NOMAD BLDC QDD Actuator

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

Implemented Robotics

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Description
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Description

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.

Details

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

Project Logs

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Custom Rotors and Stators are Here!
Implemented Robotics • 02/20/2021 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: