Servo motorThe word "servo" comes from the Greek word for "slave". "Servo motor" can be understood as a motor that absolutely obeys the control signal: before the control signal is issued, the rotor is stationary; when the control signal is issued, the rotor immediately rotates; when the control signal disappears, the rotor can stop immediately. A servo motor is a micro motor used as an actuator in an automatic control device. Its function is to convert electrical signals into angular displacement or angular velocity of the rotating shaft. Servo motors are divided into two categories: AC servo and DC servo The basic structure of AC servo motor is similar to that of AC induction motor (asynchronous motor). There are two excitation windings Wf and control windings WcoWf with a phase space displacement of 90° electrical angle on the stator, which are connected to a constant AC voltage. The AC voltage or phase change applied to Wc is used to control the operation of the motor. AC servo motors have the characteristics of stable operation, good controllability, fast response, high sensitivity, and strict nonlinearity indicators of mechanical characteristics and adjustment characteristics (required to be less than 10% to 15% and less than 15% to 25% respectively). The basic structure of DC servo motor is similar to that of general DC motor. Motor speed n = E / K1j = (Ua-IaRa) / K1j, where E is armature back electromotive force, K is a constant, j is magnetic flux per pole, Ua and Ia are armature voltage and armature current, and Ra is armature resistance. The speed of DC servo motor can be controlled by changing Ua or φ, but the method of controlling armature voltage is generally adopted. In permanent magnet DC servo motor, the excitation winding is replaced by permanent magnet, and the magnetic flux φ is constant. DC servo motor has good linear regulation characteristics and fast time response. Advantages and Disadvantages of DC Servo MotorsAdvantages: precise speed control, very rigid torque-speed characteristics, simple control principle, easy to use, and cheap.Disadvantages: brush commutation, speed limitation, additional resistance, generation of wear particles (not suitable for dust-free and explosive environments) Advantages and Disadvantages of AC Servo MotorsAdvantages: good speed control characteristics, smooth control in the entire speed range, almost no oscillation, high efficiency of more than 90%, low heat generation, high-speed control, high-precision position control (depending on encoder accuracy), constant torque in the rated operating area, low inertia, low noise, no brush wear, maintenance-free (suitable for dust-free and explosive environments)Disadvantages: The control is more complicated, the drive parameters need to be adjusted on-site to determine the PID parameters, and more connections are required. DC servo motors are divided into brushed and brushless motors.Brushed motors have low cost, simple structure, large starting torque, wide speed regulation range, easy control, and require maintenance, but maintenance is convenient (replacing carbon brushes). They generate electromagnetic interference and have requirements for the use environment. They are usually used in ordinary industrial and civilian occasions that are sensitive to cost. The brushless motor is small in size and light in weight, has high output and fast response, high speed and small inertia, stable torque and smooth rotation, complex and intelligent control, flexible electronic commutation, and can be commutated by square wave or sine wave. The motor is maintenance-free, highly efficient and energy-saving, has low electromagnetic radiation, low temperature rise and long life, and is suitable for various environments. AC servo motors are also brushless motors, which are divided into synchronous and asynchronous motors. Synchronous motors are generally used in motion control. They have a wide power range, can be very powerful, have large inertia, and have a low maximum speed. The speed decreases at a uniform speed as the power increases. They are suitable for low-speed and stable operation occasions. The rotor inside the servo motor is a permanent magnet. The driver controls the U/V/W three-phase electricity to form an electromagnetic field. The rotor rotates under the action of this magnetic field. At the same time, the motor's built-in encoder transmits the feedback signal to the driver, compares the feedback value with the target value, and adjusts the angle of rotation of the rotor. The accuracy of the servo motor is determined by the accuracy of the encoder (number of lines). What is a servo motor? How many types are there? What are its working characteristics?Answer: The servo motor, also known as the actuator motor, is used as an actuator in the automatic control system to convert the received electrical signal into angular displacement or angular velocity output on the motor shaft. Servo motors are divided into two categories: DC and AC servo motors. Their main characteristics are that there is no self-rotation when the signal voltage is zero, and the speed decreases uniformly with the increase of torque. What is the difference in performance between AC servo motors and brushless DC servo motors?A: AC servo motors have better performance because they use sine wave control and have small torque pulsation, while brushless DC servos use trapezoidal wave control. However, brushless DC servos are simpler to control and cheaper. The rapid development of permanent magnet AC servo drive technology has put the DC servo system in danger of being eliminated. [/p] [p=30, 2, left] Since the 1980s, with the development of integrated circuits, power electronics technology and AC variable speed drive technology, permanent magnet AC servo drive technology has made outstanding progress, and well-known electrical manufacturers in various countries have continuously launched new AC servo motors and servo drive series products. AC servo systems have become the main development direction of contemporary high-performance servo systems, putting DC servo systems in danger of being eliminated. Compared with DC servo motors, permanent magnet AC servo motors have the following main advantages:⑴ No brushes and commutator, more reliable operation and maintenance-free.