Hybrid Stepper Motor Design Principle

Hybrid Stepper Motor Design principle

Design principle and control of three - phase hybrid stepping motor driver. Preface The stepper motor is an open-loop servo motion system actuator that controls the output and outputs the angular displacement. Compared with the AC servo motor and DC servo motor, its outstanding advantages is the low price, and no accumulation of error. However, the stepper motor running there are many shortcomings, such as low-frequency oscillation, noise, resolution is not high, but also seriously restricted the scope of application of stepper motor. Stepper motor operating performance and its drive are closely linked, you can drive technology improvements to overcome the shortcomings of stepper motor. Compared with other driving methods, subdivision drive mode can not only reduce the stepping motor stepping angle, improve the resolution, and can reduce or eliminate low-frequency vibration, the motor running more smoothly and evenly. In general, the subdivision-driven control is the best. Because the commonly used low-end stepper motor servo system without encoder feedback, so as the motor speed increases its internal control current correspondingly reduced, resulting in lost step phenomenon. So the speed and accuracy requirements of the field is not high, its application is very extensive. Because the three-phase hybrid stepper motor has better low speed stability and output torque than the two-phase stepping motor, the three-phase hybrid stepping motor has better application prospect than the two-phase stepping motor. The traditional three-phase hybrid stepping motor control method is completed by hardware comparator. This paper mainly introduces the use of DSP and space vector algorithm SVPWM to realize three-phase hybrid stepping motor control. 2. Subdivision principle Stepping motor subdivision control is essentially through the stepper motor stator winding current control, so that the stepper motor within the synthetic magnetic field changes according to a certain requirements, in order to achieve stepper motor step angle The breakdown. The best way to subdivide is the constant torque and other step angle subdivision. Under normal circumstances, the synthetic magnetic field vector determines the magnitude of the motor rotation torque, adjacent two synthetic magnetic field vector between the angle of the size determines the size of the step angle. In the motor to produce close to the uniform circular rotating magnetic field, each phase of the winding of the synthetic magnetic field vector, that is, each phase winding current vector should be in the space for a constant amplitude of the rotary motion, which need to pass in each phase Sinusoidal current. Three-phase hybrid stepper motor works very similar to AC permanent magnet synchronous servo motor. The permanent magnet magnet used in the rotor is also a rare earth permanent magnet material with high magnetic density, so the effect of the induced current on the rotor on the rotor magnetic field is negligible. In the structure, it is equivalent to a multi-pole logarithmic alternating current permanent magnet synchronous motor. Since the input is a three-phase sinusoidal current, the resulting magnetic field is circularly distributed, and the torque characteristics of the three-phase hybrid stepping motor can be analyzed using the structural model of the permanent magnet synchronous motor (Fig. 1). For the sake of ease of analysis, the following assumptions can be made: a. Motor stator three-phase winding is completely symmetrical; b. Magnetic saturation, eddy current and core loss are ignored; c. Excitation current No dynamic response process.

 Three-phase permanent magnet synchronous motor simple structure model U, V, W for the stator on the three coil windings, three coil winding axis into 120 °. When the motor single-phase winding is energized, the steady-state torque can be expressed as: T = f (i, theta). Where i is the current through the winding; theta is the angle at which the motor rotor deviates from the reference point. Since the magnetic saturation effect is negligible, and the rotor structure is circular, its moment angle is strictly sinusoidal, due to the internal circular rotating magnetic field, the motor output torque is constant. Therefore, the AC servo control principle applied to the three-phase hybrid stepper motor drive system, the input 220V AC, rectified into DC, and then through the pulse width modulation technology into a three-step ladder-type sine wave current, they press Fixed timing, respectively, through the three-way winding, each ladder corresponding to the motor rotation step.