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. Although it’s possible to buy the servo drive, servomotor, and planetary gearbox from different suppliers, it’s not recommended as this requires a great deal of research, design, and analysis to ensure all components work together properly. Their closed-loop positioning capability also far exceeds typical positioning capabilities of variable speed motors and drives. The software will point to the optimum motor, and allow the user to choose from the list. Gearboxes also lower the reflected inertia of the load by an amount equal to the square of the gear ratio. The system resolution can be calculated with digital drive command schemes and should be checked to ensure it meets overall system accuracy requirements. It consists of a motor coupled to a sensor for position feedback. Servo systems include three primary components: a motor, a drive (also referred to as an amplifier), and a feedback mechanism. Most servos measure the angle of their output shaft using a potentiometer. 0000039411 00000 n 0000044267 00000 n 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 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. 0000008857 00000 n 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. His 30 years of experience in the industrial automation field include designing, building, and commissioning multi-axis servo systems. David P. Anderson . It makes sense because the signals of on/off are being sent more frequently compared to analog. 0000018032 00000 n This is referred to as torque constant ( K t ) and can be found on a motor’s data sheets. For high-performance systems, the reflected inertia of the load including any gearbox and actuator inertia should be kept as low as possible—ideally a 1:1 match to the inertia of the motor—but often acceptable performance can be achieved with inertia mismatch as high as 5:1 or even 10:1. DC servo motor adopts trapezoidal wave control, which is relatively poor. The smaller the servo, the harder it is to achieve the tight tolerances required for high accuracy. 0000003398 00000 n 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. Chip McDaniel works in technical marketing for AutomationDirect and graduated from Georgia Tech with a degree in industrial design. Servo systems are used to control a load. The servo understands the language of pulse position modulation. 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). Unlike DC motors, to control servo motor PWM signal is used. 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. When properly specified, designed, installed, tuned, and programmed, servo systems can provide accurate, repeatable operation for many years. With a suitable servo system and actuator selected, a motion controller and related software for tuning and control can be specified. 0000007200 00000 n 0000010099 00000 n The resulting list of available systems includes pricing information, a factor often critical to the selection process. The servo motor can be moved to a desired angular position by sending PWM (pulse width modulated) signals on the control wire. 2) AC Servo Motor. 0000015198 00000 n 0000004994 00000 n It also requires a servo drive to complete the system. Designers enter speed data as discrete values or pick a gear ratio. Careful selection of servomotors, machine actuators, and related components provides precise accuracy in motion control applications. With closed-loop feedback, servo motors deliver high accuracy positioning coupled with better speed and acceleration than stepper motors. How a Servo Motor Works. 0000012556 00000 n Most precision gearboxes have very low backlash, but designers need to be aware and plan for resulting positional errors. 0000002202 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. %PDF-1.7 %���� 0000038250 00000 n When using an external motion controller as the master, multiple drives can be daisy-chained and addressed separately using the drive’s serial port. To determine positional accuracy at speed, we must consider both the inherent electromechanical errors shown above, plus the rotor lag angle. 0000012469 00000 n 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. 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. Improving Servo Positioning Accuracy . Finally, the engineer can choose a preferred physical orientation: inline, right-angle gearing, or both. Brushless servo motor in DC servo motor has better performance than brush servo motor. The trade-off is increased cost, size, and complexity. The type of actuator and even the actuator material selection must be carefully considered. 0000008271 00000 n Search Products And Discover New Innovations In Your Industry. 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. A servo motor is a rotary actuator that allows for precise control of angular position. 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). Medium-inertia, high-accuracy and high-speed motors Sensor resolution has been signi cantly improved. 0000018809 00000 n 0000007737 00000 n 0000031453 00000 n True, you won't have a very high degree of accuracy or repeatability, but depending on the application it could be more than enough. Many applications benefit from adjusting the acceleration and selecting an S-curve motion profile as this can reduce positional overshoot during a move. Product Features Drives can also be controlled by high-speed pulse and direction signals, or by an analog voltage proportional to velocity or torque. Servos operate accurately at speeds up to 5,000 rpm or more. 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. 0000039731 00000 n Once modeled, the software can recommend the optimal motor for a given mechanical arrangement. Depending on your torque, speed, and angle requirements, you could also consider gearing this down further to get more accurate resolution. 0000036159 00000 n SureStep motion control line expands AutomationDirect stepper systems, Migrating legacy PLC programs to modern PLC hardware, Implementing secure remote access and MES, How air casters integrate CNC machining and business operations, Artificial intelligence at the edge improves manufacturing productivity, Cybersecurity strategies need to be measured, Pandemic transforms the system integration industry. The servo motor families offer Smart Motor Technology to provide automatic identification of correct motor-to-drive connectivity, and seamlessly integrated with Kinetix® servo drive for optimal system performance. 0000005306 00000 n Whether it’s an external motion controller or an internal motion control drive, the motion software and its features and functions have a significant effect on overall system accuracy. Commands are executed and the position control loop is closed internally at the drive. Servo motors can be of different types on the basis of their applications. RS485/RS422 and Modbus serial communication are typical protocols used to send motion commands to the drive. Medium-inertia, high-accuracy and high-speed motors Sensor resolution has been significantly improved. Software can calculate the torque, speed, and inertia requirements according to the user’s application specification; process motor data from a database; and create a list that matches the requirements. If you need something more heavy-duty, there are many other servos in the Dynamixel Series. The efficiency of a servo motor is simply how much current it takes to deliver its constant torque. 0000014448 00000 n 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. 0000010431 00000 n 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. In motion control applications where precision is required, a host of servomotors and machine actuators are available to fit the bill—but selection, design, and integration of the complete motion control system are critical for repeatable and precise motion. 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. 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