This thesis presents methods for implementing robust hexpod locomotion on an autonomous robot with many sensors and actuators. The controller is based on the Subsumption Architecture and is fully distributed over approximately 1500 simple, concurrent processes. The robot, Hannibal, weighs approximately 6 pounds and is equipped with over 100 physical sensors, 19 degrees of freedom, and 8 on board computers. We investigate the following topics in depth: distributed control of a complex robot, insect-inspired locomotion control for gait generation and rough terrain mobility, and fault tolerance. The controller was implemented, debugged, and tested on Hannibal. Through a series of experiments, we examined Hannibal's gait generation, rough terrain locomotion, and fault tolerance performance. These results demonstrate that Hannibal exhibits robust, flexible, real-time locomotion over a variety of terrain and tolerates a multitude of hardware failures.

Cette thèse s'inscrit dans un projet de recherche dont l'objectif est d'améliorer l'autonomie des personnes confinées en fauteuil roulant manuel grâce à des études en situation réelle de locomotion. Un modèle mécanique a été développé mettant en relation les mouvements du système sujet-fauteuil avec les efforts qui s'y exercent. Après avoir étalonné les capteurs nécessaires, plusieurs expérimentations ont permis de valider une méthode d'estimation de la résultante des forces de résistance à l'avancement, et une méthode de reconstruction de la trajectoire suivie par le fauteuil. Enfin, les paramètres biomécaniques qui interviennent dans le modèle ont été quantifiés lors d'une expérimentation en situation réelle qui a permis d'étudier l'influence des mouvements du sujet sur les déplacements du fauteuil. A terme, cette approche devrait permettre de déterminer les paramètres biomécaniques pertinents et d'optimiser les méthodes de rééducation et les réglages des fauteuils

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This thesis is about control and balance stability of leggedlocomotion. It also presents a combination of tools that makesit easier to design controllers for large and complicated robotsystems. The thesis is divided into four parts. The first part studies and analyzes how walking machines arecontrolled, examining the literature of over twenty machinesbriefly, and six machines in detail. The goal is to understandhow the controllers work on a level below task and pathplanning, but above actuator control. Analysis and comparisonis done in terms of: i) generation of trunk motion; ii)maintaining balance; iii) generation of leg sequence andsupport patterns; and iv) reflexes. The next part describes WARP1, a four-legged walking robotplatform that has been builtwith the long term goal of walkingin rough terrain. First its modular structure (mechanics,electronics and control) is described, followed by someexperiments demonstrating basic performance. Finally themathematical modeling of the robot’s rigid body model isdescribed. This model is derived symbolically and is general,i.e. not restricted to WARP1. It is easily modified in case ofa different number of legs or joints. During the work with WARP1, tools for model derivation,control design and control implementation have been combined,interfaced and augmented in order to better support design andanalysis. These tools and methods are described in the thirdpart. The tools used to be difficult to combine, especially fora large and complicated system with many signals and parameterssuch as WARP1. Now, models derived symbolically in one tool areeasy to use in another tool for control design, simulation andfinally implementation, as well as for visualization andevaluation—thus going from equation to action. In the last part we go back to“equation”wherethese tools aid the study of balance stability when complianceis considered. It is shown that a legged robot in a“statically balanced”stance may actually beunstable. Furthermore, a criterion is derived that shows when aradially symmetric“statically balanced”stance on acompliant surface is stable. Similar analyses are performed fortwo controllers of legged robots, where it is the controllerthat cause the compliance. <b>Keywords</b>legged locomotion, control, balance, leggedmachines, legged robots, walking robots, walking machines,compliance, platform stability, symbolic modeling

