Hello all, this was our first season using swerve drive (L1 sds mk4i, w/ falcons) and while our code has performed amazingly, we had at issues with the strength of our swerve drive (i.e. we were easly pused around, even by L3 geared bots, another team even said we needed to boost our power). As of now, our motors are limited to 80A on non pro Firmware, but we were woenderig if we could push it any further? Especially since we are makeing a switch to phoenix pro and FOC control? Ive seen people talking about running their falcons with 100+A limits, is this doable with FOC?
So, what current do you limit your drive motors to (or in the case of FOC, what current control authoritydo you give them)?
(If you can respond for either normal or foc control that woud be helpfull since our internal library has to support bolth phoenix 5 and pheonix pro)
What is the weight or your robot, do your wheels slip easily when pushing? Increasing the current limit probably won’t help if you are already traction limited.
Wouldn’t surprise me that a robot that is 125lb and with potentially heavier bumpers is able to push around a ~100lb robot. The only other thing you could try is making sure you are using wheels with more traction, what tread do you use and how often do you replace it.
Another possible issue is having the weight not balanced between the 4 wheels, causing some to slip easily but others to stall, not taking full advantage of all 4 motors, this is why tank drives would have the sides of the drive connected together so that the motors are pushing all of the wheels and not just each individual one.
Odds are, increasing your current limit won’t actually improve the “Strength” of your drivetrain.
If we’re referring to “Tractive Effort” (Pushing Force) then it’s a function of the Robot’s Weight x Effective COF - this determines the maximum amount of force the robot can generate with the Drive Train. From there, you apply the available torque to that force and solve for how much current would be required to generate this.
In this specific example - using L1 gearing, (8.X:1) - you actually have MORE Torque available at the wheel than all other MK4 options, meaning that for the same Wheel Torque (Output Torque), your motor will do “Less” work (Require less current in). This basically means that because your gearing provides a significant increase in output torque, you should actually be applying a lower current limit for “Ideal” Tractive Effort.*
*If you do the math, you’ll find that your drivetrain should be traction limited (able to spin wheels in place) somewhere around 60A of input current. Assuming the Current Limit is set to 80A as stated, odds are, in most pushing matches, rather than applying the maximum force possible, you’re actually spinning your wheels in place. Assuming all things are equal(ish) between two robots (Weight, Wheel Choice), the robot that spins it’s wheels first will usually lose the pushing match.
