Mental Stress Analysis System Based On Heart Rate HRV Theory

Heart rate variability(HRV)refers to the small difference between successive heart beat,which occurs in the autonomic nervous system on the modulation of the cardiac sinus node.By observing heart rate variability,the body's autonomic nervous system can be evaluated.HRV has a close relationship with the body's blood pressure,breathing,hormones and emotions.Therefore,heart rate variability is identified as the best indicator of mental stress.After scientific experiments and repeated demonstration,heart rate variability has become the most objective,accurate and direct method to measure the pressure of human body.This paper conbines heart sound analysis and heart rate variability principle to design and implement a mental pressure analyzer system.Psychoanalysis analysis system based on HRV theory is divided into three modules: heart sound collection module,heart sound analysis module and mental stress analysis module.Heart sound collection module uses a modified shoulder strap wireless heart sound collector which can effectively capture the heart sound signal for a long time.Based on the characteristics of the heart sound signal,the heart sound analysis module proposes a fast segmentation algorithm based on dual threshold which can accurately identify the first heart sound S1,systolic period,the second heart sound S2 and diastolic period of heart sound,and calculate the time of each part.The time of each part is then calculated to obtain the cardiac cycle sequence.According to the acquired cardiac cycle sequence,the stress analysis module analyzes the heart rate variability with time domain analysis mothod,frequency domain analysis mothod,and Poincaré analysis mothod.Based on the characteristic indicators of heart rate variability,the system assess the state of mental pressure from five aspects which are the pressure index,fatigue index,anti-pressure ability,autonomic nervous system activity and autonomic nervous system stability.The mental stress analyzer system designed and implemented by this paper not only can accurately assess the mental stress state of the human body,but also has the features of complete function,low cost and easy to operate,which has high popularization and practical value.