基于CC2541的生猪光电式心率测量方法研究

Photoelectric heart rate measuring method for pig based on CC2541

【目的】研制一款基于光电容积脉搏波(Photoplethysmographic,PPG)原理的生猪心率测量耳标,实现生猪心率的在线监测。【方法】依据PPG原理,采用So C芯片CC2541、光电式心率传感器、MPU6050等研制一款基于CC2541蓝牙4.0的生猪心率测量耳标,分析生猪心率信号的运动干扰来源,同时采集人体模拟生猪运动下的心率信号,导入MATLAB软件,以快速傅里叶变换(Fast Fourier transform,FFT)处理分析PPG信号、运动信号的频域特征及低频采样对心率数据提取结果的影响,并将FFT移植到CC2541中直接提取心率数据。【结果】猪耳与传感器间的相对运动是生猪心率信号干扰的主要因素。当猪耳与心率传感器间的夹持压力在0.6~1.5 N时,传感器能输出完整的PPG信号波形,在生猪安静状态下能准确获取心率数据,在生猪运动状态下通过FFT算法也可有效提取心率数据。在CC2541的RAM容量限制下,采样数为128点,能满足FFT算法提取心率数据。通过CC2541中FFT处理得到的心跳频率为2.813 Hz,生猪心率=2.813 Hz×60 s=168.78次/min,生猪安静状态下人工测量的心率为160.00次/min,二者基本相符。【结论】基于CC2541蓝牙4.0的生猪心率测量耳标具有体积小、抗运动干扰强、功耗低的特点,适合对生猪进行长期动态的心率监测,为开展生猪健康预警、动物福利、行为建模等研究提供一种新手段。

[Objective]The paper aimed to develop a pig ear tag measuring heart rate which was based on the principle of photoplethysmographic（PPG） so as to realize the on-line monitoring of pig heart rate. [Method]According to PPG prin-ciple, SoC chip CC2541, photoelectric pulse sensor and MPU6050 were used to develop a pig ear tag measuring heart rate based on CC2541 bluetooth 4.0 and then analyzed main source of movement interference for pig heart rate. Meanwhile, heart rate signals of human body simulating pig movement were collected and imported into MATLAB software. Fast fourier transform（FFT） was used to analyze effects of PPG signals, frequency domain of movement signals and low frequency sampling on the extraction of heart rate. FFT was transplanted into CC2541 and directly extract the heart rate. [Result]The relative motion between pig ear and sensor was the main internal cause in movement interference. When the clamping pre-ssure between pig ear and sensor was within the scope of 0.6-1.5 N, the sensor can output full PPG signal waveform. The ear tag could accurately obtain the heart rate when pigs were in static state, while the heart rate data was extracted effective-ly by FFT algorithm when pigs were in movement state. Under the limits of CC2541 RAM capacity, the ear tag could satis-fy FFT algorithm to extract the heart rate when using 128 sampling points. The heartbeat rate was 2.813 Hz treated by FFT in CC2541 so the pig heart rate=2.813 Hz＆#215;60 s=168.78 beat/min. The heart rate was 160.00 beat/min by manual measure-ment in static state. The two results were basically coincide. [Conclusion]Heart rate measuring pig ear tag based on CC2541 bluetooth 4.0 enjoys the characteristics of small size, strong anti-movement interference and low power consump-tion, which is suitable for long-term and dynamic monitoring of pig heart rate. It provides a new method for the study of pig health early warning, animal welfare, behavior modeling and others.