The basic definition for servo motors is an automatic device that uses an error-correction routine to correct the motion of the servo motors. The general term servo can be applied to systems other than servo motors that use a feedback mechanism such as an encoder or other feedback device to control the motion parameters. Typically when the term servo is used it applies to 'servo motors' but this term is also used as a general control term with the meaning of a feedback loop to position whatever the item is including servo motors.

Servo Motors are different from other controlled motors in that it is controlled by a time-based derivative commonly referred to as the PID loop. Servo motors that are used to control position must be capable of changing the velocity of the output shaft because the time-based derivative, or the rate of change of position, is velocity.

There are two main types of servo motors - Rotary and Linear.

Rotary Servo Motors
Rotary servo motors are what most people think of when they think of servo motors. The three types of rotary servo motors are: AC Servo Motors, Brush DC Servo Motors, and Brushless DC Servo Motors. The motion of rotary servo motors is often converted into linear motion by the use of a screw thread (ball screw or leadscrew), or with the use of belts and pulleys.

Rotary AC Servo Motors are an AC type motor that is used with a feedback device. These are typically only used in smaller application because large AC Servo Motors are typically too inefficient when compared to its DC or Brushless counterparts.

Linear Servo Motors
Linear servo motors are flattened out servo motors where the rotor is on the inside, and the coils are on the outside of a moveable u-channel. Both types of servo motors are becoming more popular as the prices for servo motors continue to come down.

Servo Motors are considered one of the more expensive motors when compared to AC, Brushless, DC, Stepper, and other motor types. The reason for the expense of Servo Motors is the precision required to make the servo motors and the expensive components that go along with servo motors.

Generally speaking servo motors are intended to be a very precise positioning or speed control device. The motion of servo motors should be smooth and very precise. To accomplish these features, servo motors are manufactured under very tight control parameters. Along with the cost of the servo motors are the case, bearings, connectors, and feedback devices. The case is usually industrial grade, often sealed to achieve an IP65 rating or better. The bearings are high quality to make sure that the servo motors can run at the speeds desired and can handle the appropriate axial and radial loads. The connectors are typically mil-style connectors that can be detached at the servo motors themselves, but are still very reliable and industrial grade. The Feedback devices are typically differential encoders and or resolvers. The devices are very expensive and add cost to servo motors.

There are two options for feedback controls on Servo Motors. These options include either a servo encoder or a servo resolver. A servo encoder and a servo resolver provide the same solution in many applications, but are vastly different. They are both used to sense speed, direction, and position of the output shaft on servo motors.

The resolver on servo motors uses a second set of rotor and stator coils called the transformer to induce rotor voltages across an air gap. The resolver does not use any electronic components, therefore it's very robust with a high temperature range, and is inherently shock resistance due to its design. A resolver is mostly used in harsh environments.

The optical encoder on servo motors uses a rotating shutter to interrupt a beam of light across an air gap between a light source and a photodetector, over time the wear associated with the rotating shutter reduces the longevity and reliability of the encoder.

The application will determine whether a resolver or an encoder is needed. Encoders are more accurate and are easier to implement so they should be the first choice for any application. The only reason to choose a resolver is if environmental and longevity requires it.

Anaheim Automation provides many different accessories for our servo motors. These accessories include a brake, encoder, connector, cable and a handheld interface unit.

The brakes for our servo motors are a 24vdc system. The brakes used with the servo motors are perfect for any holding applications. They are available on all of the servo motors Anaheim Automation has to offer, and are already attached to the rear of the servo motors. The brakes for the servo motors have a low voltage design for applications that are susceptible to weak batter, brown out, or long wiring runs. When electric power is applied to the brake of the servo motors the armature is pulled by the electromagnet force in the magnet body assembly, which overcomes the spring action. This allows the friction disc to rotate freely. When electrical power is interrupted, the electromagnetic force is removed and the pressure spring mechanically forces the armature plate to clamp the friction disc between itself and the pressure plate.

Anaheim Automation's servo motors are designed with a 2500 counts per revolution quadrature encoder, with a resolution of 10,000 pulses per revolution.

