| Gyroscope power is a quite important part of the inertial navigation system, whose performance will influence the precision of the whole system directly. This article is proposed to take the SPWM three-phase sinusoidal inverter power as the gyroscope power. Because the three-phase sinusoidal inverter power has good stability and the precision, which can cause the inertial navigation system reliable movement. At the same time, it has little high orders harmonics, which helps to enhance the system's precision.First, we introduce the study actuality of inverter in this paper as general. After that, we give out the whole design plan of the power system in the paper. We also analyze the design of commutate circuit, filter circuit and inverter circuit detailedly. This paper focuses on the realization of SPWM, and discusses the advantages and disadvantages of each method of SPWM. We use the TI Corporation's MSP430F147 as the control chip, and it can easily generate PWM wave output. We choose the symmetry regulation sample method as SPWM arithmetic.Filter circuit used IPM (intelligent power module), which has high input impedance, high switch speed, low switch power, simple driving circuit, small driving power and other characteristics. Control function of IPM combined with microprocessor can build intelligent power control system easily. Since the resonance LC filter of the filter circuit was designed for some specifically frequency, the filter circuit was useful for nothing for than basic wave and unchangeable resonance frequency. The filter circuit can eliminate the harmonics e, and make the basic wave unblocked. The inverter circuit used PWM not only can adjust the voltage, but also improve the waveform.The key point of this paper is the realization of SPWM(Sinusoidal pulse width modulation).Under the control of control circuit whose control rule is fixed, the switch is on or off, then the output of the inverter is a set of pulse equal amplitude, equal range, but different width. According sampling principle, this set of pulses is equal to inertia controlled object.There are two methods for modulating pulse width, stimulant modulation and digital modulation. The former uses triangular wave with higher frequency as the carrier signal, and the sine wave with lower frequency as modulate signal. The modulation result of the former two signals is a series of rectangular pulse with different amplitude which can be used for producing SPWM. There are several ways for producing digital SPWM, such as natural sampled PWM, equivalent area PWM, dissymmetrical sampled PWM, symmetrical sampled PWM and lower-order harmonic eliminated PWM. Smmetrical sampled PWM was adopted in the paper. Besides, the symmetrical sampled PWM has easier sampling.The CMOS chip used in this paper is MSP430F147, and the 16-bit SCM is a new generation product developed in TI. The 16-bit SCM was designed in brain-new concept with advantages of low power voltage, low consumed power, so this SCM is very suitable for low power equipment, and give PWM output expediently.After a series of debugging and improvements, the accuracy and stability of the power system has been able to meet gyroscope requirements. The output sine wave waveform distortion is extremely small, and the RMS value of the output voltage can be stabilized at 110V. And the output can maintain strict three alternate with the phase relations. Therefore, this gyroscope power improvement program, proposed in the article, can very good satisfy the operation requirements. |
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