Closed loop stepper motor Vs Servo

Closed-loop stepper motors are stepper motors with high precision encoders and servo control algorithms to achieve torque, speed and position loops.

Is a closed loop stepper a servo?

Closed-loop stepper motor is a stepper motor, it has all the functional characteristics of a stepper motor. The biggest difference between stepper motors and servo motors is that stepper motors are open-loop control and servo motors are closed-loop control.

Closed-loop Stepper Motor and Servo Motor difference

  1. closed-loop stepper motor body is a stepper motor, at a standstill is absolutely stationary. Servo motor in the stop can not be absolutely stationary, in the case of small load disturbance or servo motor parameters are well tuned, servo motor always fluctuate between positive and negative 1 pulse, in actual use can be properly adjusted motor rigidity to enhance its locking torque and performance.
  2. closed-loop stepper motor combines the characteristics of the stepper motor and servo control method, so it will not overshoot (because the characteristics of the stepper motor is not overshoot).
    Overshoot is common when a servo motor is turned from high speed to low speed or stationary. When the controller sends a pulse to the servo motor, the servo motor often does not go one pulse, but three pulses, and then back 2 pulses. This is absolutely not allowed for those scenarios with strict environmental requirements.
  1. Closed-loop stepper motor commissioning and use is very simple, only need to adjust the position of the driver’s 3 potentiometers, not only equipment manufacturers can use, but also equipment users can use, the user’s requirements are extremely low. Servo motor parameters are more difficult to debug, and requires experienced engineers to debug.
  2. closed-loop stepper motor using a true sine wave, vector and filtering way to control the current, the lowest speed can be controlled at 0.2 rpm, and the motor runs very smoothly and steadily, which even servo motors can not do (general servo motors can do 1 rpm in theory, the actual application is unable to do 1 rpm, roughly above 5 rpm).
  3. Relatively speaking, the accuracy of servo motors is higher than that of closed-loop stepper motors.
  4. Cost, to achieve the same function in the case of servo motor price is greater than the same power closed-loop stepper motor, in the cost of stepper motor is an advantage.
CNC Controller Kit

CNC Controller Kit

  • 60HSE88 Closed-loop servo motor 3N.m  88mm Length
  • HSS60 Servo driver  6A  AC24~50V

Closed loop stepper system can be applied to all kinds small automatic equipment and instrument. Such as engraving machine, special industrial sewing machine, stripping machine, marking machine, cutting machine, laser phototypesetting, graph plotter, cnc machine, automatic assembly equipment and so on.

Currnet Price

Closed-loop stepper motor and servo motor product performance differences

  1. Speed

Stepper motors with closed-loop control can achieve high-speed operation, speed almost comparable to servo motors, but also retains the characteristics of the traditional stepper motor low speed. Servo motor at high speed can be its performance, in high speed to low speed or stationary, there will be overshoot phenomenon.

  1. Moment frequency characteristics

Closed-loop stepper motor speed faster the torque is smaller, servo motor in the rated speed torque constant.

  1. Overload capability

Closed-loop stepper motor has a small (such as 1.5 times) short-time overload output capability, which improves the dynamic response of the stepper motor. Servo motor is generally 3 times overload.

  1. Commissioning difficulty

Closed-loop stepper motor commissioning and use is very simple, only need to adjust the position of a few potentiometers of the driver. Servo motors have hundreds of parameters, debugging complex, often requiring experienced engineers debugging.

  1. Noise, heat, vibration

Closed-loop stepper motor and servo motor in the application environment is not particularly rigorous, noise, heat, vibration is almost not much difference, but the servo motor or slightly superior.

  1. Working mode

Closed-loop stepper motors work in position mode and speed mode (integrated stepper motors support a variety of remote point of return mode), servo motors support position mode, speed mode and torque mode.

  1. Precision

Closed-loop stepper motors increase the accuracy of closed-loop control has improved a lot, but relatively speaking, it is still lower than the accuracy of servo motors.

  1. Cost and price

Closed-loop stepper motor in the cost of stepper motor is an advantage, to achieve the same function in the case of servo motor price is greater than the same power of the closed-loop stepper motor, servo motor’s high response, high speed and the advantages of high precision determines the high price of the product, which is inevitable.

To sum up, servo motors are used for high precision and high speed in order to give full play to its due speed and accuracy advantages, but in the application environment is not very strict closed-loop stepper motor is not bad.

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