Showing papers by "Benliang Zhu published in 2020"

Topology optimization of a cable-driven soft robotic gripper

Abstract: Improving the functionality of soft continuum manipulators to expand their application space has always been an important development direction for soft robotics. It remains very challenging to calculate the deformations of soft materials and predict the basic structure of soft fingers under complex objective functions and constraints. This work develops a cable-driven soft robotic gripper with multi-input and multi-output using topology optimization considering geometric nonlinearity, which not only performs adaptive grasping but also enables finer manipulations such as rotating or panning the target. A scheme that can describe adaptive grasping behavior is proposed, which converts the contact between the clamping surface and the object into a boundary condition to circumvent complex contact nonlinearities. An additive hyperelasticity technique is used to overcome numerical instabilities, and the finite element analysis is performed in ANSYS. Numerical simulations and experimental results are performed to demonstrate the effectiveness of the optimization algorithm and to illustrate the application potential of the proposed gripper.

Large-Deflection Analysis of General Beams in Contact-Aided Compliant Mechanisms Using Chained Pseudo-Rigid-Body Model

Abstract: The nonlinear analysis and design of contact-aided compliant mechanisms (CCMs) are challenging. This paper presents a nonlinear method for analyzing the deformation of general beams that contact rigid surfaces in CCMs. The large deflection of the general beam is modeled by using the chained pseudo-rigid-body model. A geometry constraint from the contact surface is developed to constrain the beam’s deformed configuration. The contact analysis problem is formulated based on the principle of minimum potential energy and solved using an optimization algorithm. Besides, a novel technique based on the principle of work and energy is proposed to calculate the reaction force/moment of displacement-loaded cases. Several analysis examples of the compliant mechanisms with straight or curved beams are used to verify the proposed method. The results show that the proposed method and technique can evaluate the deformation of beam-based CCMs and the reaction force/moment with acceptable accuracy, respectively.

An Improved Template-Matching-Based Pose Tracking Method for Planar Nanopositioning Stages Using Enhanced Correlation Coefficient

Abstract: In the development and application of planar nanopositioning stages (PNSs), there is an urgent need to measure pose quickly and accurately. An improved pose measurement method based on template matching that can track in-plane three degree-of-freedom (3-DOF) motion at small scale with high performance is presented in this paper. To achieve higher tracking accuracy and robustness, the problem of pose measurement is first transformed into an enhanced correlation coefficient (ECC) -based parametric image matching problem. Subsequently, an efficient 3-DOF tacking algorithm based on inverse compositional searching strategy is developed in which the update of Hessian matrix caused by the nonlinear warp is avoided to improve the tracking frame rate. A series of simulations and experiments are conducted to evaluate the performance of the proposed method. The results show that the use of ECC can effectively improve the tracking robustness and accuracy, especially for angular measurement, compared to the sum of square difference (SSD) criterion. Besides, the tracking frame rate can be improved by using the developed algorithm even though the correlation function is much more complicated. Finally, application of the proposed method on a nanorobotic system for automatic in-plane 3-DOF alignment is demonstrated.

Compliant joint having large stroke in planar composite structure space

Abstract: A compliant joint that has a large stroke in a planar composite structure space, comprising a rectangular planar unit (1) used for implementing an out-of-plane torsion function and a fork-shaped planar unit (2) used for implementing an in-plane rotation function, wherein the fork-shaped planar unit (2) is a fork-like structure that has an included angle into which two flexible straight beam sheets (201) intersect, and the rectangular planar unit (1) and the fork-shaped planar unit (2) are connected in an external or embedded manner. The present joint overcomes the problems in which existing planar structure compliant joints may only be equivalent to a single-degree-of-freedom large-stroke low-motion pair and existing LEMs compliant mechanisms are equivalent to multi-degree-of-freedom compliant joints that have smaller overall strokes, and has the advantages of a simple structure, easy processing, easy analysis and calculation, equivalent large stroke space and multiple degrees of freedom flexibility, and so on.