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This paper presents a general methodology to calibrate the geometric and flexibility parameters of robots with flexible joints and links. The method uses the classical description of rigid robots, description of the shape of links...
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This paper presents a general methodology to calibrate the geometric and flexibility parameters of robots with flexible joints and links. The method uses the classical description of rigid robots, description of the shape of links, and definition of the elasticity parameters. The generalized Jacobian matrix corresponding to the geometric and flexibility parameters is obtained, using the flexible transformation matrices between successive links. The reaction forces and moments on the links and joints are obtained using a customized recursive Newton Euler algorithm, similar to that used in the computation of the inverse dynamic model. The calibration of the PA-If robot of Mitsubishi is presented by simulation and practical experimentation. We show that taking into account the joint flexibility for this robot allows us to improve its accuracy.
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The development of hydrological models that produce practically useful and physically defensible results is an ongoing challenge in hydrology. This challenge is further compounded in large, spatially variable basins with sparse da...
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The development of hydrological models that produce practically useful and physically defensible results is an ongoing challenge in hydrology. This challenge is further compounded in large, spatially variable basins with sparse data, where a detailed understanding of a basin's hydrological response may be limited. This study presents an iterative and stepwise calibration strategy for model structure and parameters for a hydrological model of the 275,000 km(2)Liard River basin in northern Canada. The calibration procedure was optimized to exploit and represent available data at 29 stream gauges and included the use of multiple data sources to constrain model calibration and improve model function. A flexible modelling framework was used to allow the explicit inclusion of locally varied model structure within the calibration procedure. The final model exhibits strong performance in both calibration and validation, and represents significantly different hydrological responses in different portions of the basin well. The calibration procedure helped to identify differences in hydrological processes within the basin which have not been considered by other models of the Liard. The ability to modify model structure in order to account for different hydrological regimes in different parts of the basin is demonstrated to improve model performance locally and globally.
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In this paper differential kinematics was geometrically derived to be utilized in a calibration algorithm that improves the accuracy of the manipulation of a robot. Even though the mechanical components are manufactured and assemb...
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In this paper differential kinematics was geometrically derived to be utilized in a calibration algorithm that improves the accuracy of the manipulation of a robot. Even though the mechanical components are manufactured and assembled precisely, small differences between the designed and the actual system always exist, due to both geometric and unmodelled errors. In order to resolve these problems, differential relationships between the model parameters and the end-effector's posture were formulated. Subsequently, a derivative based estimation algorithm, such as an EKF (Extended Kalman Filter) manner, could be adopted to update the model parameters. The proposed algorithm includes joint flexibility, so is an advanced version of previous work, where a rigid joint model was adopted [1]. The effectiveness of the proposed algorithm was verified by a computer simulation with a 6 DOF manipulator robot.
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Together with the trends of mass personalization, flexible robotic applications become more and more popular. Although conventional robotic automation of workpiece manipulation seems to be solved, advanced tasks still need great a...
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Together with the trends of mass personalization, flexible robotic applications become more and more popular. Although conventional robotic automation of workpiece manipulation seems to be solved, advanced tasks still need great amount of effort to be reached. In most cases, on-site robot programming methods, which are intuitive and easy to use, are not applicable in flexible scenarios. On the other hand, the application of offline programming methods requires careful modeling and planning. Consequently, this paper proposes a generalized development methodology for flexible robotic pick-and-place workcells, in order to provide guidance and thus facilitate the development process. The methodology is based on the Digital Twin (DT) concept, which allows the iterative refinement of the workcell both in the digital and in the physical space. The goal is to speed up the overall commissioning (or reconfiguration) process and reduce the amount of work in the physical workcell. This can be achieved by digitizing and automating the development, and maintaining sufficient twin closeness. With that, the operation of the digital model can be accurately realized in the physical workcell. The methodology is presented through a semi-structured pick-and-place task, realized in an experimental robotic workcell together with a reconfiguration scenario.
