Maurizio Ruggiu

In-pipe inch-worm pneumatic flexible robot

A pneumatic flexible robot prototype for pipes inspection was built. A dynamic model which takes into account the flexibility, damping and friction was developed. Numerous experiments were carried out in order to characterize the robot and in order to provide the input for the numerical model. The model was validated by comparing the experimental and numerical robot gait in time. The robot motion for different pipes network geometry is presented.

Characterization and modeling of air muscles

Abstract Two flexible pneumatic actuators, McKibben and straight fiber, were analyzed. The muscles were modeled by finite element method. The numerical models take into account the non-linearity of the expanding rubber inner tube, and of the mechanism for transferring load to the braided cords surrounding the tube. Because of its own fabrication, McKibben muscle model may capture the initial backslash between rubber tube and cords. Despite of the McKibben specimen, a straight fiber muscle prototype was fabricated on purpose in the laboratory. In order to validate the numerical models, numerous experimental tests were carried out. The numerical results showed a good agreement with the data measured experimentally in terms of muscle pull force and of its deformed shape. Finally, the models of two muscles similar in terms of input energy allow their performances to be compared.

A Two Degree of Freedom Gripper Actuated by SMA with Flexure Hinges

A gripper prototype was designed and built. It is made by a rigid structure articulated by compliant hinges. Its kinematics consists of both parallel and angular finger motion. The movements were designed to be independent from each other and auto-adaptive as well. The motions were driven by Ni-Ti shape memory alloy (SMA) wires. The recovery position is achieved by the elastic force exerted by the flexure hinges in the case of parallel motion and by an axial spring in the case of angular motion. Both the actuators and the hinges were experimentally characterized by suitable test rigs. The gripper prototype was tested and it showed to be able to reach the design performances.

A MECHANICAL DEVICE FOR HARVESTING CROCUS SATIVUS (SAFFRON) FLOWERS

A prototype for harvesting Crocus Sativus (saffron) flowers was developed. The device has a simple design and is capable of performing the cutting procedure with just one actuated degree of freedom. A cam driven by a revolute motor drags the flower towards the cutting area where the flower is severed. The operating principle and some theoretical analyses of the device are presented along with details of the mechanical design and the results of laboratory tests. These are instrumental for developing the final design, its geometry, kinematics and kinetics. Finally, field tests are described.

Low cost resistive based touch sensor

Abstract In this paper a resistive based sensor is presented. The transducer is made of a rubber sample as compliant material with a graphite film spread on the whole surface as conductive material. An extensive experimental program was carried out in order to characterize the device. Both quasi-static and fully dynamic responses were measured by means of dedicated test rigs. Moreover, a neural network model of the sensor was developed in order to capture its transfer function. A good agreement was found between the sensor responses obtained by the experiments and these according to the numerical model.

Fish And Ships: Can Fish Inspired Propulsion Outperform Traditional Propulsion Based Systems?

Fish propulsion mechanisms are becoming a major research topic. The aim is to better understand the reasons for the high swimming abilities of marine creatures, and to investigate the possibility of applying fish-like propulsion to surface and underwater vehicles. In this paper, 2 mathematical models were developed and applied to predict thrust in oscillating tail propulsion. A fish prototype and thrust measuring equipment were developed in order to assess the accuracy and reliability of the analytical models used. Findings and comparison results are discussed.

On the Kinematics of the Gait with Jumping Stilts

This work deals with the kinematic analysis of the gait cycle of a subject fitted with jumping stilts. A motion capture analysis was conducted by recording the trajectory of the subject’s free-flying hoof during a complete gait cycle. A six-degrees of freedom serial chain was used to simulate the subject’s legs kinematic on the sagittal plane. The positions and velocities of the subject’s free-flying hoof obtained from the photo-frames of the video and from the kinematic model was used to validate the model.

A Mechanism for Converting Revolute Motion into Harmonic Rotating Motion

Abstract In this paper, we describe the design and construction of a cam mechanism to convert a revolute motion into a symmetrical oscillating harmonic movement. The mechanism consists of a harmonic cam driven by a revolute electric motor joined to a follower by a desmodromic constraint. The linear reciprocating motion of the follower was then transmitted, by a rack-pinion mechanism, to a final device that oscillates symmetrically. The entire mechanism was designed to be used as the propeller of a boat model. The final device, indeed, will be connected to a tail that propels the boat. On account of the peculiar application for which the device is intended, the need for symmetrical motion of the tail—either in a cycle, from side to side and return, or in a semi-cycle, from side to side—becomes evident. The analysis of the kinematics and the analytic model of its dynamics are presented throughout the paper. A numerical model, able to capture the mechanism performance when the friction effects were taken into account and to predict its behavior when the motion conditions were varied, was developed as well. During construction of the mechanism, efforts were made to reduce friction, weight, and the overall dimensions. Several laboratory tests were carried out in order to clarify the mechanisms performance. Particular care was dedicated to measure the coefficient of friction between the materials of the desmodromic constraint and to the kinematics parameters for validating the design requirements. The dedicated test benches arranged and the data collected from the tests are presented in the paper.