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The paper provides a detailed treatment of the expected range performance for the laser rangefinder (LRF) developed for the Polish ImAging SaTellites (PIAST) space mission, where the distance between satellites within a constellation has to be measured during orbital flight. The satellites are equipped with corner cube retroreflectors (CCR) to increase the efficiency of laser back-reflection. A theoretical signal-to-noise range-dependence model was developed to determine the maximum expected range of the measurements. This model included the tilt-angle-dependent properties of the CCR far-field diffraction patterns (FFDP) which were measured experimentally. In addition, the specific parameters of the receiving optoelectronic circuit used were considered. The obtained results show that in the case of the constructed PIAST LRF (peak laser pulse power of 100 W, laser beam divergence of 5 mrad, receiving optical aperture diameter of 2 in, CCR diameter of 2 in), depending on the CCR angular inclination, a maximum measurement distance of 15-40 km is expected. [ABSTRACT FROM AUTHOR]

The forest understory is often associated with rapid rates of carbon and nutrient cycling, but cost-efficient quantification of its biomass remains challenging. We tested a new field technique for understory biomass assessment using an off-the-shelf handheld laser rangefinder. We conducted laser sampling in a pine forest with an understory dominated by invasive woody shrubs, especially Rhamnus frangula L. Laser sampling was conducted using a rangefinder, mounted on a monopod to provide a consistent reference height, and pointed vertically downward. Subsequently, the understory biomass was measured with destructive sampling. A series of metrics derived from the airborne LiDAR literature were evaluated alone and in combination for prediction of understory biomass using best-subsets regression. Resulting fits were good ( r2 = 0.85 and 0.84 for the best single metric and best additive metric, respectively, and R2 = 0.93 for the best multivariate model). The results indicate that laser sampling could substantially reduce the need for costly destructive sampling within a double-sampling context. [ABSTRACT FROM AUTHOR]

We proposed an all-fiber tunable distributed Bragg reflector (DBR) laser rangefinder, which realized high-accuracy measurement of the absolute distance in the range of 1.88 to 3.33 m based on the self-mixing effect. The theoretical analysis of the all-fiber tunable DBR laser shows that wavelength tuning range and frequency of the laser can influence the measurement range and resolution. In addition, the experimental results indicate that the influence factors of measurement accuracy and sensitivity in absolute distance measurement are modulation response linearity, experimental equipment, and circuit bandwidth, which is in good agreement with theory analysis. Moreover, increasing the linear wavelength tuning range of the tunable DBR laser is an essential method to improve the measurement accuracy and sensitivity of the absolute distance measurement system. [ABSTRACT FROM AUTHOR]

Ball on plate platform is a great tool for testing of various control techniques. This study provides a detailed design and comparison of three control structures for automatic stabilization of the ball's location on plate and ball trajectory tracking. Namely PD controller, state space feedback and state space observer with state space feedback. All three methods are designed and practically compared. All structures have a common feature. It is the methodology for calculating the parameters of the controllers. Ball - on - plate mathematical model derived by Newton's method and DC motor position loop control are also part of this article. For the authors of this article, this study is an opportunity to create an educative setup to explain the principles of basic control system for non - technical person and offers motivation to future students. [ABSTRACT FROM AUTHOR]

In this study, we successfully developed a high signal-to-noise ratio (SNR) rangefinder based on a piezoelectric micromachined ultrasonic transducer (pMUT). A c -axis-oriented Pb(Mn 1/3 ,Nb 2/3 )O 3 -Pb(Zr,Ti)O 3 (PMnN-PZT) epitaxial thin film was employed as a piezoelectric transducer considering its outstanding figures-of-merit for SNR, due to the high piezoelectric coefficient and small relative permittivity (typical values: e 31, f = −14C/m 2 , ε r = 200–300). The pMUTs was based on an epitaxial PMnN-PZT/Si diaphragm structure and prototyped from a SOI substrate; its rangefinding ability was evaluated with a pair of devices, specifically, transmitter and receiver, respectively. As a result, the maximum range was estimated to be over 2 m at a low actuating voltage of 1 V p-p , when 12 dB was set as the threshold SNR. The energy consumption of the transmitter was as small as ∼5 nJ for the generation of a 50-cycle ultrasonic burst. The noise analysis of the receiver’s charge amplifier circuit indicated that this system could be improved by the optimization of bandwidth and by eliminating external noise. We believe that this high performance pMUT rangefinder will be utilized in various applications of consumer electronics or as an alternative to the bulk piezoelectric ceramic rangefinder in the near future. [ABSTRACT FROM AUTHOR]

