The demand for high-precision large-aperture antennas has continued to increase owing to the expanding application of spaceborne deployable active phased array antennas in remote sensing observation,satellite communic...The demand for high-precision large-aperture antennas has continued to increase owing to the expanding application of spaceborne deployable active phased array antennas in remote sensing observation,satellite communication,navigation positioning,and deep space exploration.However,deployment errors in deployable mechanisms,particularly hinge-induced deflection errors during array surface deployment,degrade on-orbit surface accuracy.This study proposes an active adjustment strategy that installs compliant parallel mechanisms on the backplane of antenna subarrays to regulate surface splicing precision.For one-dimensional(1D)deployable antennas,a two-translation one-rotation(2T1R)parallel mechanism configuration is employed for precision adjustment,whereas two-dimensional(2D)deployable antennas adopt a one-translation two-rotation(1T2R)configuration.A reconfigurable parallel mechanism architecture satisfying space deployment constraints-the 3PSS-2RPU-UPR/RPU parallel mechanism-is designed via configuration synthesis.The degrees of freedom(DOF)are verified via the screw theory,with complete inverse kinematics solutions derived.Search algorithms further quantify the adjustment workspace while clarifying the coupling relationships between DOFs.Equivalent compliant parallel mechanism models are obtained using the rigid-body replacement method,followed by a compliance analysis and motion simulation of compliant joints(notched flexure hinges and leaf-spring flexure prismatic joints).A systematic investigation of the deformation characteristics under different actuation modes confirmed the validity of the equivalent models.Ground experiments demonstrated close agreement between the measured and simulated adjustments,with open-loop adjustment errors constituting less than 10%of the adjustment range,thereby validating the feasibility of the method.The precision adjustment mechanism achieved configuration switching(2T1R/1T2R)through an inverted central limb design,integrating dual-mode compensation into a reconfigurable system.展开更多
In this paper, the factors of affecting surface roughness and profiles accuracy of the machined larege depth diamter ratio aspheric surfaces in ultra-precision grinding process are analyzed theoretically. An ultra-pre...In this paper, the factors of affecting surface roughness and profiles accuracy of the machined larege depth diamter ratio aspheric surfaces in ultra-precision grinding process are analyzed theoretically. An ultra-precision aspheric grinding system is then designed and manufactured. Aerostatic form is adopted to build the spindle of the workpiece, transverse guideway, longitudinal guideway and the spindle of the grinder in this system. The following specification is achieved, such as the turning accuracy of the spindle of the workpiece is 0.05 μm, radial rigidity of the spindle is GE 220N/μm, axial rigidity is GE 160 N/μm, radial rigidity of the guideway is GE 200N/μm, the highest rotational speed of the grinder is 80 000 rev/min and its turning accuracy is 0.1 μm, the resolution of linear displacement of the transverse and longitudinal guideway is 4.9 nm. Adjusting range of this adjusting mechanism is 2 mm in the Y direction, the adjusting accuracy of the precise adjusting mechanism is 0.1 μm. Micro displacement measuring system of this ultra-precision aspheric grinding adopts two-backfeed strategy, and angle displacement back-feed is realized by photoelectric encoder, it’s resolution is 655 360 pulse/rev. after 4 frequency multiplication, it’s angle displacement resolution is achieved 2 621 440 pulse/rev. Straight-line displacement is monitored by single frequency laser interferometer (DLSTAX LTM-20B, made in Japan). This CNC system adopts inimitable bi-arc step length flex CN interpolation algorithm, it’s CN system resolution is 5 nm.So this aspheric grinding system ensures profile accuracy of the machined part. The resolution of this interferometer is 5 nm. Finally, lots of ultra-precision grinding experiments are carried out on this grinding system. Some optical aspheric parts, with profiles accuracy of 0.3 μm, surface roughness less than 0.01 μm, are obtained.展开更多
The European XFEL, which has been constructed at DESY in Hamburg, Germany, is an X-ray-Free Electron Laser, which provides X-ray light of unprecedented properties for different experiments in physics, chemistry, biolo...The European XFEL, which has been constructed at DESY in Hamburg, Germany, is an X-ray-Free Electron Laser, which provides X-ray light of unprecedented properties for different experiments in physics, chemistry, biology and technology [1]. The XFEL is based on superconducting cavity technology, which is required to accelerate an electron beam up to 17.5 GeV. The facility is installed about 20 m underground in a 3.4 km long tunnel of 5.2 m diameter. High power RF systems are required to accelerate the beam to the required energy. Each RF station provides RF power to 4 accelerator modules with 8 superconducting cavities by a waveguide RF distribution system [2, 3]. Besides electrical and RF properties, mechanical properties are of high importance, since the waveguide distribution system and its components have to be manufactured, assembled and aligned with high precision. In order to test 100 superconducting accelerator modules within two years three test benches have been created in the AMTF （accelerator module test facility） to achieve the rate of one superconducting module per week. Each RF station of the test facility consists ofa 5 MW RF station at 1.3 GHz, 1.37 ms pulse width and 10 Hz repetition rate, with a waveguide distribution system. Each waveguide distribution supplies RF power to eight cavities, four times a pair of cavities. The distribution allows for a maximum power of 1 MW per cavity when the distribution is switched to a mode supplying power to only four cavities. A new type of 1 MW isolator and a new compact 5 MW power divider have been developed to achieve that goal. We present the waveguide distribution for this test stand and describe the performance of the different elements.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.52475023)Shanghai Municipal Natural Science Foundation(Grant Nos.24ZR1424300,23DZ2229032).
