BISTABLE STRUCTURES ENABLE PASSIVE TRANSITIONS IN MOBILE ROBOTS

Making robots more capable, agile, and efficient will require careful design of the robot’s mechanicalbody to match task requirements. Passive components allow a robot to perform a task without a dedicated actuator, often improving both power consumption and overall performance. In this thesis, we investigate robotic applications of bistable mechanisms, mechanical structures that exhibit two stable static equilibria, to enable passive actuation and locking for systems with discrete task modes. More specifically, the main theoretical contribution of this thesis is a method for determining theactuation force requirements for dynamically-actuated bistable mechanisms, where inertial forces are responsible for producing snap-through. In this case, there is a direct relationship between the inertial forces and the output force of the actuators that produce the associated motions. We find that the minimum actuating force required for snap-through depends on the ratio between the mass on the bistable structure and the robot’s total mass, and that it also depends on friction but not on viscous damping. The main experimental contribution includes demonstrations of the impact of bistable mechanisms on grasping and flying systems. For perching, we show that attaching a linkage to a passive bistable structure augments a gripper’s locking strength, leading to passive grasping with a high strength-to-weight ratio. For aerial reconfiguration, we demonstrate that the energy cost of passive dynamic transformation can be offset by the efficiency gains of transforming from a quadrotor to a fixed wing mode. Overall, this thesis shows that passive bistable mechanisms can eliminate the need for task-specific actuators by repurposing existing locomotion actuators.

Author dc:creator

• Weakly, Jessica

Advisor dc:contributor.advisor

• Sung, Cynthia

• Electrical Engineering
• Mechanical Engineering
• Engineering

Language dc:language.iso

en

Repository record dc:identifier.uri

https://repository.upenn.edu/handle/20.500.14332/60488

OAI identifier oai:identifier

oai:repository.upenn.edu:20.500.14332/60488