Anaheim Automation's servo motors come with all the necessary connectors to connect to another company's servo driver or an Anaheim Automation servo driver. These connectors for servo motors can also be purchased separately if they are lost. Please refer to the user's guide for a specific part number.

The cables for servo motors can be made with the supplied servo motor connector, or can be purchased from Anaheim Automation. The cable for use with servo motors comes with a standard length of 5M but can be adjusted to any length required.

Anaheim Automation offers a variety of options to customize servo motors. This list includes, but is not limited to: shaft, brake, oil seal for an IP65 rating, mounting dimensions, speed, torque, and voltage. Please give Anaheim Automation a call for any custom applications where servo motors are used.

The steam engine governor is considered the first powered feedback system that used a gain value so it is considered the first servo mechanism. The word servo motors comes from the French phrase "Le Servomoteur" or the "slave motors". The first known record of its use was by JJL Farcot in 1868 to describe steam engines and hydraulics for use in steering a ship.

Anaheim Automation offers a wide variety of standard and Servo Motors. Occasionally, OEM customers with mid to large quantity requirements prefer to have Servo Motors that are custom or modified to meet their exact design requirements. Sometimes the customization is as simple as shaft modification, brake, oil seal for an IP65 rating, mounting dimensions, wire colors, or label. Other times, a customer might require that Servo Motors meet an ideal specification such as, speed, torque, and/or voltage. Engineers appreciate that Anaheim Automation’s Servo Motors product line can answer their desire for creativity, flexibility and system efficiency. Buyers appreciate the simplicity of the "one-stop shop," and the cost savings of custom Servo Motors design, while engineers are pleased with Anaheim Automation's dedicated involvement in their specific servo motor system.

Anaheim Automation’s standard Servo Motors product line is a cost-effective solution, in that they are known for their rugged construction and excellent performance. A considerable size of its sales growth has resulted from dedicated engineering, friendly customer service and professional application assistance, often surpassing the customer's expectations for fulfilling their custom requirements. While a good portion of Anaheim Automation's Servo Motors sales involves special, custom, or private-labeling requirements, the company takes pride in its standard stock base located in Anaheim, California, USA. To make customization of Servo Motors affordable, a minimum quantity and/or a Non-Recurring Engineering (NRE) fee is required. Contact the factory for details, should you require custom Servo Motors in your design.
All Sales for customized or modified Servo Motors are Non-Cancelable-Non-Returnable, and a NCNR Agreement must be signed by the customer, per each request. All Sales, including customized Servo Motors, are made pursuant to Anaheim Automation’s standard Terms and Conditions, and are in lieu of any other expressed or implied terms, including but not limited to any implied warranties.
Anaheim Automation's customers for the Servo Motors product line is diverse: companies operating or designing automated machinery or processes that involve food, cosmetics or medical packaging, labeling or tamper-evident requirements, cut-to-length applications, assembly, conveyor, material handling, robotics, special filming and projection effects, medical diagnostics, inspection and security devices, pump flow control, metal fabrication (CNC machinery), and equipment upgrades. Many OEM customers request that we “private-label” the Servo Motors, so that their customers stay loyal to them for servicing, replacements and repairs.

A servomechanism may or may not use a servo motor. For example, a household furnace is a servomechanism that is controlled by a thermostat. Once a set temperature is reached, there is feedback signaling it to shut off; making it a “servo” in nature. The term “servo” describes more of a function or task, than it does a specific product line. For this guide, we will discuss servo motors specifically.

Servo motors are seen in applications such as factory automation, robotics, CNC machinery, and packaging. The feedback lets the drive know its position, speed, and torque to detect unwanted motion. Pharmaceutical industries are driven be the need to create smaller devices; ones that are easier to operate and function more efficiently.

Since there may be a variety of servo motors that meet the required inertia ratio specifications, the next step is to find the smallest, most cost-effective servo motor that will meet the speed and torque demands. Servo motor manufacturers normally provide speed-torque curves for each series of motors, which illustrate several interesting points of the servo motor’s characteristics. The speed-torque curve contains two regions; continuous and intermittent, which can translate to correct match or incorrect match (respectively) for the application. If the speed-torque required for a specific application falls into the continuous region of the speed-torque curve, then that motor can produce that torque and speed without overheating. If the speed-torque required for the application falls into the intermittent region of the speed-torque cure, then that motor can only produce that speed and torque for a limited amount of time before overheating.

