A servo motor is an electric actuator that operates as part of a closed-loop system. It includes a feedback mechanism—typically a sensor such as an encoder—that continuously reports the motor's actual position or speed to a controller. This allows the system to adjust its output until the desired state is reached.
When a command is sent, an electrical signal moves the output shaft to a specified angle, position, or velocity. The feedback device confirms whether the target has been achieved, and corrections are applied as needed.
Servo motors operate within a closed-loop system, meaning position and speed are continuously monitored and adjusted. In contrast, open-loop systems execute commands without verifying the final position.
A typical servo motor consists of a standard DC or AC motor combined with a feedback sensor and a control circuit. The control circuit interprets input signals and drives the motor accordingly.
Types of Servo Motors
Servo motors are available in several configurations, each suited to different types of movement. Three common types include:
Continuous rotation servos are designed to spin continuously in either direction. Speed can be controlled, but position cannot. Hobbyist projects—small robots, toy cars, or RC vehicles—often rely on these motors for drive systems.
Positional rotation servos move to and hold a specific angular position, typically within a range of 0 to 180 degrees. They are used in radio-controlled models, robotic arms, and other applications where angular positioning is required.
Linear servos produce motion along a straight line rather than rotating. They are found in applications requiring precise linear movement, such as industrial automation or actuation systems.
Beyond configuration, servo motors also differ in their power source, which affects where and how they are used.
AC and DC Servo Motors
Servo motors may be powered by either alternating current (AC) or direct current (DC). The choice between the two depends on the application requirements.
AC servo motors are commonly used in industrial equipment such as machine tools, robotics, and automation systems. They are designed to handle higher voltages and are typically found in applications requiring continuous operation. Voltage changes are managed through external transformers or drives.
DC servo motors are often used in smaller systems where rapid response and straightforward control are needed. Current flow is unidirectional, and control is typically achieved by varying the voltage applied to the motor windings. These motors appear frequently in battery-powered devices, hobbyist projects, and small-scale automation.
Applications of Servo Motors
Servo motors appear in various industrial and consumer applications. In manufacturing, they control axis movement in machine tools and CNC equipment. Factory automation systems—conveyors, pick-and-place units, and assembly lines—also rely on them for motion control.
Material handling and packaging machinery represent another major use case. Robotics, both industrial and hobbyist, depends on servo motors for joint movement and positioning. Radio-controlled models use them to control surfaces or steering in airplanes, cars, and boats.
Other applications include:
Aerospace systems, where they regulate hydraulic valves and actuators
Automotive systems, such as cruise control actuators and throttle control
Consumer electronics, including DVD and Blu-ray players, where they open and close disc trays
Toys and educational kits that require controlled motion
In each of these applications, the servo motor operates within its rated specifications. Acceleration, speed, and torque are determined by the motor design and the drive system used.
Operational Characteristics
Servo drives regulate motor speed, position, and acceleration through closed-loop control. When energized, the motor can maintain a set position. Acceleration and deceleration rates are defined by the motor's specifications and the capabilities of the connected drive.
Machines and robots equipped with servo motors are capable of controlled motion across a range of operating conditions. Their performance is influenced by factors such as load, speed, and duty cycle—all of which are outlined in manufacturer documentation.
Servo motors are available with different cost structures and maintenance intervals depending on the model and application. They can be integrated into systems that support standard control interfaces, provided that voltage, current, and signal requirements are met.
Source:https://www.oyostepper.com/article-1117-The-Application-of-servo-motor-and-how-it-works.html
