Design Of Sleeping Position Detection System Based On Resistive Sensor Array

Tactile sensor arrays are widely used in intelligent robots,wearable devices,medical health and other fields to help humans indirectly obtain tactile information such as temperature and pressure.The tactile sensor array mainly obtains information by contacting the measured object,and it is necessary to find out the contact area in the array.For example,in terms of sleeping posture detection,the shape of the contact area between the human body and the sensor array can be used to identify the sleeping posture.For sleeping posture recognition,this paper designs a sleeping posture sensing pad based on hybrid sensor array containing pressure-sensitive and thermal-sensitive sensors,and processes the pressure data and temperature data collected by the sensing pad to identify the current contact area between the human body and the sensing pad.Firstly,a sleeping posture sensing pad is designed based on a resistive hybrid sensor array.Secondly,a threshold segmentation and frame-to-frame difference fusion algorithm is proposed to identify the contact area between the human body and the thermal sensor array.Then,a sleeping posture detection system is built using the posture sensing pad and the contact area recognition method.Finally,an evaluation experiment is carried out on the designed sleeping posture detection system.The contents and achievements of this work are organized are as follows:1.A sleeping posture sensing pad is designed based on a resistive hybrid sensor array.Investigating the sleeping posture of the human body,it is found that the contact probability between the human body and different areas of the sleeping pad is different,and the sleeping posture can be effectively identified only by the shape of the contact area between the torso and the upper half of the upper arm of the human body and the sleeping pad.The conventional sensor arrays used to identify sleeping postures are mostly pressure-sensitive sensor arrays that are evenly distributed in space,which cannot improve the data acquisition resolution of local key areas.In order to meet the needs of sleeping posture recognition,this paper designs a sleeping posture sensing pad with replaceable sensitive units based on a non-uniformly distributed sensor array.The overall array size of the sensing pad is 16×16,in which the high-probability contact area with the human body is set to a higher density,and the small-probability contact area with the human body is set to a lower density,and the size of each area is determined according to the size of the human body.At the same time,in order to reduce the fabrication cost of the sensing pad and ensure the sensing performance,a large number of low-cost thermistors and a small number of expensive varistors are mixed.2.A threshold segmentation and frame-to-frame difference fusion algorithm is proposed to identify the current contact area between the human body and the thermal sensor array.The results of previous studies have shown that when the human body is in contact with the thermal sensor in the sensor array,the temperature of the sensor rises rapidly because the heat exchange method is mainly heat conduction.After the human body is separated from the thermal sensor in the sensor array,the temperature of the sensor drops slowly because the heat exchange method is mainly thermal radiation.Since the initial temperature of the thermal sensor array in the sensing pad is the ambient temperature,the threshold selection is affected by the ambient temperature when using the threshold segmentation method,and the maximum inter-class variance method is used to adaptively select the segmentation threshold.Due to the slow response speed of the thermal sensor array in the sensing pad,simply using the threshold method to identify the contact area may cause misjudgment,the frame-toframe difference method is used to track the temperature change of the array.The pressure-sensitive sensor in the sensing pad has a faster response speed,and can be used to make a quick judgment on whether the sensing pad is in contact with the human body.3.Based on the designed sleeping posture sensing pad and contact area recognition method,a sleeping posture detection system is built.The existing resistive sensor array readout methods were evaluated,and the improved zero-potential method,which has a high scan rate,was selected,and the data acquisition subsystem was designed based on the STM32F103 microcontroller to realize the data acquisition of the sleeping posture sensing pad.A host computer software is developed based on MFC to process the data collected by the sensing pad and identify the contact area,and realizes functions such as temperature and pressure data display,temperature and pressure distribution map drawing,sleeping posture shape display,data storage.4.The designed sleeping posture detection system is evaluated by experiments.The experimental results show that the sleeping posture sensing pad has good flexibility and can effectively sense temperature and pressure;the non-uniformly distributed sensor array can effectively ensure the spatial resolution of local key areas;the proposed contact area identification method can quickly identify the current contact area between the thermal sensor array and the human body;the low-cost sleeping posture sensing pad can effectively identify the sleeping posture.