Jin Huang,Jie Zhang. Key Laboratory of Electronic Equipment Structure Design Ministry of Education, Xidian University. Sept.

Transcription

1 电子装备结构设计 Metrology and Control of Large Telescopes workshop, 2016, Green Bank, US 教育部重点实验室 Wind Effect and its Compensation for Large Reflector Antennas Jin Huang,Jie Zhang Key Laboratory of Electronic Equipment Structure Design Ministry of Education, Xidian University Sept. 20, 2016

2 Outline Motivation Wind Effect Analysis Control Compensation Mechatronics Design Conclusions

3 Outline Motivation Wind Effect Analysis Control Compensation Mechatronics Design Conclusions

4 Motivation Advantages Narrow beam High gain Applications Large reflector antenna Radio astronomy Satellite communication Deep space exploration

5 Motivation Higher gain Better resolution Green Bank Telescope,2008 D: m/100MHz-115GHz Larger reflector Higher working frequency Higher pointing accuracy Pointing Accuracy Requirement: Pointing Accuracy Requirement: 4 arcseconds

6 Motivation Higher gain Better resolution Larger reflector Higher working frequency Larger windward area More flexible Disturbance Oscillation More sensitive to deformation Higher pointing accuracy Pointing accuracy The required pointing accuracy could be satisfied only when there is no wind!

7 Motivation Higher gain Better resolution Larger reflector Higher working frequency Radome Higher pointing accuracy Angular displacement Decrease its gain High cost, size limitation it ti Most Large Reflector Antennas work in open air

8 Motivation Higher gain Better resolution θ q n Larger reflector Higher working frequency Compensation Higher pointing accuracy Wind torque Excess drive torque Gawronski W.. Antenna control systems: from PI to H infinity, IEEE Antennas and Propagation Magazine, 2001, 43(1): Gawronski W., Ahlstrom, Jr.. Analysis and performance of the control system of the NASA 70-meter antennas. ISA transactions, 2004, 43:

9 Motivation Higher gain Better resolution θ n θ q Larger reflector Higher working frequency Compensation Higher pointing accuracy Wind torque Wind pressure

10 Motivation 66m S/X band antenna Higher gain Better resolution Larger reflector Higher working frequency Higher pointing accuracy Compensation Operation condition:wind speed of 10m/s Rotation angle error :29.52arcsec(RMS) Flexible pointing error:21.96arcsec(rms) Total pointing error:32.76arcsec(rms)

11 Motivation Higher gain Better resolution Mars Compensation Larger reflector Higher working frequency arcsec Higher pointing accuracy Pointing error caused by deformation

12 Motivation Higher gain Better resolution Mars Compensation Larger reflector Higher working frequency arcsec Higher pointing accuracy Pointing error caused by deformation Analysis Compensation Open Problem

13 Outline Motivation Wind Effect Analysis Control Compensation Mechatronics Design Conclusions

14 Wind Effect Analysis Traditional Rigid model Advantage: Lower order Disadvantage: Without any flexible information Antenna Structure Model PCOM That s why the pointing error caused by flexible deformation could not be compensated with those proposed methods.

15 Wind Effect Analysis Traditional Antenna Structure Model Rigid model Advantage: Lower order Disadvantage: Without any flexible information Finite element model Advantage: Describing flexible oscillation Disadvantage: Too much degree of freedom PCOM

16 Wind Effect Analysis Pointing Control Oriented Model Traditional Antenna Structure Model T = J θ + D Mq + Dq + Kq = B Rigid model: r θ Flexible model: 0u y = C q+ C q. oq q = Φq m. ov PCOM J 0 θ D 0 r θ 0 0 θ T B 11 J M + m qm B 11 D r D + m qm 0 K m q = m 0 F B 12 Nodes displacements y = C q mq m Rotation Angle Nodes displacements could evaluate the deformation of the structure

17 Wind Effect Analysis Traditional Analyze the extent of the pointing impact of all its vibration mode Antenna Structure Model Keep the Most Significant Modes Ignore the Least Significant Modes Model reduction PCOM PCOM

