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How Robot Arm react to PlayStation 2 Wireless Control

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Rookie ( offline )
Posts: 25
Posted: 2012-01-28 15:07 
Hi Jim and Kurte,

Just comeback from a trip. Thank you for your reply. The crazy beep is because I connect PS2 control in wrong way. Sorry about that. Things improve a little bit. We think the problem is calibration. Everything reacts to the control and moving. But couple things still not under control. Is there a way to calibrate the arm? I saw you have a program that can calibrate the robot. Does that also works for BB II Atom28 pro without SSC32 board?

Thanks


Rookie ( offline )
Posts: 25
Posted: 2012-01-30 09:31 
Hi,

We are trying to figure out what does is InitGripperAngle1 con -550 mean? -55 degree from where to where? CCW or CW, etc.


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Guru ( offline )
Posts: 4857
Posted: 2012-01-30 09:33 
From watching it in action, the 0 point is with the wrist straight out with the arm, and the -550 makes the gripper point down toward the ground...

Kurt


Rookie ( offline )
Posts: 25
Posted: 2012-01-31 01:06 
BaseLength con 69 ;Length of the Base [mm]

Does the length of the base mean the radius of the base?

Thanks


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Guru ( offline )
Posts: 9258
Posted: 2012-01-31 10:30 
I believe that dim is referring to the height of the base at the shoulder axis point.

_________________
Jim Frye, the Robot Guy
http://www.lynxmotion.com
I've always tried to do my best...


Rookie ( offline )
Posts: 25
Posted: 2012-01-31 17:06 
Rookie ( offline )
Posts: 25
Posted: 2012-02-05 18:33 
Dear Lynx,

Has some improvements. But, one thing that doesn't seem right. We had burn the gripper servo twice. Any advice?

Thanks


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Posts: 4857
Posted: 2012-02-05 19:21 
May be that the limits need to be refined. That is the values of Gripper_MIN, Gripper_MAX. Do you have EnableFSR defined on your arm (and have a FSR?). When I have issues like this, I would probably modify the code where L1/L2 are used and add something like: serout s_out, i9600, [sdec TargetGripper1, 13]
To each of them and then try moving the gripper in each direction and see if you get to the limits...

Kurt


Rookie ( offline )
Posts: 25
Posted: 2012-02-07 00:02 
May be that the limits need to be refined. That is the values of Gripper_MIN, Gripper_MAX. Do you have EnableFSR defined on your arm (and have a FSR?). When I have issues like this, I would probably modify the code where L1/L2 are used and add something like: serout s_out, i9600, [sdec TargetGripper1, 13]
To each of them and then try moving the gripper in each direction and see if you get to the limits...

I tried the gripper with a servo tester. It only took 90 degree to fully open and close. In the code, it is Gripper_MIN con -720 and Gripper_MAX con 680. Should I set to Gripper_MIN con -450 and Gripper_MAX con 450?


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Guru ( offline )
Posts: 4857
Posted: 2012-02-07 09:43 
Maybe. Try it see if it works.... You said it only took 90 degrees, but was it such that + and - 45 was the end points, or could it have been +48 and -42.... The fun thing is, it is not hard to experiment and see what works for you here.

Good Luck
Kurt


Rookie ( offline )
Posts: 25
Posted: 2012-02-07 16:43 
Hi,

I need the robot arm to extend fully outward, but the elbow seems to only be able to rotate the arm upwards 45 degrees from its neutral position instead of the full 90 that it is supposedly capable. I edited the mechanical limit of the elbow servo in the program from 450 to 900 to try to change the servo rotation to 90 degrees, but that had no effect. Is there something else I need to do to make the arm's full extension possible? Or is there something else that needs to be changed in the program to do this?

Here is the program for the mechanical limits of the arm. You can see that I already changed the elbow maximum to 900 (originally the elbow minimum was -710 and the maximum was 450):

Base_MIN con -900 ;Mechanical limits of the Base
Base_MAX con 900

Shoulder_MIN con -780 ;Mechanical limits of the Shoulder
Shoulder_MAX con 900

Elbow_MIN con -710 ;Mechanical limits of the Elbow
Elbow_MAX con 900

Wrist_MIN con -900 ;Mechanical limits of the Wrist
Wrist_MAX con 900

Gripper_MIN con -720 ;Mechanical limits of the Gripper
Gripper_MAX con 680

WristRotate_MIN con -760 ;Mechanical limits of the WristRotate
WristRotate_MAX con 830


Rookie ( offline )
Posts: 25
Posted: 2012-02-08 01:33 
Hi,

I still need help on my previous problem above, but i just discovered another. Although the normal controls for the gripper are supposed to be L1 to close the gripper and L2 to open the gripper, the L1 button on our robot arm actually opens the gripper instead of closing it. Also, the gripper automatically closes when the L1 button is released. Sometimes, after the release of the L1 button the gripper still does not fully close and then the L2 button must be pressed to close the gripper fully. Can you help explain the inconsistency between the listed controls and the issues we are experiencing? We would like to have the gripper open when the L1 button is pressed and close when the L2 button is pressed, when not pressing any button, for it to stay in a half open neutral position. Is it possible? (We use Aalternate Gripper with HS-225MG servo)


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Guru ( offline )
Posts: 9258
Posted: 2012-02-08 10:36 
If the gripper is moving when no button are pressed I suspect there is an issue with the controller.

Have you tried the code that was posted in the Help for 2012 Science Olympiad Competition? viewtopic.php?f=6&t=7923 It might make more sense for you to use that code as it has had many problems fixed.

_________________
Jim Frye, the Robot Guy
http://www.lynxmotion.com
I've always tried to do my best...


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Guru ( offline )
Posts: 4857
Posted: 2012-02-08 11:07 
In an earlier version of the the code that I updated there was an issue with the gripper with one of the buttons. That was it was setting the wrong variable and as soon as you released the button if I remember correctly it returned back to near the center location... Fixed in the thread that Robot Dude mentioned... I think the normal code will stay when you release the button stays where it is when you released it. You can change that to move back to the center pretty easily. For example the L1 code might look something like:
Code:
   IF (DualShock(2).bit2 = 0) AND (GripperPressure>GripperHoldPressure) THEN   ;L1 Button test
       TargetGripper1 = (TargetGripper1-abGOModifier(ArmSpeedSelect)) min Gripper_MIN ;Gripper Close
   ENDIF
   IF DualShock(2).bit2 AND (LastButton(1).bit2 = 0) THEN   ;L1 Button release test
       TargetGripper1 = 0   ; put to center position...
   ENDIF
   

L2 would be similar...

As for moving the elbow more than 45 degrees. I believe that is all controlled by the math, in the function: ArmIK [IKWristPosX, IKWristPosY, IKGripperAngle1].

My guess is that the math is setup such that if it thought it needed to go farther that the shoulder would move to get to the desired location... When the elbow does not extend to where you want it, is the shoulder at it's min or max position? If this is the case, my guess is to get what you want, the math would need to be changed, to detect that the shoulder has been constrained and then recalculate the elbow from there. But I am guessing as I did not write this code...

Kurt


Rookie ( offline )
Posts: 25
Posted: 2012-02-08 12:54 
Kurt,

Thank you for your help. In referring to your comment, "the math would need to be changed, to detect that the shoulder has been constrained and then recalculate the elbow from there". Can you point out which part of the code I need to look at? I will see if I can figure out myself.

Thanks


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