The paper concludes that the energy given by Einstein’s famous formula E = mc2 consists of two parts. The first part is the positive energy of the quantum particle modeled by the topology of the zero set. The second ...The paper concludes that the energy given by Einstein’s famous formula E = mc2 consists of two parts. The first part is the positive energy of the quantum particle modeled by the topology of the zero set. The second part is the absolute value of the negative energy of the quantum Schr?dinger wave modeled by the topology of the empty set. We reason that the latter is nothing else but the so called missing dark energy of the universe which accounts for 94.45% of the total energy, in full agreement with the WMAP and Supernova cosmic measurement which was awarded the 2011 Nobel Prize in Physics. The dark energy of the quantum wave cannot be detected in the normal way because measurement collapses the quantum wave.展开更多
Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency,however,is difficult to be guaranteed in suc...Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency,however,is difficult to be guaranteed in such a process.To overcome this problem,a method of hybrid force-position control combined with PI/PD control is proposed to be applied in robotic abrasive belt grinding of complex geometries.Voltage signals are firstly obtained and transformed to force information with signal conditioning methods.Secondly,zero drift and gravity compensation algorithms are presented to calibrate the F/T transducer which is installed on the robot end-effector.Next,a force control strategy combining hybrid force-position control with PI/PD control is introduced to be employed in robotic abrasive belt grinding operations where the force control law is applied to the Z direction of the tool frame and the positon control law is used in the X direction of the tool frame.Then,the accuracy of the F/T transducer and the robotic force control system is analyzed to ensure the stability and reliability of force control in the robotic grinding process.Finally,two typical cases on robotic belt grinding of a test workpiece and an aero-engine blade are conducted to validate the practicality and effectiveness of the force control technology proposed.展开更多
以航天器交会对接过程中的平移靠拢段作为背景,研究适用于零重力和微重力环境下液体运动的等效力学模型.以欧空局无人货运飞船(ATV,automatic transfer vehicle)中建立的等效模型为参考,提出一种适用于零/微重力球形贮箱中液体晃动的弹...以航天器交会对接过程中的平移靠拢段作为背景,研究适用于零重力和微重力环境下液体运动的等效力学模型.以欧空局无人货运飞船(ATV,automatic transfer vehicle)中建立的等效模型为参考,提出一种适用于零/微重力球形贮箱中液体晃动的弹簧-质量等效力学模型.该模型的各个参数通过将基于CFD计算的参数辨识方法和用于常重力液体晃动的传统建模方法结合运用来获取.对该模型进行介绍,然后描述等效模型参数的获取方法,并利用虚功率原理推导了晃动力和力矩的求解方程.通过与CFD软件Flow-3d的结果进行对比,对这种建模方法的可行性和准确性进行了分析.展开更多
Gravity compensation refers to the creation of a constant supporting force to fully or partly counteract the gravitational force for ground verification to simulate the spacecraft dynamics in outer space with zero-or ...Gravity compensation refers to the creation of a constant supporting force to fully or partly counteract the gravitational force for ground verification to simulate the spacecraft dynamics in outer space with zero-or micro-gravity. Gravity compensation is usually implemented via a very low stiffness suspension/supporting unit, and a servo system in series is adopted to extend the simulation range to hundreds of millimeters. The error of suspension force can be up to tens of Newton due to the contact/friction in the suspension/supporting unit and the error of the force/pressure sensor. It has become a bottleneck for the ground verification of spacecraft guidance, navigation, and control systems with extreme requirements, such as tons of payload and fine thrust in sub-Newtons. In this article, a novel gravity compensation method characterized by quasi-zero stiffness plus quasi-zero deformation(QZS-QZD) is proposed. A magnetic negative stiffness spring in parallel with positive springs and aerostatic bearing is adopted to form a QZS supporting unit, and disturbance forces, such as contact or friction, can be eliminated. The deformation of the QZS supporting unit is measured via a displacement sensor, and the QZD control strategy is applied to guarantee the force error of gravity compensation to be less than sub-newtons and irrelevant to the payload. The principle of gravity compensation with QZS-QZD is analyzed, and performance tests on a prototype are carried out. The results show that when the spacecraft moves smoothly, the absolute force error is less than 0.5 N, the relative error of gravity compensation is less than 0.1%, and when collisions with other objects occur, the relative errors are 0.32% and 0.65%. The proposed method can significantly improve the gravity compensation accuracy in comparison with conventional approaches.展开更多
目的:为解决现有放射介入手术缺少防护手段以及铅防护衣的负重问题,研制一种新型零重力铅衣辐射防护系统。方法:该系统由万向底座、空心立柱、主副摇臂、悬坠体、铅衣挂架、缆线等装置组成。铅衣挂架及摇臂采用铝质轻体合金材料制作,底...目的:为解决现有放射介入手术缺少防护手段以及铅防护衣的负重问题,研制一种新型零重力铅衣辐射防护系统。方法:该系统由万向底座、空心立柱、主副摇臂、悬坠体、铅衣挂架、缆线等装置组成。铅衣挂架及摇臂采用铝质轻体合金材料制作,底座采用铸造铁碳合金制作,以便增加稳定性。防护面罩选用1.25 mm Pb铅防护玻璃制成,整体框架以不锈钢材料制作。铅防护衣选择0.75 mm Pb新型超轻、超薄、超柔软铅防护材料制作。缆线选用直径为3.5 mm的钢丝绳制作。结果:该防护系统轻便实用,在保证辐射防护效果的同时,解决了放射介入工作者穿着铅衣的负重问题。结论:该系统操作、移动方便,性能可靠,占用空间小,适用于各类放射介入和植入类手术防护,对保护放射工作者的职业健康具有重要意义和影响,应用前景广阔。展开更多
文摘The paper concludes that the energy given by Einstein’s famous formula E = mc2 consists of two parts. The first part is the positive energy of the quantum particle modeled by the topology of the zero set. The second part is the absolute value of the negative energy of the quantum Schr?dinger wave modeled by the topology of the empty set. We reason that the latter is nothing else but the so called missing dark energy of the universe which accounts for 94.45% of the total energy, in full agreement with the WMAP and Supernova cosmic measurement which was awarded the 2011 Nobel Prize in Physics. The dark energy of the quantum wave cannot be detected in the normal way because measurement collapses the quantum wave.
