2D Laser Displacement Sensors Research Articles

Air conditioning compressor crankshaft roundness measurement based on a laser profiler

Crankshafts are key components of air conditioning compressors. The good roundness of a crankshaft has positive effects on the operating stability, service life, working efficiency, and noise radiation of the compressor. This study proposes a line point cloud data merging method for measuring crankshaft roundness using a laser profiler. First, a crankshaft roundness measurement system for air conditioning compressors is developed, and a high-accuracy 2D laser displacement sensor is employed to collect the line point cloud data. Second, the steps of the merging method are divided into two parts: (1) the radial merging to eliminate the effects of eccentricity; (2) the circumferential merging to remove overlapping data points of two adjacent profiles. Then, a pin gauge is used to select the point cloud region of the profile line for data merging. Experimental results show that the measurement repeatability of the proposed system can be controlled at the micrometer level. Besides, the roundness measured from the merged data is very close to the roundness measuring instrument measurements, which verifies the accuracy of the measurement system and the validity of the line point data merging algorithm.

Study on the evolution and suppression strategy of the interlayer gap in the drilling of CFRP/Al stacked materials

In aircraft assembly operations, interlayer gap formation during drilling through stacked materials positively affects interlayer burr size. Removing these burrs needs disassembly, deburring, and reassembly, and these processes are time-consuming, expensive, and non-value-added. This study visualizes the real-time variation of the interlayer gap to understand its evolution process and proposes a method of designing feed motion for reducing the interlayer gap. First, a real-time measurement method of the interlayer gap and deflection using a 2D laser displacement sensor is proposed, and the evolution of the interlayer gap in the drilling of stacked materials is described. Besides, a simplified analytical model of the stacks is built to explain the development of interlayer gaps during stack drilling. Then, a variable feed method based on the discrete sine curve is proposed to suppress the interlayer gap. Finally, the drilling experiments of the constant feed and the discretized sine curve feed are performed to compare the change of interlayer gap, and the results showed that the maximum interlayer gap (excluding the effect of chips), the maximum interlayer gap (not excluding the effect of chips), the final interlayer gap and the average interlayer gap was reduced by 25.2 %, 45.1 %, 72.7 % and 35.9 %, respectively. In addition, a small interlayer gap corresponds to a small flexural deformation, which helps reduce the material's stress. The bending deformation of the Al layer is reduced by 54 %, and its maximum stress value can be reduced by 22 %.

The online monitoring system of pantograph slider based on 2D laser displacement sensors

Pantograph slider is the critical component to provide power for the train. The friction between the slider and the contact line will lead to the continuous wear of the slider. Timely monitoring of the slider wear state is of great significance to ensure the safety of train operation. In this paper, we propose an online monitoring system based on 2D laser displacement sensors for the slider wear state. First, two 2D laser displacement sensors are employed to collect the slider data. Second, the original data are processed by algorithms including data pre-processing, data fusion, slider data correction, curve fitting, and wear curve extraction to obtain the wear curve of the slider. Then, five criteria are used to evaluate five wear states. The experimental results shown that the proposed system has good wear detection accuracy and can automatically evaluate the slider wear state, which can meet the needs of on-site maintenance.

Measurement of Aspheric Surfaces Using an Arcuate Region Scanning Method by 2D Laser Displacement Sensor

This study proposes an effective measurement of aspheric surfaces using arcuate region scanning method by 2D laser displacement sensor. In a global coordinate system, the point cloud data of each arcuate region in aspheric surface are obtained successively, coordinated with the rotation of the rotating platform and the transverse movement of the 2D laser displacement sensor in a fixed step size. When scanning different areas, it is necessary to calculate the scanning angle gap and included angle according to different scanning length of arc. Then the aspheric surface error could be calculated through the reconstruction consequence. It can be used for in-situ measurement in the processing stage of aspheric mirrors. We present an experiment compared with the measurement results of PGI to verify the validity of this measurement method.

A Data Splicing Method for Measuring Rail Corrugation Under Pitching Vibration

Rail corrugation is the geometric structure of the rail top surface, and it directly related to the safety and comfort of rail transportation. The monitoring of rail corrugation is the key work for rail maintenance department. Currently, the 2D laser displacement sensor is being used to measure the rail corrugation. However, the 2D sensor is easily affected by pitching vibration under complex measurement environment, which leads to large errors in the final measurement results. For solving the problem of pitching vibration in dynamic measuring rail corrugation, a data splicing method based on deviation recognition and calibration is proposed in this study. Firstly, the blind recognition of sensor deviation is applied to identify the measurement state of sensor in each data sampling. Then, a mapping method is proposed to position the actual repeated measurement interval according to geometric relationship between the deviation angle and the offset in the longitudinal direction. Finally, the modified DTW model is proposed for data registration and the data splicing can be achieved according to the registration results. Extensive experiments are carried on both indoor experimental platform and outdoor platform. The experimental results indicate that our proposed method can accurately recognize the deviation of sensor and can calibrate the deviated data set, and its performance on the rail corrugation measurement under the pitching vibration case outperforms previous data splicing work. Thus, it is with the potential engineering application.

