Recent Patents on Mechanical Engineering - Volume 17, Issue 3, 2024

Aims: This study aims to analyze the accuracy of single- and double-diode models in predicting the electrical parameters of InGaP/InGaAs/Ge triple-junction solar cells as described in relevant patents under various operating conditions. Methods: This study obtained and analyzed experimental and theoretical values of the relevant electrical parameters of solar cells through a combination of experimental research and theoretical model calculations. Results: The results indicated that the root mean square error of the short-circuit current decreased from 0.21 at 400 W/m² to 0.11 at 1000 W/m². The temperature of the two precision cut-off points for the open-circuit voltage in the single- and double-diode models increased from 34°C and 64°C at 400 W/m² to 39°C and 72°C at 1000 W/m². Additionally, for peak power and conversion efficiency, the precision cut-off temperatures of the single- and double-diode models were 56°C, 68°C, and 77°C at 400 W/m², 600 W/m², and 800 W/m², respectively. Conclusion: The theoretical values of the short-circuit current exceeded the corresponding experimental values. The single- and double-diode models for open-circuit voltage exhibited two accuracy cut-off points, with the single-diode model demonstrating greater accuracy within this temperature range. Similarly, the peak power and conversion efficiency models for single- and double-diodes have an accuracy cut-off point, with the double-diode model performing better at higher temperatures.

Background: A high percentage of renewable energy and a high percentage of power electronic devices are connected to the power system, which leads to the diversification and complexity of stochastic excitation, and the traditional single-excitation stochastic model is no longer applicable. Objective: The study aimed to solve the problem that the high proportion of renewable energy and the high proportion of power electronic equipment are connected to the power system, which leads to the diversification and complexity of stochastic excitation and makes the traditional stochastic model of single excitation no longer applicable. Methods: Firstly, stochastic differential equations for power systems have been modelled with mixed Gaussian white noise and Poisson white noise excitation. Secondly, the Milstein-Euler predictor-corrector method has been developed to solve the stochastic differential equation model of the power system. Finally, the influence of Gauss white noise and Poisson white noise on the power system stability under different excitation intensities has been analyzed. The rationality and correctness of the model have been verified by the simulation of a one-machine infinitebus (OMIB) system. Results: The stochastic differential equation model of a power system with Gauss white noise and Poisson white noise excitation has been established and its angle stability has been analyzed. Increasing the Gaussian white noise and Poisson white noise excitation intensity can lead to an increase in the fluctuation of the power angle curve, as well as an increase in the standard deviation and expected value of the power angle mean curve, which may decrease the stability of the power system. Conclusion: This study provides a reference for stochastic power systems modeling and efficient simulation, and has important application value for power system stability assessment and safety evaluation as well as related patent applications.

Background: The primary objective of this study is to assess the impact of welding conditions on the mechanical properties of friction stir-welded butt joints created from two distinct aluminium alloys, namely, AA6061 and AA7075. Friction stir welding (FSW), known for its innovation and low-energy solid-state bonding technique, was employed in this research. Methods: FSW experiments were carried out on both AA6061 and AA7075 alloys using a computer numerical control (CNC) machine. The selection and design of the tool geometry were meticulous, with an emphasis on new pin profiles that are nearly flat at the weld contact point. Precisely, four distinct tool geometries were machined from HC-HCr (High carbon, high chromium steel): Circular, Square, Tapered third, and Triangular. Critical process variables that significantly influence weld quality include rotation speed (800 rpm-1400 rpm) and traverse speed (12 to 25 mm/min). These variables were carefully optimized to achieve flawless welds. During the friction stir welding process, the nugget zone undergoes significant deformation, leading to the formation of a new microstructure that substantially impacts the mechanical properties of the joint. Results: This study comprehensively investigates the thermal and mechanical properties of friction stir welding using aluminium alloys AA6061 and AA7075, considering various tool shapes. Among the four tool shapes employed, two were found to yield higher hardness values (referred to as BH). Notably, the square-shaped tool produced the highest temperature, reaching up to 690ºC, as determined by thermocouple readings. Based on the findings, the optimal FSW parameters for enhancing hardness involve an axial feed and spindle speed of 800 rpm combined with a feed rate of 15 mm/min. These parameters were identified as crucial for achieving the desired mechanical properties in the friction stir-welded joints. Conclusion: This study presents new developments in FSW technology, which may have patent implications.

