A Hierarchical Approach to Recognize Purposeful Movements Using Inertial Sensors: Preliminary Experiments and Results
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Carme Zambrana1, Sebastian Idelsohn-Zielonka1, Mireia Claramunt-Molet1, Maria Almenara-Masbernat2, Eloy Opisso2, Josep Maria Tormos2,Felip Miralles1 and Eloisa Vargiu1
1 2
A Hierarchical Approach to Recognize Purposeful Movements Using Inertial Sensors:Preliminary Experiments and Results
CONTEXT
POST STROKE REHABILITATION
Stroke Acute careOutpatient
rehabilitation
Inpatient
rehabilitation
24-48h 2-8 weeks > 2 months0
ADALT
METHOD
Hierarchical Approach
Preprocessing (SMV)
Threshold
Tartaglia’s filter
𝑆𝑀𝑉 = 𝐴𝑐𝑐𝑥2 + 𝐴𝑐𝑐𝑦
2 + 𝐴𝑐𝑐𝑧2
Experimentally calculated
Module 1 (M1)
(𝜃)
INPUT
MODEL
OUTPUT
𝑣𝑖 = 𝑞=−2(≠0)
2
𝑙𝑖+𝑞𝑓𝑞
𝑣𝑖 > 𝑣𝑚𝑎𝑥𝑣𝑖 ≤ 𝑣𝑚𝑎𝑥
: Movement: Non-Movement
𝑣𝑚𝑎𝑥 = 𝑞=−2(≠0)
2
1 𝑓𝑞 = 8
Supervised binary classifier
Experimentally selected
Module 2 (M2)
INPUT
OUTPUT
MODEL
PRELIMINARY EXPERIMENTS AND RESULTS
Setting up
Devices• 2 IMUs (one on each wrist)• 3-axial accelerometers• 20 Hz• Bluetooth 2.0
Volunteers• 9 healthy volunteers
• 31.22 ± 4.59 years• 5 female / 4 male• 1 left-handed
Activities• Purposeful
• Non-purposeful
Results
Module 1
Preprocessing (SMV)
Threshold
Tartaglia’s filter
𝐴𝑐𝑐 =𝑇𝑃 + 𝑇𝑁
𝑇𝑃 + 𝑇𝑁 + 𝐹𝑁 + 𝐹𝑃
Grid-search over the range 0 to 1 by 0.005, maximizing the accuracy function.
(𝜃)
Module 2
Supervised binary classifier
Features:• Time domain• Frequency domain
Models:• K-Nearest Neighbor (KNN)• Random Forest (RF)• Support Vector Machine (SVM)
Windows Lengths:• 2.0 seconds• 4.0 seconds
Randomly Split 70-30% Train-Test10-fold cross validation
𝐹1 = 2𝑇𝑃
2𝑇𝑃 + 𝐹𝑁 + 𝐹𝑃
Results
Overall results
Purposeful Other
87.46%
92.38%7.62%
12.54%
Purp
osefu
lO
ther
Predicted
Tru
e
How it works
Non-movement
Movement
M1 output
Non-purposeful
Purposeful
M2 output
Eating Pouring
waterDrinking Brushing
their teethFolding a towel
Walking
FINAL REMARKS AND FUTURE WORK
Final remarks and future work
Future work:• Test the Hierarchical Approach with post-stroke patients• Create new modules to recognize other non-purposeful movements
Final remarks• We have developed a hierarchical approach to recognize purposeful movements• Tested with 9 healthy volunteers, obtaining encouraging results: Acc = 0.90701
THANK YOU
Contact:Carme Zambranacarme.zambrana@eurecat.org
Acknowledgments: The study has been partially funded by ACCIÓ(Pla d’Actuació de Centres Tecnològics 2016)
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