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Modeling and Control of Boundary Constrained Granular Swarm Robots
Title
Modeling and Control of Boundary Constrained Granular Swarm Robots
Creator
Mulroy, Declan Augustine
Date
2023
Description
Soft robots offer many advantages that traditional robotic systems do not. Soft robotic systems are able to safely interact with their...
Show moreSoft robots offer many advantages that traditional robotic systems do not. Soft robotic systems are able to safely interact with their environment and tolerate large deformations. This is due to being composed of soft materials, which allows them to be subjected to and experience large deformations. However, they still have limitations in their maneuverability, locomotion, and force exertion. Moreover, they usually require external tethering or other specialized systems, such as pneumatic devices, to function. To address some of these limitations, a novel class of robotic systems has emerged called a boundary-constrained granular swarm robot.A boundary-constrained granular swarm robot is composed of a closed-loop series of active sub-robots, each with the ability to locomote. Each sub-robot is connected to its neighbors with an elastic membrane, which forms a single robot. The membrane encloses a passive granular interior, which provides structure and allows the robot to switch between rigid and soft states via granular jamming phase transitions. This allows for the robotic system to exploit the desirable characteristics of both soft and rigid robots. However, there is limited research with regards to modeling and controlling this system due to its novelty. This thesis addresses this gap by presenting several simulation frameworks, which incorporates multi-body dynamics and non-smooth contact dynamics to model the forward dynamics of the system. These models are able to account for the frictional effects, and the contact forces experienced by the system. The developed models are verified through experimental prototypes to ensure the models are able to capture the general behaviors of the system. Additionally, gradient-based control algorithms are presented and applied to simulated and experimental systems to have each of them form arbitrary shapes, morph between shapes, grasp arbitrarily shaped objects, and navigate narrow corridors. All of these objectives have been accomplished in previous systems, however, this thesis will demonstrate this system is one of the first to be able to accomplish all four. Moreover, it is able to by using a single control framework. In addition, this thesis will present the application distance functions, R-functions, and space-time transfinite interpolation for control purposes. These techniques are commonly utilized in graphics and animation theory, and will be applied to gradient-based controllers. These controllers will be used for boundary constrained granular swarms to form desired shapes and morph between shapes in both 2D and 3D simulated systems and experimental systems. Moreover, this thesis will explore the use of grasping metrics for boundary-constrained granular swarms. The Ferrari Canny metric, a well-established tool for assessing grasp quality in robotic manipulators, is utilized to evaluate the system’s grasp performance. This thesis will also demonstrate the application of this metric for boundary-constrained swarms to find the optimal angle of approach for the system to grasp a target object.
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