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.

Design and Performance Evaluation of a Spherical Robot Assisted by High-Speed Rotating Flywheels for Self-Stabilization and Obstacle Surmounting

Abstract

In order to reinforce the operation stability and obstacle capability of a spherical robot, this paper presents a spherical robot with high-speed rotating flywheel, the mechanical structure of which is mainly composed of a spherical shell, a double pendulum on both sides and two high-speed flywheels. The robot has three excitation modes: level running, self-stability operating, and obstacle surmounting. The dynamic characteristics of the pendulum, flywheel, and brake of the robot are discussed through the establishment of kinematic and dynamic model of the spherical robot and the influence of parameters like weight, flywheel speed. and flywheel position on its dynamic characteristics and robot performance is optimized and analyzed in detail. The research results indicate that the two flywheels located in the center of the sphere apart can bring maximum stability gain to the sphere. Finally, the simulation and experiment of the stability gain brought by the high-speed flywheel to the sphere verify that the operation stability of the sphere is effectively improved after using the flywheel, and the robot that stops the flywheel through a brake fixed on the pendulum has better obstacle surmounting performance.
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