Programming for Mecanum Wheel Chassis

[Ether]

Originally Posted by yank

Driving forwards, backwards, and turning works fine, however, we are not able to strafe sideways.

Put the bot up on blocks and tell us what each wheel is doing when you give a pure strafe command.

Also, post a bird's-eye (or worm's eye) picture of the bot so we can see how the 4 mec wheels are mounted.

[yank]

Originally Posted by Ether

Put the bot up on blocks and tell us what each wheel is doing when you give a pure strafe command.

Also, post a bird's-eye (or worm's eye) picture of the bot so we can see how the 4 mec wheels are mounted.

Pictures

The "top view" picture shows our robot from earlier this week when we put the wheels on. We have not moved the wheels at all, but we did change the gear ratio (originally geared for speed, now geared for torque, as seen in the "full bot" picture)

Unfortunately I don't have a video of the bot on blocks, but the wheels turn erratically (the reason we suspect it's a programming issue).

We did do some tests earlier with another program although we still had our old speed gear ratio at that point. The wheels spun as they were supposed to (left side wheels spinning towards each other, right side wheels spinning away from each other, and vice-versa for strafing in the other direction), but the robot moved diagonally (when we tried left strafe, it moved forward diagonally to the left, when we tried right strafe, it moved forward diagonally to the right. We thought that our robot did not have enough torque to strafe properly, so we changed the gear ratio to what it is now.

Was our conjecture about torque a valid one?

Thanks for your help!

[Ether]

Originally Posted by yank

The "top view" picture shows our robot from earlier this week when we put the wheels on.

I see only two motors. You are using four motors (one for each wheel), yes?

It looks like you are actually gearing up the speed from the motor to the wheels. Yikes. I don't know what kind of motors you are using, but if they are anything like FRC motors you need to gear them down. Way down.

[yank]

Originally Posted by Ether

I see only two motors. You are using four motors (one for each wheel), yes?

It looks like you are actually gearing up the speed from the motor to the wheels. Yikes. I don't know what kind of motors you are using, but if they are anything like FRC motors you need to gear them down. Way down.

Yes, we are using one motor per wheel. That picture was taken before we got all the motors on.

We geared the motors down yesterday (2:1).

[Ether]

Originally Posted by yank

We geared the motors down yesterday (2:1).

What is the free speed of the motors you are using?

[yank]

Originally Posted by Ether

What is the free speed of the motors you are using?

160 rpm (they're AndyMark NeveRest 40s)

[Ether]

Originally Posted by yank

160 rpm (they're AndyMark NeveRest 40s)

That's a gearmotor. It's already been geared way down (40:1)

Max power is only 14 watts. How fast do you need to go, and how heavy is that robot going to be?