⑵The heat generation of stator winding is greatly reduced.⑶ Small inertia and good system responsiveness.⑷ High speed and high torque working condition is good.⑸ Small size and light weight at the same power.The rise and current status of permanent magnet AC servo systems Since the Indramat division of Rexroth of MANNESMANN, Germany, officially launched the MAC permanent magnet AC servo motor drive system at the 1978 World Trade Fair, it has marked the maturity of the new generation of AC servo technology. By the mid-to-late 1980s, major companies had a complete series of products, and the entire servo device market turned to AC systems. Early analog systems had deficiencies in aspects such as zero drift, anti-interference, reliability, accuracy and flexibility, and could not fully meet the requirements of motion control. In recent years, with the application of microprocessors and new digital signal processors (DSPs), digital control systems have emerged, and the control part can be completed by software. After the 1990s, the status of permanent magnet AC servo motor drive systems with full digital sine wave control in the transmission field has further increased. At present, most high-performance electric servo systems use permanent magnet synchronous AC servo motors, and the control drivers mostly use fast and accurate positioning full digital position servo systems. Typical manufacturers include Germany's Siemens, the United States' Kollmorgen, Japan's Panasonic and Yaskawa, etc. Overview of major manufacturers of permanent magnet AC servo systemsThe small AC servo motors and drivers launched by Yaskawa Electric Manufacturing Co., Ltd. of Japan, among which the D series is suitable for CNC machine tools (maximum speed of 1000r/min, torque of 0.25~2.8Nm), and the R series is suitable for robots (maximum speed of 3000r/min, torque of 0.016~0.16Nm). Later, six series, M, F, S, H, C, and G, were launched. In the 1990s, the new D series and R series were launched successively. The old series of rectangular wave driven 8051 single-chip microcomputer control was changed to sine wave driven 80C, 154CPU and gate array chip control, the torque fluctuation was reduced from 24% to 7%, and the reliability was improved. In this way, it took only a few years to form a relatively complete system of eight series (power range of 0.05~6kW), which met the different needs of working machinery, handling mechanism, welding robot, assembly robot, electronic components, processing machinery, printing machine, high-speed winding machine, winding machine, etc. Fanuc, a Japanese company famous for producing CNC devices for machine tools, also launched S series (13 specifications) and L series (5 specifications) of permanent magnet AC servo motors in the mid-1980s. The L series has a smaller moment of inertia and mechanical time constant, and is suitable for position servo systems that require particularly fast response. Other Japanese manufacturers, such as Mitsubishi Electric (*****, HC-MFS, *****, HC-RFS and HC-UFS series), Toshiba Seiki (SM series), Okuma Iron Works (BL series), Sanyo Electric (BL series), Tateishi Electric (S series) and many other manufacturers have also entered the competition of permanent magnet AC servo systems. ［/p］［p=30, 2, left］ The MAC series AC servo motors of the Indramat division of Rexroth of Germany have 7 frame sizes and 92 specifications. The IFT5 series of three-phase permanent magnet AC servo motors from Siemens of Germany are divided into two categories: standard type and short type, with a total of 8 frame sizes and 98 specifications. It is said that compared with the IHU series of DC servo motors with the same output torque, the weight of this series of AC servo motors is only 1/2 of the latter, and the matching transistor pulse width modulation driver 6SC61 series can control motors of up to 6 axes. BOSCH of Germany produces SD series (17 specifications) of ferrite permanent magnets and SE series (8 specifications) of rare earth permanent magnets AC servo motors and Servodyn SM series drive controllers. Gettys, a famous American servo device manufacturer, was once a division of Gould Electronics (Motion Control Division), producing M600 series AC servo motors and A600 series servo drives. It was later merged into AEG, restored the Gettys name, and launched the A700 fully digital AC servo system. The 1326 ferrite permanent magnet AC servo motor and 1391 AC PWM servo controller produced by the drive division of AB (ALLEN-BRADLEY) of the United States include 3 frame sizes and 30 specifications in total. ID (Industrial Drives) is the industrial drive division of the famous American Kollmorgen. It has produced 41 specifications of brushless servo motors and BDS3 servo drives in three series: BR-210, BR-310, and BR-510. Since 1989, it has launched a new series of permanent magnet