Browsing by Subject "Accelerometers"

Now showing 1 - 10 of 10

Open Access
Activity recognition invariant to sensor orientation with wearable motion sensors
(MDPI AG, 2017) Yurtman, A.; Barshan, B.
Most activity recognition studies that employ wearable sensors assume that the sensors are attached at pre-determined positions and orientations that do not change over time. Since this is not the case in practice, it is of interest to develop wearable systems that operate invariantly to sensor position and orientation. We focus on invariance to sensor orientation and develop two alternative transformations to remove the effect of absolute sensor orientation from the raw sensor data. We test the proposed methodology in activity recognition with four state-of-the-art classifiers using five publicly available datasets containing various types of human activities acquired by different sensor configurations. While the ordinary activity recognition system cannot handle incorrectly oriented sensors, the proposed transformations allow the sensors to be worn at any orientation at a given position on the body, and achieve nearly the same activity recognition performance as the ordinary system for which the sensor units are not rotatable. The proposed techniques can be applied to existing wearable systems without much effort, by simply transforming the time-domain sensor data at the pre-processing stage. © 2017 by the authors. Licensee MDPI, Basel, Switzerland.
Open Access
Breathing detection based on the topological features of IR sensor and accelerometer signals
(IEEE, 2017) Erden, Fatih; Çetin, A. Enis
This paper describes a non-contact breathing detection system using a pyro-electric infrared (PIR) sensor and an accelerometer. The multi-sensor system can be used to detect the respiratory disorders. A PIR sensor is placed onto a stand near a bed and an accelerometer is placed on the mattress. We recently developed a PIR sensor which is capable of producing 1-D time-varying signals corresponding to the motions in its field of view. The PIR sensor signal due to the thoracic movements turns out to be an almost periodic signal. Similarly, the accelerometer produces an almost periodic signal in response to vibrations in bed. Sensor signals are processed using a topological approach. Point clouds are constructed from the delay-coordinate embedding of the time series sensor data first. Then, periodic structures in the point clouds are detected using persistent homology. The sensors, with the proposed method, complement each other to produce more accurate decisions in different lying positions.
Open Access
Düşme tespiti için sınıflandırma yöntemlerinin karşılaştırılması
(IEEE, 2014-04) Çatalbaş, Bahadır; Yücesoy, Burak; Seçer, G.; Aslan, Murat
Bu bildiride giyilebilir yapıda olan ve üç boyutlu ölçüm alabilen bir ivmeölçerin çıktılarını kullanarak düşme tespiti yapan farklı algoritmaların karşılaştırılması yapılmıştır. Karşılaştırma amacıyla destek vektör makineleri, yapay sinir ağları ile elde edilen sınıflandırıcılar ve kural bazlı bir sınıflandırıcı kullanılmıştır. Sınıflandırıcıların tasarlanması ve dogrulanması amacıyla 7 farklı denekten üçer defa düşme ve düşme dışındaki günlük aktivitelere ilişkin ivmeölçer verileri toplanmıştır. Yapılan karşılaştırma sonucunda tespit doğruluğu en yüksek algoritmanın %87,76 ile destek vektör makineleri olduğu bulunmuştur. En yüksek düşme tespit oranı da %90,91 ˘ olarak kural bazlı sınıflandırıcı kullanımıyla elde edilmiştir. En yüksek özgüllük oranı %89,47 ile yine destek vektör makineleri ile elde edilmiştir.
Open Access
Evaluation of solid-state gyroscope for robotics applications
(Institute of Electrical and Electronics Engineers, 1995-02) Barshan, B.; Durrant-Whyte, H. F.
he evaluation of a low-cost solid-state gyroscope for robotics applications is described. An error model for the sensor is generated and included in a Kalman filter for estimating the orientation of a moving robot vehicle. Orientation eshation with the error model is compared to the performance when the error model is excluded from the system. The results demonstrate that without error compensation, the error in localization is between 5-15"/min but can be improved at least by a factor of 5 if an adequate error model is supplied. Like all inertial systems, the platform requires additional information from some absolute position-sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modeling of error sources, inertial sensors can provide valuable orientation information for mobile robot applications.
Open Access
Improved deterministic measurement model for consumer-grade accelerometers
(Institution of Engineering and Technology, 2016) Barshan, B.; Seçer, G.
Deterministic error modelling, calibration and model parameter estimation of consumer-grade accelerometers is considered and improvement to the traditionally used measurement model is proposed. Calibration experiments on a flight motion simulator are performed for experimental verification. Model parameters are estimated using the Levenberg-Marquardt optimisation algorithm. Residual errors are considerably reduced as a result of the improved measurement model.
Open Access
Inertial navigation systems for mobile robots
(Institute of Electrical and Electronics Engineers, 1995-06) Barshan, B.; Durrant-Whyte, H. F.
