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Servo systems consist of four main components — motor, drive, controller, and feedback. In some cases, a standalone controller determines required motor moves and prompts the drive to supply the necessary electrical energy to make those moves happen. In other cases, drive and controller are integrated into one component. Either way, the drive core controls torque or velocity or position ... although in servo systems, the most common command parameter is torque. That control is via a torque-mode amplifier or linear drive function.


Note that servo drives are also sometimes called amplifiers because they take control signals from the controller and amplify them to deliver some voltage and current to the motor. These are not to be confused with integrated designs (including motor, feedback, controller, and drive) also sometimes called drives for their axis-driving function.

Lisa Eitel

Executive Editor, Design World

SERVO DRIVES 

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SERVO-DRIVE BASICS

Types •  Servo-Loop •   Architecture •  Servo System

What is a servo drive?

There are several types of servo drives. A common variation is the torque-mode amplifier. These convert the command signal from the controller into a specific amount of current to the motor. 

What are servo drive loops?

Servo drives, also called amplifiers in the motion-control industry, take a command signal for position, velocity, or current and adjust the voltage and current applied to the servomotor based on closed-loop feedback.

What is distributed architecture for servo drives?

Traditional servo-system architecture consists of a power supply, a motion controller, and servo drives all housed in one location that is typically a control cabinet located away from the machine.

Why are servo drives also called servo inverters, amplifiers, and controllers?

Let’s start with the term servo drive. Here’s what a drive does in a servo system: It basically takes an input signal from a controller and amplifies that signal which is then sent to the motor. 

The basic idea is easy to understand. An integrated motor-drive system combines a motor and a drive (at the very least) and can also include other components such as controllers or encoders. Sometimes these integrated motion subsystems are simply called drives.

What are integrated motor-drive combinations?

What are auto-tuning methods for servo drives?

Tuning a servo system is a complex and iterative process. It typically requires tuning multiple control loops, each with its own gains (proportional, integral, and/or derivative) to be adjusted. In addition, tuning a servo drive usually requires adjustments to additional parameters including acceleration and velocity feed-forward gains and filters to reduce oscillations.

SERVO-DRIVE SELECTION

Selecting a servo drive: 9 things you need to know

Sizing a motor for a servo application requires evaluating the move profile and torque requirements to determine the mechanical demands of the system

When do you need a linear amplifier versus a PWM drive?

For applications that require extremely smooth motion, no audible noise, and little or no EMI, linear servo drives — commonly called linear amplifiers — are preferred over PWM drives.

Where are analog servo drives used?

The purpose of a servo drive is to convert low-power signals from the controller to high-power signals to the motor, instructing it to produce the desired torque or velocity.

Where are digital servo drives used?

The original servo drives are analog types that operate on ±10-Volt inputs. In contrast, digital servo drives operate over fieldbus networks that now dominate the market.

Application •  Linear vs PWM •   Analog •  Digital

What are typical drive-based safety functions?

Functional safety standards EN/IEC 62061 and EN/ISO 13849-1 ensure safety via electronic solutions, unlike traditional safety systems, which used electromechanical components to achieve safety. And while functional safety applies to a machine and its control system (not to individual components), the drive lies at the heart of the safety implementation.

A Must Have Book for Design Engineers

This comprehensive collection with illustrations and descriptions, includes formulas, terms, and explanations for the calculations concerning drive systems. 


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maxon develops and builds high precision electric drive systems that are among the best in the world. We combine brushed and brushless DC motors, gearheads, sensors, and controllers into complete mechatronic drive systems. Our drives are perfectly suited for medical applications where extreme precision and the highest quality standards are necessary and where compromises cannot be tolerated.