Container integrity monitoring using RF/RFID vibration sensors

Huge stresses that the container items experience during their transportation and handling are mainly responsible for some of the goods to reach their final destination with defects. If the damage of goods can be detected early during their transport, then the driver can possibly take the necessary steps to avert a larger damage to the goods and thus cause significant cost savings. Sensor based approaches are being investigated to provide this early detection capability. This thesis presents an approach that uses wireless vibration sensors based on Zigbee protocol to monitor the integrity and safety of packages during transportation. Two 2-axis accelerometers integrated with T-mote sky wireless nodes were used to monitor the integrity of the packages. Experiments were conducted to discern the vibration patterns resulting from some common mechanical stability losses like wobbling, tilting, colliding and sliding. The experiments used a 1:32 scaled version of RC truck and a proportionately sized container. The vibration patterns under stability losses were captured. It was observed that each type of stability loss can be clearly classified based on the patterns in the vibration data collected.;The vibration signals gathered from the experiments were plotted against time to identify a unique statistical pattern associated with each of the stability loss. A unique pattern was evident from the time series data but the instance at which mechanical stability loss happened was difficult to interpret. This was due to the presence of multiple frequencies in the original data. So wavelets were employed to segregate the extraneous frequencies and concentrate on the pattern associated with the stability loss events so that each stability loss is associated with a specific abnormal (out-of-control) behavioral pattern. A set of rules was developed to determine if, and when, a stability loss event has occurred during the span of time over which the measured data is collected. An algorithm was developed to identify each stability loss immediately after it occurs. A GUI was developed in Matlab and was equipped with the features of the algorithm. The results show that the motion of the container inside the trailer can be accurately monitored based upon the vibration patterns exhibited for each motion type.