Omniwheel Growbot prototype

Let's Make Robots Robots
1

I am new here and this is my second robot using a microprocessor. Electrinics in no problem for me but programming is new to me. I can see this bot will be alot more programming and tweeking then my first mini-monster Boe Bot (working on documantation). Spent around 6 hrs. just retrofitting the wheels. I plan on eventually going with 3 ultrasonic sensors or 2 Sharp IRs with an ultrasonic in the middle. Also planning on adding a 4 button R/C controller and mabe a compass. Not sure if the Parallax BS2ic can handle but will find out. For now I am just using the whisker bumper switch. I am using standard futuba continous servos and was wondering if direct drive small DC motors would give it more speed. It seems torque is not an issue with these wheels. Not many people have used omniwheels in the Parallax forum. I would appreciate any input from you guys that have expermentted with this type of robot. I already found 4 wheels are easier then 3. Thanks in advance.

http://www.metacafe.com/tags/omniwheel_growbot/

The more you learn, the more you find you don't know. It is neverending. Confucous 550 BC

Roam with eventual RC overide control

  • Actuators / output devices: Four servos modified for continuous rotation
  • Control method: Semi Controlled R/C eventually
  • CPU: Parallax Basic Stamp 2
  • Operating system: windows XP
  • Power source: 7.2 V NiCad sub C
  • Programming language: pbasic 2.5
  • Sensors / input devices: SHARP IR sensor, Ultrasonic sensors, mabe Compass
  • Target environment: indoor flat surfaces
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/omniwheel-growbot-prototype
2

im a BASIC programmer
so if you need a debugging…

3

torque vs gears

first of all: COOL ROBOT!

Even though torque might be less of av issue with omniwheels, I seriously doubt your bot will move with a direct drive motor. You will need to gear down to get enough force to move. There are several good options on the market, I’m not gonna make a complete list, but I’ll mention these three that I know are widely used in hobby robotics:

Solarbotic gearmotors

Pollolu Metal Gearmotors

Tamiya gearboxes (with motors)

To get an idea of speed, just meassure the circumference of the wheels and multiply it with the geared motors RPM. Too fast will make it impossible to controll, as inertia might make the robot continiue to travel after the motor power is cut. And to high RPM-to-weight-ratio wil make the bot skid and spin.

 

4

I have to agree
I’ve been a mentor for FIRST for four different teams since 2003, and I’ve seen a few teams at the regionals that used the omni wheels. Their autonomy attempts were shot since they kept over shooting their target spot and the thing wasted the 15 seconds they had trying to get back to position. So stay with slower motors for the omnis