CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to
U.S. application Serial No. 10/714,572 filed November 13, 2003 by Patrick
W. Smith, et al.
; and claims priority under 35 U.S.C. § 119(e) to
U.S. application serial number 60/509,577 filed on October 7, 2003 by Patrick
Smith et al.
; and to copending
U.S. application serial number 60/509,480 filed on October 8, 2003 by Patrick
Smith et al
FIELD OF THE INVENTION
Embodiments of the present invention generally relate to
systems and methods for reducing mobility in a person or animal.
BACKGROUND OF THE INVENTION
Weapons that deliver electrified projectiles have been
used for self defense and law enforcement. These weapons typically deliver a stimulus
signal through a target where the target is a human being or an animal. One conventional
class of such weapons includes conducted energy weapons of the type described in
U.S. Patents 3,803,463
4,253,132 to Cover
. These weapons typically fire projectiles toward the target so that electrodes
carried by the projectile make contact with the target, completing a circuit that
delivers a stimulus signal via tether wires through the electrodes and through the
target. Other conventional conducted energy weapons omit the projectiles and deliver
a stimulus signal through electrodes placed in contact with the target when the
target is in close proximity to the weapon.
The stimulus signal may include a series of relatively
high voltage pulses known to cause pain in the target. At the time that the stimulus
signal is delivered, a high impedance gap (e.g., air or clothing) may exist between
electrodes and the target's conductive tissue. Conventional stimulus signals include
a relatively high voltage (e.g., about 50,000 volts) signal to ionize a pathway
across such a gap of up to 2 inches. Consequently, the stimulus signal may be conducted
through the target's tissue without penetration of the projectile into the tissue.
In some conventional conducted energy weapons, a relatively
higher energy waveform has been used. This waveform was developed from studies using
anesthetized pigs to measure the muscular response of a mammalian subject to an
energy weapon's stimulation. Devices using the higher energy waveform are called
Electro-Muscular Disruption (EMD) devices and are of the type generally described
US 6 636 412
An EMD waveform applied to an animal's skeletal muscle
typically causes that skeletal muscle to violently contract. The EMD waveform apparently
overrides the target's nervous system's muscular control, causing involuntary lockup
of the skeletal muscle, and may result in complete immobilization of the target.
Unfortunately, the relatively higher energy EMD waveform
is generally produced from a higher power capability energy source. In one implementation,
a handheld launch device includes 8 AA size (1.5 volt nominal) batteries, a large
capacity capacitor, and transformers to generate a 26-watt EMD output in a tethered
A two pulse waveform of the type described in
US 7 102 870
, provides a relatively high voltage, lower amperage pulse (to form an
arc through a gap as discussed above) followed by a relatively low voltage, higher
amperage pulse (to stimulate the target). Effects on skeletal muscles may be achieved
with 80% less power than used for the EMD waveform discussed above.
There exists a significant need for a more effective stimulus
signal for use in conducted energy weapons to immobilize a human target without
lasting injury or death. In the decade preceding this application, annually over
30,000 people died of bullet wounds in the United States. Further, thousands of
police officers are injured as a result of confrontations with non compliant members
of the general public each year. Even larger numbers of these non-compliant subjects
are injured in the process of being taken into police custody. Without systems and
methods for delivering more effective stimulus signals, further improvements in
cost, reliability, range, and effectiveness cannot be realized for conducted energy
weapons. Applications for conducted energy weapons will remain limited, hampering
law enforcement and failing to provide increased self defense to individuals.
SUMMARY OF THE INVENTION
An immobilization device includes three or more electrodes
and a signal generator selectively coupled to a first electrode, to a second electrode,
and to a third electrode. The signal generator provides a test signal via the first
electrode and the second electrode to prompt movement of the target toward the third
electrode. The signal generator also provides a stimulus signal for immobilization
via the third electrode. The third electrode is arranged to come into contact with
the target as a consequence of movement of the target.
A method for immobilizing a target includes in any order:
(a) providing a first electrode in contact with the target and a second electrode
in contact with the target; (b) providing a first signal via the first electrode
and the second electrode; (c) providing a third electrode for coming into contact
with the target as a consequence of movement of the target in response to the first
signal; and (d) providing an immobilizing signal via the third electrode.
A method, according to claim 1, for selecting a subset
of electrodes from a plurality of electrodes, the subset for use in immobilizing
a target, includes: (a) recalling a stored sequence of entries, each entry identifying
a respective subset of electrodes; and (b) sequentially testing subsets in accordance
with the sequence of entries.
An immobilization device, according to claim 4, includes
a signal source that provides an immobilization signal; a plurality of electrodes;
and a circuit. The circuit selectively couples each of a multiplicity of subsets
of electrodes of the plurality of electrodes to the signal source for delivery of
the immobilization signal via a selected subset of electrodes.
