基于手持式激光测距仪的大尺寸测量应用研究

提出了一种基于手持式激光测距仪的大尺寸测量系统及方法.分别通过以手持式激光测距仪和增最式光电编码器为核心的测距及测角单元获得目标测量点的极坐标;再南运动控制器、驱动器、执行电机等构成的伺服控制系统,带动测距仪完成工件的扫描测量;然后在极坐标系下利用最小二乘拟合法进行数据处理,并对一钢质圆环内径进行了测量,测量半径标准差为0.2mm.最后,研究了多站组合测量模式及坐标配准方法.     

Dense range map reconstruction from a versatile robotic sensor system with an active trinocular vision and a passive binocular vision.

One major research issue associated with 3D perception by robotic systems is the creation of efficient sensor systems that can generate dense range maps reliably. A visual sensor system for robotic applications is developed that is inherently equipped with two types of sensor, an active trinocular vision and a passive stereo vision. Unlike in conventional active vision systems that use a large number of images with variations of projected patterns for dense range map acquisition or from conventional passive vision systems that work well on specific environments with sufficient feature information, a cooperative bidirectional sensor fusion method for this visual sensor system enables us to acquire a reliable dense range map using active and passive information simultaneously. The fusion algorithms are composed of two parts, one in which the passive stereo vision helps active vision and the other in which the active trinocular vision helps the passive one. The first part matches the laser patterns in stereo laser images with the help of intensity images; the second part utilizes an information fusion technique using the dynamic programming method in which image regions between laser patterns are matched pixel-by-pixel with help of the fusion results obtained in the first part. To determine how the proposed sensor system and fusion algorithms can work in real applications, the sensor system is implemented on a robotic system, and the proposed algorithms are applied. A series of experimental tests is performed for a variety of configurations of robot and environments. The performance of the sensor system is discussed in detail.     

Compact and high-precision range finder with wide dynamic range andits application

Described is a new range finder using a self-mixing laser diode (SM-LD). The range finder has a high accuracy of ±0.15% and a wide dynamic range of 0.2-1 m using only one sensor head. Compared to ultrasonic range finders, the light beam of this laser range finder can be focused and scanned. The feasibility study shows a possible application of the range finder to a visual sensor of a robot. The proposed range finder has been successfully applied as an infrared (IR) active type range finder of a single-lens reflex camera     

Flying triangulation--an optical 3D sensor for the motion-robust acquisition of complex objects

Three-dimensional (3D) shape acquisition is difficult if an all-around measurement of an object is desired or if a relative motion between object and sensor is unavoidable. An optical sensor principle is presented-we call it "flying triangulation"-that enables a motion-robust acquisition of 3D surface topography. It combines a simple handheld sensor with sophisticated registration algorithms. An easy acquisition of complex objects is possible-just by freely hand-guiding the sensor around the object. Real-time feedback of the sequential measurement results enables a comfortable handling for the user. No tracking is necessary. In contrast to most other eligible sensors, the presented sensor generates 3D data from each single camera image.     

Backward-mode multiwavelength photoacoustic scanner using a planar Fabry-Perot polymer film ultrasound sensor for high-resolution three-dimensional imaging of biological tissues

A multiwavelength backward-mode planar photoacoustic scanner for 3D imaging of soft tissues to depths of several millimeters with a spatial resolution in the tens to hundreds of micrometers range is described. The system comprises a tunable optical parametric oscillator laser system that provides nanosecond laser pulses between 600 and 1200 nm for generating the photoacoustic signals and an optical ultrasound mapping system based upon a Fabry-Perot polymer film sensor for detecting them. The system enables photoacoustic signals to be mapped in 2D over a 50 mm diameter aperture in steps of 10 microm with an optically defined element size of 64 microm. Two sensors were used, one with a 22 microm thick polymer film spacer and the other with a 38 mum thick spacer providing -3 dB acoustic bandwidths of 39 and 22 MHz, respectively. The measured noise equivalent pressure of the 38 microm sensor was 0.21 kPa over a 20 MHz measurement bandwidth. The instrument line-spread function (LSF) was measured as a function of position and the minimum lateral and vertical LSFs found to be 38 and 15 microm, respectively. To demonstrate the ability of the system to provide high-resolution 3D images, a range of absorbing objects were imaged. Among these was a blood vessel phantom that comprised a network of blood filled tubes of diameters ranging from 62 to 300 microm immersed in an optically scattering liquid. In addition, to demonstrate the applicability of the system to spectroscopic imaging, a phantom comprising tubes filled with dyes of different spectral characteristics was imaged at a range of wavelengths. It is considered that this type of instrument may provide a practicable alternative to piezoelectric-based photoacoustic systems for high-resolution structural and functional imaging of the skin microvasculature and other superficial structures.     

