Nov 4, 2017

天行2025

This LEGO pendulum clock is truly practical to use as a clock: it runs for over 72 hours or 3 days, it is very easy to rewind in just a few seconds, and it can be accurate to within a minute per day. A screw on the pendulum bob allows precise adjustment of the effective length of the pendulum. The hands can be easily moved to set the time. These features all contribute to making it possible to have a real working clock made of LEGO requiring only a few seconds of rewinding every 3 days!

天行2025

One of the more interesting parts of the ball catching robotis the algorithm used to estimate the 3D trajectory of the ball while it is flying through the air. This post describes in more detail how this algorithm works. To start with, let’s define some assumptions and known parameters: The object we wish to estimate the trajectory of is flying through the air according to some parametric model \( \mathbf{traj}(t) \) mapping a time \( t \) to a 3D position \( \mathbf{x} \).

Feb 22, 2015

天行2025

Ball catching delta robot in LEGO This is a delta robotbuilt with LEGO Mindstorms to catch a ballthrown through the air. The robot is programmedusing ev3dev, an alternative operating system for the EV3 brick. It uses two NXTcam cameras to track the ball and estimate its trajectory in 3D. Here is a video of the robot in action. Lightweight pneumatic hand mechanism for catching the ball In order to catch a ball, a robot needs to be able to move very quickly and accurately.

天行2025

The purpose of LiveSPICE is to simulate circuits for audio signals in real time. Simulating a circuit requires solving for the relationship between the current state of the circuit and a new input signal, to produce the new state of the circuit. This post describes the algorithm LiveSPICE uses to evaluate this relationship quickly enough to run in real time. My hope is that this post fills what I found to be a gap in the literature I could find on solving this kind of system.

Mar 12, 2014

天行2025

LiveSPICE is a SPICE-like circuit simulation tool for processing live audio signals. The motivation for developing LiveSPICE is to help prototype guitar effects and amplifiers, without requiring constructing a physical circuit or waiting for an offline simulation to run to try it out. With LiveSPICE, you can design the circuit in an easy to use visual schematic editor, and simulate it using your real instruments as input signals and your speakers as the output, in real time.

Apr 12, 2012

天行2025

This app is no longer available for download. I have not had the time to keep the app up to date as Android evolves. It is still available as an open-source project. Touchpad is a free Android app to enable you to control your windows computer from your Android device. It provides a simple multitouch touchpad interface to control the mouse, and accepts keystrokes from the keyboard on your device to send to your computer.