One application allows designers to select the optimum motor for a specific application. The working principle of servo motor driver. The servo motors, which boast smooth rotation and outstanding acceleration capabilities, are well-suited to serve as feed axes of machine tools. 0000010770 00000 n Typical servo systems for machine control also provide a broader range of power, up to 3 kW or more, than stepper motors. Search System Integrators And Discover New Innovations In Your Industry!! More advanced selector tools are available to assist with servomotor selection. 0000010431 00000 n When high dynamic responses are required, careful tuning of the servo system is needed, preferably with loads attached. Servo motors are typically used in packaging, converting, web processing, and similar applications. A servo motor is a rotary actuator that allows for precise control of angular position. 0000016747 00000 n 0000044267 00000 n Ac servo motor adopts sine wave control, with small torque ripple and large capacity. The servo motor can be moved to a desired angular position by sending PWM (pulse width modulated) signals on the control wire. Components of a servo system. Servos operate accurately at speeds up to 5,000 rpm or more. Assuming the desired process can be accomplished with either a stepper or servo motor solution, with the repeatability, accuracy and flexibility requirements, for present and future needs, the remaining considerations would likely be environment, life … The drive uses the feedback sensor to precisely control the rotary position of the motor. Compared to ac and dc motors operated with variable speed drives, servo systems have a clear advantage with respect to speed, high peak torque, and acceleration. Online tools for selecting servo systems and compatible gearboxes are provided by some suppliers, simplifying the design effort. Although some stepper packages take advantage of closed loop control, accurate and high-speed motion profiles without the motor stalling and the related position error is a common advantage of servomotors. 0000007737 00000 n Different Types of Servo Motors: DC Servo Motor and AC Servo Motor In simple words, the servo motor is an individual electric motor . 0000008271 00000 n Eight critical components for precision motion control are: The servomotor, encoder feedback, and servo drive, sometimes called an amplifier, must be designed to work together as a package, and carefully matched to the motor and load. 0000014448 00000 n These selector tools typically let designers enter their speed and torque requirements, and then automatically provide a list of available motor-and-gearbox combinations. 0000039731 00000 n Chip McDaniel works in technical marketing for AutomationDirect and graduated from Georgia Tech with a degree in industrial design. 0000035839 00000 n A typical servo motor comprises of three wires namely- power, control, and ground. The most important amongst them are : AC servo motor, DC servo motor, brushless DC servo motor, positional rotation servo motor, continuous rotation servo motor, and linear servo motor. Medium-inertia and high-accuracy servo motor; Optimal for ensuring the accuracy of a machine with high-inertia. When a step motor is driven open loop, the stator field is rotated by the driver, and, if the laws of physics are not violated by expecting more torque than the motor can deliver, the rotor follows. 0000001516 00000 n For applications requiring precision control of motion, a variety of options are available including ac and dc motors with variable speed drives, stepper motors, and servomotors (Figure 1). In the event a reversing move is required, some designers move the load past the desired position and then return to that position from the common direction. 204 0 obj <> endobj xref 204 61 0000000016 00000 n Howdy SRS, I have documented a technique for improving the accuracy and repeatability of servo positioning by use of an external reference potentiometer. The servo system needs to be able to provide the required torque, speed, and accuracy for the entire system to perform as designed. A servo motor is a DC motor integrated with a gear train, a shaft encoder, and some control logic so that it is easier to use. The old-school analog voltage command may not be as accurate as the newer digital control methods such as internal control, or external pulse and direction signals. The drive and servomotor can also follow an external encoder signal. When your application is forgiving but your budget is not, consider a stepper motor. Servo systems can also operate in a pure-torque mode where the system provides a specific amount of torque without regard to position or speed. 0000008857 00000 n 0000031132 00000 n Closed-loop position control, higher torque and higher speeds of the servomotor all confer benefits in high-accuracy applications. Engineers can enter torque data in metric or imperial values, or the designer can select a particular servomotor size. Medium-inertia, high-accuracy and high-speed motors Sensor resolution has been significantly improved. Brushless servo motor in DC servo motor has better performance than brush servo motor. To achieve maximum performance, all servo systems need tuning at initial power-up along with proper software configuration and programming. Their closed-loop positioning capability also far exceeds typical positioning capabilities of variable speed motors and drives. The trade-off is increased cost, size, and complexity. David P. Anderson . The rotor of a servo motor uses permanent magnets and can be infinitely positioned between magnetic poles on the stator by varying the voltage and current between windings. Could software help? 0000009357 00000 n 0000013641 00000 n With a suitable servo system and actuator selected, a motion controller and related software for tuning and control can be specified. Properly selected servo systems, gearboxes, and actuators can be used to solve a wide range of precision automation challenges. Many components are specified, designed, installed, and tested to create a servo system. Servo systems include three primary components: a motor, a drive (also referred to as an amplifier), and a feedback mechanism. For example, a frequent method used to minimize backlash and