3-D measurements using a video camera and a range finder

The geometric modeling of the environment can be carried out by incorporating a video camera range finder. When the quality of images is poor, the range finder, which is mounted on a site and azimuth rotation turret, brings an indispensable complement by measures of depth. The purpose of this paper is to build a geometric database of a three-dimensional (3-D) world in telerobotic applications. The calibration of the sensor system is presented by focusing on models of the range finder and methods we studied to determine them. The experimental results allow the evaluation of models and methods in terms of accuracy and stability. We show how the problem of setting up the 3-D geometric database can be solved by cooperation between human operator and sensors. Two cases are treated for database updating: determining the right position of known objects and inserting an embodying volume to model unknown objects, The experimental results concerning object modeling of cylindrical and polyhedral pattern and are given in terms of volume dimensions and position errors     

Shack-Hartmann wavefront sensing with elongated sodium laser beacons: centroiding versus matched filtering

We describe modeling and simulation results for the Thirty Meter Telescope on the degradation of sodium laser guide star Shack-Hartmann wavefront sensor measurement accuracy that will occur due to the spatial structure and temporal variations of the mesospheric sodium layer. By using a contiguous set of lidar measurements of the sodium profile, the performance of a standard centroid and of a more refined noise-optimal matched filter spot position estimation algorithm is analyzed and compared for a nominal mean signal level equal to 1000 photodetected electrons per subaperture per integration time, as a function of subaperture to laser launch telescope distance and CCD pixel readout noise. Both algorithms are compared in terms of their rms spot position estimation error due to noise, their associated wavefront error when implemented on the Thirty Meter Telescope facility adaptive optics system, their linear dynamic range, and their bias when detuned from the current sodium profile.     

Sensing strategy to detect wrinkles in components

Wrinkling is a common phenomena in a range of manufacturing processes. The ability to sense the occurrence of wrinkles is useful in deep-drawn sheet metal forming to make on-line closed-loop feedback control of the binder forces feasible. This would lead to higher productivity and better-quality of deep-drawn components. The sensing of wrinkles as they occur in manufacturing applications is considered here. The sensors used are of a noncontact type, either a fiber optic displacement sensor or a laser range finder. The size constraint is particularly relevant for the on-line sensing application. The use of two displacement sensors to detect the wrinkle and estimate its peak amplitude is explained. The sensing strategy is experimentally verified     

A Method of Feature Extraction on Recovery Curves for Fast Recognition Application With Metal Oxide Gas Sensor Array

In the fast recognition applications of electronic nose, not only the recognition time is important, another parameter response-recovery time also needs to be considered. The response-recovery time could be defined as the time from the beginning of measuring one sample to the state of being ready for new sample measurement. An electronic nose with nine metal oxide (MOX) gas sensors and a method of feature extraction on sensor recovery curves were presented in this paper. The electronic nose was designed to reduce the recognition time and the response-recovery time synchronously. In the sampling module of the electronic nose, there were two pumps, which could let the sensor quickly recovered. The feature extraction method could rapidly extract features from sensor recovery curves with robust information. Nine volatile organic compounds (VOCs) gas samples were measured with the electronic nose. The correct recognition ratios under 10 and 15 s recognition time are 91.0% and 95.8%, respectively. The mean response-recovery time of these sensors in the measurements was 33.5 s, which was about 42.7% of the response-recovery time in typical traditional gas sample measurements. The results show that the proposed feature extraction method could extract robust information with short recognition time and response-recovery time.     

Simple three-dimensional laser angle sensor for three-dimensional small-angle measurement

A simple three-dimensional (3D) laser angle sensor for 3D measurement of small angles based on the diffraction theorem and on ray optics analysis is presented. The possibility of using position-sensitive detectors and a reflective diffraction grating to develop a 3D angle sensor was investigated and a prototype 3D laser angle sensor was designed and built. The system is composed of a laser diode, two position-sensitive detectors, and a reflective diffraction grating. The diffraction grating, mounted upon the rotational center of a 3D rotational stage, divides an incident laser beam into several diffracted rays, and two position-sensitive detectors are set up for detecting the positions of +/-1st-order diffracted rays. According to the optical path relationship between the three angular motions and the output coordinates of the two position-sensitive detectors, the 3D angles can be obtained through kinematic analysis. The experimental results show the feasibility of the proposed 3D laser angular sensor. Use of this system as an instrument for high-resolution measurement of small-angle rotation is proposed.     

