How Do Servo Actuators Work?

Servo motor-controlled actuators provide precise, repeatable movements for industrial machines. Many applications use these actuators, including those requiring high-precision positioning and cycling. So, how exactly do these actuators work, and what advantages might they bring to your project?

Let’s examine how they function to help you decide whether servo actuators fit your unique application.

How Servo Actuators Work

Converting electrical energy into controlled mechanical motion, Servo actuators stand at the forefront of automation technology. Their operation hinges on a sophisticated feedback loop system that integrates sensors and advanced control algorithms.

These components work harmoniously to adjust the actuator’s output in real-time, ensuring unparalleled torque, speed, and position precision. This dynamic responsiveness is crucial for applications that demand meticulous control and repeatability, from CNC machinery to advanced robotic systems.

A Closed-Loop Mechatronic System

A servo actuator functions as a closed-loop mechatronic system. Closed-loop mechatronic systems used in industrial machinery generally include a motion controller, a servo drive, and a motor with encoder feedback. The controller sends motion commands to the servo drive for current and speed control. The motor generates mechanical output while feedback devices verify actual position and torque values. Continuously updating, the system maintains precise control during changing loads and dynamic motion patterns.

Closed-loop control enables actuators to handle disturbances from friction, changing loads, and external forces that would cause open-loop systems to lose position.

The servo system actively adjusts its operation to maintain both accuracy and stability throughout the motion.

What Is a Servo Actuator?

In industrial automation, a servo actuator is a pivotal component. Commanded by a control system, it’s a sophisticated device designed to execute controlled movements.
These actuators are renowned for their efficiency, utilizing a servo motor to control the motion accurately.

Configured for linear or rotary motion, servo actuators offer versatility, making them indispensable for many automation tasks, from simple conveyor systems to complex robotic arms.

The servo motor, together with transmission components, feedback sensors, and drive electronics, forms a single motion-control unit in actuator assemblies. The integrated design of servo actuators allows better control bandwidth. They produce smoother movements and more dependable position consistency than standard electric actuators.

Types of Actuators

The industrial world utilizes various actuators, including:

• Hydraulic
• Pneumatic
• Electric (non-servo)
• Servo actuators

Each type has its strengths, with servo actuators particularly lauded for their precision and programmability. This capability makes them the go-to choice for applications that require precise motion and fine-tuned control.

Hydraulic actuators operate best in applications that require a strong force but not precise movement. Pneumatic systems work best for basic on/off operations and for fast, but imprecise, movements. Electric actuators operate in standard automation systems that need average control precision.

Servo actuators operate at the highest level of performance because they need to execute precise motion sequences and allow users to program their operation.

At this point, the selection of servo actuator types between rotary and linear, and belt-driven and screw-driven, and direct-drive configurations becomes essential. The different types of actuators offer unique advantages in terms of speed and load capacity.

Linear Servo Actuators

These actuators move machine parts linearly, typically executing back-and-forth motions. They exert a mechanical force, facilitating straightforward linear movement.

The core components include a rotary synchronous servo motor, which provides high-precision rotational output over a wide range of speeds. This output is then amplified in terms of torque by gearboxes.

Finally, rotary motion is converted to linear motion using mechanisms like belts, leadscrews, or ball screw assemblies. Each mechanism offers its balance of performance and cost considerations.

Linear servo actuators operate in:

• Pick-and-place systems
• Medical tables
• Metrology equipment
• Industrial pressing machines
• Small-format gantries
• Packaging machinery

Engineers select mechanical transmission based on whether they need to maximize stiffness, speed, cost reduction, or service duration.

Rotary Servo Actuators

Rotary actuators excel at producing circular motion, either to fixed degrees or continuously, which is essential for many applications.

The heart of these actuators is an electric motor. The electric motor converts electrical energy into mechanical energy. This conversion results in rotational torque on the output shaft. Two types of electric motors commonly found in rotary actuators are induction motors and synchronous servo motors.

Induction motors are well suited for applications that require a high-duty cycle with variable speed. When integrated with a position sensor, these motors can accurately position payloads. Induction motors are used in applications like mixers, fans, saws, and pumps.

Synchronous servo motors have become more prevalent than induction motors and servo-based rotary actuators. They deliver better torque performance and exact position feedback control. Motors combined with harmonic, planetary, and worm gear reducers produce compact high-torque rotary modules.

These modules operate in:

• Indexing tables
• Robotics joints
• Automated assembly systems

Linear Actuator vs. Servo Actuator

While linear actuators are designed for straightforward, unidirectional motion, servo actuators offer more control. This includes the ability to precisely dictate movement patterns, speed, and positioning, making them more suitable for complex automation tasks.

Distinguishing between linear and servo actuators is key to selecting the suitable component for specific industrial applications.

The main difference between these two systems lies in their feedback control capabilities. The feedback system of traditional electric linear actuators depends on either limit switches or basic pot-style sensors.

Servo actuators achieve precise motion control through their use of high-resolution encoders and resolvers. The selection between these two systems depends on the specific requirements of high-cycle and dynamic load applications.

Stepper vs. Servo Motor for Actuators

In actuator design, the servo vs stepper motor discussion often comes up early because the two technologies behave very differently under real industrial loads.

Servo actuators outperform stepper-driven actuators in applications that require fast acceleration, variable loading, high accuracy, and extended operation time.

Steppers operate effectively for basic open-loop positioning at low speeds. However, they fail to deliver the continuous torque and closed-loop feedback that servo systems provide.

