Design and process/measurement for immersed element control in a reconfigurable vertically falling soap film

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 24-25).Reinforcement learning has proven successful at harnessing the passive dynamics of underactuated systems to achieve least energy solutions. However, coupled fluid-structural models are too computationally intensive for in-the-loop control in viscous flow regimes. My vertically falling soap film will provide a reconfigurable experimental environment for machine learning controllers. The real-time position and velocity data will be collected with a High Speed Video system, illuminated by a Low Pressure Sodium Lamp. Approximating lines of interference within the soap film to known pressure variations, controllers will shape downstream flow to desired conditions. Though accurate measurement still eludes those without Laser Doppler Velocimetry, order of magnitude Reynolds numbers can be estimated to describe the regime of controller inquiry.by John Glowa.S.B

Swimming dynamics of a micro-organism in a couple stress fluid : a rheological model of embryological hydrodynamic propulsion

Mathematical simulations of embryological fluid dynamics are fundamental to improving clinical understanding of the intricate mechanisms underlying sperm locomotion. The strongly rheological nature of reproductive fluids has been established for a number of decades. Complimentary to clinical studies, mathematical models of reproductive hydrodynamics provide a deeper understanding of the intricate mechanisms involved in spermatozoa locomotion which can be of immense benefit in clarifying fertilization processes. Although numerous non-Newtonian studies of spermatozoa swimming dynamics in non-Newtonian media have been communicated, very few have addressed the micro-structural characteristics of embryological media. This family of micro-continuum models include Eringen’s micro-stretch theory, Eringen’s microfluid and micropolar constructs and V.K. Stokes’ couple-stress fluid model, all developed in the 1960s. In the present paper we implement the last of these models to examine the problem of micro-organism (spermatozoa) swimming at low Reynolds number in a homogenous embryological fluid medium with couple stress effects. The micro-organism is modeled as with Taylor’s classical approach, as an infinite flexible sheet on whose surface waves of lateral displacement are propagated. The swimming speed of the sheet and rate of work done by it are determined as function of the parameters of orbit and the couple stress fluid parameter (α). The perturbation solutions are validated with a Nakamura finite difference algorithm. The perturbation solutions reveal that the normal beat pattern is effective for both couple stress and Newtonian fluids only when the amplitude of stretching wave is small. The swimming speed is observed to decrease with couple stress fluid parameter tending to its Newtonian limit as alpha tends to infinity. However the rate of work done by the sheet decreases with α and approaches asymptotically to its Newtonian value. The present solutions also provide a good benchmark for more advanced numerical simulations of micro-organism swimming in couple-stress rheological biofluids

Developing Design and Analysis Framework for Hybrid Mechanical-Digital Control of Soft Robots: from Mechanics-Based Motion Sequencing to Physical Reservoir Computing

The recent advances in the field of soft robotics have made autonomous soft robots working in unstructured dynamic environments a close reality. These soft robots can potentially collaborate with humans without causing any harm, they can handle fragile objects safely, perform delicate surgeries inside body, etc. In our research we focus on origami based compliant mechanisms, that can be used as soft robotic skeleton. Origami mechanisms are inherently compliant, lightweight, compact, and possess unique mechanical properties such as– multi-stability, nonlinear dynamics, etc. Researchers have shown that multi-stable mechanisms have applications in motion-sequencing applications. Additionally, the nonlinear dynamic properties of origami and other soft, compliant mechanisms are shown to be useful for ‘morphological computation’ in which the body of the robot itself takes part in performing complex computations required for its control. In our research we demonstrate the motion-sequencing capability of multi-stable mechanisms through the example of bistable Kresling origami robot that is capable of peristaltic locomotion. Through careful theoretical analysis and thorough experiments, we show that we can harness multistability embedded in the origami robotic skeleton for generating actuation cycle of a peristaltic-like locomotion gait. The salient feature of this compliant robot is that we need only a single linear actuator to control the total length of the robot, and the snap-through actions generated during this motion autonomously change the individual segment lengths that lead to earthworm-like peristaltic locomotion gait. In effect, the motion-sequencing is hard-coded or embedded in the origami robot skeleton. This approach is expected to reduce the control requirement drastically as the robotic skeleton itself takes part in performing low-level control tasks. The soft robots that work in dynamic environments should be able to sense their surrounding and adapt their behavior autonomously to perform given tasks successfully. Thus, hard-coding a certain behavior as in motion-sequencing is not a viable option anymore. This led us to explore Physical Reservoir Computing (PRC), a computational framework that uses a physical body with nonlinear properties as a ‘dynamic reservoir’ for performing complex computations. The compliant robot ‘trained’ using this framework should be able to sense its surroundings and respond to them autonomously via an extensive network of sensor-actuator network embedded in robotic skeleton. We show for the first time through extensive numerical analysis that origami mechanisms can work as physical reservoirs. We also successfully demonstrate the emulation task using a Miura-ori based reservoir. The results of this work will pave the way for intelligently designed origami-based robots with embodied intelligence. These next generation of soft robots will be able to coordinate and modulate their activities autonomously such as switching locomotion gait and resisting external disturbances while navigating through unstructured environments

