CLIAMS:We claim:
1. A system for controlling hand orthosis using electrooculography, wherein said system comprises of:
- at least one signal acquisition unit (100) having at least one electrode means capable of being positioned on the skin around the eyes to capture the electrooculogram (EOG) voltage signals being generated from the sequences of the movement of eyes of the user,
- at least one signal conditioning unit (200) capable of amplifying and filtering said captured EOG voltage signals,
- at least one signal processing unit (300) having at least one microcontroller unit capable of processing said captured EOG voltage signals for identification of the valid eye movement (301) and classification (302) thereof into sequence of eye movements,
- at least one hand orthosis (400) having at least one servo motor, for controlling hand orthosis corresponding to said processed EOG voltage signals,
wherein said signal processing unit (300) generates control signals corresponding to said processed EOG voltage signals to said servomotor to control the movements of said hand orthosis unit.

2. The system for controlling hand orthosis using electrooculography as claimed in claim 1, wherein said electrode means comprising of at least three electrodes with one electrode being placed at the forehead as a reference voltage while other two being placed on the either corner of the both eyes to capture the EOG voltage signals generated from the movements of left and right eyes.

3. The system for controlling hand orthosis using electrooculography as claimed in claim 1, wherein said electrode means are selected from Ag/AgCl electrodes or other types of electrodes capable of sensing EOG voltage signals.

4. The system for controlling hand orthosis using electrooculography as claimed in claim 1, wherein said signal conditioning unit comprises of at least one protective circuit, amplifier (201) and at least one filter circuit (202,203).

5. The system for controlling hand orthosis using electrooculography unit as claimed in claim 4, wherein protective circuit of the signal processing unit protects the circuit from unwanted voltage.

6. The system for controlling hand orthosis using electrooculography as claimed in claim 4, wherein said amplifier (201) is an instrumentation amplifier to amplify the EOG voltage signal captured by signal acquisition unit.

7. The system for controlling hand orthosis unit using electrooculography as claimed in claim 4, wherein filter circuit comprises of at least one low pass filter (202) for filtering unwanted high voltage and at least one summing amplifier (203).

8. The system for controlling hand orthosis using electrooculography as claimed in claim 1, wherein said signal processing unit (300) is an open electronic platform having at least one on-board microcontroller unit, said microcontroller unit comprising of
- analog to digital converter (A2D) capable of converting analog EOG voltage signals to integer values of said EOG voltage signals,
- means for eye movement identification (301) capable of calibrating said integer values of said EOG voltage signals,
- means for eye movement classification (302) capable of classifying said calibrated EOG voltage signals into sequence of eye movements.

9. The system for controlling hand orthosis using electrooculography as claimed in claim 1, wherein said sequence of eye movement is straight (1), right (2), straight (3), left(4), straight(5).

10. A method for hand orthosis control using electrooculography comprising the steps of :
- sensing of EOG voltage signals generated from the movements of eye by means of electrodes of signal acquisition unit (100),
- amplifying and filtering of said EOG voltage signals in the signal conditioning unit (200),
- processing of said EOG voltage signals in said signal processing unit (300) by converting said analog EOG voltage signals into their corresponding integer values of EOG voltage signals by Analog to Digital Converter (A2D), identifying the valid eye movement from the said integer values of EOG voltage signals by calibrating the same by means of Eye Movement Identification (301) and then classifying said calibrated EOG voltage signals (302) into sequence of movements of right and left eyes by means of Eye Movement Classification (302),
- generating control signals corresponding to said processed EOG voltage signals in signal processing unit (300) to servomotor which in turn controls the movement of the hand orthosis in predetermined manner .
11. The method for hand orthosis control using electrooculography as claimed in claim 10, wherein
- said identification of the valid eye movement (301) by means of Eye Movement Identification (301) from the EOG voltage signal levels,
o by initially calibrating the threshold integer value for the EOG voltage signals when user looks straight and then computing the average of discrete integer values of EOG voltage signals obtained from the signal conditioning unit when user looks from left to right or vice versa,
o by comparing the said average values with said threshold integer value to determine the shift from said calibrated threshold integer,
- classification of said EOG voltage signals (302) into the sequence of eye movements by means of Eye Movement Classification (302).
,TagSPECI:
FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(Section 10 and Rule 13)

1. TITLE OF THE INVENTION:

“HAND ORTHOSIS CONTROL USING ELECTROOCULOGRAPHY”

2. APPLICANT:

(a) Name: AMRITA VISHWA VIDYAPEETHAM (b) Nationality: India
(c) Address: Amritapuri, Clappana PO, Kollam-690525, Kerala, India

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION:
The present invention relates to control of hand orthosis using electrooculography. More particularly the present invention relates to system and method for controlling a motorized hand orthosis using electrooculography.

