Determining the Position of the Brushless DC Motor Rotor

Abstract

In brushless direct current (or BLDC) motors with more than one pole pair, the status of standard shaft position sensors assumes the same distribution several times for its full mechanical rotation. As a result, a simple analysis of the signals reflecting their state does not allow any determination of the mechanical position of the shaft of such a machine. This paper presents a new method for determining the mechanical position of a BLDC motor rotor with a number of pole pairs greater than one. In contrast to the methods used so far, it allows us to determine the mechanical position using only the standard position sensors in which most BLDC motors are equipped. The paper describes a method of determining the mechanical position of the rotor by analyzing the distribution of errors resulting from the accuracy proposed by the BLDC motor’s Hall sensor system. Imprecise indications of the rotor position, resulting from the limited accuracy of the production process, offer a possibility of an indirect determination of the rotor’s angular position of such a machine.

Influence of the Placement Accuracy of the Brushless DC Motor Hall Sensor on Inverter Transistor Losses

“…Based on the conducted research, we can conclude that small inaccuracies of sensor placement <2.5 • are acceptable and do not cause significant asymmetry of the motor phase currents. In the case of larger inaccuracies (which is a typical problem in low-power BLDC motors [6]), it is necessary to take this fact into account when selecting inverter elements. A good solution may be the use of advanced software methods in sensor placement error correction.…”

“…This procedure is relatively simple for motors with one pair of poles, or when the rotating magnet on the motor shaft is made perfectly symmetrically. However, the asymmetry of the magnet, which is a common phenomenon [6], causes the intervals between successive commutation points of transistors for multipole motors to be different, despite the same state of the Hall sensors. This significantly complicates the process of calculating the commutation errors and assigning them to individual sectors of the winding operation.…”

Machine Learning for Sensorless Temperature Estimation of a BLDC Motor

“…The BLDC motor was equipped with two analog LM35DZ temperature sensors supported by the Texas Instruments (Dallas, TX, USA), one of which was mounted to the winding ends with a thermally conductive adhesive, as shown in Figure 2 , while the other was placed on the motor casing— Figure 3 . The control of the tested motor was carried out with the use of the algorithm described in [ 35 , 36 ] to eliminate the possible impact of Hall sensors’ misalignment on the effectiveness of the estimation. The IHM08M1 system, dedicated to work with STM32 series microprocessors supported by the STMicroelectronics N.V. (Amsterdam, The Netherland), was used as the power electronic converter.…”

Improving the Angular Velocity Measured with a Low-Cost Magnetic Rotary Encoder Attached to a Brushed DC Motor by Compensating Magnet and Hall-Effect Sensor Misalignments

“…This method determines the degree of misalignment of the internal Hall-effect sensors and proposes a corrective ratio to reduce the effect of this misalignment in the estimation of the angular rotational velocity of on a two pole BLDC motor. On the other side, this paper is also inspired in the contribution of Kolano et al [ 13 ] that proposes a method for determining the mechanical position of the shaft of a BLDC with more than one pole pair. This method is based on the analysis of the distribution of the errors obtained when measuring the angular rotational velocity with the internal Hall-effect sensors relative to an external encoder in an open loop drive system.…”