Design Article

Microstepping bipolar drive of two-phase hybrid stepping motor on TMS320F2808 DSC

Chawakorn Yodsanti and Mongol Konghirun, Texas Instruments

4/7/2009 9:28 AM EDT

Hybrid stepping motors are used in a wide variety of position controlled equipments such as plotters, CNCs, printers, robots, etc. However, in high precision applications, the microstepping scheme is necessary for accurate motor rotation. Two main advantages of this scheme have been well reported in literature such as: reduction of resonance behavior and smooth movement with very low ripple torque. In this particular technical paper, the microstepping scheme with configurable fractional step is implemented using a fixed-point TMS320F2808 DSC from Texas Instruments, Inc. The discrete angle for discretized sinusoidal voltage commands is generated by the zero hold order (ZOH) module. The motor currents are controlled by using unipolar pulse width modulation (PWM) technique. The dual H-bridge circuit is primarily used to drive a two-phase hybrid stepping motor as shown in Figure 1. Each phase winding is connected to each H-bridge circuit, therefore, four switching devices are independently controlled to generate appropriate voltage for each phase winding. The main advantage of this circuit topology is the independent generation of bipolar voltage between two phases. In low-cost, low-precision applications, the conventional full or half step scheme is selected to implement without the PWM technique. However, high performance systems employ microstepping to achieve accurate motor phase current control.

To read the rest of this technical paper, click here. Included is a link to the project collateral and source code.

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