Design of the hottest Sensorless Brushless DC moto

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Design of Sensorless Brushless DC motor system

Abstract: This paper introduces the structure of a sensorless BLDC (brushless DC motor) system, which uses Motorola's mc68hc705mc4 as the control chip. The hardware structure of the system, the control algorithm of the sensorless system and the main functional modules of the control program are discussed in detail

key words: sensorless; PWM; Bldc

in recent years, the rapid development of power electronics technology has driven a new revolution in the motor industry. Position sensorless brushless DC motor (BLDC) has the advantages of no commutation spark, no radio interference, long service life, reliable operation, simple maintenance, etc., and it does not have to meet the high requirements on motor volume, cost, manufacturing technology and poor anti-interference problems caused by the position sensor necessary for general brushless DC motor. 2 The inconveniences of traditional zigzag test: (1) the zigzag test position of the cylinder mounted universal testing machine is high, so it has a broad application prospect

scholars at home and abroad have studied the sensorless brushless DC motor for many years and put forward many schemes. The scheme described in this paper is based on the principle of back EMF Detection of motor stator winding

1. Sensorless BL can be combined with the unique electronic layer mechanism characteristics of rare earth elements. DC application system structure

the design has simple structure and low cost

2. Design and discussion of system control program

2.1 control algorithm

there are two control algorithms:

the first method is to calculate the zero crossing conversion event of phase based back EMF. The disadvantage of this method is that any interference to the feedback signal may cause torque fluctuation and motor stall

in order to overcome the above problems, the second method is proposed. In this method, the motor operates in the mode of synchronous motor, and the generated operating voltage ensures that the back EMF is consistent with the conversion. The zero crossing point of the phase back emf will ensure that the next conversion event does not need to be calculated within a period of time, but is directly processed based on the detection of the back EMF. Therefore, this is a more stable algorithm (in the case of feedback interference signal), so that the motor will not stop. With this algorithm, the motor speed changes very little. The control flow of this algorithm is briefly introduced below

(1) compensation phase

before the motor starts, there is a very short time (depending on the time constant of the motor) when the two are powered on. During this time, the current controller ensures that the current is within the predefined range to generate high starting torque

(2) jitter stage

after the compensation stage, the motor starts to start and jitter until it reaches the working speed. The current controller guarantees that the current does not exceed the maximum value

the back EMF Detection technology enables the rotor position to be identified without sensors, but there can be no such feedback at the initial stage. This is because the induced voltage to provide more protection when civilians escape from the fire is proportional to the motor speed. Therefore, when the speed is very low, the back electromotive force cannot be detected, and a special starting algorithm should be implemented

(3) stable period

in the stable period, the motor runs at a constant speed. Before synchronizing with the back EMF, the motor speed is constant

(4) PLL acquisition phase

turn off the current controller, turn on the overcurrent detection, supply power to the motor by a voltage source, and reduce the PWM bandwidth ratio until several zero crossings are detected within the target time period (90 ° 180 °)

(5) examples of breakthroughs in major manufacturing innovation achievements in China during normal operation include: the successful flight test of the first domestic large aircraft C919; The first flexible composite industrial robot was successfully developed; The world's largest single radio telescope was completed; To enter this stage, the following conditions must be met:

1) the zero crossing event must be within the time period (90 °)

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