Hi Yi-Shin,
unfortunately you are correct.
There are some problems in the current version of emc2, that joints (motors)
and axes (carthesian directions) are mixed in a couple of places.
There is ongoing work (on the joints-axes3 branch) to fix this.
But it's a lot of work (in a lot of layers and places), so there is no fixed
timeline when it will be useable.
Regards,
Alex
From: Yi-Shin Li
Sent: Wednesday, November 04, 2009 6:13 PM
To: emc-developers
Subject: [Emc-developers] the trajectory planner might not be suitable forany
machines with non-trivial kinematics
Hello emc-developers,
I was digging into an issue for SCARA Robot controlled by EMC2. That is,
the angular acceleration for the first 2 joints is way too larger than the one
set by its configuration file. After carefully analyzing the dumped trace,
I found it might be caused by misleading trajectory planning results.
I then found an interesting issue for the trajectory planner, i.e. it might not
be suitable for any machines with non-trivial kinematics. Please take a
look for the following code at getStraightAcceleration() on emccanon.cc:
tx = dx? (dx / FROM_EXT_LEN(AXIS_MAX_ACCELERATION[0])): 0.0;
For non-trivial kinematic machines, such as SCARA, the dx is contributed by
several joints other than AXIS_0. However, the above code assume that
it only depends on AXIS_0, which is not true for those machines. Therefore,
the calculated accel/velocity for trajectory planner may be incorrect.
Is my understanding for above statement correct?
Yishin
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