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December 22, 2004

Scientific conference of Institute of Problem of Mechanics (Russian Academy of Science). 

 

The report “Functional peculiarity of quadrature signal suppression in a two-part HRG” was presented by Bodunov S.B. and Vladimirov B.A. at the mutual scientific session between subdivision “Navigation systems and their sensitive elements” and St.Petersburg subdivision of precision gyroscopy on movement and navigation control.

Since 1998 Medicon has been developing a low-cost small-size hemispherical resonator gyroscope (HRG) for a number of civil applications. Earlier some technical solutions on creation of electronic control systems for two-part HRG design had been represented. These systems were based on separate application in time of pick-up voltages through the same electrodes.

To conform to the principle of consecutive system operation, the functioning of a quadrature component suppression system was based on application of alternating not direct voltages. That meant that quadrature component control was controlled not by a traditional method of the resonator’s rigidity change, but by force application. According to the test results of a number of HRGs with the electronic systems described above the following positive results were obtained:

  1. Quadrature suppression system effectively rejected resonators quadrature signal with frequency splitting range of 0,001–0,01Hz with the help of minor forces formed by force impulse voltages in the range 3–18V;
  2. Control system linearity is provided with width and amplitude modulation of a force signal;
  3. Timely division into the intervals of measurement and control makes it possible to exclude signal interference;
  4. High-voltage amplifier is eliminated and the power consumption is reduced.

In the process of various tests of HRGs in the force-to-rebalance (FTR) mode there was detected a cross impact of quadrature suppression channels and in-phase gyro component. Thus the value of temperature drift component in precession control channel tuned out to be depending on the quantity of a force impact in quadrature suppression channel. This magnitude appeared to be quite large and came to tenths of degree/hour/°С. Taking into consideration the key task to create devices with accuracy exceeding 0,1°/hour as well as increasing their dynamic performances, the principle of functioning of quadrature suppression component had been reconsidered.

Having considered disadvantages of an earlier electronic part design we developed another electronic part design with a new principle of a device that forms quadrature oscillation suppression signals. In addition to the force method it provides the possibility to introduce two extra “soft” impact modes — dynamic and static balancing.

Dynamic balancing mode is based on application of force impacts in one oscillation period at any two antiphase points. The dynamic principle of balancing is based on the following: as a result of application at one period of resonator oscillation of 2 impulses in anti-phase, the integral value of the force at one resonator oscillation period is equal to zero. The resonator hardness will change proportional to impulse duration, its amplitude and the number of  “force” resonator oscillation periods. Looking at function principle, the static balancing mode is close to the classic method of resonator hardness control method; DC voltage is formed by impulse chain, which length is equal to resonator oscillation period. The application of improved HRG control system helps to achieve the following results: increase needed range of angular AVS till 5°/sec at force impulse amplitude equal to 30 V.