Servo motors operate on negative feedback, meaning that the control input is closely compared to the actual position via a transducer. If there is any variance between physical and wanted values, an error signal is amplified, converted, and used to drive the system in the direction necessary to reduce or eliminate error. Servo motors are controlled by a pulse of variable width that is sent from a micro-controller output pin to the servo motor’s control wire. The shaft angle is determined by the duration of the pulse, also known as pulse width modulation (pwm). This pulse has to have specific parameters such as; minimum pulse, a maximum pulse, and a repetition rate. Given these constraints, neutral is defined to be the position where the servo has exactly the same amount of potential rotation in the clockwise direction as it does in the counter clockwise direction. It is important to note that different servo motors will have different constraints on their rotation, but they all have a neutral position, and that position is always around 1.5 milliseconds (ms).

Anaheim Automation offers AC Servo Drives providing high speed DSP. These servo motors are equipped with auto disturbance rejection control and speed observation control algorithm, in addition to compensation servo delays, forward feed control, and reference smoothing techniques. Anaheim Automation Servo Drives are equipped with a range of dynamic features including: High Overload Capacity The industrial grade Intelligent Power Modules (IPM) utilized in the EDB/EDC AC Servo Drives are one step higher in capacity than other servo products that are specified at the same power. Communication Interface Standard CAN bus interfaces are available in the EDC AC Servo Driver, simplifying the integration process. Based on Modbus protocols from either RS485 or RS232 interfaces, up to 32 servo motors can be connected together. When RS485 interface is used, the transmission distance can reach up to 4000 feet. Anaheim Automation AC Servo Drivers can also communicate with a PLC, DCS, intelligent instruments, touch screens, and more.

Anaheim Automation offers AC Servo Drives providing high speed DSP. These servo motors are equipped with auto disturbance rejection control and speed observation control algorithm, in addition to compensation servo delays, forward feed control, and reference smoothing techniques. Anaheim Automation Servo Drives are equipped with a range of dynamic features including: High Overload Capacity The industrial grade Intelligent Power Modules (IPM) utilized in the EDB/EDC AC Servo Drives are one step higher in capacity than other servo products that are specified at the same power. Communication Interface Standard CAN bus interfaces are available in the EDC AC Servo Driver, simplifying the integration process. Based on Modbus protocols from either RS485 or RS232 interfaces, up to 32 servo motors can be connected together. When RS485 interface is used, the transmission distance can reach up to 4000 feet. Anaheim Automation AC Servo Drivers can also communicate with a PLC, DCS, intelligent instruments, touch screens, and more. ESView Communication Software Anaheim Automation software is capable of the following: Parameter Management - Fast and convenient operations to all parameters available, including editing, transmission, comparison, and initialization. Monitoring - Real time monitoring of all I/O signals, alarms of the present and history records, and system status Real Time Management - Real time sampling of the torque vs. speed curves for simple, rapid analysis. Adjusting - Quick adjustment of gains.

There are two main types of Servo Motors: Rotary and Linear. Rotary Servo Motor A rotary Servo Motor is what most people think of when they think of a Servo Motor. The three types of Rotary Servo Motors are: AC Servo Motor, Brush DC Servo Motor, and Brushless DC Servo Motor. The motion of a rotary Servo Motor is often converted into linear motion by the use of a screw thread (ball screw or lead screw), or with the use of belts and pulleys. A Rotary AC Servo Motor is an AC type motor that is used with a feedback device. These are typically used in smaller applications, because a large AC Servo Motor is typically inefficient when compared to its DC or Brushless counterparts. Linear Servo Motor A linear Servo Motor is a flattened out Servo Motor where the rotor is on the inside, and the coils are on the outside of a moveable u-channel. Both Servo Motor types are becoming more popular as Servo Motor prices continue to come down.