We propose a method for developing small all-fiber vehicle laser rangefinders that is based on pulse position modulation (PPM) and data integration and present a theoretical study on its performance. Compared with spatial coupling, which is employed by most of the current commercial vehicle laser rangefinders, fiber coupling has the advantage that it can guide laser echoes into the interior of a car, so the electronic components following the photodiode can operate in a moderate-temperature environment. However, optical fibers have numerical apertures (NAs), which means that a laser beam from a receiving lens cannot be coupled into an optical fiber if its incident angle exceeds the critical value. Therefore, the effective size of the receiving lens is typically small since it is limited by its focal length and the NA of the fiber, causing the power of the laser echoes gathered by the receiving lens to be insufficient for performing target identification. Instead of increasing the peak transmitting laser power unrestrictedly, PPM and data integration effectively compensate for the low signal-to-noise ratio that results from the effective receiving lens size reduction. We validated the proposed method by conducting numerical simulations and performance analysis. Finally, we compared the proposed method with pseudorandom noise (PN) code modulation and found that, although the two methods perform equally well in single-target measurement scenarios, PPM is more effective than PN code modulation for multitarget measurement. In addition, PPM enables the transmission of laser beams with higher peak powers and requires less computation than PN code modulation does. [ABSTRACT FROM AUTHOR]

RGB-D sensors became a standard in robotic applications requiring object recognition, such as object grasping and manipulation. A typical object recognition system relies on matching of features extracted from RGB-D images retrieved from the robot sensors with the features of the object models. In this paper we present ModReg: a system for registration of 3D models of objects. The system consists of a modular software associated with a multi-camera setup supplemented with an additional pattern projector, used for the registration of high-resolution RGB-D images. The objects are placed on a fiducial board with two dot patterns enabling extraction of masks of the placed objects and estimation of their initial poses. The acquired dense point clouds constituting subsequent object views undergo pairwise registration and at the end are optimized with a graph-based technique derived from SLAM. The combination of all those elements resulted in a system able to generate consistent 3D models of objects. [ABSTRACT FROM AUTHOR]

This paper describes a navigation and seamless localization system that permits carlike robots to move safely in heterogeneous scenarios within indoor and outdoor environments. The robot localization integrates different sensor (GPS, odometry, laser rangefinders) information depending on the kind of area (indoors, outdoors, and areas between) or on the sensor uncertainty in such a way that there are no discontinuities in the localization, and a bounded uncertainty is constantly maintained. Transitions through indoor and outdoor environments are thoroughly considered to assure a smooth change in-between. The paper addresses a navigation technique that combines two well-known obstacle avoidance techniques, namely the nearness diagram and the dynamic window approaches, exploiting the advantages and properties of both, and integrating the seamless localization technique. The navigation technique is developed for carlike robots by considering their shape and kinodynamic constraints, and the restrictions imposed by the environment. Forward-backward maneuvers are also integrated in the method, allowing difficult situations in dense scenarios to be managed. The whole system has been tested in simulations and experiments in real large-scale scenarios. [ABSTRACT FROM AUTHOR]

We studied the effect of frequency dispersion in an antenna-waveguide tract on the properties of the difference frequency signal when measuring distances in free space. The dispersion leads to an increase in the measurement error and reduced noise immunity. It has been shown that the simultaneous impact of frequency dispersion and parasitic amplitude modulation further increases the error. We propose and investigate variants of the Fourier transform that reduce said error, and give quantitative estimates of the achieved performance results. [ABSTRACT FROM AUTHOR]