A low-cost solid-state inertial navigation system (INS) for mobile robotics applications is described. Error models for the inertial sensors are generated and included in an Extended Kalman Filter (EKF) for estimating the position and orientation of a moving robot vehicle. Two Merent solid-state gyroscopes have been evaluated for estimating the orientation of the robot. Performance of the gyroscopes with error models is compared to the performance when the error models are excluded from the system. The results demonstrate that without error compensation, the error in orientation is between 5-15"/min but can be improved at least by a factor of 5 if an adequate error model is supplied. Siar error models have been developed for each axis of a solid-state triaxial accelerometer and for a conducting-bubble tilt sensor which may also be used as a low-cost accelerometer. Linear position estimation with information from accelerometers and tilt sensors is more susceptible to errors due to the double integration process involved in estimating position. With the system described here, the position drift rate is 1-8 cds, depending on the frequency of acceleration changes. An integrated inertial platform consisting of three gyroscopes, a triaxial accelerometer and two tilt sensors is described. Results from tests of this platform on a large outdoor mobile robot system are described and compared to the results obtained from the robot's own radar-based guidance system. Like all inertial systems, the platform requires additional information from some absolute position-sensing mechanism to overcome long-term drift. However, the results show that with careful and detailed modeling of error sources, low-cost inertial sensing systems can provide valuable orientation and position information particularly for outdoor mobile robot applications.
Open Access
Investigation of sensor placement for accurate fall detection
(Springer, 2017) Ntanasis, P.; Pippa, E.; Özdemir, A. T.; Barshan, Billur; Megalooikonomou, V.
Fall detection is typically based on temporal and spectral analysis of multi-dimensional signals acquired from wearable sensors such as tri-axial accelerometers and gyroscopes which are attached at several parts of the human body. Our aim is to investigate the location where such wearable sensors should be placed in order to optimize the discrimination of falls from other Activities of Daily Living (ADLs). To this end, we perform feature extraction and classification based on data acquired from a single sensor unit placed on a specific body part each time. The investigated sensor locations include the head, chest, waist, wrist, thigh and ankle. Evaluation of several classification algorithms reveals the waist and the thigh as the optimal locations.
Open Access
Leg motion classification with artificial neural networks using wavelet-based features of gyroscope signals
(2011) Ayrulu-Erdem, B.; Barshan, B.
We extract the informative features of gyroscope signals using the discrete wavelet transform (DWT) decomposition and provide them as input to multi-layer feed-forward artificial neural networks (ANNs) for leg motion classification. Since the DWT is based on correlating the analyzed signal with a prototype wavelet function, selection of the wavelet type can influence the performance of wavelet-based applications significantly. We also investigate the effect of selecting different wavelet families on classification accuracy and ANN complexity and provide a comparison between them. The maximum classification accuracy of 97.7% is achieved with the Daubechies wavelet of order 16 and the reverse bi-orthogonal (RBO) wavelet of order 3.1, both with similar ANN complexity. However, the RBO 3.1 wavelet is preferable because of its lower computational complexity in the DWT decomposition and reconstruction. © 2011 by the authors; licensee MDPI, Basel, Switzerland.
Open Access
Minyatür eylemsizlik duyucuları ve manyetometre sinyallerinin işlenmesiyle insan aktivitelerinin sınıflandırılması
(IEEE, 2011-04) Yüksek, Murat Cihan; Barshan, Billur
Bu çalışmada insan vücuduna yerleştirilen minyatür eylemsizlik duyucuları ve manyetometreler kullanılarak çeşitli aktiviteler örüntü tanıma yöntemleriyle ayırdedilmiş ve karşılaştırmalı bir çalışmanın sonuçları sunulmuştur. Ayırdetme işlemi için basit Bayeşçi (BB) yöntem, yapay sinir ağları (YSA), benzeşmezlik tabanlı sınıflandırıcı (BTS), ceşitli karar ağacı (KA) yöntemleri, Gauss karışım modeli (GKM) ve destek vektör makinaları (DVM) kullanılmıştır. Aktiviteler gövdeye, kollara ve bacaklara takılan beş duyucu ünitesinden gelen verilerin işlenmesiyle ayırdedilmiştir. Her ünite, her biri üç-eksenli olmak üzere birer ivmeölçer, dönüölçer ve manyetometre içermektedir. Çalışmanın sonuçlarına göre, en iyi ilk üç başarı oranı sırasıyla GKM (%99.12), YSA (%99.09) ve DVM (%98.90) yöntemleri ile elde edilmiştir.
Open Access
Recognizing daily and sports activities in two open source machine learning environments using body-worn sensor units
(Oxford University Press, 2014-11) Barshan, B.; Yüksek, M. C.
This study provides a comparative assessment on the different techniques of classifying human activities performed while wearing inertial and magnetic sensor units on the chest, arms and legs. The gyroscope, accelerometer and the magnetometer in each unit are tri-axial. Naive Bayesian classifier, artificial neural networks (ANNs), dissimilarity-based classifier, three types of decision trees, Gaussian mixture models (GMMs) and support vector machines (SVMs) are considered. A feature set extracted from the raw sensor data using principal component analysis is used for classification. Three different cross-validation techniques are employed to validate the classifiers. A performance comparison of the classifiers is provided in terms of their correct differentiation rates, confusion matrices and computational cost. The highest correct differentiation rates are achieved with ANNs (99.2%), SVMs (99.2%) and a GMM (99.1%). GMMs may be preferable because of their lower computational requirements. Regarding the position of sensor units on the body, those worn on the legs are the most informative. Comparing the different sensor modalities indicates that if only a single sensor type is used, the highest classification rates are achieved with magnetometers, followed by accelerometers and gyroscopes. The study also provides a comparison between two commonly used open source machine learning environments (WEKA and PRTools) in terms of their functionality, manageability, classifier performance and execution times. © 2013 © The British Computer Society 2013. All rights reserved.