AC servo motors (Goldline), including three categories: B (small inertia), M (medium inertia) and EB (explosion-proof), with five frame sizes of 10, 20, 40, 60, and 80. Each category has 42 specifications, all of which are made of neodymium iron boron permanent magnet materials, with a torque range of 0.84 to 111.2Nm and a power range of 0.54 to 15.7kW. The supporting drivers include three series: BDS4 (analog), BDS5 (digital, including position control) and Smart Drive (digital), with a maximum continuous current of 55A. The Goldline series represents the latest level of contemporary permanent magnet AC servo technology. Inland in Ireland was originally a branch of Kollmorgen abroad, and now merged into AEG. It is famous for producing DC servo motors, DC torque motors and servo amplifiers. It produces 17 specifications of SmCo permanent magnet AC servo motors with three frame sizes of BHT1100, 2200 and 3300, and eight controllers. The French Alsthom Group produces 14 specifications of LC series (long type) and GC series (short type) AC servo motors at its Parvex plant in Paris, as well as the AXODYN series drives. The former Soviet Union developed two series of AC servo motors for CNC machine tools and robot servo control. The ДBy series uses ferrite permanent magnets, has two frame sizes, each with three core lengths, two winding data, a total of 12 specifications, and a continuous torque range of 7 to 35 N.m. The 2ДBy series uses rare earth permanent magnets, 6 frame sizes and 17 specifications, with a torque range of 0.1 to 170 N.m, and is equipped with a 3ДБ controller. In recent years, Panasonic Corporation of Japan has launched the fully digital MINAS series AC servo system, among which the permanent magnet AC servo motors include the MSMA series small inertia type, with power ranging from 0.03 to 5kW, with a total of 18 specifications; the medium inertia type includes three series: MDMA, MGMA, and MFMA, with power ranging from 0.75 to 4.5kW, with a total of 23 specifications; the MHMA series large inertia motors have a power range from 0.5 to 5kW, with 7 specifications. In recent years, Samsung Corporation of South Korea has developed fully digital permanent magnet AC servo motors and drive systems. Among them, the FAGA AC servo motor series includes CSM, CSMG, CSMZ, CSMD, CSMF, CSMS, CSMH, CSMN, and CSMX models with power ranging from 15W to 5kW. The power rate is now often used as a comprehensive indicator as the quality factor of the servo motor to measure and compare the dynamic response performance of various AC and DC servo motors and stepper motors. The power rate represents the ratio of the motor's continuous (rated) torque to the rotor's moment of inertia. Calculation and analysis based on the power change rate show that the technical indicators of permanent magnet AC servo motors are best in the Goldline series of American ID, followed by the IFT5 series of German Siemens. Servo Motor Principle1. AC servo motorThe structure of the AC servo motor stator is basically similar to that of the capacitor split-phase single-phase asynchronous motor. Its stator is equipped with two windings with a position difference of 90°, one is the excitation winding Rf, which is always connected to the AC voltage Uf; the other is the control winding L, which is connected to the control signal voltage Uc. Therefore, the AC servo motor is also called two servo motors. The rotor of AC servo motor is usually made into squirrel cage type, but in order to make the servo motor have a wide speed regulation range, linear mechanical characteristics, no "self-rotation" phenomenon and fast response performance, it should have the two characteristics of large rotor resistance and small moment of inertia compared with ordinary motors. There are two forms of rotor structures that are widely used at present: one is a squirrel cage rotor with high resistivity bars made of high resistivity conductive materials. In order to reduce the moment of inertia of the rotor, the rotor is made slender; the other is a hollow cup rotor made of aluminum alloy, with a cup wall of only 0.2-0.3mm. The hollow cup rotor has a small moment of inertia, quick response, and stable operation, so it is widely used. When there is no control voltage in the AC servo motor, there is only a pulsating magnetic field generated by the excitation winding in the stator, and the rotor is stationary. When there is a control voltage, a rotating magnetic field is generated in the stator, and the rotor rotates in the direction of the rotating magnetic field. Under the condition of constant load, the speed of the motor changes with the size of the control voltage. When the phase of the control voltage is opposite, the servo motor will reverse. Although the working principle of AC servo motor is similar to that of capacitor-operated single-phase asynchronous motor, the rotor resistance of the former is much larger than that of the latter. Therefore, compared with capacitor-operated asynchronous motor, servo motor has three significant characteristics: 1. Large starting torque: Due to the large rotor resistance, the torque characteristics (mechanical characteristics) are closer to linearity, and have a larger starting torque. Therefore, when the stator has a control voltage, the rotor rotates immediately, that is, it has the characteristics of fast starting and high sensitivity. 2. Wide operating range: stable operation and low noise. ［/p］［p=30, 2, left］3. No self-rotation phenomenon: The servo motor in operation will stop running immediately if the control voltage is lost.