Furthermore a projectile according to claim 8, a system
for immobilizing a target according to claim 9 and a launch device according to
claims 10 and 11 are further aspects of the invention and solve the problems discussed
above at least in part by more effectively immobilizing a target, by reducing the
risk of serious injury or death, and/or by immobilizing for a period of time with
an expenditure of energy less than systems using techniques of the prior art.
BRIEF DESCRIPTION OF THE DRAWING
Embodiments of the present invention will now be further
described with reference to the drawing, wherein like designations denote like elements,
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
- FIG. 1 is a functional block diagram of a system that uses a stimulus signal
for immobilization according to various aspects of the present invention;
- FIG. 2 is a functional block diagram of an immobilization device used in the
system of FIG. 1;
- FIG. 3 is a timing diagram for a stimulus signal provided by the immobilization
device of FIG. 2; and
- FIG. 4 is a functional flow diagram for a process performed by the immobilization
device of FIG. 2.
A system according to various aspects of the present invention
delivers a stimulus signal to an animal to immobilize the animal. Immobilization
is suitably temporary, for example, to remove the animal from danger or to thwart
actions by the animal such as for applying more permanent restraints on mobility.
Electrodes may come into contact with the animal by the animal's own action (e.g.,
motion of the animal toward an electrode), by propelling the electrode toward the
animal (e.g., electrodes being part of an electrified projectile), by deployment
mechanisms, and/or by gravity. For example, system 100 of FIGs. 1-4 includes launch
device 102 and cartridge 104. Cartridge 104 includes one or more projectiles 132,
each having a waveform generator 136.
Launch device 102 includes power supply 112, aiming apparatus
114, propulsion apparatus 116, and waveform controller 122. Propulsion apparatus
116 includes propulsion activator 118 and propellant 120. In an alternate implementation,
propellant 120 is part of cartridge 104. Waveform controller 122 may be omitted
with commensurate simplification of waveform generator 136, discussed below.
Any conventional materials and technology may be employed
in the manufacture and operation of launch device 102. For example, power supply
112 may include one or more rechargeable batteries, aiming apparatus 114 may include
a laser gun sight, propulsion activator 118 may include a mechanical trigger similar
in some respects to the trigger of a hand gun, and propellant 120 may include compressed
nitrogen gas. In one implementation, launch device is handheld and operable in a
manner similar to a conventional hand gun. In operation, cartridge 104 is mounted
on or in launch device 102, manual operation by the user causes the projectile bearing
electrodes to be propelled away from launch device 102 and toward a target (e.g.,
an animal such as a human), and after the electrodes become electrically coupled
to the target, a stimulus signal is delivered through a portion of the tissue of
Projectile 132 may be tethered to launch device 102 and
suitable circuitry in launch device 102 (not shown) using any conventional technology
for purposes of providing substitute or auxiliary power to power source 134; triggering,
retriggering, or controlling waveform generator 136; activating, reactivating, or
controlling deployment; and/or receiving signals at launch device 102 provided from
electrodes 142 in cooperation with instrumentation in projectile 132 (not shown).
A waveform controller includes a wireless communication
interface and a user interface. The communication interface may include a radio
or an infrared transceiver. The user interface may include a keypad and flat panel
display. For example, waveform controller 122 forms and maintains a link by radio
communication with waveform generator 136 for control and telemetry using conventional
signaling and data communication protocols. Waveform controller 122 includes an
operator interface capable of displaying status to the user of system 100 and capable
of issuing controls (e.g., commands, messages, or signals) to waveform generator
136 automatically or as desired by the user. Controls serve to control any aspect
and/or collect data from any circuit of projectile 132. Controls may affect time
and amplitude characteristics of the stimulus signal including overall start, restart,
and stop functions. Telemetry may include feedback control of any function of waveform
generator 136 or other instrumentation in projectile 132 implemented with conventional
technology (not shown). Status may include any characteristics of the stimulus signal
and stimulus signal delivery circuit.
Cartridge 104 includes projectile 132 having power source
134, waveform generator 136, and electrode deployment apparatus 138. Electrode deployment
apparatus 138 includes deployment activator 140 and one or more electrodes 142.
Power source 134 may include any conventional battery selected for relatively high
energy output to volume ratio. Waveform generator 136 receives power from power
source 134 and generates a stimulus signal according to various aspects of the present
invention. The stimulus signal is delivered into a circuit that is completed by
a path through the target via electrodes 142. Power source 134, waveform generator
136, and electrodes 142 cooperate to form a stimulus signal delivery circuit that
may further include one or more additional electrodes not deployed by deployment
activator 142 (e.g., placed by impact of projectile 132).