Indoor navigation is important for various applications such as disaster management, building modeling, safety analysis etc. In the last decade, indoor environment has been a focus of wide research that includes development of indoor data acquisition techniques, 3D data modeling and indoor navigation. In this research, an automated method for 3D modeling of indoor navigation network has been presented. 3D indoor navigation modeling requires a valid 3D model that can be represented as a cell complex: a model without any gap or intersection such that two cells (e.g. room, corridor) perfectly touch each other. This research investigates an automated method for 3D modeling of indoor navigation network using a geometrical model of indoor building environment. In order to reduce time and cost of surveying process, Trimble LaserAce 1000 laser rangefinder was used to acquire indoor building data which led to the acquisition of an inaccurate geometry of building. The connection between surveying benchmarks was established using Delaunay triangulation. Dijkstra algorithm was used to find shortest path in between building floors. The modeling results were evaluated against an accurate geometry of indoor building environment which was acquired using highly-accurate Trimble M3 total station. This research intends to investigate and propose a novel method of topological navigation network modeling with a less accurate geometrical model to overcome the need of required an accurate geometrical model. To control the uncertainty of the calibration and of the reconstruction of the building from the measurements, interval analysis and homotopy continuation will be investigated in the near future. [ABSTRACT FROM AUTHOR]

Markov localization and its variants are widely used for mobile robot localization. These methods assume Markov independence of observations, implying that the observations can be entirely explained by a map. However, in real human environments, robots frequently make unexpected observations due to unmapped static objects like chairs and tables, and dynamic objects like humans. We therefore introduce Episodic non-Markov Localization (EnML), which reasons about the world as consisting of three classes of objects: long-term features corresponding to permanent mapped objects, short-term features corresponding to unmapped static objects, and dynamic features corresponding to unmapped moving objects. Long-term features are represented by a static map, while short-term features are detected and tracked in real-time. To reason about unexpected observations and their correlations across poses, we augment the Dynamic Bayesian Network for Markov localization to include varying edges and nodes, resulting in a novel Varying Graphical Network representation. The maximum likelihood estimate of the belief is incrementally computed by non-linear functional optimization. By detecting timesteps along the robot’s trajectory where unmapped observations prior to such time steps are unrelated to those afterwards, EnML limits the history of observations and pose estimates to “episodes” over which the belief is computed. We demonstrate EnML using different types of sensors including laser rangefinders and depth cameras, and over multiple datasets, comparing it with alternative approaches. We further include results of a team of indoor autonomous service mobile robots traversing hundreds of kilometers using EnML. [ABSTRACT FROM AUTHOR]

The problem of real-time relative orbit estimation of long range and high speed between a noncooperative target and a chaser is addressed. A high precision relative orbit model, in which the Earth J2 perturbation has been taken into consideration, is established for state estimation. As the attitude of the chaser is required for relative orbit estimation, it has also been estimated. The range, elevation, and azimuth between the target and the chaser, which can be measured by a laser rangefinder and a CCD device, are chosen as measuring vector, while a rate gyroscope and one star sensor is installed on the chaser to measure its rate and attitude parameters. On the basis of nonlinear filtering technology, two kinds of filtering systems are designed, namely the separated filtering system and the united filtering system, and the relationship between the two filtering systems are analyzed. Simulation results indicate the united filtering system is more robust than the separated filtering system against realistic initial attitude errors and attitude measurement noises. [ABSTRACT FROM AUTHOR]