A rotary Servo Motor is what most people think of when they think of a Servo Motor. The three types of Rotary Servo Motors are: AC Servo Motor, Brush DC Servo Motor, and Brushless DC Servo Motor. The motion of a rotary Servo Motor is often converted into linear motion by the use of a screw thread (ball screw or lead screw), or with the use of belts and pulleys. A Rotary AC Servo Motor is an AC type motor that is used with a feedback device. These are typically used in smaller applications, because a large AC Servo Motor is typically inefficient when compared to its DC or Brushless counterparts.

Anaheim Automation provides many different accessories for its Servo Motor product line. These accessories include brakes, encoders, connectors, cables and a handheld interface unit, as well as a full line of servo motor drives. The Servo Motor brake is a 24VDC system. These Servo Motor brakes are perfect for holding applications and are available for Anaheim Automation Servo Motors. They can be purchased separately or are attached to the rear of the Servo Motor. The Servo Motor brakes have a low voltage design for applications that are susceptible to weak batter, brown out, or long wiring runs. When electric power is applied to the Servo Motor brake, the armature is pulled by the electromagnet force in the magnet body assembly, which overcomes the spring action. This allows the friction disc to rotate freely. When electrical power is interrupted, the electromagnetic force is removed and the pressure spring mechanically forces the armature plate to clamp the friction disc between itself and the pressure plate.

Anaheim Automation provides many different accessories for its Servo Motor product line. These accessories include brakes, encoders, connectors, cables and a handheld interface unit, as well as a full line of servo motor drives. Anaheim Automation's Servo Motor is designed with a 2500 counts per revolution quadrature encoder, with a resolution of 10,000 pulses per revolution. Anaheim Automation's Servo Motor comes with the necessary connectors to connect to another companys servo drive or an Anaheim Automation servo drive. These Servo Motor connectors can also be purchased separately should they become lost. Please refer to the servo motor users guide for a specific part numbers. Servo Motor cables can be made with the supplied Servo Motor connector, or can be purchased from Anaheim Automation. The Servo Motor cable comes with a standard length of 5M but can be adjusted to any length required. NOTE: Anaheim Automation strongly recommends the purchasing of the cables with servo motors and drives to ensure cable integrity. These cables are perfectly matched and a stable form of connection.

Anaheim Automation provides many different accessories for its Servo Motor product line. These accessories include brakes, encoders, connectors, cables and a handheld interface unit, as well as a full line of servo motor drives. Anaheim Automation's Servo Motor is designed with a 2500 counts per revolution quadrature encoder, with a resolution of 10,000 pulses per revolution. Anaheim Automation's Servo Motor comes with the necessary connectors to connect to another company's servo drive or an Anaheim Automation servo drive. These Servo Motor connectors can also be purchased separately should they become lost. Please refer to the servo motor users guide for a specific part numbers. Servo Motor cables can be made with the supplied Servo Motor connector, or can be purchased from Anaheim Automation. The Servo Motor cable comes with a standard length of 5M but can be adjusted to any length required. NOTE: Anaheim Automation strongly recommends the purchasing of the cables with servo motors and drives to ensure cable integrity. These cables are perfectly matched and a stable form of connection.

Why So Many Electrical Safety Requirements when Working with a Servo Motor? Organizations, such as the Standard for Electrical Safety Requirements for Employee Workplaces, outlines the steps companies must take to be in federal compliance with safety. They include: 1. A safety program with defined responsibilities 2. Calculations for the degree of an arc flash hazard 3. Electrical safety equipment for workers 4. Training for workers 5. Electrical safety tools 6. Electrical safety labels on equipment An emphasis on safety is largely due to the fear of what an arc flash can do. An arc flash is a short circuit through the air that can happen when conductors can't support the voltage. An arc flash can be as hot as 5,000 F and creates a brilliant flash of light and loud noise. As radiant energy explodes out of the electrical equipment, hot gases and melted metal can endanger human life. This is why there are four separate industry standards or electrical safety requirements in place to protect workers against arc flashes and electrical safety equipment on the market in the form of boots, suits, gloves and more. It is the responsibility of the installer/user of servo motors and drives, and all other Anaheim Automation products, to become familiar with all safety requirements.

