Modeling and simulation of sensor orientation errors in garments

We report in this paper on a novel modeling and simulation approach to predict orientation errors of garment-attached sensors and their effect on posture classification. Such errors occur frequently in smart garment implementations and can reduce sensor information quality for movement and posture recognition. A kinematic model of the human upper-body was developed to simulate upper limb postures and the output of virtual 3D acceleration sensors. The model was enhanced with a statistical approximation of garment-related orientation errors. We derived this model from acceleration sensor deviations between skin- and garment-attached units. The feasibility of our body model and the garment-attached sensor deviation was validated in experimental data. We compared the classification performance for ten posture types that are frequently used in shoulder rehabilitation. In a validation set of 7 participants we observed similar classifier confusions and a relative error of 2.6% (SD:±3.2%) between simulation and experiment. We utilized the model to estimate classification performance for further simulated textile error distributions. Our simulations showed that classification performance depends on low deviations of an acceleration sensor at the lower arm, while a sensor at the upper arm was less critical. Moreover, we included magnetic field sensors in our simulation. With the help of this additional modality our posture classification performance increased by 18%. We conclude that simulation of skin- and garment-attached sensors is a feasible approach to expedite design and development process of smart garments.

[1]  Mark W. Spong,et al.  Robot dynamics and control , 1989 .

[2]  D. De Rossi,et al.  Wearable kinesthetic systems for capturing and classifying body posture and gesture , 2005, 2005 IEEE Engineering in Medicine and Biology 27th Annual Conference.

[3]  Gerhard Tröster,et al.  SMASH: a distributed sensing and processing garment for the classification of upper body postures , 2008, BODYNETS.

[4]  C Kirtley,et al.  Calculation of multi-segment rigid body joint dynamics using MATLAB , 1997, Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine.

[5]  O. Amft,et al.  Influence of a loose-fitting sensing garment on posture recognition in rehabilitation , 2008, 2008 IEEE Biomedical Circuits and Systems Conference.

[6]  J. Denavit,et al.  A kinematic notation for lower pair mechanisms based on matrices , 1955 .

[7]  Henry Dreyfuss,et al.  Measure of Man and Woman: Human Factors in Design , 1993 .

[8]  Steve Mann,et al.  Smart clothing: the shift to wearable computing , 1996, CACM.

[9]  Peter I. Corke,et al.  A robotics toolbox for MATLAB , 1996, IEEE Robotics Autom. Mag..

[10]  Michael Eisenberg,et al.  Fabric PCBs, electronic sequins, and socket buttons: techniques for e-textile craft , 2009, Personal and Ubiquitous Computing.

[11]  Paul Lukowicz,et al.  Dealing with sensor displacement in motion-based onbody activity recognition systems , 2008, UbiComp.

[12]  D.L. Hill,et al.  Smart Garment to Help Children Improve Posture , 2006, 2006 International Conference of the IEEE Engineering in Medicine and Biology Society.

[13]  Theodoros N. Arvanitis,et al.  Assessing the Wearability of Wearable Computers , 2006, 2006 10th IEEE International Symposium on Wearable Computers.

[14]  Paul Lukowicz,et al.  PadNET: wearable physical activity detection network , 2003, Seventh IEEE International Symposium on Wearable Computers, 2003. Proceedings..

[15]  Richard Martin,et al.  Design for wearability , 1998, Digest of Papers. Second International Symposium on Wearable Computers (Cat. No.98EX215).

[16]  Mark T. Jones,et al.  E-textile based automatic activity diary for medical annotation and analysis , 2006, International Workshop on Wearable and Implantable Body Sensor Networks (BSN'06).

[17]  Gerhard Tröster,et al.  Recognizing Upper Body Postures using Textile Strain Sensors , 2007, 2007 11th IEEE International Symposium on Wearable Computers.

[18]  Albrecht Schmidt,et al.  Multi-sensor context aware clothing , 2002, Proceedings. Sixth International Symposium on Wearable Computers,.