压电陶瓷驱动FSM三自由度柔性支撑设计

为了有效吸收反射镜偏转造成驱动点的横向位置偏差,保护压电陶瓷驱动器,抑制反射镜在非工作方向上的自由度,提高系统谐振频率,设计了基于压电陶瓷驱动的快速反射镜三自由度柔性支撑。首先根据压电陶瓷驱动的快速反射镜对柔性支撑的设计要求确定了由支撑杆与支撑片组成的三自由度四周式柔性支撑方案,再利用压杆稳定性理论与变形能法对支撑杆与支撑片进行参数设计,最后利用workbench对设计结果进行分析。有限元分析结果表明,直径1 mm、长度8 mm的柔性支撑杆的应用可以使压电陶瓷的剪切位移减少86.7%,柔性支撑片的应用使反射镜一阶模态为轴向平移振动,谐振频率为360 Hz,二三阶模态为反射镜两轴偏摆振动,谐振频率为420 Hz,而高阶模态在1 000 Hz以上。三自由度柔性支撑可以有效防止压电陶瓷受到剪切破坏,提高快速反射镜结构谐振频率,有利于提高系统闭环带宽。

Design of three DOFs flexure support for FSM driven by piezoelectric ceramics

Three DOFs elastic support for fast steering mirror driven by piezoelectric is designed in order to effectively absorb the lateral deviation of driving point caused by tilting of mirror, protect the piezoelectric drivers, restrain the DOF in non-working direction and enhance the frequency resonance of system. Firstly the scheme of all-around elastic support which consists of flexure ring and flexure staff was determined according to requirements of fast steering mirror driven by piezoelectric design. Secondly flexure ring and flexure staff was designed separately based on the buckling theory and energy theory. Finally the design was analyzed with FEA software workbench. The FEA analysis shows that the sheer displacement of piezoelectric decreases 86.7% with the application of 8 mm length and 1mm diameter flexure staff. In addition, the application of flexure ring turns the axial translation vibration into the first-order mode with resonance frequency of 340 Hz,turns the swing vibration into the second and the third order mode with resonance frequency of 420 Hz and the higher-order resonance frequency is more than 1 000 Hz. The three DOFs elastic support can prevent piezoelectric from sheering damage and help to enhance the resonance frequency of fast steering mirror system, which does help to enhancing the close-loop bandwidth of the system.