On the development of an implantable - biomechatronic system for - - PowerPoint PPT Presentation

On the development of an implantable - biomechatronic system for the rehabilitation

• f lower limb neuro-muscular disabilities.

V.N. Syrimpeisa, L.L. Chioua, V.C. Moulianitisa, N.A. Aspragathosa, E.C Panagiotopoulosb a Department of Mechanical Engineering and Aeronautics, University of Patras b General University Hospital of Patras, Orthopedics Department

Outline

• Introduction
• Comparative comments on FES systems
• -Biomechatronics design approach
• The proposed rehabilitation system
• Simulation results
• Conclusions

Introduction

• The lower limp disabilities caused by spinal cord injuries, stroke or

head injuries, where the muscles are intact can be rehabilitated using Functional Electrical Stimulation (FES).

• Liberson et al. [1] proposed the application of electrical stimulation to

the common peroneal nerve to correct the Drop-Foot Syndrome, which is the inability of the patient to dorsiflex (raise) his foot.

• Design of a wireless -biomechatronics system for the rehabilitation
• f the lower limbs disabilities. Implantable microsensors and

microstimulators are considered.

• The proposed control laws are based on computational intelligent

techniques based on fuzzy logic and neural networks.

• The computational requirements are minimized resulting to the

miniaturization of the controller.

Funtional Electrical Stimulation (FES) classification

• External systems that are non-invasive and all

components are outside the body.

• Percutaneous systems where the stimulator and

controller are outside the body, while stimulating electrodes are inside the body.

• Implanted systems where the stimulator and

electrodes are inside the body and the controller is

• utside.

Comparative comments on FES systems

Any muscle No need Very convenient Disappeared No enough data surgical Implanted Difficult (deep muscle) Less frequent acceptable Entry skin infection Periodic electrodes replacement Percuta- neous Difficult (deep muscle) frequent Unacceptabl e Skin irritation Easy but daily External Muscle selectivity Calibration Aesthetics & Comfort Tissue Reaction Application FES category

New trends in FES

• The comfort of the patient is a crucial requirement for a

successful design of FES systems.

• The reduction of the size facilitates the implantation,

improves the comfort of the patient and possibly the surgical incision.

• If some components of the system cannot be implanted

then the communication among them should be wireless.

• Today, almost all biomedical implantable

microelectronics are wireless to reduce the risk of infection as well as to increase patients comfort and robustness of the implanted device.

• Biomechatronics design

approach

• Mechatronics is a synergetic interdisciplinary

approach to the design of products and systems. In this case, biomedical sciences with engineering and a new kind of integration emerges called Biomechatronics

• Design a control system for rehabilitation:

synergy of experts from different disciplines such as microengineering and medicine is necessary towards -Biomechatronics leading in new trends in research and development.

The proposed rehabilitation system

Micro-sensors

• Micro-sensors are used to detect kinematic and dynamic

information such as muscle force during the gait cycle.

• The force measurement is based on light intensity

modulation when the fiber (diameter of 0.5 mm) is compressed inside the tendon.

• Stainless steel needle electrodes are used for the EMG,

with a length between 25 mm to 75 mm and a diameter between 0.36 mm to 0.45 mm.

• The implantable microsensor named “Biomechatronic

Position Transducer” (BPT) is able to extract kinematic information by monitoring the sliding movements of some tendons.

Micro-stimulators

• Micro-stimulators are used to stimulate specific nerves, that

stimulate muscles or to stimulate directly the selected muscles.

• BiONs™ consist of a ceramic and titanium cylinder capped

at each end with platinum anode and cathode. The cylinder is 15.6 mm in length and 2.5 mm in diameter.

• Cuff electrodes are conformal to the natural shape of the

nerve and it is possible to have many contacts for multi- channel stimulation.

• The cuff is manufactured from biocompatible materials

such as medical grade silicon rubber and platinum or iridium oxide contacts. Typical cuff diameters vary from 1 to 6 mm with wrap thickness under 40 m.

BiONS implanted to Tibialis Anterior and Extensor Digitorum Longus muscles

Intelligent Controller for drop-foot syndrome rehabilitation

• Intelligent neuro-fuzzy controller adaptable to the patient

and to usual walking modes (normal slope, ascending and descending stairs).

• Knowledge based, model free controller. Learning

adjusts the parameters of the fuzzy controller.

• Optimization of the computational requirements towards

minimizing the size of the controller.

• Stepper exercise is simulated for preliminary tests on the

controller performance.

The intelligent controller

Simulation results: Tibialis Anterior (TA)

Force vs. stepper cycle

1 2 3 4 5 6 7 8 9 10

• 50

50 100 150 200 250 Stepper Cycle Force (N) Tibialis Anterior control error fuzzy error learning error

Simulation Results:Extensor Digitorum Longus (EDL)

Force vs. stepper cycle

1 2 3 4 5 6 7 8 9 10

• 20

20 40 60 80 100 120 140 160 Stepper Cycle Force (N) Extensor Digitorum Longus control error fuzzy error learning error

Conclusions

• The design of a rehabilitation system using a -biomechatronics

approach is presented.

• The preliminary simulation results of the controller performance are

encouraging.

• The benefits of this system can be summarized in the following:

Decreased size offering more comfort to the patient. Increased flexibility of the system since it can work with multiple muscles of lower limbs. Increased adaptability since the control laws can be adapted to the patient and walking mode.

• Interdisciplinary research work is necessary for further decreasing

the components size using micro-fabrication techniques to facilitate the implantation with the appropriate biocompatible materials.

Thank you for your attention!