In this paper, a theoretical and experimental study to evaluate the use of force control in drilling operations, based on an industrial robot, is presented. A force control strategy embedded in a commercial industrial robot, originally devoted to general machining tasks, is adapted to drilling operations. It is shown that satisfactory results can be achieved in standard industrial applications. Unwanted displacements can occur, resulting in dimensional uncertainty, especially in specimens with very small dimensions. Nevertheless, the implemented force control is able to avoid the risks of failure in the material, and to minimize the operating time in several industrial drilling processes.

The present paper deals with the subject of failure of deep-sea pipelines that have thickness metal-loss areas caused by corrosion and are subjected to high external hydrostatic pressure. An extensive research program was launched to observe failure modes, to examine existing and to develop prediction collapse equations, and to determine their accuracy. The program uses finite element modeling and external hydrostatic collapse tests of full-scale specimens. This paper presents and discusses the results of the first 20 collapse tests, which were performed in a new 103 MPa (15 ksi) hyperbaric chamber (760 mm internal diameter and 7200 mm length). The test results obtained with full scale specimens (324 mm external diameter and 23 mm thickness) made of low carbon steel API 5L X60 with external machined metal loss defects are used to verify the level of accuracy and conservatism of four analytical simple equations used to predict collapse of pipes with corrosion subjected to high external pressure.

This article aims to present a strategy for multi-objective optimization based on torque distribution for electrical 4WD (four-wheel drive) vehicles. By considering applications on uneven terrain, common to the navigation of tractors, off-road vehicles, or even mobile robots, an algorithm is developed having as input the vehicle attitude and output the controlled torque on each actuated wheel. The main criterion adopted is to guarantee the execution of a stable trajectory. And, to avoid wheel slippage, which occurs when low torques are applied, as well as vehicle rollover, which can occur in the presence of high torques, it is necessary to use two objective functions. To find the Pareto optimal solutions, the simplified dynamic model of a vehicle is adopted, considering a quasi-static motion. For each vehicle, its electrical, mechanical, and geometric characteristics can be used as formulation constraints. From an optimization performed offline, and adopting a polynomial approximation-based approach for real-time application, simulations and experiments show an interesting behavior: solutions that go beyond allowing the ascent of simple ramps or the overcoming of smooth obstacles are found - it is possible, for example, to climb ramps with high slopes, taking the vehicle to the limit between stability and instability.

This work presents a methodology to perform a combined torque and time optimization for trajectories with particular force requirements. Usually, to reduce the time interval of a trajectory, elevated torques are required, an issue mainly when the mechanism needs to spend part of its energy to apply forces on its environment. In order to find a solution for this problem, an optimization method can be adopted. Here, the procedure is divided in two phases. First, a manipulator posture is chosen to minimize the total applied torques on the robot joints, performed by using a recently developed technique. Afterwards, from the selected posture, a set of possible joint velocities is simulated. The goal of this process is to find a threshold for the time trajectory from which the torque on the robot joints is not largely intensified. The dynamics based on a Lagrangian formulation of a two-link serial arm is applied for the mechanical modeling. By carrying out the analysis, it is possible to relate the robot posture, the velocity and the forces applied on the robot endeffector with the torque on the robot joints, to find an optimal trajectory.

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