This paper presents a novel reactive collision avoidance method for mobile robots moving in dense and cluttered environments. The proposed method, entitled Tangential Gap flow (TGF), simplifies the navigation problem using a divide and conquer strategy inspired by the well-known Nearness-Diagram Navigation (ND) techniques. At each control cycle, the TGF extracts free openings surrounding the robot and identifies the suitable heading which makes the best progress towards the goal. This heading is then adjusted to avoid the risk of collision with nearby obstacles based on two concepts namely, tangential and gap flow navigation. The tangential navigation steers the robot parallel to the boundary of the closest obstacle while still emphasizing the progress towards the goal. The gap flow navigation safely and smoothly drives the robot towards the free area in between obstacles that lead to the target. The resultant trajectory is faster, shorter and less-oscillatory when compared to the ND methods. Furthermore, identifying the avoidance maneuver is extended to consider all nearby obstacle points and generate an avoidance rule applicable for all obstacle configurations. Consequently, a smoother yet much more stable behavior is achieved. The stability of the motion controller, that guides the robot towards the desired goal, is proved in the Lyapunov sense. Experimental results including a performance evaluation in very dense and complex environments demonstrate the power of the proposed approach. Additionally, a discussion and comparison with existing Nearness-Diagram Navigation variants is presented. [ABSTRACT FROM AUTHOR]

In this article, an accurate method for the registration of point clouds returned by a 3D rangefinder is presented. The method modifies the well-known iterative closest point (ICP) algorithm by introducing the concept of deletion mask. This term is defined starting from virtual scans of the reconstructed surfaces and using inconsistencies between measurements. In this way, spatial regions of implicit ambiguities, due to edge effects or systematical errors of the rangefinder, are automatically found. Several experiments are performed to compare the proposed method with three ICP variants. Results prove the capability of deletion masks to aid the point cloud registration, lowering the errors of the other ICP variants, regardless the presence of artifacts caused by small changes of the sensor view-point and changes of the environment. [ABSTRACT FROM AUTHOR]

A 2-D laser rangefinder (LRF) and a camera are widely applied in various mobilized systems, such as autonomous robot and unmanned ground vehicle. Integration of these two types of sensors promotes a new measurement technology. Extrinsic calibration is crucial and basically the first step to fuse image and laser data. The chessboard-plane-based method is one of the most popular ones, which requires at least five plane-input (five shots). Vasconcelos et al. recently reduced the number of shots from five to three and derived the minimal solution. However, it requires solving a sophisticated perspective-three-point (P3P) problem with eight solutions. This paper first introduces a virtual trihedron from three plane-input and reformulates the P3P problem directly in 3-D space rather than in 3-D dual space to derive the minimal solution for extrinsic calibration. Based on this, we propose a novel and flexible method for extrinsic calibration of an LRF–camera with a trirectangular trihedron (or a cube). One unique feature is that the method requires only a single shot of the target, which can greatly simplify the calibration procedure. The proposed calibration method involves solving simplified P3P and perspective-three-line (P3L) problems separately. In particular, computation of LRF pose is formulated as a simplified P3P problem, which is easily solved and has unique solution from single-shot laser data only. It also avoids the degeneration problem. Camera pose computation is formulated as a simplified P3L problem from image data. The proposed calibration method has been tested with both simulation and real data. The results show that the method is both accurate and flexible for extrinsic calibration of a 2-D LRF and a camera. [ABSTRACT FROM AUTHOR]

