On-Line Computational Scheme for Mechanical Manipulators

Abstract

Industrial robots are mechanical manipulators whose dynamic characteristics are highly nonlinear. To control a manipulator which carries a variable or unknown load and moves along a planned path, it is required to compute the forces and torques needed to drive all its joints accurately and frequently at an adequate sampling frequency (no less than 60 Hz for the arm considered). This paper presents a new approach of computation based on the method of Newton-Euler formulation which is independent of the type of manipulator-configuration. This method involves the successive transformation of velocities and accelerations from the base of the manipulator out to the gripper, link by link, using the relationships of moving coordinate systems. Forces are then transformed back from the gripper to the base to obtain the joint torques. Theoretically the mathematical model is "exact. "A program has been written in floating point assembly language which has an average execution time of 4.5 milliseconds on a.PDP 11/45 computer for a Stanford manipulator. This allows an on-line computation within control systems with a sampling frequency no lower than 60 Hz. A further advantage of using this method is that the amount of computation increases linearly with the number of links whereas the conventional method based on Lagrangian formulation increases as the quartic of the number of links.

Preliminary investigation of the lateral postural stability of spinal cord-injured individuals subjected to dynamic perturbations

“…The links represented the lower torso, the upper torso and arms together, and the neck and head together. The parameters for the links were calculated from body segment measurements through the use of an anthropomorphic software package 21 (Generator of Body Data, Wright-Patterson Air Force Base, OH, USA).…”

Implementação Em Hardware De Um Controlador Neural Para Robô

“…Na tentativa de superar estas dificuldades, vários algoritmos de controle usando as características dinâmicas do robô manipulador têm sido propostos [1], [4], [5], [6], [9].…”

“…Cada elemento de M(q) e G(q) é uma função que depende da posição de cada junta do robô. Já o termo H(q, q 0) que especifica reações coriolis e forças centrífugas é uma função tanto da posição (q) quanto da velocidade (q 0) [2], [3] e [5].…”

Network model approach to the analysis of multirigid-body systems

“…The special cases where the joints are spherical, revolute and prismatic (sliding pair) are considered after the establishment of the general system model. Although the closed form equations are useful for theoretical investigations, an algorithmic approach to the solution of these equations is preferable [10][11][12][13][14]. This is the main reason for keeping the across variables xc.…”

“…From the first six rows of equation (1) (10) and the circuit equation (8) and the relations in equation (10) …”