Aiming at the existing picking manipulator's fingers are primarily integrated with rigid materials, which have the problem of poor flexibility and self-adaptability, this study designs a multi-chamber soft picking manipulator for tomato picking. The structural model of the soft body picking manipulator is established, and the mathematical model of the single chamber is constructed using the strain energy density function, the principle of virtual work and the volume solution method, otherwise, it is concluded that the pressure in the finger chamber is positively correlated with the bending angle in the material’s limit range. Yeoh’s third order and control variable method are used in workbench finite element simulation to simulate and analyze the finger’s structure model. The simulation results demonstrate the ideal combinations of parameters for the finger: 6 chambers, the chamber spacing is 6mm and the chamber wall thickness is 3mm; The fingers intracavity pressure can pick tomatoes when the minimum pressure is 0.03MPa, and it can pick fruits similar to the shape of the tomato. Additionally the soft picking robot model has some degree of universality, providing new models and parameters for fruit and vegetable picking robots.
Simulations of terahertz signals in the time or frequency domain focus on the photoconductive antenna (PCA). However, they lack a simpler and more accurate simulation technology for PCA, which plays a crucial role in designing and optimizing detectors. Such work is essential in terahertz imaging and time-domain spectroscopy (THz-TDS). This work simulates an incident terahertz wave by introducing a three-dimensional (3-D) finite-difference time-domain (FDTD) simulation in the form of a total field to scattering field. This wave is pretreated as a plane wave that is incident on the receiver. The equation of carrier dynamics with semiconductor charge and transport is solved by using the 3-D full-wave FDTD method. A center surface current method is used to calculate the time-varying conductivity. A sampling electric field was used to evaluate the photocurrent. They were obtained by convolving the main time-varying photoconductivity of the photoexcited carrier distribution on the cross-section in the middle of the gap of a PCA receiver. Then, we compare these simulations with previously reported data from an incident terahertz signal. In addition, we simulated the detection characteristics with other results in the literature. Our simulation tool can accurately reproduce these data sets. These simulations can be used to design and optimize the receiving performance of different PCAs structures before costly fabrication has commenced.
In order to obtain the terahertz detection signal as accurately as possible, a numerical simulation tool for terahertz signal reception is developed in this paper. The numerical simulation tool with the full-wave finite-difference time-domain (FDTD) method in three dimensions (3D) that couple multi-physics together is capable of getting the Terahertz detection signals. The carrier distribution effect of the incident femtosecond laser interacting with terahertz on the detector is analyzed briefly, and the simulation tool is validated by comparing the incident terahertz signal with the detected terahertz signal by using the low temperature growth GaAs substrate. The results show that the simulation tool developed in this paper is of great significance to the terahertz detection of micro-structure photoconductive antenna.
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