Passive Actuation of a Planetary Rover to Assist Sandy Slope Traverse

This thesis introduces the design of a novel locomotive methodology. The problem being addressed is the traverse of unmanned locomotion over sandy inclined traverses. This is a special terramechanical issue regarding terrain or regolith that is non-cohesive in nature. The method uses a planetary exploration rover, Solar Rover 2 as its base. The proposed solution methodology includes a passively-actuated leg affixed to the rover to assist in slope traversal. Proposed physical implementations are designed and virtual representations are created, studied, and simulated in SolidWorks. This solution is justified through the use of a simulation designed in MATLAB

Micromechanics of passive and active inclusions in granular media

Passive and active inclusions in granular materials play an increasingly important role in the development of sustainable infrastructure. Passive inclusions, such as geogrids, have been shown to augment the service life of roadways and reduce aggregate consumption in pavement base layers. This is possible due to the aggregate-geogrid composite action, that results in the redistribution of traffic loads. The present study presents three-dimensional models that simulate the cyclic-loading behavior of geogrid-reinforced base layers using the discrete element method. It introduces a new framework by which upper and lower performance bounds are established by simulating unreinforced and perfectly reinforced aggregate bases. The model works as a tool for systematic prototyping of new geogrid geometries and mechanical properties. Furthermore, important insights into how aggregate morphology works in combination with different geogrids were obtained via a parametric study. The sustainability of linear infrastructure can also be improved with the use of active inclusions for thorough soil exploration and characterization. Self-motile probes are an emergent technology that will enable multidirectional testing of soils in situ. The locomotion systems of several of these technologies have been inspired by annelid peristalsis. Annelids such as the earthworm Lumbricus terrestris use synchronized muscle expansion and contraction to anchor portions of their segmented bodies while other portions push into the medium. In this doctoral work, the peristaltic locomotion and the design of burrowing robots are investigated on multiple fronts. First, the anchorage mechanism developed by expanded segments is studied by conducting pullout experiments in sand and numerical modeling using the discrete element method. The results revealed the expansion ratio to be critical in the development of anchorage resistance by promoting different soil responses. Subsequently, the effect of tip shape in reducing penetration resistance to enable greater advancement into granular beds is investigated using experiments and numerical modeling with the discrete element method. Results reveal that under low interface friction, penetration resistance can be decreased threefold by utilizing sharper tips. Later, the soil response to the anchor–push mechanism employed is investigated utilizing robotic analogs and X-ray micro-tomography. Results revealed a significant contrast between the soil response in loose and dense materials. Finally, a transparent synthetic soil testbed is developed. It enables the prototyping and testing of burrowing devices with real-time imaging. Results demonstrate the ability of the setup to provide important insight into geometrical aspects of robot designs that improve their advancement and overall performance.Ph.D

Modelling of capsule-intestine contact for a self-propelled capsule robot via experimental and numerical investigation

This is the final version. Available on open access from Springer Verlag via the DOI in this recordThis paper studies the modelling of capsuleintestine contact through experimental and numerical investigation for designing a self-propelled capsule robot moving inside the small intestine for endoscopic diagnosis. Due to the natural peristalsis of the intestinal tract, capsule-intestine contact is multimodal causing intermittent high transit speed for the capsule, which leads to incomplete visualisation of the intestinal surface. Three typical conditions, partial and full contacts, between the small intestine and the capsule, are considered in this work. Extensive experimental testing and finite element analysis are conducted to compare the contact pressure on the capsule. Our analytical, experimental and numerical results show a good agreement. The investigation using a synthetic small intestine shows that the contact pressure could vary from 0.5 [kPa] to 16 [kPa] according to different contact conditions, i.e. expanding or contracting due to the peristalsis of the small intestine. Therefore, a proper control method or a robust stabilising mechanism, which can accommodate such a high pressure difference, will be crucial for designing the robot.Engineering and Physical Sciences Research Council (EPSRC

