Latest Papers

ASME Journal of Mechanisms and Robotics

  • An Improved Dual Quaternion Dynamic Movement Primitives-Based Algorithm for Robot-Agnostic Learning and Execution of Throwing Tasks
    on May 9, 2025 at 12:00 am

    AbstractInspired by human nature, roboticists have conceived robots as tools meant to be flexible, capable of performing a wide variety of tasks. Learning from demonstration methods allow us to “teach” robots the way we would perform tasks, in a versatile and adaptive manner. Dynamic movement primitives (DMP) aims for learning complex behaviors in such a way, representing tasks as stable, well-understood dynamical systems. By modeling movements over the SE(3) group, modeled primitives can be generalized for any robotic manipulator capable of full end-effector 3D movement. In this article, we present a robot-agnostic formulation of discrete DMP based on the dual quaternion algebra, oriented to modeling throwing movements. We consider adapted initial and final poses and velocities, all computed from a projectile kinematic model and from the goal at which the projectile is aimed. Experimental demonstrations are carried out in both a simulated and a real environment. Results support the effectiveness of the improved method formulation.

  • Chained Timoshenko Beam Constraint Model With Applications in Large Deflection Analysis of Compliant Mechanism
    on May 9, 2025 at 12:00 am

    AbstractAccurately analyzing the large deformation behaviors of compliant mechanisms has always been a significant challenge in the design process. The classical Euler–Bernoulli beam theory serves as the primary theoretical basis for the large deformation analysis of compliant mechanisms. However, neglecting shear effects may reduce the accuracy of modeling compliant mechanisms. Inspired by the beam constraint model, this study takes a step further to develop a Timoshenko beam constraint model (TBCM) for initially curved beams to capture intermediate-range deflections under beam-end loading conditions. On this basis, the chained Timoshenko beam constraint model (CTBCM) is proposed for large deformation analysis and kinetostatic modeling of compliant mechanisms. The accuracy and feasibility of the proposed TBCM and CTBCM have been validated through modeling and analysis of curved beam mechanisms. Results indicate that TBCM and CTBCM are more accurate compared to the Euler beam constraint model (EBCM) and the chained Euler beam constraint model (CEBCM). Additionally, CTBCM has been found to offer computational advantages, as it requires fewer discrete elements to achieve convergence.

Increasing Mobile Robot Efficiency and Versatility Through Manipulation-Driven Adaptation 1

Abstract

Terrestrial mobile robotics are crucial to a range of missions including planetary exploration, search and rescue, logistics, and national security. Many of these missions require the robot to operate on a broad variety of terrain. Wheels are ideal for energy efficiency but can suffer catastrophic failure when presented with obstacles or complex ground. Legs can help traverse obstacles but at the cost of energy efficiency. Physical adaptation can enable a robot to benefit from both modes of locomotion. This article describes a new approach to physical adaptation through manipulation. Specifically, this article examines how manipulators can be used to change the vehicle’s mode of locomotion and improve energy efficiency and versatility. This article presents “swappable propulsors,” which can be easily attached/detached to adapt the vehicle through the use of permanent magnets. A new robot system that uses its manipulator to discretely switch between wheeled and legged locomotion is created. The experimental results demonstrate how this approach provides a unique combination of energy efficiency and versatility. This study describes the design of swappable propulsors, analyzes how to manipulate them, and describes how they can be used to improve performance. This study extends on prior work with additional analysis, an improved robot prototype, and new experimental results.
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