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NOMAD BLDC QDD Actuator

Compact High Bandwidth, High Performance and Compliant Actuator for use in Legged Robotics.

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These BLDC actuators were developed to support the build of the NOMAD 12-DOF Quadruped project. At the time of the start of development there were no readily available off the shelf solutions to solve this problem. The design is very much based on the actuators from the MIT Cheetah mini robot but with an increased maximum current and torque ratings. They feature a 6:1 planetary gear reduction to keep compliance and torque transparency high. This is the so called quasi-direct drive configuration where there is some additional gear reduction for increased torque, but it is kept to a minimum to reduce reflected inertia, friction as well as to allow output torque sensing by the onboard motor controller. All parts with the exception of the bearings, gearing, rotor and stator where machined by me in my workshop.

Currently being used in the NOMAD Quadrupedal Robot Project!

Actuator Features and Specifications:

  • Custom BLDC 8118 sized 80Kv rated
  • Integrated 6:1 single stage planetary reduction for Quasi-Direct Drive(QDD)
  • Continuous/Peak Torque: 25N⋅m / 50N⋅m(short pulse duration)
  • 40V DC Bus Voltage
  • Continuous/Peak Current: 30A/80A (still needs testing)
  • Integrated AMS5147 Magnetic On-Axis Absolute Encoder
  • STM32G474 Microcontroller
  • DRV8323 Gate Driver
  • 40khz Control Loop Frequency
  • Ceramic Bus Link Capacitors optimized for use with Higher Control Frequency
  • Field Oriented Control(FOC) operating mode for high efficiency
  • FOC Current Mode
  • FOC Torque Mode
  • FOC Voltage Mode
  • Position Control Mode
  • Speed Control Mode
  • CAN-FD 5mbps Command Interface
  • UART Command Interface
  • On board FET Temperature NTC Thermistor
  • Support for External Temperature NTC Thermistor

  • Custom Rotors and Stators are Here!

    Implemented Robotics02/20/2021 at 22:16 0 comments

    Received the custom rotor and stator order from MAD Components.  These are 8118 sized stators would for 80KV rating.  Also a custom machined rotor for the direct integration of the encoder magnet on the back as well as the sun gear for the 6:1 planet gear reducer.  This lot will be used for the actuators of the NOMAD Quadrupedal Robot.  Next steps is to begin machining the aluminum housings for the actuators.  More to come!

    Well packed and undamaged.

    The offered to even add a logo for me free of charge.  Looks good!

    Closeups of one of the rotors:

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