BACKGROUND OF THE INVENTION:
In Cerebrovascular accidents, spinal cords injuries, non-degenerative, degenerative neurological diseases or in some accidents, injuries can result in to neurological disabilities. Such neurological disabilities can reduce or damage the motor function of the affected person.

Rehabilitation specialists may advise the use of assistive devices during a patient’s daily activities. These assistive devices can increase their independence and can be helpful in rehabilitating them. In the current state of art there has been major progress in the development of these assistive devices which can compensate or assist the affected limbs.

These assistive devices include light weight versatile types of prosthetics, exoskeleton and orthotics like a hand orthosis and/or active ankle foot orthosis. However control of these assisted devices is still a challenge. For controlling these devices researchers have developed various methodologies which includes the use of bio-signals. Bio-signals are electrical signals which are obtained due to a change in the potential difference across tissues, muscles and organs in the body. This technique of using bio-signals for orthosis is very useful for the rehabilitation of patients suffering from complete or partial paralysis.

There are number of bio-signals classified on the basis of their origin in the body. The more popular bio-signals include the Electromyogram (EMG) and Electrooculography (EOG).

The EMG control signals are the signals generated from the action potentials of contracting muscle fibers. This method is attractive for patients with weak or small muscles. The EMG signals carry the distinct signature of the voluntary intent of the central nervous system (CNS). The example for these types of signals to control hand orthosis is depicted in the article, “Arm orthosis control based on surface EMG signal extraction” by Aeron et al in 8th International Conference, HAIS 2013 Salamanca, Spain on September 11-13, 2013.

The EOG signals are other electrical signals which correspond to the potential difference between the front end, i.e. cornea and the backend, i.e. retina of the eye. This cornea maintains the nearly potential of about 0.40 millivolt to 0.1 millivolt which is higher than the retina of the eye. The EOG signals are the electrical recording corresponding to the direction of the eye and are very useful for patients with severe cerebral palsy or those born with a congenital brain disorder or those who have suffered severe brain trauma because in these cases the eye movement is the only signaling which is not affected.

The EOG signals can be used to control the various types of assistive devices such as wheel chair and computer devices and has been researched in the state of art. One example is disclosed in the US Patent application WO 2004021157 published on March 11, 2004 which discloses the method and apparatus for generating control signals that simulate the computer mouse.
Further the use of EOG signals along with EMG signals to control the assistive devices is also disclosed in the prior art. The research paper titled “A Low cost EMG and EOG signal conditioning system for Brain computer interface application” by P Geethanjli et al discloses such system.

Despite the presence of such assisted device in the prior art there is still need of system which is cost effective and can easily control assistive devices, especially orthosis, by using one type of signal such as EOG signals.

OBJECTS OF THE INVENTION:
In order to obviate the drawbacks present in the current state of art technology the main object of the present invention is to provide a system and method to control hand orthosis using single form of bio-signals namely electrooculography (EOG signals).

Still another object of the present invention is to provide a system for controlling hand orthosis using electrooculography (EOG signals) which is cost effective and easy to use.

SUMMARY OF THE INVENTION:
Accordingly the present invention relates to system and method to control the hand orthosis using electrooculography. The system comprises of at least one signal acquisition unit for sensing EOG signals, at least one signal conditioning unit to amplify and condition the captured EOG signals, at least one signal processing unit and at least one hand orthosis.

The signal acquisition unit comprises of Ag/AgCl electrodes which are positioned around the skin to sense the EOG signals generated by the eye movements of the user. The sensed signals are then amplified and conditioned in the signal conditioning unit. The output from the signal conditioning unit is transferred to the signal processing unit. The signal processing unit which is an Arduino based electronic platform has an on- board microcontroller unit. The signal processing unit identifies valid eye movement from the EOG signals and then classifies them into either left or right movements. The signal processing unit generates the control signal based on the processed data to the servomotor of the hand orthosis to control its movement.

The advantages of the present system and method lie in its cost effectiveness, reliability and its ease of use which is lacking in the prior art systems. This can be used in the rehabilitation process of people who have met with neck injury or stroke etc. and lost partial control of their hands. This would help make the recovery process of such people faster and easier.

Accordingly the present invention provides a system for controlling hand orthosis using electrooculography. The system comprises of at least one signal acquisition unit having at least one electrodes means, at least one signal conditioning unit, at least one signal processing unit and at least one hand orthosis unit. The electrode means of the signal acquisition unit being positioned on the skin around the captures the electrooculogram (EOG) voltage signals which are being generated from the sequences of the movement of eyes of the user. The signal conditioning unit amplifies and filters the captured EOG signals. The signal processing unit processes the captured EOG voltage signals by first identifying said valid eye movement and then classifying the same into sequence of eye movements which in turn send the control signals corresponding to the processed EOG voltage signal to the servomotor to control the movement of hand orthosis unit

The signal processing unit is an open electronic platform having at least one on-board microcontroller unit. The microcontroller unit comprises of analog to digital converter (A2D), means for eye movement identification and means for classifying the eye movements. The A2D convertor is to convert analog EOG voltage signals to integer values of said EOG voltage signal. The means for eye movement identification is to calibrate the integer values of the EOG voltage signal and the means for eye movement classification is to classify the calibrated EOG voltage signals into the sequence of eye movements.

