Low-grade thermal energy, either from waste heat or from natural resources, constitutes an enormous energy reserve that remains to be fully harvested. Harvesting low-grade heat is challenging because of the low Carnot efficiency. Among various thermal energy harvesting mechanisms available for capturing low-grade heat (temperature less than 100 °C), the thermomagnetic effect has been found to be quite promising. In this study, we demonstrate a scalable thermomagnetic energy harvester architecture that exhibits 140% higher power density compared to the previously published spring–mass designs. The alternating force required to oscillate the thermomagnetic mass is generated through the interaction between two magnetic forces in opposite directions. We employed numerical modeling to illustrate the behavior of a thermomagnetic device under different operating conditions and to obtain the optimal hot-side and cold-side temperatures for continuous mode operations. A miniaturized thermomagnetic harvester was fabricated and experiments were conducted to systematically evaluate the performance. The prototype was found to exhibit an oscillation frequency of 0.33 Hz, a work output of 0.6 J/kg/cycle, and a power density of 0.2 W/kg of gadolinium under the temperature difference of 60 K.

An investigation of the biological locomotion and control mechanisms observed in Diplopoda (millipedes) is performed in order to provide design rules for the development of a crawling millipede-inspired robot (millibot). Millipedes have long bodies with numerous pairs of legs, which allows them to perform higher ranges of motion compared to other arthropods traveling in the same environment. The relevant features of millipedes with respect to robotics include: (i) metachronal locomotion, (ii) ability to burrow through different substrates, and (iii) capability to traverse uneven terrains and align themselves swiftly when fallen over. A mathematical model is proposed describing these locomotion features that will provide guidance towards emulating these actions in a millibot.

A detailed model for the locomotory mechanics used by millipedes is provided here through systematic experimentation on the animal and validation of observations through a biomimetic robotic platform. Millipedes possess a powerful gait that is necessary for generating large thrust force required for proficient burrowing. Millipedes implement a metachronal gait through movement of many legs that generates a traveling wave. This traveling wave is modulated by the animal to control the magnitude of thrust force in the direction of motion for burrowing, climbing, or walking. The quasi-static model presented for the millipede locomotion mechanism matches experimental observations on live millipedes and results obtained from a biomimetic robotic platform. The model addresses questions related to the unique morphology of millipedes with respect to their locomotory performance. A complete understanding of the physiology of millipedes and mechanisms that provide modulation of the traveling wave locomotion using a metachronal gait to increase their forward thrust is provided. Further, morphological features needed to optimize various locomotory and burrowing functions are discussed. Combined, these results open opportunity for development of biologically inspired locomotory methods for miniaturized robotic platforms traversing terrains and substrates that present large resistances.

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When cranes lift heavy payloads off the ground, the payload may slide or swing sideways unexpectedly. This dangerous motion occurs when the payload is not directly beneath the overhead suspension point of the hoist cable. Given that cable suspension points are usually tens of feet, and perhaps hundreds of feet above the payload, it is very difficult for crane operators to know if the hoist cable is perfectly vertical before they start to lift the payload off the ground. Inevitably, some horizontal motion of the payload will occur at lift off. If an off-center lift creates substantial horizontal motion, then it can create significant hazards for the human operators, the crane, the payload, and the surrounding environment. This paper develops a three-dimensional dynamic model of off-centered lifts. The accuracy of the model is experimentally investigated using a 10-ton bridge crane.