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Flexible tactile sensing based on capacitive sensing has become a research hotspot inrecent years because of its low energy consumption, high performance and wide application prospects. However, the axis error caused by the coupli...
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Flexible tactile sensing based on capacitive sensing has become a research hotspot inrecent years because of its low energy consumption, high performance and wide application prospects. However, the axis error caused by the coupling deformation of thedielectric will seriously affect the accuracy of the sensor. In this paper, a capacitive flexiblethree‐axis tactile sensor array is modelled and simulated, and a neural network‐basedcalibrator for the three‐axis sensor array is proposed, which can be used to calibratethe simulated measurement data. The simulation results show that even though thecorrelation coefficient of linear regression for each axis is very close to 1, the effect ofdielectric nonlinear coupling distortion cannot be eliminated. The calibration methodbased on the neural network can effectively suppress the nonlinear coupling distortion ofthe dielectric, and reduce the measurement coupling rate of the sensor model from 26%to 1%. At the same time, in order to ensure the measurement accuracy and robustness ofdifferent units in the sensor array, the input layer of the calibrator is expanded, and thedata set containing capacitance information and two‐dimensional location information isused for training. The experimental results show that the proposed calibration methodcombining two‐dimensional position information training accurately calibrates thecapacitive flexible three‐dimensional tactile sensor array.
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A method to calculate the local damping coefficient and the bond Young's modulus of a flexible fibre for use in the discrete element method (DEM) was proposed and validated. Segments of harvested wheat straw were clamped on one en...
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A method to calculate the local damping coefficient and the bond Young's modulus of a flexible fibre for use in the discrete element method (DEM) was proposed and validated. Segments of harvested wheat straw were clamped on one end while the other end was deflected a set distance, released, and allowed to vibrate freely. This cantilever beam motion was captured by a high-speed camera (960 fps). The red-band of the images were isolated and used to calculate the x-section height (mm) along the stem in time. This data was then fit to a non-linear function, which conforms to beam theory. The global bond damping coefficient, as a function of x-section height, was then calculated and found to be in the range of -0.5 to -0.2. The cantilever beam experiment was then repeated in the DEM software LIGGGHTS, where the wheat straw was modelled as a single line of spheres connected by stiff-flexible bonds. A design of experiment (DOE) was ran varying bond Young's modulus and local bond damping, to determine the linear relationships with the global bond damping coefficient and the frequency of oscillation of the DEM particle respectively. With the proposed method the DEM local bond damping coefficient and the DEM bond Young's modulus were calibrated with relative errors of 0.9% and 1.8% respectively to laboratory estimated values. Utilising the linear relationships found from the DEM simulations, the bond Young's modulus was found to be in the range of 0.42-4.84 GPa. (C) 2019 IAgrE. Published by Elsevier Ltd. All rights reserved.
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Purpose This paper aims to propose a novel model and calibration method to improve the absolute positioning accuracy of a robotic drilling system with secondary encoders and additional axis. Design/methodology/approach The enhance...
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Purpose This paper aims to propose a novel model and calibration method to improve the absolute positioning accuracy of a robotic drilling system with secondary encoders and additional axis. Design/methodology/approach The enhanced rigid-flexible coupling model is developed by considering both kinematic parameters and link flexibility. The kinematic errors of the robot and the additional axis are considered with a model containing 27 parameters. The elastic deformation errors of the robot under self-weight of links and end-effector are estimated with a flexible link model. For calibration, an effective comprehensive calibration method is developed by further considering the coordinate systems parameters of the drilling system and using a two-step process constrained Levenberg-Marquardt identification method. Findings Experiments are performed on the robotic drilling system that contains a KUKA KR500 R2830 industrial robot and an additional lifting axis with a laser tracker. The results show that the maximum error and mean error are reduced to 0.311 and 0.136 mm, respectively, which verify the effectiveness of the model and the calibration method. Originality/value A novel enhanced rigid-flexible coupling model and a practical comprehensive calibration method are proposed and verified. The experiments results indicate that the absolute positioning accuracy of the system in a large workspace is greatly improved, which is conducive to the application of industrial robots in the field of aerospace assembly.
