3.2 工作原理

直流伺服電機(jī)的工作原理與普通的直流電機(jī)工作原理基本相同。依靠電樞氣流與氣隙磁通的作用產(chǎn)生電磁轉(zhuǎn)矩，使伺服電機(jī)轉(zhuǎn)動(dòng)。通常采用電樞控制方式，在保持勵(lì)磁電壓不變的條件下，通過(guò)改變電壓來(lái)改變轉(zhuǎn)速。電壓越小轉(zhuǎn)速越低，電壓為零時(shí)，停止轉(zhuǎn)動(dòng)。因?yàn)殡妷簽榱銜r(shí)，電流也為零，所以電機(jī)不會(huì)產(chǎn)生電磁轉(zhuǎn)矩，既不會(huì)出現(xiàn)自轉(zhuǎn)現(xiàn)象。

直流伺服電機(jī)在數(shù)控系統(tǒng)中應(yīng)用很多，但是直流伺服電機(jī)也有一定的缺點(diǎn)：它的電刷和換向器易磨損；電機(jī)轉(zhuǎn)速的限制，應(yīng)用環(huán)境的限制；結(jié)構(gòu)復(fù)雜，制造困難，成本高。

二 伺服驅(qū)動(dòng)器

1. 概念

伺服驅(qū)動(dòng)器又稱為伺服放大器或放大器，是將從控制器輸入的脈沖信號(hào)或模擬量信號(hào)經(jīng)內(nèi)部計(jì)算放大后輸出給電機(jī)的裝置。

2. 結(jié)構(gòu)及原理

伺服驅(qū)動(dòng)器主要有伺服控制單元、功率驅(qū)動(dòng)單元、通訊接口單元組成。其中伺服控制單元包括位置控制器、速度控制器、轉(zhuǎn)矩和電流控制器等。

伺服驅(qū)動(dòng)器大體可以劃分為功能比較獨(dú)立的功率板和控制板兩個(gè)模塊。功率板是強(qiáng)電部分，其中包括兩個(gè)單元，一是功率驅(qū)動(dòng)單元IPM用于電機(jī)的驅(qū)動(dòng)，二是開關(guān)電源單元為整個(gè)系統(tǒng)提供數(shù)字和模擬電源?？刂瓢迨侨蹼姴糠?，是電機(jī)的控制核心也是伺服驅(qū)動(dòng)器技術(shù)核心控制算法的運(yùn)行載體?？刂瓢逋ㄟ^(guò)相應(yīng)的算法輸出PWM/PFM信號(hào)，作為驅(qū)動(dòng)電路的驅(qū)動(dòng)信號(hào)，來(lái)改變逆變器的輸出功率，以達(dá)到控制交流伺服電機(jī)的目的。

3.2 Working Principle

The working principle of DC servo motor is basically the same as that of ordinary DC motor. Electromagnetic torque is generated by the action of armature air flow and air gap flux to make the servo motor rotate. The armature control method is usually used to change the speed by changing the voltage while keeping the excitation voltage unchanged. The smaller the voltage, the lower the speed. When the voltage is zero, stop rotating. Because when the voltage is zero, the current is also zero, so the motor will not produce electromagnetic torque, neither will there be rotation phenomenon.

Dc servo motor is widely used in numerical control system, but DC servo motor also has some disadvantages: its brush and commutator are easy to wear; The maximum speed limit of the motor, the application environment limit; The structure is complicated, the manufacture is difficult and the cost is high.

Two-servo driver

1. Concept

The servo driver, also known as the servo amplifier or amplifier, is a device that outputs the pulse signal or analog signal input from the controller to the motor after internal calculation and amplification.

2. Structure and principle

The servo driver is composed of servo control unit, power drive unit and communication interface unit. The servo control unit includes position controller, speed controller, torque controller and current controller.

The servo driver can be divided into two modules, the power board and the control board, which are relatively independent in function. The power board is the strong current part, which includes two units, one is the power drive unit IPM used to drive the motor, and the other is the switching power supply unit to provide digital and analog power for the entire system. The control board is the weak current part, the control core of the motor and the operating carrier of the core control algorithm of servo drive technology. The control board outputs PWM/PFM signal through the corresponding algorithm, which is used as the drive signal of the drive circuit to change the output power of the inverter, so as to achieve the purpose of controlling the AC servo motor.