Why is my robot not perfect? (part 2)

So here is the follow up to the post I made last week. Click here to refresh your memory.

There were a few different points of view with the theory so what better way to proceed than some real live tests.

Test Setup:
NXT robot, 2 wheels on a smoothish table.
2 white lines, 500mm apart
Program was written to wait 2 seconds then drive forward 1024 degrees. (the 2 seconds allowed the robot to settle and let me get my hand out of the way before it started driving)

1st test
75% power 1024 degrees, unloaded. I ran this 3 times and it was spot on in every case.

2nd test
50% power 1024 degrees, unloaded. I wanted to try and eliminate slippage with the surface of the table. If there was slippage at high power, it would be less at low power. Again all 3 runs were spot on.

3rd test
75% power 1023 degrees fully loaded. I found a nice heavy book to place over the top (2.2kg). The wheel does deform by a noticeable amount.

This time when I ran it, the robot came consistantly 30mm short. Vary the power and get the same result, 30mm short.

So if there is no slippage with the table, and changing of the wheel diameter does not affect the distance the only thing left is slippage between the wheel and the tyre.

I got some whiteout and marked both the hub and the tire and ran the experiment again. Turns out there is a small amount of slippage, although not enough to account for all the error.

Conclusion:
I think it's a combination of hub/tyre slippage and slightly deformed wheel diameter. The rubber is soft enough to compress itself slightly changing the diameter.

What do you think? Post in the comments.

--
Damien Kee

Celebrating 25 Years of MINDSTORMS

In celebration of the 25th Anniversary of MINDSTORMS, we take a trip through history. Please also visit ROBOTMAK3RS Community every week as we highlight different projects all through 2023 in celebration of the anniversary. Some of the early history is based on the content shared by Coder Shah in our MINDSTORMS EV3 Community Group . Some of the text and links may have been edited from his original posts for consistency and clarity. 1984 - Kjeld Kirk Kristiansen watched a TV program called "Talking Turtle," where MIT professor Seymour Papert demonstrated how children could control robot "turtles" using LOGO, a programming language he developed. 1988 - The collaboration between MIT and LEGO resulted in LEGO TC Logo in 1988, which allowed students to control LEGO models using computer commands. The video shows Papert demonstrating TC Logo. 1990 - LEGO TC Logo was hampered since the robots you built had to be tethered to a personal computer. LEGO and MIT...

Celebrating MINDSTORMS with a Remix - Part 3

The ROBOTMAK3RS continued their celebration of the 25th Anniversary of MINDSTORMS through these Fall and Winter remix projects. Each ROBOTMAK3R was tasked with selecting one LEGO set of their choice and combining it with a MINDSTORMS set. Below are the five amazing models they came up with. Braill3 by Jerry Nicholls Braill3 is an EV3-based LEGO Braille bricks reader. This robot uses its fingertip, made from three touch switches, to read messages written using the LEGO Braille bricks and will speak out what it detected. If it sees a simple maths problem it will attempt to solve it and give the answer as well. To learn more about the process of creating this machine, read Jerry's blog . Braill3 can be viewed here . Set Review: The Braille Bricks set is well thought out. The ratios of the letters is suitable for general use and the addition of some punctuation and arithmetic operators is excellent. There is a card showing what bricks there are and their quantities, but no form of sort...

Ghostbusters R.T.V Remix

Nino Guba is from Torrance, California, USA. He played with LEGO as a kid, but growing up in the Philippines, it wasn’t something he had easy access to. He only got reintroduced to LEGO when he moved to the US and had kids of his own. When his sons were younger, they received LEGO sets as gifts, but as they grew older, the sets got put into storage as their interest faded. Fast forward a few years, he started coming up with his own product ideas and thought about how he could quickly prototype them. That’s when he discovered LEGO MINDSTORMS—and was hooked! He raided his kids’ old collection, got everything organized, and now he's designing and building his own creations, blending his coding skills with LEGO robotics to bring ideas to life. Tell us about your Ghostbusters Remote Trap Vehicle (R.T.V) project. This project is a LEGO Technic adaptation of the Ghostbusters R.T.V.—a ghost trap converted into a remote-controlled vehicle. Its companion build is a prop replica of the Futaba...

ROBOTMAK3RS Blog

Search This Blog