Development of strategies to reduce energy expenditure for lower-limb active orthoses
- Autores: Daniel Sanz Merodio
- Directores de la Tesis: Elena García Armada (dir. tes.)
- Lectura: En la Universidad Politécnica de Madrid ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Ernesto Gambao Galán (presid.), Alberto Brunete González (secret.), María Dolores Blanco Rojas (voc.), Nicolás Manuel García Aracil (voc.), Antonio Giménez Fernández (voc.)
- Programa de doctorado: Programa de Doctorado en Automática y Robótica por la Universidad Politécnica de Madrid
- Materias:
- Enlaces
- Tesis en acceso abierto en: Archivo Digital UPM
- Resumen
Lower-limb exoskeletons and powered orthoses are non-invasive devices that assist patients with locomotive disorders to achieve correct limb movements.
The intended use as an assistive device for daily life activities still encounters barriers to practical implementation.
Current batteries cannot meet the long-term power requirements for these devices, which need to operate for long periods. This issue has become a major challenge in the development of these portable robots.
Conversely, legged locomotion in animals and humans is efficient. This thesis explores the methods to reduce energy consumption in the motion control of gait exoskeletons and especially its applicability and feasibility.
From a thorough analysis of the human gait from the energetic point of view and based on the state of development of robotics, a hybrid strategy is proposed to reduce energy consumption in the gait cycle.
Three major research areas can be distinguished in energy-efficient biped walking robots: 1. The first research area focuses on developing optimal gait trajectories for active walking robots. These trajectories are obtained with optimization procedures to minimize an objective function.
2. The second research area focuses on exploiting the passive-dynamic of the robot legs. In the first place, the research is focused on non-active mechanisms that descend ramps taking advantage of the energy of gravity and the elastic energy of the impact. Subsequently, by applying these concepts, it is possible to make robots that walk on flat ground providing only the energy, previously contributed by gravity, to take advantage of the elastic energy of the impact.
3. In the third area, the leg dynamics is modified by including passive or active elastic mechanisms in the joints to reduce energy losses caused by the impact with the ground and to store and release energy for an improved energy-efficiency.
In this thesis, a hybrid approach is proposed, because several strategies to reduce consumption are going to be applied, taking advantage of the benefits of each area. The trajectory in pediatric active orthoses is calculated according to the physiological needs of the patient. The gait control approach will explode the natural dynamics of the leg; actively modifying joints dynamics through the use of Variable Stiffness Actuators (VSA).
By the application strategy of stiffness variation, control strategies based on passive dynamics can be implemented in the same joint, while the necessary torque can be provided for a rigid control in position in phases of higher torque demand, allowing subactuation in gait phases where inherent inertia is enough to take advantage of it and also providing the high torque necessary for the orthosis to perform more versatile and non-cyclic movements, such as sitting and standing maneuvers. In turn, by establishing the adequate stiffness to the joint, consumption is reduced in changes of direction of the joint and energy can be stored and released in certain gait phases.
The locomotion control strategies proposed have been validated through their implementation in the ATLAS active orthotic prototype. In this experiment, the importance of the variation of stiffness in relation to an efficient gait is reflected. This hybrid strategy achieves a reduction in energy consumption of 40%, while maintaining the robustness and reliability of the active orthosis with stiff actuators.
The results of the research work have led to 8 publications in indexed scientific journals and 14 articles in international congresses, several of which have been prizes for their scientific and technical excellence. The doctoral thesis has had a relevant impact in the area of rehabilitation robotics since its results are being used in real environments, since pediatric gait exoskeletons, transferred to the technology-based company, are being used in two hospitals in the therapy of neuromuscular diseases in childhood.
