Held, AlexanderAlexanderHeldSeifried, RobertRobertSeifried2023-10-092023-10-09202311th ECCOMAS Thematic Conference on Multibody Dynamics (MULTIBODY 2023)978-989-53599-3-6https://hdl.handle.net/11420/43604The paper is on applying the adjoint variable method in the sensitivity analysis of multibody systems, which are formulated in state-space representation using a QR decomposition. The Jacobian of the state equations, which is necessary to develop the adjoint dynamics, is derived. Moreover, an analytical way to determine the derivatives of the QR matrices with respect to the redundant position variables is presented, which avoids costly finite differences or differentiation of the direct QR algorithm. The developed method is tested by a spring torsional pendulum found in previous contributions to the subject. The obtained gradient is more precise compared to numerical differentiation using forward differences. Also, providing the analytical Jacobian of the state equations turns out to be beneficial regarding both the gradient accuracy and computational times.enadjoint sensitivity analysismultibody systemsQR decompositionstate-space respresentationComputer SciencesEngineering and Applied OperationsConference Paperhttps://multibody2023.tecnico.ulisboa.pt/~multibody2023.daemon/prog_MULTIBODY_WEB/MULTIBODY2023_PAPERS/ID_223_548_eccomas2023_full_paper.pdfConference Paper