Design of a Lightweight, Cost Effective Thimble-Like Sensor for Haptic Applications Based on Contact Force Sensors

This paper describes the design and calibration of a thimble that measures the forces applied by a user during manipulation of virtual and real objects. Haptic devices benefit from force measurement capabilities at their end-point. However, the heavy weight and cost of force sensors prevent their widespread incorporation in these applications. The design of a lightweight, user-adaptable, and cost-effective thimble with four contact force sensors is described in this paper. The sensors are calibrated before being placed in the thimble to provide normal and tangential forces. Normal forces are exerted directly by the fingertip and thus can be properly measured. Tangential forces are estimated by sensors strategically placed in the thimble sides. Two applications are provided in order to facilitate an evaluation of sensorized thimble performance. These applications focus on: (i) force signal edge detection, which determines task segmentation of virtual object manipulation, and (ii) the development of complex object manipulation models, wherein the mechanical features of a real object are obtained and these features are then reproduced for training by means of virtual object manipulation

Force sensing glove for quantification of joint torques during stretching after spinal cord injury in the rat model.

An increasing amount of healthcare resources is used for the treatment and prevention of contractures in patients with spinal cord injury (SCI), with stretch and passive movements remaining the most prominent intervention methods. The results of both clinical trials and animal studies in recent years have shown traditional stretch therapies to be ineffective at preventing contracture and joint immobility, and have encouraged further emphasis on evidence-based practices. However, these studies only analyzed one aspect of stretching, dosage, and failed to look at the characteristic of joint torque. Recent clinical trials have unearthed the fact that the joint torque application of therapeutic stretches in the clinic not only vary by therapist, but also can be well beyond the range of torques tolerated by able-bodied individuals. A glove device utilizing force sensing resistors (FSRs) was developed to gauge joint torques. Coupled with a custom National Instruments’ LabVIEW program, the device was able to accurately measure forces, and eventually torques, applied during stretching. This study sought to explain what range of torques were being applied during stretching after SCI in the rat model in the hopes of understanding how to administer safe, effective therapeutic stretches. Six adult female Sprague-Dawley rats were mildly contused at T9 using the NYU impactor device with a 12.5 g-cm weight drop. n=2 rats were stretched 2 days per week and n=2 rats were stretched once per week using an eight minute protocol, for the first 5 weeks post-injury while controls (n=2) received no stretch therapy. Briefly, the tibialis anterior (TA) and triceps surae (TS) muscle groups were stretched by two therapists bilaterally for a minute each, totaling 4 minutes of stretch per rat per day. Kinematic assessments of stretching were accompanied by force measurement data and were used to generate comparisons between therapeutic torque and end range of motion (ROM) of the ankle. The data suggests that both once and twice per week stretching regimens were not enough to inhibit locomotor recovery or elicit a noticeable change in end ROM in such a mild injury model. There were noticeable differences in torques applied during stretching by different therapists, confirming the findings of previous studies. More importantly, the data showed that immediately after injury the normal end ROM can be achieved by applying less torque. The torque necessary to reach the end ROM increases to baseline values by week 5, potentially due to a return of the stretch reflex during spinal shock. This study urges other aspects of stretching therapy to be considered and suggests a tool for therapists to quantitatively apply safe and consistent stretching therapies to patients

Soft pneumatic devices for blood circulation improvement

The research activity I am presenting in this thesis lies within the framework of a cooperation between the University of Cagliari (Applied Mechanics and Robotics lab, headed by professor Andrea Manuello Bertetto, and the research group of physicians referencing to professor Alberto Concu at the Laboratory of Sports Physiology, Department of Medical Sciences), and the Polytechnic of Turin (professor Carlo Ferraresi and his equipe at the Group of Automation and Robotics, Department of Mechanical and Aerospace Engineering) This research was also funded by the Italian Ministry of Research (MIUR – PRIN 2009). My activity has been mainly carried on at the Department of Mechanics, Robotics lab under the supervision of prof. Manuello; I have also spent one year at the Control Lab of the School of Electrical Engineering at Aalto University (Helsinki, Finland). The tests on the patients were taken at the Laboratory of Sports Physiology, Cagliari. I will be describing the design, development and testing of some soft pneumatic flexible devices meant to apply an intermittent massage and to restore blood circulation in lower limbs in order to improve cardiac output and wellness in general. The choice of the actuators, as well as the pneumatic circuits and air distribution system and PLC control patterns will be outlined. The trial run of the devices have been field--‐tested as soon a prototype was ready, so as to tune its features step--‐by--‐ step. I am also giving a characterization of a commercial thin force sensor after briefly reviewing some other type of thin pressure transducer. It has been used to gauge the contact pressure between the actuator and the subject’s skin in order to correlate the level of discomfort to the supply pressure, and to feed this value back to regulate the supply air flow. In order for the massage to be still effective without causing pain or distress or any cutoff to the blood flow, some control objective have been set, consisting in the regulation of the contact force so that it comes to the constant set point smoothly and its value holds constant until unloading occurs. The targets of such mechatronic devices range from paraplegic patients lacking of muscle tone because of their spinal cord damage, to elite endurance athletes needing a circulation booster when resting from practicing after serious injuries leading to bed rest. Encouraging results have been attained for both these two categories, based on the monitored hemodynamic variables

Modelado de sensores piezoresistivos y uso de una interfaz basada en guantes de datos para el control de impedancia de manipuladores robóticos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Arquitectura de Computadores y Automática, leída el 21-02-2014Sección Deptal. de Arquitectura de Computadores y Automática (Físicas)Fac. de Ciencias FísicasTRUEunpu