5:15 PM - 6:45 PM
[PCG20-P07] Modeling of frequency characteristic and comparison with hardware performance for digital-type fluxgate magnetometer
Keywords:magnetometer, small satellite, space observation, planetary exploration
Digital-type fluxgate magnetometers have been developed and installed on satellites and rockets in Japan and other countries because they have advantages in reducing power consumption and weight compared to conventional analog-type fluxgate magnetometers. In this study, the frequency characteristics of a digital-type magnetometer are numerically modeled and compared with those of manufactured hardware to expand the possibilities for advanced magnetic field measurement in the future space-science mission.
The fluxgate magnetometer measures the external magnetic field strength and direction by the non-linearity characteristics of magnetic field in a soft-magnetic core in the sensor. Artificial magnetic field is excited by alternating current flowing through a drive coil wound around the core, and the induced voltage in another coil, pickup coil, wound around the same core, is detected as the signal corresponding to the external field. For the digital-type fluxgate magnetometer, developed for use on spacecraft, a Field Programmable Gate Array (FPGA), a digital logical processor, is used to perform most of the pickup signal processing. Therefore, the weight and power consumption of its circuit can be reduced compared to analog-type fluxgate magnetometer. Recently the target of space exploration is expanded to the wider area in the solar system. As a result, observation instruments of wider variety are installed on a single spacecraft and the technology for the in-situ observation has been developed to suit that condition. Digital-type fluxgate magnetometer, which is small and power-saving compared with the conventional analog-type, is more suitable for the future exploration by spacecraft, on which more various and smaller observation instruments would be installed. Meanwhile the devices and materials used in instruments on spacecraft require a high degree of reliability and must be tolerant of the severe space environment, e.g., high and low temperatures and radiation. The reliability and environment tolerance strictly restrict the available device, material and design of the instruments. The goal of this research is to develop a digital-type magnetometer with improved performance over conventional one while overcoming these limitations.
This study and development are based on the design of a digital-type fluxgate magnetometer designed for the SS-520-3 sounding rocket. Since the output data from the magnetometer to the magnetic-field input depend on the frequency of the magnetic field time variation, the frequency characteristics of the response of the magnetometer should be evaluated with high accuracy. We numerically simulated and modeled the frequency characteristics of the signal processing in FPGA as well as the surrounding analog circuit, and derived the overall transfer function of the digital-type fluxgate magnetometer. The obtained frequency response model is then compared with the frequency response of the manufactured hardware.
We will present the scheme to model the frequency response of the digital-type fluxgate magnetometer, show the results of the comparison of the characteristics of the model and the actual hardware, and discuss the causes of the differences.
In the future, based on the results of this study, we will improve the parameter design of the digital-type fluxgate magnetometer that could detect higher frequency magnetic field fluctuations.
The fluxgate magnetometer measures the external magnetic field strength and direction by the non-linearity characteristics of magnetic field in a soft-magnetic core in the sensor. Artificial magnetic field is excited by alternating current flowing through a drive coil wound around the core, and the induced voltage in another coil, pickup coil, wound around the same core, is detected as the signal corresponding to the external field. For the digital-type fluxgate magnetometer, developed for use on spacecraft, a Field Programmable Gate Array (FPGA), a digital logical processor, is used to perform most of the pickup signal processing. Therefore, the weight and power consumption of its circuit can be reduced compared to analog-type fluxgate magnetometer. Recently the target of space exploration is expanded to the wider area in the solar system. As a result, observation instruments of wider variety are installed on a single spacecraft and the technology for the in-situ observation has been developed to suit that condition. Digital-type fluxgate magnetometer, which is small and power-saving compared with the conventional analog-type, is more suitable for the future exploration by spacecraft, on which more various and smaller observation instruments would be installed. Meanwhile the devices and materials used in instruments on spacecraft require a high degree of reliability and must be tolerant of the severe space environment, e.g., high and low temperatures and radiation. The reliability and environment tolerance strictly restrict the available device, material and design of the instruments. The goal of this research is to develop a digital-type magnetometer with improved performance over conventional one while overcoming these limitations.
This study and development are based on the design of a digital-type fluxgate magnetometer designed for the SS-520-3 sounding rocket. Since the output data from the magnetometer to the magnetic-field input depend on the frequency of the magnetic field time variation, the frequency characteristics of the response of the magnetometer should be evaluated with high accuracy. We numerically simulated and modeled the frequency characteristics of the signal processing in FPGA as well as the surrounding analog circuit, and derived the overall transfer function of the digital-type fluxgate magnetometer. The obtained frequency response model is then compared with the frequency response of the manufactured hardware.
We will present the scheme to model the frequency response of the digital-type fluxgate magnetometer, show the results of the comparison of the characteristics of the model and the actual hardware, and discuss the causes of the differences.
In the future, based on the results of this study, we will improve the parameter design of the digital-type fluxgate magnetometer that could detect higher frequency magnetic field fluctuations.