From Motors and Drives

The servomotors used in industry today are used in a closed-loop servo system. To understand how the servomotor is used in the system, it is first necessary to review the entire system. Figure 3-44 indicates a block diagram of a typical servo system.

A reference input (typically called a velocity input) is sent to the servo amplifier, which controls the speed of the servomotor. Directly mounted to the machine (or to the servomotor) is a feedback device (either an encoder or resolver). This device changes mechanical motion into electrical signals and is used as a feedback loop. This feedback loop is then sent to the error detector, which compares the actual operation with that of the reference input. If there is an error, that error is fed directly to the amplifier, which makes the necessary corrections.

In many servo systems, both velocity and position are monitored. (Note: In servo systems, the word "velocity" is often used to describe speed control. Velocity indicates a rate of change of position, with respect to time. It also indicates a rate of motion in a particular direction, with respect to time.) The velocity loop control may take its command from the...

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Products & Services
AC Servomotors
AC servomotors are responsive, high-acceleration motors typically constructed as permanent magnet synchronous motors.
DC Servomotors
DC servomotors are generally small and powerful for their size, and easy to control. Common types of DC servomotors include brushless or gear motors.
Motor Speed Controllers
Motor speed controllers are electronic devices that control motor speed. They carry specifications for drive type, product classification, electrical ratings, and operating parameters.
Motor Controllers
Motor controllers receive supply voltages and provide signals to motor drives that are interfaced to motors. They include a power supply, amplifier, user interface, and position control circuitry.
Servo Drives
Servo drives provide electrical drive outputs to servo motors in closed-loop motion control systems where position feedback and corrective signals optimize position and speed accuracy.

Topics of Interest

AC Servomotors This type of motor is basically a two-phase induction motor, capable of reverse operation. To achieve the dynamic requirements of a servo system, the servomotor must have a small...

A few logical procedures during setup can tune motion controllers to perform at their best. For many engineers, the process of tuning a servomotor is a mysterious black art. But the procedure needn't...

Introduction Basically, four different types of DC motors are used in industrial applications: series wound, shunt wound, compound wound, and permanent magnet. Several factors must be considered when...

Control of ac servomotors can now take place on a single IC. Digital Control IC Design Center Circuitry for handling highperformance control of ac servos has been condensed onto one chip in the...

Manufacturers have also developed special-purpose ICs that handle tasks needed to implement both closed-loop motion control and motor speed control. Presently, three chips are available for...

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