Development Of Time-domain Aeroelectromagnetic Transmitting Circuit Based On Amplitude Tracking Technology

Time-domain Aeroelectromagnetic Method is an Effective Geological Exploration Method,which can complete exploration tasks in the air and has obvious environmental advantages.It has been widely used in Mineral Exploration,Environmental Monitoring,Detection of Buried Pipelines and Ocean Available Ice and other aspects.The Detection Depth and Precision of Airborne Electromagnetic Method in Time-domain are closely related to the quality of transmitting waveform.Currently,in the actual detection process,Transmitting Current Waveform has many problems,such as large ripple in the flat-top section,low property along the descending line,and long cutting-off time,which seriously limit the high-precision measurement of Aeroelectromagnetic System.In view of the above problems,this paper,under the funding of the National Key Research and Development Program "Development of Helicopter Aeroelectromagnetic Measurement Technology System(2017YFC0601802)",carried out the research on the Time-domain Aeroelectromagnetic Transmission Circuit based on Amplitude Tracking Technology.The main research contents are as follows:1.In order to realize the quick cutting-off of the transmitting current,the Bridge Arm Switch of the Inverter Circuit is improved on the basis of the Traditional Aeroelectromagnetic Transmitting Circuit.The active Clamping Feed-energy Circuit is added to accelerate the discharge process of the load coil,which is beneficial to realize the energy feedback.2.According to the topological structure of the Airborne Electromagnetic Inverter Circuit,a Amplitude Tracking Technology is proposed.The relationship between the transmitting current and the clamping voltage is taken as an important basis for regulating the transmitting circuit.3.According to the design requirements of Amplitude Tracking Technology for the launch system,a combined transmitter controller is designed.Freescale,as the main control chip,is mainly used for the realization of Amplitude Tracking Method and the fault monitoring of the launch system.FPGA chip and peripheral circuit are mainly used for data acquisition and conversion.SPI serial communication is adopted between the two chips for data interaction.In order to drive SiC MOSFET devices accurately and avoid misfiring,a special Driving Circuit Topology is designed and the switching loss of transmitting bridge is calculated.4.Using PLECS to carry out system simulation on the transmitting circuit to verify the feasibility of the topology;the output characteristic and switching loss of SiC MOSFET are measured by Double Pulse Circuit.Tracking technology based on Amplitude of Time-domain Aeroelectromagnetic Launch System in national engineering research center for geophysical detection instrument field experiment.The results show that the input voltage 384 V,flat-topped period of peak current is 400 A,the highest clamping voltage 500 V,under the condition of linearity can be optimized to 99.77%,cutting-off time reduced from 1.5 ms to 963 ?s,and reached the desired effect.The Aeroelectromagnetic Launch Circuit in time-domain based on Amplitude Tracking Technology developed in this paper has been improved in hardware equipment and control method at the same time,which provides a new idea for the subsequent research on the design of Time-domain Aeroelectromagnetic Launch System The quality of launch current,energy consumption and stability of the system are improved,and the detection accuracy of the Aeroelectromagnetic System is improved.