Pinv velocity solver sigma output #359
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added 3 commits
September 28, 2021 14:36
Add functions to set the input parameters (maxiter, eps) which can be done from the controller. Also add functions to retrieve the singular values and current value of eps.
The singular value decomposition in SVD_HH does not sort the singular values in descending order. So a sort function was added to do this based on the same code used in SVD_eigen_HH. The sorted version of S called Smaxtomin is then used to find the minimum of the six largest singular values and is also what is returned by the get Sigma function used to calculate the manipulability.
This adds a solver test for the new functions in the pseudoinverse velocity solver which include the set/get functions and the singular value sorter and retrieval functions.
MatthijsBurgh
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Feb 27, 2023
| // copied from svd_eigen_HH.cpp | ||
| Smaxtomin = S; | ||
| SortJntArrayMaxToMin(Smaxtomin); | ||
| // Minimum of six largest singular values of J is S(5) if number of joints >=6 and 0 for <6 |
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Why is this behaviour comming from? As there should be the same number of singular values as the number of joints, correct?
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Yes, the number of singular values is the same as the number of joints. However, any singular values beyond the sixth which is S(5) will be zero (assuming SVs are ordered from high to low). We are interested in whether the sixth singular value is zero because that is when the determinant of J*J^T is zero and a Cartesian degree of freedom is lost. Then the condition corresponding to fabs(S(i))<eps (line 140) must be applied in order to compute the pseudoinverse.
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The main purpose of this request is to add member functions to retrieve the singular values from the pseudoinverse velocity solver. These can be used to generate manipulability feedback to the user similar to that already present in the wdls velocity solver.
A function was also added to sort the singular values in descending order in order to retrieve the minimum singular value. Functions were also added for setting/getting the number of iterations and singularity threshold.