The objective of this research is to discover principles of ambulatory locomotion on homogeneous and heterogeneous granular substrates and create models of animal and robot interaction within such environments. Since interaction with natural substrates is too complicated to model, we take a robophysics approach – we create a terrain generation system where properties of heterogeneous multi-component substrates can be systematically varied to emulate a wide range of natural terrain properties such as compaction, orientation, obstacle shape/size/distribution, and obstacle mobility within the substrate. A schematic of the proposed system is discussed in detail in the body of this dissertation. Control of such substrates will allow for the systematic exploration of parameters of substrate properties, particularly substrate stiffness and heterogeneities. With this terrain creation system, we systematically explore locomotor strategies of simplified laboratory robots when traversing over different terrain properties. A key feature of this proposed work is the ability to generate general interaction models of locomotor appendages with such complex substrates. These models will aid in the design and control of future robots with morphologies and control strategies that allow for effective navigation on a large diversity of terrains, expanding the scope of terramechanics from large tracked and treaded vehicles on homogeneous ground to arbitrarily shaped and actuated locomotors moving on complex heterogeneous terrestrial substrates.

Studying animal mechanics is crucial in order to understand how signals in the neuromuscular system contribute to an organism’s behaviour and how force-sensing organs and sensory neurons interact. In particular, the connection between the nerves and the muscles responsible for the force generation in the neuromuscular system needs to be established. Knowledge of the locomotion forces can be beneficial for the development of therapies for muscle disorders, neurodegenerative and human genetic diseases, such as muscular dystrophy. The simplicity of the nematode Caenorhabditis elegans’ (C. elegans) nervous system, which is limited to 302 neurons, has made it an excellent model organism for studying animal mechanics which include mechanosensation and locomotion at the neuronal level. The advent of miniaturized force sensing devices has led to the proposal of various approaches for measuring C. elegans locomotion forces. However, these existing devices are relatively complex, involving complicated microfabrication procedures and are incapable of measuring forces exerted by C. elegans in motion. This thesis addresses these shortcomings by introducing a force sensor capable of continuously measuring the forces generated by C. elegans in motion. The system consists of a micropillar-based device made of polydimethylsiloxane (PDMS) only and a vision-based algorithm for resolving the worm force from the deflection of the cantilever-like pillars. The measured force is horizontal and equivalent to a point force acting at half of the pillar height. The microdevice, sub-pixel resolution for visual tracking of the deflection, and experimental technique form an integrated system for measuring dynamic forces of moving C. elegans with force resolution of 3.13 uN for worm body width of 100 um. A simple device fabrication process based on soft-lithography and a basic experimental setup, which only requires a stereo microscope with off-the-shelf digital camera mean that this method is accessible to most biological science laboratories. The results demonstrate that the proposed device is capable of quantifying multipoint forces of moving C. elegans rather than single-point forces for a worm sample. This allows one to simultaneously collect force data from up to eight measurements points on different worm body parts. This is a significant step forward as it enables researchers to explicitly quantify the relative difference in forces exerted by the worm’s different body segments during the worms’ movements. The device’s capability to determine multipoint forces during nematode motion can also generate meaningful data to compare forces associated with different worm body muscles, gaining new understanding on how these muscles function. The forces measured during locomotion in the micropillars could also be used to differentiate mutant phenotypes. Apart from locomotion forces, the device is also capable of conducting concurrent measurement of other locomotion parameters such as speed, body amplitude and wavelength, as well as undulation frequency. This additional information can be useful to further quantify phenotypic behaviour of C. elegans and deepen the understanding of the theory behind worm locomotion forces. The relationship between C. elegans locomotion forces and their environment has also been analyzed by variation of the pillar arrangement and spacing. The results indicate that the microstructured environment significantly affects the worm’s contraction force, locomotion speed and the undulation frequency. In addition, an alternative measurement technique was provided to measure worm forces on other substrates, such that worm locomotion behaviour in varying environments can be investigated further. The combination of the conventional measurement technique with the findings of worm locomotion on a glass substrate reported show promise for biological measurements and other sensing application such as tactile force. Additional functions of on-chip worm selection, sorting, and imaging have also been integrated with the device, rendering its potential to accommodate for high-throughput application of C. elegans force measurement and locomotion studies in the future. The primary contributions of this thesis are centered around four topics: the development of the PDMS micropillar array and its application to study C. elegans locomotion forces, the analysis of C. elegans muscular forces and locomotion patterns in microstructured environments, the investigation of the worm locomotion forces using different substrates and finally the integration of the PDMS micropillar with PDMS microvalve for on-chip worm selection and imaging. Although the results presented in this thesis focus on wild type C. elegans, the method can be easily applied to its mutants and other organisms.

No description available.

No description available.

No description available.

