need help with programming

Ownonono

i'm working on project of hexapod robot, the robot only use 3 servo. the problem is,when the middle leg lift the body it wont hold
because other instruction were executed.how do i maintain the program that were already executed???

' {$STAMP BS2}
' {$PBASIC 2.5}

'===============return to normal position==================
temp VAR Word
DO

FOR temp=650 TO 750
PULSOUT 15,temp
PAUSE 1 '==============
NEXT '====='= = ======
'= =
FOR temp=550 TO 750 '= =
PULSOUT 14,temp '====='= ======
PAUSE 1 '= =
NEXT '= =
'= =
FOR temp=550 TO 750 '====='= ======
PULSOUT 13,temp '==============
PAUSE 1
NEXT

'=========================
PAUSE 3000

FOR temp=750 TO 650
PULSOUT 15,temp
PAUSE 1 '==============
NEXT ''= '= = ==
'= '= = =
FOR temp=750 TO 1000 '='= = =
PULSOUT 15,650 '====='= ======
PAUSE 1 '= =
PULSOUT 14,temp '= '= =
PAUSE 1 '= '= =
NEXT '='= ==
'============== =
FOR temp=750 TO 1000 '=
PULSOUT 15, 650
PAUSE 1
PULSOUT 13,temp
PAUSE 1
NEXT

'===========================
PAUSE 10

FOR temp=850 TO 750
PULSOUT 15,temp '==============
PAUSE 1 '====='= = ======
NEXT '= =
'= =
FOR temp=1000 TO 750 '====='= ======
PULSOUT 14,temp '= =
PAUSE 1 '= =
NEXT '= =
'====='= ======
FOR temp=1000 TO 750 '==============
PULSOUT 13,temp
PAUSE 1
NEXT
'============================
PAUSE 10

FOR temp=750 TO 850
PULSOUT 15,temp '==============
PAUSE 1 '='= = = =
NEXT '= '= = =
'= '= = =
FOR temp=750 TO 550 '====='= ======
PULSOUT 15,850 '= =
PULSOUT 14,temp '='= = =
PAUSE 1 '= '= = =
NEXT '= '= ==
'==============
FOR temp=750 TO 550
PULSOUT 15,850
PULSOUT 13,temp
PAUSE 1
NEXT

PAUSE 10
LOOP
'==================================

if somebody can help i really appreciate it...

[img]http://img252.imageshack.us/img252/3315/1001860le4.jpg<img src=[/img]

SRLM

You should consolidate your code. Put each of the Pulsouts one after another, in a loop, with a 20 ms pulse between iterations. The way that you have it, there is a 3000 ms, then 3 ten ms pauses. To maintain a position, you have to refresh the servo every 20 ms with the desired position, hence the loops. Take a look at the LOOKUP command to relate various values together.

Ownonono

temp VAR Word
DO

FOR temp=650 TO 750
PULSOUT 15,temp
PAUSE 1
NEXT

FOR temp=550 TO 750
PULSOUT 14,temp
PAUSE 1
NEXT

FOR temp=550 TO 750
PULSOUT 13,temp
PAUSE 1
NEXT


PAUSE 3000

FOR temp=750 TO 650
PULSOUT 15,temp
NEXT

FOR temp=750 TO 1000
PULSOUT 15,650 'middle leg
PULSOUT 14,temp 'left leg

NEXT

did u mean like this

SRLM

No. A servo must have a pause of approx. 20 ms between pulses. In all your loops, you have about 1 ms pause (due to code execution time). You want something like this:


For temp = 650 to 750

PULSOUT 13, temp
PULSOUT 14, 750
PULSOUT 15, 750
PAUSE 17 '17 because you have three ~1 ms pulses and execution times.

NEXT

This will properly refresh the servos, and hold the unmoving servos in place. This would constitute one "step", or movement. It looks like your walking sequence has about 6 sequences, so you'll need to repeat this six times (or however many).