Hand-held 3D scanner for surface-shape measurement without sensor pose tracking or surface markers

Current hand-held three-dimensional (3D) scanners for surface-shape measurement require sensor-tracking devices or surface markers to determine the position and orientation (pose) of the sensor at different viewpoints, thus limiting their functionality. This paper presents a hand-held 3D scanner without sensor tracking or surface markers. Multiple planes of light are simultaneously projected onto an object surface to provide sufficient surface information to enable surface fitting and fine interpolation between acquired data points. In surface scanning, the hand-held scanner acquires a sequence of dense overlapping range-images from different viewpoints with enough overlap between range views and abundant information within each range view to permit registration of all acquired data into a single 3D model. Calibration is performed by closed-form surface-fitting to map 2D image coordinates to 3D calibration-object coordinates. Conical diffraction adjustment corrects for projected-line curvature. The measurement accuracy was suitable for applications such as reverse engineering, and virtual and physical prototyping.     

相似度距离耦合角度径向变换的图像配准算法

目的为了解决当前图像配准算法因利用l1距离或l2距离相似度测量手段来完成图像特征点匹配,使其忽略了相位信息,难以有效消除高斯噪声的影响,使其配准精度与效率不佳不足的问题。方法提出最优相似度距离耦合角度径向变换的抗噪图像配准算法。首先引入角度径向变换,以降低算法复杂度,快速提取图像的特征点。然后联合图像的幅度和相位信息,基于欧式距离测度,定义最优相似度距离测量模型,通过求解其全局最小值,对特征点完成匹配,提高算法的抗噪性能。最后将图像分割为内点与外点,择取6个内点,通过计算其变换矩的几何配准误差,改进随机样本一致策略,对匹配进行提纯,消除误配。结果仿真实验结果显示,与当前基于l1距离或l2距离相似度测量的图像配准技术相比,该算法具有更强的抗高斯噪声性能和更高的匹配精度,且算法时耗最短。结论所提算法能够精确完成图像特征配准。     

基于扩展卡尔曼滤波的轮式移动机器人定位技术

针对单一传感器或现有多传感系统在信息传递提取上的不足,应用一种信息融合方法,对机器人进行相对定位与绝对定位的融合分析,得出机器人的最优位置信息,最终实现了移动机器人的精确定位。首先,采用码盘、陀螺仪进行机器人相对定位,采用激光雷达进行机器人绝对定位;其次,建立环境地图、传感器及机器人运动模型;最后,以扩展卡尔曼滤波作为多传感器融合技术,建立多传感器信息融合模型,实现精确定位。     

Energy extraction for a self-energized pressure sensor

With the prolific use of sensors for manufacturing process monitoring, proper power supply and installation scheme has assumed an increasingly central role. Cable-based sensor powering, while commonly used on the factory floor, faces various real-world constraints. It is desirable that the power required by the sensors be "extracted" from the process being monitored itself to enable "self-energized" sensing. Such a novel design for a wireless pressure sensor for injection molding process monitoring is presented in this paper. The focus is on the energy extraction mechanism from the pressure transients exerted by the polymer melt during the injection molding process to power a piezoelectric signal transmitter, which digitally reconstructs the polymer melt pressure profile. An analytical model examining the energy conversion mechanism due to interactions between the mechanical strain and the electric field developed within the energy extraction device is first established. Using a coupled-field analysis, a numerical model is then developed to evaluate the electromechanical properties dependent upon the geometric effects of the energy extraction device. The two models are then compared with experimental results obtained from a functional prototype to evaluate the relevance of the assumptions made and the modeling accuracy. Preliminary experimental results describing the integration of the energy extraction device with the ultrasonic transmitter and the subsequent transmission of pressure information acoustically through a block of steel are also presented. The presented design introduces a new generation of self-energized sensors that can be employed for the condition monitoring of a wide range of high-energy manufacturing processes.     

A feasible noise estimation algorithm for resource-limited sensor systems

Fault tolerance and self-checking capabilities are key features of modern smart sensors, which often require the integration of additional signal processing facilities. In high-volume production areas such as automotive applications, however, optimized controllers are employed that typically have only limited computing resources. This paper examines several algorithms to assess the noise in a quasi-closed loop measurement channel under the assumption that the stimulus can be held constant during noise measurement. Starting from the definition of standard deviation, we propose several modifications and obtain an easy-to-implement algorithm relying entirely on addition and shift operations. Numerical experiments based on simulated and measured noise verify the practicability of the approach. The proposed algorithm has already been successfully implemented in a capacitive angular speed sensor system for automotive applications.     

