ISSUE_NOTE.txt

Feb 2020:  Users reporting UR5 broken on master. 

>> 3-Feb:   solution of UR5 working. just some extra variables in the output: eg th_23 
    which have solutionmethod = "*none* and no solution equations.
    need to prune nodes by nodes.solutionmethod
    21-Dec  Update:  prune by zero length solution method instead!
    
    ----------------------------------------

     New branch RepairUR5Regression which is newest commit which works with ARM & UR5.
     
     ** UR5 doesn't solve trival eqns like   th_4 = th_234-th2-th3
        -- make sure SOA definition equations are included during solver scanning of eqn lists. 
     
---------------------------------
 
May 2019:    "Arm_3"
  *  This arm now works ... mostly.   The Latex report has a couple of gaps but still produces a workable solution.
  *  Still 2 open issues with ArmRobo and Lori.

21-Feb-19:    Following are open issues:
  *   simple planar 3-link "Arm_3" fails to properly manage 3-way sum of angles
  *   python -m ikbtleaves.sum_transform   FAILS
  *   find_xy function (see below) is commented out in ik_classes()(@*)!_#)%%?)
  *   SofAngles fails some previous test cases in the comprehensive test included in updateL.py

-----------------------------
August 2018 (just prior to releasing the UR5 Fix)
--
Regarding sum of angles changes to handle 3 parallel axis case:

1) there are two very similar codes which are dupes and should be unified:
    a)  find_xy in ikbtbasics/ik_classes.py   ***  official version 
    b)  find_xy in sum_transform.py           ***  DELETED

2) there are two methods that use find_xy to substitue sum-of-angles.  One is in sum_transform.py
    and another is a method member of the Robot class (!)   the later is used in updateL. 

We need to eliminate these redundancies so that we can fix the 3-parallel axis case.   Strategy:

1) elmininate duplcated codes    **Check: 3-Aug-18
2) find a new method other than the set lookup table (or maybe a lookup table with a two list input):

   {[th1,th2] : [ th12, th123],\\
    [th2,th3] : [th23, th 123, th234] }  etc.

BH  30-Jul


New alg:

1) convert two args to strings (i.e. string having the variable NAME)  # does this require new class members?

       th1 --> 'th1',   th23 --> 'th23'    etc

2) separate indices (ints) from strings, 

       th1 --> '1',  th23 --> '23'

3) concatenate and sort. 

   ['23', '1'] --> '123

4) search existing unknowns for match to new variable 

   'th123' --->   < already a defined unknown > or < create new unknown th123>
   
   
Second approach ***

1) each unknown has self.n = index of joint.    if index > 10, it means a sum of angle:
       i.e. if self.n == 234,  self is th_234.
       
2) for two unknowns, a,b:

   if sum is a new unknown where sum = th_a + th_b,
   
    sum.n = int(str(a.n)+str(b.n))