Cloverleaf microgyroscope with electrostatic alignment and tuning

Abstract

A micro-gyroscope ( 10 ) having closed loop operation by a control voltage (V ty ), that is demodulated by an output signal of the sense electrodes (S 1 , S 2 ), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope ( 10 ) on the output axis (y-axis). The present invention provides independent alignment and tuning of the micro-gyroscope by using separate sensors and actuators to detect and adjust alignment and tuning. A quadrature amplitude signal is used to detect misalignment, that is corrected to zero by an electrostatic bias adjustment. A quadrature signal noise level, or a transfer function test signal, is used to detect residual mistuning, that is corrected to zero by a second electrostatic bias adjustment.

What is claimed is:  
     
         1 . A method for aligning a micro-gyroscope having closed loop control of drive, output and sense axes, said method comprising the steps of: 
 detecting misalignment of said micro-gyroscope; and    correcting misalignment to zero by an electrostatic bias adjustment.    
     
     
         2 . The method as claimed in  claim 1  wherein said step of detecting misalignment further comprises detecting misalignment by way of quadrature signal amplitude obtained by demodulation of a signal of said output axis using a signal in quadrature to rate signal for said drive axis.  
     
     
         3 . The method as claimed in  claim 1  further comprising the step of nulling an in-phase bias.  
     
     
         4 . The method as claimed in  claim 3  wherein said step of nulling an in-phase bias further comprises nulling by electronically coupling a torque component of said drive axis with said output axis.  
     
     
         5 . A method for tuning a cloverleaf micro-gyroscope having closed loop control of drive, output and sense axes, said method comprising the steps of: 
 detecting residual mistuning by way of a signal; and    correcting said residual mistuning to zero by way of electrostatic bias adjustment.    
     
     
         6 . The method as claimed in  claim 5  wherein said step of detecting residual mistuning further comprises detecting by way of a quadrature signal noise level.  
     
     
         7 . The method as claimed in  claim 5  wherein said step of detecting residual mistuning further comprises detecting by way of a transfer function test signal.  
     
     
         8 . A method for independently aligning and tuning a cloverleaf micro-gyroscope having closed loop control of drive, output and sense axes, said method comprising the steps of: 
 detecting misalignment of said micro-gyroscope by way of a quadrature signal amplitude;    correcting said misalignment to zero by way of an electrostatic bias adjustment;    detecting residual mistuning by way of a signal; and    correcting said residual mistuning by way of an electrostatic bias adjustment.    
     
     
         9 . The method as claimed in  claim 8  wherein said step of detecting a residual mistuning further comprises detecting a residual mistuning by way of a quadrature signal noise level.  
     
     
         10 . The method as claimed in  claim 8  wherein said step of detecting a residual mistuning further comprises detecting a residual mistuning by way of a transfer function test signal.  
     
     
         11 . The method as claimed in  claim 8  further comprising the step of nulling in-phase bias.  
     
     
         12 . The method as claimed in  claim 11  wherein said step of nulling further comprises electronically coupling a torque component of said drive axis with said output axis.  
     
     
         13 . The method as claimed in  claim 8  wherein said micro-gyroscope closed loop control further comprises: 
 using separate sensors and actuators for said step of correcting said misalignment and said step of correcting said residual mistuning.  
 
     
     
         14 . The method as claimed in  claim 8  wherein said step of correcting said misalignment further comprises the step of introducing an electrostatic cross-coupling spring, K e   xy  for canceling said misalignment.  
     
     
         15 . The method as claimed in  claim 14  further comprising the step of applying a bias voltage to a drive electrode on said drive axis that is different from a bias voltage to another drive electrode on said drive axis.  
     
     
         16 . The method as claimed in  claim 8  further comprising the step of introducing a relative gain mismatch, δ T ≈0, to each drive electrode on said drive axis.  
     
     
         17 . The method as claimed in  claim 8  further comprising the step of maximizing a stiffness matrix K.  
     
     
         18 . The method as claimed in  claim 8  wherein said step of correcting said residual mistuning to zero further comprises adjusting a total stiffness of said micro-gyroscope.