Six-step Hall effect output and ladder motor phase
However, since motor manufacturers must now assemble Hall effect sensors and incremental encoders on their motors, many encoder manufacturers are beginning to offer incremental encoders with commutation outputs, often referred to simply as commutation Encoder. These encoders are designed to provide not only traditional quadrature A and B channels (and in some cases "once per revolution" index pulse channel Z), but also the standard U required for most BLDC motor drives. V and W commutation signals. This way, the motor designer can eliminate the unnecessary steps of installing both the Hall effect sensor and the incremental encoder.
Although the advantages of this method are obvious to all, this method has also made a great compromise. As mentioned above, in order to effectively commutate the BLDC motor, the position of the rotor and stator must be known. This means that care must be taken to ensure that the commutation encoder's U/V/W channel is properly aligned with the BLDC motor phase.
The process of achieving proper alignment of the BLDC motor is both repetitive and time consuming for optical encoders with fixed patterns on the disc and Hall effect sensors that must be manually placed. The alignment method also requires additional equipment, including a second motor and an oscilloscope. To align an optical encoder or a set of Hall effect sensors, a second motor must be used to drive the BLDC motor in reverse; then, when the motor rotates at a constant speed under the action of the second motor, the oscilloscope is used to monitor the three motors. The back electromotive force of the phase (also known as back electromotive force or back EMF). The U/V/W signal subsequently sent by the encoder or Hall effect sensor must be checked against the back EMF waveform on the oscilloscope. If there is any difference between the U/V/W channel and the back EMF waveform, the phase should be adjusted. In this process, each motor will take more than 20 minutes and require a lot of laboratory equipment to operate, so it is the main source of trouble for using BLDC motors. Although the optical commutation encoder solves the installation burden by installing only one technology, the implementation of the optical commutation encoder also has the disadvantage of lacking versatility. Since the optical encoder uses a fixed pattern in its optical disc, the number of motor poles, the orthogonal resolution, and the size of the motor shaft must be clearly understood before purchase.
