Elements of Motion Control - Open and Closed-loop Control

Summary

This video script explains the difference between open-loop and closed-loop control systems. Open-loop systems operate without feedback, while closed-loop systems use feedback to adjust the output to match the desired setpoint. The script outlines the key components of a closed-loop motion control system, including the operator interface, motion controller, motion profile, amplifiers, actuators, and feedback devices. It describes how each component works together to ensure precise motion control, highlighting the importance of monitoring and adjusting for optimal performance.

Takeaways

• 😀 Open-loop systems do not measure or monitor output, meaning they lack feedback for comparison with the setpoint.
• 😀 Closed-loop systems use feedback to maintain the desired output by comparing it with the actual condition.
• 😀 Closed-loop motion control systems automatically adjust based on feedback from sensors and controllers.
• 😀 The operator interface allows users to input commands to the controller, such as using industrial computers or terminals.
• 😀 The motion controller creates motion profiles, which define parameters like position, velocity, and torque for actuator movement.
• 😀 Position profiles in motion control include start and finish positions for the load's movement.
• 😀 Velocity profiles are often trapezoidal, with constant acceleration, velocity, and deceleration.
• 😀 The torque profile uses constant positive or negative acceleration to achieve the target velocity as defined by the motion profile.
• 😀 Amplifiers, or drives, convert the motion profile from the controller into the current needed to drive the actuator (motor or other types).
• 😀 Actuators, such as motors or cylinders, convert electrical signals into physical motion, with linear actuators converting rotary to linear motion.
• 😀 Feedback devices like encoders or position sensors monitor the actuator's position and send updates to the controller to adjust movement accordingly.

Q & A

What is the difference between open-loop and closed-loop control systems?

An open-loop control system does not measure or monitor the output to compare it with the system's setpoint, while a closed-loop system uses feedback devices to automatically adjust and maintain the desired output by comparing the actual condition with the target.

What is another name for open-loop systems?

Open-loop systems are also referred to as non-feedback systems.

What role does the operator interface play in a closed-loop motion control system?

The operator interface allows the user to command signals to the controller, typically through devices like industrial computers or operator interface terminals.

What are the key components of a simple motion profile in a closed-loop motion control system?

A simple motion profile consists of position, velocity, and torque parameters, including a start and finish position for moving a load, and a trapezoidal shape for velocity with constant acceleration and deceleration.

How does the motion controller function in a closed-loop system?

The motion controller takes the user input from the operator interface and creates a motion profile for the actuator to follow, ensuring the system meets the desired movement parameters.

What is the function of amplifiers or drives in a motion control system?

Amplifiers or drives take the motion profile from the controller and generate the current necessary to drive the motor or other actuators.

What types of devices are considered actuators in motion control systems?

Actuators in motion control systems can include motors, cylinders, or other electromechanical devices used to create motion.

What is the role of linear actuators in industrial applications?

Linear actuators convert rotary motion to linear motion, typically by turning the actuator nut to move the screw in a straight line.

How does the feedback device work in a closed-loop motion control system?

The feedback device, usually an encoder or position sensing device, monitors the motor’s position and relays the information back to the controller to compare with the user input.

What type of information does the encoder provide in a motion control system?

The encoder provides position and speed information, which are relayed to the controller for comparison with the motion profile and user input.