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Laser beam used as a visualizing measuring axis has emerged as a major candidate technology for 3D shape measurement. Until now, a prime limitation has been the highly-accurate positioning of laser beam in the whole measurement sp...
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Laser beam used as a visualizing measuring axis has emerged as a major candidate technology for 3D shape measurement. Until now, a prime limitation has been the highly-accurate positioning of laser beam in the whole measurement space. A multi-position calibration method for laser beam based on the cyclical error of harmonic turntable is proposed in this paper. A flexible calibration field constructed by CMM and PSD-based laser receiving board is presented. The coordinate of laser spot on PSD is obtained and transformed into CMM coordinate system. The direction vector of laser beam is obtained by linear fitting from a set of calibrated laser spots. Then the laser beams are calibrated in multiple positions. Based on the cyclicity of harmonic turntable, the error model of rotation angle is established by Fourier series function. The rotation angles are compensated in whole-space and the positioning of laser beam is obtained with highly-accurate. The experimental results demonstrate that the RMSE of linear fitting of laser beams is no more than 0.006 mm, the RMSE of the compensated rotation angles is no more than 0.003 degrees, the RMSE of the spatial points is 0.089 mm and the RMSE of the reconstructed distances is 0.060 mm.
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The design specifications and experimental characteristics of a newly developed laser-projection transnasal flexible endoscope coupled with a high-speed videoendoscopy system are provided. The hardware and software design of the p...
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The design specifications and experimental characteristics of a newly developed laser-projection transnasal flexible endoscope coupled with a high-speed videoendoscopy system are provided. The hardware and software design of the proposed system benefits from the combination of structured green light projection and laser triangulation techniques, which provide the capability of calibrated absolute measurements of the laryngeal structures along the horizontal and vertical planes during phonation. Visual inspection of in vivo acquired images demonstrated sharp contrast between laser points and background, confirming successful design of the system. Objective analyses were carried out for assessing the irradiance of the system and the penetration of the green laser light into the red and blue channels in the recorded images. The analysis showed that the system has irradiance of 372 W/m(2) at a working distance of 20 mm, which is well within the safety limits, indicating minimal risk of usage of the device on human subjects. Additionally, the color penetration analysis showed that, with probability of 90%, the ratio of contamination of the red channel from the green laser light is less than 0.002. This indicates minimal effect of the laser projection on the measurements performed on the red data channel, making the system applicable for calibrated 3D spatial-temporal segmentation and data-driven subject-specific modeling, which is important for further advancing voice science and clinical voice assessment.
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This study developed a novel error compensation method aimed at eliminating placement error caused by hand-eye calibration and pick-and-place tool motions in automatic stiffener bonder for flexible printed circuit. Using the trans...
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This study developed a novel error compensation method aimed at eliminating placement error caused by hand-eye calibration and pick-and-place tool motions in automatic stiffener bonder for flexible printed circuit. Using the transformation of homogeneous coordinates to develop an error model of the system describing the coupling of errors among various coordinate systems, the least squares method is used to calculate the unknown model parameters. The experiment results demonstrate that this error compensation method reduced placement error by an order of magnitude. The mounting precision throughout the entire work area was 60.046mm at 3sigma, and for flexible printed circuit products with a specification limit of 0.1 mm, the process capability index of the automatic stiffener bonder in this study was 2.19. This represents that the system is capable of fully satisfying the precision requirements of flexible printed circuit stiffener bonding. The proposed system employing a vibrating feeder bowl and machine vision-aided target positioning is applicable to a variety of stiffeners, which enhances production flexibility. The proposed error model considers the complex coupling effect of the errors among multiple coordinate systems in hand-eye calibration, without the need of detecting and calculating the calibration error item by item, and takes into account the errors produced by the rotation and downward pressing motions of the pick-and-place tool.
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