A major function of the central nervous system (CNS) during locomotion is the ability to maintain dynamic stability during threats to balance. The CNS uses reactive, predictive, and anticipatory mechanisms in order to accomplish this. Previously, stability has been estimated using single measures. Since the entire body works as a system, dynamic stability should be examined by integrating kinematic, kinetic, and electromyographical measures of the whole body. This thesis examines three threats to stability (recovery from a frontal plane surface translation, stepping onto and walking on a compliant surface, and obstacle clearance on a compliant surface). These threats to stability would enable a full body stability analysis for reactive, predictive, and anticipatory CNS control mechanisms. From the results in this study, observing various biomechanical variables provides a more precise evaluation of dynamic stability and how it is achieved. Observations showed that different methods of increasing stability (eg. Lowering full body COM, increasing step width) were controlled by differing CNS mechanisms during a task. This provides evidence that a single measure cannot determine dynamic stability during a locomotion task and the body must be observed entirely to determine methods used in the maintenance of dynamic stability.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Approved for public release; distribution is unlimited / "Human body motion tracking using inertial sensors requires an attitude estimation filter capable of tracking in all orientations. One way to represent orientation is to use Euler angles, but they have singularities and therefore are not suitable for human body tracking applications. Quaternions can be used to represent orientation without incurring singularities. A quaternion-based Kalman filter has been designed for this purpose and implemented in this thesis. Also, a new suboptimal algorithm to compute the quaternions based on magnetometer and accelerometer data is implemented. This new algorithm called "Factored Quaternion Algorithm" is computationally simpler than previous methods and provides a decoupling property from magnetometer and accelerometer data." p. i. / Lieutenant Junior Grade, Mexican Navy

Swimming is important to the ecology of many species of scallop but the effects of temperature upon swimming are not clear. The ecology and natural history of scallops is introduced followed by a description of the state of current knowledge of scallop swimming, muscle physiology and energetics. The effects of temperature and the mechanisms used by ectotherms to compensate for such changes over acute, seasonal and evolutionary timescales are discussed. Scallops are active molluscs, able to escape from predators using jet propelled swimming. Queen scallops (Aequipecten opercularis) were acclimated to 5,10 and 15°C in the laboratory and collected in Autumn (13±3°C) and Winter (8±2°C) in order to investigate seasonal acclimatisation. The first jetting cycle of escape responses in these animals was recorded using high-speed video (200-250fps). Whole-animal velocity and acceleration were determined while measurements of valve movement and jet area allowed the calculation of muscle shortening velocity, force and power output. Peak swimming speed was significantly higher at 15°C (0.37m.s⁻¹) than at 5°C (0.28m.s⁻¹). Peak acceleration was 77% higher at 15°C (7.88m.s⁻²) than at 5°C (4.44m.s⁻²). Mean cyclic power output was also higher at 15°C (31.3W.kg⁻¹) than at 5°C (23.3W.kg⁻¹). Seasonal comparison of swimming in freshly caught animals revealed significantly greater acceleration (x2 at 11°C) and velocity during jetting in Winter than in Autumn animals (ANCOVA). These were associated with significant increases in peak power output (x8 at 11 °C), force production and muscle shortening velocity. Actomyosin ATPase activity was significantly higher (31 % at 15°C) in winter animals with peptide mapping of the Myosin heavy chain showing no differences between groups. Increases in muscle power output were associated with reductions in the length of the jetting phase as a proportion of the overall cycle. As a result large changes in muscle performance resulted in large short-term whole body performance enhancement but little difference to velocity over the cycle. Measurements of the swimming performance of the Antarctic scallop were made from videos of escape responses. Animals were acclimated to +2 and -1 °C in the laboratory and compared to animals maintained at natural water temperature (0±0.5°C) at the time of experimentation. Adamussium was very sensitive to temperature change with the proportion of swimming responses being less common at higher temperatures and where an individual was exposed to temperatures above it's maintenance temperature. Analysis of the first jetting cycle of swimming was carried out as described in Chapter 2. These analyses revealed that over the small temperature range that the animals can tolerate swimming performance is strongly temperature dependent. Q₁₀s above 2 included those for thrust (3.74), mean cyclic swimming speed (2.46), mean cyclic power output (5.71) and mean muscle fibre shortening velocity (2.16). Adamussium did not demonstrate strong phenotypic plasticity with no significant differences in swimming of muscle performance between animals acclimated to different temperatures. Comparison of the relationship between swimming velocity and temperature in Adamussium and other species showed little evidence for evolutionary compensation for temperature with all data fitting to a single relationship with a Q₁₀ of 1.96 (0-20°C). Similar results were obtained for power output and the performance of in vitro muscle preparations. These results are discussed in the light of field studies revealing the low predator pressure and escape performance of wild Adamussium. In vivo ³¹P-Nuclear Magnetic Resonance Spectrometry (MRS) was used to measure the levels of ATP, Phospho-l-arginine (PLA) and inorganic phosphorous (PI) in the adductor muscle of the Antarctic scallop, Adamussium colbecki, and two temperate species, Aequipecten opercularis and Pecten maximus. Graded exercise regimes from light (1-2 contractions) to exhausting (failing to respond to further stimulation) were imposed upon animals of each species. MRS allowed non-invasive measurement of metabolite levels and intracellular pH at high time resolution (30-120s intervals) during exercise and throughout the prolonged recovery period. Significant differences were shown between the magnitude and form of the metabolic response with increasing levels of exercise. Short-term (first 15 minutes) muscle alkalosis was followed by acidosis of up to 0.2 pH units during the recovery process. Aequipecten had significantly higher resting muscle PLA levels than either Pecten or Adamussium, used a five-fold greater proportion of this store per contraction and was able to perform only half as many claps (maximum of 24) as the other species before exhaustion. All species regenerated their PLA store at a similar rate despite widely different environmental temperatures. The major results and their impact on our knowledge of biomechanics and it's temperature dependence are discussed. Suggestions for future research based upon the experimental findings and techniques developed are presented.