基金National Nature Science Foundation of China(Nos.51675394and 51375196)National Key Research and Development Program of China(No.2017YFB1303404)+2 种基金State Key Laboratory of Digital Manufacturing Equipment and Technology of China(No.DMETKF2018018)Fundamental Research Funds for the Central Universities of China(No.2017II33GX)the Key R&D Program of Jiangsu Province(No.BE2015005)
文摘Robotic belt grinding has emerged as a finishing process in recent years for machining components with high surface finish and flexibility.The surface machining consistency,however,is difficult to be guaranteed in such a process.To overcome this problem,a method of hybrid force-position control combined with PI/PD control is proposed to be applied in robotic abrasive belt grinding of complex geometries.Voltage signals are firstly obtained and transformed to force information with signal conditioning methods.Secondly,zero drift and gravity compensation algorithms are presented to calibrate the F/T transducer which is installed on the robot end-effector.Next,a force control strategy combining hybrid force-position control with PI/PD control is introduced to be employed in robotic abrasive belt grinding operations where the force control law is applied to the Z direction of the tool frame and the positon control law is used in the X direction of the tool frame.Then,the accuracy of the F/T transducer and the robotic force control system is analyzed to ensure the stability and reliability of force control in the robotic grinding process.Finally,two typical cases on robotic belt grinding of a test workpiece and an aero-engine blade are conducted to validate the practicality and effectiveness of the force control technology proposed.
文摘以航天器交会对接过程中的平移靠拢段作为背景,研究适用于零重力和微重力环境下液体运动的等效力学模型.以欧空局无人货运飞船(ATV,automatic transfer vehicle)中建立的等效模型为参考,提出一种适用于零/微重力球形贮箱中液体晃动的弹簧-质量等效力学模型.该模型的各个参数通过将基于CFD计算的参数辨识方法和用于常重力液体晃动的传统建模方法结合运用来获取.对该模型进行介绍,然后描述等效模型参数的获取方法,并利用虚功率原理推导了晃动力和力矩的求解方程.通过与CFD软件Flow-3d的结果进行对比,对这种建模方法的可行性和准确性进行了分析.
基金supported by the National Key R&D Program of China (Grant No. 2020YFB2007601)the National Natural Science Foundation of China (Grant No. 52075193)the National Major Science and Technology Projects of China (Grant No. 2017ZX02101007-002)。
文摘Gravity compensation refers to the creation of a constant supporting force to fully or partly counteract the gravitational force for ground verification to simulate the spacecraft dynamics in outer space with zero-or micro-gravity. Gravity compensation is usually implemented via a very low stiffness suspension/supporting unit, and a servo system in series is adopted to extend the simulation range to hundreds of millimeters. The error of suspension force can be up to tens of Newton due to the contact/friction in the suspension/supporting unit and the error of the force/pressure sensor. It has become a bottleneck for the ground verification of spacecraft guidance, navigation, and control systems with extreme requirements, such as tons of payload and fine thrust in sub-Newtons. In this article, a novel gravity compensation method characterized by quasi-zero stiffness plus quasi-zero deformation(QZS-QZD) is proposed. A magnetic negative stiffness spring in parallel with positive springs and aerostatic bearing is adopted to form a QZS supporting unit, and disturbance forces, such as contact or friction, can be eliminated. The deformation of the QZS supporting unit is measured via a displacement sensor, and the QZD control strategy is applied to guarantee the force error of gravity compensation to be less than sub-newtons and irrelevant to the payload. The principle of gravity compensation with QZS-QZD is analyzed, and performance tests on a prototype are carried out. The results show that when the spacecraft moves smoothly, the absolute force error is less than 0.5 N, the relative error of gravity compensation is less than 0.1%, and when collisions with other objects occur, the relative errors are 0.32% and 0.65%. The proposed method can significantly improve the gravity compensation accuracy in comparison with conventional approaches.
文摘目的:为解决现有放射介入手术缺少防护手段以及铅防护衣的负重问题,研制一种新型零重力铅衣辐射防护系统。方法:该系统由万向底座、空心立柱、主副摇臂、悬坠体、铅衣挂架、缆线等装置组成。铅衣挂架及摇臂采用铝质轻体合金材料制作,底座采用铸造铁碳合金制作,以便增加稳定性。防护面罩选用1.25 mm Pb铅防护玻璃制成,整体框架以不锈钢材料制作。铅防护衣选择0.75 mm Pb新型超轻、超薄、超柔软铅防护材料制作。缆线选用直径为3.5 mm的钢丝绳制作。结果:该防护系统轻便实用,在保证辐射防护效果的同时,解决了放射介入工作者穿着铅衣的负重问题。结论:该系统操作、移动方便,性能可靠,占用空间小,适用于各类放射介入和植入类手术防护,对保护放射工作者的职业健康具有重要意义和影响,应用前景广阔。
