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Manipulating mobile robots on a pre-defined path is a challenging task when there are unknown objects on its path. Most of the manipulators use gripping methods to move such obstacles. In this research, an object to be pushed in a predefined path is considered. Estimation of the point of contact is important to control the mobile robot in its desired path. This paper introduces a novel concept called Contact Position Estimator (CPE) to calculate the point of contact when the robot is moving on the said path. CPE estimates the position using the reaction torque observer and the estimated torque, which is a sensorless method of estimating the torque, was used. Results show the applicability of the proposed concept.

The Accelerator Production of Tritium (APT) Project is investigating using a superconducting linac for the high-energy portion of the accelerator. As this accelerator would be used to accelerate a high-current (100-mA) CW proton beam up to 1700 MeV, it is important to determine the effects of stray-beam impingement on the superconducting properties of 700-MHz Nb cavities. To accomplish this, two 3000-MHz elliptical niobium cavities were placed in a cryostat, cooled to nominally 2 K in sub-atmospheric liquid helium, and irradiated with 798-MeV protons at up to 490-nA average current. The elliptically shaped beam passed through the equatorial regions of both cavities in order to maximize sensitivity to any changes in the superconducting surface resistance. Over the course of the experiment, 6/spl times/10/sup 16/ protons were passed through the cavities. After irradiation, the cavities were warmed to 250 K, then recooled to investigate the effects of a room-temperature annealing cycle on the superconducting properties of the irradiated cavities. A detailed description of the experiment and the results shall be presented. These results are important to employing superconducting RF technology to future high-intensity proton accelerators for use in research and transmutation technologies.

The superconducting radiofrequency (SRF) part of the Accelerator Production of Tritium (APT) linac will accelerate a 100-mA proton beam from 217 MeV to 1700 MeV. Since SRF cavities can accept protons over a wide velocity range, cavities with only two different betas are required; however, three different length cryomodules are required. A modular design was adopted that will reduce the engineering and design effort to produce these cryomodules. A final design of the APT Engineering Development and Demonstration (ED&D) cryomodule for a two-cavity /spl beta/=0.64 cryomodule has been completed, and a single cryomodule will be fabricated by industry next year. The cavities will be cooled in a 2.15-K superfluid helium bath similar to the Continuous Electron Beam Accelerator (CEBAF) system. What sets the APT cryomodules apart is the high radiofrequency (RF) power that must be delivered to the cavities. The RF losses in the cavities and power couplers place a large heat load on the central helium liquifier. Minimizing these loads required extensive iterations of the power coupler cooling schemes and thermal shield. A spoke support arrangement was developed to keep the beam centerline fixed and to minimize forces acting on the helium vessel/cavity during cool down. Laminar flow through the cryomodule during clean room assembly dictated the use of a vacuum vessel with large top and bottom openings. Analyses were performed to ensure structural integrity under vacuum loading, while also minimizing vessel deflections which could impact beam centerline positioning. The structural/thermal analysis used to optimize the cryomodule design is presented in this paper.