Robot Vision System for Coordinate Measurement of Feature Points on Large Scale Automobile Part

In this paper,we present a robot vision based system for coordinate measurement of feature points on large scale automobile parts.Our system consists of an industrial 6-DOF robot mounted with a CCD camera and a PC.The system controls the robot into the area of feature points.The images of measuring feature points are acquired by the camera mounted on the robot.3D positions of the feature points are obtained from a model based pose estimation that applies to the images.The measured positions of all feature points are then transformed to the reference coordinate of feature points whose positions are obtained from the coordinate measuring machine（CMM）.Finally,the point-to-point distances between the measured feature points and the reference feature points are calculated and reported.The results show that the root mean square error（RMSE） of measure values obtained by our system is less than 0.5 mm.Our system is adequate for automobile assembly and can perform faster than conventional methods.

Antenna Mechanical Pose Measurement Based on Structure from Motion

Antenna mechanical pose measurement has always been a crucial issue for radio frequency(RF)engineers,owning to the need for mechanical pose adjustment to satisfy the changing surroundings.Traditionally,the pose is estimated in the contact way with the help of many kinds of measuring equipment,but the measurement accuracy cannot be well assured in this way.We propose a non-contact measuring system based on Structure from Motion(SfM)in the field of photogrammetry.The accurate pose would be estimated by only taking several images of the antenna and after some easy interaction on the smartphone.Extensive experiments show that the error ranges of antenna’s downtilt and heading are within 2degrees and 5 degrees respectively,with the shooting distance in 25 m.The GPS error is also under 5 meters with this shooting distance.We develop the measuring applications both in PC and android smartphones and the results can be computed within 3 minutes on both platforms.The proposed system is quite safe,convenient and efficient for engineers to use in their daily work.To the best of our knowledge,this is the first pipeline that solves the antenna pose measuring problem by the photogrammetry method on the mobile platform.

Determiningrelativeposition and attitude of a close non-cooperative target based on the SIFT algorithm

A binocular stereo vision positioning method based on the scale-invariant feature trans- form （SIFT） algorithm is proposed. The SIFT algorithm is for extracting distinctive invariant features from images. First, image median filtering is used to eliminate image noise. Then, according to the characteristics of the target satellite, image map is used to extract the middle part of the target satel- lite. At last, the feature match point under the SIFT algorithm is extracted, and the three-dimension- al position and orientation are calculated. The features are invariant to image scale and rotation, and are shown to provide robust matching across a substantial range of affine distortion, change in 3D viewpoint, addition of noise, and change in illumination. The experimental result shows that the al- gorithm works well and the maximum relative error is within 0. 02 m and 2.5 o

MC-LRF based pose measurement system for shipborne aircraft automatic landing

Due to the portability and anti-interference ability,vision-based shipborne aircraft automatic landing systems have attracted the attention of researchers.In this paper,a Monocular Camera and Laser Range Finder(MC-LRF)-based pose measurement system is designed for shipborne aircraft automatic landing.First,the system represents the target ship using a set of sparse landmarks,and a two-stage model is adopted to detect landmarks on the target ship.The rough 6D pose is measured by solving a Perspective-n-Point problem.Then,once the rough pose is measured,a region-based pose refinement is used to continuously track the 6D pose in the subsequent image sequences.To address the low accuracy of monocular pose measurement in the depth direction,the designed system adopts a laser range finder to obtain an accurate range value.The measured rough pose is iteratively optimized using the accurate range measurement.Experimental results on synthetic and real images show that the system achieves robust and precise pose measurement of the target ship during automatic landing.The measurement means error is within 0.4in rotation,and 0.2%in translation,meeting the requirements for automatic fixed-wing aircraft landing.

