A Look at the Essential Components of a Motion Control System

Modern manufacturers must increase efficiency in their operations to remain competitive. Motion control systems, which precisely control speed, acceleration, position, and torque in industrial automated equipment, can help manufacturers achieve greater levels of productivity. These sophisticated systems have four essential components: a controller, drive, motor, and feedback device. Understanding how they work together is key to optimizing the performance of your automated production machinery.

This blog will explore these components in detail to provide insight into how the precision and repeatability provided by a well-designed motion control system can help you achieve your production goals. As your trusted partner in automation, JHFOSTER is ready to help you implement motion control solutions so you can start working more efficiently.

Four Essential Components of Motion Control Systems

The four components of a motion control system include a motion controller, a motor drive, a motor and feedback devices. 

Motion controller: Often referred to as the brain of the motion control system, the motion controller coordinates the motor drives; sometimes there are several drives being controlled at once. Based on the programmed target position and motion profiles, the motion controller creates the appropriate trajectories for the motors to follow. Like the human brain, it sends the command to accelerate to a precise speed and slow down to a stop at the desired location. The number of controllers used in an application will vary based on the number of individual processes that require control. Each controller in a system will receive instructions from and send feedback to the computer or PLC that controls the machine or line.

Motor Drive: The drive serves as the interpreter between the motion controller and the motor. Its function is to receive the command signal from the controller, interpret the command, and then supply the proper level of power to the motor to provide accurate movement of the machine. Drives are available as digital, analog, linear, switching, stepper, and servo drives. Each type of drive has different characteristics. Digital drives contain discrete input and output capabilities, while analog drives contain variable input and output capabilities. Linear drives are used for straight motion. Switching drives use a technique called pulse width modulation to turn voltage on and off rapidly to create a particular motion or speed. Stepper drives offer low- to mid-level torque and produce smooth rotation over a wide speed range. Servo drives interpret command signals and internal feedback loops to precisely control motion in high-power, high-speed applications.

Motor: The motor functions as a muscle. Its role is to receive the electrical input from the motor drive and convert it into motion. The two types of electric motors are AC and DC, and they both transform electricity into motion by means of magnetic fields. DC motors run on Direct Current, while AC motors run on Alternating Current. The speed of DC motors is typically controlled by varying the amount of applied voltage. The speed of AC motors is usually controlled by varying the frequency of the applied voltage.  AC motors are more commonly used. 

Feedback Devices: Used only in closed-loop motion control systems, feedback devices provide motor position information to the motion controller so it can adjust its commands at the appropriate times. Encoders, which measure and report position, velocity, and direction, are the most popular feedback devices. Closed-loop motion control systems can precisely perform complex motions that open-loop motion control systems can’t.

How Does Motion Control Work?

Motion control systems create a precise sequence of movement, called the motion profile, and then continuously adjust the motor’s operation to match the specified sequence. Here’s how a  motion control system works:

Step 1: The motion controller receives the target command.

Step 2: The controller calculates the desired trajectory (the motion profile).

Step 3: The controller sends a command signal to the motor drive.

Step 4: The drive supplies the necessary electrical power to the motor.

Step 5: The motor executes the motion.

Step 6: In a closed-loop system, the feedback device measures the actual motion and sends this information back to the controller.

Step 7: The controller compares the actual motion to the desired motion and adjusts the commands (the control loop) to correct any errors, ensuring precision motion.

Understanding Motion Sensors

In industrial motion control, the “motion sensor” is the feedback device, which is most often an encoder. To provide feedback, encoders measure the actual motion parameters, such as position, velocity, and/or direction, and relay them to the controller for system correction.

What Will Trigger a Motion Sensor?

In an industrial closed-loop motion control system, the motion sensor (typically an encoder) is triggered by the movement of the motor shaft or linear stage. The encoder is connected to the motor so that when the motor moves, the encoder detects this movement and sends out a signal.

How Do You Know if Your Motion Sensor is Working?

There are three common ways to determine whether your industrial motion sensor is working.

Monitor feedback data: The most reliable method of verifying that your encoder is operational is to check the position or velocity data sent to the motion controller through the Human Machine Interface (HMI) or machine software. If the machine moves and the data updates correctly, the encoder is working.

Look for faults: If the sensor fails in a closed-loop motion control system, a fault or alarm will be triggered because the controller cannot verify or correct the motor position.

Verify motion accuracy: Issues such as the machine failing to hold position or showing excessive vibration may indicate a malfunctioning or improperly tuned feedback device.

Where is Motion Control Used?

To increase efficiency and lower operational costs, more manufacturers are automating their production lines, and motion control plays a key role in effective automation. Motion control systems can be found in applications where intricate motions must be repeatable, precise, and adjustable, including:

• Pick-and-place robots for palletizing and packaging tasks.
• Robots/cobots are used for welding, assembly, cutting, and other tasks that require precise movement.
• Precise CNC machining.
• 3D printers.
• Automated material handling systems.
• Automotive assembly applications.

As the integration of automated equipment continues to increase, motion control systems are essential to precise, repeatable motion, which helps you maximize productivity and lower operational costs.

JHFOSTER, your partner in automation, is ready to assist with your motion control needs. Contact us today to start increasing the accuracy and efficiency of your application.