18 Wind Effect Analysis FE Modeling Model Calibration PCOM construction Traditional Antenna Structure Model PCOM

19 Wind Effect Analysis FE Modeling Model Calibration PCOM construction Traditional Model test Antenna Structure Model Load deformation test PCOM

20 Wind Effect Analysis FE Modeling Model Calibration PCOM construction Natural Frequency Traditional Test content Load (Kg) Test results (Hz) Simulation results (Hz) Relative error Antenna Structure % Model Deformation Test content Load Test results Calculate results Relative (Kg) (mm) (mm) error PCOM % % % %

21 Traditional Wind Effect Analysis FE Modeling Model Calibration PCOM construction Main reflector Feed Sub-reflector Sub-reflector Deformation displacement displacement rotation Antenna Structure Model The 1 st order The 3 rd order Order Energy ratio Pointing error in AZ( ) PCOM The 2 nd order 0.08% 9.4%

22 Wind Effect Analysis FE Modeling Model Calibration PCOM construction Traditional θ = θ + θ p Shaft rotation angle Pointing error caused by deformation n k = θ + F i = 1 Wind force Antenna Structure Model PCOM n n n n G i The order kept pointing error caused by each mode G = ( A G u + A G v + A G w + A G ) i 5,1 si s 5,2 si s 5,3 si s 5,4 si s= 1 s= 1 s= 1 s= 1 n n n n A 5,1 Gu si s + A 5,2 Gv si s + A 5,3 Gw si s + A 5,4 G si L 1 + L 3 s= 1 s= 1 s= 1 s= 1 n n n n L2( A 5,1 Gsius + A 5,2 Gsivs + A 5,3 Gsiws + A 5,4 Gsi ) s= 1 s= 1 s= 1 s= 1 n n n n ( A 1,1 Gu si s + A 1,2 Gv si s + A 1,3 Gw si s + A 1,4 Gsi) s= 1 s= 1 s= 1 s= 1 ( )( ) ( GiB + GiB + GiN + LG 1 iθ / M + LG 3 iθ) Pointing error caused Pointing error Pointing error caused by main reflector caused by feed by sub-reflector K w / f

23 Wind Effect Analysis Antenna Structure Model Traditional FE Modeling Model Calibration PCOM construction MAX DEFORMATIONS UNDER A 10M/S WIND SPEED Mi Main reflector rotation tti (deg) Displacement of the vertex (m) Displacement of the feed (m) Displacement of the sub-reflector(m) Sub-reflector rotation ti (deg) FEM Deformed Refector GRASP PCOM PCOM GRASP Relative error Pointing error % 4.6%

24 Wind Effect Analysis FE Modeling Model Calibration PCOM construction Traditional Max error(deg) RMS error(deg) FPE Antenna Structure RPE Model TPE PCOM FPE: Flexible pointing error RPE: Rotation error TPE: Total pointing error Wind torque and force almost have the same impact on pointing error Jie Zhang, Jin Huang*, Lili Qiu, et al, Analysis of reflector vibration-induced pointing errors for large antennae subject to wind disturbance, IEEE Antennas and Propagation Magazine, 2015, 57(6):

25 Outline Motivation Wind Effect Analysis Control Compensation Mechatronics Design Conclusions

26 Passive Compensation Traditional control method and improved PID: Disadvantage: flexible formation induced pointing error was neglected. Traditional pointing servo control Estimating Disturbance or Over all pointing error Disturbance Observer Based on LQG Based on predictive control Feedforward compensation directly Deriving a optimal control action Estimating disturbance and Pointing error for gust

27 Passive Compensation Based on DOB Based on LQG Based on MPC Disturbance Observer( DOB ) Estimating the overall disturbance (Wind induced torque/force, Model perturbation, Nonlinear Components) Wind Force F Wind Torque T PCOM G f Ref PID Motor and Reducer T m T w G t Beam pointing u d G m -1 G c G t -1 T d Q d DOB

28 Passive Compensation Based on DOB Based on LQG Based on MPC Linear-Quadratic-Gaussian(LQG) Q Wind torque T Wind force F Ref + - PI controller + u e + u Velocity controller Motor and Reducer PCOM + + Beam pointing Kc Estimated state- LQG controller (Alqg,Blqg,Clqg) LQG estimator + y Ke y Flexible information Estimated beam pointing LQG control system based on the PCOM. Kc: optimal feedback gain matrix Kc: optimal estimator gain matrix Jie Zhang, Jin Huang* and Jun Zhou et al., A compensator for large antennas based on pointing error estimation under a wind load, IEEE Trans. Control systems technology, accepted.

