The GRT-Minus is a miniature, low-voltage, single-axis servo drive. The GRT-Minus models are fully digital controllers, capable of driving brushed and brushless DC motors.

The GRT-Minus is powered by a 18-70 VDC supply, and is capable of sourcing up to 12A RMS continuous current, and (according to model) up to 30 peak current.


All the GRT-Minus models have the following abilities:

  • Fully digital current, velocity or position closed loop control.
  • Support of the DS301 CAN-Open communication standard. This includes, among others: SDO, programmable PDO, OS interpreter, Heartbeat, Emergency and NMT


The PWM switching frequency is set up to a minimum of 10 kHz. Combined with advanced space-vector modulation, this enables operation with minimal current ripple and acoustic noise.

The GRT-Minus is a partial DFT-Servo implementation meant for driving current into a BLDC motor with analog commands and Hall sensor position feedback.


For that purpose, the GRT-Minus is equipped with:

  • Analog command input
  • Discrete enable signal (configurable)
  • Discrete I/O indications
  • Analog output for observing current or speed


  • Motor

  • Up to 900W

    Brush DC

    Brushless DC

  • Control modes

  • Torque (current) control

  • Feedback

  • Incremental encoder

  • Commutation

  • Hall sensors only, or Hall sensors aided by incremental encoder

  • RMS continuous current

  • 12 A

  • RMS peak current

  • 20 A

  • Logic voltage (separate supply, if applicable)

  • 16 – 70VDc.

  • Bus voltage

  • 16 – 70VDc.

  • Maximum output voltage

  • 99% of operating voltage

  • PWM frequency

  • 10 …20kHz

  • Maximum incremental encoder frequency

  • 10 M count/sec

  • Sample rate - current loop

  • 10 …20kHz

  • Operating temperature

  • -45 to 71°C   (-49° to 160°F)

    Screening to -55o (-67°F) is available

  • Storage temperature

  • -55 to 85°C   (-67° to 185°F)

  • Humidity

  • 5 to 95%, non-condensing

  • Weight

  • 100g, not including mating connectors

  • Dimensions

  • (L x W x H)  55 x 46.5 x 29.7 mm
    (L x W x H)  2.16 x 1.83 x 1.17 inch