Robohub.org
 

Rapid prototyping of the strider robot – smoother, stronger, faster

by
29 August 2018



share this:

This summer we used our Strider optimizer coupled with rapid prototyping in LEGO to refine its 10-bar linkage.

In a tiny fraction of the time it took us to refine TrotBot’s linkage in our garage, we explored numerous variations of Strider’s linkage and their trade-offs, and were able to significantly improve its performance in these categories:

Gait Efficiency. To be energy efficient, walking gaits should be smooth and not cause the robot to rise and fall – think how much more tiring it is to do lunges than it is to simply walk. The feet should also move at constant speed – try walking while changing how quickly your feet sweep across the ground and your leg muscles will quickly complain! Strider Ver 3 was optimized for both of these features, and it’s the only mechanism that we’ve tested which can walk with a 1:1 gear ratio without the LEGO motors stalling:

Rugged Terrain. Like with TrotBot, we wanted Strider to be able to walk on rugged terrain, otherwise why not just use wheels? But, mechanical walkers are blind and dumb, and they can’t lift their feet to avoid tripping on obstacles. So we designed Strider’s foot-path to mimic how you would walk blindfolded on a path crisscrossed by roots: lift your feet high and keep them high until stepping back down to the ground, like this:

Here’s a rugged terrain test an 8-leg build:

Strength. Walkers stress frames more than wheeled vehicles, so we increased the frame’s rigidity with more triangles. Also, the leverage of long legs can put a tremendous amount of force on the leg’s joints, especially when turning them tank-style. We strengthened Strider’s leg joints by sandwiching them between beams like in the image below, which also reduces how quickly friction wears down the lips of the frictionless pins.

Here’s a test of Strider’s strength with a 10 pound load:

We made these changes while keeping Strider simple – it’s still our easiest walker to build. We also (hopefully) made our building instructions more clear. We learned how bad we are at creating building instructions from Ben’s experience teaching his walking robots class last spring. In the past when users would email us about something confusing in the instructions, we’d simply add more pictures to clarify things. This backfired in Ben’s class, since more build pictures resulted in the students getting more confused, and caused them to skim thru the pictures more quickly, and to make more mistakes. As we learned, less is more!

We also separated the leg and frame instructions to make it easier to build different versions of Strider, and we designed the frame to make it easy to swap between the battery box/IR controller, or the EV3 brick. You can find the instructions here. Here’s an example build with the EV3 brick mounted underneath – but it would probably work with the brick mounted on top as well.

For the bold, we also posted a half dozen new variations of the Strider linkage for you to try building here, along with an online optimizer for the even bolder to create their own versions of the Strider linkage. We’ve also optimized Klann’s and Strandbeest’s linkages for LEGO, and you can find their online optimizers here. (jeez, I guess we’ve been busy)

Here’s a final teaser to encourage you (or your students) to take on the challenging task of replacing wheels with mechanical legs:




Wade Vagle is a robotics mentor.
Wade Vagle is a robotics mentor.





Related posts :



Unable to attend #ICRA2022 for accessibility issues? Or just curious to see robots?

There are many things that can make it difficult to attend an in person conference in the United States and so the ICRA Organizing Committee, the IEEE Robotics and Automation Society and OhmniLabs would like to help you attend ICRA virtually.
17 May 2022, by
ep.

350

podcast

Duckietown Competition Spotlight, with Dr Liam Paull

Dr. Liam Paull, cofounder of the Duckietown competition talks about the only robotics competition where Rubber Duckies are the passengers on an autonomous driving track.
17 May 2022, by

Designing societally beneficial Reinforcement Learning (RL) systems

In this post, we aim to illustrate the different modalities harms can take when augmented with the temporal axis of RL. To combat these novel societal risks, we also propose a new kind of documentation for dynamic Machine Learning systems which aims to assess and monitor these risks both before and after deployment.
15 May 2022, by

Innovative ‘smart socks’ could help millions living with dementia

‘Smart socks’ that track rising distress in the wearer could improve the wellbeing of millions of people with dementia, non-verbal autism and other conditions that affect communication.
13 May 2022, by

Swiss Robotics Day showcases innovations and collaborations between academia and industry

The 2021 Swiss Robotics Day marked the beginning of NCCR Robotics’s final year. The project, launched in 2010, is on track to meet all its scientific goals in the three areas of wearable, rescue and educational robotics, while continuing to focus on supporting spin-offs, advancing robotics education and improving equality of opportunities for all robotics researchers.
10 May 2022, by

Afreez Gan: Open Source Robot Dog, Kickstarter, and Home Robots | Sense Think Act Podcast #18

In this episode, Audrow Nash speaks to Afreez Gan, who is the founder and CEO of MangDang; MangDang is a Chinese startup that makes Minipupper, an open source robot dog that uses the Robot Operating S...





©2021 - ROBOTS Association


 












©2021 - ROBOTS Association