The present invention also provides the method for control of hand orthosis using electrooculography. The method comprises the step of sensing of EOG voltage signals generated from the movements of eyes by means of electrodes of signal acquisition unit. The method may further comprises the steps of amplifying and filtering the EOG voltage signals in the signal conditioning unit and then processing of the EOG voltage signals in the signal processing unit by converting the analog EOG voltage signals into their corresponding integer values by Analog to Digital Converter (A2D). The method may further comprise the step of identifying the valid eye movement from the integer values of EOG voltage signals by calibrating the same by means of Eye Movement Identification. The method may further comprise the steps of classifying the calibrated EOG voltage signals into sequence of movements of right and left eyes by means of Eye Movement Classification and generating control signals corresponding to said processed EOG voltage signals by signal processing unit to servomotor which in turn controls the movement of the hand orthosis in predetermined manner.

BRIEF DESCRIPTION OF DRAWINGS:
Fig 1 provides the schematic block/schematic diagram of the system.
Fig 2 depicts the EOG electrodes (100).
Fig 3 provides the block/schematic diagram of signal conditioning Unit.
Fig 4 illustrates the Signal Processing Unit in details.
Fig 5 illustrates the graphical representation of EOG signals obtained from the sequence: straight, right, straight, left, straight.
Fig 6(a) illustrates the opening of arm when eyes moves left
Fig 6(b) illustrates the closing of arm when eye moves right.

DETAIL DESCRIPTION OF THE INVENTION WITH ILLUSTRATIVE EXAMPLES:
The present invention relates to the system and method for controlling hand orthosis using electrooculography.

The term “electrooculography” in the specification means is a technique for measuring the cornea-retinal standing potential that exists between front and back of the human eye. The term “EOG voltage signals” refers to the resulting signals of potential difference caused by eye movements.

The term “Arduino” used in specification refers to as an open electronic platform intended to be used for the EOG signal processing for the identification of the EOG signal and classifying them as eye movements as either left or right. It has on the board microcontroller. The microcontroller is programmed with the assembly program for signal processing purpose.
The present invention provides the system which can control the orthosis by using EOG signals. The key to control the hand orthosis unit by EOG signals lies in mapping of the EOG signals generated from the eye movements of the subject to the orthosis through signal processing. As the system utilizes the EOG signals as sole controlling mechanism, therefore, the user does not require elaborate training to use the system. Thus the present invention facilitates faster and easier recovery process of people who have lost partial control of their hands.

The term “servomotor” in the specification refers to the motor which is essentially a rotatory actuator which can rotate or push a part of machine with great precision.

Fig 1 illustrates the schematic diagram of the system. The system comprises of signal acquisition unit (100), signal conditioning unit (200), signal processing unit (300) and hand orthosis unit (400).

Fig 2 illustrates the disposable, pre-gelled Ag/AgCl electrodes of the signal acquisition unit (100). The electrodes are placed in the region surrounding the eye to acquire the EOG signals. These electrodes are capable of measuring the EOG signals generated from the eye movements. As the vertical movement of the eyes accompanied with the blinks so the system only captures and uses the EOG signals generated from the horizontal movement of the eyes as a controlling signal to control the orthosis. In order to capture the horizontal movements one electrode each is placed on either corner of both eyes. The third electrode which acts as reference electrode is placed approximately at the center of the forehead.

Fig 3 depicts the signal conditioning unit (200) which comprises of an instrumentation amplifier (201), a low pass filter (202) and a summing amplifier (203). All these are used for conditioning of the EOG signals from the electrodes: removing the artifacts from the EOG signals and amplifying them.

Fig 4 depicts the signal processing unit (300). The signal processing unit (300) is Arduino based open electronic platform whose main function is to identify the valid eye movements (301), to classify said eye movements into sequence of eye movements (302) and then to send the same to orthosis unit (400) as a control signal. Arduino has analog I/O, digital I/O, serial receiver, serial transmission and power with at least one on board microcontroller unit. The hardware features of Arduino can be accessed, programmed and controlled by any mathematical programming software packages such as lab view, python or MATLAB. In the present system, Arduino is controlled and programmed through MATLAB using the Arduino IO Library (Reference:Mathworks.com). Arduino IO is a MATLAB support package for controlling an Arduino directly from MATLAB. It allows communication with an Arduino over a serial port. It consists of a MATLAB API on the host computer and a server program that runs on the Arduino. Together, they allow access and control to the Arduino’s analog I/O, digital I/O, and to operate servo motors, read encoders all from the MATLAB command lines.