This thesis presents actuators used in autonomous microsystems. Characteristic for all actuators presented is the low drive voltage and the low power consumption. Different motion mechanisms have been studied and applied in various locomotion modules for microrobots. High resolution movement of a monolithic piezoceramic PZT rotational arm module, using a quasi-static motion mechanism, was demonstrated in a 10x10x20 mm3 autonomous robot. The rotational arm comprises multilayer PZT bimorphs and is fabricated by a wet-building technology. The multilayer approach enables operation of the modules at the low drive voltages provided by the robot electronics. In addition a locomotion module has been designed and fabricated based on the above principles. A three-legged locomotion module with piezoceramic unimorphs, moving by tapping the legs against the floor, has been investigated. Characteristics such as low power consumption, high velocities, low drive voltages and a high weight carrying capability were demonstrated using a resonant motion mechanism. Highly miniaturized three-legged locomotion modules were developed for a 3x3x3 mm3 autonomous microrobot. The modules comprise a multilayer structure of the electroactive copolymer P(VDF-TrFE) on a flexible printed circuit board (FPC) substrate. A novel multilayer fabrication process suitable for mass production was used. It is based on sequential deposition of spun cast copolymer with evaporated aluminum electrodes. Reactive ion etching is used to microstructure the copolymer and the FPC. The mechanical deformability of the FPC is exploited when folding the 2D FPC-multilayer assembly into 3D locomotion modules. Locomotion was demonstrated by moving a glass slider corresponding to the robot weight. A modular building technology for microsystems is presented. It uses surface mounting technology and conductive adhesives to assemble modules on a double-sided FPC. Complex geometries were achieved by subsequent folding the FPC. The feasibility of the technology was demonstrated by assembly of the 3x3x3 mm3 autonomous microrobots.

The ability to control balance and stability are essential to prevent falls during locomotion. Maintenance of stable locomotion is challenging especially when complicated by amputation and prosthesis use. Humans employ several motor strategies to maintain stability during walking on complex terrain: decreasing walking speed, adjusting stride length and stance width, lowering the center of mass, and prolonging the double support time. The mechanisms of selecting these motor strategies by the primary motor cortex are unknown and cannot be studied directly in humans. There is also little information about dynamic stability of prosthetic gait with bone-anchored prostheses, which are thought to provide sensory feedback to the amputee through osseoperception. Therefore, the Specific Aims of my research were to (1) evaluate dynamic stability and the activity of the primary motor cortex during walking with different constraints on the base of support and (2) develop an animal model to evaluate mechanics and stability of prosthetic gait with a bone-anchored prosthesis. To address these aims, I developed a feline model that allows for investigating (1) the role of the primary motor cortex in regulation of dynamic stability of intact locomotion, (2) skin and bone integration with a percutaneous porous titanium implant facilitating prosthetic attachment, and (3) dynamic stability of walking on a bone-anchored prosthesis. The results of Specific Aim 1 demonstrated that the area and shape of the base of support influence the margins of dynamic stability during quadrupedal walking. For example, I found that the animal is dynamically unstable in the sagittal plane and frontal plane (although to a lesser degree) during a double-support by a forelimb and the contralateral hindlimb. Elevated neuronal activity from the right forelimb representation in the primary motor cortex during these phases suggests that the motor cortex may contribute to selection of paw placement location and thus to regulation of stability. The results of Specific Aim 2 on the development of skin-integrated bone-anchored prostheses demonstrated the following. Skin ingrowth into 3 types of porous titanium pylons (pore sizes 40-100 μm and 100-160 μm and nano-tubular surface treatment) implanted under skin of rats was seen 3 and 6 weeks after implantation, and skin filled at least 30% of available implant space. The duration of implantation, but not implant pore size (in the studied range) or surface treatment statistically influenced skin ingrowth; pore size and time of implantation affected the implant extrusion length (p<0.05). The implant type with the slowest extrusion rate (pore size 40-100 μm) was used in a feline model of prosthetic gait with skin-integrated bone-anchored prosthesis. The developed implantation methods, rehabilitation procedures and feline prostheses allowed 2 animals to utilize skin- and bone-integrated prostheses for dynamically stable locomotion. Prosthetic gait analysis demonstrated that the animals loaded the prosthetic limb, but increased reliance on intact limbs for weight support and propulsion. The obtained results and developed animal model improve the understanding of locomotor stability control and integration of skin with percutaneous implants.