A rail corrugation measurement method based on data splicing

Rail corrugation dynamic measurement techniques are essential to guide rail maintenance and ensuring the safety of railway transportation. However, the effective measuring wavebands covered by traditional techniques are limited. Hence, this paper constructs a novel measurement system by using 2D laser displacement sensors for accurate measuring rail corrugation (2D-RCM). At first, original discontinuous data of rail irregularities are sampled by 2D sensors, and then the accurate restoring of rail corrugation is completed by the coarse-to-refine data splicing method. Coarse splicing mainly extracts and calibrates the data of overlapping measurement area. The refine splicing is achieved by rigid transformation and multiple population genetic algorithm. The validity and repeatability of the 2D-RCM is tested by extensive experiments. The experimental results demonstrate that it owns high-precision on measuring the wavebands of corrugation varied from 10 mm to 1 m, and robust to deviations of 2D sensors and pitching vibrations of the 2D-RCM system.

Razvoj automatizovanog i namenskog mernog sistema kod dimenzija cevi korišćenjem 1d i 2d laserskog senzora pomaka

The measurement of tube dimensions such as Inner Diameter (ID), Outer Diameter (OD), length, chamfer angle and OD run-out with the help of conventional measuring instruments requires skilled operators. Human operated inspection system is having a high possibility of uncertainty in the inspection of midsize and large batch production of tubes. Industries require high precision and high-speed with low uncertainty in the measurements for ensuring the better quality delivery of the tube product. This work aims to present the development of an automated and dedicated inspection system that inspects ID, OD, length, chamfer angle, and OD run-out of tubular components (such as camshafts, air-suspension tubes, etc.) using 1D and 2D laser displacement sensors. The ID, OD, and chamfer angle (inner chamfer angle on both ends of the tube) of the tubes are measured using 2D laser displacement sensor. The 1D laser displacement sensors were used to measure the run-out and length of the tubes. Calibration of sensors with the master tube was done and compared with the manual inspection method.

点云频域配准的双目双线结构光列车轮对检测

点云频域配准的双目双线结构光列车轮对检测

Online adaptive measurement and adjustment for flexible part during high precision drilling process

Shape of flexible part is easy to be out of tolerances due to deformations in the clamping and machining process. These deformations are generated randomly and hard to be predicted. Surface normal drilling and countersinking of flexible part is commonly necessary in aircraft assembly process. An online high precision surface normal measurement and cutter orientation compensation method is developed for adaptively drilling of flexible part in this paper. During the process of normal measurement and adjustment, the distance from tool nose to drilling point is accurately measured and adjusted synchronously, which is critical for countersinking. To accurately measure the current normal of the deformed workpiece, two 2D laser displacement sensors are applied to measure the surface profiles of the workpiece and sample two sets of geometrical points each time. Two crossed spatial curves are respectively fitted by the two sets of geometrical points, and the surface normal at the intersection point of the crossed curves is computed. After the deviation between the measured normal and tool orientation is calculated, an online compensation method is used to eliminate the deviation and meet the perpendicularity requirement of the cutter axis to the workpiece surface, and the distance from tool nose to drilling point is measured and adjusted to the setting value synchronously. The compensation method is based on the kinematic transformation of a five-axis machine tool and is implemented by NC compensation. Simulations and experiments are conducted to validate the feasibility and effectiveness of the online adaptive measurement and adjustment method.

Online detection system for wheel-set size of rail vehicle based on 2D laser displacement sensors

The real-time detection of wheel-set size, the most significant technical parameter during vehicle operation, has important implications for ensuring the safety of wheel running. Based on laser ranging, an online detection system of the wheel size installed below the track is developed. Eight two-dimensional (2D) laser displacement sensors are applied to detect the wheel-set size including wheel flange and tread profile. A digital I/O card is utilized to generate synchronous signals which guarantee simultaneous working of all sensors. Least square based curve fitting and pick-up algorithm of tread feature-points are used to process the measured data and calculate the flange width, flange height and wheel diameter. The experimental results show that the online detection system of wheel-set size can realize the non-contact, dynamic and real-time measurement of wheel-set parameters. When train running speed is under 5km/h and sampling frequency is 30Hz, the detection accuracy of flange width and height is ±0.2mm and the detection accuracy of wheel diameter is ±0.5mm, which can meet the requirements of maintenance operation.