Automatic detection of people is essential for automated systems that interact with persons and perform complex tasks in an environment with humans. To detect people efficiently, in this article it is proposed the use of high-level information from several people detectors, which are combined using probabilistic techniques. The detectors rely on information from one or more sensors, such as cameras and laser rangefinders. The detectors' combination allows the prediction of the position of the persons inside the sensors' fields of view and, in some situations, outside them. Also, the fusion of the detector's output can make people detection more robust to failures and occlusions, yielding in more accurate and complete information than the one given by a single detector. The methodology presented in this paper is based on a recursive Bayes filter, whose prediction and update models are specified in function of the detectors used. Experiments were executed with a mobile robot that collects real data in a dynamic environment, which, in our methodology, is represented by a local semantic grid that combines three different people detectors. Results indicate the improvements brought by the approach in relation to a single detector alone. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) data processing has applications in solving complex tasks such as object recognition, environment modeling, and robotic mapping and localization. Because using raw 3D data without preprocessing is very time-consuming, extraction of geometric features that describe the environment concisely is essential. In this sense, a plane can be a suitable geometric feature due to its simplicity of extraction and the abundance in indoor environments. This paper presents an online incremental plane extraction method using line segments for indoor environments. Our data collection system is based on a “nodding” laser scanner, so we exploit the incremental nature of its data acquisition in which physical rotation and 3D data processing are conducted in parallel. Line segments defined by two end points become supporting elements that comprise a plane, so a large proportion of scan points can be ignored once the line segments are extracted from each scan slice. This elimination of points reduces the algorithm complexity and computation time. Experiments with the tens of complete scan data sets which were acquired from a typical indoor environment demonstrated that our method was at least three times faster than the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Target positioning systems based on MEMS gyros and laser rangefinders (LRs) have extensive prospects due to their advantages of low cost, small size and easy realization. The target positioning accuracy is mainly determined by the LR's attitude derived by the gyros. However, the attitude error is large due to the inherent noises from isolated MEMS gyros. In this paper, both accelerometer/magnetometer and LR attitude aiding systems are introduced to aid MEMS gyros. A no-reset Federated Kalman Filter (FKF) is employed, which consists of two local Kalman Filters (KF) and a Master Filter (MF). The local KFs are designed by using the Direction Cosine Matrix (DCM)-based dynamic equations and the measurements from the two aiding systems. The KFs can estimate the attitude simultaneously to limit the attitude errors resulting from the gyros. Then, the MF fuses the redundant attitude estimates to yield globally optimal estimates. Simulation and experimental results demonstrate that the FKF-based system can improve the target positioning accuracy effectively and allow for good fault-tolerant capability. [ABSTRACT FROM AUTHOR]

Human–robot collaboration is a key issue for the development of factories of the future, a space where humans and robots can work and carry out tasks together. Within this collaborative human–robot interaction paradigm, safety is one of most critical subjects. The presented paper describes a security framework for industrial robotic cells based on laser rangefinders able to detect and track obstacles around the robot, information that is used to modify robot’s behaviour and guarantee safety. The system includes a Joint Probability Data Association Particle Filter to enhance the tracking process. The obtained results, implemented and tested in a real industrial robotic cell, show the suitability of the approach. [ABSTRACT FROM AUTHOR]

The Kalman filter is a valued method of signals filtration having the possibility of a sensors fusion, which is commonly applied in aerospace technology. Mainly, it eliminates random noises, improves the accuracy of a measurement system and their resistance to unexpected faults. Small unmanned aerial vehicles (UAV) are a challengeable area for various applications of the Kalman filter, because their high dynamics makes them highly sensitive to external disturbances acting on the on-board sensors. The paper discusses an application idea of the Kalman filter, whose purpose is to reduce the quantity of accidental incorrect measurements reported by a miniature laser rangefinder fixed to the UAV's wing. To verify the filtration effectiveness, real distance measurements recorded during real flights were applied. The results compare two approaches: an optimization using a reference signal from the second sensor mounted to the same UAV, and an adaptation of the covariance matrix R based on innovation. We can observe that the measurements of the laser rangefinder are corrected significantly, especially for the adaptation method, what is visible as the reduced amount of the incorrect distance measurements. Hence, the reliable detection and localization of an obstacle can be achieved by the usage of the miniature laser rangefinder. [ABSTRACT FROM AUTHOR]

In the field of precision assembly of large & medium scale, the orientation and position measurement system is quite demanding. In this paper a novel measuring system, consisting of four motorized stages, a laser rangefinder, an autocollimator and a camera is proposed to assist precision assembly. Through the design of coaxial optical system, the autocollimator is integrated with a laser rangefinder into a collimation rangefinder, which is used for measuring orientation and position synchronously. The laser spot is adopted to guide autocollimation over a large space and assist the camera in finding collimated measurand. The mathematical models and practical calibration methods for measurement are elaborated. The preliminary experimental results agree with the methods currently being used for orientation and position measurement. The measuring method provides an alternative choice for the metrology in precision assembly. [ABSTRACT FROM AUTHOR]

