What Are Motion Controllers?

Motion controllers are control circuits specifically made to coordinate movements. A typical application may involve a robot picking up an object from one place, moving to another place and putting the object down, this action could involve moving two are more axes at the same time as illustrated below:

In the example above, three axes are moving at the same time. The motor for each axis would accelerate up to speed, travel at a fixed speed to the vicinity of the destination, and then decelerate to a stop. The speeds of the motors would be controlled so that they all arrived at the destination at the same time, even if that meant that they moved at different speeds.

A motion controller is essentially a programmable digital controller. A typical controller is built on a circuit card and may be able to control 4 to 8 axes. The controller can be either open loop or closed loop. Open loop systems have to use stepper motors. Closed loop systems employ DC or AC servo motors and require feedback sensors, which are usually optical encoders. Outputs from the motion controller card provide the speed or torque signal to the motors (Or motor drives). Inputs to the controller come from the sensors. ?The two possible hardware configurations are shown below:

The system shown in Figure 1.1 is a PC with a motion controller expansion card. The card can be programmed with special software that runs under Windows. The second configuration in Figure 1.2, the motion controller is a module that runs under a PLC. In this case, the PLC would download the motion parameters into the motion controller, and then the motion controller would then function on its own.

Also Read: Cascade Control

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