Giancarlo Orengo

A novel application method for wearable bend sensors

Bend sensors fundamental characteristic is to furnish an electrical resistance value related to the angle they are bent. This feature can be successfully exploited to realize wearable systems capable to measure human static and dynamic postures. In particular some efforts have been made to determine finger joint movements of human hands and it has been demonstrated the feasibility of using the so called data glove system as a goniometric device. The repeatability of such system is quite good for general purposes but it is still not sufficient for specific applications (for instance in virtual surgery). So here we introduce a novel application method of bend sensors and demonstrate how it can be useful to improve the system repeatability.

Wireless data glove system developed for HMI

Human Machine Interfaces support users to interact or simply control any kind of devices founded on machinery basis. Very simple and common interfaces are represented by the mouse and keyboard tools by which a user interact with the personal computer “machine”. It is however evident how these tools can be particularly “limited” since they “act” only in a 2D superficial environment and cannot provide an immersive experience. So in the latter years new kind of interfaces have been investigated in order to expand the user capabilities in a 3D space, then increasing the realism degree too. In this paper we deal with a new kind of these interfaces. In fact we developed a sensorized glove capable to measure all human hand Degree of Freedom (DoF), “translating” them into commands for personal computers.

Characterization of piezoresistive sensors for goniometric glove in hand prostheses

Piezoresistive sensors can be successfully adopted in many field where bend angles need to be measured. In particular, attention must be paid for increase the sensor numbers, applied to body-sample, which give parallel information on the movement activity. The possibility to capture information from the sensors adopting wireless technology can allow the increasing of sensor number, and the removing of wire ties between sensors and the central processor unit in normal human motion. We utilized these sensors to develop an instrumented glove to measure human joint fingers. The great advantage in applications of piezoresistive sensors rely on their pliability, sensitivity and cheapness. In any case, for effective results, it is mandatory a complete electrical sensor characterization, which lacks in literature and therefore it is the aim of this work.

Modeling Wearable Bend Sensor Behavior for Human Motion Capture

The possibilities offered by variable resistance bend sensors, applied as wearable devices on body garments, to recover human joint bend angles for body segment movement tracking, have been investigated, underlying their advantages and drawbacks in real-time applications. Due to their pliability, sensitivity, and cheapness, they could be a valid alternative to movement analysis systems, based on optoelectronic devices or inertial electronic sensors. This paper suggests a new method for sensor characterization under fast bend and extension movements, to extract few parameters of a synthetic model, which provide to the users the chance to foresee their electrical performance in different applications. The sensor and their extracted models were applied to register the human knee rotation during a gait cycle, either at slow speed (83 deg/s) for a walking pattern at 5 km/h, and at high speed (650 deg/s) for a running pattern of a sprinter at 10 m/s, and finally the finger joint rotations at their maximum angular velocity (900 deg/s). This was done for a twofold purpose: from one hand, to assess the model capability to predict the sensor performance, tracking human body segment rotations at different speed, without the need of measurement; from the other hand, to recover in real time the actual sensor rotation from its resistance measurement, especially in high speed applications, where its response is distorted. With this technique, the mean error decreases from 22.5° to 3.7° in the worst case.

Advanced characterization of piezoresistive sensors for human body movement tracking

Due to their pliability, sensitivity and cheapness, piezoresistive sensors can be usefully adopted to recover joint bend angles in human body movement tracking. After providing quasi-static and dynamic electrical characterization of piezoresistive sensors, the authors develop a simple and accurate RLC model fitted on sensor electrical response under fast deformation and relaxation movements, which allows to predict the actual device behavior in tracking body fast movements.

Shaping Resistive Bend Sensors to Enhance Readout Linearity

Resistive bend sensors have been increasingly used in different areas for their interesting property to change their resistance when bent. They can be employed in those systems where a joint rotation has to be measured, in particular biomedical systems, to measure human joint static and dynamic postures. In spite of their interesting properties, such as robustness, low price, and long life, the commercial bend sensors have a response which is not actually linear, as an electronic device to measure bend angles should be, to recover human posture without distortion. In this work, different interfaces for sensor device readout were analyzed and compared from the output response linearity point of view. In order to obtain a sensor characteristic as closer as possible to the ideal linear one, a way to calculate the sensor characteristic with a generalized resistive strip contour, starting from an empiric sheet resistance model, was developed, in order to find what is the more suitable nonuniform geometry.

A monolithic active notch tunable filter based on the gyrator principle

A monolithic bandstop active tunable filter has been designed and realised. The filter is based on a gyrator-type active resonator, implemented using only three active devices. The center frequency of the realised notch filter is around 1.9 GHz, with a tuning range of more than 400 MHz. Measured performances include a typical in-band rejection of more than 30 dB all over the operating bandwidth, a stopband span of less than 50 MHz, together with input/output match better than 12 dB. Positive supply only has been employed.

ELECTRONIC INTERFACE AND SIGNAL CONDITIONING CIRCUITRY FOR DATA GLOVE SYSTEMS USEFUL AS 3D HMI TOOLS FOR DISABLED PERSONS

A simple PC screen can be considered as an interface of a virtual environment where an user can move objects and interact with them. The interaction tools can be simply a virtual mouse or a keyboard. But it is evident how these tools cannot provide an immersive experience since the bi-dimensionality of the screen. So in the latter years the virtual reality is becoming more and more accomplished by new hardware interfaces capable to increase the realism degree. Among all, the sensorized glove is becoming one of the more interesting and promising of these interfaces. Here we propose the electronic interface and signal conditioning circuitry we adopt as the most suitable for our developed data glove system. The same solution we adopted can be usefully extended for other specific systems that treat signals coming from sensors which read kinematics from disabled persons with reduced Range Of Motion (ROM) capabilities.

The Squarax spatial power combiner

A broad-band transmission line spatial power combiner (SPC) is proposed in this paper, which uses a square coaxial (Squarax) transmission line (TL). This structure has some advantages over the traditional circular coaxial spatial power combiner, which have been described in this paper. Fin-Line to microstrip transitions are inserted into the Squarax TL, in order to allow an easy integration of Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifler (SSPA). The Squarax SPC geometry allows the feeding of a higher number of MMIC than in a Waveguide SPC, so that this structure ensures high power outputs and small sizes, together with theoretical DC frequency cut-ofi. In this work, the design and simulation of a passive 4{18GHz Squarax SPC are reported.

Non Uniform Geometry Bend Sensors Exploited for Biomedical Systems.

In biomedical systems the bend sensors have been increasingly used stands their interesting properties useful to measure human joint static and dynamic postures. These commercially available sensors are usually made of a polyester film printed on with a special carbon ink. The film acts as a support while the ink’s resistance value changes with bending dues to an applied external force. The substrate film material is usually made by Kapton and/or Mylar for their properties, stands the fact that substrate must be able to bend repeatedly without failure for the sensor to work. In spite of their interesting properties the commercial bend sensors have a resistance vs. bent angle characteristic which is not actually ideal as a linear function, to measure human postures, would be. So we introduce here a novel solution useful to linearize the sensor response.