SBIR-STTR Award

The deployment of US military forces often requires aircraft operations on runways of unknown construction, roughness, and load carrying capacities not only in UAS but also in foreign countries. Current FWD, DCP and RWD cannot satisfy the mission requirement. The air force is looking for an air droppable lighter weight RWD that can rapidly collect continuous data using sensor technologies. In this proposal, a lightweight RWD with same tire pressure as the big RWD is proposed. Instead of using a rotating mirror an innovative sensor array using linear IR laser diode array and detector array sharing a common optical axis is designed. One sensor array will be put at a location under truck before loading and the other will be put after loading to measure the perpendicular distance from the laser to the runway. Two arrays will be mounted on a H-shape suspension platform with the same height and will be aligned each other precisely. By subtracting the data from two sensor arrays we not only can quantitatively measure the deflection of the runway but also can eliminate all systematic errors caused by vibration etc. If we use our unique parabolic LED array to replace the laser diode array, the total saving will be over $10,000 and the system reliability can be largely increased. In addition to the above sensor arrays, a stereo camera using linear CCD & LIR fused arrays is also designed to not only visualize the runway deformation after loading but also detect the void underneath the runway. Since all optical sensors cannot penetrate the runway, simple microwave impulse radar is also designed to show the void and construction under the runway. Because the RWD is air droppable it should not use a driver, therefore a novel robot is designed to operate the sensors in the RWD and drive the RWD to any place on the runway, and the data will be wirelessly sent to a remote computer for analysis. After finishing the runway survey the RWD will return to the start point and wait for pickup by the helicopter. In order to calibrate the RWD data, our automatic FWD and DCP operated by the robot and developed in one phase-I and two phase-II projects for Army and SOF will be used to measure the runway stiffness and CBR at certain points, thus the relationship between the RWD deflection and the runway strength can be established. Not only all above new sensor prototypes but also a bench scale RWD prototype will be delivered to the Air Force in phase-I.

During the Phase-I research we only spent 6 months (not 9 months) an air droppable rolling weight deflectormeter (ADRWD) was built and a conceptual demo at a small airport was successfully conducted. The Phase-II main objective is to refine the Phase-I design and build a lightweight working ADRWD prototype that can accurately measure the runway deflection and correctly evaluate the load carrying capacity of any runway to give a go or not go answer for a class of airplane. In order to realize this goal we have deeply analyzed those big RWDs and found that there are 7 serious problems must be overcome: (1) the measurement assumptions and calculating equations are questionable, (2) it is impossible to measure the deflection at the same point in the two-step and two-point procedure, (3) the two-step procedure will get large error from the truck vibration and pavement unevenness, (4) the two-point measurement cannot get the deflection basin, (5) the error from support beam bending should be simply removed, (6) the error from different sensor heights should be eliminated, (7) the effects of the dust, dirt and moisture to the sensor window should be prevented. The key of our new design to solve these problems is to put a sensor between the front tire and rear tire without deflection and put 3 sensors behind the rear tire with deflection and sample their data simultaneously then make average and subtraction to get the relative deflection basin and eliminate the errors from pavement unevenness, truck vibration, test not at exact point, and so on. In Phase-II, we will build and deliver 3 prototypes: (1) use high accuracy laser rangefinders with inclinometer, speed/distance encoder, GPS and ground marker to get the deflection profile, (2) add the thermal scanner and ground penetration radar to the above for layer analysis, (3) add a portable falling weight deflectometer to the system (1) for test verification at discrete points. Since there is no software can be adopted from existing RWD, two new software packages will be developed: (1) automatic high speed sensor operation and data collection software and ASIC, (2) backcalculation and runway load bearing capacity estimation equations and data analysis software to get a 3-D runway deflection and defects profile with ground marks as a function of space and time. In addition to the airport application, the portable ADRWD will be used for highways, gas stations and many other places; the technology related with laser rangefinder, IR, Radar, etc. will be used for railway defects inspection and missile defense and their prototypes will be built up in Phase-II as a part of commercial applications.

Keywords:
Rolling Weight Deflectometer, Air Droppable Rwd, Deflection Basin, Laser Rangefinder, Inclinometer, Infrared Scanner, Ground Penetration Radar, Fallin