This thesis investigates a simple dynamic model of the hind leg of a beetle during initiation of a step. The primary assumption was that the full load of the body was carried on the hind leg during this time. That is, the only forces on the body were that of the hind leg and gravity and their resultant produced forward acceleration. Only two dimensional models were used in this study. This was justified since the beetle is bilaterally symmetrical. However, it required the assumption that hind legs were positioned symmetrically and it limited the investigation to forward acceleration in a straight line. Models with two and three links were tested. The two link model assumed the body has no motion relative to the upper legs; that is the muscles were strong enough to prevent movement at the joint between body and leg. The three link model assumed only friction prevented movement at the joint between body and leg. Dynamic equations were developed using Lagrangian mechanics. These equations were integrated using the 4th order Runge-Kutta algorithm. Both models were driven by applying a constant torque at the joint between upper and lower segments. Driving torque was adjusted to minimize verical movement of body center of mass. Initial position of body center of mass relative to foot was varied to examine it's influence on both horizontal travel of body, center of mass and driving torque required for this travel. For both models horizontal travel was less dependent on initial height of body center-of-mass than on initial horizontal position. For both models required driving torque increased with decrease in initial height of body center-of-mass and with increase of initial horizontal distance from foot to body center-of-mass. For both models maximum horizontal travel was attained with minimum initial height of body center-of-mass and minimum initial horizontal distance between foot and body center-of-mass. For the two link model, maximum horizontal travel was approximately half of the total leg length while for the three link model the equivalent number was approximately one quarter, of total leg length. / Graduation date: 1992

The significant development in medical diagnostics and imaging has brought up a lot of new wireless capsule endoscopes coming to health care market. The capsule has been able to minimize patient discomfort and pain during digestive tract screening with less risk of infection and harmless to body organs. This kind of medical procedure is less invasive and gives a great impact compared to the traditional method. Although pill-shaped capsules have existed for over 11 years by now and are currently being used successfully in medical screening to study the GI tract, these systems are passive and are dependent to the peristaltic movement of the gastric wall to propel. The aim of this work is to provide the electronics needed to control an endoscopic capsule robot and the electronics needed to enable active locomotion and advanced vision functions (like autofocus). Enabling such functions the capsules will be able to perform screening, diagnosis and therapy. Such capsule robot has been designed in the framework of the “Versatile Endoscopic Capsule for Gastrointestinal Tumour Recognition and Therapy” (VECTOR) project. This project pursues the goal of realizing smart pill technologies and applications for gastrointestinal (GI) diagnosis and therapy. The overall medical goal of the project is to enable medical devices through advanced technology that can dramatically improve early detection and treatment of GI early cancers and cancer precursors. The main technological objective of the project is the take-up of microsystems and sub-components and their integration into robotic, mobile pill devices for useful and large impact applications in the medical field.

Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.

Walking around in dynamically changing environments require the integration of three of our sensory systems: visual, vestibular, and kinesethic. Vision is the only modality of these three sensory systems that provides information at a distance for proactively controlling locomotion (Gibson, 1958). The visual system provides information about self-motion, about body position and body segments relative to one another and the environment, and environmental information at a distance (Patla, 1998). Gibson (1979) developed the idea that everyday behaviour is controlled by perception-action coupling between an action and some specific information picked up from the optic flow that is generated by that action. Such that visual perception guides the action required to navigate safely through an environment and the action in turn alters perception. The objective of my thesis was to determine how well perception and action are coupled when approaching and walking through moving doors with dynamically changing apertures. My first two studies were grouped together and here I found that as the level of threat increased, the parameters of control changed and not the controlling mechanism. The two dominant action control parameters observed were a change in approach velocity and a change in posture (i. e. shoulder rotation). These findings add to previous work done in this area using a similar set-up in virtual reality, where after much practice participants increased success rate by decreasing velocity prior to crossing the doors. In my third study I found that visual fixation patterns and action parameters were similar when the location of the aperture was predictable and when it was not. Previous work from other researchers has shown that vision and a subsequent action are tightly coupled with a latency of about 1second. I have found that vision only tightly couples action when a specific action is required and the threat of a collision increases. My findings also point in the same direction as previous work that has shown that individuals look where they are going. My last study was designed to determine if we go where we are looking. Here I found that action does follow vision but is only loosely correlated. The most important and common finding from all the studies is that at 2 seconds prior to crossing the moving doors (any type of movement) vision seems to have the most profound effect on action. At this time variability in action is significantly lower than at prior times. I believe that my findings will help to understand how individuals use vision to modify actions in order to avoid colliding with other people or other moving objects within the environment. And this knowledge will help elderly individuals to be better able to cope with walking in cluttered environments and avoid contacting other objects.