When open-loop stepper performance isn't suitable for an application, an engineer will typically use a closed-loop three-phase brushless motor. This solution can become costly especially if high torque performance is also required. However, now it is possible to use Galil's 2 Phase Brushless (2PB) option with stepper motors to gain the advantages of both stepper motors and closed-loop three-phase brushless motors in one small, easy to use package. Three phase BLM and 2PB are mutually exclusive features. If you require a mix of the motors, please contact an applications engineer at Galil.
Like a three-phase brushless motor, Galil sinusoidally commutates a two phase stepper motor which ensures smooth motion with no discontinuities. A small difference is that each phase in a three-phase brushless motor is offset by 120 electrical degrees while each phase in a two-phase stepper is offset by 90 degrees. The 2PB closed-loop solution also allows the controller to use PID parameters, pole/ notch filters, and feed forward control parameters. These capabilities enable the controller to account for friction, resonances, and other system perturbations.
There are many benefits to closed-loop stepper control such as greater position accuracy and reduced motor power consumption. Other advantages include high torque performance comparable to implementing a three-phase brushless motor with a gear box. The greatest advantage of using steppers in closed-loop control is the low cost of the stepper motors themselves and the cost benefit of not needing a gear box when high torque is required. All of these advantages provide an ideal option for an application that requires a high torque, low cost, precision solution.
For additional information on closed-loop stepper performance, please refer to the Closed-Loop Stepper Motor Performance Gains article.
The 2PB option is available now for Galil’s integrated sinusoidal amplifiers the AMP-43540, AMP-43520, and the DMC-30017. For ordering options, please refer to Galil's part number generator.