Test rig for friction force measuremets in pneumatic components and seals

This article describes the design of a new test rig for measuring the friction force in pneumatic components and seals. The test rig was designed in order to measure both the overall friction force in a pneumatic cylinder or a valve as a whole, and the single contribution to friction force caused by the sliding seals. To this end, special fixtures and devices were designed and manufactured in order to measure the friction force in piston seals, rod seals and cartridge valve seals individually. Results of friction measurements carried out on pneumatic cylinders with similar characteristics but produced by different manufacturers are presented and compared. A test procedure and a methodology, in order to separate the contributions of the individual seals from the overall friction of the cylinders, is presented

Fuzzy Logic Position Control of a Shape Memory Alloy Wire

Due to the thermomechanical characteristics of Shape Memory Alloy wires, it is important to develop control systems in order to design new applications for these smart materials. This work presents three SMA wire position controls: a classic PD control with PWM modulation is compared to two different fuzzy logic controls. They are implemented on a SMA wire (Flexinol®)with a diameter of 250 mm and a length of about 200 mm. The so called Fuzzy logic is particularly suitable in case of uncertain conditions and in presence of data acquisition noise and it is widely used to model and control time dependent and/or non linear processes. The experimental tests comprise square wave response tests, sinusoidal wave tests and multiple step response tests. Interesting results are a maximum error during stability phase with the fuzzy logic control of about 2%, four times smaller than that obtained with the PD control, with reduced fluctuations amplitude. The PD control with fuzzy supervisor is a control more simple than the fuzzy control and lead to similar results for the sinusoidal tests and multiple step response tests, with fluctuation amplitude of about 0,01 mm, much more less than those observed with the PD or the fuzzy control

High-performance device for air interlacing of a yarn and corresponding method

Abstract A device for air interlacing of a yarn , comprising an interlacing chamber , a first entrance channel for receiving the yarn at the device entrance and feeding it to the interlacing chamber , and a second exit channel for receiving the yarn from the interlacing chamber and releasing it at the device exit, in which the interlacing chamber is delimited by a first emitting wall bearing a nozzle for the emission of a continuous jet of compressed air , and a second deflecting wall , opposite the first wall , suitable for receiving and deflecting the jet of compressed air emitted by the nozzle and intersecting the yarn to be interlaced, and in which the second deflecting wall is concave in shape both on a transversal plane and on a longitudinal plane with respect to the feeding path of the yarn through the devic

Study of the press forming mechanism of a thermoforming machine

The paper presents kinematic and dynamic investigations of the main press forming mechanism of a thermoforming machine. A multibody analysis of this press forming mechanism, which lifts and rotates a press bed, was carried out. Press bed lifting, which is necessary to form the component, is performed by means of a first rod and toggle mechanism. Press bed rotation to eject the formed component is produced by means of a second rod and must be appropriately shifted. These rods are oscillating followers driven by cams, making it possible to precisely define trajectories as a function of the motor shaft rotation angle. Analysis is performed by numerically solving the equations of motion. Cam synthesis on the basis of the oscillating followers' trajectories makes it possible to obtain cam profiles in order to evaluate pressure angles and check that there is no undercutting. System dynamics is investigated in order to evaluate motor torque and analyse internal stresses on the hinges. In addition, some experimental results and those obtained with the dynamic model are compared. Performance improvement of the actual machine is carried out by modifying the trajectory of the press bed by means of a numerical code at the purpose developed. This approach is more convenient than the use of a commercial multibody code, which is not specifically built for parametric studies

Soft Pneumatic Actuators for Rehabilitation

Pneumatic artificial muscles are pneumatic devices with practical and various applications as common actuators. They, as human muscles, work in agonistic-antagonistic way, giving a traction force only when supplied by compressed air. The state of the art of soft pneumatic actuators is here analyzed: different models of pneumatic muscles are considered and evolution lines are presented. Then, the use of Pneumatic Muscles (PAM) in rehabilitation apparatus is described and the general characteristics required in different applications are considered, analyzing the use of proper soft actuators with various technical properties. Therefore, research activity carried out in the Department of Mechanical and Aerospace Engineering in the field of soft and textile actuators is presented here. In particular, pneumatic textile muscles useful for active suits design are described. These components are made of a tubular structure, with an inner layer of latex coated with a deformable outer fabric sewn along the edge. In order to increase pneumatic muscles forces and contractions Braided Pneumatic Muscles are studied. In this paper, new prototypes are presented, based on a fabric construction and various kinds of geometry. Pressure-force-deformation tests results are carried out and analyzed. These actuators are useful for rehabilitation applications. In order to reproduce the whole upper limb movements, new kind of soft actuators are studied, based on the same principle of planar membranes deformation. As an example, the bellows muscle model and worm muscle model are developed and described. In both cases, wide deformations are expected. Another issue for soft actuators is the pressure therapy. Some textile sleeve prototypes developed for massage therapy on patients suffering of lymph edema are analyzed. Different types of fabric and assembly techniques have been tested. In general, these Pressure Soft Actuators are useful for upper/lower limbs treatments, according to medical requirements. In particular devices useful for arms massage treatments are considered. Finally some applications are considered

