hexapod collapse

[René van den Broek]

In RC mode things like to work normal. But with the gamepad is in W1,2,3,4 or D1,3 mode and doing nothing for a while (approx 5 seconds)the hexapod collapses. The servoś are no active any more. When activating with one of the gamepad buttons movinfgworks again.

This does not occur in D2,4 and F1,2,3,4 mode. This all start happening when I was trying to record on and sd. Any ideas?

[vorpalrobotics]

In order to save power and extend battery life, the hexapod deactivates all servos after about five seconds of inactivity.

However, if your servos are adjusted properly, the robot should continue to stand there after power is cut. If it is collapsing when power is cut, then that probably means the legs are not standing "high" enough in the normal standing position. If the standing position of the robot is too "low" then natural friction between the leg components will not be enough to stop it from falling under its own weight. But if it stands "high" enough, the correct amount, then it can stand there with power cut.

You can adjust how high the robot stands by default by using the "Trim mode" feature (so you will most likely not need to do any reassembly to fix this unless the servo horns are so far out of whack that its beyond the trim mode adjustment max value). This only takes about 5 minutes but everyone should always trim up their servo positions. The servo horns (for both hips and knees) should come out straight from the servo at a 90 degree angle, when the robot is in "Adjust" mode. Like this:

A complete guide on how to trim the servo horns is here: 

           https://vorpalrobotics.com/wiki/index.php/Vorpal_The_Hexapod_Trim_Mode_Guide

Hope this helps!  If you still have the issue after trimming all the servos, then put the robot in "Adjust mode" and send me a picture showing a close up of some servo knee positions so I can judge whether they're coming off at 90 degrees or not.

-Steve P.

[René van den Broek]

Thank you Steve for your quick response. That did the job. I trimmed the servos and it works now. The problem started when I mounted a gripper. Because of the extra weight it collapsed :)

Question: why does the power save not in D2,4 and F1,2,3,4?

Regards René

Op dinsdag 21 november 2023 om 16:38:12 UTC+1 schreef vorpalrobotics:

[vorpalrobotics]

Oh, I haven't looked at that particular code in a few years but I think it's because those modes have fewer than all four legs on the ground and if power were cut then the remaining legs would not be able to support the weight and they'd sink down. Modes where all six legs are on the ground when standing can cut power without having that happen assuming servos are all trimmed.

That's definitely true of all the F modes and D4 ("hands mode"), but actually I'm not sure about D2 because all the legs should be on the ground in D2 (ballet mode), just standing in a higher position ("on pointe"). Now I'm curious, when I'm not so busy I'll take a look at that. It could be that there were problems keeping the "on pointe" stance stable with power cut.

When I'm demonstrating these robots and letting kids test drive them, this power saving really extends the battery life a lot. In fact when someone stops testing the robot I always make sure to put it back in D1 mode so that the power does get saved. (For example if someone leaves it in one of the F modes the servos will keep sucking down power even though nobody is driving the robot!)