Absolute robot calibration with a single telescoping ballbar

A novel 6D measurement system was recently proposed, comprising a single commercially available telescoping ballbar and two custom-made fixtures. One fixture is attached to the robot base and the other to the robot end-effector, and each having three magnetic cups. In each of 72 poses of the tool fixture, with respect to the base fixture, it is possible to measure six distances with the ballbar between the magnetic cups on the tool fixture and the magnetic cups on the base fixture, and thus calculate the pose with high accuracy. This paper is the first to present the successful use of this measurement system for absolute robot calibration. The robot calibrated is a Fanuc LR Mate 200iC six-axis industrial robot and the telescoping bar used is the QC20-W by Renishaw. The absolute position accuracy of the robot after calibration is validated with a Faro laser tracker in almost 10,000 robot configurations. Considering the validation data in only the front/up configurations, the mean absolute positioning error is improved from 0.873 mm to 0.479 mm. To allow a comparison, the robot is also calibrated using the laser tracker and the robot accuracy validated in the same 10,000 robot configurations.     

Correction to: Proposed Model for Radio Wave Attenuation due to Rain (RWAR)

Wireless Personal Communications - A correction to this paper has been published: https://doi.org/10.1007/s11277-021-08370-x     

Vasoconstrictors inhibit ATP-sensitive K+ channels in arterial smooth muscle through protein kinase C

We investigated therapeutic effects of a rapid- and short-acting non-sulfonylurea hypoglycemic agent, calcium (2S)-2-benzyl-3-(cis-hexahydro-2-isoindolinylcarbonyl)propionate dihydrate (KAD-1229), on streptozotocin (STZ)-induced non-insulin-dependent diabetes mellitus (NIDDM) rats. The effects exerted by KAD-1229 on the post-prandial plasma glucose rise in STZ-induced mild NIDDM (mNIDDM) rats were different from those of sulfonylureas. When KAD-1229 with liquid meal (10 kcal/kg) was given to the mNIDDM rats, the plasma glucose migration was similar to that of normal healthy rats. On the contrary, glibenclamide had little or no effect on the plasma glucose rise 0.5-1 hr after oral administration, and its effect was only evident 2-5 hr after dosing. Tolbutamide showed similar hypoglycemia to that induced by glibenclamide at 2-5 hr with insufficient efficacy at 0.5 hr. Gliclazide sufficiently suppressed the level of post-prandial plasma glucose. However, its complete inhibition of post-prandial plasma glucose was associated with the extra-hypoglycemia 1-5 hr after oral administration. We also tested the efficacy of KAD-1229 in more severe STZ-induced NIDDM (sNIDDM) rats to elucidate the effects of the drug on the long-term glycemic controls and diabetic complications. When the sNIDDM rats were treated with 10 mg/kg KAD-1229 twice a day for about 17 weeks, increases in fasting plasma glucose and hemoglobin A1c were inhibited. Furthermore, treatment with KAD-1229 suppressed the development of microalbuminuria and cortical cataract. We conclude that the rapid- and short-acting insulinotropic agent KAD-1229 is able to improve the deterioration in the glycemic controls and inhibit the development of diabetic complications in STZ-induced NIDDM rats.     

Effects of Atmospheric Impairments of Satellite Link Operating in Ka Band

Wireless Personal Communications - Over the past decades, satellites have been used to provide a variety of services like voice, data, negation and video. Frequencies above 10 GHz provide...     

Absolute calibration of an ABB IRB 1600 robot using a laser tracker

The absolute accuracy of an ABB IRB 1600 industrial robot is improved using a 29-parameter calibration model, developed after extensive experimentation. The error model takes into account all possible geometric errors (25 geometric error parameters to be identified through optimization, in addition to the pose parameters for the base and tool frames and four error parameters related to the compliance in joints 2, 3, 4 and 5). The least squares optimization technique is used to find the 29 error parameters that best fit the measures acquired with a laser tracker. Contrary to most other similar works, the validation of the robot's accuracy is performed with a very large number of measures (1,000) throughout the complete robot's joint space. After calibration, the mean/maximum position errors at any of eight different measurement points on the end-effector (all offset from axis 6 by approximately 120 mm) are reduced from 0.968 mm/2.158 mm respectively, to 0.364 mm/0.696 mm.     

Portable autonomous walk calibration for 4-legged robots

In the present paper we describe an efficient and portable optimization method for calibrating the walk parameters of a quadruped robot, and its contribution for the robot control and localization. The locomotion of a legged robot presents not only the problem of maximizing the speed, but also the problem of obtaining a precise speed response, and achieving an acceptable odometry information. In this study we use a simulated annealing algorithm for calibrating different parametric sets for different speed ranges, with the goal of avoiding discontinuities. The results are applied to the robot AIBO in the RoboCup domain. Moreover, we outline the relevance of calibration to the control, showing the improvement obtained in odometry and, as a consequence, in robot localization.     

Feature selection, mutual information, and the classification of high-dimensional patterns

We propose a novel feature selection filter for supervised learning, which relies on the efficient estimation of the mutual information between a high-dimensional set of features and the classes. We bypass the estimation of the probability density function with the aid of the entropic-graphs approximation of Rényi entropy, and the subsequent approximation of the Shannon entropy. Thus, the complexity does not depend on the number of dimensions but on the number of patterns/samples, and the curse of dimensionality is circumvented. We show that it is then possible to outperform algorithms which individually rank features, as well as a greedy algorithm based on the maximal relevance and minimal redundancy criterion. We successfully test our method both in the contexts of image classification and microarray data classification. For most of the tested data sets, we obtain better classification results than those reported in the literature.     

Information-theoretic selection of high-dimensional spectral features for structural recognition

Pattern recognition methods often deal with samples consisting of thousands of features. Therefore, the reduction of their dimensionality becomes crucial to make the data sets tractable. Feature selection techniques remove the irrelevant and noisy features and select a subset of features which describe better the samples and produce a better classification performance. In this paper, we propose a novel feature selection method for supervised classification within an information-theoretic framework. Mutual information is exploited for measuring the statistical relation between a subset of features and the class labels of the samples. Traditionally it has been measured for ranking single features; however, in most data sets the features are not independent and their combination provides much more information about the class than the sum of their individual prediction power. We analyze the use of different estimation methods which bypass the density estimation and estimate entropy and mutual information directly from the set of samples. These methods allow us to efficiently evaluate multivariate sets of thousands of features.Within this framework we experiment with spectral graph features extracted from 3D shapes. Most of the existing graph classification techniques rely on the graph attributes. We use unattributed graphs to show what is the contribution of each spectral feature to graph classification. Apart from succeeding to classify graphs from shapes relying only on their structure, we test to what extent the set of selected spectral features are robust to perturbations of the dataset.     

The Studies of Millimeter Waves at 60 GHz in Outdoor Environments for IMT Applications: A State of Art

As the growth of mobile technology network increasing exponentially due to which radio frequency becomes more valuable natural resources. Shortage of bandwidth creates an enormous opportunities for researchers and engineers for exploration of underutilize millimeter wave spectrum in order to design and develop future technologies. It is a need of an hour to do extensive studies on the impact of millimeter wave technologies as both indoor and outdoor environments. This paper describes the various studies carried out earlier in the field of radio wave propagation at 60 GHz in different outdoor environments.