Latest Papers

ASME Journal of Mechanisms and Robotics

  • Investigation on a Class of 2D Profile Amplified Stroke Dielectric Elastomer Actuators
    on September 24, 2024 at 12:00 am

    AbstractDielectric elastomer actuators (DEAs) have been widely studied in soft robotics due to their muscle-like movements. Linear DEAs are typically tensioned using compression springs with positive stiffness or weights directly attached to the flexible film of the DEA. In this paper, a novel class of 2D profile linear DEAs (butterfly- and X-shaped linear DEAs) with compact structure is introduced, which, employing negative-stiffness mechanisms, can largely increase the stroke of the actuators. Then, a dynamic model of the proposed amplified-stroke linear DEAs (ASL-DEAs) is developed and used to predict the actuator stroke. The fabrication process of linear DEAs is presented. This, using compliant joints, 3D-printed links, and dielectric elastomer, allows for rapid and affordable production. The experimental validation of the butterfly- and X-shaped linear DEAs proved capable of increasing the stroke up to 32.7% and 24.0%, respectively, compared with the conventional design employing springs and constant weights. Finally, the dynamic model is validated against the experimental data of stroke amplitude and output force; errors smaller than 10.5% for a large stroke amplitude (60% of maximum stroke) and 10.5% on the output force are observed.

One-Step Solving the Hand–Eye Calibration by Dual Kronecker Product

Abstract

Hand–eye calibration is a typical research direction in robotics applications. The current methods can be divided into two categories according to whether the rotational and translational equations are decoupled for computation: two-step methods and one-step methods. Both one-step and two-step methods generally convert such problems to linear null space computations, which are implemented by the corresponding computational operators. Owing to the booming development of the rotation operators, the two-step methods have been more fully researched. However, due to the limitations of the research on computational operators integrating rotation and translation, the one-step methods still have much scope for research. Dual algebra, as effective mathematical entities for screws and wrenches, provides the theoretical basis for the development of the one-step methods for hand–eye calibration. In this paper, a computational operator for the dual matrices computation was first proposed, i.e., dual Kronecker product. Subsequently, a hand–eye calibration framework was proposed based on the dual Kronecker product, which allowed the screw motion to be represented as multiple dual vectors. Furthermore, the equivalence of this framework with the orthogonal-dual-tensor-based approach was derived, providing a more intuitive computational representation. The feasibility and superiority of the proposed computational framework were experimentally verified.

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