Relationship between position sensor and brushless DC motor

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Relationship between position sensor and brushless DC motor [Copy link]

The position sensor is one of the three major parts of the brushless DC motor system and is also the main feature that distinguishes it from a brushless DC motor. Its function is to detect the position of the main rotor during movement, convert the position signal of the rotor magnetic pole into an electrical signal, and provide the correct commutation information for the logic switch circuit to control their conduction and cutoff, so that the current in the motor armature winding commutates in sequence as the rotor position changes, forming a step-by-step rotating magnetic field in the air gap, and driving the permanent magnet rotor to rotate continuously. The position sensor is used to measure the position of the rotor. The motor controller receives the position sensor signal to synchronize the inverter with the rotor to drive the motor to run continuously. Although the brushless DC motor can also detect the position of the rotor through the reverse induced electromotive force generated by the stator winding without the position sensor, the speed is too low when the motor starts, and the reverse induced electromotive force signal is too small to detect. The Hall sensor chip that can be used as the position sensor of the brushless DC motor is divided into switch type and locking type. For electric bicycle motors, these two Hall sensor chips can be used to accurately measure the position of the rotor magnet. The performance of the brushless DC motor made with these two Hall sensor chips, including the output power, efficiency and torque of the motor, has no difference, and can be compatible with the same motor controller. =The application of position sensors can reduce the noise of motor operation, improve the life and performance of motors, and reduce energy consumption. The application of position sensors has undoubtedly provided a strong impetus for the development of the motor market. The crankshaft position sensor is also called the engine speed and crankshaft angle sensor. Its function is to collect the crankshaft rotation angle and engine speed signals and input them into the electronic control unit (ECu) to determine the ignition timing and injection timing. In order to distinguish it from the crankshaft position sensor (CPS), the camshaft position sensor is generally represented by CIS. The function of the camshaft position sensor is to collect the position signal of the valve camshaft and input it into the ECU so that the ECU can identify the compression top dead center of cylinder 1, thereby performing sequential injection control, ignition timing control and detonation control. In addition, the camshaft position signal is also used to identify the first ignition time when the engine is started. Because the camshaft position sensor can identify which cylinder piston is about to reach the top dead center, it is called a cylinder identification position sensor.

Position sensor structural features: The photoelectric crankshaft and camshaft position sensors produced are improved from distributors, and are mainly composed of signal disks (i.e. signal rotors), signal generators, distributors, sensor housings, and wiring harness plugs.

The signal disk is the signal rotor of the American MACRO position sensor, which is pressed onto the sensor shaft. Two circles of light-transmitting holes with evenly spaced arcs are made near the edge of the signal disk. Among them, the outer ring is made with 360 light-transmitting holes (gaps) with an interval of 1 arc. (The light-transmitting hole accounts for 0.5°, and the light-shielding hole accounts for 0.5°), which is used to generate crankshaft angle and speed signals; the inner ring is made with 6 light-transmitting holes (rectangular holes) with an interval of 60°, which are used to generate the top dead center signals of each cylinder, and one of the rectangular wide sides is slightly longer, which is used to generate the top dead center signal of cylinder 1. The signal generator is fixed on the position sensor housing, which consists of a Ne signal (speed and angle signal) generator, a G signal (top dead center signal) generator and a signal processing circuit. Both the Ne signal and the G signal generator consist of a light-emitting diode (LED) and a phototransistor (or photodiode), and the two LEDs are facing the two phototransistors respectively. bit

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The signal generator is fixed on the housing of the position sensor, and it consists of a Ne signal (speed and angle signal) generator, a G signal (top dead center signal) generator, and a signal processing circuit. Both the Ne signal and the G signal generator consist of a light-emitting diode (LED) and a phototransistor (or photosensitive diode), and the two LEDs are facing the two phototransistors respectively.