High-precision pose measurement method in wind tunnels based on laser-aided vision technology

The measurement of position and attitude parameters for the isolated target from a highspeed aircraft is a great challenge in the field of wind tunnel simulation technology.In this paper,firstly, an image acquisition method for small high-speed targets with multi-dimensional movement in wind tunnel environment is proposed based on laser-aided vision technology.Combining with the trajectory simulation of the isolated model, the reasonably distributed laser stripes and selfluminous markers are utilized to capture clear images of the object.Then, after image processing,feature extraction, stereo correspondence and reconstruction, three-dimensional information of laser stripes and self-luminous markers are calculated.Besides, a pose solution method based on projected laser stripes and self-luminous markers is proposed.Finally, simulation experiments on measuring the position and attitude of high-speed rolling targets are conducted, as well as accuracy verification experiments.Experimental results indicate that the proposed method is feasible and efficient for measuring the pose parameters of rolling targets in wind tunnels.

Remote-controlled flexible pose measurement system and method for a moving target in wind tunnel

The measurement of position and attitude parameters for the isolated target from a highspeed aircraft is a great challenge in the field of wind tunnel simulation technology. This paper proposes a remote-controlled flexible pose measurement system in wind tunnel conditions for the separation of a target from an aircraft. The position and attitude parameters of a moving object are obtained by utilizing a single camera with a focal length and camera orientation that can be changed based on different measurement conditions. Using this proposed system and method, both the flexibility and efficiency of the pose measurement system can be enhanced in wind tunnel conditions to meet the measurement requirements of different objects and experiments, which is also useful for the development of an intelligent position and attitude measurement system. The position and the focal length of the camera also can be controlled remotely during measurements to enlarge both the vertical and horizontal measurement range of this system. Experiments are conducted in the laboratory to measure the position and attitude of moving objects with high flexibility and efficiency, and the measurement precision of the measurement system is also verified through experiments.

A Monocular Vision Measurement System of Three-Degree-of-Freedom Air-Bearing Test-Bed Based on FCCSP

A monocular vision-based pose measurement system is provided for real-time measurement of a three-degree-of-freedom （3-DOF） air-bearing test-bed. Firstly, a circular plane cooperative target is designed. An image of a target fixed on the test-bed is then acquired. Blob analysis-based image processing is used to detect the object circles on the target. A fast algorithm （FCCSP） based on pixel statistics is proposed to extract the centers of object circles. Finally, pose measurements can be obtained when combined with the centers and the coordinate transformation relation. Experiments show that the proposed method is fast, accurate, and robust enough to satisfy the requirement of the pose measurement.

Three-line structured light vision system for non-cooperative satellites in proximity operations

Adapter ring is a commonly used component in non-cooperative satellites,which has high strength and is suitable to be recognized and grasped by the space manipulator.During proximity operations,this circle feature may be occluded by the robot arm or limited field of view.Moreover,the captured images may be underexposed when there is not enough illumination.To address these problems,this paper presents a structured light vision system with three line lasers and a monocular camera.The lasers project lines onto the surface of the satellite,and six break points are formed along both sides of the adapter ring.A closed-form solution for real-time pose estimation is given using these break points.Then,a virtual structured light platform is constructed to simulate synthetic images of the target satellite.Compared with the predefined camera parameters and relative positions,the proposed method is demonstrated to be more effective,especially at a close distance.Besides,a physical space verification system is set up to prove the effectiveness and robustness of our method under different light conditions.Experimental results indicate that it is a practical and effective method for the pose measurement of on-orbit tasks.

An experimental system for release simulation of internal stores in a supersonic wind tunnel

Aerodynamic parameters obtained from separation experiments of internal stores in a wind tunnel are significant in aircraft designs. Accurate wind tunnel tests can help to improve the release stability of the stores and in-flight safety of the aircrafts in supersonic environments.A simulative system for free drop experiments of internal stores based on a practical project is provided in this paper. The system contains a store release mechanism, a control system and an attitude measurement system. The release mechanism adopts a six-bar linkage driven by a cylinder, which ensures the release stability. The structure and initial aerodynamic parameters of the stores are also designed and adjusted. A high speed vision measurement system for high speed rolling targets is utilized to measure the pose parameters of the internal store models and an optimizing method for the coordinates of markers is presented based on a priori model. The experimental results show excellent repeatability of the system, and indicate that the position measurement precision is less than0.13 mm, and the attitude measurement precision for pitch and yaw angles is less than 0.126°, satisfying the requirements of practical wind tunnel tests. A separation experiment for the internal stores is also conducted in the FL-3 wind tunnel of China Aerodynamics Research Institute.