Temperature is crucial for battery pack durability and power. Folded fin and serpentine channel cooling methods are mostly used to cool the pack. However, fluid absorption during cooling can reduce capacity and cause downstream temperatures to be higher than upstream. Consistent cooling is vital to prevent temperature variation and increase battery pack lifespan. This work is concerned with the computational study of heat dissipation from open-cell aluminium metal foam for cooling LiFePO4 battery packs. The battery module consists of six pieces of pouch cell and three pieces of the aluminium foam heat sink. In the present study, aluminium foams are positioned between the LiFePO4 battery modules that are arranged in a vertical manner. Thermal interaction between the battery module and aluminum foam was studied. The effect of pore density on heat dissipation performance at different mass flow rates was explored. It has been discovered that aluminium foam with suitable porosity and pore density can efficiently cool the LiFePO4 battery pack. This paper provides a theoretical framework for designing a thermal management system for lithium- ion batteries using aluminium foam. Background: Metal foam cooling is an established technique for thermal management of Lithiumion batteries in electric vehicles. Objective: The present study aims to analyze heat transfer through aluminium metal foams for vertically aligned LiFePO4 battery pack cooling. Methods: The Darcy extended Forchheimer (DEF) model examines fluid flow through metallic foams, using the local thermal non-equilibrium model to determine heat transfer. Results: The impact of the density of pores in the aluminium foam on the average wall temperature and temperature difference along the battery surface is determined. The variation of heat transfer of lithium-ion battery modules for different mass flow rates is also studied. Conclusion: The results indicate that utilizing aluminium foam as a heat transfer medium for battery modules significantly enhances their thermal management performance.

Background: The condition that vehicles are prone to skidding during emergency lane changing, an anti-rollover constraint is added to the trajectory planning. Methods: The evaluation index is constructed by the lateral load transfer rate LTR, so as to put forward a seventh-order polynomial trajectory planning method considering the anti-rollover. It improves the safety and stability of the planned trajectory of the intelligent vehicle when changing lanes in an emergency. The risk assessment index under different emergency lane changing modes is obtained through simulation tests, the phase plane method is used to classify the risk level and formulate a reasonable risk decision-making mechanism. A patented model for risk assessment considering the risk of instability is designed. Results: The tests conducted on a low-friction road show that when the risk assessment factor is in the range of the steering lane change mode intervals, the steering controller maneuvers the vehicle to make an emergency lane change with a seventh-order polynomial trajectory. Conclusion: The small fluctuation of the LTR verifies the feasibility of the model.

Background: Patient Transfer Apparatus (PTA), which has been reported by various relevant papers and patents, is widely used in the hospital. However, there are few corresponding transfer apparatuses for research and development in the nuclear magnetic resonance imaging (MRI) room because of the influence of a high magnetic field environment. It is desired to require the apparatus for the patient and the medical staff to have weak magnetism, high matching, and easy operation, etc. Objective: The purpose of this study is to find out the working principle of PTA, to conduct parameter optimization and design and develop more effective PTA for the application of the MRI room. Methods: Firstly, based on the patient transfer process, a novel transfer model with the coordinated movement of the transfer belt and the moving panel is proposed, the corresponding clutch mechanism is conceived and the working principle of the whole mechanism movement is designed and analyzed in detail. Secondly, the force analysis of the clutch mechanism, lifting mechanism and patient transfer mechanism are performed, the mechanical structures are optimized, and the optimal sizes are obtained. Thirdly, the mechanical structure of the system is designed in detail, and the prototype is manufactured. Results: Finally, the performance evaluation of the system is conducted by means of the fuzzy evaluation method and clinical study. The results showed that the motion function of the apparatus is reasonable and it can work normally in the MRI room, the comfort of the PTA is also excellent. The research results also prove the accuracy of the working principle and the rationality of the structural design. Conclusion: The non-magnetic PTA is suitable for quickly transferring patients who are unable to move in the MRI room of a hospital by the manual method.