The Design and Application of Soft Electromagnetic Actuators
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Kohls, Noah
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Abstract
Soft robots offer remarkable advantages in flexibility, shape-shifting capabilities, and human-robot compatibility. These robots use compliant and elastic materials to bend and deform, enabling complex motions. Despite their benefits, they often lack the speed and power of conventional robots or rely on rigid components. This work introduces a new approach to developing soft systems utilizing soft electromagnetic actuators. Novel designs are explored for soft actuators using liquid metal conductors, compliant permanent magnets, and flexible/elastic polymers. For force and field estimation of these unique actuator topologies, systematic modeling techniques for magnetic and electromagnetic systems are outlined. Additionally, the mechanical, electrical, and magnetic properties of soft materials are discussed, along with trade-offs for designing novel soft actuators.
To demonstrate these concepts, several unique architectures are discussed. First, bioinspired soft electromagnetic actuators are developed to mimic the pulsing motion of a Xenia coral. The high-stroke linear design for this concept uses soft flexure joints to enable arm movement up to 42 mm with a bandwidth of 30 Hz. Next, a new soft actuator for AR/VR applications is explored using hydraulically amplified electromagnetic forces to render vibration, squeeze, and localized sensations for haptic feedback. The soft actuator can exert up to 5.2 N of force, has a bandwidth of up to 30 Hz in air, and maintains low operating temperatures (<36°C at 1.3 W), making it safe for haptic applications. To demonstrate how soft actuators can be used for realistic robotic applications, a fully soft rotary motor and novel magnetic contact sensors are developed. The motor has a stall torque of 2.5 to 3 mN⋅m, and a no-load speed of up to 4000 rpm, making it orders of magnitude faster and more powerful than previously developed soft rotary actuators. Finally, soft electromagnetic oscillators that can expand and compress are designed by uniquely integrating liquid metal for both actuation and sensing. This novel bistable design only requires power to switch states and is used for crawling, hopping, and swimming locomotion. The self-regulating astable design requires only a battery to operate and can continuously oscillate at 27 Hz with 18 W. These innovative designs bridge the gap between soft and conventional actuators, paving the way for the next generation of compliant and intelligent robots.
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2024-05-17
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Text
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Dissertation