Brushless dc motor is on the basis of a brush dc motor development, has the infinite speed regulation, wide speed range, overload ability, good linearity and long service life, the advantages of small volume, light weight, large output, solved with a series of problems of the brush motor, widely used in industrial equipment, instruments and meters, household appliances, robotics, medical equipment and other fields. Because of brushless motor without brush for automatic reversing, so you need to use electronic commutator for reversing. Brushless dc motor drive is the function of the electronic commutator. Brushless dc motor is on the basis of a brush dc motor development, has the infinite speed regulation, wide speed range, overload ability, good linearity and long service life, the advantages of small volume, light weight, large output, solved with a series of problems of the brush motor, widely used in industrial equipment, instruments and meters, household appliances, robotics, medical equipment and other fields. Because of brushless motor without brush for automatic reversing, so you need to use electronic commutator for reversing. Brushless dc motor drive is the function of the electronic commutator. At present, the mainstream of the brushless dc motor control mode is: FOC (Also known as the vector variable frequency, magnetic field vector oriented control), square wave to control (Also known as the trapezoidal wave control step, ° control, reversing control)And sine wave control. So what this control method has its advantages and disadvantages? Square wave to control the square wave control using hall sensor or non-inductive estimate algorithm to obtain the position of the motor rotor, then according to the position of the rotor in ° electrical cycle, for reversing (Every ° reversing)。 Each position reversing motor output power in a certain direction, therefore the position of the square wave to control precision is electrical °. Under control because in this way, the motor phase current waveform close to square wave, so called the square wave control. Square wave control mode, control algorithm of the method is simple, low hardware cost, using ordinary performance controller can obtain high motor speed; The disadvantage is that large torque ripple, there is a current noise, can not reach the maximum efficiency. Square wave control is suitable for the occasion of motor rotation performance requirements is not high. Sine wave control sine wave control mode is used SVPWM wave, sine wave output is the phase voltage, the corresponding current is sine wave current. This way has no concept of square wave to control the reversing, or that an electrical cycle reversing the infinite times. Obviously, sine wave control compared to square wave control, the torque ripple is small, less current harmonic, control feels more 'exquisite', but the performance requirements of the controller is a bit higher than that of square wave to control, and motor efficiency can't play to the maximum. FOC control is realized the voltage sine wave vector control, indirect help to control the current size, but can't control the direction of current. FOC control mode can be thought of as an upgraded version of the sine wave control, realized the current vector control, which has realized the vector control of motor stator magnetic field. Due to control the direction of the motor stator magnetic field, so I can make the motor stator magnetic field and rotor magnetic field at all times maintain in °, achieve a certain electricity flow peak torque output. The advantage of FOC control mode is: small torque ripple and high efficiency, low noise, fast dynamic response. The disadvantage is that: the hardware cost is higher, the controller performance have higher requirements, motor parameters should be matched. Because of the obvious advantages of FOC, has in many applications gradually replace the traditional control mode, popular in the motion control industry.
