Patent No. 4158196 Man-machine interface system
Patent No. 4158196 Man-machine interface system (Crawford, Jr., Jun 12 1979)
Abstract
The system provides a direct electrical interface between the electrical activity that may be self-induced in the human nervous system and the electrical activity in devices such as computers or calculators. Either one-way or two-way communication and/or control may be provided. For man-to-machine (efferent) communication bioelectric activity is monitored with electrodes and the action potentials which are self-generated are converted into digital signals preferably in the form of binary signals which may be interpreted by digital computers, micro-processors or other logic systems. For machine-to-man (afferent) communication binary signals in the form of binary ones or zeros are converted to action potentials. Depending upon the particular application, different codes are used to give specific meanings to specific patterns of bioelectric activity that the operator generates and specific patterns of electric stimulation that the operator receives. For example, if the system is used to replace a teletype terminal used to communicate with the computer, each specific pattern generated by the operator corresponds to a keyboard character with the need in this case for multiple channels for communication. In one system according to the invention the control is used by a handicapped person to manipulate a wheelchair with each specific pattern of bioelectric activity corresponding to a direction of movement of the wheelchair. In the wheelchair application two-way communication is provided and binary signals are generated from two separately excitable electrode sites with the code being sent employing successive communication time slots. For any given application, the operator is required to learn an appropriate code. After sufficient practice, the codes become subliminal in the same way as an experienced typist is not consciously concerned with the details of the finger movement.
Notes:
Man-machine
interface. Filed April 1977, Granted June 1979. 1st paragraph under background
of the invention, in the first sentence, replace the word direct with remote
and electrical with electromagnetic. The impulses or action potentials as the
patent states that are picked up by electrodes in the trapezius muscles are
action potentials or impulses that originate in the brain before traversing
the nervous system to the trapezius muscles.
BACKGROUND
OF THE INVENTION
The present invention relates in general to a direct, electrical, man-machine
interface system. More particularly, the present invention is concerned with
a man-machine interface system that permits direct communication with a digital
device such as a computer, micro-processor or calculator. The system of this
invention may also be implemented as a two-way communication system permitting
the conversion of bioelectric activity into digital signals and vice-versa.
Man is becoming continuously more dependent upon the services of computers,
micro-processors, hard-wired logic circuitry and mechanical and electrical devices
that are controlled and/or monitored by these digital devices. Of course, in
order for electrically controlled machinery to serve man, provisions must be
made for man-machine interfaces. Typical devices presently used for performing
this interface function are teletype terminals and similar keyboards, cathode
ray tube displays, consoles with switches and indicator lamps, card readers,
and magnetic tape drives.
A limited number of special purpose systems have been developed to control prosthetic
devices such as artificial limbs by using amplified and rectified myoelectric
signals to switch on drive motors. However, these systems are not capable of
direct electrical interface with a digital system such as a computer or calculator.
These systems do not provide coding for controlling a digital system but simply
convert directly a self-induced bioelectric activity into a mechanical action.
Accordingly, one object of the present invention is to provide a direct electrical
man-machine interface system for permitting direct communication between the
human nervous system and a man-made digital system. In accordance with the object
of this invention there is no longer the need for awkward interface devices
such as keyboards, switches and displays.
Another object of the present invention is to provide a man-machine interface
system for converting bioelectrical activity to either a single channel or multi-channel
stream of digital signals that can serve as an input to a computer, micro-processor,
discreet logic network or any system using digital input signals. These digital
input signals are usually in binary form in binary ones and zeros.
A further object of the present invention is to provide a man-machine interface
system that additionally provides information flow from the digital system to
the operator by converting digital signals into electrical stimuli induced in
the operator.
Still another object of the present invention is to provide an interface system
that provides different time slots for code communication, preferably in combination
with acknowledgement signals transferred from the digital system to the operator.
SUMMARY OF THE INVENTION
To accomplish the foregoing and other objects of this invention there is provided,
apparatus for direct electrical man-machine communication comprising electrode
means for detecting bioelectric signals which are then preferably electronically
amplified and converted to a digital format preferably using digital signal
processing circuitry. The electrode means may comprise surface electrodes, implanted
electrodes or any other type that may be used to monitor bioelectric activity
in muscle fibers, nerve cells, or nerve fibers. The amplifier that is used for
amplifying the bioelectric signals provides adequate gain for these signals
suitable for triggering standard digital logic. The amplifier also provides
pass band filtering to eliminate noise at frequencies that contain little energy
of the bioelectric signal spectrum and has an adequate low noise figure to prevent
masking the weak bioelectric signals with amplifier noise. In addition, for
multichannel, two-way communication systems, the amplifier inputs are isolated
from each other and from any common ground to prevent the conduction of stimulating
current from a desired stimulation site to other sites, resulting in cross talk
among the channels. The digital signal processing circuitry may comprise a threshhold
detector, the output of which triggers a monostable multi-vibrator which in
turn generates a standard digital pulse preferably of predetermined width.
For machine-to-man information transfer, digital pulses are converted into bioelectric
stimulation pulses that are applied to the operator with electrodes. With the
use of an appropriate multiplexer the same electrodes may be used as were used
for information flow from the operator (efferent flow direction). In one form
a digital pulse is used to trigger a monostable multi-vibrator that has an "on"
time equal to the desired width of the stimulation pulse. The output of the
multi-vibrator is used to gate a constant current source. The use of a constant
current source is convenient to maintain the stimulation level in the limited
dynamic range between the threshhold of detection and the threshhold of an unpleasant
shocking effect, as the electrode impedance varies over a period of time. For
multi-channel operation, output isolation using such techniques as optical coupling
or transformer coupling is used to confine the stimulation for each channel
to the desired location.
In accordance with the invention information transfer can occur either in serial
fashion or in parallel fashion. For parallel transfer a number of channels are
used and an entire binary word is communicated in parallel. For serial communication
in a simplified system disclosed herein two channels are used and the signals
are communicated in successive time slots. These time slots may be separated
by an acknowledgement time period wherein a signal is coupled from the digital
system to the operator indicating receipt in the first code in the first time
slot. In another system using a simple code there are provided two channels,
one for representing a dot and the other for representing a dash thereby allowing
the use of Morse code that the user may already be familiar with.
Comments