Ownonono

temp VAR Word
DO

=============SERVO RETURN TO NORMAL POSITION==============
FOR temp=650 TO 750
PULSOUT 15,temp
PAUSE 1
NEXT

FOR temp=550 TO 750
PULSOUT 14,temp
PAUSE 1
NEXT

FOR temp=550 TO 750
PULSOUT 13,temp
PAUSE 1
NEXT

PAUSE 3000 'HOLD FOR 3 SEC THEN MOVE
======================================

For temp = 750 to 1000

PULSOUT 13, 850 'MIDDLE SERVO LIFT BODY
PULSOUT 14, TEMP 'LEFT LEG MOVES FORWARD
PULSOUT 15, TEMP 'RIGHT LEG MOVES BACKWARD
PAUSE 17 'WILL IT BE LIKE THIS???

NEXT

LOOP


DO THE SERVO ON P13 HOLD ITS POSITION BECAUSE OF THE WEIGHT AND THE OTHER INSTRUCTION ARE RUNNING???

SRLM

I assuming in my answer that your question refers to the line:

PULSOUT 13, 850 'MIDDLE SERVO LIFT BODY

near the end. The servo holds it's position because you are refreshing it ~20ms with a constant value. The weight has nothing to do with it, and neither do the other instructions. That's one of the double edged swords about servos: you have enough time to do other stuff between refreshes, but you can't forget about them.


You first three loops are still wrong. You have a ~2 ms refresh rate (PAUSE 1 + execution time). You need 20 ms. Also, you might as well combine the first three loops. It will get the servos to the normal position faster (they all move together, rather than wait for one to move, then the next). It's a good habit to do all your servo refresh work at the same time. (AKA, always group the PULSOUTs together unless you have a really good reason.)

Ownonono

=============SERVO RETURN TO NORMAL POSITION==============

FOR temp=550 TO 750
PULSOUT 14,temp
PULSOUT 13,temp
PULSOUT 15,temp
PAUSE 20
NEXT

PAUSE 3000 'HOLD FOR 3 SEC THEN MOVE
======================================

For temp = 750 to 1000

PULSOUT 13, 850 'MIDDLE SERVO LIFT BODY
PULSOUT 14, TEMP 'LEFT LEG MOVES FORWARD
PULSOUT 15, TEMP 'RIGHT LEG MOVES BACKWARD
PAUSE 20

NEXT

LOOP

it is like this??

when i try this command,the middle servo lift it leg but then return back when left leg moving, when i check the volts, at first it receive 6 volt, then when left leg moves the middle servo show 0 volts making it goes to original position,so that why i assume the weight of robot making it return after lift it.

and i see that my servo moves very slow.my servo type is Cytron C40S (180 degree type)

Ownonono

Bruce Bates

Ownnonono -

My guess is that either your battery pack needs a charge, or it isn't large enough for your hexapod.

Regards,

Bruce Bates

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When all else fails, try inserting a new battery.

Ownonono

no..i dont use the battery i use a power supply from the socket...it never runs out...

allanlane5

If the voltage drops to zero, then the wall-wart power-supply may be undersized. What is its voltage and amperage rating?

Ownonono

6v 1.1 A

the sequence like this..

midle servo move = 6v left leg 0v
left leg move=6v middle 0v
middle move again=6v left leg 0v

allanlane5

Each servo can take up to 1 amp, when moving, depending on resistance. So yes, activating two servo's (or three, as you're doing) at the same time can be a problem.

It sounds more likely that the legs have too much resistance in their moving, and this is "browning out" the supply.

From looking at earlier posts, it does seem that you're stopping "refresh" of one of your servo's, which means it won't "hold position".

It's better to have three variables: Servo1Pos, Servo2Pos, Servo3Pos

Then:

RefreshServo:
· PULSOUT Servo1Pin, Servo1Pos
· PULSOUT Servo2Pin, Servo2Pos
· PULSOUT Servo3Pin, Servo3Pos
· RETURN

On 'return', you have 20 milliseconds before you MUST call RefreshServo again.

