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How Servo Motors Work The "switch" of Fuji PLC is used to control the start and stop of the servo controller. The start or stop of the servo controller is to start and stop the servo motor. The control accuracy of the servo controller is higher than that of the inverter. Servo motors are generally used in occasions requiring high control accuracy (such as: speed control, position control, torque control). Fuji servo motor comes with photoelectric encoder. The rotation of the rotor drives the code disc of the photoelectric encoder. The number of turns of the rotor directly affects the number of pulses sent by the encoder to the controller. The pulses make the servo rotate, and the DO output determines the servo direction. The pulse direction controls the direction of the servo, the forward pulse servo rotates forward, and the reverse pulse servo reverses, so the Fuji servo motor combined with the servo controller can truly realize its precision control. If the servo is controlled by analog quantity, positive and negative analog quantity can be used for forward and reverse control. If using communication control, send the command directly. On the program, you can directly input the position JOG command to make it forward or reverse.

Servo motor: 6 key parameters for servo drive selection A servo system is a feedback control system used to accurately follow or reproduce a process. The servo system is an automatic control system that enables the output controlled quantities such as the position, orientation, and state of the object to follow any changes in the input target (or given value). Its main task is to amplify, transform and regulate the power according to the requirements of the control command, so that the torque, speed and position control of the drive device is very flexible and convenient. The servo driver is a part of the servo system and is used to control the servo motor. Its function is similar to that of the inverter acting on the ordinary AC motor. It is mainly used in high-precision positioning systems. Generally, the servo motor is controlled by three methods of position, speed and torque to achieve high-precision positioning of the transmission system. It is currently a high-end product of transmission technology. Selecting a suitable servo driver needs to consider various aspects, which are mainly selected according to the requirements of the system. Before selecting the type, first analyze the following system requirements, such as size, power supply, power, control method, etc., to set the direction for the selection. . Let's take a look at various parameters of the servo drive. 1. Continuous current, peak current; 2. Power supply voltage, control part supply voltage; 3. Supported motor types and feedback types; 4. Control mode, form of accepting commands; 5. Communication protocol 6. Digital IO Based on this information, we can roughly select the servo driver that matches the motor. In addition, pay attention to the working environment, temperature and humidity conditions, whether the installation is the right size, etc. The selection of the driver is not only considering whether the driver matches the motor, but also the control method. The servo drive has three control modes: position, speed and torque mode. Torque mode and speed can be set by external analog input or communication command, while position mode determines the speed and length of motion through the frequency and number of pulses. In torque mode, the motor outputs a fixed torque and cannot control the position and speed. Position mode has very strict control of speed and position, and is generally used for positioning devices. According to the needs of the system and the type of upper control, the appropriate control method can be selected. Now servo drives are becoming more and more intelligent, not only supporting various types of servo motors, but also compatible with various types of feedback, can receive analog, PWM, pulse + direction and software commands, communication supports CANopen, Ethercat, etc. Provides three-loop control and commutation functions, and intelligent one-key tuning, etc. It is very convenient to use and has high control precision, which greatly improves the performance of the system and saves a lot of time for developers.