평면 구조물의 단일점 일치를 이용한 2차원 레이저 거리감지센서의 자동 캘리브레이션

In this paper, we introduce an autonomous calibration method for a 2D laser displacement sensor (e.g. laser vision sensor and laser range finder) by matching a single point on a flat structure. Many arc welding robots install a 2D laser displacement sensor to expand their application by recognizing their environment (e.g. base metal and seam). In such systems, sensing data should be transformed to the robot's coordinates, and the geometric relation (i.e. rotation and translation) between the robot's coordinates and sensor coordinates should be known for the transformation. Calibration means the inference process of geometric relation between the sensor and robot. Generally, the matching of more than 3 points is required to infer the geometric relation. However, we introduce a novel method to calibrate using only 1 point matching and use a specific flat structure (i.e. circular hole) which enables us to find the geometric relation with a single point matching. We make the rotation component of the calibration results as a constant to use only a single point by moving a robot to a specific pose. The flat structure can be installed easily in a manufacturing site, because the structure does not have a volume (i.e. almost 2D structure). The calibration process is fully autonomous and does not need any manual operation. A robot which installed the sensor moves to the specific pose by sensing features of the circular hole such as length of chord and center position of the chord. We show the precision of the proposed method by performing repetitive experiments in various situations. Furthermore, we applied the result of the proposed method to sensor based seam tracking with a robot, and report the difference of the robot's TCP (Tool Center Point) trajectory. This experiment shows that the proposed method ensures precision.

In-Process Visualisation for Deformation Monitoring and Analysis of Sheet Metal Forming Processes

In this paper, a visualisation system will be discussed that can be used to capture the deformation profile of the sheet blank during sheet metal forming processes, such as deep drawing and shape forming. The visualisation system utilizes a 2D laser displacement sensor for deformation profile acquisition. The sensor is embedded in the die and the laser propagates through the die to detect the profile change of the specimen concealed in the die during operation. The captured profile data will be collected, manipulated and transferred to a monitor for display via a controller. This visualisation of the deformation profile will provide engineers and researchers with an intuitive means of analysing and diagnosing the deformation process during sheet metal forming.

Chemical speciation of chlorine in particulate matter by wavelength-dispersive PIXE technique

Chemical speciation of chlorine (Cl) in atmospheric particulate matter (APM) was performed by using a wavelength-dispersive PIXE spectrograph based on high-resolution measurement of Cl-Kβ emission. Samples of atmospheric particles were size-fractioned and collected by a cascade impactor at an urban area in Tokyo. The target position with respect to the spectrograph was precisely adjusted by a 2D laser displacement sensor to achieve high detection efficiency. The samples were irradiated with 2 MeV protons from a tandem electrostatic accelerator. The beam current was 300–500 nA. During the irradiation, the target was cooled by liquid nitrogen to avoid the evaporation of volatile Cl compounds. The measured spectra for the NaCl standard samples clearly showed the Cl-Kβ series composed of the Kβ 1 and the satellite Kβ x, Kβ 5 lines. From the measured X-ray yields, it was found that the chemical speciation of samples with Cl concentrations as low as ≈1% is possible by this method. The Cl-Kβ series were also successfully observed in the case of APM samples with particle sizes of 11.0–2.1 μm. The spectra shapes of the NaCl standard samples and an APM sample were slightly different from each other, because of some possible mixing of non-sea salt component in the APM sample.

A14 Machining Error Compensation Utilizing On-the-machine Measurement of machined surface(Digital design and digital manufacturing (CAD/CAM))

Recently, the demand for precision machining of dies and molds with complex shapes has been increasing. Yet, even as the use of CNC machining tools increases in the area of precision machining, machining error compensation is still necessary to meet the machining accuracy requirements. Machining error compensation, however, is an operation that not only demands a highly-skilled machinist, but also requires a large amount of time and money. Transporting a workpiece is time consuming and costly, and re-clamping the workpiece causes positioning errors, especially when it is of substantial size and weight. Therefore, demands for an On-the-machine Measurement have been increasing. This paper describes an On-the-machine Measurement device that consists of a 2D laser displacement sensor. This device attaches to a machining tool using magnetic clamps, and is equipped with special features that permit non-contact scanning measurement, multi-point measurements, high-speed measurements, and the measurement of both the vertical surface and the steep slope.