Modelling the temperature in joint friction of industrial manipulators

In this paper, a new model for joint dynamic friction of industrial robot manipulators is presented. In particular, the effects of the temperature in the joints are considered. A polynomial-based model is proposed and the parameter estimation is performed without the need of a joint temperature sensor. The use of an observer is then proposed to compensate for the uncertainty in the initial estimation of the temperature value. A large experimental campaign show that the model, in spite of the simplifying assumptions made, is effective in estimating the joint temperature and therefore the friction torque during the robot operations, even for values of velocities that have not been previously employed

On the Inclusion of Temperature in the Friction Model of Industrial Robots

This paper deals with a modelling technique that takes into account the effects of the temperature in the joint friction of industrial robot manipulators. In particular, it is shown that a general friction model can be suitably modified by explicitly considering the temperature as a parameter. This allows to estimate the friction term accurately in different operating conditions without the direct measurement of the joint internal temperature, which makes the overall technique suitable to apply in practical cases. Experimental results show the effectiveness of the methodology

Modelling the temperature in joint friction of industrial manipulators

In this paper, a new model for joint dynamic friction of industrial robot manipulators is presented. In particular, the effects of the temperature in the joints are considered. A polynomial-based model is proposed and the parameter estimation is performed without the need of a joint temperature sensor. The use of an observer is then proposed to compensate for the uncertainty in the initial estimation of the temperature value. A large experimental campaign show that the model, in spite of the simplifying assumptions made, is effective in estimating the joint temperature and therefore the friction torque during the robot operations, even for values of velocities that have not been previously employed

Manipulation of micro-components using vacuum grippers.

SUMMARY. During the past decades several microproducts have been fabricated for a great variety of applications in the traditional fields, including the medical and biomedical sectors, automotive, aeronautics and aerospace, Information Technology and telecommunication as well as in more innovative areas, such as household appliances, entertainment and sport equipment. Nevertheless, hybrid three dimensional micro products have still great difficulty in penetrating the market, mainly due to the limits of the fabrication processes that require manipulation and final assembly of microcomponents. These processes, being not yet automated, strongly affect the cost of products. Therefore, new market perspectives can be reached automating the assembly phase. The main challenge is due to the new physical scenario that appears when dealing with the assembly of millimetric and sub-millimetric parts. Indeed, at the microscale the high surface to volume ratio leads to the predominance of the superficial forces (e.g. electrostatic, van der Waals and surface tension forces) over the gravitational force; this results in an unpredictable behaviour of the traditional manipulating mechanisms, whereas an efficient and precise control of the grasp and release of thousands of microscopic and fragile parts is required. For this reason the downscaling of traditional handling strategies and the development of new handling techniques require further studies. Several solutions can be found in literature, with their advantages and limitations, i.e.: friction and jaw microgrippers, magnetic and electrical fields used to levitate objects, adhesive grippers exploiting capillary force. Also vacuum grippers can be miniaturized. Due to their intrinsic simplicity, vacuum grippers are very cheap and appear a promising solution for industrial applications, if some improvements are carried out. In this context, an experimental setup for the automatic manipulation of microcomponents through some vacuum grippers was developed. Moreover, an innovative design of a nozzle for a vacuum gripper was fabricated and tested, comparing its performance with traditional needles. The design was conceived in order to reduce the frequency of occlusions of the nozzle and handle a wide range of particles. The tests described in this paper concern mainly the success and the precision of the release of objects from the gripper. Indeed, this is one the crucial aspect of micromanipulation because microparts tend to stick to the gripper preventing the successful performance of manipulation tasks

A Novel Method and Mechanism for Micro-Sphere Singularization

The paper presents an innovative mechanism for the singularization of micro-spheres, which can be effectively employed in a diverse range of robotized applications in micro-electronics and micro-mechanics. Many miniaturized devices are currently being developed and consist of different micro-components to be precisely assembled. The demanding product and process requirements can be met by automating the assembly phases, which include sorting and feeding the micro-components. Therefore, accurate, high-throughput, and modular mechanisms and tools able to supply a number of micro-components, or even a single element for the subsequent operations, play a significant role. In this context, this work focused on the development of a novel strategy for separating a single component from an unstructured stock of identical parts, in particular of micro-spheres with diameters of 0.2–1 mm. Suitable expedients were considered to overcome the adhesive effects that can become significant at the micro-scale due to the very small size and low mass of the micro-spheres. The paper describes the operating principle and the actuation strategies of the mechanism. The design and the development of a prototype for singularizing micro-spheres with a diameter of 0.6 mm are thoroughly discussed. Finally, the results of experimental singularization tests demonstrate the method effectiveness and the mechanism performance