Constant high rates of dislocation-related complications of total hip replacements (THRs) show that contributing factors like implant position and design, soft tissue condition and dynamics of physiological motions have not yet been fully understood. As in vivo measurements of excessive motions are not possible due to ethical objections, a comprehensive approach is proposed which is capable of testing THR stability under dynamic, reproducible and physiological conditions. The approach is based on a hardware-in-the-loop (HiL) simulation where a robotic physical setup interacts with a computational musculoskeletal model based on inverse dynamics. A major objective of this work was the validation of the HiL test system against in vivo data derived from patients with instrumented THRs. Moreover, the impact of certain test conditions, such as joint lubrication, implant position, load level in terms of body mass and removal of muscle structures, was evaluated within several HiL simulations. The outcomes for a normal sitting down and standing up maneuver revealed good agreement in trend and magnitude compared with in vivo measured hip joint forces. For a deep maneuver with femoral adduction, lubrication was shown to cause less friction torques than under dry conditions. Similarly, it could be demonstrated that less cup anteversion and inclination lead to earlier impingement in flexion motion including pelvic tilt for selected combinations of cup and stem positions. Reducing body mass did not influence impingement-free range of motion and dislocation behavior; however, higher resisting torques were observed under higher loads. Muscle removal emulating a posterior surgical approach indicated alterations in THR loading and the instability process in contrast to a reference case with intact musculature. Based on the presented data, it can be concluded that the HiL test system is able to reproduce comparable joint dynamics as present in THR patients.
Load calculations on wind turbines are an essential part of its development. In the preliminary design phase simplified multibody models are used for the estimation of the interface loads. The interface loads are used within an iterative development loop to design the components of the wind turbine such as gearbox, blades, tower and so on. Due to the early application of load calculations within the development process, the quality of the simulation results has a great influence on the wind turbine design.
In this contribution the simulation results of the multibody codes alaska/Wind, MSC.Adams and SIMPACK are compared with measurements obtained from a prototype of a 2.05 MW wind turbine developed by W2e Wind to Energy. Furthermore, simulation results of the special wind turbine design code Flex5, developed at the Technical University of Denmark Copenhagen, are taken into account. A statistical and dynamical evaluation of the simulation and measurement results has been done. Due to the use of the same controller procedures as used on the physical wind turbine, the wind turbine models show almost the same behaviour (electrical power, pitch angle, rotor speed) as the wind turbine in the field. Differences occur during the evaluation of the interface loads due to the different kinds of wind turbine modelling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.