Many applications, like mobile robotics, can profit from acquiring dense, wide-ranging and accurate 3D laser data. Off-the-shelf 2D scanners are commonly customized with an extra rotation as a low-cost, lightweight and low-power-demanding solution. Moreover, aligning the extra rotation axis with the optical center allows the 3D device to maintain the same minimum range as the 2D scanner and avoids offsets in computing Cartesian coordinates. The paper proposes a practical procedure to estimate construction misalignments based on a single scan taken from an arbitrary position in an unprepared environment that contains planar surfaces of unknown dimensions. Inherited measurement limitations from low-cost 2D devices prevent the estimation of very small translation misalignments, so the calibration problem reduces to obtaining boresight parameters. The distinctive approach with respect to previous plane-based intrinsic calibration techniques is the iterative maximization of both the flatness and the area of visible planes. Calibration results are presented for a case study. The method is currently being applied as the final stage in the production of a commercial 3D rangefinder. [ABSTRACT FROM AUTHOR]

Surmounting terrain elevations, such as terraces, is useful to increase the reach of mobile robots operating in disaster areas, construction sites, and natural environments. This paper proposes an autonomous climbing maneuver for tracked mobile manipulators with the help of the onboard arm. The solution includes a fast 3-D scan processing method to estimate a simple set of geometric features for the ascent: three lines that correspond to the low and high edges, and the maximum inclination axis. Furthermore, terraces are classified depending on whether they are reachable through a slope or an abrupt step. In the proposed maneuver, the arm is employed both for shifting the center of gravity of the robot and as an extra limb that can be pushed against the ground. Feedback during climbing can be obtained through an inertial measurement unit, joint absolute encoders, and pressure sensors. Experimental results are presented for terraces of both kinds on rough terrain with the hydraulic mobile manipulator Alacrane. [ABSTRACT FROM PUBLISHER]

Abstract: Laser may cause disfunction or even damage to laser rangefinder. Based on evaluation rules of high repetition rate laser jam pulsed laser rangefinder, the principles of distance deception and blinding jamming were analysed and the jamming success rate was calculated. We also set up a calculation example for 100kHz repetition rate laser jam certain type rangefinder. The result showed that we can obtain jamming grade and success rate, accomplish the quantitative evaluation of the laser jamming effect. [Copyright &y& Elsevier]

A reactive obstacle avoidance strategy based on local virtual target following is proposed in this paper with reference to obstacle avoidance problems for a unicycle mobile robot in an unknown environment. The strategy took a laser rangefinder as the main environment detecting sensor. A polar co-ordinate vector map (PMap) was utilized to store environmental information and a cluster ideology was used to describe obstacle features. The local virtual target comprised environment features and target information together and so it was used as a temporary target to guide the robot to track the real goal while accomplishing obstacle avoidance. This method could be applied to obstacles with arbitrary shapes and could reduce the environment memory amount dramatically. It improved the dynamic response performance of the robot and fulfilled real time obstacle avoidance when the robot was following a target. A great deal of robot experiments showed that the propounded strategy was very effective. [ABSTRACT FROM AUTHOR]

The possibility of reducing the influence of low-frequency noise in the laser phase-frequency rangefinders, which leads to a shortterm instability of converting links of the device has been reviewe. This is achieved through the use of filtering the output signal of the phase-frequency system, the frequency which is proportional to the measured distance. The electronic simulation of converting processes in such system was carried out for which the output signal models in analog and discrete form were received. The results of the simulation allow to choose optimal parameters for a high pass filter according to the allowable value of the error arising from the transition processes in it. By numerical simulations assessment of the random error of the device due to the influence of broadband noise has been carried out. The simulation results are presented as a function of the random error from the signal/noise ratio for the selected filter time constant. [ABSTRACT FROM AUTHOR]

Highlights: [•] We provided an error offset item to compensate the errors induced by lens distortion so that the accuracy of distance computation can be increased. [•] Applying the curve fitting technology to obtain the equation of the error offset item. [•] Low cost scheme on the sensor base structure improvements which enhance the mechanical strength for mobile robots application. [Copyright &y& Elsevier]

