Showing papers by "Paolo Rocco published in 1999"

Modular dynamic virtual-reality modeling of robotic systems

Abstract: This article presents the results of research into the field of dynamic simulation of mechanical and robotic systems. The main goal of the whole project is to achieve an efficient modular approach to modeling, in order to make the modeling process easier, ensure its traceability and inspectability, and support model reuse. This is achieved through the declarative definition of models, the standardization of model interfaces, and the object-oriented approach to model development and model data management. The article presents the specific features ofa general-purpose simulation environment, including an overview of the 3D solid modeling software interfaces. The modeling and simulation of a 3-DOF gripper designed for Space robotics applications is also discussed to show the performance of the whole simulation environment in terms of complexity management, efficiency, and accuracy.

Force oscillations in contact motion of industrial robots: an experimental investigation

Abstract: Describes the results of research on the oscillatory behavior that has been systematically experienced in the force measured during contact motion of an industrial robot. Two phenomena have been found to be mainly responsible for it, namely, the arm structural elasticity due to the torsional flexibility of the joints and the torque ripple of the brushless motors. The structural elasticity is characterized by a resonance frequency which varies with the arm configuration, while the torque ripple has harmonics of frequency proportional to the motor velocity. Most severe oscillations, and even loss of the contact, arise when the resonance and ripple frequency values come closer or match, so that elasticity and ripple excite each other.

Torque ripple adaptive rejection in brushless motors

Abstract: A known problem with brushless permanent magnet AC motors is that parasitic pulsations generally affect the torque. A compact model of the pulsating torque has been recently proposed by the authors (1998), together with simple laboratory identification experiments. In this paper the identification methodology is first extended to cope with variable speed motion. Then, recognizing the time varying nature of the torque disturbance, an adaptive identification, based on a recursive least squares algorithm, is proposed, which naturally leads to an adaptive compensation of the disturbance. Experimental results confirm the validity of the method.

Modular dynamic modeling and simulation of grasping

Abstract: A point contact model, suitable for dynamic modeling and simulation of complete grasping tasks, is discussed in the paper. The model is applicable to an arbitrary number of contacts and is local to the point of contact, thus allowing a modular approach to grasp systems modeling. The model, based on an extension of the LUGRE friction model, also accounts for microscale phenomena such as microsliding displacements. Some simulation results are discussed showing the effectiveness of the model in assessing the performance of a grasp control system.