Pablo Rogeli

A Digital Goniometer based on encoders for measuring knee-joint position in an orthosis

Angular measurements of knee joint are a key factor in orthoses design, actually is very important for human gait analysis in order to obtain a deep knowledge of the musculoskeletal system performance. Video-based motion analysis systems have been used as measurement tools to quantify the angle and movement of knee joint. Though this technique is good, it requires special equipment and high computational cost. This work introduces a novel method of knee joint measurement. The design is mainly based on the contactless magnetic absolute encoder AS5040 (Austria Microsystems®, USA), and the microprocessor type PIC16F877A. The developed device has a resolution of 0.35 degrees, quite enough for an orthosis that requires knee position measurements. The reliability of the system was evaluated by making: 1) Static measurements by using a mechanical goniometer as reference, in which a correlation up to 0.999 was obtained. 2) Dynamical measurements by performing flexion-extension movements by a healthy subject and comparing the records with a commercial motion analysis system (APAS®, USA). A correlation of 0.9943 was obtained. Besides, trials were performed by three subjects under natural gait.

A pressure distribution measurement system for supporting areas of wheelchair users

Pressure ulcers are skin injuries caused by long term exposition to high pressures on support points that interrupt blood circulation reducing the transport of oxygen and nutrients to the cells. They mainly affect people with poor mobility that stay in seating position for long periods of time. In spite of the diversity of commercial prototypes of cushions, ulcers caused by pressure are still a problem for wheelchair users. This work describes the design of a measurement system of pressure distribution in sedentary position. The aim of the system is to record the pressure concentration in order to obtain specific information about the supporting areas, and with these data used as feedback, eventually to determine an efficient random stimulation sequence to provide, in the future, a system to prevent these referred injuries. The proposed system consists of a 12 air-cell division cushion. Each cell has a pressure sensor and an input for electro valves to inflate and deflate. The recording and control of the valves is carried out through a graphical interface designed in LabVIEW®. A calibration procedure for the designed cushion was made by comparing the greatest load values pressure with a commercial platform, similar results were obtained.

An alternating pressure sequence proposal for an air-cell cushion for preventing pressure ulcers

The distribution and release of pressure on ischial regions are two important parameters for evaluating the effectiveness of a cushion; especially the release of pressure over time on ischial tuberosities, which is significant for preventing pressure ulcers. The aim of this work is to evaluate the effect on interface pressure through the application of a proposed alternating pressure sequence for an air-cell cushion. Six healthy volunteers were asked to sit on the air cell cushion, in static and alternating modes, as well as on a typical foam cushion for 12 minutes. Interface pressure was monitored with a matrix sensor system. Interface pressure values on ischial tuberosities, user contact area and pressure distribution were analyzed. Results showed that IP on IT tends to increase in both foam and static cushions, while in alternating cushion IP on IT tends to decrease. User contact area was significantly larger in alternating cushion than in static or foam cushions. Moreover, there is a better pressure re-distribution with alternating cushion than with the other cushions. The goal of the alternating sequence is to redistribute pressure and stimulate the ischial regions in order to promote blood flow and prevent pressure occurring in wheelchair users.

Evaluation of suitability of a micro-processing unit of motion analysis for upper limb tracking

The aim of this study is to assess the suitability of a micro-processing unit of motion analysis (MPUMA), for monitoring, reproducing, and tracking upper limb movements. The MPUMA is based on an inertial measurement unit, a 16-bit digital signal controller and a customized algorithm. To validate the performance of the system, simultaneous recordings of the angular trajectory were performed with a video-based motion analysis system. A test of the flexo-extension of the shoulder joint during the active elevation in a complete range of 120º of the upper limb was carried out in 10 healthy volunteers. Additional tests were carried out to assess MPUMA performance during upper limb tracking. The first, a 3D motion reconstruction of three movements of the shoulder joint (flexo-extension, abduction-adduction, horizontal internal-external rotation), and the second, an upper limb tracking online during the execution of three movements of the shoulder joint followed by a continuous random movement without any restrictions by using a virtual model and a mechatronic device of the shoulder joint. Experimental results demonstrated that the MPUMA measured joint angles that are close to those from a motion-capture system with orientation RMS errors less than 3º.

Development of an electrical impedance tomograph

This article describes the design of an electrical impedance tomograph (EIT), with the aim to provide a tool to detect morphological changes in tissues. This design consists of an array of 16 electrodes distributed on a ring way. The 4 points technique is used to record the amplitude of the electrical impedance. The array was placed around of a tank filled with a saline solution and objects of different sizes and shapes as test material. The operation of the system is controlled by a program developed on LabVIEW, the impedance data recorded are sent to a MATLAB toolbox called EIDORS to be processing. The final result is a reconstructed image in witch objects larger than 1 cm of contrasting impedance can be recognized.

A System for Simultaneous Finger Joints Goniometric Measurements Based on Inertial Sensors

In this work, a system to record continuously and simultaneously the flexion and extension of finger joints and to compute a range of motion of the hand joints is presented. The system is based on micro-inertial sensors and a graphical interface in LabVIEW with a mathematical algorithm for signal conditioning. Ten sensors were attached to fingers with adjustable velcro belts, eight on proximal and distal phalanges from index to little fingers, one on the proximal phalanx of the thumb and another on the hand dorsum. The evaluation protocol consisted of 3 sessions of 10 repetitions each, on both hands of 6 healthy volunteers where the angular trajectory was recorded during grasping a 7.8 cm diameter sphere. A statistical analysis was performed in order to determine the variation among the measurements. The purpose of this study was to demonstrate the suitability of this system for simultaneous measurements of range of motion during flexion and extension, considering that it can be used interchangeably in the two hands, regardless the size. The results showed that the developed system is suitable for registering objectively the range of motion of the hand.

Design and simulation of an active bilateral orthosis for paraplegics

Most wheelchair users suffer physical, social and psychological health adverse consequences. In order to cope with these problems, orthosis and prosthesis have been developed in order to assist and provide a better quality life for these people. An active bilateral orthosis can support and induce bipedal locomotion for people with lower limb paralysis. The design and simulation of Cinabo, an active bilateral orthosis based on static and kinematic analysis, a finite element analysis (FEA) and a validation in Matlab to achieve a functional structure, is presented in this work. The main goal is to develop a rehabilitation tool to maintain active remnant bio-structures to keep or restore the lower limbs in healthy conditions through basic movement patterns of bipedal gait and posture modifications. According to the results, the physical model of the active bilateral orthosis will provide the functions needed to solve the important problem of health due to collateral lesions caused by immobility.

Development of a multimedia interactive system for virtual heart animation based on phono-electrocardiography for educational purposes

In this work, an interactive system is presented as a friendly approach to science addressed to scholars and people interested in some basics about the heart function. It is based on an animated virtual heart, commanded by the heart electrical activity. The signal is directly recorded from the thorax of the user with a three-electrode set mounted in a support that includes a microphone to capture heart sounds produced by its mechanical activity. The system uses a graphic User interface (GUI) developed to show a heart animation where users may associate the action of their own organ with both the presence of bioelectrical phenomenon of muscle excitation and sounds mainly produced by valves motion. This interactive device was required by a museum of science and schools.