The Woodruff School

SUMMARY

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 thesis introduces a new approach to developing soft systems utilizing soft electromagnetic actuators. New designs are explored for soft actuators using liquid metal conductors, compliant permanent magnets, and flexible/elastic polymers. Modeling techniques for magnetic and electromagnetic systems enable force and field estimation for unique actuator topologies. Mechanical, electrical, and magnetic properties of soft materials are discussed, along with trade-offs for designing novel soft actuators. Unique architectures for bio-inspired soft electromagnetic actuators are developed to mimic the pulsing motion of a Xenia coral. A high-stroke linear design uses soft flexure joints to enable arm movement up to 42 mm with a bandwidth of 30 Hz. Following this work, a new design 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. The next actuator design enables rotational motion using a fully soft motor and novel magnetic contact sensors. 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 enable expanding and compressing motions by uniquely integrating liquid metal for both actuation and sensing. This novel bistable design can self-regulate or passively maintain its state for crawling, hopping, and swimming locomotion. The self-regulating design requires only a battery to operate and can continuously oscillate at 27 Hz with 18 W DC power. These innovative designs and applications bridge the gap between soft and conventional robotics, paving the way for the next generation of soft and intelligent robots.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Noah Kohls

TIME:	Wednesday, April 24, 2024, 3:00 p.m.

PLACE:	MARC Building, 114

TITLE:	The Design and Application of Soft Electromagnetic Actuators

COMMITTEE:	Dr. Ellen Mazumdar, Chair (Mechanical Engineering) Dr. Jun Ueda (Mechanical Engineering) Dr. Kok-Meng Lee (Mechanical Engineering) Dr. Priyanshu Agarwal (Meta Platforms Inc.) Dr. Bryan Ruddy (The University of Auckland)

SUMMARY 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 thesis introduces a new approach to developing soft systems utilizing soft electromagnetic actuators. New designs are explored for soft actuators using liquid metal conductors, compliant permanent magnets, and flexible/elastic polymers. Modeling techniques for magnetic and electromagnetic systems enable force and field estimation for unique actuator topologies. Mechanical, electrical, and magnetic properties of soft materials are discussed, along with trade-offs for designing novel soft actuators. Unique architectures for bio-inspired soft electromagnetic actuators are developed to mimic the pulsing motion of a Xenia coral. A high-stroke linear design uses soft flexure joints to enable arm movement up to 42 mm with a bandwidth of 30 Hz. Following this work, a new design 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. The next actuator design enables rotational motion using a fully soft motor and novel magnetic contact sensors. 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 enable expanding and compressing motions by uniquely integrating liquid metal for both actuation and sensing. This novel bistable design can self-regulate or passively maintain its state for crawling, hopping, and swimming locomotion. The self-regulating design requires only a battery to operate and can continuously oscillate at 27 Hz with 18 W DC power. These innovative designs and applications bridge the gap between soft and conventional robotics, paving the way for the next generation of soft and intelligent robots.