Computers And Technology

From traditional steppers to innovative servos

Vaibhav Rai

September 07, 2018 10:30 PM

A simple guide to stepper and servo: how to choose?

Servos and steppes are the very engines that control the motion of many different devices and machines: robots, remotely controlled planes, video players and automatically opening doors in the supermarket. Both of them are able to do an amazing job and perform without a miss, but there are some occasions when one is better than the other. Much of the quality is determined by the motor, so we will focus on evaluating these two options and compare their key features in the most transparent way.

The correct choice will have long-term benefits and will have a strong positive impact on the overall production and the lifespan of it. At the same time, if you make a mistake at the very beginning by choosing a less efficient kind - performance and maintenance issues are inevitable.

The table shows the key features of servos and steppers opposed to each other.

  Stepper motor Servo motor
Torque Drops with the increase of speed. Peaks when the shaft is motionless Always high
Power Low. Stepper has a low output-input ratio, meaning that it consumes a lot of power and most of it emits with heat High. Current consumption equals the applied load
Position Feedback No feedback. System is not able to determine if the motor is missing steps Encoder provides feedback. The positioning of the shaft can be corrected, if not - the system will detect the mistake that can be dealt with
Precise positioning Can shift slightly: not more than 5% of the step Regulated by the encoder
Safety High level of safety. The worst thing that can happen is the machine missing some of the steps Medium. In case of poor programming can burn the engine down. But, modern models are getting safer to work alongside with
Roter resonance Steppers are prone to resonance that results in malfunctioning and poor quality of work -
Noise Loud Quiet
Heating Produces a lot of heat Usually requires cooling Not critical
Overload Can miss steps and can’t speed up due to the overload Tolerates overload and can  increase the speed in seconds

As compared in the table, servos are a bit more complex and intricate, when steppers have a simpler technology and do not require much of an adjustment. Though, if a stepper is damaged, there are no sensors to detect it. Steppers have excellent torque, but only at a low speed. They don’t require position feedback and have almost no major maintenance requirements.

Servo motor, on the other hand, is perfect for high speed, torque control or dynamic loads support. In many situations, where high precision is a must, a higher cost of servos is a price to be paid.