Motor Drives and Amplifiers


Electric servo motors require an amplifier to provide the current to the correct phases at the right time, which is called commutation.

The following items are important to make sure a drive is compatible with the RMC:

  1. ±10V Control Signal
    The drive must accept a ±10V signal from the RMC as a velocity command or torque command. Velocity will typically produce the best results, but will require tuning the drive.

  2. Encoder Feedback to Drive
    For high-performance control, the drive should support encoder feedback. The drive should be wired to both hall sensors and an encoder from the motor. Using only hall effect sensors will not result in as good control as using an encoder. Delta always recommends using an encoder.

  3. Position Feedback to RMC
    The RMC must also receive feedback from the system. This can be either:

    • From the encoder.
      If the encoder outputs quadrature A and B signals with RS-422, then the signal can typically be connected to both the drive and to the RMC. However, many drives output only single-ended signals which cannot be connected to the RMC.

    • Encoder emulation from the drive.
      Many drives can output (emulate) an encoder signal that can be used by the RMC as position feedback. Most of these drives output quadrature. Make sure that the signal is RS-422. If the signal is single-ended, a converter can be used to convert to RS-422.
      Some drives output an SSI signal that can be used by the RMC.

    • Another sensor.
      The system may have a different sensor, such as a linear position sensor. This has an advantage in that is measures the position where it is most important. Measuring at the motor encoder may not take into account backlash.

There are two main types of amplifiers: Analog Amplifiers and Digital Drives. Delta’s RMC motion controllers can work with both Analog Amplifiers and Digital Drives.
Analog Amplifiers are less expensive but lack many features available on Digital Drives. Analog Drives are generally set up by turning potentiometers and setting switches. Digital Drives are set up using software on a PC or by downloading data over a network. Digital Drives have control modes not available on Analog Amplifiers. Many motor manufacturers will sell motors and digital drives as matched sets which makes design easier.

Analog Amplifiers that have been used with the RMC:
Copley Controls
Advanced Motion Controls
These companies also sell Digital Drives. Many others do as well.

Drives that have been used with the RMC:
Allen Bradley
Pacific Scientific

Drives with SSI emulation:
MOOG: MSD Servo Drive. This drive supports SSI emulation that can be used by the RMC as feedback. This requires the SSI module option.

For more details, or to suggest a product to be added to this list, send an email to