Servo motor (伺服电机)Refers to the servo control of mechanical components in the system operation of the engine, is a kind of subsidy motor indirect variable speed device. the role of the servo motor is the input voltage signal,The control voltage)Into a shaft angular displacement or angular velocity output, in automatic control system as actuators, so also known as force motor, servo motor, its biggest characteristic is: is rotor rotating immediately when the control voltage, no control voltage rotor immediately halt. Axis of steering and speed is determined by the direction and size of the control voltage. Divided into two major categories of ac and dc servo motor. The basic structure of ac servo motor is mainly composed of stator and rotor. usually use silicon steel sheet veiw of the stator core. Groove on the surface of the stator core is embedded with two phase winding, one phase winding is exciting winding, another phase winding is to control the winding, two phase winding each other in spatial location 90 & deg; Electric point of view. The working principle of when there is no control voltage ac servo motor, only produced by the pulse excitation winding in the air gap magnetic field, no startup torque on the rotor and stationary. When there is a control voltage current and exciting winding and control winding current, different phase is to produce a rotating magnetic field in air gap and generate electromagnetic torque, the rotor rotate along the direction of the rotating magnetic field. But for servo motor requires not only is can start under the effect of the control voltage, and voltage disappeared after the motor should be able to immediately halt. If the servo motor control voltage disappears like general single-phase asynchronous motor continue to roll, then appear out of control phenomenon, we call this because of out of control and self rotation is called rotation. to eliminate the phenomenon of the rotation of the ac servo motor, and must strengthen the rotor resistance r2, this is because when the control voltage disappears, the single phase operation of the servo motor, if the rotor resistance is very big, the critical slip sm> 1, when the positive and negative sequence generated by the role of a rotating magnetic field and rotor two torque characteristic curve and the synthetic characteristic curve of torque as shown. Synthesized from can be seen in the figure, the direction of the torque and motor rotate in opposite directions, is a braking torque, which ensures that when the control voltage disappeared after the rotor turns, still will be quickly brake and stop motor. After rotor resistance increase, not only can eliminate the rotation, also enlarge the speed range, improved regulation characteristics, improve the reaction speed, etc. control method can adopt the following three methods to control the servo motor speed and the direction of rotation. (1)Amplitude control maintain phase difference between the control voltage and the excitation voltage unchanged, only change the control voltage amplitude. (2)Phase control to maintain the control voltage amplitude unchanged, only change the phase difference between the control voltage and the excitation voltage. (3)Picture -Phase control at the same time, change the control voltage amplitude and phase. Basic structure of the the traditional dc servo electric motor essence is common dc motor capacity is small, he wound type and permanent magnet type two kinds, the structure and common dc motor in the same structure. cup armature dc servo motor rotor made of non-magnetic materials cup hollow cylinder, rotor is lighter and make the moment of inertia of small, rapid response. In rotor made of soft magnetic materials between the inside and outside of the stator rotating, the air gap is bigger. brushless dc servo motor using electronic commutation device instead of the traditional brush and commutator, make it more reliable. The stator core structure and common dc motor basic same, it is embedded with multiphase winding, rotor permanent magnet materials. Basic working principle of the basic working principle of the traditional dc servo motor and common dc motor are exactly the same, relying on the effect of armature current and air gap flux produce electromagnetic torque, to rotate the servo motor. Usually adopt the armature control mode, that is, under the condition of the excitation voltage unchanged, by changing the armature voltage to adjust speed. The armature voltage is smaller, the speed is lower; The armature voltage is zero, the motor stalling. Due to the armature voltage is zero armature current is zero, also do not produce electromagnetic torque motor, there will be no & other; Rotation & throughout; 。 三、交直流伺服电机的区别 直流伺服电机的缺点： 电刷和换向器易磨损，换向时产生火花，限制转速 结构复杂，制造困难，成本高 交流伺服电机的优点： 结构简单，成本低廉，转子惯量较直流电机小 交流电动机的容量大于直流电机 伺服系统的性能要求 一、基本要求 1、位移精度高 位移精度：指指令脉冲要求机床工作台的位移量和该指令脉 冲经伺服系统转化为工作台的实际位移量之间的 符合程度 2、稳定性好 稳定性：指伺服系统在给定输入或外界干扰作用下，能在短暂 的调节过程后，达到新的或者恢复到原来的平衡状态 3、定位精度高 定位精度：是指输出量能复现输入量的精确程度 4、快速响应性好 5、调速范围宽 调速范围：是指机械装置要求电动机能提供的最高转速 和最低转速的比值 6、系统可靠性好 7、低速大转矩 二、伺服系统的分类 1、按伺服系统调节理论分类 开环伺服系统
