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The paper aims to propose a novel dual-stage shape memory alloy (SMA) actuated gripper (DAG), of which the grasp performance is improved through primary and secondary actuation.

This paper presents a method of integrating the design of dual-stage actuation modules based on the SMA bias actuation principle to enhance the grasping shape adaptability and force modulation of a DAG. The actuation angle range and grasping performance of the DAG are investigated by thermomechanical analysis and the finite element method based numerical simulation.

The results of present experiments and simulations indicate that the actuation angle scope of the DAG is about 20° under no load, which enables the grasping space occupied by an object in the DAG from 60 mm to 120 mm. The grasping force adjusted by changing the input power of the primary main actuation module and secondary fine-tuning actuation module can reach a maximum of 2 N, which is capable of grasping objects of various sizes, weights, shapes, etc.

The contribution of this paper is to design a DAG based on SMA, and establish the solution methods for the primary main actuation module and secondary fine-tuning actuation module, respectively. It lays a foundation for the research of lightweight and intelligent robotic grippers.

Recent development of wireless communication devices dictates that miniaturization, multi-functions and high integration are the important factors for antenna structures. This has resulted in the requirement of antennas with dual or multi-frequency operations. Although the dual-band antennas can be achieved through the experience-based configuration selection with the parameter adjustment, it is still a challenging problem to design an antenna with specific dual-frequency operations effectively. The purpose of the paper is to develop an effective design method to guide the design of antennas with specific dual-frequency operations.

The topology optimization is carried out through the material distribution approach, where the patch of the antenna is taken as the design domain. The optimization formulation is established with maximizing the minimum antenna efficiency at the target frequencies. The sensitivity of the antenna efficiency with the design variables is derived, and the optimization problem is solved by a gradient-based algorithm.

Based on the proposed design method, an example of a patch antenna design for specific dual-frequency operations is presented. The performance of the designed antenna is cross-verified by experimentation, where the reflection coefficients (S₁₁) obtained by simulation and experiment show a good agreement. The simulation and the experimentation of the designed antenna show that two operational bands are optimized to occur around the target frequencies, which confirms the effectiveness of the proposed design method.

This paper presents a topology optimization-based design method for patch antennas operating at dual specific frequencies.