Alternative to T200 control

I had never gotten thrusters to work smoothly off the servo channels so I took a thruster commander and mounted a servo one the potentiometers and it allows me to control T200s quite well. However, I have no doubt some off you will have immediate suggestions on how to achieve the same outcome much more efficiently so I look forward to hearing any feedback.

Hi @johng,

Am I understanding correctly that instead of doing

flight controller servo output
→ ESC → thruster

your current approach is

flight controller servo output
→ servo motor → potentiometer → thruster commander
→ ESC → thruster


Can you elaborate on what you mean by this? In particular,

  1. are you saying the thrusters were moving jerkily, or you couldn’t get the connection process to work smoothly or something?
  2. which flight controller board are you using?
  3. which autopilot firmware are you running?
  4. what SERVOn_FUNCTION values have you tried assigning for the extra motors (before you tried the thruster commander approach)?
  5. what are your RC_SPEED and SERVO_RATE parameters set to?

Hi Elliot

The thrusters have always moved jerkily when I have tried it through the servo channels. I used the standard set up of Pixhawk +Raspi 3b and now the Navigator and Raspi4, BR Heavy and Q Ground control with all the defaults set as they are when I downloaded everything. I knew it must be possible to change values to iron out the jerkiness but could not find anything to tell me what values and by how much. Perhaps you can spare the time to tell me what I should do instead.

I don’t really understand this - all the thrusters are controlled through servo channels. Granted there may be a difference between the MAIN and AUX pins on a Pixhawk, but on a Navigator all 16 of the output pins are controlled by the same controller, so unless you’ve got some broken hardware if one of those pin works for an ESC+thruster combo then all the others should as well.

Are you trying to use the extra thrusters as part of the vehicle’s motion control, or are they serving some other purpose?

For motion control they should have the corresponding SERVOn_FUNCTION configured as a MotorN output. If they’re supposed to have outputs that match other thrusters in your frame then you may be able to double up on the configured ones, but if all the motors contribute differently to the vehicle’s motion axes then you’ll need to create a custom frame with the appropriate thrust factors and assign the extra motors as Motor9 and Motor10.

If they’re acting as controlled peripherals (e.g. rotating a cleaning brush or something) then they’ll need to be assigned as a servo output, or as a faux camera servo or set of lights, with SERVOn_MIN/MAX set (likely to 1100/1900) and joystick button functions assigned as appropriate to be able to control them.

Hi Elliot.

Thank you for that.I am using the two extra thrusters for other functions than vehicle motion control. It was mainly when using a Pixhawk that I encountered the problems and assumed it was an Ardusub issue and likely if I follow your suggestions with the Navigator I will achieve the control I want.