Scout - Magic Smoke! EEK!

ultraweasel · November 1, 2017, 1:36am

Hi,

Well, having given my new Scout a ‘Hip Replacement’ - a new servo was DOA, I fitted a warranty replacement and it works fine.

It can now stand up! Yay!

Then the magic smoke appeared

The +ve lead from the main servo battery (6v, 2800 mAh) decided to short out to the -ve lead for the 9v logic supply.

With my lightning fast reflexes, I unplugged the battery and saved the day…

Luckily no damage.

Now need to tweak the SSC-32U servo offsets to balance / align the servos neutral positions to provide an accurate “starting position” for gait developement…

(It’s all pretty close, but I reckon that a couple of degrees here and there to improve alignment of the servos will pay dividends in the future).

Now gotta get the Lynxterm working on my Win 7 VM (Using a Debian 9.1 host with a Win 7 VM). Anybody have any bright Ideas regarding getting the bugger working? Any help will be appreciated!

Cheers,

Ultraweasel.

innerbreed · November 1, 2017, 8:55am

well done for keeping it alive.
Iv been looking over my gait flow to get an idea of the best approach. I think i am close.
Not sure if this will help. if i can remember you are making sequences rather than controlling with Inverse Kinematics?
Here is my current gait.

[code]void GaitSelect(void)
{
//Gait selector
switch (g_InControlState.GaitType) {
case 0:
//Biped Gait 12 steps
'GaitLegNr(cRightLeg) = 1
'GaitLegNr(cLeftLeg) = 8

NrLiftedPos = 1;
HalfLiftHeigth = 1;
LiftedMiddlePos = 5
TLDivFactor = 13;
StepsInGait =9;
NomGaitSpeed = 60;
break;}}[/code]

image.ibb.co/k5EiTG/biped_gait.jpg

ultraweasel · November 6, 2017, 10:25pm

Hi All,

Well, I finally got my Win 7 VM working with all the software

Tweaked the SSC-32USB servo offsets to (hopefully!) align the servo positions…

At least the little guy is standing upright and level.

Now, having got all the software and drivers that I believe I need, I reckon I’m good to go

Just been working out the servo directions - left leg and mirror image right leg…

Next step is to determine the travel limits for all the joints - don’t want to be driving servos beyond their installed limits!

Fun times ahead!

Cheers,

Ultraweasel.

innerbreed · November 7, 2017, 1:05pm

great look forward to seeing it.

ultraweasel · November 9, 2017, 11:47pm

Hmm,

Just been thinking about how to use the SSC-32 Sequencer effectively…

Now, with a Scout (or other bipeds?) using (Hitec 5645MG) RC servos to control joint movement, out of the box, Hitec servos are CW rotation (i.e. 1500 uS+), CCW is 1500 uS-)

Now, taking my Scouts left leg as a ‘datum’ for servo directions - i.e. left hip forward, requires 1500 uS+ (CW) but right hip forward requires 1500uS- (CCW).

This, to me is complicating the issue - I’m a simple creature at heart, so was thinking that if I reversed the direction of my digital servos for the right leg, I would have an easier time of programming motion - e.g. either leg forward is 1500 uS+, and backwards would be 1500- uS.

I’m thinking that because I’ve got the Little Guy sat on the floor in front of me, having the +/- (Y axis) rotation being the same for each leg should make my life easier?

Any thoughts?

My aim with this project is to get it ‘right’ from the get go.

I have not even started to think about getting my Little Guy walking - I’m trying to get the basic foundations solid.

Any comments will be most welcome - I’m a total, naive, beginner with Robotics!

Cheers,

Ultraweasel.

innerbreed · November 10, 2017, 8:20am

If you are looking to symmetrize your setup rather than mirror it you could just plug in a servo signal reverser or hack the servo directly but that would mean taking it apart. its not a big deal and would look tidier than having additional wires.
I think if it helps you work with the scout better them go for it. If you have a solution to an issue then use that to better your project.

I personally wouldn’t. I would try and remain conscious of the set up and just work with it but thats just me.

Still waiting to see this little guy.