Selecting the Optimum Motion Technology for your Application Series: Accuracy

Another factor to review is the accuracy required from the motion system in the application.  Is the motion continuous or incremental?  What is the resolution needed from the motor during incremental operation?  Does the motor need to have different resolutions for different points in the operation?

The motor technologies offer different methods of achieving accuracy.  DC and Brushless DC motors require an encoder to track and control the position of the rotor.  Standard encoders offer a range of resolutions within the same package size to meet the varying requirements of applications.  Increased resolution can be gained by the addition of a gearbox on the front of the motor.  The resolution is multiplied by the gear ratio, so combining the encoder and gearbox multipliers can achieve precise positioning.

Stepper motors provide positional accuracy based on their mechanical construction.  The number of poles on the rotor will dictate the number of steps per revolution, providing a step angle for each pulse given to the motor.  Drivers typically can increase this resolution by ½ or micro-stepping, creating intermediate steps between the mechanical ones.  The addition of a gearbox is an option here too, gaining the resolution of the gear ratio.  When sized with a proper safety factor, stepper motors can be run open loop (no encoder) to achieve the desired accuracy.

The Portescap application engineers can review the different technology options and additions to achieve your desired accuracy.  Contact us to discuss the available options for your application.