Surge-Suppression – General Practices when Working with a Servo Motor Transient Electromagnetic Interference (EMI) can be generated whenever inductive loads such as relays, solenoids, motor starters, or servo motors are operated by “hard contacts” such as pushbutton or selector switches. The wiring guidelines are based on the assumption that you guard your system against the effects of transient EMI by using surge-suppressors to suppress transient EMI at its source. Inductive loads switched by solid-state output devices alone do not require surge-suppression. However, inductive loads of AC output modules that are in series or parallel with hard contacts require surge-suppression to protect the module output circuits as well as to suppress transient EMI.

EMI – Electromagnetic Interference Electromagnetic Interference is the radiation or induction of electromagnetic noise on a servo motor system or machine. Servo motors, and motors in general, are a common source of EMI, due to their electromagnetic circuit components. An electromagnetic disturbance which may degrade the performance of equipment (device, system or sub-system), or causes malfunction of the equipment, is called electromagnetic interference (EMI). Servo motors are potential sources of noise and can generate common-mode currents. EMI can result in degraded servo motor system performance and/or data corruption. When it is very strong, it can cause the system to fail completely. EMI can be radiated or conducted comes from magnetic and electrical sources, respectively. In the case of most servo motors, both radiated and conducted emissions are present.

Causes of Servo Motor EMI – Typical sources of servo motor EMI Industrial – ARC welding, servo motors, computers, fast-switching digital devices, Integrated Circuits, power cords Military - Aircraft navigation and equipment Household – Refrigerators, washers, dryers, dishwashers, electric shavers, personal computers, air-conditioning and heating systems Susceptible to EMI – Can cause poor functioning and/or damage Communication receivers, microprocessors, industrial drives and controls, medical devices, household appliances EMC – Electromagnetic Compatibility Electromagnetic Compatibility is the practice of monitoring and reducing unwanted servo motor EMI. Electromagnetic compatibility is a near-perfect state in which a receptor (device, system, or sub-system) functions well in a common electromagnetic environment, without introducing intolerable electromagnetic disturbance to any other devices, equipment or systems that share that environment. IMPORTANT NOTE: EMC performance concerns the complete servo motor and drive system, as well as all other motion control systems and machinery. Therefore it is the responsibility of the OEM (original equipment manufacturer) to monitor and reduce undesirable EMI, and not of those who supply motion control products. There are often varying regulations on EMC, depending on the purpose of the system and the country it is used or sold.

Servo Motor EMI Reduction Techniques for Servo Motors to Improve a System's EMC Performance. Arcing (sometimes referred to as arc discharge or voltaic arc) is an electrical characteristic where current can flow through the air, or other normally non-conductive materials. You may have seen instances of arcing between two wires, or on the power rails of trains or trams. This is not to be confused with an electrical spark, as an electrical arc is continuous, however they do look similar. Whilst arcing can be useful, used in both welding and strip lighting, in some cases it can be a source of EMI. For Example: With DC motors, arcing can be common because of the periodic interruption of the current in the rotor windings. This very high-frequency spectra content, which can appear as wideband noise superimposed onto other signals. DC motors also provide paths for common-mode currents through their frames. Another example of radiated and conducted emissions can come from the driver circuit. A typical H-bridge circuit should ideally provide a constant current to the servo motor, but this current has fast rise time spikes due to the fast and frequent switching of the current in the driver circuit. Another significant problem is when the motor is located far from the servo driver, as this creates a fairly large loop area between servo motor leads and device frame. The radiation potential is a direct function of the loop area; the larger the loop, the larger the emissions.

Standard Components The easiest solution is to place a ceramic capacitor between the servo motor terminals, as close as possible to the servo motor. This is known as a decoupling capacitor, and reduces servo motor EMI by removing some of the high frequency noise signals. The common value used for these decoupling capacitors is between 100pF and 100nF, depending on the size of the servo motor. IMPORTANT NOTE: EMC is an important field in electronics with strict regulations, and servo motors and their circuits are significant sources of EMI. It is therefore essential that engineers take the appropriate actions to reduce EMI improve EMC as much as possible.