白车身视觉检测系统中多类型传感器全局校准技术

针对白车身视觉检测系统中传感器数量多、种类各异、分布空间大、位置关系复杂等问题,提出了一种适用于工业现场的多视觉传感器全局校准技术。基于坐标系间接统一法,设计多个精密立体靶标作为坐标系转换中介,利用激光跟踪仪获取现场校准数据,在单位四元数数学模型的基础上,求解两坐标系间最优转换矩阵,将固定式传感器和柔性传感器的测量坐标系统一到全局坐标系。该方法已在某企业在线测量项目中成功应用,现场只需完成传感器坐标系与全局坐标系转换关系标定,降低了复杂现场环境对多传感器全局校准的限制,简化了校准过程,提高了环境适应性,校准后检测系统各向测量精度均优于±0.2 mm,满足白车身在线测量精度要求。     

Side-line tunable laser transmitter for differential absorption lidar measurements of CO2: design and application to atmospheric measurements

A 2 microm wavelength, 90 mJ, 5 Hz pulsed Ho laser is described with wavelength control to precisely tune and lock the wavelength at a desired offset up to 2.9 GHz from the center of a CO(2) absorption line. Once detuned from the line center the laser wavelength is actively locked to keep the wavelength within 1.9 MHz standard deviation about the setpoint. This wavelength control allows optimization of the optical depth for a differential absorption lidar (DIAL) measuring atmospheric CO(2) concentrations. The laser transmitter has been coupled with a coherent heterodyne receiver for measurements of CO(2) concentration using aerosol backscatter; wind and aerosols are also measured with the same lidar and provide useful additional information on atmospheric structure. Range-resolved CO(2) measurements were made with <2.4% standard deviation using 500 m range bins and 6.7 min? (1000 pulse pairs) integration time. Measurement of a horizontal column showed a precision of the CO(2) concentration to <0.7% standard deviation using a 30 min? (4500 pulse pairs) integration time, and comparison with a collocated in situ sensor showed the DIAL to measure the same trend of a diurnal variation and to detect shorter time scale CO(2) perturbations. For vertical column measurements the lidar was setup at the WLEF tall tower site in Wisconsin to provide meteorological profiles and to compare the DIAL measurements with the in situ sensors distributed on the tower up to 396 m height. Assuming the DIAL column measurement extending from 153 m altitude to 1353 m altitude should agree with the tower in situ sensor at 396 m altitude, there was a 7.9 ppm rms difference between the DIAL and the in situ sensor using a 30 min? rolling average on the DIAL measurement.     

A weak magnetic field measurement system using micro-fluxgate sensors and delta-sigma interface

This paper presents a weak magnetic field measurement system using micro-fluxgate (FG) sensors and a sensor signal processing technique using the delta-sigma modulation in the negative feedback loop. The feedback of the lowpass filtered bitstream output of a delta-sigma modulator to the magnetic field improves system linearity, hysteresis, and stability. In spite of the fact that the second-order delta-sigma modulator is used, the third-order noise shaping can be obtained in the digital output bit-stream by the use of an integrator in the loop. This improves the SNR of the digital output. The measured noise of the implemented system meets the measured noise of the FG sensing element itself. The weak magnetic field in the range of the Earth's magnetic field is successfully measured. The nonlinearity error is less than 0.4% in the range of /spl plusmn/100 /spl mu/T.     

A review of wireless SAW sensors

Wireless measurement systems with passive surface acoustic wave (SAW) sensors offer new and exciting perspectives for remote monitoring and control of moving parts, even in harsh environments. This review paper gives a comprehensive survey of the present state of the measurement systems and should help a designer to find the parameters required to achieve a specified accuracy or uncertainty of measurement. Delay lines and resonators have been used, and two principles have been employed: SAW one-port devices that are directly affected by the measurand and SAW two-port devices that are electrically loaded by a conventional sensor and, therefore, indirectly affected by the measurand. For radio frequency (RF) interrogation, time domain sampling (TDS) and frequency domain sampling (FDS) have been investigated theoretically and experimentally; the methods of measurement are described. For an evaluation of the effects caused by the radio interrogation, we discuss the errors caused by noise, interference, bandwidth, manufacturing, and hardware tuning. The system parameters, distance range, and measurement uncertainty are given numerically for actual applications. Combinations of SAW sensors and special signal processing techniques to enhance accuracy, dynamic range, read out distance, and measurement repetition rate (measurement bandwidth) are presented. In conclusion, an overview of SAW sensor applications is given.     

阵列光电传感器的非线性校正

阵列光电传感器在接近饱和时表现出非线性,但是可以通过阵列传感器的线性区的系数外推得到修正,而且只需在一个波长位置测得曝光量与A/D转换值的响应曲线,将能够推广到任意波长位置。为此,利用最小二乘法进行多项式拟合和软件的非线性校正,在同等硬件配置的条件下,增加了线阵传感器的线性区,延拓了传感器的动态范围。在整个动态范围内,系统测量误差可以减少到±2%。此非线性校正方法也非常适用于光电阵列传感器的光谱仪生产厂的强度定标校正。