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US-12623340-B2 - Device and method of fabrication for dexterous continuum tensegrity manipulator

US12623340B2US 12623340 B2US12623340 B2US 12623340B2US-12623340-B2

Abstract

A continuum manipulator that comprises an assembly of ‘vertebra’-like modules fabricated using two curved links and twelve strings and actuated using Motor-Tendon Actuators. The modules being modeled as tensegrity structures having a polyhedron shape. The vertices and edges of the tensegrity structure polyhedron correspond to the holes and strings or links of the structure. Furthermore, a mobile continuum manipulator that includes a control unit and wheels or mobile legs.

Inventors

  • Vishesh Vikas
  • Cole Woods

Assignees

  • THE BOARD OF TRUSTEES OF THE UNIVERSITY OF ALABAMA

Dates

Publication Date
20260512
Application Date
20240122

Claims (20)

  1. 1 . A manipulator comprising a plurality of modules interlocked to form a linear arrangement of modules, wherein a module comprises: two rigid elements each defining a plurality of connection holes, wherein the two rigid elements do not touch, wherein each of the two rigid elements comprises an assembly connector, whereby the plurality of modules are coupled by interlocking assembly connectors of respective modules; and a single continuous string or cord routed through the plurality of connection holes of the two rigid elements to form a plurality of tension-compliant elements extending between the two rigid elements.
  2. 2 . The manipulator of claim 1 , wherein at least one of the two rigid elements comprises a two-dimensional shape forming a half-circle and the assembly connector is oriented radially.
  3. 3 . The manipulator of claim 1 , wherein the single continuous string or cord is a prestressed string or cord.
  4. 4 . The manipulator of claim 1 , wherein the module comprises a polyhedron shape, wherein edges and vertices of the polyhedron shape are formed by the plurality of tension-compliant elements and the plurality of connection holes of the two rigid elements.
  5. 5 . The manipulator of claim 1 , wherein the plurality of modules are rigidly coupled by interlocking the assembly connector of respective modules.
  6. 6 . The manipulator of claim 1 , wherein the plurality of tension-compliant elements are secured to the two rigid elements with a rigid assembly, wherein the rigid assembly prevents movement between a tension compliant element and a rigid element.
  7. 7 . The manipulator of claim 1 , wherein the module further comprises a first tendon connector and a second tendon connector each oriented radially and equally spaced on either side of the assembly connector, the first and second tendon connectors each comprising a tendon attachment, wherein each tendon attachment comprises a hole through which a tendon is positioned.
  8. 8 . The manipulator of claim 7 , further comprising a plurality of actuators positioned at a proximal end of the manipulator, a plurality of tendons connecting the plurality of actuators and the plurality of modules, and a means for gripping at a distal end of the manipulator, wherein a number of tendons and number of actuators are the same.
  9. 9 . The manipulator of claim 8 , wherein the plurality of actuators comprises motor-tendon actuators.
  10. 10 . The manipulator of claim 8 , comprising ten modules, four tendons, and four actuators, wherein each module comprises twelve tension-compliant elements formed by the single continuous string or cord and four holes in each of the two rigid elements.
  11. 11 . A device comprising a plurality of manipulators of claim 10 .
  12. 12 . The device of claim 11 , further comprising a base plate, wherein the base plate is positioned above the plurality of actuators and below a first module from the proximal end of the plurality of manipulators.
  13. 13 . The device of claim 11 , further comprising a base housing, wherein the base housing encases the plurality of actuators and a control unit, and wherein a plurality of wheels and mounts are coupled to the base housing.
  14. 14 . The manipulator of claim 8 , further comprising a base plate, wherein the base plate is positioned above the plurality of actuators and below a first module from the proximal end of the manipulator.
  15. 15 . The manipulator of claim 14 , further comprising a base housing, wherein the base housing encases the plurality of actuators, and a control unit.
  16. 16 . The manipulator of claim 15 , wherein a plurality of wheels or a plurality of mobile legs are coupled to the base housing.
  17. 17 . The manipulator of claim 8 , wherein one or more sensors are coupled to the modules of the manipulator.
  18. 18 . The manipulator of claim 1 , wherein the two rigid elements of the module comprises a first rigid element and a second rigid element oriented at a 90-degree angle to the first rigid element relative to a longitudinal axis of the linear arrangement of modules.
  19. 19 . The manipulator of claim 1 , wherein the module is a first module comprising a first rigid element and a second rigid element, wherein the assembly connector of the first rigid element projects from the first rigid element to interlock and overlap with at least a portion of an assembly connector of a third rigid element of a second module.