Projectile 132 may include a body having compartments or
other structures for mounting power source 134, a circuit assembly for waveform
generator 136, and electrode deployment apparatus 138. The body may be formed in
a conventional shape for ballistics (e.g., a wetted aerodynamic form).
An electrode deployment apparatus includes any mechanism
that moves electrodes from a stowed configuration to a deployed configuration. For
example, in an implementation where electrodes 142 are part of a projectile propelled
through the atmosphere to the target, a stowed configuration provides aerodynamic
stability for accurate travel of the projectile. A deployed configuration completes
a stimulus signal delivery circuit directly via impaling the tissue or indirectly
via an arc into the tissue. A separation of about 17,8 cm (7 inches) has been found
to be more effective than a separation of about 3,81 cm (1.5 inches), and, longer
separations may also be suitable such as an electrode in the thigh and another in
the hand. When the electrodes are further apart, the stimulus signal apparently
passes through more tissue, creating more effective stimulation.
According to various aspects of the present invention,
deployment of electrodes is activated after contact is made by projectile 132 and
the target. Contact may be determined by a change in orientation of the deployment
activator; a change in position of the deployment activator with respect to the
projectile body; a change in direction, velocity, or acceleration of the deployment
activator; and/or a change in conductivity between electrodes (e.g., 142 or electrodes
placed by impact of projectile 132 and the target). A deployment activator 140 that
detects impact by mechanical characteristics and deploys electrodes by the release
or redirection of mechanical energy is preferred for low cost projectiles.
Deployment of electrodes, according to various aspects
of the present invention, may be facilitated by behavior of the target. For example,
one or more closely spaced electrodes at the front of the projectile may attach
to a target to excite a painful reaction in the target. One or more electrodes may
be exposed and suitably directed (e.g., away from the target). Exposure may be either
during flight or after impact. Pain in the target may be caused by the barb of the
electrode stuck into the target's flesh or, if there are two closely space electrodes,
delivery of a stimulus signal between the closely spaced electrodes. While these
electrodes may be too close together for suitable immobilization, the stimulus signal
may create sufficient pain and disorientation. A typical response behavior to pain
is to grab at the perceived cause of pain with the hands (or mouth, in the case
of an animal) in an attempt to remove the electrodes. This so called "hand trap"
approach uses this typical response behavior to implant the one or more exposed
electrodes into the hand (or mouth) of the target. By grabbing at the projectile,
the one or more exposed electrodes impale the target's hand (or mouth). The exposed
electrodes in the hand (or mouth) of the target are generally well spaced apart
from other electrodes so that stimulation between another electrode and an exposed
electrode may allow suitable immobilization.
In an alternate system implementation, launch device 102,
cartridge 104, and projectile 132 are omitted; and power source 134, waveform generator
136, and electrode deployment apparatus 138 are formed as an immobilization device
150 adapted for other conventional forms of placement on or in the vicinity of the
target. In another alternate implementation, deployment apparatus 138 is omitted
and electrodes 142 are placed by target behavior and/or gravity. Immobilization
device 150 may be packaged using conventional technology for personal security (e.g.,
planting in a human target's clothing or in an animal's hide for future activation),
facility security (e.g., providing time for surveillance cameras, equipment shutdown,
or emergency response), or military purposes (e.g., land mine).
Projectile 132 may be lethal or non-lethal. In alternate
implementations, projectile 132 includes any conventional technology for administering
Immobilization as discussed herein includes any restraint
of voluntary motion by the target. For example, immobilization may include causing
pain or interfering with normal muscle function. Immobilization need not include
all motion or all muscles of the target. Preferably, involuntary muscle functions
(e.g., for circulation and respiration) are not disturbed. In variations where placement
of electrodes is regional, loss of function of one or more skeletal muscles accomplishes
suitable immobilization. In another implementation, suitable intensity of pain is
caused to upset the target's ability to complete a motor task, thereby incapacitating
and disabling the target.
Alternate implementations of launch device 102 may include
or substitute conventionally available weapons (e.g., firearms, grenade launchers,
vehicle mounted artillery). Projectile 132 may be delivered via an explosive charge
120 (e.g., gunpowder, black powder). Projectile 132 may alternatively be propelled
via a discharge of compressed gas (e.g., nitrogen or carbon dioxide) and/or a rapid
release of pressure (e.g., spring force, or force created by a chemical reaction
such as a reaction of the type used in automobile air-bag deployment).
