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

Detailed Study of Amplitude Nonlinearity in Piezoresistive Force Sensors

This article upgrades the RC linear model presented for piezoresistive force sensors. Amplitude nonlinearity is found in sensor conductance, and a characteristic equation is formulated for modeling its response under DC-driving voltages below 1 V. The feasibility of such equation is tested on four FlexiForce model A201-100 piezoresistive sensors by varying the sourcing voltage and the applied forces. Since the characteristic equation proves to be valid, a method is presented for obtaining a specific sensitivity in sensor response by calculating the appropriate sourcing voltage and feedback resistor in the driving circuit; this provides plug-and-play capabilities to the device and reduces the start-up time of new applications where piezoresistive devices are to be used. Finally, a method for bypassing the amplitude nonlinearity is presented with the aim of reading sensor capacitance

Sistema y procedimiento de control para manipuladores

Sistema y procedimiento de control para manipuladores. Basado en guantes (5) dotados de sensores, que permite a un operario (6) controlar cualquier manipulador (4) con uno o más grados de libertad, coordinando su movimiento de acuerdo con la magnitud, dirección y sentido de la fuerza aplicada por el operario (6), ejercida sobre la estructura del manipulador (4) o sobre la carga movilizada (406). Dicho sistema de control comprende al menos un guante (5) dotado de sensores, un computador (411), un receptor inalámbrico (412) y unos variadores de frecuencia (413). Cada guante (5) posee en su zona dorsal un sistema de posicionamiento dactilar (2) que mide la flexión y abducción de los cinco dedos, un sistema de posicionamiento espacial (7) que mide la posición y orientación absoluta del guante (5) y por ende de la mano (1) en el espacio, y en su zona palmar un sistema de medición de fuerza (3) que mide las fuerzas aplicadas por el operario (6).Peer reviewedConsejo Superior de Investigaciones Científicas (España)A1 Solicitud de patentes con informe sobre el estado de la técnic

Statistical process control of commercial force-sensing resistors

The manufacturing and characterization of polymer nanocomposites is an active research trend nowadays. Nonetheless, statistical studies of polymer nanocomposites are not an easy task since they require several factors to consider, such as: large amount of samples manufactured from a standardized procedure and specialized equipment to address characterization tests in a repeatable fashion. In this manuscript, the experimental characterization of sensitivity, hysteresis error and drift error was carried out at multiple input voltages () for the following commercial brands of FSRs (force sensing resistors): Interlink FSR402 and Peratech SP200-10 sensors. The quotient between the mean and the standard deviation was used to determine dispersion in the aforementioned metrics. It was found that a low mean value in an error metric is typically accompanied by a comparatively larger dispersion, and similarly, a large mean value for a given metric resulted in lower dispersion; this observation was held for both sensor brands under the entire range of input voltages. In regard to sensitivity, both sensors showed similar dispersion in sensitivity for the whole range of input voltages. Sensors’ characterization was carried out in a tailored test bench capable of handling up to 16 sensors simultaneously; this let us speed up the characterization process

Experimental study to improve "Federica" prosthetic hand and its control system

Modern 3D printing technologies and wide availability of microcontroller boards allow to make active prosthetic devices in a simple way. This is the case of “Federica”, a very low-cost, under-actuated, active hand prosthesis. The five fingers of the prosthesis are moved by a single motor through inelastic tendons. The control system of the prosthesis is proportional to muscle contraction: firstly, EMG was used, then mechanical sensors that measure muscle volumetric variation were successfully utilized. This prosthesis proved to be particularly energy efficient and fast; it provided a general grasp function by adapting the exerted forces, thus allowing to easily catch even deformable objects. This study presents further analyses and design improvements of this prosthesis. In particular, a new, extremely simple but effective conditioning system of a force sensor resistor was presented and tested. In addition, the actual three-dimensional kinematics of a single finger was captured by means of high frame rate cameras and then analyzed. The new sensor conditioning system was characterized. It proved to be as effective as the EMG envelope to proportionally control the hand prosthesis motion, and it allowed an easier connection to common microcontroller boards. Kinematic analysis allowed to accurately reconstruct the actual phalanges motion over time

Underlying Physics of Conductive Polymer Composites and Force Sensing Resistors (FSRs) under Static Loading Conditions

Conductive polymer composites are manufactured by randomly dispersing conductive particles along an insulating polymer matrix. Several authors have attempted to model the piezoresistive response of conductive polymer composites. However, all the proposed models rely upon experimental measurements of the electrical resistance at rest state. Similarly, the models available in literature assume a voltage-independent resistance and a stress-independent area for tunneling conduction. With the aim of developing and validating a more comprehensive model, a test bench capable of exerting controlled forces has been developed. Commercially available sensors—which are manufactured from conductive polymer composites—have been tested at different voltages and stresses, and a model has been derived on the basis of equations for the quantum tunneling conduction through thin insulating film layers. The resistance contribution from the contact resistance has been included in the model together with the resistance contribution from the conductive particles. The proposed model embraces a voltage-dependent behavior for the composite resistance, and a stress-dependent behavior for the tunneling conduction area. The proposed model is capable of predicting sensor current based upon information from the sourcing voltage and the applied stress. This study uses a physical (non-phenomenological) approach for all the phenomena discussed here

A Novel and Inexpensive Approach for Force Sensing Based on FSR Piezocapacitance Aimed at Hysteresis Error Reduction

Force-sensing resistors (FSRs) are inexpensive alternatives to load cells. They are suitable for applications where noninvasive devices are needed to measure force, stress, or pressure. However, they have been proved to be hysteresis prone and offer nonrepeatable readings due to their highly voltage-dependent electrical resistance. A piezocapacitive effect has been found as an alternative phenomenon that is able to offer force-dependent readings of capacitance with less hysteresis error. Also, this capacitance is not dependent on voltage, which also improves repeatability in force measurements. Since measuring capacitance is more expensive than resistance, the least costly conditioning circuitry is desired. An inexpensive alternative using an LM555 that oscillates depending on capacitance is here presented. Hysteresis and repeatability errors have been reduced for a widespread-used force-sensing resistor brand

Practical Considerations towards Repeatable Measurements in Force Sensing Resistors (FSRs)

The usability of Force Sensing Resistors (FSRs) has been thoroughly demonstrated in [...