R Sai Krishna200701168BY Srinath Reddy200701174

Electromyography (EMG) Signals Instrumentation Interfacing EMG Signal Processing Applications

Electromyography (EMG) is the study of the electrical signals associated with the activation of muscle.Its originated in 1792 from work of Galvani.

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Myoelectric Energy Detection

Motor units control groups of muscle fibers

Myoelectric energy produced as motor units activate

A single moving dipole associated with changes in membrane potential.

The moving dipole is the basis for EMG, and triggers the contraction process.

Amplitude (mV) 0.01 - 5Primary Freq Range (Hz) 20 - 200Min Sampling Rate (Hz) 400Preferred Sample Rate (Hz) 1000

Input

1000 timesAmplifier

High Pass Filterfor DC voltage rejection

Low Pass Filterfor noise rejection

Voltage Adderfor AD conversion

Analog Switch for op-amp drift prevention

Circuit design for signal acquisition

Electrode and Amplifier Design

Differential amplification

Electrode stability

Improved quality of electrodes

Ambient (electromagnetic) noise is constant

System subtracts two signals

Resultant difference is amplified

Cancels out, or rejects, common components (noise) of the two signals coming from the active electrodes

Results in amplification of the differencebetween the signals

External noise may be reduced by using filters.

Amplifier will pick up frequencies produced by electrical activity in the muscle

Signal-to-noise ratio

Ratio of energy of EMG signal divided by energy of noise signal

Distortion of the signal

EMG signal should be altered as minimally as possible for accurate representation

Amplitude is somewhat random in nature.

Frequency range of 0 – 20 Hz is especially unstable.

Electromagnetic radiation sources.

Essentially impossible to avoid.

Dominant frequency: 60 Hz.

Amplitude: 1 – 3x EMG signal.

Generated by all electronics equipment.

Frequency range: 0 – several KHz.

Reduced by using high quality components

Types of Electrodes

Inserted

Fine-wire (Intra-muscular)

Needle

Surface

Advantages Extremely sensitive

Record single muscle activity

Disadvantages Extremely sensitive

Requires medical personnel, certification

Advantages Quick, easy to apply

Minimal discomfort

Disadvantages Generally used only for superficial muscles

Cross-talk concerns

No standard electrode placement

Electrode Placement Away from tendon

Away from outer edge of muscle

Closer to other musculature

Orientation parallel to muscle fibers

More accurate conduction velocity

As far away as possible from recording electrodes

Electrically neutral tissue

Bony prominence

Good electrical contact

Larger size

Good adhesive properties

Clinical applications like Bio-Feedback instruments

Cerebral Palsy

In Multi Touch operating systems using only Muscle operations

Motion Tracking

Indicator for muscle activation/deactivation

Relationship of force/EMG signal

Use of EMG signal as a fatigue index

Electronic or electromechanical instruments that accurately measures, processes, and provides feedback via auditory or visual signals

Used to help patient develop greater voluntary control of either

Neuromuscular relaxation, or

Muscle re-education following injury

Different sensitivity levels are used like 1 µV, 10 µV, or 100 µV.

A high sensitivity means the biofeedback unit is sensitive enough to detect the smallest amounts of electrical activity

Computer gamesStrengthen agonist

muscle groupsRelax/inhibit

antagonist muscle groups

Gait training

Patient able to make appropriate, small changes in performance which are immediately noted and rewarded

Eventually larger changes, or improvements, in performance can be accomplished

Most common type of biofeedback used in athletic training

To determine the electrical activity in the muscle, all negative waves are flipped upward toward the positive pole

The rectified EMG signal can be smoothed Eliminates the peaks and valleys which are produced

with a changing electrical signal

Once smoothed, the EMG signal may be integrated by measuring the area under the curve for a specified period of time

Microsoft Patented EMG Technology to Allow Touch Technology Using Only Muscle Operations.

It is studying the feasibility of muscle-computer input.

It aims at building a wireless module for sending and receiving inputs and outputs.

Biceps brachii ROM of an elbow joint

0~145 degrees

Deltoideus

ROM of a shoulder joint

0~180 degrees

Optimization Process

Recursive-least-squares method is applied to the pre-angle for self-adaptation.

The tap-weights are adjusted by itself during the optimization procedures.

Applications Master (human) arm device for tele-operation Prosthetic arm for an amputee.

NoraxonMotion Lab SystemsDelsys

Basmajian JV, De Luca CJ. Muscles Alive: their functions revealed by electromyography (fifth ed.). Williams & Wilkins, Baltimore, Maryland, 1985

Cram JR, Kasman GS. Introduction to surface electromyography. Aspen Publishers, Inc. Gaithersburg, Maryland, 1998

De Luca CJ: Surface electromyography: detection and recording. DelSys, Inc., 2002

De Luca CJ: The use of surface electromyography in biomechanics. J App Biomech 13: 135-163, 1997

MyoResearch: software for the EMG professional. Scottsdale, Arizona, Noraxon USA, 1996-1999

Thank You!