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A possible typo in a doc formula of chainjnttojacdotsolver #367

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torydebra opened this issue Oct 27, 2021 · 2 comments
Open

A possible typo in a doc formula of chainjnttojacdotsolver #367

torydebra opened this issue Oct 27, 2021 · 2 comments

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@torydebra
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Hi, I was just wondering about some documentation in the chainjnttojacdotsolver

/**
* @brief Computes \f$ \frac{\partial J^{i,ee}}{\partial q^{j}}.\dot{q}^{j} \f$
*
* @param bs_J_bs The Jacobian expressed in the base frame with the end effector as the reference point
* @param joint_idx The indice of the current joint (j in the formula)
* @param column_idx The indice of the current column (i in the formula)
* @param representation The representation (Hybrid,Body-fixed,Inertial) in which you want to get dJ/dqj .qdotj
* @return Twist The twist representing dJi/dqj .qdotj
*/
const Twist& getPartialDerivative(const Jacobian& J,
const unsigned int& joint_idx,
const unsigned int& column_idx,
const int& representation);

I see that the formula written is $ \frac{\partial J^{i,ee}}{\partial q^{j}}.\dot{q}^{j} $, but I am not sure that the final $\dot{q}^{j}$ should be there.
Indeed in :

// Column J is the sum of all partial derivatives ref (41)
if(!locked_joints_[j])
jac_dot_k_ += getPartialDerivative(jac_,j,k,representation_) * q_in.qdot(j);

The result of getPartialDerivative is multiplied by qdot(j)

I am using these formulas/codes, so I would just like to be sure about what it is happening inside :D

Thanks!

@MatthijsBurgh
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I don't have the formulas ready to me. @meyerj @smits could you take this one?

@traversaro
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I guess also @ahoarau may know something as the original author of the class.

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