Vincenzo Niola

A study of a robotic hand with tendon driven fingers

In the present paper, a model of an underactuated robotic hand with tendon driven fingers is proposed. The aim of the project was to study the feasibility of building a mechanical hand with four or five fingers, the movement of which is achieved using a single linear actuator. The mechanism was first modelled in order to study the possible improvement in the ability of a “robotic hand” powered with a single actuator in regard to grasping objects with complex shapes and also in achieving a strong grip on objects. Next, a model of the finger was studied in order to optimize of its parameters. Finally, a five-fingered robotic hand was modelled for potential application as a human hand prosthesis. Our studies on the dynamic and kinematic behaviour of a single finger mechanism permitted us to make the first prototypes of the mechanism. In addition to modelling studies, we also present a prototype of the modelled robotic hand that was developed in order to optimize functionality and simplicity of construction.

An underactuated mechanical hand: A first prototype

In the present paper a model of an underactuated tendon driven mechanical hand is proposed. The aim of the activity was to study the possibility of realization of a mechanical hand five fingers, the movement of which is realized by the use of one only actuator. The mechanism is conceived as an hand prosthesis. The main particularity of the device essentially consist in that it is based on an adaptive scheme. In this way it is possible to obtain that the three phalanxes of each of the fingers adapt their rotation to the grasped object shape. This will be obtained by non-extendible tendons. So each finger will grasp the object surface independently on the configuration of the finger itself and independently on the configuration of the other fingers.

Advanced Image Analysis of Two-Phase Flow inside a Centrifugal Pump

The analysis two-phase flow inside centrifugal pumps is a fundamental issue in several engineering applications. This often represents a bad working condition with respect to single phase one, causing head reduction, efficiency decrease, and higher operational costs in terms of energy and money. The paper reports a numerical analysis of bubbles behavior inside centrifugal pumps. Equations regulating the air bubble motion within the rotor of a centrifugal pump have been solved considering the effects of all forces acting. Coalescence phenomena have been investigated too, in order to identify how gas zone presence in the rotor can lead to anomalous working condition. Results are reported in graphs and diagrams varying bubble dimension and water flow rate. An experimental approach to visualize the two-phase flow field inside the impeller is presented too. Images have been acquired, elaborated, compared with numerical results, and discussed in order to understand the interaction between gas phase and liquid phase and to correlate this behavior with the energy dissipation phenomena for a centrifugal pump.

Influence of the Tendon Design on the Behavior of an Under-Actuated Finger

An investigation on the influence of the design parameters of the tendon system on the behavior of an under-actuated finger is presented. The study was carried on by simulations with Working Model 2D™ and by an experimental apparatus.

An application of vision systems to the path planning of industrial robots

In this paper the early results on the possibility to use a video system for the robots trajectories planning is presented. By means of this application it is possible to plan the trajectories by a PC monitor, just clicking with the mouse on the monitor. In order to obtain a three dimensional vision a couple of cameras has been used. A software was developed that by means of each couple of frames make possible to select a desired point in the work space, obtaining three cartesian coordinates. These last are given to the control system and recorded by this last. Finally the control system will move the robot in a work cycle that is described by means of the points selected and recorded as described above. Tests have been carried on with a robot prototype that was designed and built at our Laboratory and showed a very good behaviour of the system.

A stretchable, conductive rubber sensor to detect muscle contraction for prosthetic hand control

Recently, many type of prosthetic hands have been proposed. Nonetheless, any active prosthesis needs patients physiological signals to be controlled. Electromyography is one of the most used signals to control prostheses. However, EMG needs electrodes in contact with patients skin. This study aims to test an alternative, easy to wear sensor able to detect muscle contraction and to control hand prosthesis as well. The new sensor consists of a conductive rubber cord that changes its electrical resistance when stretched. The rubber cord was enclosed in a soft fabric cuff that can be easily worn by the patient. No electrical contact between the cord and the patient is needed. Simultaneous recordings of EMG and the correspondent rubber cord resistance were carried out in order to test the relationship between the two signals and to assess the effectiveness of proportional control of the prosthesis motor. A simple 3D printed, under-actuated prosthetic hand was connected to the new sensor. Results show that the new sensor offers a control signal very similar to the EMG envelope and it is able to provide both on-off and proportional control of the prosthesis.

Design, Modelling and Prototyping of a Mechanical Hand for Prosthetic Purposes

In this paper the design, modelling and prototyping of a mechanical hand for prosthetic purposes are presented. In particular, the development of the project is presented, with the subsequent choices made to reach the prototyping step. In the last part of the paper the results of some tests are also shown, in order to verify the design choices.

Video System in Robotic Applications

The “Artificial Vision” permits industrial automation and system vision able to act in the production activities without humane presence. So we suppose that the acquisition and interpretation of the imagines for automation purposes is an interesting topic. Industrial applications are referred to technological fields (assembly or dismounting, cut or stock removal; electrochemical processes; abrasive trials; cold or warm moulding; design with CAD techniques; metrology), or about several processes (control of the row material; workmanship of the component; assemblage; packing or storages; controls of quality; maintenance). The main advantages of these techniques are: 1. elimination of the human errors, particularly in the case of repetitive or monotonous operations; 2. possibility to vary the production acting on the power of the automatic system (the automatic machines can operate to high rhythms day and night every day of the year); 3. greater informative control through the acquisition of historical data; these data can be used for successive elaborations, for the analysis of the failures and to have statistics in real time; 4. quality control founded on objective parameters in order to avoid dispute, and loss of image. The use of a vision system in a robot application, it concurs to increase the robots ability to interact with their work space, to make more efficient their management. In this chapter some “Artificial Vision” applications to robotics are described: • robot cinematic calibration; • trajectories recording; • path planning by means of vision system; • solid reconstruction with a video system on a robot arm.

Experimental Measurement of Underactuated Robotic Finger Configurations via RGB-D Sensor

Underactuated robotic systems need suitable experimental methods able to measure their small and low-weight component dynamics. Depth sensors represent a valuable strategy to develop quantitative approaches to study the behavior of these systems. Here, an experimental application of markerless vision technique is proposed employing the low-cost and low-resolution Kinect depth sensor to compute the kinematics of an underactuated robotic finger.

Analytical Study for the Capability Implementation of an Underactuated Three-Finger Hand

Combining the simple design with the implementation capability of underactuated hands is a challenging task. In this context, it is necessary to find a compromise between the number of actuators, the grasping abilities and the control strategy. Here, an analytical study is proposed to improve the precision grasping performance together with a simple control strategy of a three-finger underactuated hand.