Offsetting all waypoints in all programs on a UR robot

Nicolas_Lauzier

Hi all,

Let's say that I have a minor change on my robot's end effector (for example, I changed the fingertips of my gripper) and I want to apply an offset of 5mm in tool Z. Normally, I would just change the TCP. However, if all waypoints were teached with the "Use Tool Flange" option for the TCP, is there a way that I can offset all these points without having to change the TCP on all the move instructions? Imagine that I have a lot of programs with a lot of points such that any manual operation is not practical.

I'm looking for a script, a tool or a built-in option in Polyscope.

Thanks!

matthewd92

What type of moves are you making?

Nicolas_Lauzier

@matthewd92 , I am looking for a generic solution on this so I'm interested if something works for either moveJ, moveL or both of them.

matthewd92

With moveL you could simply alter the base_var and then it adjusts the moves accordingly.  This does not work for movej though since there is no transformation going on behind the scenes like there is with moveL. You could store as an installation variable the offset pose to use and then in the before start section of the program do the pose_add such as:

base_var = pose_add(base_var,someOffsetPose)

We played around with this some yesterday and it actually does work with the movel

Nicolas_Lauzier

Thanks @matthewd92, I wasn't aware of this variable!

However, this offset will not be applied in the tool frame, am I right?

MarcAntoine_Lacasse

@matthewd92 I try to play with the base_var on polyscope 3.6 but I receive an error about 'base_var not initialized' ?

matthewd92

Sorry @MarcAntoine_Lacasse I had a typo in the code line above. It should use the pose Base in the formula

Base_var = pose_add(Base,someOffsetPose)

@Nicolas_Lauzier I'm not sure if it would or not, my gut says that it wouldnt but if you are using the tool frame of reference then correcting the TCP would correct those motions.  This would be a correction for the motion was taught using the tool flange unless I am not understanding the question correctly.

I wrote a small program the other day to test this and all we did was make an incrementing x offset that we kept applying to the Base_var and then calling the same moveL and the robot would step each time the amount of the x offset that we were applying.  To get it to work with a movej we had to do set a variable equal to the waypoint desired in the before start section and then we were recalculating that point before each time it was used in the offsetting loop using the new Base_var as the frame of reference.  Then we were able to achieve the same result which makes sense as this is being done in script code automatically for the moveL situation. 

MarcAntoine_Lacasse

Hi @matthewd92, I must be missing something, Base_var and Base are not recognized as valid pose variable in my test program. Could you link a program in which those variables are used ?

matthewd92

You need to go to the installation tab, go to features and select variable under Base to get to the Base_var in the assignment tab.

I can never get programs to upload but here is a screen shot of the program

MarcAntoine_Lacasse

Thanks Mat, that's what I was missing !

AZalmanov

Is there a reason why this will not work for other features than the base? I am trying to only offset some waypoints in the program.

matthewd92

It should work for any feature you use with a movel so long as you make the feature a variable and then apply your offsets to that variable. 

AZalmanov

Okay, thank you for clarifying. I did also notice that once you change the movej to movel you can select the feature it is based on. That is why it wasn't working at first.

MarcAntoine_Lacasse

@matthewd92 Is it still working with eSeries ?

MarcAntoine_Lacasse

@matthewd92 Looks like the feature is deprecated 

matthewd92

@MarcAntoine_Lacasse that sucks. That was a very useful feature. 

DevinNorris

@MarcAntoine_Lacasse this is still working however you cant use the base variable feature you'll need to set up a point in the features menu and use this where you would use base variable

Kaleb_Rodes

@DevinNorris use a plane in this instance because it has a coordinate system. Without a coordinate system the robot can arrive at points in any orientation.

matthewd92

Any point has a coordinate system, the plane feature in UR condenses down to a single waypoint. We use waypoints all the time in this manner. We have also continued to use the Base variable by just defining one at the start of the program or you can store it as an installation variable if you want some place you can quickly update it

MarcAntoine_Lacasse

@matthewd92 Do you mean you can still define waypoint relative to Base feature with E-Series and modify de Base feature by just defining the Base_var variable ? If so, can you give a programme example ?

MarcAntoine_Lacasse

@DevinNorris Feature points in UR includes orientation. 

matthewd92

MarcAntoine_Lacasse said:

@matthewd92 Do you mean you can still define waypoint relative to Base feature with E-Series and modify de Base feature by just defining the Base_var variable ? If so, can you give a programme example ?

Let me see if I can find one when I’m back in the office next week. 

matthewd92

MarcAntoine_Lacasse said:

@DevinNorris Feature points in UR includes orientation. 

Trying to understand something here, how are Feature waypoints different in orientation than regular waypoints?  I know you can use features within the built-in Polyscope move functions but we do the same thing all the time with regular waypoints with scripted moves, or we do the math we need to do and then just use Polyscope move functions with a variable waypoint. 

Just trying to understand and what you are getting at regarding the feature points and orientation. 

MarcAntoine_Lacasse

@matthewd92 You are right, Feature point are the same as regular waypoint, both contains position and orientation.

Kaleb_Rodes

@matthewd92 @MarcAntoine_Lacasse I've used point features in the past and occasionally the robot would move to the point/location but not in the correct orientation. For example, say I created a feature point on the top surface of the table.. base and tool z-axis perpendicular to the surface. Now when moving to that point the robot would approach from the bottom side of the table.

matthewd92

Kaleb_Rodes said:

@matthewd92 @MarcAntoine_Lacasse I've used point features in the past and occasionally the robot would move to the point/location but not in the correct orientation. For example, say I created a feature point on the top surface of the table.. base and tool z-axis perpendicular to the surface. Now when moving to that point the robot would approach from the bottom side of the table.

@Kaleb_Rodes I posted a blog post related to this topic as I have seen a lot of folks have this same issue, including myself when I first started doing more advanced stuff with UR programs.  Here is a link to the post, https://blog.hirebotics.com/engineering/universal-robots-programming-feature-point-orientation

Pmkgur10

matthewd92 said:

With moveL you could simply alter the base_var and then it adjusts the moves accordingly.  This does not work for movej though since there is no transformation going on behind the scenes like there is with moveL. You could store as an installation variable the offset pose to use and then in the before start section of the program do the pose_add such as:

base_var = pose_add(base_var,someOffsetPose)

We played around with this some yesterday and it actually does work with the movel

I have one doubt if we use Base_var ,  are we shifting the robot base?

Due to this any impact on robot..

matthewd92

No impact that I am aware of, you are simply changing a feature that points are taught relative too