Digital Theses Archive


Tesi etd-03292022-145205

Type of thesis
Design and clinical testing of new control strategies for an hip exoskeleton for individuals with moderate gait impairments.
Scientific disciplinary sector
Istituto di Biorobotica - BIOROBOTICS
relatore Dott.ssa CREA, SIMONA
  • discrete wavelet transform
  • gait event detection
  • gait phase estimation
  • hip exoskeleton
  • neurorehabilitation
  • transfemoral amputees
  • walking energy expenditure
Exam session start date
Gait impairments due to aging and pathological conditions, such as neurological disorders or <br>lower-limb amputation, are among the major causes of restricted life and loss of personal <br>independence. Early rehabilitation provided along a continuum of care from hospital to <br>community is essential to improve recovery outcomes and the quality of life of individuals with <br>movement disabilities. In this scenario, lower-limb exoskeletons are seen as a cutting-edge<br>technology that can support impaired people in activities of daily living and improve rehabilitation <br>programs in ecological conditions. The robotics research community is fostering the growth of <br>the wearable robotics industry, by promoting technology transfer actions and translating research <br>outcomes into market products. Several full lower-limb exoskeletons have already reached the <br>commercial market internationally. However, for individuals who retain walking capacity, such <br>as the majority of stroke survivors (up to 80%), and lower-limb amputees (up to 60%), individuals <br>at the early stage of multiple sclerosis or with incomplete spinal cord injury, these devices may <br>not be the best approach to promote a more functional walking pattern. Lightweight lower-limb <br>exoskeletons which selectively assist some of the lower-limb joints are emerging as promising <br>alternative robotic tools. Despite recent advances, yet, major challenges in designing effective <br>exoskeletal robots relate to realizing natural and synergistic cooperation between the human user <br>and the robot. To accomplish this objective, several aspects of the system must be considered. On <br>one hand, the physical human-robot interface has to guarantee safe and comfortable fitting of the <br>device; on the other hand, the control interface for the human-robot interaction should ensure <br>intuitive movement intention decoding, as well as adaptive and reliable assistance in different <br>locomotion tasks.<br>Within this framework, the aim of this thesis was the design and clinical testing of innovative <br>control strategies for a hip exoskeleton to assist individuals with mild-to-moderate gait <br>impairments. To pursue this goal, the research activity followed two lines of action. Firstly, a <br>novel method for real-time gait phase estimate was developed. Secondly, novel assistive strategies <br>were explored to investigate the effects of hip assistance in specific end-users, i.e., individuals <br>with mild-to-moderate neurological gait disorders and transfemoral amputees.<br>This thesis proposed a novel wavelet-based gait phase estimation method capable of: (i) <br>continuously tracking the user gait phase and (ii) identifying in real time relevant biomechanical <br>gait events (i.e., initial and final foot contact) of physiological and pathological gait patterns. The <br>algorithm uses only hip joint angle signals (measured by encoders onboard the hip exoskeleton), <br>thus avoiding the use of additional sensors that could challenge the overall system <br>usability/acceptability and dependability in out-the-lab applications. The proposed method <br>(patented method WO2022053934) proves that distal events, related to foot–ground interaction <br>can be reliably detected by using hip joint angles. Experimental tests with healthy subjects <br>indicated that the method can robustly adapt to different walking speeds. Experimental tests <br>carried out with transfemoral amputees and post-stroke subjects showed that the proposed method <br>is reliable and accurate also with pathological gait patterns.<br>Furthermore, in this thesis, clinical investigations were designed to explore the effectiveness <br>of hip assistance for two different objectives: (i) to improve the walking economy in transfemoral <br>amputees and (ii) to increase the walking speed and induce the recovery of a physiological gait <br>pattern in individuals with neurological disorders. For the first application, although achieved <br>results showed that tailored energy injection at the residual and intact limbs of transfemoral <br>amputees could be promising, further research is needed for a better understanding of the real<br>benefits in daily-life scenarios. For the second application, the use of the hip exoskeleton was <br>investigated both as a gait trainer and as a mobility extender. In addition, a method for tailoring <br>the hip assistance based on subject-specific gait impairments was developed (patented method <br>WO2022137031). Experimental tests carried out with eighteen post-stroke survivors suggested <br>that the proposed approach is promising to improve their walking performance, paving the way <br>for future clinical investigations.