For the application of parallel robots in the grinding industry, a parallel robot equipped with a constant force actuator that produces a constant force for grinding is designed. To study the ...characteristics of the parallel robot’s spatial positions and poses, the inverse solutions of the moving platform’s spatial positions and poses as well as the workspace where objects were ground were established by using DH parameters and geometric methods. The experimental results showed that the workspace where objects were ground was a cylinder with a cross section similar to a symmetric circular sector. To analyze the characteristics of the forces produced by the parallel robotic system, the dynamics equation was established via the Newton–Euler method to verify the rationality of the force decoupling design. Theoretical calculation combined with simulation and experimental analyses confirmed the viability of the theoretical analyses which lay a theoretical foundation for the design, manufacture and control of the parallel robotic system proposed in this paper.
•Sonication elevated taste compounds of soy sauce and lowered its NaCl content.•Sonication improved sensory quality of soy sauce and accelerated its maturation.•Sonication enhanced enzyme activities ...and reaction sites of moromi.
Sonication can significantly enhance amino acids (AAs) release to accelerate maturation during short-term and low-salt soy sauce fermentation. Here, sonication was applied at 68 kHz (60 W/L/10 min/8 circles) to determine its effects on the taste during long-term and high-salt soy sauce fermentation. The possible mechanisms were explored by analyzing differences in enzymes profile, proximate indices, molecular weight distribution of peptides, AAs composition and microstructures of sonicated moromis and their controls. Sonication greatly elevated levels of organic taste compounds ranging from 8.4% to 22.2%, but lowered levels of NaCl (6.0%), peptides ≤ 1 kDa (5.2%), histidine (20.5%) and glutamic acid (3.4%). Compared to its controls, sonicated raw soy sauces also had a more harmonious and palatable taste. Increased enzymes’ activities and formation of more surface area and reaction sites in sonicated moromis might be the possible mechanisms for sonication to elevate levels of taste compounds and sensory quality of soy sauce.
To elucidate the effects of sonication on the antioxidant activities of compounds in soy sauce, sonication at 68 kHz (60 W/L/10 min/8 circles) was employed during moromi fermentation. Sonication ...enhanced four antioxidant indices of soy sauce from 5.29% to 24.29%, which were attributed to the significantly higher levels of free amino acids (FAAs, 12.45%), total phenolics (26.71%) and 1–3 kDa peptides (12.28%) in sonicated moromi. Amongst them, FAAs contributed 65.88% and 53.45% to the enhanced metal ion chelating activity and DPPH radical scavenging activity (p < 0.05), respectively. However, Maillard reaction products and isoflavones contributed little to the enhanced antioxidant activities, because sonication slightly affected Maillard reaction products, isoflavones and β-glucosidase activities during moromi fermentation. It was concluded that cell wall of soybean was destroyed by sonication, facilitating the release of antioxidant compounds, which significantly enhanced the antioxidant activities in raw soy sauce.
•Sonication significantly facilitated antioxidant compounds release.•Sonication remarkably improved antioxidant activities of soy sauce.•FAAs, phenolics, 1–3 kDa peptides increase led to antioxidant activities improvement.
An algorithm for automatically planning trajectories designed for painting large objects is proposed in this paper to eliminate the difficulty of painting large objects and ensure their surface ...quality. The algorithm was divided into three phases, comprising the target point acquisition phase, the trajectory planning phase, and the UR5 robot inverse solution acquisition phase. In the target point acquisition phase, the standard triangle language (STL) file, algorithm of principal component analyses (PCA), and k-dimensional tree (k-d tree) were employed to obtain the point cloud model of the car roof to be painted. Simultaneously, the point cloud data were compressed as per the requirements of the painting process. In the trajectory planning phase, combined with the maximum operating space of the UR5 robot, the painting trajectory of the target points was converted into multiple traveling salesman problem (TSP) models, and each TSP model was created with a genetic algorithm (GA). In the last phase, in conformity with the singularities of the UR5 robot’s motion space, the painting trajectory was divided into a recommended area trajectory and a non-recommended area trajectory and created by the analytical method and sequential quadratic programming (SQP). Finally, the proposed algorithm for painting large objects was deployed in a simulation experiment. Simulation results showed that the accuracy of the algorithm could meet the requirements of painting technology, and it has promising engineering practicability.
