# robotics

## Key Control Strategies Emerge in Spring Loaded Inverted Pendulum Traversal of Slippery Terrain

Last week I returned from the Dynamic Walking 2017 conference, where I had a poster and five minute talk on some of the numerical trajectory optimization work I’ve been doing […]

## Legged Helicopter Landing Gear

One of my biggest projects to date is a legged landing gear that allows helicopters to land on uneven terrain with large touchdown velocity. For a quick overview, please see […]

## Optimizing Trajectories for the Spring Loaded Inverted Pendulum over Slippery Terrain

Previously, I’ve written short introductions to numerical trajectory optimization here and here—if you’re unfamiliar with the basics, I recommend you check those out first. This write up expands upon a section of my […]

## Tutorial: Direct Collocation Trajectory Optimization with Matlab

In the previous tutorial, we focused on single shooting trajectory optimization, which involved time-discretizing the control input and simply integrating the dynamics. The desired end state was then added as […]

## Tutorial: Single Shooting Trajectory Optimization with Matlab

Numerical methods for trajectory optimization have become increasingly popular for analyzing the motion of bipedal spring-mass walkers, whose complex nonlinear dynamics make analytical solutions often infeasible. When I began looking into trajectory […]

## 3D Printing Inaccuracies with the Lulzbot Mini

A few months ago, I bought a LulzBot Mini to print parts for a robotics project. Despite its rather goofy name, the machine itself is great, especially for the price. […]

## Optimizing Retraction Reflexes Using Reinforcement Learning based on Particle Filtering

As part of my development of a legged helicopter landing gear (more on this later), I started studying ways to minimize landing impact using a combination of leg retraction (active impedance) […]

## Relationships Between Current, Angular Velocity, and Torque in Position-Controlled Servos

TL;DR I did some experimentation on whether or not it is possible to estimate the shaft torque on a cheap, position-controlled hobby servo using current and angular velocity. A paper […]