Indirect contact pressure evaluation on pneumatic rod seals

This paper deals with the experimental evaluation of contact pressure at the interface between an elastomeric rod seal for pneumatic cylinders and its metallic counterpart without interposing any intrusive measuring device. A new test bench, which is able to measure the radial force exerted by a rod seal displaced at constant velocity on a sensorized portion of a cylinder rod over time, was designed and manufactured. The seal was pressurised to reproduce actual working conditions. A data postprocessing methodology was developed for an indirect evaluation of contact pressure starting from the experimental data set of the radial force exerted by the seal on the rod. At first, the measured radial force signal was filtered and properly fitted obtaining a differentiable function; then, contact pressure distribution was computed as a function of radial force time derivative, seal velocity and rod diameter. Preliminary experimental results are presented

Nuevo sistema de carga y descarga en grúas portacontenedores

El transporte de mercancías vía marítima es, actualmente, uno de los más utilizados. Por ello, los puertos se ven implicados en la búsqueda de soluciones para mejorar el proceso de carga y descarga de contenedores, con el fin de optimizar el tiempo de la acción aumentando de este modo la productividad. En concreto, el puerto SECH de Génova en colaboración con el Departamento de Mecánica del Politécnico de Turín, se encuentran estudiando diversos métodos para alcanzar esta finalidad. El objetivo de este proyecto es dar una solución con el fin de obtener esa mejora temporal y verificar que es posible su realización. Se han tenido en cuenta las peculiaridades del puerto para desarrollar un sistema que se adapte a ellas. El punto de partida de este trabajo es otro con título “Verifica di fattibilità di un sistema automatico di trasferimento container su vagone ferroviario” elaborado por Stefano Colombo (2008), en el Politécnico de Turín. En la primera parte del estudio, en primer lugar, se analizan las ideas más innovadoras encontradas tras revisar varias bases de patentes y múltiples publicaciones científicas sobre este tópico. En segundo lugar, se han realizado unos cálculos sobre la grúa tomada como punto de partida con el fin de predimensionar sus elementos, ya que sólo se aportaron sus diseños en 3D. En una segunda parte, se han generado dos nuevas ideas posibles para agilizar el proceso citado anteriormente. Ambas soluciones crean un nuevo nivel de trabajo dentro de la grúa. Éstas permiten automatizar el proceso de almacenaje de los contenedores o descargarlos directamente sobre los trenes que se aproximan a las grúas de puerto. Éstos nuevos sistemas propuestos se sirven de elementos hidráulicos y bandas transportadoras con el objetivo de agilizar todos los movimientos. Se ha realizado un predimensionamiento de todos ellos. Además, se ha generado su diseño en 3D con la herramienta de CAD, SOLIDWORKS. Con la misma, se han creado animaciones para visualizar mejor el movimiento de los mismos. En tercer lugar, se ha verificado también la reducción temporal en la carga/descarga de los nuevos sistemas propuestos, desde el punto de vista del movimiento del spreader. Por último, se ha creado un estudio según el Método de los Elementos Finitos (MEF) con el fin de comprobar la resistencia mecánica del segundo sistema propuesto, ya que ese diseño es el más interesante en la reducción de tiempo. En este estudio se han utilizado los programas PATRAN y ABAQUS, para mallar y calcular respectivamente. Como conclusión, por una parte, se verifica la reducción en el tiempo de carga y descarga, obteniéndose nuevos sistemas de “handling” que permiten una automatización del proceso con el consiguiente ahorro temporal. Por otra parte, se verifica la resistencia mecánica de todo el conjunto de la grúa, observándose cuales son las secciones con mayor solicitación mecánica

An Active Exoskeleton Called P.I.G.R.O. Designed for Unloaded Robotic Neurorehabilitation Training

The development of innovative robotic devices allows the design of exoskeletons for robotic neurorehabilitation training. This paper presents the active exoskeleton called pneumatic interactive gait rehabilitation orthosis (P.I.G.R.O.), developed by the authors. The main innovative characteristic of this prototype is its design for fully unloaded robotic neurorehabilitation training, specific for brain-injured patients. It has six degrees of freedom (DOF) in the sagittal plane, an active ankle joint (removable if it is required); a wide range of anthropometric regulations, both for men and for women; a useful human machine interface (HMI); and an innovative harness system for the patient for the unloaded training. It is realized using light and strong materials, and it is electropneumatically controlled. In particular the authors also studied and defined some innovative input control curves useful for the unloaded training. In this paper, the main characteristics and innovations of P.I.G.R.O. are presented