COMPUTE_DFNLDXD
function dfnl = compute_dfnldxd(obj,x,xd)
This function computes the Jacobian of nonlinear internal force f with respect to the velocities xd in a second-order mechanical system. Currently, this function does not support velocity dependent nonlinearities.
assert(obj.order == 2, ' dfnldxd can only be computed for second-order systems') dfnl = sparse(obj.n,obj.n); % for j = 1:length(obj.fnl) % dfnl = dfnl + expand_tensor_derivative(obj.fnl(j),x); % end error('Method not implemented yet')
end