EuMoBot: Replicating Euglenoid Movement in a Soft Robot

Contains PCA for the larger robot and analysis of design parameters

Towards tactile sensing active capsule endoscopy

Examination of the gastrointestinal(GI) tract has traditionally been performed using tethered endoscopy tools with limited reach and more recently with passive untethered capsule endoscopy with limited capability. Inspection of small intestines is only possible using the latter capsule endoscopy with on board camera system. Limited to visual means it cannot detect features beneath the lumen wall if they have not affected the lumen structure or colour. This work presents an improved capsule endoscopy system with locomotion for active exploration of the small intestines and tactile sensing to detect deformation of the capsule outer surface when it follows the intestinal wall. In laboratory conditions this system is capable of identifying sub-lumen features such as submucosal tumours.Through an extensive literary review the current state of GI tract inspection in particular using remote operated miniature robotics, was investigated, concluding no solution currently exists that utilises tactile sensing with a capsule endoscopy. In order to achieve such a platform, further investigation was made in to tactile sensing technologies, methods of locomotion through the gut, and methods to support an increased power requirement for additional electronics and actuation. A set of detailed criteria were compiled for a soft formed sensor and flexible bodied locomotion system. The sensing system is built on the biomimetic tactile sensing device, Tactip, \cite{Chorley2008, Chorley2010, Winstone2012, Winstone2013} which has been redesigned to fit the form of a capsule endoscopy. These modifications have required a $360^{o}$ cylindrical sensing surface with $360^{o}$ panoramic optical system. Multi-material 3D printing has been used to build an almost complete sensor assembly with a combination of hard and soft materials, presenting a soft compliant tactile sensing system that mimics the tactile sensing methods of the human finger. The cylindrical Tactip has been validated using artificial submucosal tumours in laboratory conditions. The first experiment has explored the new form factor and measured the device's ability to detect surface deformation when travelling through a pipe like structure with varying lump obstructions. Sensor data was analysed and used to reconstruct the test environment as a 3D rendered structure. A second tactile sensing experiment has explored the use of classifier algorithms to successfully discriminate between three tumour characteristics; shape, size and material hardness. Locomotion of the capsule endoscopy has explored further bio-inspiration from earthworm's peristaltic locomotion, which share operating environment similarities. A soft bodied peristaltic worm robot has been developed that uses a tuned planetary gearbox mechanism to displace tendons that contract each worm segment. Methods have been identified to optimise the gearbox parameter to a pipe like structure of a given diameter. The locomotion system has been tested within a laboratory constructed pipe environment, showing that using only one actuator, three independent worm segments can be controlled. This configuration achieves comparable locomotion capabilities to that of an identical robot with an actuator dedicated to each individual worm segment. This system can be miniaturised more easily due to reduced parts and number of actuators, and so is more suitable for capsule endoscopy. Finally, these two developments have been integrated to demonstrate successful simultaneous locomotion and sensing to detect an artificial submucosal tumour embedded within the test environment. The addition of both tactile sensing and locomotion have created a need for additional power beyond what is available from current battery technology. Early stage work has reviewed wireless power transfer (WPT) as a potential solution to this problem. Methods for optimisation and miniaturisation to implement WPT on a capsule endoscopy have been identified with a laboratory built system that validates the methods found. Future work would see this combined with a miniaturised development of the robot presented. This thesis has developed a novel method for sub-lumen examination. With further efforts to miniaturise the robot it could provide a comfortable and non-invasive procedure to GI tract inspection reducing the need for surgical procedures and accessibility for earlier stage of examination. Furthermore, these developments have applicability in other domains such as veterinary medicine, industrial pipe inspection and exploration of hazardous environments

SMA-Based Muscle-Like Actuation in Biologically Inspired Robots: A State of the Art Review

New actuation technology in functional or "smart" materials has opened new horizons in robotics actuation systems. Materials such as piezo-electric fiber composites, electro-active polymers and shape memory alloys (SMA) are being investigated as promising alternatives to standard servomotor technology [52]. This paper focuses on the use of SMAs for building muscle-like actuators. SMAs are extremely cheap, easily available commercially and have the advantage of working at low voltages. The use of SMA provides a very interesting alternative to the mechanisms used by conventional actuators. SMAs allow to drastically reduce the size, weight and complexity of robotic systems. In fact, their large force-weight ratio, large life cycles, negligible volume, sensing capability and noise-free operation make possible the use of this technology for building a new class of actuation devices. Nonetheless, high power consumption and low bandwidth limit this technology for certain kind of applications. This presents a challenge that must be addressed from both materials and control perspectives in order to overcome these drawbacks. Here, the latter is tackled. It has been demonstrated that suitable control strategies and proper mechanical arrangements can dramatically improve on SMA performance, mostly in terms of actuation speed and limit cycles