4dof Quadruped robot (T-Hex type) AXIS

Lynxmotion Legged Robots
21

i found that the main reason for having so many steps is that it allows for a bigger bytetable to be used and there for smaller buildup in the bytes allows for a smoother cycle in the shift. going from center (128) to the left (100) or right (155) was very jumpy.

the table now moves at about 5 bytes per cycle rather than 20-30 in previous attempts.
you may also notice that i have only added X-axis shift for this. Z-axis may also need to be tested.

at the moment, as soon as the robot is started the body starts to shift Left - Right. even without walking. so i need to find the right way to add the code in so that it only starts shifting when walking. ?

22

Spreading out the shift is definitely a good idea.

But -100 and +55 from center? Wouldn’t that be off-balanced?

Yeah, I was going to ask about that! Z being for-aft is still a little weird.

Humm, I’ll bet that’s interesting to watch! How does it work with the various body shifts?

Alan KM6VV

23

Corrected table:

; (LF) (RR) ' 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, X_Axis_Shift bytetable 100,100,100,100,100,105,110,115,120,128,128,140,145,146,147,148,148,148,148,148,148,148,148,148,148,148,| 148,148,148,148,147,146,143,128,128,120,115,110,105,100,100,100,100,100,100,100,100,100,100,100,100, ; 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 ; (RF) (LR)

well when performing body moves it does look interesting as it almost looks like L1 & L2 functions are being used at the same time. :wink:

24

Well i think its time for a video! :smiley:

i have made the bytetable wider with values.

'Walking comp tables: ; GaitLegNr(cLF) = 28 ; GaitLegNr(cRR) = 40 ; GaitLegNr(cRF) = 3 ; GaitLegNr(cLR) = 16 ; (RF) (LR) ' 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, X_Axis_Shift bytetable 90, 90, 90, 90, 90,100,110,115,120,128,128,140,145,150,155,158,158,158,158,158,158,158,158,158,158,158,| 158,158,158,158,155,150,145,128,128,120,115,110,100,90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, 90, ; 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 ; (LF) (RR)

This is a short test but improvements are yet to be made. :wink:
i need to find a way to select the body shifting on command so its not running all the time.

Also a name is needed!
Vid:

25

I like it! 8)

26

I like the body shift.

I’m wondering, maybe if there was a slight torso “roll” (rotation around for/aft axis) while the 'bot shifts? Sorta “swaying” (staggering, sauntering, sashaying…) gently side to side.

Just thinking out loud.

I’m Impressed!

Alan KM6VV

27

Great work Jonny!

The walking part seem to work very fine. :smiley:

28

Well iv combined things iv learned from you to accomplish this. :wink:
The Bytetable works ok but im finding that it slows things down, or could this be the 50step gait that causes this!?

id like the shifting to be smoother and slightly quicker. ill try and get some more done on that part after the weekend.

29

ok well i have cracked it. now the body shifting is only active when walking and return to middle when J/Stick is released. :wink:

30

I will second (or is that third) the Looking great!

Kurt

31

Always nice to learn a few things!

I’ll bet it’s the 50 steps…

Looking forward to seeing more.

Alan KM6VV

32

i have made some progress but one thing im looking to do its make the shifting smoother. so far, here is the x shift table. i have tried to make the most of it 'but again i feel limited to making the numbers tighter as it would mean making the gait with more steps.

'Walking comp tables: ; GaitLegNr(cLF) = 28 ; GaitLegNr(cRR) = 40 ; GaitLegNr(cRF) = 3 ; GaitLegNr(cLR) = 16 ; (RF) (LR) ' 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, X_Axis_Shift bytetable 88, 89, 90, 91, 95,100,110,115,120,128,135,145,150,155,158,158,158,159,160,161,162,163,163,162,161,160,| 159,158,158,158,155,150,145,135,128,120,115,110,100, 95, 91, 90, 89, 88, 87, 86, 85, 86, 87, ; 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, ; (LF) (RR)

would there be a way of shrinking the amount of steps im using, i.e to say “24 step wave gait” but making a bigger table so i can tighten up the numbers. ?

any thoughts?

33

Make the table bigger? Do you mean more precision? Store values X8 (fixed point) math?

I ordered (I think) enough SES parts to build a set of 4 T-hex legs.

Alan KM6VV

34

correct. :wink: i would like to make the shifting and stepping smoother but with pace!

i can check the list for you if you wish?
Cool get building then, i wanna see pictures. 8) a whole fleet of T-hex Quads! or call them… DAUQ’s (pronounced Dukes)

…bed time i think!! :confused: :blush:

35

Hi Jonny,

On order:

4 ea Rubber End Caps REC-06 ] $1.75 USD (pair) $3.50 4 ea AT-01 1.5” Aluminum tubes AT-01 ] $1.50 USD (each) $6.00 4 ea HUB-08 tube connector hubs (flange) HUB-08 ] $8.00 USD (pair) $16.00 8 ea ASB-06 “L” connector brackets ASB-06B ] $5.95 USD (pair) $24.00 16 ea ASB-04 Multi Purpose Servo Brackets ASB-04 ] $11.95 USD (pair) $95.60 8 ea ASB-11 Offset “C” Servo Brak w/ Bearings ASB-11 ] $12.90 USD (pair) $51.60 4 ea ASB-10 long “C” Servo Brackets w/ Bear ASB-10 ] $12.90 USD (pair) $25.80

Of course, I had a few of the brackets, so I was able to cut down a little. Adds up too quickly! I’ll have to “steal” a pair of servos, HS485HB. And cut another 'quad chassis plate. I will leave my 4DOF “little cat” legs together, at least for a while.

I also ordered a pair of the new aluminum 'bot wheels and hubs for my MicroMoose.

Let me know when you’ve got another cool software build ready to release!

what, me sleep?

Alan KM6VV
Wireless

36

yep your list looks fine. be sure to post some pics of your “MicroMoose”.

37

just to point out i am using 4x HS485 servos on the coxa’s and 12x HS645’s on femurs/tibia’s. works fine. cuts cost too. :wink:

38

Also alan, another thing about the set up…

The below picture illustrate how zenta calibrated the femur, tibia and tars. In this position all joints are calibrated to the 0-deg position.
http://i531.photobucket.com/albums/dd355/innerbreed/file.jpg
Zenta pointed out the easiest way to solve the calibration part is to first set all servos to the center 1500 position and mount the horn so that the leg pose the 0-deg positions (like picture #1). Then snap out the horn from the femur and turn it 15 deg upward. Then snap out the tars horn and turn it 15 deg inward. Hopefully the leg should look close to the second picture.
http://i531.photobucket.com/albums/dd355/innerbreed/file3.jpg

download/file.php?id=251&mode=view

39

I think that’s what I’m going to do too.

Thanks!

Alan KM6VV

40

Thanks for the setup pix!

The stand is nice too!

So the knee is left at 0 deg then?

I’ll see how it goes.

Alan KM6VV