In the open CNC system, the driving element of the movement under the control of the controller at the core, open core controller (such as the PMAC) to control all types of drive components and drive, glue stick enabling flexible configuration of drive components .
In the NC system, the drive components are CNC important part of the system, its performance will directly affect the system performance.glue gun Servo drive components used are the following types: stepper motors and drives, DC servo motors and drives, AC servo motors and drives, linear motors and drives, ceramic motor and its drive, torque motors. The most commonly used in CNC drive components are the first three, the talk focuses on three types of servo drive technology.
A stepper motor and drive.
Stepper motor and its driving device used in some simple open-loop numerical control system, cheap, easy to achieve speed, composition, and wiring is relatively simple, more accurate positioning.
Stepper motor is the electric pulse signal into the corresponding angular displacement or linear displacement of electromechanical actuators. In accordance with the principle of different stepper motor is divided into three categories: reactive, permanent magnet and hybrid. Step Motor structure is simple, there are poles on the stator, each pair of magnetic pole has a winding around the rotor and the stator core are very small teeth on the boots, given a small air gap between rotor. Permanent magnet stepper motor rotor or stator of a party with a permanent magnet, soft magnetic materials produced by the other party, no small teeth on the rotor. Hybrid stepper motor is a stepper motor in the future development trend, which combines reaction and the characteristics of permanent magnet stepper motor. From its magnetic circuit containing a permanent magnet as the magnet of view, but from the stator or the rotor magnet to see but also as reactive in its rotor Similarly on the small teeth. Hybrid stepping motor has a step angle of reaction the advantages of small, but also has a small permanent magnet of the control power, power off after a certain detent torque characteristics. Typical products for Japan and Germany Boge La servo's hybrid stepper motors. Characteristics and stable performance, hybrid stepping motor is ideal. Stepper motors are precision characteristics of technical indicators, torque, response frequency, frequency characteristics and the inertia moment of the frequency characteristics.
Stepper motor can not work alone, it must and its special equipment - stepper motor drive together. Stepper motor driver's basic functions are: the order and frequency according to certain stepper motors on and off the field winding, in accordance with the requirements of the motor to start, stop: the provision of adequate electric power: stepper motor to improve the speed and smooth running sex. The composition of step motor driver shown in Figure 1.
Pulse distributor received instruction and direction of the signal pulse after the command signal in accordance with the motor distribution of the conductive phase sequence pulse signal, the pulse signal after the distribution of instructions through the power amplifier drive a stepper motor work. In practical applications, but also such as circuit protection, broken drivers and other issues. Subdivided driving principle is to switch each input pulse when not all pass into the winding current or the removal, but the only change in the nominal part of the corresponding winding. This is not a winding in the current square wave, but a step wave, current, divided into several steps, the same number of the rotor to turn one step angle. The main purpose of segmentation is to drive stepper motors run more smoothly and improve the uniform nature, weaken or eliminate the oscillations, but also the complicated structure of the drive. Currently on the market a lot of stepper motor driver, such as Japan MYCOM produced UPS200, it can be used to drive two-phase hybrid stepping motor. Up to 2A per phase current, and adjustable pulse plus direction signals can be received or dual pulse signal (CW and CCW), to bring the whole - half-step drive, there are over-current protection and automatic half-current (in the absence of command pulse 1s phase current will be halved) function.
2 DC servo motor and drive.
DC servo motor and drive long history and wide use.
It features a large overload capacity, good dynamic performance, wide speed range, speed ratio can be 1:1000 or more, a good low stiffness, high-precision positioning can be carried out at low speed can output a larger torque. However, as brush DC servo motors with brushes and commutator, the motor during operation will generate commutation spark, so the spacecraft, satellites, and explosive special occasions such as DC servo system is not suitable for use.
DC servo system by the encoder position and velocity feedback to achieve closed-loop control. DC servo motor in accordance with the armature structure divided into: permanent magnet DC servo motors, slotless armature DC servo motors, DC servo motor armature hollow glass, printed circuit DC servo motor. Permanent magnet DC servo motor which is small in size, torque, torque and current proportional to the power of the volume ratio and good stability is very important in electrical servo system of a motor. Permanent magnet DC servo motor structure and general structure similar to the DC motor, but the armature core large aspect ratio, small air gap. Slotless armature DC servo motor armature core is a smooth cylinder, the armature winding is fixed to the core by the resin surface. Moment of inertia is characterized by small, generally for applications that require fast action, power larger occasions. Coreless DC servo motor armature windings with epoxy pouring into a cup, a core composition inside and outside the armature magnetic circuit, which is characterized by a small moment of inertia, low speed smoothness, long life and high efficiency. Printed Circuit DC servo motor armature insulation board is printed in the circular form the armature winding bare, with fast response characteristics, and can withstand the frequent reversible operation.
