5. Understanding Drop Foot
2. Inability to avoid foot slap during
controlled plantarflexion
3. Plantarflexors’ weakness might
occur during powered plantarflexion.
Source: McMahon, Muscles, Reflexes and Locomotion (1984)
1. Inability to clear the toe during swing
phase
5
6. Market Solutions for Drop Foot
Existing
Solutions
Beechfield
Healthcare
Richie
1. Mostly passive
2. Uncomfortable
3. Assymetric walking
4. Active solutions not
patient-specific
Odstock DFS
6
7. Objective
Develop an Active Assistive Device to restore gait
and promote movement rehabilitation of the
ankle-foot complex in individuals with Drop Foot
(DF), using Functional Electrical Stimulation (FES).
Gait cycle in a healthy individual
7
8. Introduction: The FES pulse
Use of electrical currents
delivered to the muscles
Artificial activation of
paralyzed muscles
Promotes desired foot
movements
6
9. Technical Objectives
Develop a FES actuator to promote functional human
movement1.
Develop a FES Assistive Platform to rapidly prototype
different correction strategies for DF2.
Model the dynamics of the electrically stimulated leg
muscles affected by DF3.
9
10. Technical Objectives
Develop a FES actuator to promote functional human
movement1.
Develop a FES Assistive Platform to rapidly prototype
different correction strategies for DF2.
Model the dynamics of the electrically stimulated leg
muscles affected by DF3.
10
11. PULSE
AMPLITUDE
BIPHASIC PULSE MODULAR
PULSE WIDTH PULSE
FREQUENCY
BATTERY
POWERED
LIGHT WEIGHT
PORTABLE INTERFACE
FES PULSE PARAMETERS (FULLY CUSTOMIZABLE)
The ISTIM Modular Stimulation System
Modular Stimulation Unit
(MSU)
Control
Module
The FES Actuator
UP TO 100 mA UP TO 500 µs UP TO 200 Hz
USB & TTL Serial
28.7g
GENERAL SPECIFICATIONS
11
12. The FES Actuator
Safety & Quality
benchmark
Promotes functional
movements in large
and small muscles
12
14. Technical Objectives
Develop a FES actuator to promote functional human
movement1.
Develop a FES Assistive Platform to rapidly prototype
different correction strategies for DF2.
Model the dynamics of the electrically stimulated leg
muscles affected by DF3.
14
15. The FES Assistive Platform
MODULAR
SENSORS
ACTUATORS (STIMULATION CHANNELS)
GENERAL SPECIFICATIONS
WIRELESS BATTERY
POWERED
9-AXIS INERTIAL 3-AXIS ACCEL
(EMBEDDED)
FORCE SENSING
MSU
(NATIVE)
MSU EXPANSION PORT
15
16. Platform Walking Trials
Gait Analysis Trials (Full Setup)
System able to capture the ankle angle
and foot-ground interactions (force)
16
17. Platform Walking Trials II
In both DF correction strategies:
Stimulation was correctly delivered
3 walking phases detectedForce Sensors
2 walking phases detectedInertial Sensors
DF correction trials
17
18. Technical Objectives
Develop a FES actuator to promote functional human
movement1.
Develop a FES Assistive Platform to rapidly prototype
different correction strategies for DF2.
Model the dynamics of the electrically stimulated leg
muscles affected by DF3.
18
20. Modeling the stimulated muscle
P. L. Melo, M. T. Silva, J. M. Martins, D. J. Newman, A
Model-based Approach To Correct Drop Foot Using
Electrical Stimulation, Control Eng Pract, 2014
(submitted, under review).
Ass.
Salvador
Award 2011
Best oral pres. and poster award
2012 Conference
► Understanding the electrically stimulated dorsiflexors behavior is crucial for
the development of advanced closed loop control strategies to correct DF;
► A two-stage empirical methodology is proposed to model the dynamics of
the ankle-foot complex under electrical stimulation;
► A black-box modeling approach and a wide variety of excitation signals were
used to estimate and validate linear models of the referred dynamics;
20
21. A modular muscle stimulation system
Experimentally validated and tested, able to perform real-time
controlled forceful muscle contractions.
Contributions
A FES neuroprosthesis platform
Experimentally validated and tested, allowing the rapid prototyping
of multiple control strategies for DF, and eventually to other motor
disabilities.
A process to model muscle dynamics using FES
The first study performed to model the electrically stimulated
dorsiflexors that allows for patient-specific FES models in:
- compensatory devices (daily use);
- rehabilitation (physical therapy);
21
22. Future research directions
► Implement model-based and patient-specific FES neuroprostheses, using methodologies such as the
one developed in this work;
► Clinically validate the developed methodologies both as a randomized controlled trial and at the
same time optimize the process (time wise) so it becomes clinically viable;
► Explore and model the dynamics of sFES under co-contraction as a way to model the joint’s
mechanical impedance (as suggested by N. Hogan, 1984), specifically:
► Co-contraction of the plantarflexors and dorsiflexors;
► Additional control of the ankle by controlling the foot’s invertors and eversors;
► Introduce muscle fatigue models in FES neuroprostheses: explore the redundancy of different
muscles over specific joints and develop a network of different stimulation channels. Implantable
stimulators (BIONs) will likely provide better selectivity and therefore efficiency in this matter.
22
23. Journal Publications
P. L. Melo, M. T. Silva, J. M. Martins, D. J. Newman, Identification of Muscle Dynamics For Functional Electrical Stimulation Control
Applications, J Biomech, 45, S1, p. S72, 2012.
P. L. Melo, M. T. Silva, J. M. Martins, D. J. Newman, Technical Developments of Functional Electrical Stimulation to Correct Drop Foot:
Sensing, Actuation and Control Strategies, Clin Biomech, 2014 (Accepted).
P. L. Melo, M. T. Silva, J. M. Martins, D. J. Newman, A Microcontroller Platform For The Rapid Prototyping of FES-based Gait
Neuroprostheses, Artif Organs, 2014 (Accepted)
P. L. Melo, M. T. Silva, J. M. Martins, D. J. Newman, A Model-based Approach To Correct Drop Foot Using Electrical Stimulation, Control
Eng Pract, 2014 (accepted, with revisions).
P. L. Melo, M. T. Silva, J. M. Martins, A. M. Pinto, D. J. Newman, Modular Stimulation Units: A Novel Stimulation Platform for Motor
Rehabilitation, Artif Organs, 2014 (submitted, under review).
F. Romero, P. L. Melo, M. T. Silva, F. Javier Alonso, Estimation of FES actuation parameters based on inverse dynamic analysis, J Bionic
Eng, 2014 (submitted, under review).
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