Honeycomb core sandwich plates are widely used as a lightweight, high-strength sound insulation material. However, they do not perform well in specific frequency bands. Acoustic metamaterials can ...break the law of mass in specific frequency bands and have high sound transmission loss (STL); however, the resonance frequency is difficult to regulate. To solve this problem, this paper first proposes an infinitely large metamaterial honeycomb core sandwich plate, which can generate newly tuned piezoelectric resonance frequencies, and we study its STL. The structure has piezoelectric patches arranged in sub-wavelength arrays with inductance shunting circuits that are elastically connected to both sides of the honeycomb core sandwich plate. The effective dynamic mass density and effective dynamic bending stiffness of the metamaterial plates were obtained using the effective medium (EM) method. A theoretical model for the numerical calculation of oblique STL and diffuse-field STL was established by the structural bending wave method. The finite element simulation method was used to verify that the metamaterial plates can generate three peaks at 1147 Hz, 1481 Hz and 1849 Hz in oblique or diffuse-field STL curves, which reached 57 dB, 86 dB and 63 dB, respectively, and are significantly better than the plate rigidly connected with piezoelectric sheets and the bare plate with the same mass. In order to better understand the characteristics of STL, the explicit functions of the resonance frequencies were derived. Key influencing factors were analyzed, and the regulation law of new piezoelectric resonance frequencies was clarified.
The measurement accuracy of a magnetic gradiometer relies on magnetometer consistency, measurement accuracy, and assembly technology. The traditional methods calibrate measurement error, misalignment ...error, and the interference magnetic field independently. However, after a long time of work, the calibration parameters will inevitably change. Furthermore, it will waste a lot of manpower and material resources if the magnetic gradiometer is disassembled and calibrated step by step. Given the above problems, a novel attitude-independent calibration algorithm using a limited number of measurement points is proposed, which can effectively overcome the measurement distortion of the magnetic gradiometer and does not rely on a reference magnetometer. For the cross-shaped magnetic gradiometer, the simulation results show that the error after integrated calibration is reduced to less than 8% of the error before calibration. The test results suggest that the magnetic gradient results before calibration are even up to 1.5 µT/m, whereas the magnetic gradient results after the integrated calibration are less than 100 nT/m.
Multi-loop spherical mechanisms are extremely beneficial for creating versatile mechanical devices, including robotic joints and surgical tools, since multi-loop spherical mechanisms possess unique ...capabilities to operate in spatial situations with relatively simple movement. Nevertheless, the research on multi-loop spherical mechanisms with spherical sliders containing spherical prismatic pairs is lacking. Therefore, the main innovation of this paper is to propose the Stephenson-III two-loop spherical mechanism that possesses a spherical slider containing a spherical prismatic pair and to analyze the proposed spherical mechanism’s motion characteristics. An algebraic approach was employed to obtain the branch graphs of the proposed spherical mechanism with a spherical slider. The branch graphs were categorized into two types, according to whether branch points existed. With the algebraic approach, loop equations of the two spherical kinematic chains inside the proposed spherical mechanism were established to identify the input–output curves and singularity curves, with which the branch graphs were obtained. With the branch graphs, the joint rotation spaces (JRSs) of the proposed mechanism were recognized and so were the dead center positions, branches, sub-branches, and branch points. The results from the mathematical analysis were simulated and verified by three-dimensional (3D) models of the proposed spherical mechanism. The analytical results demonstrate that the spherical prismatic pair diversifies the motion of the proposed spherical mechanism by producing rotational sliding movement, which can cover the entire circumference of a specific greater circle on the proposed mechanism’s sphere.
This paper considers exponential convergence for a class of high-order recurrent neural networks (HRNNs) with continuously distributed delays in the leakage terms (i.e., “leakage delays”). Without ...assuming the boundedness on the activation functions, some sufficient conditions are derived to ensure that all solutions of this system converge exponentially to zero point by using Lyapunov functional method and differential inequality techniques, which are new and complement previously known results. In particular, we propose a new approach to prove the exponential convergence of HRNNs with continuously distributed delays in the leakage terms. Moreover, an example is given to show the effectiveness of the proposed method and results.
Active control is currently a hot-button issue in the research of reducing vibration and noise created by rolling piston compressors. Active control can effectively suppress the modal vibration of ...the structure and reduce the modal resonance acoustic radiation. This paper, which focuses on the active control of the compressor shell’s multiple modes with the control of acoustic radiation power being the research objective, studies the relationship between vibration modes and acoustic radiation modes of the compressor shell and the primary sources of noise. An improved Filtered-U least mean square (FULMS) algorithm for compressor vibration and noise control, which is based on the Nesterov accelerated adaptive moment estimation (NADAM) optimization algorithm, is proposed to determine the multi-order modes to be controlled from the perspective of sound energy, and a particle swarm algorithm is used to determine the location and number of secondary sources. The active control model of the compressor shell was established by using the joint simulation platform, and the performance of the improved algorithm was verified and analyzed by the simulation test process. The results show that compared with the traditional FULMS algorithm, the improved FULMS algorithm has better active vibration control effect, higher convergence speed and can effectively suppress structural mode vibration in a short period time.
Consider the neutral functional differential equation
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