The CAPTIF simulated loading and vehicle emulator (SLAVE) is controlled by an Alan Bradley SLC500 PLC(external link) controller. The PLC program operates the electrical and hydraulic motors, pumps and actuators. It also monitors numerous safety sensors and will shut the machine down if a fault is detected. A wifi SCADA system allows an operator to send instructions to the PLC from a shore based PC in the control room. This PC runs a supervisory Labview(external link) program.
A system has been developed at CAPTIF to monitor and analyse the dynamic wheel force behaviour of the SLAVE ‘vehicles’. The system is able to monitor the dynamic forces that are imparted to a pavement and the dynamic behaviour of the vehicle itself.
The system comprises of four PCB(external link) 353B51 +-10g accelerometers, one mounted on the chassis and one mounted on the axle on each of the two SLAVE vehicles. Between the axle and chassis on each vehicle there is mounted a Shaevitz EC-DC-2000 +-50mm LVDT displacement sensor.
The sensors are wired from the vehicles back to a NI SC2345 signal conditioning chassis. The SC2345 is controlled from a NI PXI1050 instrumentation computer. This computer runs Labview(external link) software to monitor and record the sensors. There is also a Labview program to calculate the dynamic forces from the accelerometer data. The instrumentation computer is operated over a wifi link to a control room PC running Windows Remote Desktop.
CAPTIF uses a Laser Profiler developed by the Australian Road Research Board (ARRB) to measure the longitudinal profile of the pavement surface. The shape of the surface and macro-texture are recorded at speeds up to 50km/Hr. The laser has a measurement range of +-35mm with a standoff distance of 310mm. Incorporated into the laser hardware is an accelerometer which is used to offset the laser measurement against the bounce of the vehicle. The ARRB laser is routed to a NI SC2345 signal conditioning chassis which is controlled from a NI PXI1050 instrumentation computer. This computer runs Labview(external link) software to monitor, record and filter the sensors. The data is the processed using ProVal(external link) 3.6 software. This software calculates a roughness index for the pavement.
