Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-05-23
2001-04-17
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S439000, C340S545400, C340S575000, C180S272000
Reexamination Certificate
active
06218947
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to safety devices and, more particularly, to a driver sleep alarm for use in a vehicle which detects the condition of sleepiness or inattentive driving and alerts the driver thereof.
The reality of drivers becoming increasingly drowsy or even falling asleep while driving is a grave problem which carries well-publicized consequences. Even a momentary lapse in mental alertness and attentiveness often leads to the long-lasting disability or even death of the drowsy driver or to others. In addition, the grisly statistics of vehicular accidents resulting from drowsy drivers or drivers lacking adequate alertness due to drug or alcohol consumption do not reflect the mental anguish and sorrow suffered by the family and friends of persons needlessly injured or killed.
Many devices have been proposed in the art for alerting drivers of the condition of drowsiness. Many of these devices may be categorized as pressure responsive or grip-sensitive devices. Maintaining sufficient pressure on a steering wheel or other grip-sensitive structure for long periods of time, however, may lead to even further driver fatigue. In addition, implementation of pressure sensing transducers is complex and expensive, especially those which are adaptable to the pressure exerted by different drivers of a single vehicle.
Other systems, such as the alarm disclosed in U.S. Pat. No. 4,259,665, utilize a pair of conductive plates spaced apart about a steering wheel between which a current is communicated through the hand of the driver when placed in contact therewith. It has been found, however, that such a system is prone to electrical shorting from condensation on the steering wheel. Another problem is dry contact resistance wherein current is not delivered between the plates because a person's skin is very dry or the driver is wearing gloves. Still another problem with conductive systems is that the plates may become soiled and thus unable to consistently deliver current therebetween.
Another category of sleep alarms includes optical devices which must be worn about a driver's head or neck. These devices also contribute to driver fatigue as the driver holds his head rigidly so as to avoid inadvertently tripping the alarm. Other optical systems are mounted on the steering wheel itself and use optical beam deflection to monitor finger placement. These systems, however, require a protrusion on the back of the steering wheel for the light beam-shaping lens and require a driver's fingers to extend through the protrusions in an uncomfortable and unfamiliar manner.
Many sleep alarms from each of the above described categories include manual disabling switches whereby a driver may completely deactivate the device. Unfortunately, the complexity or disadvantages of these system often leads to such deactivation and non-use by drivers.
Therefore, it is desirable to have a driver sleep alarm which overcomes the above described disadvantages by sensing the position of a driver's fingertips on, or in close proximity to, a steering wheel without requiring any level of grip pressure, circuit formation, or optical sensing. Further, it is desirable to have a driver sleep alarm which operates effectively even when a driver is wearing gloves. In addition, it is desirable to have a driver sleep alarm which is not affected by humidity, condensation, light, or other environmental conditions. Finally, it is desirable to have a driver sleep alarm which may only be temporarily disabled by a driver.
SUMMARY OF THE INVENTION
The preferred embodiment of the present invention comprises a pair of conductive plates attached to opposed sides of a steering wheel rim in a spaced apart arrangement. The first conductive plate is attached to the front side of the steering wheel rim and is electrically grounded. The second conductive plate is attached to the back side of the rim.
A monitoring circuit is electrically connected to the second conductive plate for sensing the capacitance of the second conductive plate relative to the first conductive plate. The capacitance thereof corresponds to a touching, or near touching, of the steering wheel at the approximate position of the second conductive plate by the fingertips of the driver. The monitoring circuit provides a voltage to the second plate for charging the second plate and for measuring the capacitance thereof relative to the first grounded plate. The monitoring circuit is connected to a voltage source such as the vehicle battery and includes a clock element and a pair of monostable multi-vibrators, also known as “one-shots”, which are initiated by the rising edge of a clock pulse (P1). A first one-shot is connected to the second plate and measures the capacitance thereof. A proximate touching of the second plate affects the capacitance thereof and, thus, the speed at which that plate is charged. The first one-shot generates a pulse (P2) having a width representing the speed with which the second plate is charged. The second one-shot operates as a reference and therefore generates a reference pulse (P3) having substantially the same width during every clock cycle. The pulse width of the reference one-shot is adjustable, thus affecting the “sensitivity” of the steering wheel to a driver's hand. At its most sensitive setting, a driver need not even physically touch the steering wheel to successfully make “proximate” contact therewith. Therefore, this invention effectively establishes an “electric field” about the steering wheel to monitor the position of a driver's fingertips thereabout.
A D-type flip-flop is used to compare the width of pulse P2 and P3. The pulse (P2) generated by the first one-shot is delivered to the data pin of a D-type flip-flop or comparator. The clock pulse (P3) is delivered to the clock input pin of the flip-flop. The data pin is read only upon receipt of a downward edge of a clock pulse. In the case where the second plate has been charged before the downward transition of the clock pulse (P3), then the pulse (P2) will have a width less than that of the clock pulse (P3) and will therefore register a “low” or “0” into the flip-flop. This is indicative of a removal or release of a driver's fingertips from the back side of the steering wheel and an alarm is activated. Conversely, if the second plate is still charging and thus is still registering a “high” pulse when a downward edge of a clock pulse (P3) is received by the flip-flop, a “high” or “1” is registered in the flip-flop. This is indicative of the driver's fingertips touching the steering wheel rim at the proximate location of the second conductive plate and the alarm is disabled.
A touching, or near touching depending on the capacitive sensitivity, of the steering wheel rim proximate to the second plate affects capacitance because capacitance is directly proportional to the surface area of the plates and inversely proportional to the distance between the plates. Therefore, capacitance increases as a person's finger, which has ground potential, is moved closer to the second plate. Sensing capacitance of a plate positioned on the back side of the steering wheel rim is extremely advantageous in that an uncurling of a user's fingertips from about the rim is indicative of drowsiness or inattentiveness.
The preferred embodiment of this invention may include a speed sensor adapted to disable the alarm when the vehicle is traveling at a rate less than a predetermined speed. The invention may also include a noise sensor for sensing engine, radio, or other ambient noise so as to automatically adjust the volume of the alarm or to reduce the volume of one or more of the engine noises upon alarm activation. The alarm may also be disabled by the driver for selectable amounts of time.
Therefore, a general object of this invention is to provide a driver sleep alarm which continually monitors placement of a driver's fingertips on or about a steering wheel by sensing changes in the capacitance of capacitive sensitive elem
Hofsass Jeffery
Nguyen Phung T.
Ream Dale J.
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