The Generating Method And Experiment Of SPWM Signal For Sound Source In Seafloor Sediment Measurement Based On STM32

In modern ocean development,the research of seafloor sediment has an important impact on energy extraction and national defense construction,and the performance of seafloor sediment measurement system directly affects the measurement results,so the requirements for seafloor sediment measurement system are constantly improving,and the reduction of power consumption is especially important for in-situ measurement.The seafloor sediment measurement system generally consists of control module,acoustic signal generation module,acoustic emission drive module,signal conditioning module and sampling module.There are two methods for generating acoustic signals,one is hardware and the other is software.The current acoustic wave signal generation module uses an analog circuit to generate the corresponding sinusoidal pulse width modulation(hereinafter referred to as SPWM)signal to the emission drive module for power amplification,and the power consumption of the signal generation module accounts for 20% of the overall system power consumption.Under the condition that the main control module adopts STM32 low-power CPU,the high-speed characteristics of STM32 are used to directly generate SPWM signals,eliminating the need for signal generation modules,so that the seafloor sediment measurement system can reduce power consumption and system complexity,which is of great significance for in-place acoustic wave measurement.This paper studies the SPWM signal directly generated by STM32 CPU combined with natural sampling method.The SPWM signal corresponding to the acoustic signal is generated through STM32 program and input into the acoustic emission power amplifier circuit(hereinafter referred to as the power amplifier circuit).The amplified SPWM voltage waveform is obtained through low-pass filtering and the driving voltage corresponding to the original acoustic signal waveform is stimulated to generate the acoustic wave.In order to meet the needs of time domain measurement and frequency domain measurement,sinusoidal wave,sweep wave and am wave are used as acoustic signals to carry out experimental research.The main tasks completed in this paper are as follows:(1)Discussed the principle of SPWM,two modulation methods of SPWM and three generation algorithms.Through comparative analysis,it is determined that the modulation method in this article is bipolar modulation and the generation algorithm is natural sampling.On this basis,this article proposes a digital method based on STM32 to generate SPWM signals.(2)Introduced the seafloor sediment measurement system developed by the research team in the early stage,and proposed an improvement plan.And elaborate the main content of the improvement,and the corresponding Class D power amplifier circuit.(3)Discuss the software development process,which focuses on analyzing the complementary output of SPWM,the design of the dead time,and the influence of the amplitude and frequency of the acoustic signal on the output waveform of SPWM.In order to facilitate the comparison of experiments,the DAC and DMA output programs related to waveforms are also designed.(4)Experiments were carried out to verify the above results.The experimental results show that the digital method of generating SPWM signal based on STM32 and the program designed and developed in this paper can effectively generate three sound wave waveforms through the power amplifier circuit.It also shows that the method of generating SPWM signal of sound source based on STM32 for seabed sediment measurement proposed in this paper And the procedure is correct and effective.