At the beginning of February I posted a teaser for what I was calling an open source robot. This is a robot that I put together for my own use which is more complex than say a clawbot but not quite at the level of a full competition robot. The reason that I built this was so I had a test platform for the various software examples that I post as well as being able to test student code when they have problems. The original teaser thread is here.
At that time I had planned to release some detailed explanation of how the robot is built so that anyone who wants can copy it. I’ve realized that I’m never going to find the time to document the robot to that level of detail so I’ve decided instead to just post what I have and leave it there for now.
A 4 motor drive with mecanum wheels using 393 motors set for torque. The motors directly drive the wheels. Each motor is encoded using a VEX integrated motor encoder. The drive uses the 25x25 Aluminum chassis kit as its basis.
Two 393 motors set to torque drive the arm system through an 8.33:1 compound gearbox. The arm is able to move through approximately 270 degrees. One of the motors uses an IME for feedback into the arm control software, however, as an alternative the arm is setup to allow either one or two potentiometers to be used as feedback. Limit switches are installed that are used by the software to limit movement at full forward and backward limits of travel.
The intake is currently a scoop style intake that uses two 393 motors set to torque with a 3:1 gear ratio. A quadrature encoder is used for feedback into the intake control software along with a limit switch that is used as an index for the encoder. The intake is able to move through a full 360 degrees.
In addition to the 5 IMEs, quad encoder and limit switches, the robot is fitted with the following sensors.
Three line tracking with adjustable height.
Bumper switch for emergency stop or other software control.
LCD display for user input and status.
Yaw rate gyro
The full BOM for this robot, including control system, is as follows. These are the parts that you would need to order to be able to build this from scratch, I will post another BOM at some point with the quantities of each individual piece.
You can download this as a spreadsheet from the link at the end of the post.
There are links at the end of the post to a 3D pdf file and also the Inventor database (2012). The Inventor file really needs more cleaning up, the root folder is called DemoBot and the top level assembly is HB_Full.iam. Set the project to point at DemoBot/HB_Full.ipj.
A simplified version of the software is linked below, this allows driving using joystick channels 3 & 4 for forwards/backwards and strafing, buttons 8L and 8R for rotation, buttons 8U and 8D for manual arm control using PID and buttons 6U and 6D for the scoop. The arm and scoop are not synchronized in this version, however, the scoop will level if the arm is lowered too far. I will post a much more complex version after worlds.
Inventor database (large file 45MB)
3D pdf file (even larger file, 92MB)
Simplified control software (needs ROBOTC V3.51 or later)
Please don’t quote this post as I linked to all the images rather than attaching them.