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Modular Soft Robot Actuator Cells and the Patterns and Applications of Linear Actuator Buckling
thesisposted on 17.12.2021, 21:46 by Benjamin Lee HutchinsBenjamin Lee Hutchins
Soft robots allow for almost arbitrary continuous deformation by leveraging the nonlinear, large deformation of soft materials. However, this flexibility of possible motions comes often at the price of restricting a robot for a particular application. Efforts to create modular robots have emerged in recent years, but gaps remain. Here we design four different kinds of modular soft actuators, for bending, linear expansion, bilinear expansion, torsion, such that they all occupy the same 3×3×3in3volume and can be connected to each other to form arbitrary 3D assemblies by coupling to each other mechanically, pneumatically, and electronically. The actuators can be mechanically connected through magnets. Rather than connecting each actuator independently to a pneumatic line, coupling between adjacent actuators allows for a single pressure and vacuum line to run through an assembly, each actuator has its own controller and can be actuated independently by operating two valves which connect the internal chamber of each actuator to the central pressure and vacuum lines. All actuators are connected to the same central controller analogously to the pneumatic coupling. To optimize the designs and assemblies, finite element simulations were used to iterate designs before any fabrication took place. We showcase the modularity of our actuators in three applications: a walking robot, a claw actuator, and a balance plate.
Buckling is typically associated with something that occurs in hard materials and is thought of as undesirable, but with soft robotics, buckling can be leveraged to accomplish useful tasks. Buckling experiments involving 1D and 2D buckling as well as applications for the buckling of linear actuators are shown. Buckling patterns in 1D are modified by changing the number of actuators as well as the angles of the boundary condition. By changing the length of the actuator assembly, different buckling modes are observed. By modifying the angle of the fixed ends, different buckling patterns are forced as well. With this knowledge, several applications are demonstrated. A parallel robot is demonstrated that can cause rotation in either direction by modifying the angle at an end to force it to buckle in a certain way. Another application that is demonstrated is the ability to change the overall shape of an assembly by simply modifying the order in which actuation occurs. This demonstrates how something that is typically associated with mechanical failure, buckling, can be used advantageously with soft robotics. Additionally, buckling is demonstrated that is analogous to biological systems.