Use of Hybrid System Modeling Technique for Robot-Assisted Rehabilitation Systems

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Use of Hybrid System Modeling Technique for
Robot-Assisted Rehabilitation Systems

• Duygun Erol

Yeditepe University Electrical Electronics
Engineering Department Istanbul, TURKEY
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Motivation

• Stroke is a highly prevalent condition,
  especially among the elderly, that results in
  high costs to the individual and the society
• Every year, a large number of people have a
  stroke in all over the world

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Motivation

• Stroke rehabilitation points towards the intense
  and repetitive movement assisted therapy that has
  shown significant beneficial impact on a large
  segment of the patients
• The availability of such training techniques,
  however, are limited by
• the amount of costly therapists time they
  involve
• the ability of the therapist to provide
  controlled, quantifiable and repeatable
  assistance
• Robot-assisted rehabilitation that can
• provide quantifiable and repeatable assistance
  that ensure consistency during the rehabilitation
  
• likely to be cost-efficient

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Robot-Assisted Rehabilitation Systems
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Limitations

• Two important issues that the current
  robot-assisted rehabilitation systems do not
  address
• First, they are limited by their inability to
  simultaneously assist both arm and hand movements
• Second, none of these robot-assisted
  rehabilitation systems can comprehensively alter
  the task parameters based on patients feedback
  to impart effective therapy during the execution
  of the task in an automated manner

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Scope of the Research

• The objective of this work is to develop an
  intelligent control architecture for
  robot-assisted rehabilitation systems that can
  provide assistance to both the arm and hand in a
  coordinated manner to allow stroke patients to
  undergo task-oriented active training therapy
• Additionally a human intention recognition
  system is augmented inside the control
  architecture to dynamically modify the
  rehabilitation task based on the patients verbal
  feedback

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Intelligent Control Architecture

• Hybrid system theory provides mathematical tools
  that accommodate both continous and discrete
  system in a unified manner
• Hybrid system model provides flexible and
  extendible environment
• Hybrid system allows analysis of properties such
  as stability, reachability
• Advantage of using hybrid system model is taken
  to model the robot-assisted rehabilitation system

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Intelligent Control Architecture
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Intelligent Control Architecture
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Intelligent Control Architecture
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Intelligent Control Architecture
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Intelligent Control Architecture
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Intelligent Control Architecture
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PLANT Rehabilitation Robotic System
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PLANT (cont)Rehabilitation Robotic System
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PLANT (cont)Rehabilitation Robotic System
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PLANT (cont)Rehabilitation Robotic System
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PLANT (cont)Human Intention Recognition
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Task Design(Drinking from a Bottle)
i) reach towards the bottle while opening the
hand, ii) reach the bottle, iii) close the hand
to grasp the bottle, iv) move the bottle towards
the mouth, v) drink from a bottle using a straw,
vi) place the bottle back on the table, vii) open
the hand to leave the bottle back on the table
and viii) go back to starting position
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Design Details of theIntelligent Controller
(Theory)

• The discrete event system (DES) plant model
  (plant and interface) is a nondeterministic
  finite automaton

• The DES controller (high-level controller) is
  modeled as a discrete-event system (DES)
  deterministic finite automaton

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Design Details of the Intelligent Controller

• Each region in the state space of the plant
  bounded by the hypersurface is associated with a
  state of the DES plant as

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Design Details of the Intelligent Controller
(cont)

• The plant symbols

in
are found using
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Design Details of the Intelligent Controller
(cont)

• The control states

in
are found using
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Design Details of the Intelligent Controller
(cont)

• The control symbols

in
are found using
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Design Details of the Intelligent Controller
(cont)
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Experiments

• First the validation of the human intention
  recognition system is summarized
• Then the results of the experiments to
  demonstrate the efficacy of the proposed control
  architecture are provided
• The Matlab/Simulink/Stateflow software is used
  to implement the proposed high-level controller

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Results (Validation of Human Intention
Recognition System)
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Results(Evaluation of the Proposed Intelligent
Control Architecture )
Desired Motion Trajectory
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Control Mechanism
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Results (cont)
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Desired Trajectory for the DFB task when an
Unplanned Event Happened
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Results (cont)
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Subjects Actual Trajectories and Hand
Configuration of the Subject for the Experiment
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Discussions and Conclusion

• A new intelligent control architecture is
  designed that can
• supervise the arm and the hand assistive devices
  to produce necessary coordinated motion to
  complete a given ADL task,
• monitor the progress and the safety of the ADL
  task such that necessary dynamic modifications of
  the task execution can be made (if needed) to
  complete the given task in a safe manner,
• incorporate patients feedback in order to make
  the necessary modifications to impart effective
  therapy during the execution of the task in an
  automated manner

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Discussions and Conclusion (cont)

• The proposed intelligent control architecture
  exploits hybrid system modeling techniques to
  accommodate both continuous and discrete systems
  in a unified manner
• Hybrid system modeling technique is particularly
  useful in this context since it allows a
  systematic interface between the low-level
  assistive controllers and the high-level
  decision-making controller
• The hybrid system modeling technique provides
  flexibility in interfacing low-level controllers
  without extensive redesign cost

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Discussions and Conclusion (cont)

• Hybrid system modelling is mathematically
  rigorous and provides systematic design tools
  that are not limited by the number of states or
  events
• New safety features as well as new task
  requirements can be incrementally added to the
  system by designing new events either by adding
  new sensors or by further analyzing the current
  sensory information and by adding new decision
  rules in the high-level controller
• The patients feedback is easily integrated
  inside the proposed intelligent control
  architecture

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Contributions of Hybrid System Modelling
Techniques to Rehabilitation Robotics

• The proposed hybrid system based control
  architecture provides a systematic procedure to
  effect changes such that the task execution could
  be automated
• Instead of preprogramming numerous static trees
  based on if-then-else rules, it provides a
  dynamic mechanism of generating events that leads
  to necessary high-level decisions
• A hybrid system based control mechanism could be
  useful in rehabilitation context in terms of
  coordinating decision making and assisting,
  monitoring safety, and managing and modifying
  code for automation
• To our knowledge, such a hybrid system based
  control mechanism has not been explored in
  rehabilitation robotics

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Future Work

• Demonstrate the efficacy of the proposed
  intelligent control architecture with the stroke
  patients
• Search for other hybrid system modelling
  techniques to develop a global control
  architecture
• The efficient ways of human intention recognition
  systems are planned to be investigated that can
  recognize unclear words for stroke survivors who
  have aphasia

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THANK YOU
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