A Kinetostatic Model for Concentric Push-Pull Robots

Area of Science:

• Robotics
• Mechanical Engineering
• Applied Physics

Background:

• Concentric push-pull robots (CPPRs) utilize nested, laser-cut tubes with offset stiffness centers for actuation.
• Existing CPPR kinematic models are limited, assuming only two tubes, planar configurations, and neglecting torsion and external loads.
• These limitations hinder the development and application of more complex CPPR designs.

Purpose of the Study:

• To develop a generalized kinetostatic model for concentric push-pull robots (CPPRs).
• The new model accounts for an arbitrary number of tubes, variable curvature, 3D shapes, torsion, and external loads.
• To enable advanced design, planning, and control of CPPRs.

Main Methods:

• Employed a modified Kirchhoff rod model for each nested tube, incorporating offset stiffness centers.
• Integrated constraints to maintain concentricity between the tubes.
• Utilized an energy method to derive the robot's shape based on actuation inputs and external forces.

Main Results:

• Developed and validated a novel, generalized kinetostatic model for CPPRs.
• Experimental results with two- and three-tube prototypes, featuring variable stiffness and curvature, showed strong agreement with the model.
• The model accurately predicts the 3D shape of CPPRs under various conditions, including torsion and external loading.

Conclusions:

• The developed generalized kinetostatic model significantly advances CPPR capabilities.
• This model provides a foundation for optimizing CPPR design, improving motion planning, and enhancing control strategies.
• It paves the way for more sophisticated and versatile applications of concentric push-pull robots.