Boat Skid Steer SetUp Issue

Configuring my first skid steer boat model, and must be missing something basic in pixhawk setup, as I can’t even get manual mode to work.

Boat has twin forward-fixed trolling motors with ESC’s correctly configured for forward/reverse.

Taranis transmitter is configured with single stick for throttle and steering, with mixer set up to properly mix throttle and steering for left and right motor thrust. This can be verified in several ways including RC_CHANNELS_RAW (Chan1 & 3) in attached T-log.

I have the following key pixhawk parameters set for skid steer:
SERVO1_FUNCTION = 73 (left throttle)
SERVO3_FUNCTION = 74 (right throttle)

Despite this, the thrust output from pixhawk, as seen in SERVO_OUTPUT_RAW (Servo1 & 3) in attached T-Log, shows all the thrust from the throttle going to Servo1, and all the thrust from the steering going to Servo2.

On a side note, not sure what role RC1_XXXX & RC3_XXXX parameters have here. RC1_OPTION (as well as RC3_OPTION) are set to 0 (“do nothing”) as there is no left or right thrust option.

Hope someone has some insight for me …and I’m not being an idiot.

2019-11-17 14-43-23.tlog (497.1 KB)


First thing I noticed, you do not need to setup a mixer in the Taranis. You only need two independent channels for steering and throttle.
Otherwise the Taranis mixes the two channels and ardurover does it again, effectivly unmixing both channels. The servo_out throttle left, throttle right setting is what tells ardurover to do skid steer mixing.

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AHA - so I was an idiot. THANK YOU Sebastian :slight_smile:

Manual mode working fine now. Will continue tuning and testing auto mode. More questions to come I’m sure.


This is a super old thread, so I’m not sure if anyone is still monitoring it. I’m now trying to setup my first skid-steer boat. I’m using a Spektrum DX8, and I have mapped the sticks so that throttle comes from the elevator stick, so that stick center will make the motors stop. I’ve setup the servo functions for left and right throttle. In the Radio Calibration tab I can see the RC inputs for throttle and aileron come in, but on the Servo Output tab, I do not see any response - both output channels remain at 1500.

Is there someplace else where I indicate that I want skid steering? Searching the full parameter list for “skid,” the only thing that comes up is the mix ratio, favoring turning or throttle. It’s set at the default value of 0.5.

Other settings: Frame_Class=boat, Frame_type=0. I’m not sure what else I need to do.

Update: I just rebooted the autopilot to see if that would make a difference, and indeed it did. I now get servo outputs for left and right throttle, but only when armed - which is good. However, on both channels the range appears to be from 1500 to 1900. With the stick centered, both output channels are sending 1688. With the elevator (mapped to throttle) stick all the way back, both channels go to 1500. Min/max for both channels is set to 1100-1900, with trim at 1500.

2nd update - I just recalibrated, and that fixed the motor centers. Looks like I might be ready to try driving motors.

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Great stuff. good luck!

I just discovered an interesting bug/feature, but I’m not sure if it’s a bug with regard to Ardu or the ESC. I was just testing out a motor, but with an ESC that I had not setup for bi-directional operation. The RC controller was setup to drive it using roll and elevator. I pressed the hardware safety switch and armed. The motor initially wouldn’t spool up since it was at half throttle. I lowered the elevator until the ESC detected low throttle and armed. The motor ran fine. I then left the RC stick centered, with the motor at half throttle, and disarmed the system. The motor remained running at half throttle, but was not responsive to stick inputs. I then pressed the hardware safety switch, and that shut off the motor.

This is sort of a misuse of the system, as 1500 PWM should be idle, but it’s interesting that valid PWM values are still sent when disarmed.

Set MOT_SAFE_DISARM to 1 and Ardurover will not send any PWM signal while the vehicle is disarmed.

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Thanks for the help, that resolved the issue.

I’ve now got everything working OK in manual. I’m getting ready to try some controlled modes. I was looking for some form of heading-hold mode. I thought maybe STEERING mode would do it, but on the bench, when I switch to STEERING mode, neither motor will run. ACRO mode seems to be the closest, but if that’s like copter and plane, I think that just uses gyro data, no compass. Is there a heading hold mode that utilizes compass for heading data?

Hi @Kevin_Jones,

Acro mode is what you’re looking for I think. The pilot controls turn rate and speed. It does use compass and gyro for the heading estimate.

It seems to track really well in ACRO mode. I wasn’t sure if that used compass or just gyro data. Thanks for the feedback.

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One more thing. It seems to stop at each WP and pivot on a point before heading to the next WP. In Copter I usually am able to avoid this by setting the WP radius larger. Is there a trick to getting this to work with Boat? I’m fairly sure it’s a parameter I just have set incorrectly.


Great that you got it working. We’ve got a wiki page here re tuning pivot turns. If you wanted to disable pivot turns completely you could set WP_PIVOT_ANGLE to zero.

Thanks for the feedback. I’ll give the pivot turn tuning a try…

Regarding ACRO mode, the boats only seem to track correctly in ACRO mode if they are trimmed well in manual mode. Are we sure that compass is used there?

The servo trim values are the starting point for all assisted modes. If they are misaligned, the rate controllers need to fight that along with any disturbance or cross track error, so performance will indeed suffer.