Papers by Keyword: Position Measurement

Abstract: This paper presents a method for initial calibration and online compensation of systematic errors in a resolver system. Initial calibration at standstill condition is carried out for a few positions by applying Discrete Fourier Transform and Least Squares method. The error model is constructed based on complex Fourier expression of position angle signal obtained from non-ideal resolver signals due to amplitude imbalance, quadrature error and offset. Error parameters are determined online using the integral control loops which are initialized with the calibration results. Besides, single channel amplitude tracking is incorporated in the error compensation scheme. This makes the compensation adaptive to changes in error parameters. And thus accuracy of the resolver system is reasonably improved and the system becomes robust. The effectiveness of the proposed method is validated by simulation and experiments.

Abstract: In the traditional spraying production line, the wheels are mounted on the catenary hook. The location of the wheel valve hole is by artificial visual. Not only the workers labor. This paper puts forward the technology of line scanning the wheel valve hole position based on the linear CCD. The method is unfolding the wheel circumference image into the two-dimensional plane image. Then we use the image processing and matching technology to measure the wheel valve hole position.

Abstract: The paper aims to measure the exact position while detecting inner surface defects of large scale pipeline. A realizable method using opto-electrical is presented in this paper, which can give the position of opto-electrical sensor. On-line measured data is automatically recorded and processed with precision because of the application of step motor and gear drive, as well as software controlling computer.

Abstract: The stereo-camera method is used to measure the positions of robots. In taking the measurements it is important to precisely measure the distance between cameras and the relative posture of the cameras. Therefore, we developed a novel method for measuring a mobile robot's relative position and posture by photographing robots’ pivot turns. A mobile robot system was equipped with a camera and an identification marker that made it possible to measure position and posture with the stereo-camera method when the viewpoint changed freely. One robot photographs the pivot turns of another. As the latter turns, an identification marker on it is used to trace the movement onto an image. The turning robot’s position and posture is determined by the length and angle of the trace. This procedure makes it possible for each of the two robots to obtain their relative position and posture, making the measurement of the stereo-camera method precise. Measuring with a fixed stereo camera is impossible when there are obstacles in the environment and the object being measured moves over a wide range. However, this robot system was able to use the stereo-camera method to expand the measurement range.

Abstract: A three-axis mosaic surface encoder, which can measure the X-directional position and the Y-, Z-directional straightness of the linear stage in a long range, is proposed. The three-axis mosaic surface encoder is composed of multiple scanning probes and a mosaic scale grating. The mosaic scale grating is constructed by placing the multiple two-dimensional reflective-type scale gratings in a line to obtain long measurement range along the in-plane direction of a scale grating. In addition, the optical configuration of the encoder head, which employs multiple scanning probes to be projected on the mosaic scale grating, is proposed so that a long range measurement can be achieved by the mosaic scale gratings. With the proposed encoder head, the measurement information of the X-directional displacement can always be obtained from the probe which is not on the gaps of the mosaic scale grating. The proposed configuration was applied to the three-axis surface encoder, and basic performances of the proposed three-axis mosaic surface encoder are experimentally investigated.

Abstract: In order to solve the problem of algorithmic complexity and large computation in Doppler radar measurement processing, a direct unscented Kalman filter is proposed in the paper. It undertakes nonlinear filtering to Doppler radar measurement in mixed coordinate directly, which makes the algorithm much simpler and reduces computation greatly. Simulation results show that the algorithm not only reaches the similar state estimation accuracy like SEKF and SUKF, but also improves the consistency of state estimation apparently.

Abstract: In this paper, a software-based resolver-to-digital converter using tangent algorithm is proposed. Meanwhile, three main non-ideal signal characteristics which cause the error of the presented resolver-to-digital converter are individually discussed, and the error compensation methods are given. The results show that the proposed strategies effectively improve the accuracy and stability of the system.

Abstract: The speed and position measurement is an important part of the train control system. Accurate measurement of train speed and position ensures safety of train running and improves transportation efficiency. Traditional methods to measure speed and position usually rely on single sensor, which has less accuracy and reliability. A method of measuring train speed and position based on multi-sensor fusion is proposed in this paper. Since trains are running on fixed rail tracks, the position of train can be determined by the traveled distance and speed monitoring is essentially to measure the magnitude of train velocity. According to this characteristic, this measurement system consists of axle odometer, Doppler radar, accelerometer and intermittent inquiry balise. The federated Kalman filter is used to implement multi-sensor fusion. Simulation experiment results prove that this method can improve the accuracy and reliability of train speed and position measurement.

Abstract: Position and pose measurement is an important issue in the field of robot navigation, operation and assembly as well as other fields such as photogrammetry, computer vision, computer graphics and other disciplines. The micro-table as a machine tool, one of the key components for improving the processing quality of the product plays a particularly role. However, in certain circumstances, we could not continuously and steady proceed relying on the naked eye when precisely and rapidly measure the small size, color matching and identification and so on, and the existing detection methods are difficult to balance the contradiction between the speed and accuracy. This paper puts forward a measurement method of detection 6-dof micro-table position and pose based on binocular vision. Using two CCD cameras measure 2D micro-table coordinates of the four corners of points from different angles, by coordinates transformation, we can calculate the 3D coordinates of the four corners of points; then we can solve the micro-table position and pose with the four corners of points.

Abstract: This abstract presents the development of an ultra-precision motion controlled positioning stage for nanometer positioning over a working volume of 50 mm × 50 mm × 4 µm at an accuracy of better than 10 nm that is traceable to the national standards. The positioning stage is designed to use various probing systems to perform “pick and place” manipulations and scanning of large specimens, including biological. The system is comprised of a two-axis, long-range stage and a 6 degree-of-freedom (DOF) short-range stage. The long-range stage is responsible for coarse motions of up to 50 mm, while the short-range stage is responsible for correcting positioning errors generated by the long-range stage to achieve nanometer level accuracies. The system will be housed in a vacuum chamber operating at a vacuum pressure of better than 10-3 Torr. The vacuum chamber is also designed to act as an environmental chamber where different gases can be used depending on the measurement task. The initial results of the fully developed positioning stage will be presented at the conference.