Continuous Turn Joint 6

Continuous Turn Joint 6

Postby ToddR » Wed May 13, 2009 10:09 am

In order to use the continuous turn option for joint six of a Viper there are a few prerequisites that need to be handled.

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If your six axis-robot was purchased from Adept along with the continuous turn functionality then the below measures will already have been taken by our production team.
If you are having trouble getting joint six to turn past +/- 360 please check the following things.
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1) J6 Continuous Turn license has to be installed.
2) J6 soft limits have to be increased above the +/- rollover value.
*3*) There is a special procedure to make encoder on J6 ignore overflow error which is done only at Adept's production facility, and a continuous turn robot option bit which must be set (done by Adept.)

1) To check whether or not this license is installed:
From Adept ACE: Open the controller object in the Workspace Explorer which is associated with the Viper of interest (by double clicking). Click the "Configure V+". A new Window will open with the title "V+ System Configuration." Select the Licenses Tab and scroll down to check whether or not the "Six-Axis Robot Multi-Turn J6" license box is ticked. If not you can enter your password at this screen and click install. If you don't have a password for this license you can purchase one from Adept.
From Adept Windows PC: LOAD d:\util\config_c . EXECUTE a.config_c on an unused task above zero. Select the option for NVRAM, and on the following screen select "display contrtoller NVRAM." Here you will see a list of installed licenses. If the "Continuous-Turn Joint 6" license is not present exit config_c and from the monitor window enter "INSTALL" followed by a space and then your password. If you do not have a password for this license you can purchase one from Adept.

2) Ensure that the Motion Limits are set above the +/- rollover value:
The default rollover value is 360 and can only be changed by Adept. For your continuous turn operation to run smoothly it is recommended that you then set your Motion Limits to 720 and -720.
From Adept ACE: From the Viper robot object (as shown in the attached screen-shot) click the + next to "Joints" to expand this field, then the + for "[6]". The only option you are allowed here is Motion Limits. The default will be 360 -360. Change this number to 720 -720 by highlighting the existing value and replacing it.
From Adept Windows PC: LOAD d:\util\spec. EXECUTE a.spec on an unused task above zero. Select the option for "edit robot specifications." Then select the option for "edit joint motion specs." The default joint will be joint one. Choose "Change Joint Number" and enter 6. Select "Lower Joint Limit". Enter -720. Select Upper "Joint Limit." Enter 720. Exit spec by entering 0 to exit to a higher level menu until the program closes properly

You may need to restart the controller and the robots amplifier before the changes take place.

*3*) There is a change that needs to be made to the joint six encoder that can only be made at Adept. This change is intended to force the encoder to ignore overflow errors. Unless this change is made, traveling a certain distance in one direction (15 or so turns in some cases) you will generate an error and the robot will not be movable until you unwind it. Depending on the application the robot may work well for quite some time before this error is realized. If the robot was not initially purchased with the intent of being used for continuous turning then it is very possible that this modification has not been made. Please contact Adept if you are unsure.

*3 Contd*) There is a robot option bit which must be set in order to make use of the continuous turn functionality. If you receive an error when attempting to change your Motion Limits above -360 360 (step 2) please make a note of this when contacting Adept for support.

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At this point you should be able to use the DRIVE or SPIN instructions to move joint 6 through the point value at which the joint value rolls over (360). It is important to note that you will not be able to assign locations or precision points which specify roll values or joint values higher than before. This means the MOVE and MOVES commands cannot be used to rotate through this rollover value.

EXAMPLE - To turn joint 6 three times you could use the instruction "DRIVE 6, 1080, 100" which will drive joint 6 1080 degrees at speed 100. MOVE HERE:TRANS(,,,,,1080) will not work, and may return a position out of range error.

It is also important to note that V+ does not keep track of how many turns have taken place, but simply changes the joint value from 360 to zero if you are turning in a positive direction, or 0 to 360 if you are moving in a negative direction. World location values for Roll will cycle between -180 and 180. If necessary you should keep track of how many degrees joint six has been commanded to turn from within your program.
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ToddR
 

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