Simplified theodolite calibration for robot metrology

Theodolites represent a well-established three-dimensional-point-measuring technology. However, when used for robot applications they have to be properly calibrated to fulfil the necessary accuracy requirements. The theodolite calibration methods reported in the literature involve the use of costly sophisticated equipment not easily available to most users. Therefore, a new simplified calibration technique is presented based on the use of a graduated precision bar suspended freely to align with the vertical direction. To develop efficient mathematical models, the theodolites will be regarded as 2R open-ended mechanisms with the end-effector axis directed along the line of sight. The proposed models are then coded in a computer program designed to verify the validity of the technique presented. The simulation results will be presented at the end of the paper.     

37—THE AIR-FLOW FINENESS OF GREASY WOOL: INTER-LABORATORY TESTS OF A PROPOSED STANDARD PROCEDURE

An account is given of an inter-laboratory trial of a method of measuring the fineness of greasy wool by means of a Wira Air-flow Fineness Meter. Eight laboratories took part in two tasks: firstly, a calibration by each laboratory of its own air-flow meter in terms of internationally standardized wools; and, secondly, the measurement of the fineness of greasy-wool core samples by means of the specified method, which included a normal laboratory washing of the wool followed by opening on a wool-type Shirley Analyser.

As a result of the trial, the method was considered to be suitable for use by testing authorities, and tentative limits of precision of the method of measuring the fineness of greasy wool were established. The mean difference between any two laboratories ranged from 0.2 μm at 20-μm diameter to 0.5 μm at 28-μm diameter. This does not include sampling errors.     

A general approach for sensibility analysis in visual servoing

In an experimental robotic context, it is very important to study the robustness of visual servoing control laws with respect to uncertainties that arise on the camera intrinsic and extrinsic parameters. Here we propose a general approach allowing us to analyze the sensibility of such control laws with respect to the camera parameter uncertainties. We only focus on sensibility aspects and do not address the stability analysis problem. The presented approach is validated on several examples which consider uncertainties on focal length, camera optical centers and measurement noise.     

Error Analysis and Effective Adjustment of the Walking-Ready Posture for a Biped Humanoid Robot

A walking control algorithm is generally a mixture of various controllers; it depends on the characteristics of the target system. Simply adopting one part of another researcher's algorithm does not guarantee an improvement in walking performance. However, this paper proposes an effective algorithm that can be easily adopted to other biped humanoid robots; the algorithm enhances the walking performance and stability of the robot merely by adjusting the walking-ready posture. The walking performance of biped humanoid robots is easily affected by an unsuitable walking-ready posture in terms of accuracy and repeatability. More specifically, low accuracy for the walking-ready posture may cause a large difference between an actual biped robot and its mathematical model, and the low repeatability may disturb the evaluation of the performances of balance controllers. Therefore, this paper first discusses the factors that detrimentally affect bipedal walking performance and their phenomena in the walking-ready posture. The necessary conditions for an ideal walking-ready posture are then defined based on static equilibrium and a suitable adjustment algorithm is proposed. Finally, the effectiveness of the algorithm is verified through dynamic computer simulations.     

Localization and guidance with an embarked camera on a mobile robot

In this paper, a new method using the Hough transform to correct the drift of the mobile robot CESA is presented. The corrections are made by direct observation. As an illustration, an algorithm implemented is detailed, and experiment results for CESA navigation in our laboratory's corridor and trajectory generation are given.     

The Calibration of Air-flow Apparatus for the Determination of the Fibre Diameter of Wool

There is a general algorithm for the determination of practicable starting allocations of colours to the two sides of a 4 × 4 box pick-at-will loom, but its convenience in use varies greatly. An improvement is indicated, but a simpler and more efficient algorithm is suggested for the one-empty-box case, for which the general algorithm is least satisfactory.

Two of the constraints of weft patterning on such 4 × 4 box looms are examined, largely by using the general algorithm. First, the maximum number of practicable starting allocations is determined for any given number of weft colours and any smaller number of box-pairs. Next, it is shown that there is a possibility that a weft repeat may be unweavable with one shuttle per colour if the number of picks in the reduced repeat is not less than the number of shuttle boxes in use.

In contrast to the genera! case, if there is only one empty shuttle box, the box plan that minimizes the number of large box movements for a given weft repeat can rapidly be determined by using a microcomputer.