What Is the Purpose of Servo Actuators?

At their core, servo actuators create precise movement in machines by converting supplied energy into mechanical force. This transformation is key in tailoring the actuator’s output to the specific motion requirements of various industrial applications, whether they involve linear or rotary servo actuators.

Many favor rotary servo actuators for their adaptability because they generate circular motion that can seamlessly convert to linear motion, typically via mechanisms like pulleys and belts.

Efficiency and Versatility

This ability to convert rotational movement into linear displacement allows for efficient transport of objects from one point to another. Their versatility in motion control makes them an ideal choice for a wide range of industrial scenarios, where precision and adaptability are paramount.

In every application, the primary objective of servo actuators remains the same: to enable effective and controlled mechanical movement within a machine, aligning with the principles of actuation products and power density.

Modern servo actuators perform beyond basic motion. Servo actuators are capable of precise motion profiles, torque control, and coordinated multi-axis synchronization for high-performance machinery operations.

Servo Actuator Advantages

Servo actuators are pivotal in industrial settings due to their numerous advantages, which include superior performance, precision control, compact size, and low energy consumption. These attributes make them ideal for various demanding industrial applications and environments.

Superior Performance: A servo actuator is renowned for delivering exceptional torque, speed, and power throughout its lifespan. This consistent, dependable performance is vital in industrial contexts where reliability and efficiency are paramount.

Precision Control: One of the hallmark features of servo actuators is their ability to enable highly accurate motion control. This precision is mandatory in applications where exact positioning and near-perfect repeatability are crucial, ensuring operations are carried out with the utmost accuracy.

Compact Size: The design of linear and rotary servo actuators is remarkably size-efficient. This compactness is crucial in applications with space or weight constraints, such as robotics systems, where integrating servo actuators helps create more compact and lightweight solutions.

Low Energy Consumption: Servo actuators offer high power density, which translates to reduced overall energy consumption. This cost-effectiveness efficiency aligns with the growing need for more sustainable, energy-efficient industrial solutions across various sectors.

These advantages collectively contribute to the growing adoption of servo actuators in diverse industrial applications, underlining their role as a transformative component in modern machinery.

Programmability stands as a major benefit of servo actuators. They allow users to adjust their compliance, stiffness, damping, acceleration limits, and multiple positioning profiles. These advanced customization features help engineers create machines that fulfill specific requirements.

Engineers can optimize for performance, operational safety, and extended lifespan while reducing energy consumption.

Application Examples

Servo actuators are integral to the nuanced requirements of medical devices and the demanding environments of manufacturing lines. They provide the necessary precision and reliability for many applications.

Material Handling

Precise automation is critical in material handling, where speed, accuracy, and care are crucial to meet consumer demands. A linear or rotary servo actuator grants material handling systems a new control caliber, ensuring materials are transported quickly and safely to their proper destinations.

Functional safety tools, such as emergency brakes and Safety PLCs, can elevate these solutions to maximize safety while keeping the supply chain fluid.

Servo-driven conveyors and lifts improve motion transitions, reducing product damage and enhancing operational cycle stability.

Servo actuators in warehouse automation help robotic systems to perform coordinated multi-axis movements, which are necessary for both robotic picking and high-speed sorting operations.

Medical Devices

Medical devices require pinpoint accuracy to support patient safety and comfort. This is where a rotary or linear servo actuator excels. Medical tools that require precise motion control, such as patient lifts, can use servo actuators to properly position objects or patients for treatment.

Purpose-built brakes and clutches can further improve these medical applications. Servo actuators operate as the preferred choice for medical equipment because they provide silent operation and consistent performance under changing load conditions.

The design process benefits from servo actuators because they deliver smooth operation and consistent results.

Robotics

Robotics is an ascendant force in automation, sweeping diverse industrial applications from metalworking and spot welding to packaging and plastics. With servo actuators, machine builders can create more dependable, efficient robotic systems that move tools, parts, or materials with unmatched precision.

Robotic joints, end-of-arm tooling, autonomous vehicles, and collaborative robots depend on servo actuators. The combination of high torque density and precise feedback in servo actuators allows designers to build compact robotic arms that maintain exact positioning during fast multi-axis operations.

Feedback Systems in Servo Actuators

The operation of servo actuators depends on high-performance feedback systems, which enable closed-loop control. The most common feedback devices used in servo systems include:

• Incremental encoders
• Absolute encoders (single- or multi-turn)
• Resolvers
• Hall sensors (supporting commutation)

Precise encoder position data enables systems to achieve accurate speed, torque, and displacement control. Absolute encoders offer high accuracy, and precision required by complex motion profiles used in dynamic actuators. Resolvers maintain strong performance in harsh environments, making them well-suited for heavy-duty actuators and equipment exposed to vibration, heat, or contaminants. KEB servo motors can be configured with absolute encoders or resolvers.

The system requires feedback to perform real-time corrections and maintain stability when operating under dynamic loads. KEB servo motors are designed for actuator integration.

Servo Motors and Servo Actuators

KEB develops world-class products that work with actuators to drive performance, including servo motors and brakes for electric linear actuators.

At the end of the day, a successful servo actuator depends heavily on the quality of the servo motor driving it. Torque characteristics, thermal behavior, feedback resolution, and motor inertia all influence the actuator’s performance envelope. Selecting the right motor leads to accuracy and long-term reliability.

Servo actuators are essential components in modern industrial automation. Understanding their function and benefits is crucial in selecting the proper actuator for your needs.