Hey folks, using Rover 4.5.1 on a SpeedyBeeF405WING with VGEBY bi-directional 50A ESCs that don’t need (nor support) calibration, and Apisqueen U2 thrusters, on a boat with differential steering. The thrusters respond to input as expected, save for one aspect:
When I go forward, then let go of the throttle, the right thruster stops instantly (with a bit of a ‘click’, sounds rather hefty) whereas the left thruster nicely spins down to a stop on its own (in about 1/5th of a second).
When I go backward, then let go of the throttle, the same happens but the other way around: this time the left thruster ‘click-stops’.
This asymmetric behavior doesn’t seem right to me somehow. And I’m also not sure I want the thrusters to stop so suddenly at all—both for angular moment forces and motor longevity. Any ideas what might be up? The servos are set to ThrottleRight and ThrottleLeft in Rover, and all trims/mins/max PWMs etc are set identically.
Thanks! I’ve reversed just one of the thrusters in the AP params (and rewired the motor to undo the reverse). This seems strange (why would identical ESCs need different configurations?) but the braking behavior is the same for both thrusters now!
I also learned that ESC braking is not a necessarily bad for your motors, it just powers all 3 magnets in the motor to immediatly stop the motor coil (intended for flying drones, to prevent props from breaking when hitting the ground).
Check this video of the same thrusters, seems like they have the same behavior (foward looks a tad smoother than backward). Maybe they have it somehow built into the thrusters? https://www.youtube.com/watch?v=lsLD3dp1otY
Maybe! There also could just be quality issues? Or just the default way they sell a CCW thruster?
I’ve also noticed that one thruster maxes out a lot lower in rpms than the other one (the boat was going in circles when going straight :). To compensate I had to slow down the stronger thruster to match the weaker one by tweaking SERVOx_MAX. RPM range from 1480-1900 all the way down to 1480-1640 :-/
I think its just those ESCS, they look like something cheap from 10 years ago, I would replace them with a set of BLHELI32 controllers that have current monitoring. that way you can set a max current limit for each motor and it will stop the thruster burning out if something gets stuck in it. they also have FOC mode and DSHOT that makes them much smoother at low rpm.
I use them on my boats and I get full telemetry, so volts, current temperature and RPM from each controller in ardupilot.
Could be - though I get significant thruster response changes simply by swapping the 3-wire behind one unchanging ESC (exact same current/voltage/frequency etc).
But I thank you for this tip regardless, the features you mention certainly seem worth the price of admission! Do BLHELI32 ESCs generally support bidirectional use?
