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.