Universal Robots Forum

Changes in release 5.9.1 Blend algorithm for MoveL


We are experiencing a strange and unpredictable behaviour of linear movements with blend when using new firmware versions 5.9.1 or higher. When using blend between waypoints with large orientation change (but NOT small translation as described in the release notes) the robot seems to stop completely at the waypoint instead of proceeding with the specified blend radius. At this point the tool orientation is somewhere between the start and end position. The new behaviour is significantly different from what we have seen in older versions.
So far we have not found any specific circumstances that cause this to happen, but apparently there is some difference between 5.9.1 and 5.9.4 versions again. The only safe solution to use no blend in our application.

If possible, we would like to understand the changes in more detail. It might be related to the Release Notes but the description does not mention any changes in moveL with large orientation AND large translation or define what is considered large or small.

Fixed blend algorithm for MoveL movements with large orientation change and very small translation.
Fixed issue where blending during MoveL could result in aborted program execution or the robot drifting away from the expected trajectory. The issue was related to the combination of orientation blend paths and positional blend paths. In scenarios where the required joint movements of the MoveL blend are dominated by a tool orientation change, i.e. especially relevant for zero or small tool position changes (lower than the blend radius), this issue would occur.

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