Andrea Ginammi

Design and Optimization of a PKM for Micromanipulation

The actual miniaturization trend, present in several industrial sectors, requires high performance capabilities in micromanipulation and assembly. A complete automation of these operations, by means of robots, could result in a significant cost cut in the final product. In this work we present the mechatronic design and optimization of a 3 d.o.f. Delta type PKM for micromanipulation. Starting from a reference task (pick and place with high stroke rate) the optimal links length has been determined by considering several kinematic performance indexes; afterwards the actual link sizing has been performed considering dynamic loading, also taking into account the effect of the links flexibility on end effector trajectory. A direct drive actuation has been chosen, where the motor sizing has been performed to satisfy several criteria: maximum and r.m.s. torque and maximum speed. The motor selection has been speeded up querying a database built by collecting data from the catalogues of several producer. Furthermore robot joints have been carefully designed in order to reduce backlash and friction.

Experimental activities on step motor drives

Thanks to their robustness, reliability and ease of use, step motor drives are widely used in several fields, mainly for small size automation. Step motor drives have also some well known bad running conditions related to their oscillatory behaviour and synchronism loss. In order to properly design the application, those conditions must be accurately taken into account setting-up proper mathematical models. In particular in this paper we refer to a simplified electro-mechanical model where the most of the parameters can be drawn from datasheets, while the others, as the equivalent damping factor, need experimental investigation. This paper deals with preliminary experimental activities performed on small size step motor drives for both testing the suitability of a test bench designed and developed in previous works, and outlining some remarks on the behaviour of the tested motors.

MLA Piezoelectric-Mechanical Systems: Modelling and Simulation

Multilayer actuators (MLA) are among the piezoelectric devices best suited to be introduced into fast and high-precision mechanical systems, because of their relatively large strokes and short actuation time. Several analytical models of their dynamic behaviour were developed during the last decades but none considered the real structure of the multilayer actuator. In this paper a more detailed model of a generic mechanical system driven by a piezoelectric multilayer actuator is presented. A complete description of such model is given and a comparison to existing modelling techniques is made. The behaviour of some commercially available actuators is analysed and results are discussed.