Most of the current use of DC servo motor PWM (pulse width modulation) drive drive. By changing the PWM duty cycle of periodic pulse signal to change the increase in the average voltage on the motor to achieve speed. This method has a constant torque speed governing characteristics, mechanical characteristics of a good, wide speed range.
U.S. Copley produced a full range of DC servo motors and drives, including a brush DC servo motor and drive, brushless DC motors and drives, brushless AC motor (permanent magnet synchronous AC motor) and driver and DSP chip-based digital servo drives. In its brush DC servo drive, you can choose to use servo drive torque control or speed, torque control all of the servo drives.
3 AC servo motor and drive.
With high-speed CPU and other computing chip price cuts, AC servo motor and drive into the increasingly wide range of applications. AC servo motor for closed loop control system, usually a cage asynchronous servo motors and permanent magnet synchronous servo motor two. Now is the most widely used permanent magnet synchronous servo motor, it mainly consists of two parts, the rotor and the stator, the rotor is equipped with a special shape of the permanent magnet, there is no field winding, stator core is equipped with three-phase field winding. The asynchronous servo motor control is very complex, requiring use of vector control, low-speed characteristics of good, so use is not widespread. The following describes the main AC synchronous servo motor and its driving principle.
Permanent magnet AC servo drive and control by way of drive current waveform is divided into rectangular wave current drive and the sine wave current drive (SPWM) of two types. Rectangular wave-driven permanent magnet AC servo motor to brushless DC servo motor, sine wave drive brushless permanent magnet AC servo motor for the AC servo motor. Synchronous servo drive principle in Figure 2.
The control block diagram is only drawn some of the speed loop and current loop. Photoelectric encoder pulse signal generated by the speed of processing into a digital signal decoder directly to the CPU, the digital regulator with the speed reference signal comparison operation (PID) resulting from three-phase AC current amplitude signal Im. In order to improve the quality of speed regulation, and now most of the drive using the following two key technologies: First, the decoder speed measurement methods used in M23, that the motor at high speed by recording the number of pulses per unit time to achieve speed measurement, and the motor at low speed, by recording the time between the two pulses to achieve long-velocity measurements.
No matter at high speed and low speed can be very accurate determination of motor speed. Second, the digital regulator sliding algorithm uses advanced algorithms, this algorithm based on the motor running at high speed and low speed on the different characteristics, were given different PID regulator parameters to the parameters of each stage can be optimized.
The current amplitude of the signal through the multiplier Im and the motor rotor position signal q by vector multiplication to synthesize three-phase alternating current. Q position signal generated by the optical encoder pulse signal processing made by the location of the decoder.
iu = Imsinq.
iv = Imsin (q 120 °).
iw = Imsin (q 240 °).
When the three-phase current obtained after the current regulator and feedback into the back of the current signal comparison operation, and then modulated by the PWM servo motor-driven work.
In addition to these basic structures, the circuit also joined the fault handling and protection of areas, such as overvoltage, undervoltage, overcurrent, phase and the motor overheating and other hardware detection and protection circuitry. Once the failure to notify the CPU and lock the data output.
Panasonic in Japan synchronous AC servo motor and its drive for performance and stability, functional and easy to operate in the industry won a good reputation. The servo system can easily torque, speed, location, or complex control, drive through its unique control panel so that you can not have any other additional tools to modify the various parameters. Internal control using sliding mode algorithm, and provides various protection and monitoring functions.
4 drive units selection.
Briefly above, the basic principle of the servo system and related products. Servo drive system in the selection of the user when the main factors to consider the following points: ① According to the location accuracy requirements and the choice of which type of motor occasions: ② consider matching servo system parameters: load torque and motor torque, load inertia and motor inertia (general motor inertia to be elected in the load inertia of 1 to 3 times the range), according to these choices the right size motor: ③ under control, driving capacity, and the other asked to select the appropriate servo drives: ④ other special requirements. Of course, the right to choose the right servo drive system, the user may, in accordance to choose their actual application requirements.