Multistability Enabled Passive Multiplexing in an n-DOF, Underactuated Hyper-Redundant Robot
Cole Nagata, Jordan Raney, Mark Yim
AI summary
Problem
Miniaturized high-DOF robots are limited by bulky internal actuators and complex scaling, making it difficult to map many mechanical outputs to few inputs. This work addresses how to compactly control numerous joints with minimal hardware for scalable, constrained-environment applications.
Approach
Serially chain bistable rotary joints with progressively tuned maximum moments and route four tendons through them. Varying the moments creates a predetermined demultiplexing order, allowing tendon tension to passively switch joints one at a time for individual control.
Key results
- Designed and fabricated tunable bistable rotary joints with verified moment-angle behavior
- Demonstrated passive multiplexing and high positional accuracy on 4-link and 11-link prototypes
- Validated analytical and finite element models against physical bistable beam tests
- Quantified geometric relationships between link parameters and overall workspace radius via simulation
Why it matters
Enables highly miniaturizable, scalable serial robots for medical and inspection tasks by eliminating internal electronics and complex active switching mechanisms.
Abstract
New developments in robotics have allowed robots to become very small, and capable of completing tasks humans cannot. Current robots capable of achieving this are physically limited in how small they can be without compromising on other aspects such as sensing, strength, or complexity. Thus, we strive to understand how we can more compactly map complex mechanical outputs to a low number of mechanical inputs. This paper presents a novel design for a hyper-redundant robot, capable of passive multiplexing. This is achieved using bistable joints at each link, with each link having a different bistable moment in order to establish priority when multiplexing. In doing so, this simple mechanism is able to achieve individual joint control, and reach a variety of complex configurations. To demonstrate the proposed robot, we construct an eleven linked mechanism and four linked mechanism, in which we demonstrate multiplexing, as well as high positional accuracy. By simulating the mechanism, we also quantify a geometric relationship between individual links and the overall robot’s workspace.