| Owing to the traditional two-axis tracking frame inherently having large moment of inertia and easily affected by some factors such as shaft gap and the fraction,the response bandwidth cannot effectively compensate the high-frequency disturbances such as atmospheric turbulence and carrier vibration causing the beam to point inaccurate.In order to obtain micro-arc or sub micro-arc level of the dynamic direction of beam precision in the fields such as laser communication,laser weapon,space target monitoring and laser precision machining,we need to use a system such as the composite axis to control the two stage stabilization and a high frequency response characteristics of first-level aiming,which were achieved or relied on fast steering mirror.Therefore,the study of fast steering mirror had become one of the hot research topics at home and abroad.Combined with the current situation and development trend of related technology at home and abroad,the fast steering mirror system designed in this paper was based on the application requirements of the secondary system.It adopted the program which were based on flexible hinge structure and multi-point driving by piezoelectric ceramic actuator.Firstly,According to the targets such as positioning accuracy,through diameter,deflection range and response bandwidth,the type of driver,the type of sensor and driving form were determined.The system composition and performing principle were analyzed,which included the relationship between the driven displacements of PZTs and the angle of reflection Mirror,the brief introduction of PZT and the description of measurement sensors using MATLAB software to fit the approximate simplified mathematical model.Secondly,the linear power amplifier driving for piezoelectric ceramic of the principle are analyzed,which included electing the core devices were elected,designing the circuit schematic of the linear power amplifier,analyzing the stability and the anti-jamming of the circuit.Meanwhile,the linearity,resolution,output ripple,time drift and frequency response of the linear power amplifier circuit are tested.The test results were showed: 1)nonlinearity was 0.25%;2)resolution was 5mV;3)the maximum of output voltage ripple was 13.91mV;4)time drift was 10mV/8h;5)dynamic response bandwidth was 2kHz.Thirdly,building the hardware platform based on controller Euro209 and high precision capacitive sensor,the digital PID+feedforward closed loop control algorithm was used.The main program,serial communication program and alarm program were designed to achieve a multi-axis high-speed,high precision synchronization and decoupling control.Ultimately,the static and dynamic performance of FSM is tested.The tested results were showed: 1)the absolute value of static error was less than 0.25 urad and the RMS was less than 0.10urad;2)responding to the 90 urad and 180 urad of step signal,the rise time respectively were 5.12 ms and 6.40 ms and the time of reach ± 2% steady-error respectively were 7.85 m and 10ms;3)responding to the minimum angle of deflection was 0.16urad;4)from open loop control to closed loop control,step signal coupling was reduced from 12.71% to 0.60 and the dynamic coupling was reduced from 2.63% to 1.17%;5)the sin and cosine signals into round in which 10 Hz and 50 Hz of repetitive positioning accuracy were 0.20 urad and 100 Hz of repetitive positioning accuracy was 0.5urad. |
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