its related positional error is to approach all target positions from a common direction. See the motors and drives page here and related articles below. After choosing a motor/gear combination, the designer can view full specifications for the selected servo system, the gearbox, and the combination. Product Features 0000015198 00000 n A servo motor, then, is one that incorporates a feedback device (such as a resolver or encoder) whose output is compared to the command signals sent to the motor by the controller. Range 0.5 to 11 [kW] Maximum speed 3,000 [r/min] Adaptable to both standard detector at 100,000 p/rev and high-accuracy detector at 1 million p/rev. DC servo motor adopts trapezoidal wave control, which is relatively poor. Depending on your torque, speed, and angle requirements, you could also consider gearing this down further to get more accurate resolution. There are multiple ways to control a servo drive from an external controller. The resulting list of available systems includes pricing information, a factor often critical to the selection process. 0000001985 00000 n When properly specified, designed, installed, tuned, and programmed, servo systems can provide accurate, repeatable operation for many years. Servo motors are a better choice for systems requiring high speed, high acceleration, and high accuracy. In some applications, for example, an aluminum lever actuator might flex too much for accurate motion, so stiffer materials or structural bracing should be considered. The software will point to the optimum motor, and allow the user to choose from the list. The type of actuator and even the actuator material selection must be carefully considered. The smaller the servo, the harder it is to achieve the tight tolerances required for high accuracy. 0000015978 00000 n 0000037599 00000 n 0000004588 00000 n 0000031954 00000 n To achieve maximum performance, all servo systems need tuning at initial power-up along with proper software configuration and programming. This problem originated when we were developing a two-axis head for a video camera mounted on our remotely piloted vehicle. In this case there is a few disadvantages: 1) Limitation of speed like 1Mpps(Pulse Per Second) 2) Not strong enough When deciding on a servo system for a new application, sizing software is often used. Perhaps the most notable difference between steppers and servomotors is that servomotors improve positioning with closed loop control. If an application can handle the reduction in top speed, a gearbox can be a great way to improve the overall performance of the system. 0000005306 00000 n Servo motor receives a control signal that represents an output position and applies power to the DC motor until the shaft turns to exact position, determined by the position sensor. 0000041999 00000 n For the servo to do this properly per the system requirements, it must be appropriately sized. Figure 8.62 shows a servo with the lid removed to reveal the gears. Servo Accuracy By High Speed Network For a long time, control command of a servo motor was sent by analogue voltage command or pulse train command from master controller. While servomotors have many advantages over competing technologies, a number of factors must be considered. It makes sense because the signals of on/off are being sent more frequently compared to analog. The type of load, the mechanical transmission, the duty cycle of the system (how often it starts and stops), how fast the system needs to go during operation, and how accurate the system needs to be all play a part in deciding what system should be selected. The servo motors, which boast smooth rotation and outstanding acceleration capabilities, are well-suited to serve as feed axes of machine tools. Finally, the engineer can choose a preferred physical orientation: inline, right-angle gearing, or both. 0000002202 00000 n When replacing an existing servo system, the same power size can usually be selected, even though the motor may be a different physical size. Most servo systems can accept traditional motion commands from external controllers such as programmable logic controllers (PLCs) and programmable automation controllers (PACs), and some drives also have the ability to provide their own internal motion control. Once the drive is configured and tuned, the type of motion profile can be programmed. RS485/RS422 and Modbus serial communication are typical protocols used to send motion commands to the drive. This motor can be placed to high accuracy and also controlled precisely as compulsory for the applications. Typical applications for high-precision servo system motion control include press feeds, auger fillers, rotary tables, robots for pick-and-place, test or assembly operations, boring, drilling, cutting, tapping, and similar applications using simple index moves for single or multi-axis motion. 0000011097 00000 n In this case there is a few disadvantages: 1) Limitation of speed like 1Mpps(Pulse Per Second) 2) Not strong enough for noise environment. 0000037906 00000 n Whether it is a single-axis or multi-axis system, the requirements for the motion profile such as maximum velocity, acceleration, jerk (change in acceleration), total distance, and deceleration must all be carefully reviewed for a successful application. 0000033864 00000 n Sometimes the control sequence of the actuator affects accuracy. Search Products And Discover New Innovations In Your Industry. His 30 years of experience in the industrial automation field include designing, building, and commissioning multi-axis servo systems. A pulse of width varying from 1 millisecond to 2 milliseconds in a repeated time frame is sent to the servo for around 50 times in a second. With closed-loop feedback, servo motors deliver high accuracy positioning coupled with better speed and acceleration than stepper motors. Compared to lower cost stepper motor systems, servo systems provide more torque at higher speeds, up to 5,000 rpm. 0000045248 00000 n In some applications, using a gearbox to multiply the system’s available torque can allow the use of a smaller motor and drive—a big cost saver. Generally I work with precisions of 20 micron or less, this application is only about 800 micron of positioning accuracy. 