PID Controllers with DC Gearmotors

PID Controllers with DC Gearmotors

A graph showing the overshoot and correction for positioning applications

A graph showing the overshoot and correction for positioning applications

As a designer, you always have the challenge to ensure that your chosen DC gearmotor delivers optimum performance according to its technical specifications. For a DC geared motor, the deviation from its optimum performance can happen for many reasons, such as backlash. A PID (proportional integral derivative) controller, when working in conjunction with a DC gear motor, implements a closed loop system and due to its ability to increase accuracy, it has found wide acceptance in industrial, positioning and consumer applications.

Using a PID controller to improve the positioning performance of a DC gearmotor is a smart design choice. A PID controller provides a feedback mechanism for a gear motor’s parameter, for example, the positioning accuracy. A designer, working on a geared motor application, finds a lack of positioning accuracy due to backlash. Without any control system, the application gets reduced stability or becomes sluggish.

How does a PID controller provide positioning accuracy?

A PID controller implements a closed-loop control system. Output measurement is calibrated in order to control the input. In a closed-loop control system, the following is defined:

Output = (Input − Output) × Gain

For your design requirements:

  • Use the PID controller to regulate the gain
  • Consider other factors in feedback to adjust the PID algorithms

The PID controller opens up the possibility of changing the dynamics with a larger number of options. This helps the designer in practical applications. PID controllers are viewed as three terms: a proportional term, an integral term and a derivative term. These are added together.  As a designer, use a PID controller that has well-tuned parameters for your application.

Note: High acceleration or shock on the output gear shreds gear teeth. To prevent this, the designer can also use pre-gearhead (rear shaft) encoding feedback to improve positioning control. This control can be about 1 (one) revolution on the rear shift per degree of gearhead output. This ensures slow start and slow stop, avoiding high stress on one of the teeth.

Image of a PID controller

PID controllers improve positioning accuracy

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