Servers by jDrones

Limiting min/max servo-output on heliquad

(Max Drougge) #1

Hello.
I’m using a heliquad (http://ardupilot.org/copter/docs/heliquads.html) with pixhawk cube. My servos max/min outputs are too great if used through their entire span. I need to limit these ouput so that they do not stall.

Do I do this by simply adjusting the max/min values in the “Servo output” in mission planner? I’m seeing a problem that my heliquad is yawing to the left when I try to take off. Could this be a problem with min/max/trim setting of the servo outputs? I don’t have a log file to share unfortunately.

(Ahmed Mohamed) #2

The output of the servos can be limited by the setting different configuration to the ESCs setting a limit to its output.
Regarding the yawing to the left.
I think the calibration of implemented IMUs on the pixhawk is the problem.
check this link:
http://ardupilot.org/dev/docs/extended-kalman-filter.html

(Bill Geyer) #3

@Max_Drougge I don’t believe you will be able to set the output of the servos through the SERVOX_MIN and SERVOX_MAX parameters. you will have to use H_COL_MIN and H_COL_MAX are used to limit the collective output. I’m not sure what would cause it to yaw left at the moment. Could you post a param file. That would help me understand your setup.

Thanks,
Bill

(Max Drougge) #4

Hello.
I did set the SERVOX_MIN/MAX to my maximum/minimum servo movement without stalling. The problem seemed to be that I set my servo hover position to correspond to 1500 throttle output from the RC transmitter. However, at 1500 throttle the YAW from the RC control has no to little effect on the servos. Once I did change my RC throttle output to be from 1500-2000 (where around 1750 is hovering) it seems to work fine. I’m not sure why it is this way? Could it be because the Heliquad can be used for inverted flight and thus RC input 1500 would correspond to “0” throttle? I’m confused.