0000031453 00000 n It regulates the speed of the motor by simply sending on and off pulses. I have worked a great deal designing PM synchronous servo motors and their systems. 0000009110 00000 n Using software, a design engineer can model the mechanical systems including lead screws, timing belts, gearboxes, and so forth. Medium-inertia, high-accuracy and high-speed motors Sensor resolution has been signi cantly improved. This allows for very simple yet powerful control of multi-axis processes not needing precise path control, but only exact starting and stopping points (Figure 3). It consists of a motor coupled to a sensor for position feedback. %PDF-1.7 %���� Iron core linear motors are best suited for applications that require extremely … ���qp2}8#�z�+c�& ǃ��&��gD-��:أSf����ZFv��2:�L&%%%0�< X� ����8�F�A���Aāy ��).��ö�A�Aށ��/��� ��:m�9�z F�{��(;�p0�d�y@� K�����LX��6�0&. Improving Servo Positioning Accuracy . 0000010099 00000 n With a servo drive and an internal "indexer," up to eight index moves can be pre-defined and stored in the drive, and then selected and executed using discrete input signals from a PLC or PAC. The encoder and controller of a servomotor are an additional cost, but they optimise the performance of the overall system (for all of speed, power and accuracy) relative to the capacity of the basic motor. Gearboxes also lower the reflected inertia of the load by an amount equal to the square of the gear ratio. Servo motors, also known as axis or torque motors, use fewer electromagnetic poles—usually fewer than a dozen—and rely on closed-loop communication for accuracy and speed control, meaning there is a two-way signal between it and the control. – Chip McDaniel, technical marketing, AutomationDirect; edited by Mark T. Hoske, content manager, Control Engineering, mhoske@cfemedia.com. Also, the output of a 85mm frame size motor … AC Servo Motor; It delivers high power output: Delivers low output of about 0.5 W to 100 W: It has more stability problems : It has less stable problems: It requires frequent maintenance due to the presence of commutator: It requires less maintenance due to the absence of commutator: It provides high efficiency : The efficiency of AC servo motor is less and is about 5 to 20% Drives that feature on-board indexer and adaptive tuning modes must be configured properly, as must external motion controllers. 0000017268 00000 n It also requires a servo drive to complete the system. Purchasing the components from one supplier, especially one that has carefully matched the components and will stand behind the specific combination of parts, offers several advantages. Servo motors are well suited to precision to applications where accurate control of motor speed, position and/or torque is required. When using an external motion controller as the master, multiple drives can be daisy-chained and addressed separately using the drive’s serial port. 0000039411 00000 n 0000011937 00000 n Each of these methods can affect servo system accuracy. If gear reduction is required, a precision planetary gearbox provides better accuracy and repeatability compared to most other gear reducers, and its high efficiency lets it deliver the maximum power available from the servo system. 0000017062 00000 n 0000009147 00000 n 0000018032 00000 n Servo Accuracy By High Speed Network For a long time, control command of a servo motor was sent by analogue voltage command or pulse train command from master controller. How a Servo Motor Works. Deciding whether the application requires an iron core or an ironless linear motor is typically the first step in design and selection. The motion can be incremental or absolute (homing routines are available in the drive), and acceleration can be linear or S-curve. A servo motor has a 3-pin interface with power (typically 5 … This is a common requirement in various winding operations. But the gearbox will add some reflected inertia of its own to the system, and also introduce a certain amount of backlash. 0000002767 00000 n Software can calculate required speed and torque and verifies many other system requirements such as top-end speed, acceleration, and inertia mismatch. Servo systems provide the highest possible level of performance for precise control of position, velocity, and/or torque. A servo system coupled with a planetary gearbox (Figure 2) will provide accurate motion when connected to a wide range of actuator types, but only if all components are carefully specified and matched. True, you won't have a very high degree of accuracy or repeatability, but depending on the application it could be more than enough. 0000003398 00000 n With larger systems, where a powerful motor represents an increasing proportion of the system cost, servomotors have the advantage. Motor, Motor control. 0000004994 00000 n Linear direct drive servo motors come in two main types, iron core or ironless, referring to whether the windings in the primary part (analogous to the stator in a rotary motor) are mounted in an iron lamination stack or in epoxy. The servo understands the language of pulse position modulation. 0000022626 00000 n trailer <<90AF7061C4674B198CE89BECEB97CFF1>]/Prev 1273241>> startxref 0 %%EOF 264 0 obj <>stream 0000222964 00000 n It is not easy to fully grasp the whole idea unless there are comparison examples against other control motors such ... For a 42mm motor frame size, its output is equivalent to that of a servo motor with 50 to 100W. To determine positional accuracy at speed, we must consider both the inherent electromechanical errors shown above, plus the rotor lag angle. 0000003128 00000 n The rotor inside the servo motor is a permanent magnet. Most servos measure the angle of their output shaft using a potentiometer. Commands are executed and the position control loop is closed internally at the drive. h�b``Pf``;����7�A��؀�,�@�4�]�+��� dž������=�������4�f���M���L Drive configuration software can provide configuration of drive parameters and automatic tuning algorithms and tools to help find the optimal settings for most applications. Servo systems are used to control a load. Many applications benefit from adjusting the acceleration and selecting an S-curve motion profile as this can reduce positional overshoot during a move. 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