A. Romiti

Force and moment measurement on a robotic assembly hand

Abstract In investigating active robot assembly, it is first necessary to solve the problem of measuring forces and moments on a gripper during insertion. In a previous study, we designed and built a robot wrist with six independent degrees of freedom and a parallel architecture which actuates gripper micromotion for error compensation purposes. The device presented here for measuring forces and moments should be readily applicable in industrial environments. Many different structural configurations have been examined, while levels of cross-correlation among the values measured by sensors vary according to the sensor arrangement, e.g., whether sensors are arranged along three orthogonal directions, on a plane and its perpendiculars, or in a Stewart platform configuration. The latter two cases are accurately analysed. Theoretical results are examined using six force sensors of a given measurement range (±50 N). Results in diagram form show hypervolumes of maximum normalized forces on each axis.

A Simulation Program for Analysis of Any Type of Fluid Mechanical Systems "Flowsim"

Abstract Transients in fluid mechanical systems with any nunber and type of components are analyzed. The systems may be hydraulic or pneumatic (adiabatic or diabatic), with propagation, heat flow and friction taken into account. A particular fonn of the energy equation for gases takes care of any thermodynamic transfonnations. A simulation program lets know the state of the system in any instant.

Four track mobile robot for non structured environments

Concerns a mobile robot to work in hostile environments, for civil protection or handling of nuclear material, having four tracks that may pivot around the driving axles. All tracks have a driving function, but they are moved only by two motors, one at each side, that allows to simplify the actuation and control system. For this reason, it has been necessary to use a differential gear for driving each couple of tracks on each side. Clutches, brakes, and tilting of tracks are discussed. The robot weighs over 10000 N, and its drive motors each have a power of 1000 W. Its maximum speed is about 0.3 m/s. Steering is by running tracks at different speeds. The frame is meant to bear a payload of 3000 N.<<ETX>>

Unilateral transmission joints with friction elastic rings

SommarioSono studiati accoppiamenti per attrito atti a trasmettere coppie torcenti in una sola direzione; per tali accoppiamenti si determina il valor massimo della coppia trasmissibile.A tale scopo, viene analizzata la configurazione di equilibrio elastico della molla elicoidale interposta tra gli alberi motore e condotto, e sono ottenute le relazioni che collegano parametri geometrici e dinamici.I risultati sono ottenuti attraverso calcoli numerici, e sono tabulati per differenti valori dei fattori fisici influenti sul funzionamento del giunto.SummaryFrictional couplings, transmitting torque in only one direction, are studied in order to find the maximum value of the transmissible torque. For this purpose, the elastic equilibrium configuration of the helical spring interposed between driver and driven shafts is analyzed, and relations between the geometrical and dynamical parameters are found. The results are obtained through numerical calculations and tabulated for different values of the influencing physical factors.

Robot Wrist Configurations, Mechanisms and Kinematics

This paper discusses a general method for determining the kinematic performance of spherical robot wrists. Different wrist types considered include R-P-R (roll-pitch-roll) and P-Y-R (pitch-yaw-roll) wrists. Singularity conditions are indicated for both cases. For R-P-R wrists, singularity is defined by the ratio of the angular velocity of each motor to the velocity around the degeneracy axis. For P-Y-R wrists, singularity is identified both by analyzing the Jacobian matrix and by analyzing the relative velocities of the wrist components.

Dynamic Six Components Measurement of Robot Precision

An analysis of the robot dynamic precision by measurement of the six spatial coordinates of the geometrical error is undertaken.

Modelling and Dynamic Analysis of Fluid Powered Robots

Abstract Robots require fast response and high positioning accuracy, particularly when performing jobs like assembly or spray painting. The speed of motion is often quite, high and the, structure is Inherently less stiff than in conventional operating machines. A very precise analysis of the. dynamic behaviour of the, robotic system is therefore necessary, fluid powered robots are here examined. They are made by fluid control elements, fluid transmission ducts and actuators, and by the mechanical components of the structure. If one tries to write down the modelling equations of the system, one has to face a strongly nonlinear problem. Linearization procedures can be used only with loss of significant characters of the operating dynamics. A method for system modelling and analyzing is here shown. It takes Into account alt nonlinearities and it is flexible enough to account {on. different system configurations and feedback modes. The method employs the technique of the method of the characteristics for the fluid transmission tines; the components at both ends of each duct are dealt in a way to provide the boundary conditions for the characteristic equations. The computational results show the robot performances with high accuracy; they may be also used in synthesis work, where compensations, when needed, may be achieved by adjusting some parameter values, or by Interpolating a new component, or sometimes, on the account of the system nonlinearity, by changing the input shape.

POSITIONING OF TRIDIMENSIONAL PIECES CASUALLY FED

A solution to the problem of orienting and positioning dissimmetrical mechanical pieces randomly fed is presented. It relies on simple sensory and control systems and gets its flexibility by minor hardware variations. The pieces to be oriented arrive randomly on a platform, where they are driven by cylindrical grippers inside a circle having the same radius of the circle circumscribed to the orthogonal projection of the piece on the platform. The platform is then magnetized and turned by a stepping motor until the sensors signal that the correct orientation has been obtained. The piece is then picked up and placed by a manipulator. The sensors are able to distinguish if the piece on the platform is upside down; in this case, the manipulator arm rotates around its axis to correct the lie of the piece.

Positioning of tridimensional Pieces Casually Fed

Abstract A solution to the problem of orienting and positioning dissimmetrical mechanical pieces randomly fed is presented. It relies on simple sensory and control systems and gets its flexibility by minor hardware variations. The pieces to be oriented arrive randomly on a platform, where they are driven by cylindrical grippers inside a circle having the same radius of the circle circumscribed to the orthogonal projection of the piece on the platform. The platform is then magnetized and turned by a stepping motor until the sensors signal that the correct orientation has been obtained. The piece is then picked up and placed by a manipulator. The sensors are able to distinguish if the piece on the platform is upside down; in this case, the manipulator arm rotates around its axis to correct the lie of the piece.

Some extensions of the L. S. Pontryagin maximum principle for optimum control problems

c) Optimum problems iu processes with control parameters [4]. Duration and proceeding of these processes depend upon a previous choice of a certain number of constant parameters. There is, indeed, a theorem of Pontryagin and collaborators (theorem 17 of [1]), which states the optimizing conditions for control processes with parameters, in the case when the boundaries of the time interval representing the process duration do not depend upon the parameters, and these can vary without any limits. In order to cancel these restrictions, the problem has been reconsidered in a more general shape, and a new resolving expression has been obtained. Opt imum problems with controlling parameters can be found, for instance, in the stage composition optimization of multistage missiles.