A compact linear test rig was designed and built to study the dynamics of in-line inspection techniques and defect characterization within a controlled laboratory environment. It consists of an inspection vehicle propelled by a 5.5 meter linear module having a toothed belt drive. An AC servo drive motor with a closed loop control unit operates the linear module. It is able to maintain a constant travel speeds up to 4.5 meters per second along the 2 meter test sample. The vehicle travel over a ball rail system and guide rail and is capable of high accurate and repeatable positioning. The vehicle is also able to handle various inspection technologies. At this moment the inspection vehicle is equipped with a magnetic flux leakage detection scheme, consisting of neodymium iron boron magnets and coupling steel brushes. The magnets have energy products of 18 to 30 mega-gauss oersted. It also has high sensitivity Hall effect sensors and a data acquisition system. Data acquisition is performed through a commercial mini-notebook attached to the vehicle equipped with a 16 bit analog to digital PC card converter having 16 input channels. Figure 1 shows a schematic drawing of the inspection system. To simplify the construction process a linear shape was adopted since it has no effect on the magnetic behavior of the system.
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