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Smart Servo Module

drawing

The Bpod Smart Servo Module controls up to 9 Dynamixel X-series servo motors.

Smart servo motors offer capabilites beyond popular "hobby" servos. They are controlled via serial interface, and follow parametric movement trajectories. Movement feedback is provided by a 4096-position magnetic encoder built into each motor, for precise position control.

Control modes are available for continuous rotation, current-limited movement and stepping relative to the current position. Additional capabilities include position readback, motor auto-detection and torque control.

The module can store a library of motor programs each consisting of timed movements addressing any connected motor.

A screw terminal interface exposes DIO channels for triggering from pushbuttons and external instruments.

Key specs are:

  • Arduino-compatible 600MHz ARM Cortex M7 processor (Teensy 4.0)
  • Compatibility: Dynamixel X-series servos with TTL interface (part name ending in T)
  • Motor Serial Channels: 3
  • Motors Supported: 9 (3 daisy-chained per channel)
  • Motor voltage: 5V-12V via external wall adapter. All motors connected to a single module must use the same voltage.
  • USB Motor Power: Enabled via internal jumper. Use at your own risk with X-series 5V motors only.
  • Control modes:
    • Position: set a goal position in range (0, 360) deg
    • Extended position: set a goal position in range (-91800, 91800) deg
    • Current-limited position: set a goal position and a maximum motor current (mA)
    • Velocity: set continuous rotation at a target velocity (rev/s)
    • Step: Move degrees relative to the current position
  • Motor programs:
    • Total programs: 100
    • Max steps per program: 255
    • Triggering: State Machine, TTL/pushbutton or USB (MATLAB/Python)
  • Movement parameters:
    • Goal position (degrees)
    • Maximum velocity (rev/s)
    • Maximum acceleration (rev/s^2)
    • Maximum motor current (Control mode 3 only)
  • Readback via USB:
    • Position
    • Motor temperature
  • Triggering:
    • Parametric single-movement command via USB or State Machine
    • Motor program (previously loaded) triggered via USB, State Machine or DIO

  • DIO Interface: Three DIO channels are exposed via a screw terminal. Configured as inputs they can:

    • Start motor programs
    • Stop motor programs
    • Stop all motors, setting torque to 0

    Each channel is pulled weakly high, so a pushbutton can be installed between the channel and GND.

The Smart Servo module is controlled from MATLAB with the SmartServoModule class.

Its interfaces to the Bpod State Machine and USB are documented here.

Bill of Materials