Integrated framework for hip joint simulator design and validation under realistic loading conditions

Accurately replicating physiological hip joint loading is essential for the reliable evaluation and optimization of total hip replacement implants. This thesis presents a comprehensive methodology integrating finite element modeling, topology optimization, and fatigue sensitivity analysis with experimental validation using a custom-built, ISO 14242-compliant hip joint simulator. The mechanical system features zero-backlash Harmonic Drive® and planetary gear mechanisms, a high-precision six-degree-of-freedom load sensing platform, and adaptive control strategies that precisely reproduce complex multi-axis motion and force profiles. Beyond conventional ISO-based testing, this work incorporates measured in vivo daily-life activity data from Rydell, Paul, and Duff-Barclay alongside the ISO 14242 standard, enabling accurate simulation of gait cycles and other functional tasks. This integration highlights discrepancies in force magnitudes and loading patterns between standardized and physiological conditions. Monte Carlo simulations with stochastic gait load vectors were conducted to evaluate the simulator's structural response under rare high-angle or high-magnitude loading scenarios not captured by existing standards. These analyses informed subtle reinforcements in the force-application mechanism and guided parametric studies assessing the influence of key design variables on stiffness, actuator demand, and service life. Results show that the optimized arm structures achieved a significant weight reduction of 55% without compromising structural integrity or fatigue resistance. The hybrid control architecture, leveraging high-resolution feedback and zero-backlash actuation, ensures high-fidelity reproduction of gait cycles under both deterministic and random load conditions. Validation experiments confirmed the system's ability to maintain accurate force tracking, minimize actuator energy consumption, and sustain long-term wear and fatigue testing reliability. The developed platform satisfies ISO 14242 compliance and enables extended, physiologically realistic testing scenarios, providing a robust foundation for future studies in implant wear mechanisms, lubrication dynamics, and predictive data-driven modeling for next-generation prosthetic designs.