Looking for Info to build a small 4 wheel wireless vehicles.

Simon Ampleman

Hello,

·· I would like to build a small 4 wheels vehicle·with wireless control that will perform some automated precise task in my house. I want very strong torque and·low speed.·I can easily use 12V motors with gearbox for the wheels but I have no idea how could·I rotate the vehicle left or right precisely, I thought of a stepper motor at first, but I have no idea if this is the right choice for·the·size and weight of the vehicle... around maybe·2 to 3 feet square... and·easily·25 to 50 lbs. For the electronic, it's fine, I will put a propeller, a vdrive1 and a linx rf rx-tx 3000 feets rf module.

···Is there a book, or website that exists·that explain·or sell·kits to achieve this ? I know that price will be high...

Thank you!

Simon···

Rayman

I'm interested in hearing what people have to say about this, because I have something in mind along the same line...

Stepper motors are really nice, but consume a lot of power. I guess the first thing you must decide is how big a battery can you use and how long does it need to run on the battery...

I think servos are fairly low power, but are usually plastic, which I think limits them a bit for heavy loads...

Dgswaner

The Motor/wheel combo that parallax is releasing soon is perfect for what you want. as far as doing "specific tasks" I've looked into this a lot, you need to research on Odometry... using encoders to keep track of movement and then calculating a position. I've seen videos of bots drive around a room and return to almost the exact spot.

I have a 4 wheeled 17" diameter and 2'6" tall bot. I'm working toward this goal but I'm trying to get over the "SPIN NOOB" hurdle and get my bot all the needed hardware to function. I'd love to help if I can. or just get feed back from you on your project.

This is where I started it's a lengthy post but a lot of people added a lot of good info. This post sums up my ultimate goal. hopefully in the near future I'll be working on the main goal.
http://forums.parallax.com/showthread.php?p=661633

Might I suggest:

• A bot with a zero turning radius. I found it almost a necessity for getting out of tight areas in my home.
• Use at least a 6" diameter wheel. with that amount of weight smaller wheels will "sink" too far into thick padded carpet. making it hard to turn and move.
• keep the center of gravity as low as possible. my bot was about 5" off the ground and has tons of torque it would try to climb walls if I didn't stop it. This resulted in it tipping over if it hit an object big enough that it could not push out of the way. I've fix the problem but it was a massive overhaul.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

Post Edited (Dgswaner) : 12/3/2007 11:46:12 PM GMT

Simon Ampleman

That is very appreciated and it represents a big part effectively of the AI and·movements of the robot.

However, my big challenge (for me) is more in the hardware and methods necessary to build a mid-sized robot. Everything I see on the web describes how to build a very small robot that can follow a line... That is not what I am looking for... For example, I want, for my first project, to build my own lawnmower with the motor of a standard gaz powered lawnmower... I would simply add a new frame, wheels, motors and·precise direction control and relays to drive it from a propeller with a wireless control... That is a lot of weight... I don't want to buy some 50$ motors each to finally see that they are not made for this purpose... Or some expensive·stepper or servos to control the direction only to see it cannot move the steering at all... I see some information on how to build battle bots that we see at TV but they sell kits for like 3000$...·They include their own electronic, weapons, flames, powerful RF system, charger, etc... That is too much... I thought that maybe someone here knows that I could use the motors from a car to save a lot of money for example... Things like that.... Probably that there is website devoted to build mid-sized robots from scratch... ?

The navigation of the vehicle is the next step, I have some knowledge of DGPS, odometer, gyro, accelerometer, AI, pathfinding that I will put together to build my algorithm...·And that is only software with a few sensors, that is stuff I am more used to work with. My first test is to record the whole static sequence of movements received from the Wireless device, and I would playback the same sequence again when I want the robot to execute the same work again, starting at the same initial position. It won't probably be precise at all, but it won't require any intelligence or extra components for the first firmware. I will add the necessary intelligence or hardware step by step after I see it executing its job for the first time, that will be a lot of satisfaction.

Best regards,

Simon