Bio-signals patterns analysis problems have enjoyed a rapid increase in popularity in the past few years. The electromyography (EMG) signal, also referred to as the Myoelectric signal (MES), recorded at the surface of the skin, is one of the biosignals generated by the human body, representing a collection of electrical signals from the muscle fibre, acting as a physical variable of interest since it first appeared in the 1940s (Scott, 1984). It was considered to be the main focus of scientists, and was advanced as a natural approach for the control of prosthesis, since it is utilising the electrical action potential of the residual limb’s muscles remaining in the amputee’s stump (which still has normal innervations, and thus is subject to voluntary control) as a control signal to the prosthesis—in other words, it allows amputees to use the same mental process to control their prosthesis as they had used in controlling their physiological parts; however, the technology in that time was not adequate to make clinical application viable. With the development of semiconductor devices technology, and the associated decrease in device size and power requirements, the clinical applications saw promise, and research and development increased dramatically.
Key Terms in this Chapter
Grasp: To take hold of or seize firmly with, or as if with the hand.
Noninvasive Interfaces: Those interfaces that acquire signals transcutaneously, using surface electrodes, which are preprocessed to reduce noise content.
Electromyogram (EMG): These are electrical potentials arising from muscle movements. They originate from the motor cortex when the brain sends action potentials along appropriate nerve tracts. They then transmit to the muscle groups, resulting in contractions of the muscle fibers, and are accessible as bioelectric signals under direct volitional control.
Wavelet Transform: In mathematics, wavelets, wavelet analysis, and the wavelet transform refers to the representation of a signal in terms of a finite length or fast-decaying, oscillating waveform (known as the mother wavelet). This waveform is scaled and translated to match the input signal. In formal terms, this representation is a wavelet series, which is the coordinate representation of a square integrable function with respect to a complete, orthonormal set of basis functions for the Hilbert space of square integrable functions.
Rehabilitation: The process of restoration of skills by a person who has had an illness or injury, so as to regain maximum self-sufficiency, and function in a normal—or as near normal—manner as possible. For example, rehabilitation after a stroke may help the patient walk again and speak clearly again.
Biocontrol System: A mechanical system that is controlled by biological signals—for example, a prosthesis controlled by muscle activity.
Myoelectric Control: A man-machine control scheme in which myoelectric signals are used as control signals.