Seeing the Light with RPLIDAR

A project log for OSCAR: Omni Service Cooperative Assistant Robot

A project aimed at developing a humanoid ballbot platform.

Poh Hou ShunPoh Hou Shun 10/04/2015 at 09:350 Comments

Good news everyone (in Professor Farnsworth's voice)! The first of our navigation sensor the RPLIDAR has arrived. We gotten ours from Seeedstudio for a little under 400 bucks. For those who are not familiar with the RPLIDAR, it is probably one of the cheapest lidar one can get on the market, without getting into "Poor Man's Lidar (PML)" . It has a range of about 6 m with a refresh range of 5.5 Hz and 2000 samples/s at 1 degree resolution. It works by sending out a modulated (intensity I supposed) laser beam which gets reflected from an obstacle. The return signal is then detected by an onboard camera and decoded (probably some timing measurement goodness here) for the distance measurement.

Included in the box is the RPLIDAR itself (fortunately), a 7-way ribbon cable, and some kind of serial to USB adapter with builtin power suppy for the lidar and its motor. For testing, using the adapter is probably the best beg as it just streams the measurement through USB. However with the adapter one cannot selectively control the power to the motor. Using the demo program we easily verified that the lidar was working.

An issue that we faced with our RPLIDAR was that the spinning head does not seem to be balanced. As it spins it was introducing a fair bit of vibration, but not enough to be a showstopper. Maybe in the future we will try to balance out the head.