What is "precision transmission micro motor"?
"Precision transmission micro motors" can quickly and correctly execute frequently changing instructions in the system, drive the servo mechanism to complete the work expected by the instructions, and can mostly meet the following requirements: 1. It can start, stop, brake, reverse and run at low speed frequently, and has high mechanical strength, high heat resistance and high insulation grade. 2. Good rapid response capability, large torque, small moment of inertia and small time constant. 3. Equipped with a driver and controller (such as servo motor, stepper motor), with good control performance. 4. High reliability and high precision. Category, structure and performance of "precision transmission micro motor" 1. AC servo motor(1) Cage-type two-phase AC servo motor (slender cage rotor, nearly linear mechanical characteristics, small size and excitation current, low-power servo, and not smooth enough at low speed) (2) Non-magnetic cup-shaped rotor two-phase AC servo motor (hollow cup rotor, mechanical characteristics are approximately linear, volume and excitation current are large, small power servo, low-speed operation is smooth) (3) Ferromagnetic cup-shaped rotor two-phase AC servo motor (ferromagnetic cup-shaped rotor, nearly linear mechanical characteristics, large rotor moment of inertia, small cogging effect, and stable operation) (4) Synchronous permanent magnet AC servo motor (consisting of a permanent magnet synchronous motor, a tachometer and a position detection element coaxially integrated unit, with a 3-phase or 2-phase stator and a magnetic material rotor, and must be equipped with a driver; wide speed regulation range, mechanical characteristics consisting of a constant torque zone and a constant power zone, continuous stall capability, good rapid response performance, high output power, and small torque fluctuation; available in square wave drive and sine wave drive modes, good control performance, and is a mechatronics product) (5) Asynchronous three-phase AC servo motor (the rotor is similar to the cage-type asynchronous motor, must be equipped with a driver, uses vector control, expands the constant power speed regulation range, and is mostly used in machine tool spindle speed regulation systems) 2. DC servo motor(1) Printed winding DC servo motor (disc-shaped rotor, disc-shaped stator, axially bonded cylindrical magnetic steel, small rotor moment of inertia, no cogging effect, no saturation effect, and large output torque) (2) Wire-wound disc-type DC servo motor (disc-shaped rotor, stator axially bonded cylindrical magnetic steel, small rotor moment of inertia, better control performance than other DC servo motors, high efficiency, and large output torque) (3) Cup-type armature permanent magnet DC motor (hollow cup rotor, small rotor inertia, suitable for incremental motion servo system) (4) Brushless DC servo motor (stator is multi-phase winding, rotor is permanent magnet, with rotor position sensor, no spark interference, long life, low noise) 3. Torque motor(1) DC torque motor (flat structure, large number of poles, slots, commutator segments, and series conductors; large output torque, continuous operation at low speed or stall, good mechanical and regulation characteristics, and small electromechanical time constant) (2) Brushless DC torque motor (similar in structure to brushless DC servo motor, but flat, with more poles, slots and series conductors; large output torque, good mechanical and regulation characteristics, long life, no sparks and low noise) (3) Cage-type AC torque motor (cage-type rotor, flat structure, large number of poles and slots, large starting torque, small electromechanical time constant, long-term stall operation, relatively soft mechanical characteristics) (4) Solid rotor AC torque motor (solid rotor made of ferromagnetic material, flat structure, large number of poles and slots, can be locked for a long time, runs smoothly, and has relatively soft mechanical characteristics) 4. Stepper motor(1) Reaction stepper motor (the stator and rotor are both made of stacked silicon steel sheets, there is no winding on the rotor core, and there is a control winding on the stator; the step angle is small, the starting and running frequency is high, the step angle accuracy is low, and there is no self-locking torque) (2) Permanent magnet stepper motor (permanent magnet rotor, radial magnetization polarity; large step angle, low starting and running frequency, holding torque, power consumption is lower than the reactive type, but positive and negative pulse currents are required) (3) Hybrid stepper motor (permanent magnet rotor, axial magnetization polarity; high step angle accuracy, holding torque, small input current, and the advantages of both reactive and permanent magnet types) 5. Switched reluctance motor (both the stator and rotor are made of stacked silicon steel sheets, both are salient pole type, similar in structure to large-step reactive stepper motors with similar pole numbers, with rotor position sensor, torque direction is independent of current direction, speed regulation range is small, noise is high, mechanical characteristics consist of three parts: constant torque area, constant power area, and series excitation characteristic area) 6. Linear motor (simple structure, guide rails can be used as secondary conductors, suitable for linear reciprocating motion; good high-speed servo performance, high power factor and efficiency, and excellent constant speed operation performance)
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