Now referring back to the Figs 1, 2, 3 and 4, the Ag/AgCl electrodes of the signal acquisition unit (100) captures the EOG voltage signal and transfers them to the signal conditioning unit (200) through the protection circuit. The function of the protection circuit is to block the voltage greater than voltage supplied from power source.

In its initial stage as EOG biological signals are very small in strength i.e. in millivolts range so they are amplified in the signal conditioning unit (200) before their processing in signal processing unit (300). In signal conditioning unit, they are first passed through higher gain instrumentation amplifier (201) where they are amplified. Then amplified EOG voltage signals are passed through the filter circuit (202,203) of signal conditioning unit (200). The filter circuit comprises of low pass filter (202) and summing amplifier (203). The undesired frequencies of above 38 Hz in the EOG voltage signals are filtered in the low pass filter (202). The output from the low pass filter is then given as input to the summing amplifier where the amplification of the EOG voltage signals are carried out. The purpose of the summing amplifier is to bring the EOG voltage signals in 0 to 5V range, such that it can be read by the signal processing unit (300).

The output of the signal conditioning unit (200) is fed into analog input of Arduino based signal processing unit (300) where it is processed or analyzed through Arduino’s on board microcontroller for example ATMEGA microcontroller. The on board microcontroller has in-built A2D converter (Analog to digital converter). If required, the analysis of EOG voltage signals can be simulated in MATLAB to ensure that the obtained results are as expected. The inbuilt 10 bit ADC converts the incoming analog EOG voltage signals to integer values. The voltage levels from 0-5V are mapped to integer values between 0 and 1023.

In order to identify the valid eye movements, the on board microcontroller unit initially calibrates the threshold voltage integer value for the EOG voltage signals (Vo) when the user looks in straight direction. Then it continuously computes the average of around the 200 discrete values of EOG voltage signals coming from the signal conditioning unit (200), to see if there is increase or decrease in the said values from the calibrated threshold voltage signal, when the user's eyes are moved in right direction then there is increase in this average value from the threshold voltage and if the user's eyes are moved in left direction there is decrease in average value from the threshold voltage or vice versa. This change in the value of the average value with respect to the threshold voltage of potential (Vo) is used by the microcontroller unit of Arduino to classify the eye movements and to generate control signals which in turn control the operation of the servomotor of the hand orthosis. For example, when average value is greater than the threshold value then servomotor is rotated such that hand orthosis arms closes and if average is less than threshold voltage then servomotor is rotated such that hand orthosis arms opens. If it does not change then it remains the same.

The present invention also provides the method for controlling hand orthosis using electrooculography. The method comprises the steps of sensing of EOG voltage signals generated from the movements of eyes by means of electrodes of signal acquisition unit (100), amplifying and filtering said EOG voltage signals in the signal conditioning unit (200), processing of said EOG voltage signals in said signal processing unit (300) by converting the analog EOG voltage signals into their corresponding integer values by Analog to Digital Converter (A2D), identifying the valid eye movement from the said integer values of EOG voltage signals by calibrating the same by means of Eye Movement Identification (301) and then classifying said calibrated EOG voltage signals (302) into sequence of movements of right and left eyes by means of Eye Movement Classification (302), generating control signals corresponding to said processed EOG voltage signals by the signal processing unit to servomotor which in turn controls the movement of the hand orthosis in predetermined manner.

The present invention is now explained with reference to following non-limiting example:

EXAMPLE
There is a significant shift in the voltage levels or potential when the user moves his eyes to either left or right. The electrode means of the signal acquisition unit (100) are placed around the eye in the manner that the electrodes capture EOG voltage signals caused by change in potential due to the movement of eyes i.e. right and left eye movements as shown in Fig 6(a) and 6(b). Then this EOG voltage signals is passed into the signal conditioning unit (200) where it is amplified by via high gain instrumentation amplifier (201) and conditioned by filter circuit. Then it is transferred to signal processing unit (300) for processing. The system identifies and classifies the various EOG signals obtained from sequences of eye movements as straight (1) , right (2), straight (3) , left (4), straight (5) (as shown in Fig. 5). This identification and classification is done by the initial calibration of a central threshold voltage by the microcontroller unit of signal processing unit of the system when the user's eyes are in the straight direction and then by finding the average of around 200 discrete values to detect any increase or decrease from the calibrated threshold when the person looks to his left or right. When the average voltage value is greater than the threshold voltage, the servomotor is rotated such that hand orthosis arm closes shown in Fig 6 (b) and if average is less than the threshold voltage then servomotor is rotated such that the hand orthosis arm opens (Fig 6 (a)).