Unexploded Landmines, after wares, represent a serious problem, wastes life and money. Recent research states that contact sensors are promising. In this work, a novel contact sensor for landmine detection is presented. The sensor principle is based on the concept of 2-DOF vibration absorber system (two springs and two masses), to detect the presence of an object (landmine) in sand which is modeled as a third spring. The 3rd spring stiffness (the sand stiffness) can be measured as a function of the vibration absorber frequency ωAbs (the frequency at which the 2nd mass gives minimum amplitude (theoretically proven: zero)) and the 1st mass gives amplitude near to peak. When the sand stiffness changes due to existence of the landmine, the vibration absorber frequency ωAbs changes, and consequently the landmine can be detected. The mathematical proof of the idea is verified by simulation on Matlab and finite element COMSOL Multi-physics. The system parameters are chosen to be appropriate with the sand-landmine stiffness measurement range. The simulation results are optimized to give best sensitivity and linearity of the sensor output. The sensor gives sensitivity of 1559 Hz/(MN/m) and linearity better than 95%. Finally, a detailed design procedure for the contact stiffness sensor for landmine detection is developed. |