Abstract: In an effort to facilitate lighting-invariant exploration, this paper presents an appearance-based approach using 3D scanning laser-rangefinders for two core visual navigation techniques: visual odometry (VO) and visual teach and repeat (VT&R). The key to our method is to convert raw laser intensity data into greyscale camera-like images, in order to apply sparse, appearance-based techniques traditionally used with camera imagery. The novel concept of an image stack is introduced, which is an array of azimuth, elevation, range, and intensity images that are used to generate keypoint measurements and measurement uncertainties. Using this technique, we present the following four experiments. In the first experiment, we explore the stability of a representative keypoint detection/description algorithm on camera and laser intensity images collected over a 24 h period outside. In the second and third experiments, we validate our VO algorithm using real data collected outdoors with two different 3D scanning laser-rangefinders. Lastly, our fourth experiment presents promising preliminary VT&R localization results, where the teaching phase was done during the day and the repeating phase was done at night. These experiments show that it possible to overcome lighting sensitivity encountered with cameras, yet continue to exploit the heritage of the appearance-based visual odometry pipeline. [Copyright &y& Elsevier]

Curb detection is an important research topic in environment perception, which is an essential part of unmanned ground vehicle (UGV) operations. In this paper, a new curb detection method using a 2D laser range finder in a semi-structured environment is presented. In the proposed method, firstly, a local Digital Elevation Map (DEM) is built using 2D sequential laser rangefinder data and vehicle state data in a dynamic environment and a probabilistic moving object deletion approach is proposed to cope with the effect of moving objects. Secondly, the curb candidate points are extracted based on the moving direction of the vehicle in the local DEM. Finally, the straight and curved curbs are detected by the Hough transform and the multi-model RANSAC algorithm, respectively. The proposed method can detect the curbs robustly in both static and typical dynamic environments. The proposed method has been verified in real vehicle experiments. [ABSTRACT FROM AUTHOR]

The article discusses a study which adapted rangefinders used in hobby robotics without compromising performance. Instructions for the development of a low-cost ultrasonic rangefinder for estimating ice ablation that has an accuracy comparable with commercially available units are presented. The study design is focused on the PING ultrasound rangefinder manufactured by Parallax that retails for around 30 U.S. dollars. To record ice ablation during the 2008 melt season, two prototypes were deployed on Storglaciären, Sweden.

The development of new pulsed optical sources with high pulse stability allows the improvement of common contactless measurement techniques. A new two-way optical rangefinder, employing a femtosecond laser, is presented here from design to implementation. The system is based on the evaluation of the phase delay of the returning optical pulse train with respect to the outgoing one. The main idea is to expand the time interval corresponding to the phase delay by harmonic heterodyne downconversion of a high harmonic of the pulse repetition rate (up to 10 GHz), which is applied symmetrically to the two channels. The system has shown 10 \mu\m repeatability with a resolution that improves proportionally to the number of the employed harmonic. [ABSTRACT FROM AUTHOR]

Abstract: A pulsed time-of-flight (TOF) laser rangefinder with a pulsed laser diode and an avalanche photo diode (APD) receiver is constructed and tested. Trigged by an avalanche transistor, the laser diode can emit a periodic pulse with rise time of ∼2ns. A new structure with auto gain control (AGC) circuits both in the pre-amplifier and the post-amplifier is presented. Through this technology, not only the dynamic range of the receiver is extended, but also the walk error of timing discriminators is reduced. Large measurement range from 5m to 500m is achieved without any cooperative target. The single-shot precision is 3cm for the weakest signal. Compared with previous laser rangefinders, the complexity of this system is greatly simplified. [Copyright &y& Elsevier]

Abstract: This paper describes the principle and techniques of ultrasonic rangefinder based on micro-controller AT89C2051. The performance characteristics of the ultrasonic rangefinder are studied theoretically and experimentally. The primary objective of the study was to determine the hardware principle circuit and the main software design, the computed simulation by Pspice is provided for the key part of the hardware circuit. In this paper it is demonstrated that this type of the ultrasonic rangefinder is available. [Copyright &y& Elsevier]

