Open loop vs. closed loop, which control system would benefit your operation more? It may seem like a tricky question at first, but after learning the differences with Motion Automation Intelligence, you’ll know precisely what system works for you. Closed-loop and open-loop control systems differ in how they handle feedback. However, both are crucial components of electro-mechanical systems and offer effective motor control for specific applications. In addition, open and closed-loop systems can be combined to achieve many processes. First, let’s dive into a basic breakdown of how a control system works.

Control System Breakdown

Control systems have three essential elements: input, amplification, and output. Input usually comes from signals such as temperature, velocity, force, torque, position, or other physical/environmental events. The input triggers amplification, which modifies the input into output. Complex control systems may have multiple inputs, gain control, complex loops, filters, and output signals. The critical distinction between the two is their feedback loop, despite having similar components like drives, motors, and controllers.

Open-loop vs. Closed-loop Control System

Open-loop systems have a similar structure to typical control systems, like input, amplification, and output. They start with an input and produce a desired output, running until completion with no feedback to adjust the operation. An example is a timer-based toaster: bread is placed in the toaster, a timer is set to however long, and a lever is pushed to start heating. The toaster stays heated for the appointed time, then the toast pops up, the coils turn off, and the process ends. Pretty simple.

Closed-loop systems are different and use feedback to adjust the control system's processes. The input, feedback, and output are continually monitored and compared, and the output updates at set intervals. This leads to a constantly changing output as the amplification phase repeats. Examples include temperature control systems (thermostats) and cruise control systems. They adjust automatically based on feedback, compared to a set point, without user input.

For example, room temperature feedback is compared to a fixed point in a temperature control system, and the output (air generation and flow) is adjusted. In a vehicle cruise control, the vehicle's velocity feedback is compared to the set point speed. The amplification controls the velocity change rate (acceleration) to maintain a smooth, consistent set speed.