An XRP Mecanum Wheel Robot

The XRP is an open-robotics platform designed to help you learn engineering, robotics, and software development. As an educator, I wanted to assess the ease of use of this platform for someone with limited prior experience. Although my FTC robotics team builds and codes great robots, I have a basic understanding of Tinkercad, and my programming knowledge is limited. I'm also 63 years old. This is my journey.

Purchase the following supplies (links in supporting file):

1. Experiential Robotics Platform (XRP) Kit
2. Mecanum Wheels, 60mm
3. Hobby Motor with Encoder
4. PLA filament in the color of your choice.

You will also need access to a computer and a 3D printer.

Using Tinkercad, make a copy of the standard XRP chassis. Cut off the caster wheel section of the chassis using a box shape.



Tinkercad has to re-render each shape in a large modified model. I like to save my model as a solid shape periodically to avoid corrupting my model.

Since I want the final robot to fit in an 8-inch sizing cube, I have to cut down the rear end of the chassis. The dimensions are in the photos.

This will save your progress thus far as a single shape.

Cut off the XRP channel on the front, leaving at least 1mm cross support.

This saves the half-chassis as a solid shape.

Make a copy of the board and power box

At this point, the CAD file is quite complex and should be saved as a solid shape one last time.

Add two 1 mm high boxes to cover the logo.

The Chassis is now ready to print. Be sure to add supports and print at 20% infill or greater. The frame must be sturdy so that all 4 wheels stay aligned. This will be a 12-hour or more print.

Screw the wheels onto the motors. Pay attention to the way the treads face. Attach the motor cables to the motors. Slide the motors into the chassis. Feed the motor cables up through the holes in the frame. Add batteries to the battery box and slide it into the power box. Flip the bot over and slide the XRP board gently into the power box slots. Carefully attach all motor cables. If you want to add the servo attachment, print it and superglue it to the front crosspiece.

Okay, this is where my journey got really hard! There are several great online tutorials for the XRP robot, such as the Experimental Robotics Platform and the Digikey article on the Mecanum drive. Unfortunately for me, the last computer language I was proficient in was BASIC, but my brain executed a (Delete*.*) many years ago. I needed help, but was having a hard time figuring out the math and logic. I turned to ChatGPT for help. This was an amazing AI teacher. When I got stuck, it slowed down and explained everything to me like I am 63 (I am)! I highly recommend you work with ChatGPT or a real programmer to learn the ins and outs of this program. Download these files to your computer. Go to the XRP code editor and upload these files to your XRP module. They need to be saved into specific subfolders to make sure the bot can find them. The pictures show where to save each file.

Open the pestolink_mecanum.py file in the XRPCode editor. Change the robot name in line 27 to your name. Save it to your XRP.

You are now ready to drive!

Attach a USB joystick to your computer. To make this work, you need to connect your robot to your computer using a USB cable, not Bluetooth. Start at the XRP code editor and open the Pestolink_mecanum.py file. Hit run. Make sure the robot's power button is on. Unplug the USB cable from the robot.

Go to the PestoLink site. Connect your robot. Drive your robot!

I didn't like that the robot processor and all the wires were exposed, so I created a cover to keep them all hidden. This cover must be affixed with tape or Velcro because you will need access to the board to program or turn it on.

So. It turns out that I can do this! You can, too. I hope this instructable brings you robot happiness. Happy Birthday, Instructables! Here's to 20 more! You can find my CAD files here: XRP mecanum chassis