![]() ![]() I used seven inch round, 1/4 inch thick expanded PVC for the base of my small model. I constructed two robots using stepper motor propulsion. A couple of URLs for this are and There is also a brief version at The Hardware In addition, I noticed several universities are using an early copy of a Thomson/Airpax catalog which contains a very good review of stepping motors. A good overview of stepper motors can be found at. Stepping motors are a very different animal compared to traditional DC motors. We will only be discussing unipolar stepper motors in this article. Bipolar stepper motors need drivers that can alternately supply current in both directions through the motor’s coils, while unipolar stepper motors always run the current in one direction through the coils - which also means a simpler driver circuit. Stepper motors come in two basic types: bipolar and unipolar. In general, you will find the weight and size of a stepper motor needed to drive a given size robot larger than traditional DC motors. It has to have enough holding torque for robot propulsion. One needs to be careful in selecting a stepping motor. ![]() In addition, they cannot be operated at great rotational speeds and the faster they run, the less torque they have. They are heavier, use more power, and have far less torque than traditional DC motors. Stepper motors are not a panacea for robot propulsion. The characteristics of stepper motors that appealed to me were their ability to precisely turn a wheel at a calculated distance and their ability to brake. Individual differences in the two DC motors are then accommodated by optical feedback that provides data which can be used to match the speed of the two motors. A more typical approach is to use two traditional DC motors. This is not the usual method for propelling a robot. A few years back, I became interested in attempting to propel a wheeled robot using stepper motors. ![]()
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