“Creating dynamical robots of different morphologies and sizes through automatic origami design”
Abstract: Origami robots are machines whose morphologies and functions are created by folding locally flat sheets. This thesis makes three contributions to the design and fabrication of origami robots aimed at the development of an automated computational pipeline for the specification and construction of widely different morphologies and body sizes capable of highly dynamic operation. The initial contribution recruits recent advances in the design of compliant folded structures to build the first soft robots that exhibit highly dynamic behavior. Specifically, the proof-of-concept robots reported here achieve their juggling and hopping behaviors by actuating their origami springs as power-cascading devices. Second, this thesis advances the origami design literature by automating the construction of compliant origami kinematic chains. The “Kinegami” algorithm reported here accepts a Denavit-Hartenberg kinematic specification and uses a catalog of tunably compliant origami modules to generate a crease pattern that folds into the prescribed serial robot mechanism. Finally, the thesis addresses the problem of scalability in general (not just origami) robot design by studying the simultaneous interaction of structural integrity and actuator affordance. Four contrasting abstract task domains impose different scaling criteria that reveal the relative advantages and disadvantages of three distinct structural principles combined with three different actuator types. For example, applying the unloaded dynamic task criterion to a direct drive actuation type reveals that the origami-style shell structure supports superior length scale-up. An accompanying empirical study confirms that structural alternatives cannot achieve a one-degree-of-freedom hopping task at the same five-fold scale-up of the original hopper design exhibited by the shell structure design. Considered in isolation, these contributions advance, respectively, the recent soft robotics literature, the older origami design literature, and the traditional engineering scaling literature. Considered together, they advance the agenda for the rapid, computer-assisted design of customized, high-performance robots.
Abstract: In this work, we consider the problem of controlling the end effector position of a continuum manipulator through local stiffness changes. Continuum manipulators offer the advantage of continuous deformation along their lengths, and recent advances in smart material actuators further enable local compliance changes, which can affect the manipulator’s bulk motion. However, leveraging local stiffness change to control motion remains lightly explored. We build a kinematic model of a continuum manipulator as a sequence of segments consisting of symmetrically arranged springs around the perimeter of every segment, and we show that this system has a closed form solution to its forward kinematics. The model includes common constraints such as restriction of torsional or shearing movement. Based on this model, we propose a controller on the spring stiffnesses for a single segment and provide provable guarantees on convergence to a desired goal position. The results are verified in simulation and compared to physical hardware.
Abstract: Repeated jumping is crucial to the mobility of jumping robots. In this paper, we extend upon the REBOund jumping robot design, an origami-inspired jumping robot that uses the Reconfigurable Expanding Bistable Origami (REBO) pattern as its body. The robot design takes advantage of the pattern’s bistability to jump with controllable timing. For jump repeatedly, we also add self-righting legs that utilize a single motor actuation mechanism. We describe a dynamic model that captures the compression of the REBO pattern and the REBOund self-righting process and compared it to the physical robot. Our experiments show that the REBOund is able to successfully self-right and jump repeatedly over tens of jumps.
Abstract: Modular and truss robots offer the potential of high reconfigurability and great functional flexibility, but common implementations relying on rigid components often lead to highly complex actuation and control requirements. This paper introduces a new type of modular, compliant robot: TrussBot. TrussBot is composed of 3D-printed tetrahedral modules connected at the corners with compliant joints. We propose a truss geometry, analyze its deformation modes, and provide a simulation framework for predicting its behavior under applied loads and actuation. The TrussBot is geometrically constrained, thus requiring compliant joints to move. The TrussBot can be actuated through a network of tendons which pinch vertices together and apply a twisting motion due to the structure’s connectivity. The truss was demonstrated in a physical prototype and compared to simulation results.