Research On Low Power Wireless Laser Image Deflection Automatic Monitoring System

The deflection is an important parameter of bridge safety evaluation. Hence, many effective methods were put forward to measure the deflection by engineers. The laser image method was used widely because of its high precision and distant measurement and so on. However, Existing laser image deflection monitoring systems still exist some disadvantages, such as high power consumption, complex wiring, can not be used in strong interference environment. Therefore, the main purpose of this paper is to design specific technical solutions and verify their effectiveness and reliability by experiments.For the issue of high power consumption, this paper designed a novel dynamic power management technology. The explanation is as follows: (1) Use the simplest low power embedded data collector with ARM microprocessor instead of industrial personal computer. And coordinate the work of electronic components by intelligent control strategy. The two methods can reduce the system's power consumption. (2) Achieve mode switching between high-power mode and low-power mode, instead of traditional single high power mode. This method can prevent the damage of electronic components because of their high workload in the long term. (3) Use an intermittent power supply manager (called Secretary Mechanism Manager(SMM) by us) to manage element working time. As the measurement command arrives, SMM opens the power of systems'components relevant to measurement task, but closes their power as the task is completed. And SMM opens them again with the advent of next command. This method not only reduces the systems'power, but also avoids the aging and damage of system's components because of long-term work with power.For the issue of complex wiring, the GPRS remote wireless technology is used in data remote transmission, and SRWF-501 wireless module is used in short-range communication among systems'components. Hence, System's components can be installed wirelessly, and data was transmitted wirelessly. And communication data set different encapsulation protocol. This method can avoid large wiring and guaranteed the reliability of data transmission.For the issue of strong interference, this paper designed a difference operation spot center location algorithm. A foreground image with laser spot takes away another background image without laser spot means dying background noises. Median filtering, opening and closing operation are used to filter the small noise in the spot image. This method improves the anti-interference of algorithm. Circle fitting operation with appropriate gradient and spot testing operation can improve the location precision of laser spot center.With above three technology schemes, this paper designed a novel laser image deflection monitoring system, composed of laser emitter, half reflecting target, embedded data collector, Secretary Mechanism Manager, Scene Master Control Manager, GPRS Transceiver, calibration module. Finally, based on the completion of software designing and hardware designing, the algorithm experiment, power saving experiment and system performance experiment are done in the laboratory and bridges. Experiment results demonstrate the high precision, low power consumption, strong anti-interference, data wireless transmission, and continue online measurement of the new system.