Soft Robotics: Design for Simplicity, Performance, and Robustness of Robots for Interaction with Humans.

This thesis deals with the design possibilities concerning the next generation of advanced Robots. Aim of the work is to study, analyse and realise artificial systems that are essentially simple, performing and robust and can live and coexist with humans. The main design guideline followed in doing so is the Soft Robotics Approach, that implies the design of systems with intrinsic mechanical compliance in their architecture. The first part of the thesis addresses design of new soft robotics actuators, or robotic muscles. At the beginning are provided information about what a robotic muscle is and what is needed to realise it. A possible classification of these systems is analysed and some criteria useful for their comparison are explained. After, a set of functional specifications and parameters is identified and defined, to characterise a specific subset of this kind of actuators, called Variable Stiffness Actuators. The selected parameters converge in a data-sheet that easily defines performance and abilities of the robotic system. A complete strategy for the design and realisation of this kind of system is provided, which takes into account their me- chanical morphology and architecture. As consequence of this, some new actuators are developed, validated and employed in the execution of complex experimental tasks. In particular the actuator VSA-Cube and its add-on, a Variable Damper, are developed as the main com- ponents of a robotics low-cost platform, called VSA-CubeBot, that v can be used as an exploratory platform for multi degrees of freedom experiments. Experimental validations and mathematical models of the system employed in multi degrees of freedom tasks (bimanual as- sembly and drawing on an uneven surface), are reported. The second part of the thesis is about the design of multi fingered hands for robots. In this part of the work the Pisa-IIT SoftHand is introduced. It is a novel robot hand prototype designed with the purpose of being as easily usable, robust and simple as an industrial gripper, while exhibiting a level of grasping versatility and an aspect comparable to that of the human hand. In the thesis the main theo- retical tool used to enable such simplification, i.e. the neuroscience– based notion of soft synergies, are briefly reviewed. The approach proposed rests on ideas coming from underactuated hand design. A synthesis method to realize a desired set of soft synergies through the principled design of adaptive underactuated mechanisms, which is called the method of adaptive synergies, is discussed. This ap- proach leads to the design of hands accommodating in principle an arbitrary number of soft synergies, as demonstrated in grasping and manipulation simulations and experiments with a prototype. As a particular instance of application of the method of adaptive syner- gies, the Pisa–IIT SoftHand is then described in detail. The design and implementation of the prototype hand are shown and its effec- tiveness demonstrated through grasping experiments. Finally, control of the Pisa/IIT Hand is considered. Few different control strategies are adopted, including an experimental setup with the use of surface Electromyographic signals

Functional Resistance Training During Walking: Design, Testing, and Evaluation of Passive and Semi-Passive Wearable Devices for Providing Targeted Resistance to the Leg During Gait

Injuries to the neuromusculoskeletal systems often result in muscle weakness, abnormal coordination strategies, and gait impairments. Functional resistance training during walking—where a patient walks while a device increases loading on the leg—is an emerging approach to combat these symptoms. While simple passive devices (i.e., ankle weights and resistance bands) can be applied for this training, rehabilitation robots have more potential upside because they can be controlled to treat multiple gait abnormalities and can be monitored by clinicians. However, the cost of conventional robotic devices limits their use in the clinical or home setting. Hence, in this dissertation, we designed, developed, and tested passive and semi-passive wearable exoskeleton devices as low-cost solutions for providing controllable/configurable functional resistance training during walking. We developed and tested two passive exoskeleton devices for providing resistance to walking and tested their effects on able-bodied participants and stroke survivors. First, we created a patented device that used a passive magnetic brake to provide a viscous (i.e., velocity-dependent) resistance to the knee. The resistive properties of the device could be placed under computer control (i.e., made semi-passive) to control resistance in real-time. Next, we created a passive exoskeleton that provided an elastic (i.e., position-dependent) resistance. While not controllable, this device was highly configurable. Meaning it could be used to provide resistance to joint flexion, extension, or to both (i.e., bidirectionally). Human subjects testing with these devices indicated they increased lower-extremity joint moments, powers, and muscle activation during training. Training also resulted in significant aftereffects—a potential indicator of therapeutic effectiveness—once the resistance was removed. A separate experiment indicated that individuals often kinematically slack (i.e., reduce joint excursions to minimize effort) when resistance is added to the limb. We also found that providing visual feedback of joint angles during training significantly increased muscle activation and kinematic aftereffects (i.e., reduced slacking). With passive devices, the type of passive element used largely dictates the muscle groups, types of muscle contraction, joint actions, and the phases of gait when a device is able to apply resistance. To examine this issue, we compared the training effects of viscous and elastic devices that provided bidirectional resistance to the knee during gait. Additionally, we compared training with viscous resistances at the hip and knee joints. While the resistance type and targeted joint altered moments, powers, and muscle activation patterns, these methods did not differ in their ability to produce aftereffects, alter neural excitability, or induce fatigue in the leg muscles. While this may indicate that the resistance type does not have a large effect on functional resistance training during walking, it is possible that an extended training with these devices could produce a different result. Lastly, we used musculoskeletal modeling in OpenSim to directly compare several strategies that have been used to provide functional resistance training to gait in the clinic or laboratory setting. We found that devices differed in their ability to alter gait parameters during walking. Hence, these findings could help clinicians when selecting a resistive strategy for their patients, or engineers when designing new devices or control schemes. Collectively, this dissertation introduces a new class of wearable devices for functional resistance training during walking and establishes the biomechanical and neurophysiological effects and the clinical potential of these devices in able-bodied and stroke survivors.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169867/1/epwiv_1.pd