Verheffen van Gangrevalidatie: Ontwerp van een Koppelgestuurd Heupflexie- en Extensie-Exoskelet

Cerebral palsy (CP) is a debilitating neurological condition affecting motor function and impacting the lives of 1.5 to 3 per 1000 children. While CP manifests in varying degrees of motor impairment, many affected children are ambulatory but experience gait difficulties. Robotic devices such as gait trainers and lower-limb exoskeletons have shown clinical benefits in adult and pediatric patients with neurological disorders or injuries. Current state-of-the-art solutions have shown promise in improving spatiotemporal gait parameters in CP patients. However, traditional position-controlled exoskeletons have limitations, particularly in addressing specific issues of CP patients, such as muscle contractures and spasticity. In contrast, compliant exoskeletons with torque-controlled actuators could offer adaptive assistance to users, potentially improving gait patterns and overall mobility. Moreover, recent studies with torque-controlled hip exoskeletons have demonstrated benefits in both unimpaired as well as CP participants, such as reduced metabolic cost, reduced muscle activity, and a more upright gait, by providing properly timed and scaled assistive torques. In this work, a torque-controlled hip flexion/extension exoskeleton is designed to address specific gait abnormalities observed in CP patients, such as excessive hip flexion and hip extension deficits. The primary hypothesis is that providing extension torque during the stance phase of gait can ameliorate these abnormalities, particularly in crouch and apparent equinus gait patterns. This could lead to increased endurance, lasting benefits, and an improved quality of life. This dissertation consists of the following chapters. Chapter 1 expounds on the state-of-the-art in exoskeleton therapy for CP and outlines the research goals. In Chapter 2, a numerical approach for optimizing actuator sizing is presented and implemented to meet estimated performance requirements without excessively oversized components. This comprehensive actuator sizing method based on apparent inertia, load torque, velocity, and acceleration at each time instant in a periodic load cycle was applied to gait data. Additionally, an appropriate spring stiffness for a Series Elastic Actuator (SEA) was determined, considering factors such as bandwidth, torque sensing resolution, and the effect of adding compliance on motor torque and power. In Chapter 3, the hip exoskeleton design, control, and performance assessment are presented. The exoskeleton's system architecture, actuators, control system, and hardware components are described in detail and analyzed. The torque control of the actuator was extensively benchmarked, and performance metrics include step and frequency response metrics, tracking error, controller stability, and output impedance. Next, the mechanical design of the device is covered, comprising individualized physical human-robot interfaces and an abduction/adduction mechanism. Finally, a trial with an unimpaired participant was conducted to assess the device's performance. The device demonstrated good tracking performance, a torque delivery capability of approximately 35 Nm during the stance phase, and the potential for improving crouch gait. This finding was supported by the participant who reported difficulty maintaining a simulated crouch gait, noting a lifting sensation. In Chapter 4, the valorization aspects of the research outcomes are discussed. The chapter starts with a case study on the successful commercialization of the Hibbot walker, a walking aid for children with neurological disorders. The technological outcome of the PhD is summarized, Technology Readiness Level (TRL) is introduced, and suggestions for follow-up research to further develop this exoskeleton technology are proposed. The chapter presents potential future perspectives, including licensing the technology to industrial partners and addressing the legal and human factors related to exoskeleton technology. Potential commercial strategies for the hip exoskeleton are discussed, with a focus on selling products and services to healthcare providers. Chapter 5 recapitulates the main outcomes and findings of this PhD, discusses potential solutions for the design shortcomings, and offers suggestions for future work. This research presents a promising direction for improving the mobility and gait patterns of CP patients with impaired gait by using a torque-controlled hip exoskeleton. The findings offer valuable insights into actuator design, control strategies, and personalized design. Future work should involve patient trials, taking additional measurements such as kinematics, kinetics, and electromyography, to establish potential clinical benefits of these innovative exoskeletons.