Post Edited (allanlane5) : 10/30/2008 3:00:18 PM GMT

Ownonono

looking at your comment...i try to moves servo only..without any attachment..but the servo also moves slow
i do realize that if there is a resistance in servo movement it will draw more current.

i want the middle servo to lift the body and hold its current position while the other leg moving

SRLM

Are you sure that you servos are okay? Have you always fed them ~5-6 volts? Also, I don't know what a refresh rate of 2ms does, and it might have hurt you servos. I suggest that you either a) put as little weight as possible on them or b) take them out and test to see if they acutally do work. They should move quickly to position (if you tell it some thing like 850) and then hold their quietly.

Chris Savage

Overdriving servos (refreshing them faster than ~15 mS) doesn’t really hurt them so much as it makes them jittery depending on the servo.

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Chris Savage
Parallax Engineering

SRLM

Ah, thanks Chris. I've never tried to overdrive, and have not been willing to risk a servo to see what happens.

Ownonono

allanlane5 did u mean like this

middleright CON 850
middleleft CON 650
leftfwd CON 1000
leftback CON 550
rightfwd CON 550
rightback CON 1000

do

GOTO RefreshServo
pause 20

PULSOUT 13, rightfwd
PULSOUT 14, leftfwd
PULSOUT 15, middleleft

GOTO Refresh Servo
pause 20

loop



RefreshServo:
PULSOUT 13, rightback
PULSOUT 14, leftback
PULSOUT 15, middleright
RETURN

SRLM

You defined constants. Allanlane said variables. The way that he has it set up (as per good programming practice: put things in methods) is to call the RefreshServo method every time that you need to refresh the servo. Aka, in your code above, you want to replace the first three pulseouts with a call to RefreshServo. You "tell" the servos where you want them to be by changing the ServoPos variable to the pulseout width (750, 800, etc.) If you want to use the constants, you'll use a line like this:


Servo1Pos = leftfwd
GOSUB RefreshServos
Pause 20


Also, note that you want to call the RefreshServo method with GOSUB, not GOTO. Take a look in the BS manual to see why.

Ownonono

actually i want to wrote GOSUB..but just before i was programming the intel 8051..that why i accidently wrote GOTO...hohohohoh

how to do the variables??

SRLM

You have three servos, so you have three servo positions:

servo1 VAR Word
servo2 VAR Word
servo3 VAR Word


In your refresh servos method, simply use these variables in place of a constant number or CON. Since the variables are global, there shouldn't be any visibility problems. When you want to change where a servo is, just change (for example) servo1 = 850.

Ownonono

the in programming..should i wrote like this

servo1 VAR Word 'here is where i declare
servo2 VAR Word
servo3 VAR Word

do

pulsout servo1,750 'all the in normal position
pulsout servo2,750
pulsout servo3,750

pause 20

pulsout servo1,850 'lift left body while left leg forward,right leg backward
pulsout servo2,1000
pulsout servo3,1000

pause 20

pulsout servo1,650 'lift right body while left leg backward,right leg forward
pulsout servo2,550
pulsout servo2,550

pause 20

loop

it is like this..for simple walking only???

SRLM

That should almost work. Note that it will probably take longer than 20 ms to move a leg. So, you need to put each of the blocks into a loop. I'd guess a second would work, but you'll have to play with it. And are you just giving up on the subroutine? Anyway, try reading Robotics with the Boe-Bot, in specific the chapters on servo control. Those servos are continuous, so there is some theoretical differences, but the prinicples are the same and you can translate it to your code.

Ownonono

ok ...i try that..

this is just sample of code...later i put it into subroutine...if i put RETURN command, do i still need the PAUSE 20??

SRLM

Whenever you pulsout a servo, you need to wait ~20 ms before the next pulsout. You can use a PAUSE 20, or other code that takes 20 ms, or any combination of the two. A subroutine (with GOSUB and RETURN) is just some code organization that we programmers do to save size and make it easier to read and change.

Ownonono

ok ...now i get it..since u said it between pulsout...which one better??

PULSOUT SERVO1,750
PAUSE 20
PULSOUT SERVO2,750
PAUSE 20

or

PULSOUT SERVO1,750
PULSOUT SERVO2,750
PAUSE 20