Some extracurricular projects

My 8 DOF spider robot: making it learn to walk

November 7^th, 2018

When I was studying machine learning, I wanted to use those techniques in a physical environment. Thus, I built a 8 DOF spider robot. I followed the Kamrani’s rapid prototyping methodology: start with a simple design, build it, add more features, make the needed corrections, and then iterate the process several times.

I developed this project entirely on my own initiative, outside the requirements of any course, driven by my own curiosity and passion for building physical robots.

Iterative design process of the spider robot — Iterative process of the spider design. I started with a simple walking robot, but it could not move itself without falling down. After that, I added two DOF at each leg, and increased the torax's size. Then, I increased the number of legs, and added one rotative distance sensor. In the next step, I simplified the leg design, but it was a bit unstable. Hence, for the last iteration, I used a 1 DOF four-bar linkage mechanism at the end of each of the four legs. The lateral rotation of each limb is achieved with the servomotor that fixes the leg to the torax. After the iterations, I ended up with a functional spider robot.

For the mechanical structure, I laser-cutted MDF and then assembled the pieces.

CNC machine cutting the mechanical parts of the spider robot — **First image:** CNC machine making the mechanical parts of the spider. **Second image:** Building of the spider's torax.

Assembly of the spider robot thorax — **First image:** CNC machine making the mechanical parts of the spider. **Second image:** Building of the spider's torax.

Regarding the electronics of the spider, it has a 9 DOF IMU (for measuring the 3D orientation), it has a current sensor (to measure the amperage consumed during the gait), and other components.

I developed the robot’s walking algorithm using genetic algorithms and supervised machine learning to optimize a reward function, without using reinforcement learning techniques. This spider robot later served as the foundation for a scaled-up platform I designed to navigate uneven terrain for landmine detection. That extended version was presented as part of my bachelor’s degree thesis.