Design Of Mental Fatigue Detection System Based On Pulse Wave

As a universal mental state,human mental fatigue is easily ignored by people,which has a certain degree of negative impact on people’s daily life and work.In order to greatly reduce the harm caused by human mental fatigue,finding suitable fatigue detection methods has become a hot topic in this field.Fatigue detection methods based on human physiological parameters have been proven to be feasible,but due to EEG and ECG The acquisition device of other signals is complicated,and it is difficult to perform real-time monitoring.Therefore,it is necessary to select another signal for fatigue detection.In order to meet the new needs of real-time monitoring of human mental fatigue,this paper designs a mental fatigue detection system based on pulse waves,which takes into account both portability and practicality.The main research work and innovations of this paper are as follows:The hardware design is based on the STM32 microprocessor as the main control chip,and the SFH7050 is selected as the photoplethysmographic acquisition module,with535 nm green light source,660 nm red light source and 940 nm infrared light source,together with the designed signal filtering,amplification,current/voltage conversion circuit And AFE4400 integrated analog front end to complete the collection and preprocessing of pulse wave signals.Finally,the Bluetooth HC-05 module was selected for wireless data transmission.The software design mainly has two parts,the lower computer and the upper computer software.The software of the lower computer is embedded in the acquisition device,and it mainly performs pulse wave signal acquisition,preprocessing and uploading the processed signal to the upper computer APP;the upper computer APP mainly includes a feature extraction module,a filtering algorithm module and a fatigue detection algorithm module,which performs the processing of the received signal Feature point recognition,extraction and fatigue detection calculation,and the final pulse wave waveform and detection results are displayed.Experiment with the designed collection device,and the collected data shows good results.The mental fatigue detection method based on pulse wave signal is researched.The peak time interval of the pulse wave signal is extracted,instead of the RR wave time interval of the ECG signal,the frequency domain index and non-linear index research of heart rate variability are carried out.First,the threshold method is used to identify the pulse wave peak value in a certain interval,and the identified pulse wave peak value is extracted as a time interval sequence;then,the frequency domain index LF/HF and nonlinearity of the time interval obtained are analyzed Index SD1/SD2;Finally,compare the frequency domain index and non-linear index under normal state and fatigue state to carry out related research on fatigue detection.Through corresponding experimental verification,this method can accurately determine whether the human body is in a state of mental fatigue.