29 Passive Compensation Based on DOB Based on LQG Based on MPC Model Predictive Control( MPC ) Reject the disturbance of gust θ Wind Servo system Conventional method

30 Passive Compensation Based on DOB Based on LQG Based on MPC Model Predictive Control( MPC ) Reject the disturbance of gust Wind Servo system Sensor Estimating disturbance with wind field sensing

31 Passive Compensation Based on DOB Based on LQG Based on MPC Model Predictive Control( MPC ) Reject the disturbance of gust Wind force F PCOM Ref Integral control Velocity controller Motor and Reducer Wind torque T G f G t Pointing State observer Model predictive G t Wind control f G f force and torque estimation Wind forecast LSSVR Wind Speed

32 Passive Compensation Based on DOB Based on LQG Based on MPC Model Predictive Control( MPC ) Reject the disturbance of gust Sampling point wind speed Sampling point layout The comparison between test speed and the prediction speed

33 Passive Compensation Simulation results with 7.3m Antenna Pointin ng error( ) x DOB PID 10 LQG MPC Time(s) Control method Max pointing error( ) RMS pointing error ( ) PID % 66.6% DOB % 81.9% LQG % 85.8% MPC

34 Passive Compensation Simulation results with 7.3m Antenna In initial stage Pointing error( ( ) Time(s) Control method Max pointing error( ) PID DOB LQG MPC %

35 Outline Motivation Wind Effect Analysis Control Compensation Mechatronics Design Conclusions

36 Active Compensation 66m Beam Waveguide Antenna Moment of Inertia: kg m 2 Fundamental lfrequency:2.1hz 21H Bandwidth of servo system:0.6hz Performance for compensating high frequency pointing error Adjustable Plate Mirror Mirror Axis of elevation compensation Electric cylinder Improving the pointing accuracy Motor Axis of azimuth compensation

37 Active Compensation Real-time Pointing Error Compensation System( RPECS ) Sub-reflector B1 Main reflector Focal axis M 5 F M4 1 M 3 Wind Pitch axis Z O2 O 1 APM Y Focal O M 2 axis Feed Beam waveguide system

38 Active Compensation Real-time Pointing Error Compensation System( RPECS ) Primary servo RPECS Inverse kinematic analysis PID controller PID controller Motor model Electric cylinder model APM Forward kinematic analysis The primary servo subsystem is used to compensate the large-range g and slowly-varying y error. The subsystem is used to compensate the final pointing errors with high frequency components.

39 Active Compensation Real-time Pointing Error Compensation System( RPECS ) The comparison of the bandwidth between the primary servo and the APM servo

40 Active Compensation The compensation effect under a wind speed of 10m/s: Control o method Max pointing error( ) RMS Spointing gerror ( ) TPID RPECS % 92.7% Meet the requirement Jie Zhang, Jin Huang* and Shuangfei Wang et al., An active pointing compensator for large beam waveguide antenna under wind disturbance, IEEE/ASME Trans. Mechatronics, 2016, 21(2):

41 Outline Motivation Wind Effect Analysis Control Compensation Mechatronics Design Conclusions

42 Conclusion The wind effect on pointing accuracy for large antenna is analyzed, and a pointing control-oriented model is presented. Several Passive pointing error compensation is proposed, which improve the pointing performance effectively. An active compensation method is put forwarded, in which the high frequency disturbance can be rejected with a fast and high accuracy plate mirror. These wind disturbance compensation methods can be applied to newly These wind disturbance compensation methods can be applied to newly developed large reflector antennas and control system upgrading for those in operation with a low cost hardware, for an improved pointing performance.

43 Thank you!