Servo Drives and Motors

What is a Servo System?

Servo System Definition

A Servo Drive is a special electronic amplifier used to power electric servomechanisms to amplify performance in terms of the desired velocity, torque, and position/angle, as well as stiffness, and damping. The main task of a Servo Drive is to monitor feedback and continually adjust for deviation from expected behaviour (closed loop system). A Servo Drive is thus only one component forming part of a more comprehensive system referred to as a Servo System (servomechanism). Servo Systems includes four main components, a Servo Drive, a Servo Motor, a motion Controller, and a Feedback Device (usually referred to as an Encoder).

In a Servo System, a Servo Drive is responsible for powering the Servo Motor. The Servo Drive is an incredibly important component in determining the performance of the Servo System.

The motion Controller (sometimes referred to as the ‘brains’) determines what the Servo Motor must do and then triggers the Servo Drive (sometimes referred to as the ‘nervous system’) to send the necessary electrical energy to the Servo Motor to make the required movement/action happen (execute). In other words, the Controller calculates the path/trajectory/movement required and sends a low-voltage command signal to the Servo Drive, which in turn, sends the necessary voltage and current to the Servo Motor to achieve the required motion. Servo Drives can control torque, velocity, or position (torque control being the most common parameter).

For a more detailed explanation on this, please see our blog post: What is a Servo Drive?

Advantages of using a Servo System

Servo System Benefits

The main advantage of a Servo System, compared to traditional DC or AC motors, is the addition of motor feedback. This feedback can be used to detect unwanted motion, or to ensure the accuracy of the commanded motion. Servo Drives helps to improve overall system performance through faster acceleration rates and more precise speed and position control (rotate parts with high efficiency and great precision). In providing continuous adjustment, they amplify performance in terms of the desired velocity, torque, and position / angle, as well as stiffness, and damping.

Servo Motors, in constant speed changing use, have a better life cycle than typical AC wound motors. Servo Motors can also act as a brake by shunting off generated electricity from the motor itself. Closed loop systems using Servo Drives offer more reliability and precision in motion applications than open loop systems by using the feedback to account for errors and system disturbances (unlike open loop systems). When compared to straight power amplifiers, Servo Drives offer a wide range of advantages for automatic machining systems, including superior positioning, speed, and motion control.

So, whether you are looking for a system with greater torque than a stepper motor or just more precise control, a Servo System is most likely a necessary component of your machining or manufacturing process.

For a more detailed explanation on this, please see our blog post: Advantages of using a Servo Drive

Servo System Industry Applications

What are Servo Systems Used for?

Servo Drives come in a variety of sizes and are suitable for static and mobile applications, increasing productivity and proving useful across many industries.

For automatic systems that require position control, the use of a Servo System is ideal. Whether it is just positioning a globe valve to the right position or aiming a telescope, a Servo System can be used to regulate a shaft to its desired position regardless of friction or other disturbances.

Servo System applications include CNC machining, factory/warehouse/industrial automation, laboratories, robotics, satellite communication, marine, aerospace, and defence (and many more).

Servo Systems are most used in the manufacturing industry for assembly line robots that require high repetition yet precise welding, drilling, fastening, sealing, dispensing, and rigid manufacturing. Servo Systems also enable better control over corrosion and better hygiene allowing high-pressure washing at high temperatures repeatedly for extended periods of time (typically used in the food and pharmaceuticals industries).

For a more detailed discussion on this, please see our blog post: Servo Drive Industry Applications

How do Servo Systems Work?

Servo System Working Principle

Servo Systems includes four main components, a Servo Drive, a Servo Motor, a motion Controller, and a Feedback Device (usually referred to as an Encoder).

Basically, a Servo Drive takes a command signal for position, speed or torque requirement and compares it with feedback from a servomechanism to provide the required voltage and/or current to a Servo Motor to correct any deviation from the commanded status (closed loop control).

The motion Controller is responsible for higher-level computation and decision-making (sometimes referred to as the ‘brains’). In basic terms, the motion Controller’s role is to determine what needs to be done to achieve the desired position, velocity or torque and sends this information to the Servo Drive, which produces the voltage that energises the motor windings and causes the motor to rotate or produce torque. The Controller thus moves information from the Feedback Device and sends the necessary signals to the Servo Drive. The motion Controller (the ‘brains’) has basically two tasks to perform, Command Tracking (tracks the commanded input - Reference Tracking) and Disturbance Rejection (improves the system’s disturbance).

Command Tracking and Disturbance Rejection functions are enabled by the Servo System’s control loop capability. Servo Tuning involves finding the appropriate corrections (amount and type of change for the various error conditions) to allow Command Tracking and Disturbance Rejection without causing the Servo System to become unstable.

The role of the Servo Drive is to translate low power command signals from the Controller into high power voltage and current to the Servo Motor. In essence, the Servo Drive (the ‘nervous system’) sends the required amount of current to the Servo Motor. Depending on the application, the Servo Drive can regulate and properly coordinate the Servo Motor’s desired position, speed, torque, etc. This is an ongoing process of reading and responding to the feedback which created a closed loop system and is the defining feature of a Servo System, allowing it to improve the transient response times, reduce any steady-state errors, and reduce the sensitivity of the system to load parameters.

Servo Drives can account for expected errors through a feedback monitoring device that leverages negative feedback to send a signal back through its own control loop and/or to the main Controller. In motion control, the Feedback Device evaluates the relation of the control input to the actual position of the mechanism or control shaft. By understanding the relationship between the actual value and “wanted value” of the shaft’s position, the Feedback Device sends a signal to the Servo Drive for corrective action in the Servo Motor.

For a more detailed explanation on this, please see our blog post: How do Servo Drives Work?

What is a Servo System?

Servo System Definition

TCGC distributes the following EMHEATER Servo Products:

Servo Motor and Servo Drive

VSD for Synchronous Motor