Servo Motors are not prone to wear over time, and therefore require little maintenance. However, periodic maintenance checks should be performed so that the servo motor keeps running like new. Upon first arrival of the servo motor one should double-check the following: the servo motor is the correct model, servo motor does not have any visible damage, shaft can be rotated by hand, the brake works correctly, and there are no loose bolts. Operators should periodically check the servo motor for vibration and noise while the motor is not rotating, rotating at low speeds, and accelerating and decelerating. Inspect the servo motor for scratches or cracks on the motor casing. If crevices or cracks are found on the servo motor, action should be taken immediately by repairing or replacing the damaged unit. Check the motor casing for oil or cutting fluid because this can corrode the coating – possibly leading to future failure. Use an insulation level tester to check insulation resistance between motor coil and servo motor frame and refer to the owner’s manual to see if insulation value falls within an operable range. Observe the normal voltage waveforms on an oscilloscope periodically and take notes for future comparison purposes and report any inconsistencies to manufacturer. Check cables and wiring for cracks and frays. Replace if found worn, as this could be dangerous (See the Wiring section in this guide for more details).

Linear Tables are controlled by one of various types of motors, along with drivers and controllers. Selecting the correct motor and driver is the key to determining how the system will operate. The first step is to determine whether a linear motor or a rotary motor is preferred to drive the system. Each motor has its own advantages and disadvantages; selection should be based upon system parameters. Linear servo motors are typically chosen because they tend to be more reliable than a brushless motor; however they are also a bit more costly. When it comes to selecting a rotary motor for an application, there are several selection options; stepper, brushless, brushed or servo - all of which offer various speed, torque and lifetime options. Generally Linear Tables are controlled with a controller that has a dedicated program running at all times which can receive feedback, analyze feedback, and make decisions based on the feedback. Various other components can decide which movement to do next such as home switches, proximity sensors, and infrared sensors.

A Linear Table is controlled by one of various types of motors, along with drivers and controllers. Selecting the correct motor and driver is the key to determining how the system will operate. The first step is to determine whether a linear motor or a rotary motor is preferred to drive the system. Each motor has its own advantages and disadvantages; selection should be based upon system parameters. Linear servo motors are typically chosen because they tend to be more reliable than a brushless motor; however they are also a bit more costly. When it comes to selecting a rotary motor for an application, there are several selection options; stepper, brushless, brushed or servo - all of which offer various speed, torque and lifetime options. Generally a Linear Table is controlled with a controller that has a dedicated program running at all times which can receive feedback, analyze feedback, and make decisions based on the feedback. Various other components can decide which movement to do next such as home switches, proximity sensors, and infrared sensors.

A Linear Stage is controlled by one of various types of motors, along with drivers and controllers. Selecting the correct motor and driver is the key to determining how the system will operate. The first step is to determine whether a linear motor or a rotary motor is preferred to drive the system. Each motor has its own advantages and disadvantages; selection should be based upon system parameters. Linear servo motors are typically chosen because they tend to be more reliable than a brushless motor; however they are also a bit more costly. When it comes to selecting a rotary motor for an application, there are several selection options; stepper, brushless, brushed or servo - all of which offer various speed, torque and lifetime options. Generally a Linear Stage is controlled with a controller that has a dedicated program running at all times which can receive feedback, analyze feedback, and make decisions based on the feedback. Various other components can decide which movement to do next such as home switches, proximity sensors, and infrared sensors.

Table Slides are controlled by one of various types of motors, along with drivers and controllers. Selecting the correct motor and driver is the key to determining how the system will operate. The first step is to determine whether a linear motor or a rotary motor is preferred to drive the system. Each motor has its own advantages and disadvantages; selection should be based upon system parameters. Linear servo motors are typically chosen because they tend to be more reliable than a brushless motor; however they are also a bit more costly. When it comes to selecting a rotary motor for an application, there are several selection options; stepper, brushless, brushed or servo - all of which offer various speed, torque and lifetime options. Generally Table Slides are controlled with a controller that has a dedicated program running at all times which can receive feedback, analyze feedback, and make decisions based on the feedback. Various other components can decide which movement to do next such as home switches, proximity sensors, and infrared sensors.