Figure 12Results of shaking table test: (a) sine wave 2Hz, (b) sine wave 4Hz, (c) random case 1, and (d) random case 2.3.2. Time Synchronization TestAnother shaking test verified the time synchronization algorithm used in this study. Figure 13 shows the configuration of the time synchronization test using a shaking table. In this test, three laptop PCs, one master and two slaves, Dasatinib side effects were used, and the typical specifications as follows: Lenovo R61, Intel Core Duo 2.4MHz, 160 of HDD, 2GB of RAM, Acer Asprire 5580, Intel Core 2-Duo 1.66MHz, 160GB of HDD, 3GB of RAM, Lenovo X201 Tablet, Intel Core i7-640LM 2.13MHz, 320GB of HDD, 4GB of RAM. Figure 13Experimental setup for the time synchronization test.Lenovo X201 Tablet was used as the master PC. Two subsystems simultaneously tracked the same target panel at a distance of 16 meters.

All the subsystems were connected to master PC via a wireless LAN access point placed 10 meters away from all the PCs. The distance between the systems was determined considering the performance of telescopic lenses and camcorders. The software, including the time synchronization algorithm, was installed on both the master and the slave PCs.The system time of the slave PCs were synchronized based on the internal time clock of the master PC. For verifying the accuracy of the salve PCs’ internal time clocks, each slave PC generated voltage signals through its serial port based on its internal clock. An oscilloscope connected to the serial ports of the slave PCs monitored the voltage signals generated by the slave PCs, and the time lag between the two slave PCs was determined by referring to the voltage signals.

The time lag of the subsystems were checked every 60s and found a time delay of 1.54ms initially after the time synchronization process. The time delay increased with time due to differences in the accuracy of the internal time clocks of the slave PCs, as shown in Figure 14(a). In this experiment, the time lag increased 1.66ms an average of every 60s. Thus, to avoid increasing in the time lag, the time synchronization process was Batimastat performed every 60s. Figure 14(b) compares the displacements measured from the LVDT with those obtained from the system with the periodical time synchronization process. With sinusoidal excitation of 1Hz, the displacements obtained from the system using different Laptop configurations were in good agreement with the LVDT measurements.Figure 14Result of the time synchronization test: (a) time lag between the subsystems and (b) displacement with an excitation frequency of 1Hz.4. Conclusions In this study, an advanced synchronized multipoint vision-based system using an image processing technique has been successfully developed for a real-time dynamic displacement measurement.