Modern AC servo systems, after undergoing changes from analog to digital, have their internal digital control loops ubiquitous, such as commutation, current, speed and orientation control, etc.; Functional DSP plus FPGA, and even servo-specific modules are also rudimentary. In addition, new power devices or modules are updated every 2 to 2.5 years, new software algorithms are also changing with each passing day, and the servo products of international manufacturers are also updated about every 5 years. In short, the product life cycle is getting shorter and shorter. , changing faster and faster. Summarizing the technical road and product road of domestic and foreign servo manufacturers, and contacting the changes in market demand, we can see the latest development trends of the following servo motor systems: high efficiency Although high efficiency has always been the primary open issue for the servo system, it still needs to be strengthened. It mainly includes the high efficiency of the motor itself: such as the improvement of the performance of permanent magnet materials and the very good structure of the magnet equipment; it also includes the high efficiency of the drive system: including the optimization of the inverter drive circuit, the optimization of the acceleration and deceleration motion, the regeneration system Dynamic and energy response and very good cooling methods etc. Direct drive Direct drive includes turntable servo drive using disc motor and linear servo drive using linear motor. Since the transmission error of the base mechanical transmission equipment is eliminated, high speed and high positioning accuracy are achieved. The simple change of the shape of the linear motor can make all kinds of equipment that use the linear linear structure realize the miniaturization and light weight. High-speed, high-precision, high-performance The use of higher-precision encoders, higher sampling accuracy and data bits, faster DSP, high-performance rotary motors and linear motors without cogging effects, and the use of various modern control strategies such as self-learning and artificial intelligence, Continuously improve the basic policy of the servo system. Integration and integration The vertical integration of motor, response, control, drive, and communication became an opening direction for low-power servo systems at that time. Sometimes we call this kind of motor that integrates drive and communication an intelligent motor, and sometimes we call a drive that integrates motion control and communication an intelligent servo driver. The integration of motors, drives and controls brings the three closer together from planning and manufacturing to operation and maintenance. However, this method faces greater technical challenges and the challenges of engineers' usage habits, so it is difficult to become a mainstream, and it is a small and characteristic part in all servo markets. Universal The general-purpose driver is equipped with many parameters and rich menu functions, which is convenient for users to set V/F control, speed sensorless open-loop vector control, closed-loop flux vector control, permanent magnet without changing the hardware configuration. Five operating methods, including brushless AC servo motor control and regeneration unit, are suitable for various occasions and can drive different types of motors, such as asynchronous motors, permanent magnet synchronous motors, brushless DC motors, stepper motors, and can also be used to Different sensor types do not even have an orientation sensor. A semi-closed-loop control system can be formed by using the response provided by the motor itself, or a high-precision full-closed-loop control system can be formed with an external azimuth or speed or torque sensor through the interface. Intelligent Modern AC servo drives have parameter recall, fault self-diagnosis and analysis functions. Most drives have load inertia measurement and automatic gain adjustment functions. Some can automatically identify the parameters of the motor and automatically determine the zero position of the encoder. Vibration suppression is performed automatically. Connecting control functions such as electronic gears, electronic cams, synchronous tracking, and interpolation motion with the drive provides a very good solution for servo users.

Sometimes we are easy to confuse the role of electromagnetic braking, regenerative braking and dynamic braking, and choose the wrong accessories. These concepts are clarified below. The dynamic brake is composed of a dynamic braking resistor, which shortens the mechanical feed distance of the servo motor through energy consumption braking in the event of a fault, emergency stop, or power failure. Regenerative braking means that when the servo motor decelerates or stops, the energy generated by the braking is fed back to the DC bus through the inverter circuit, and absorbed by the resistance-capacitance circuit. The electromagnetic brake is to lock the shaft of the motor through a mechanical device. The difference between the three (1) The regenerative braking must work when the servo is working normally, and the motor cannot be braked in the event of a fault, emergency stop, power failure, etc. The dynamic brake and electromagnetic brake do not need power supply when working. (2) The work of regenerative braking is carried out automatically by the system, while the work of dynamic braking and electromagnetic braking requires external relay control. (3) Electromagnetic brake is generally started after SV OFF, otherwise the amplifier may be overloaded. Dynamic brake is generally started after SV OFF or the main circuit is powered off, otherwise the dynamic braking resistor may be overheated. Notes on choosing accessories (1) Some systems such as transmission devices, lifting devices, etc. require the servo motor to stop as soon as possible. In the event of a fault, emergency stop, or power failure, the servo cannot decelerate the motor without regenerative braking. At the same time, the mechanical inertia of the system is large. At this time, the selection of the dynamic brake should be based on the weight of the load, the working speed of the motor, etc. (2) For some systems to maintain the static position of the mechanical device, the motor needs to provide a large output torque and stop for a long time. If the self-locking function of the servo is used, the motor will be overheated or the amplifier will be overloaded. In this case, choose Motor with electromagnetic brake. (3) Some servos have a built-in regenerative braking unit, but when the regenerative braking is frequent, the DC bus voltage may be too high. At this time, a regenerative braking resistor needs to be reconfigured. Whether the regenerative braking resistor needs to be reconfigured? For the size of the regenerative braking resistor, please refer to the instruction manual of the corresponding sample. It should be noted that the braking times on the general sample list is the data of the motor when the motor is no-load. In the actual selection, the load inertia of the system and the sample Calculate the inertia ratio. Then divide the braking times on the sample list by (inertia ratio + 1). The data obtained in this way is the allowable braking times.