基于超弹性金属的间断式奶牛瘤胃pH测量探头设计与试验

Design and Experiment of Intermittent Probe for Rumen pH Measurement in Dairy Cows

摘要:

在现代奶牛养殖中，瘤胃pH值是牛只健康的一项重要生理指标。现有电极中，间断式pH参比电极采用气体增压促进电解液渗出。但是，存在电解液流出可能被阻断的风险。本文使用超弹性金属设计了控制参比液间断流出的阀门和基于弹簧活塞系统的参比液加压部件，完成间断式奶牛瘤胃pH检测探头设计。首先对阀门部件进行有限元分析，确定阀门部件中镍钛合金棒长度为9 mm，硅胶管中轴线到镍钛合金棒固定端距离为4.5 mm；压强部件使用弹簧配合活塞进行加压，所用弹簧刚度0.284 N/mm，自由高度70 mm，最大压缩量49 mm。通过仿真试验，明确镍钛合金棒最大应力为281 MPa，处于超弹性范围内，可循环使用；性能试验表明探头可在误差小于0.1的情况下稳定工作。根据寿命试验可知，该探头可稳定释放缓冲液60 480次。在测量间隔为20 min的情况下，探头可工作2年。现场瘤胃测量试验中，人工测量值与系统测量值平均绝对偏差为0.11，最大绝对偏差为0.25，表明设备满足实际应用需求。

Abstract:

Rumen pH is an important physiological indicator for the health of cows in modern dairy farming.Among the existing electrodes, the intermittent pH reference electrode uses gas pressurization to promote the electrolyte exudation. However, there is a risk that the electrolyte outflow may be blocked. Hyperelastic metal was used to design a valve to control the intermittent outflow of reference electrolyte and a reference electrolyte pressurization component-based on a spring piston system.The final assembly of the intermittent rumen pH detection probe in dairy cows was completed. The finite element analysis of the valve component determined that the length of the hyperelastic metal rod in the valve component was 9 mm, and the distance between the central axis of the silicone tube and the fixed end of the nitinol rod was 4.5 mm. The pressure component used a spring with a piston for pressure, the spring stiffness was 0.284 N/mm, the free height was 70 mm, and the maximum compression was 49 mm. The finite element analysis of the valve components showed that the maximum stress of the hyperelastic metal rod was 281 MPa, which was within the hyperelastic range and can be recycled. Performance experiments showed that the probe can work stably with the pH error no more than 0.1. According to the life test, the probe can be used 60 480 times. When the measurement period was set to be 20 min, the probe can meet the service life of two years. In the rumen environment test, the average absolute deviation between manual measurement and system measurement was 0.11, and the maximum absolute deviation was 0.25. The research result can provide technical means and reference for the development of rumen pH monitoring equipment.