Car Laser Roughness Meter Design And Implementation

With the rapid development of highways, the requirements of highway pavement are also increasing. International use IRI (International Roughness Index[3]) as the road roughness index to measure pavement roughness. Currently, China is widely using the standard deviation to measure the pavement roughness. Use standard deviation measure is less accurate than IRI.Invent the pavement roughness measuring instrument is to get the roughness index easily. Firstly, use the 3 m ruler, then use hand push pavement instrumen[12][13], and now use the current widespread laser inertial roughness meter, from the development we knows that, pavement roughness measure is gradually to automation, high efficiency, high-precision direction of evolution[15]. However, in our country still use eight wheel gauge or it upgrade instrument to measure the pavement roughness. Our country cannot meet the international pavement roughness index requirement.Currently, vehicle-mounted inertial flatness meter is widely used internationally, which is installed in the measuring car. During the movement of the measuring car, the laser displacement sensor measuring the vehicle mileage data and odometer get the mileage. Enter the elevation information and mileage information into the computer, then output the analyzed value of IRI. The instrument has a high accuracy. However, this apparatus don't consider of vibration by moving vehicle, which can aspect elevation measured by laser displacement sensor.In this paper, researched the pavement roughness index and smoothness instrument, and then designed a new generation of vehicle-mounted laser roughness meter. In order to obtain accurate road mileage, used the instrument, which can output 3600 signal pulses when the car wheels rotate a circle[36]. The laser displacement sensor is used to measure the pavement longitudinal information. In order to eliminate body vibration effects on the laser sensor, introduction the acceleration sensor to compensate the laser displacement sensor. When Laser displacement sensors measure the road surface elevation, the second integral of acceleration can remove the body vibration displacement, and thus the IRI values calculate is more accurately.In this paper, we analysis the car's encoder signal, then design an encoder signal processing circuit with zero point one millimeter accuracy and have phase discriminator function. The signal after treatment is used as the odometer input. The odometer contains frequency, memory, keyboard, display module. The odometer treatment the input signal, display the real-time mileage and output the frequency signal. Data acquisition card collect the measured data of odometer, laser displacement sensor and acceleration sensor to cache, then real-time send to the host computer. Finally, design implementation of PC data acquisition and calculation procedures, then displayed the IRI values in tabular forms. After several laboratory experiments and real road experiments, we get a multi-set of experimental data. The system is continuous improved based on analysis of experimental data, which verifies the acceleration sensor can reduce the interference of body vibration. Ultimately we make this vehicle-mounted laser roughness meter which can meet the needs of the actual test.