  20. 20 . The manipulator of claim 1 , further comprising one or more pinch points disposed in at least one of the plurality of connection holes, the one or more pinch points being adjustable to adjust tension in the single continuous string or cord.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This patent application claims priority to, and the benefit of, U.S. provisional application, U.S. 63/440,213, filed on Jan. 20, 2023, which is hereby incorporated by reference herein in its entirety. ACKNOWLEDGEMENT OF GOVERNMENT SUPPORT This invention was made with government support under grant no. 1832993 awarded by the National Science Foundation. The government has certain rights in the invention. TECHNICAL FIELD The disclosure generally relates to mechanical devices comprising tension and compression elements and methods related thereto. BACKGROUND Tensegrity mechanisms synergistically combine tension elements (pre-stressed cables) with compression elements (rigid rods) to achieve structural integrity. This concept is prevalent from the model of the universe where the compression elements (heavenly bodies) are floating in a sea of tension (gravitational force) to micro-scale biological organisms (Ingber, D. E., 1993. “Cellular tensegrity: defining new rules of biological design that govern the cytoskeleton”. J. Cell Sci. 104(3):613-627). From an engineering perspective, these mechanisms are packable, portable, internally stable (i.e., do not require gravity for maintaining structural integrity), and possess high strength-to-weight ratios (Connelly, R., 2002. “Tensegrity structures: why are they stable?”. In Rigidity theory and applications. Springer, pp. 47-54; Skelton, R. E., et al., 2016. “Globally stable minimal mass compressive tensegrity structures”. Composite Structures, 141, pp. 346-354). This makes them ideal for applications relating to space, bio-mechanical modeling and robotic manipulation. These advantages can be viewed as a result of the strategic interaction between the tension-compression elements that preserves the structural integrity of the mechanism. However, this combination of the two antagonistic members poses design and modeling challenges. Complex tensegrity systems result from assembly of smaller, fundamental primitive units or tensegrity modules. For example, Ikemoto et al. (2021. “Development of a modular tensegrity robot arm capable of continuous bending”. Frontiers in Robotics and AI, 8, 11) made a modular tensegrity robot arm that comprised of five modules of four link tensegrity prisms that used twenty pneumatic cylinders to actuate each rigid member; Ramadoss et al. (2022. “Hedra: A bioinspired modular tensegrity robot with polyhedral parallel modules”. In 2022 IEEE 5th International Conference on Soft Robotics (RoboSoft), pp. 559-564), a modular tensegrity arm that has five modules and used three cables to move the arm; Sabelhaus et al. (2018. “Design, simulation, and testing of a flexible actuated spine r quadruped robots”. arXiv, Sabelhaus, A. P., et al., 2015. “Mechanism design and simulation of the ultra spine: a tensegrity robot”. In International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Vol. 57120, American Society of Mechanical Engineers, p. V05AT08A059) a spine for a quadruped with five vertebrae, three of which were active and change the length of cables using motors; Zappeti et al. (2017. “Bio-inspired tensegrity soft modular robots”. In Conference on Biomimetic and Biohybrid Systems, Springer, pp. 497-508), an icosahedron modular robot that had three modules. Here, all the modular tensegrity robots use node-to-cable connections between consecutive modules, except for Zeppettii et al., where the authors use node-to-node approach to connect the triangular face of consecutive icosahedrons. The use of node-to-node connections when applicable, has potential to tremendously simplify the design. Despite interest in tensegrity mechanisms since their conception by Buckminster Fuller in the 1960s, their fabrication methodology remains minimally discussed in literature given its arduous nature. It is further complicated with integration of actuators. For example, Ikemoto, S., et al., Ramadoss, V. et al., Sabelhaus, A. P., 2018, Sabelhaus, A. P., 2025, and Fasquelle, B., e al. (2020. “A bioinspired 3-dof light-weight manipulator with tensegrity x-joints*”. p. 5054-5060) all fabricated tensegrity spine-like structures, however, only (Ramadoss, V. et al.) has less actuators than the total number of modules. From the perspective of design, systems with less number of actuators are easier to fabricate. Increasing the number of actuators potentially provides more controllability over the system, e.g., variation in stiffness and shape change. However, this comes at the cost of complexity in design and control (computation power and algorithm). Passively, Zappetti et al. (2020. “Variable-stiffness tensegrity spine”. p. 075013) fabricated a tensegrity spine with variable stiffness. Rhodes et al. (2019. “Compact Shape Morphing Tensegrity Robots Capable of Locomotion”. Frontiers in Robotics and AI, 6) fabricated a tensegrity robot that could change its shape. Kobayashi et al. (2022.