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A novel stiffness optimization model of space telescopic boom based on locking mechanism

Frontiers of Mechanical Engineering 2024年第3期19卷 41-59页

作者： Kun XU Xinghan ZHUANG Zhou SU Qiuhong LIN Shouzhi REN Hang XIAO Xilun DING School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Beijing Institute of Spacecraft System Engineering Beijing 100094China

The deployable telescopic boom,whose mass and stiffness play crucial roles,is extensively used in the design of space-deployable ***,the most existing optimal design that neglects the influence of the locking mechanisms in boom joints cannot raise the whole stiffness while reducing the boom *** tackle this challenge,a novel optimization model,which utilizes the arrangement of the locking mechanisms to achieve synchronous improvement of the stiffness and mass,is *** proposed optimization model incorporates a novel joint stiffness model developed based on an equivalent parallel mechanism that enables the consideration of multiple internal stiffness factors of the locking mechanisms and tubes,resulting in more accurate representations of the joint stiffness *** analysis shows that the proposed stiffness model achieves more than at least 11% improved accuracy compared with existing ***,case verification shows that the proposed optimization model can improve stiffness while effectively reducing mass,and it is applied in boom optimization design.

关键词： deployable telescopic boom locking mechanism stiffness model clearance error optimization model

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A calibration and compensation method for an industrial robot with high accuracy harmonic reducers

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Science China(Technological Sciences) 2024年第3期67卷 725-739页

作者： ZHAO YiYang LIU Xun CAO JiaBin LIU JinYu XU Yan YAN WeiXin School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China College of Computer and Control Engineering Northeast Forestry UniversityHarbin 150040China

Industrial serial robots need high stiffness to keep absolute pose accuracy and meet the requirements in practical applications. However, the weak stiffness feature of robot joints and the payloads affected on robot end-effector, which will also increase the pose error of robot. Especially, the existing calibration methods often consider under no-payload condition without discussing the payload state. In this paper, we report a new industrial serial robot composed by a new harmonic reducer: model-Y, based on high accuracy and high stiffness, and a kinematic parameter calibration algorithm which is based on a harmonic reducer forcedeformation model. To decrease the accuracy effects of payload, an iterative calibration method for kinematic parameters with payload situation was proposed. Simulation and experiments are conducted to verify the effectiveness of the proposed calibration method using the self-developed industrial serial robot. The results show a remarkably improved accuracy in absolute position and orientation with the robot's payload range. The position mean error has 70% decreased to 0.1 mm and the orientation mean error diminished to less than 0.01° after calibration with compensation. Additionally, online linear and circular tests are carried out to evaluate the position error of the robot during large-scale spatial and low-speed continuous movement. The accuracy is consistent with the previous calibration results, indicating the effectiveness and advantages of the proposed strategy in this article.

关键词： industrial serial robot model-Y harmonic calibration stiffness model online compensation

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Rice stem lodging properties and bending modeling under the influence of circadian temperature difference

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International Journal of Agricultural and Biological Engineering 2024年第3期17卷 21-32页

作者： Bangzhui Wang Zhong Tang Liyun Lao Guoqiang Wang Tiantian Jing Yao Yu School of Agricultural Engineering Jiangsu UniversityZhenjiang 212013JiangsuChina School of Water Energy and EnvironmentCranfield UniversityMK430ALUK Department of Agricultural Engineering Jiangsu Agriculture&Animal Husbandry Science and Technology Vocational CollegeTaizhou 225300JiangsuChina

Under diurnal temperature stress,the vascular bundle content of mature rice stems will change which will cause a change in the modulus of ***,the rice stems will collapse with the reduction in bending resistance because of the change in the modulus of *** order to reveal the distribution of vascular bundle gradients in rice stems under different climatic temperatures and explore the locations where stems are prone to bending and the form of stem damage,this study established a model of stem stiffness under free loading based on observing microstructure of the *** lodging characteristics of rice stems was explored seldom in different environmental temperatures from a micro structure of rice ***,the statistical analysis and t-tests were carried out on stems 1 to 4 in combination for cantilever bending tests at room temperature on stem internodes 3,versus three-point bending tests at-10℃ to 65℃ temperature *** showed that the bending resistance of the stem can be well predicted by using the vascular bundle distribution regression model and the variable stiffness mechanical *** bending resistance of No.3 stem was established by using the results obtained from the three-point bending test in a temperature range between 10℃-65℃.The correction coefficient TF of stem bending resistance under temperature difference induced stress was established based on the Gauss regression *** analysis showed that the bending resistance of No.3 stem was relatively large in a temperature range of 16℃-34℃.This study elucidated the variations of the mechanical properties of rice stems under temperature difference induced stress and provided a theoretical foundation for understanding the lodging characteristics of rice during mechanized harvesting.

关键词： rice stem vascular gradient stiffness model stem bending temperature stress

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