This is the first (Paper I) of three companion papers focused respectively, on the estimates of the errors in ice thickness retrieved from pulsed ground-penetrating radar (GPR) data, on how to estimate the errors at the grid points of an ice-thickness DEM, and on how the latter errors, plus the boundary delineation errors, affect the ice-volume estimates. We here present a comprehensive analysis of the various errors involved in the computation of ice thickness from pulsed GPR data, assuming they have been properly migrated. We split the ice-thickness error into independent components that can be estimated separately. We consider, among others, the effects of the errors in radio-wave velocity and timing. A novel aspect is the estimate of the error in thickness due to the uncertainty in horizontal positioning of the GPR measurements, based on the local thickness gradient. Another novel contribution is the estimate of the horizontal positioning error of the GPR measurements due to the velocity of the GPR system while profiling, and the periods of GPS refreshing and GPR triggering. Their effects are particularly important for airborne profiling. We illustrate our methodology through a case study of Werenskioldbreen, Svalbard.

Dimensional errors of the parts from a part family cause the initial misplacement of theworkpiece on the fixture affecting the final product quality. Even if the part ispositioned correctly, the external machining forces and clamping load cause the part todeviate from its position. This deviation depends on the external load and the fixturestiffness. In this article, a comprehensive analytical model of a 3-2-1 fixturing systemis proposed, consisting of a kinematic and a mechanical part. The kinematic modelrelocates the initially misplaced workpiece in the machine reference through the axialadvancements of six locators taking all the fixturing elements to be rigid. Therepositioned part then shifts again from the corrected position due to the deformation offixturing elements under clamping and machining forces. The mechanical model calculatesthis displacement of the part considering the locators and clamps to be elastic. The rigidcuboid baseplate, used to precisely relocate the workpiece, is also considered elastic atthe interface with the locators. Using small displacement hypothesis with zero friction atthe contact points, Lagrangian formulation enables us to calculate the rigid bodydisplacement of the workpiece, deformation of each locator, as well as the stiffnessmatrix and mechanical behavior of the fixturing system. This displacement of the workpieceis then finally compensated by the advancement of the six axial locators calculatedthrough the kinematic model.

High accuracy is usually difficult to obtain with a robotic arm installed on a mobile base, since the errors of the base are transferred to the manipulator. This paper proposes a method to address this problem through integration of a self-calibration algorithm and low-cost sensors. The self-calibration algorithm might be repeated several times during execution of a mission by the robot and is only based on the internal sensors of the robot, meaning that external observers or reference point transceivers (e.g., ultrasonic transceivers) are not used. The proposed self-calibration system was implemented on a pole climbing robot and effectively improved the positioning accuracy of the climbing arm.

In this paper a pneumatic vibratory wrist operated with a PWM controller is developed for robotic assembly. In the vibratory assembly system, the vibratory wrist can perform random search motion of a hole to compensate the position error at the early stage of an insertion process. Since the vibration characteristics of the wrist, such as the amplitude and trajectory of the vibration, are critical to assembly performance, they are experimentally investigated for various system controller parameters. In addition, a series of insertion experiments are performed to evaluate the assembly performance of the proposed wrist. The results show that within a wide range of operating conditions the wrist vibration can effectively compensate for large positioning errors when this wrist is used for a chamferless peg-in-hole task.

In this paper we develop a compilant system that permits robotic assembly of chamferless pieces. The idea is to absorb the positioning error between parts to be inserted by giving one of them a planar random movement. An actuator consisting of two axes (X and y) operated by an electromagnetic System is fitted to the work table; when its inputs are pseudo-random binary signais (P.R.B.S.) random motion is obtained. The trajectories of the actuator are analysed depending upon the P.R.B.S. parameters and a peg-in-a-hole assembly task is carried out. Experimental results show that large positioning errors can be compensated for chamferless insertions.