Abstract: This paper deals with offline nonlinear state estimation where measurements are available only when some given equality conditions are satisfied. For this type of problems, which are often met in robot localization when sonar or radar are involved, the data are qualified as fleeting because the measurements are available only at some given unknown dates. In this paper, the first approach able to deal with nonlinear estimation with fleeting data is presented. An illustration related to offline robot localization with a laser rangefinder will be given. [Copyright &y& Elsevier]

The computational method of range estimate is presented to deal with the problem that the accuracy of position is too low to satisfy calculating the time-to-go because the pure INS has worked for long time without GPS. The messengers used by method include sight line angle from image seeker, relative position and altitude from INS. Under typical measuring errors, the influence of sampling frequency on estimation accuracy was analyzed. The engineering application scheme and time-to-go calculation strategy were given. The simulation results show that the accuracy of the range estimate is well enough to be used in engineering. [ABSTRACT FROM AUTHOR]

In this paper the problem of tracking walking people with multiple moving robots is tackled. For this purpose we present an adaptation to the Multiple Hypothesis Tracking method, which unlike classic MHT, allows for one-to-many associations between targets and measurements in each hypothesis production cycle and is thus capable of operating in a scenario involving multiple sensors. Derivation of hypotheses probabilities accounts for the continuously changing overlapping areas in fields of view of the robots sensors and for detection uncertainty. In the context of three experiments involving people walking among moving robots, the successful integration of our tracking algorithm to a real-world setup is assessed. [ABSTRACT FROM AUTHOR]

As laser scanning technology has improved a lot in recent years, terrestrial laser scanners (TLS) have become popular devices for surveying tasks with high accuracy demands, such as deformation analyses. For this reason, finding a stochastic model for TLS measurements is very important in order to get statistically reliable results. The measurement accuracy of laser scanners—especially of their rangefinders—is strongly dependent on the scanning conditions, such as the scan configuration, the object surface geometry and the object reflectivity. This study demonstrates a way to determine the intensity-dependent range precision of 3D points for terrestrial laser scanners that measure in 3D mode by using range residuals in laser beam direction of a best plane fit. This method does not require special targets or surfaces aligned perpendicular to the scanner, which allows a much quicker and easier determination of the stochastic properties of the rangefinder. Furthermore, the different intensity types—raw and scaled—intensities are investigated since some manufacturers only provide scaled intensities. It is demonstrated that the intensity function can be derived from raw intensity values as written in literature, and likewise—in a restricted measurement volume—from scaled intensity values if the raw intensities are not available. [ABSTRACT FROM AUTHOR]

This paper presents a study on the data measurements that the Hokuyo UST-20LX Laser Rangefinder produces, which compiles into an overall characterization of the LiDAR sensor relative to indoor environments. The range measurements, beam divergence, angular resolution, error effect due to some common painted and wooden surfaces, and the error due to target surface orientation are analyzed. It was shown that using a statistical average of sensor measurements provides a more accurate range measurement. It was also shown that the major source of errors for the Hokuyo UST-20LX sensor was caused by something that will be referred to as “mixed pixels”. Additional error sources are target surface material, and the range relative to the sensor. The purpose of this paper was twofold: (1) to describe a series of tests that can be performed to characterize various aspects of a LIDAR system from a user perspective, and (2) present a detailed characterization of the commonly-used Hokuyo UST-20LX LIDAR sensor. [ABSTRACT FROM AUTHOR]

Recently, a new type of displacement instrument using spectral-interference has been found, which utilizes fiber and a wideband light source to produce an interference spectrum. In this work, we develop a method that measures the absolute air-gap distance by taking wavelengths at two interference spectra minima. The experimental results agree with the theoretical calculations. It is also utilized to produce and control the spectral switch, which is much easier than other previous methods using other control mechanisms. A scanning mode of this scheme for stepped surface measurement is suggested, which is verified by a standard thickness gauge test. Our scheme is different to one available on the market that may use a curve-fitting method, and some comparisons are made between our scheme and that one. [ABSTRACT FROM AUTHOR]