Biomechatronic design of novel compliant active and passive joints for wearable robots

Wearable robots are a class of mechatronic systems intended to exchange energy with the environment and the human body for assistive, prosthetic or rehabilitative purposes. The conventional design approach starts with the definition of suitable technical specifications, which provide a set of constraints to the designer. The objective of the design phase is to find a solution of such constrained problem. While the conventional design methodology is still effective in several fields of robotics, a number of issues arise in the case of wearable robots, mainly related to the need of high efficiency, robustness and safety levels. Moreover, wearable robots have to cope with the human body own dynamics, which is rather complex and influenced by a number of concurrent biomechanical and neurological factors. In particular, the application of the concept of structural intelligence, as form of embodied intelligence, in the design of wearable robots can greatly simplify the achievement of the emergence of dynamic behaviors derived from the coupling of the human body and the wearable robot. Such machine would expectedly be lighter, more energy efficient and possibly simpler than machines designed in a conventional way. The development of efficient wearable robotic systems for rehabilitation and assistive purposes requires the synergistic deployment of advanced solutions involving multiple aspects, such as the design of the kinematic structure and of the actuation system. New compliant actuation solutions have been developed in recent years to establish a safe and effective physical human-robot interaction in rehabilitation and assistive wearable robots. The introduction of intrinsic compliance, as a form of structural intelligence, in the actuation system and in the passive joints of wearable robots is motivated by the necessity of improving safety and dynamical adaptability. Furthermore, in wearable robots for gait assistance, the exploitation of conservative compliant elements as energy buffers mimics the intrinsic dynamical properties of legs. In order to address this design challenge, this thesis described the design of novel active and passive joints for lower limbs wearable robots embedding innovative solutions to render different viscoelastic behaviors. Commercially available compliant components do not generally allow to obtain the desired requirements in terms of admissible peak loading demanded by gait assistance, while guaranteeing a compact and lightweight design. The high torque and power necessary for gait assistive robotic systems requires the use of custom-made springs, able to guarantee high performances with a compact and lightweight design. Two rotary Series Elastic Actuators and a passive viscoelastic joint have been developed. The working principles, the basic design choices regarding the overall architectures and the single components and the systems characterization are presented and discussed. The developed joints have been integrated in two wearable robots concepts: an active orthosis for knee assistance and a non-anthropomorphic lower limbs wearable robot for gait assistance. The wearable robot include two modules for the actuation of the hip/knee flexion/extension in the sagittal plane and for the actuation of the hip degrees of freedom outside the sagittal plane. The integration of the modules and the concept of the wearable robot are finally reported.