Servo motor knowledge summary

2019-09-28 424

  The word servo comes from the Greek word for slave."Servo motor" can be understood as a motor that absolutely obeys the command of the control signal.When the control signal is sent, the rotor immediately rolls.When the control signal disappears, the rotor can stop running immediately.

  Servo motor is a micro-motor used as an executive element in automatic control device. Its function is to convert electrical signals into angular displacement or angular velocity of the rotating shaft.

  Servo motor is divided into ac servo and dc servo two categories

  The basic structure of ac servo motor is similar to ac induction motor.There are two excitation windings Wf and control windings WcoWf with a phase space displacement of 90° on the stator, connected with a constant ac voltage. The purpose of controlling motor operation is achieved by using the change of ac voltage or phase applied to Wc.Ac servo motor has the characteristics of smooth operation, good controllability, fast response, high agility and strict nonlinear index of mechanical characteristics and adjusting characteristics (less than 10% ~ 15% and less than 15% ~ 25%, respectively).

  The basic structure of dc servo motor is similar to that of dc motor.Motor speed n = E/K1j = (Ua - IaRa)/K1j, type of E for armature counter electromotive force, K is constant, j per pole flux, Ua, Ia for the armature voltage and the armature current, Ra as the armature resistance, change Ua or phi, can control the speed of the dc servo electric thoughts, but generally adopt the method of control the armature voltage, thought of the electricity in the permanent magnet dc servo, excitation winding is replaced by a permanent magnet, magnetic flux phi is constant.Dc servo motor has good linear regulation and fast time response.

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  Advantages and disadvantages of dc servo motor

  Advantages: accurate speed control, torque speed characteristics are very hard, simple control principle, easy to use, cheap price.

  Disadvantages: brush reversing, speed limitation, additional resistance, abrasive particles (dust free and explosive environment is not suitable)

  Advantages and disadvantages of ac servo motor

  Strengths: good speed control features, in the whole speed range can realize smooth control, almost no oscillation, more than 90% of the high efficiency, less fever, high speed control, high accuracy position control accuracy (depending on the encoder), rated operation area, can realize the constant torque, moment of inertia is low, low noise, no brush wear, free maintenance (for dust-free, explosive environment)

  Disadvantages: the control is more complicated, the driver parameters need to be adjusted on the spot to determine PID parameters, and more wiring is needed.

  Dc servo motor is divided into brush and brushless motor.

  Brush motor cost is low, simple structure, start torque is big, speed range is wide, control is easy, need to maintain, but maintain the benefit (for carbon brush), the generation of electromagnetic interference, the use of the environment has requirements, usually used for the cost sensitive common industry and civil occasions.

  Brushless motor small weight light, large output response fast, high speed small inertia, torque is not disorderly rolling smooth, complex control, intelligent, electronic phase exchange flexible, square wave or sine wave phase exchange, motor maintenance free, efficient energy saving, electromagnetic radiation small, low temperature rise long life, suitable for various environments.

  Ac servo motor is also brushless motor, divided into synchronous and asynchronous motor, the current motion control is generally used synchronous motor, its power range, power can be very large, large inertia, the highest speed is low, speed with the increase of power and uniform decline, suitable for low speed smooth operation occasions

  The inside of the servo motor rotor is a permanent magnets, three-phase electric drive control U/V/W form the electromagnetic field, under the action of the rolling rotor in this field, at the same time, motor with encoder feedback signal to the drive, the feedback value compared with the target, to adjust the Angle of the rotor rolling, the precision of servo motor is determined by the precision of the encoder (line number).

  What is a servo motor? How many types are there? What are the job characteristics?

  Answer: servo electric idea also known as the executive electric idea, in the automatic control system top use as the executive element, the received electrical signal into the electrical idea axis angular displacement or angular speed output.

  Servo motor knowledge summary