文摘The demand for high-precision large-aperture antennas has continued to increase owing to the expanding application of spaceborne deployable active phased array antennas in remote sensing observation,satellite communication,navigation positioning,and deep space exploration.However,deployment errors in deployable mechanisms,particularly hinge-induced deflection errors during array surface deployment,degrade on-orbit surface accuracy.This study proposes an active adjustment strategy that installs compliant parallel mechanisms on the backplane of antenna subarrays to regulate surface splicing precision.For one-dimensional(1D)deployable antennas,a two-translation one-rotation(2T1R)parallel mechanism configuration is employed for precision adjustment,whereas two-dimensional(2D)deployable antennas adopt a one-translation two-rotation(1T2R)configuration.A reconfigurable parallel mechanism architecture satisfying space deployment constraints-the 3PSS-2RPU-UPR/RPU parallel mechanism-is designed via configuration synthesis.The degrees of freedom(DOF)are verified via the screw theory,with complete inverse kinematics solutions derived.Search algorithms further quantify the adjustment workspace while clarifying the coupling relationships between DOFs.Equivalent compliant parallel mechanism models are obtained using the rigid-body replacement method,followed by a compliance analysis and motion simulation of compliant joints(notched flexure hinges and leaf-spring flexure prismatic joints).A systematic investigation of the deformation characteristics under different actuation modes confirmed the validity of the equivalent models.Ground experiments demonstrated close agreement between the measured and simulated adjustments,with open-loop adjustment errors constituting less than 10%of the adjustment range,thereby validating the feasibility of the method.The precision adjustment mechanism achieved configuration switching(2T1R/1T2R)through an inverted central limb design,integrating dual-mode compensation into a reconfigurable system.
文摘In this paper, the factors of affecting surface roughness and profiles accuracy of the machined larege depth diamter ratio aspheric surfaces in ultra-precision grinding process are analyzed theoretically. An ultra-precision aspheric grinding system is then designed and manufactured. Aerostatic form is adopted to build the spindle of the workpiece, transverse guideway, longitudinal guideway and the spindle of the grinder in this system. The following specification is achieved, such as the turning accuracy of the spindle of the workpiece is 0.05 μm, radial rigidity of the spindle is GE 220N/μm, axial rigidity is GE 160 N/μm, radial rigidity of the guideway is GE 200N/μm, the highest rotational speed of the grinder is 80 000 rev/min and its turning accuracy is 0.1 μm, the resolution of linear displacement of the transverse and longitudinal guideway is 4.9 nm. Adjusting range of this adjusting mechanism is 2 mm in the Y direction, the adjusting accuracy of the precise adjusting mechanism is 0.1 μm. Micro displacement measuring system of this ultra-precision aspheric grinding adopts two-backfeed strategy, and angle displacement back-feed is realized by photoelectric encoder, it’s resolution is 655 360 pulse/rev. after 4 frequency multiplication, it’s angle displacement resolution is achieved 2 621 440 pulse/rev. Straight-line displacement is monitored by single frequency laser interferometer (DLSTAX LTM-20B, made in Japan). This CNC system adopts inimitable bi-arc step length flex CN interpolation algorithm, it’s CN system resolution is 5 nm.So this aspheric grinding system ensures profile accuracy of the machined part. The resolution of this interferometer is 5 nm. Finally, lots of ultra-precision grinding experiments are carried out on this grinding system. Some optical aspheric parts, with profiles accuracy of 0.3 μm, surface roughness less than 0.01 μm, are obtained.
文摘The European XFEL, which has been constructed at DESY in Hamburg, Germany, is an X-ray-Free Electron Laser, which provides X-ray light of unprecedented properties for different experiments in physics, chemistry, biology and technology [1]. The XFEL is based on superconducting cavity technology, which is required to accelerate an electron beam up to 17.5 GeV. The facility is installed about 20 m underground in a 3.4 km long tunnel of 5.2 m diameter. High power RF systems are required to accelerate the beam to the required energy. Each RF station provides RF power to 4 accelerator modules with 8 superconducting cavities by a waveguide RF distribution system [2, 3]. Besides electrical and RF properties, mechanical properties are of high importance, since the waveguide distribution system and its components have to be manufactured, assembled and aligned with high precision. In order to test 100 superconducting accelerator modules within two years three test benches have been created in the AMTF （accelerator module test facility） to achieve the rate of one superconducting module per week. Each RF station of the test facility consists ofa 5 MW RF station at 1.3 GHz, 1.37 ms pulse width and 10 Hz repetition rate, with a waveguide distribution system. Each waveguide distribution supplies RF power to eight cavities, four times a pair of cavities. The distribution allows for a maximum power of 1 MW per cavity when the distribution is switched to a mode supplying power to only four cavities. A new type of 1 MW isolator and a new compact 5 MW power divider have been developed to achieve that goal. We present the waveguide distribution for this test stand and describe the performance of the different elements.
