FPGA programming are discussed. Proposed control method is implemented within a Xilinx Spartan 3E XC3S500E board.Index Terms-Permanent-magnet brushless DC-machine (BLDC-machine), back-EMF zero-crossing, sensorless control, field-programmable gate arrays (FPGAs)

Improving the torque generation in self-sensing BLDC drives by shaping the current waveform

“…During speed transients this assumption leads to a degradation of the performance of the drive. The technique proposed in [2] and [3] is employed together with the current reference optimisation.…”

“…The most frequently used self-sensing method for BLDC drives is to detect the back-EMF zero-crossing moments. Examples of the use of zero-crossings detection can be found in [2], [3] and [4].…”

Real time simulation of sensorless control based on back-EMF of PMSM on RT-Lab/ARTEMIS real-time digital simulator

“…Sensorless vector control scheme is successfully implemented if the the accuracy of the estimation of the rotor position is good. This algorithm is implemented by fundamental excitation method and the position of the rotor is detected from the back electromotive force (back EMF) [22,23].…”

Real-time frequency tracking for induction motor drives using LabVIEW FPGA

“…Real-time spectral search based velocity estimation is reported in [1][2][3][4] at estimation window durations ranging from ≈142.8 to ≈333.3 milliseconds, with some of the employed techniques using overlapping windows to increase the attainable estimation rate. FPGA application of real-time positon and speed estimation techniques that are non-spectral search based has been examined recently [7][8] to evaluate the execution speed benefits provided by FPGA implementation.…”