|
Re: Swerve Drive vs Mecanum Wheel drive?
A lot of misinformation in this thread.
Mecanum drivetrains have a fraction of the traction that skid steers does. This really isn't debatable. There is no difference in traction between a good and a bad mecanum drive, they have the same 4 wheels touching the ground, if they are static there is nothing that makes them any different. The only difference is in gearing but that doesn't matter when the robot is sitting still.
Most drivetrains in FRC (especially with the advent of the 6 cim drivetrain) are traction limited, not limited by the power output of the motors. Our drivetrain is geared for ~24 fps in high gear and it's still traction limited.
A well designed swerve drive can have just as much pushing power as any tank drive assuming it uses the same tread material.
The maneuverability of mecanum or omni wheel drivetrains can be very advantageous for offense, however it's been proven time and again that they really can't do anything on defense. After watching over 400 matches just this season I can't even count the number of times I've seen a mecanum bot just get brushed aside by a tank or swerve drive as if they weren't even there.
Robots rarely have their wheels lifted off the ground. Nearly all pushing matches have both robots with all 4 wheels planted on the ground. Despite their weight shifting to the back wheels their force applied on the ground is relatively constant and it marginally affects a robots traction.
Mecanum wheels never behave the same as traction wheels. The rollers on mecanums make it so there is always a slight loss in efficiency since those rollers will always spin slightly unless you are going perfectly perpendicular to their direction of rotation. Also the rollers have a relatively smooth surface so even if the wheels are traveling perpendicular to direction of the rollers they still slip and cause a loss in efficiency.
It's not any easier to push a robot (on traction wheels) backwards than is to push it sideways assuming that it has enough power to at least keep it's wheels from spinning. It's the same amount of friction in every direction as long as the wheels are locked.
Do not take this to mean that mecanums are bad. Just stop saying that they can do things that they can't.
__________________
All posts here are purely my own opinion.
2011-2015: 1678
2016: 846
2017 - current: 3501
Last edited by themccannman : 12-04-2014 at 01:16.
|