The Omni-Directional Mobile Robot Base kit (RB-Cyt-88)

[daltonschool]

I am in 7th grade at a school in New York City. Our robotics team would like to compete in Robocup Jr. soccer in April 2013 using Arduino Microcontrollers. We don’t know if we’ll have enough time to build and program a robot, but we want to try anyway. The Omni-Directional Mobile Robot Base kit (RB-Cyt-88) looks like it would fit our needs in terms of omnidirectional wheels and motors, but the RCJ rules require that we build our own chassis. Also, our chassis optimally needs to be exactly 8" diameter, with a notch for the ball (and a place for the kicker and dribbler). The robot would need to move at least 1/2 meter per second, but faster is better (although it needs to be able to move slowly as well).

Here are our questions:

1. Your kit uses Cytron 12V 185RPM 11oz-in Spur Gearmotors (RB-Cyt-33). We would get the same motors, but do you sell mounts? If not, how could we mount them?

2. How do we connect the motors to the omniwheels? We would like to use a wheel that’s about 50mm. (RB-Dag-17)?

3. We see that your kit does not include encoders. Does that mean that the robot will generally move in a relatively predictable direction without encoders?

4. We need motor controllers for the robot. We were thinking of ordering three MegaMotor shields (RB-Rop-01). If we chose not to use Arduino shields but controllers that we would manually wire to the arduino (i.e. not stacking them), what controllers would you recommend and why?

Thanks for your help.

Spencer

[cbenson]

1. Your kit uses Cytron 12V 185RPM 11oz-in Spur Gearmotors (RB-Cyt-33). We would get the same motors, but do you sell mounts? If not, how could we mount them?

Unfortunately the mounts are not sold separately

2. How do we connect the motors to the omniwheels? We would like to use a wheel that’s about 50mm. (RB-Dag-17)?

RB-Nex-24 is a great wheel, and can be matched with either RB-Hit-78 (CR servo) or RB-Dfr-51 gear motor (with RB-Dfr-46 encoders). You can make a custom hub for other omniwheels using 3D printing (if you have that available) or a lathe.

3. We see that your kit does not include encoders. Does that mean that the robot will generally move in a relatively predictable direction without encoders?

Generally yes, but consider that no motor is exactly the same, and friction can change slightly even on a uniform surface, so there is no guarantee the robot will move in a perfectly straight line.

4. We need motor controllers for the robot. We were thinking of ordering three MegaMotor shields (RB-Rop-01). If we chose not to use Arduino shields but controllers that we would manually wire to the arduino (i.e. not stacking them), what controllers would you recommend and why?

It depends on which motor you go with now…