Estimation And Compensation of Angular Misalignment At Robot End Brush Roller - Workpiece Contact Interface Via Elastic Contact Force Perception

When the non-standard customized brush roller tool is used for robotic grinding of large-scale components, the clamping and positioning error of the brush roller at the end of the robot is extremely easy to cause misalignment at the brush roller - workpiece contact interface, which will affect the machining accuracy and surface quality. In order to ensure the parallel contact between the brush roller and the workpiece surface during the machining process, a calculation model of the angular misalignment at the brush roller - workpiece contact interface is proposed based on the elastic contact force perception, and then the accurate positioning of the robot end brush roller is realized by a fast compensation method. Firstly, according to the geometric force relationship between the brush roller and the workpiece, as well as the determined brush roller material properties parameters, the estimation model of angular misalignment is established. Secondly, both the axial force and normal torque at the time of initial contact detected by the force-controlled sensor are regarded as the input parameters in the model. Further, the calculated brush roller - workpiece contact offset is used as the geometric error compensation amount, and the brush roller is deflected to achieve error compensation by the robot RAPID program control command. The finite element simulation results are compared with the theoretical calculation values, and the average relative error is 15.1%. The experiment on robotic grinding and brushing of high-speed rail body indicates that the compensated angle can be reduced to 0.024° from an average of 0.179° before compensation, coupled with uniform material removal depth. The proposed method can significantly improve the contour accuracy of large-scale components.

Static and dynamic characteristics of a Rayleigh-steps mechanical seal with reverse steps

This paper presents a Rayleigh-steps mechanical seal with reverse steps (RS-MS), and the governing equation was solved by the finite difference method (FDM). The effects of angular misalignment, working condition parameters, and film thickness on sealing performance were discussed, including the opening force, cavitation ratio, leakage rate, frictional torque, stiffness and damping coefficients. The results indicate that the cavitation phenomenon in the reverse step groove can restrain the leakage, while it also affects the stability of the seal. The angular misalignment makes the seal have greater stiffness and damping coefficients. The stiffness and damping coefficients decrease rapidly with the increase of the film thickness, and the dynamic stability of the mechanical seal decreases with the increase of the film thickness, which is not conducive to the stable operation of the seal. The research results can guide the optimization design of mechanical seals.

Analisis Ketidaksesumbuan Poros (Misalignment) pada Rotordinamik Berdasarkan Sinyal Suara

This research aims to identify misalignment of the rotor dynamics based on sound spectrum characteristic. In this study, rotor dynamics consist of motor, shaft, coupling and bearings. Three types of misalignment were considered, namely parallel, angular, and combination misalignment. In order to obtain the best signal, microphones were used as sensors to capture sound signal placed on coupling and each bearing. The signal obtained was in time series. The sound signal in the time domain is then filtered to remove noise signals, which are then transferred to be signals in the frequency domain using Fast Fourier Transform (FFT). From the test results, it is found that in the case of parallel misalignment, the sound frequency spectrum is obtained with a peak amplitude at 2x rpm. The case of angular misalignment obtained a sound spectrum with a peak amplitude value and is dominant at 1x rpm than 2x rpm. Meanwhile, in the case of a combination of parallel and angular misalignment, a peak amplitude sound spectrum appears at 1x rpm and 2x rpm with relatively close spacing between the peaks of the sound spectrum. The result shows that sound signal can be used for identification of misalignment of the rotor dynamics.

Post-mission misalignment angle calibration for airborne laser scanners

An Airborne Laser Scanning (ALS) system operates by locating returned laser pulses independently from all others. Locating the returned laser pulses requires knowing precisely for each laser pulse, the aircraft position (e.g. GPS), the attitude of the aircraft (e.g. IMU), the scanner angle when the laser pulse left the sensor, and the slant range to the terrain surface for that pulse. One of the most critical errors in ALS systems is the angular misalignment between the scanner and the IMU, which is called the misalignment or boresight error. This error must be addressed before an ALS system can accurately produce data. The purpose of this thesis was to develop and test a method of estimating the small misalignment angles between the laser scanner and the combined GPS/IMU solution for position and attitude. This method is semi-automated, requires no ground control and does not re-sample the ALS data in order to match the overlapping strips of data. A computer program called Misalignment Estimator was developed to estimate the misalignment angles using a least squares adjustment. The method was tested using a data set located at the Oshawa airport and provided by Optech. The misalignment angles were estimated to be -0.0178 degrees, -0.0829 degrees and 0.0320 degrees, for roll, pitch and heading respectively. The estimation of the misalignment angles was considered to be successful. Further research into automated point matching is recommended.

Post-mission misalignment angle calibration for airborne laser scanners

An Airborne Laser Scanning (ALS) system operates by locating returned laser pulses independently from all others. Locating the returned laser pulses requires knowing precisely for each laser pulse, the aircraft position (e.g. GPS), the attitude of the aircraft (e.g. IMU), the scanner angle when the laser pulse left the sensor, and the slant range to the terrain surface for that pulse. One of the most critical errors in ALS systems is the angular misalignment between the scanner and the IMU, which is called the misalignment or boresight error. This error must be addressed before an ALS system can accurately produce data. The purpose of this thesis was to develop and test a method of estimating the small misalignment angles between the laser scanner and the combined GPS/IMU solution for position and attitude. This method is semi-automated, requires no ground control and does not re-sample the ALS data in order to match the overlapping strips of data. A computer program called Misalignment Estimator was developed to estimate the misalignment angles using a least squares adjustment. The method was tested using a data set located at the Oshawa airport and provided by Optech. The misalignment angles were estimated to be -0.0178 degrees, -0.0829 degrees and 0.0320 degrees, for roll, pitch and heading respectively. The estimation of the misalignment angles was considered to be successful. Further research into automated point matching is recommended.

Intercept Factor for a Beam-Down Parabolic Trough Collector

This paper presents a method for evaluating the intercept factor (γ) of a beam-down parabolic trough collector (BDPTC), accounting for collector design, solar cone, and shading on the aperture due to secondary reflectors. A numerical ray-tracing technique was developed and used for the purpose. Validation was performed by comparing the results with rays traced in a two-dimensional drafting program. The effects of changing the rim-angle and angular misalignment associated with the primary and secondary concentrators for various designs are presented and discussed in detail. The optimum values of the design parameters for low, medium, and high concentration ratio BDPTCs are reported. An online tool for quickly estimating γ is also launched in this paper.

Stiffness characteristics of crossed roller bearings with roller roundness deformation

This study investigated the stiffness characteristics of crossed-roller bearings (XRBs) subjected to various loading and boundary conditions. A five degree-of-freedom XRB model was adopted that considers the effect of roller roundness deformation, which was developed by the authors in a prior study. The analytical formulation for a fully occupied (5 × 5) stiffness matrix of XRB was obtained. Extended simulations were performed to determine the XRB stiffness and internal load distribution considering the effects of the external loads, axial preloads, axial clearance, and angular misalignment. The numerical results confirmed that the bearing stiffness possessed significant nonlinearity with respect to the external loads. Increasing the axial clearance reduced the stiffness of the bearing under radial and moment loading, but it did not affect the stiffness of the pure axially loaded bearing. The stiffness of the bearing with axial clearance increased consistently with the misalignment angle. The stiffness behavior of the preloaded bearing depended on the misalignment angle.