Blackbird Bipedal Robot

A lightweight and efficient human-scale bipedal robot.

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The aim of this project is to build an underactuated biped based on the spring-mass model -- similar to Agility Robotics' Cassie and its predecessor ATRIAS.

This robot differs from other spring-mass-based bipeds in the type of actuators used -- specifically, quasi-direct-drive rather than series-elastic. This allows the "springs"  to be implemented in software rather than hardware, simplifying the design and reducing cost. 

This is the actuator I designed for use in this project: OpenTorque Actuator

The project will be split up into 2 stages. First, I'll build a simplified, 2d planar biped capable of walking on a treadmill. Once that works, I'll add the other 6 actuators (yaw, roll, and ankle pitch for each leg) for a complete, fully-functional robot. 

  • Leg testing

    Gabrael Levine09/24/2018 at 06:43 0 comments

    I'm running some sinusoidal trajectories on the leg to simulate different modes of locomotion such as walking and jumping. The actual controller will be far more complicated of course, but this gives me the opportunity to check the range of motion. 

    I also put the leg right-side-up on the ground to see how much current it draws when standing. The results were promising -- only 15A per actuator. Or in other words, only 37 watts for the entire leg. It seems highly likely that I'll be able to hit the goal of 2 hours of operation on a 500Wh battery. (The real robot will need to support more weight, like the battery and yaw/roll actuators, but this will be mitigated by the new actuator I'm designing that features a 50% higher gear ratio and better cooling.)

  • Leg Operational

    Gabrael Levine09/21/2018 at 01:56 0 comments

    Quick update: I finished wiring up the encoders and got the leg working. More to come soon.

  • First Leg Complete

    Gabrael Levine09/07/2018 at 00:26 0 comments

    I finished assembling the first leg for the prototype Blackbird robot. It's made from 2 OpenTorque actuators, some carbon fiber tubes, and a few printed parts. (The parts were printed out of PLA but will be redone in NylonX for the final version.) 

    Since this is a simplified prototype, there's no ankle joint. Instead it has a point-contact foot. This makes it a better approximation of the spring-loaded inverted pendulum (SLIP) model, which makes developing the controls easier, but it'll need an ankle joint to be able to stand still. Until the ankle joint is added, I can use dynamic standing (see the video below).

    Next up: building a test rig from V-slot extrusions and seeing how high the leg can jump. 

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merck.ding wrote 09/11/2018 at 11:37 point


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Paul Crouch wrote 09/08/2018 at 20:59 point

Loving this, reminiscent of Cassie (minus the series-elastic components). Watching with interest.

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