A waveform generator, according to various aspects of the
present invention, may, in any order perform one or more of the following operations:
select electrodes for use in a stimulus signal delivery circuit, ionize air in a
gap between the electrode and the target, provide an initial stimulus signal, provide
alternate stimulus signals, and respond to operator input to control any of the
aforementioned operations. In one implementation, a large portion of these operations
are controlled by firmware performed by a processor to permit miniaturization of
the waveform generator, reduce costs, and improve reliability. For example, waveform
generator 200 of FIG. 2 may be used as waveform generator 136 discussed above. Waveform
generator 200 includes low voltage power supply 204, high voltage power supply 206,
switches 208, processor circuit 220, and transceiver 240.
The low voltage power supply receives a DC voltage from
power source 134 and provides other DC voltages for operation of waveform generator
200. For example, low voltage power supply 204 may include a conventional switching
power supply circuit (e.g., LTC3401 marketed by Linear Technology) to receive 1.5
volts from a battery of source 134 and supply 5 volts and 3.3 volts DC.
The high voltage power supply receives an unregulated DC
voltage from a low voltage power supply and provides a pulsed, relatively high voltage
waveform as stimulus signal VP. For example, high voltage power supply 206 includes
switching power supply 232, transformer 234, rectifier 236, and storage capacitor
C 12 all of conventional technology. In one implementation, switching power supply
232 comprising a conventional circuit (e.g., LTC1871 marketed by Linear Technology)
receives 5 volts DC from low voltage power supply 204 and provides a relatively
low AC voltage for transformer 234. A feedback control signal into switching power
supply 232 assures that the peak voltage of signal VP does not exceed a limit (e.g.,
500 volts). Transformer 234 steps up the relatively low AC voltage on its primary
winding to a relatively high AC voltage on each of two secondary windings (e.g.,
500 volts). Rectifier 236 provides DC current for charging capacitor C12.
Switches 208 form stimulus signal VP across electrode(s)
by conducting for a brief period of time to form each pulse; followed by opening.
The discharge voltage available from capacitor C12 decreases during the pulse duration.
When switches 208 are open, capacitor C12 may be recharged to provide the same discharge
voltage for each pulse.
Processor circuit 220 includes a conventional programmable
controller circuit having a microprocessor, memory, and analog to digital converter
programmed according to various aspects of the present invention, to perform methods
A projectile-based transceiver communicates with a waveform
controller as discussed above. For example, transceiver 240 includes a radio frequency
(e.g., about 450 MHz) transmitter and receiver adapted for data communication between
projectile 132 and launch device 102 at any time. A communication link between 136
and 122 may be established in any suitable configuration of projectile 132 depending
for example on placement and design of radiators and pickups suitable for the communication
link (e.g., antennas or infrared devices). In one implementation projectile 132
operates in four configurations: (1) a stowed configuration, where aerodynamic fins
and deployable electrodes are in storage locations and orientations; (2) an in flight
configuration, where aerodynamic fins are in position extended away from projectile
132; (3) an impact configuration after contact with the target; and (4) an electrode
A stimulus signal includes any signal delivered via electrodes
to establish or maintain a stimulus signal delivery circuit through the target,
and/or to immobilize the target. According to various aspects of the present invention,
these purposes are accomplished with a signal having a plurality of stages. Each
stage comprises a period of time during which one or more waveforms are consecutively
delivered via a waveform generator and electrodes coupled to the waveform generator.
Stages from which a complete waveform, according to various aspects of the present
invention may be constructed include in any order: (a) a path formation stage for
ionizing an air gap that may be in series with the electrode to the targets tissue;
(b) a path testing stage for measuring an electrical characteristic of the stimulus
signal delivery circuit (e.g., whether or not an air gap exists in series with the
target's tissue); (c) a strike stage for immobilizing the target; (d) a hold stage
for discouraging further motion by the target; and (e) a rest stage for permitting
limited mobility by the target (e.g., to allow the target to catch a breath).
An example of signal characteristics for each stage is
described in FIG. 3. In FIG. 3, two stages of a stimulus signal are attributed to
path management and three stages are attributed to target management. The waveform
shape of each stage may have positive amplitude (as shown), inverse amplitude, or
alternate between positive and inverse amplitudes in repetitions of the same stage.
Path management stages include a path formation stage and a path testing stage as
In the path formation stage, a waveform shape may include
an initial peak (voltage or current), subsequent lesser peaks alternating in polarity,
and a decaying amplitude tail. The initial peak voltage may exceed the ionization
potential for an air gap of expected length (e.g., about 50 Kvolts, preferably about
10 Kvolts). In one implementation, the waveform shape is formed as a decaying oscillation
from a conventional resonant circuit. One waveform shape having one or more peaks
may be sufficient to ionize a path crossing a gap (e.g., air). Repetition of applying
such a waveform shape may follow a path testing stage (or monitoring concurrent
with another stage) that concludes that ionization is needed and is to be attempted
again (e.g., prior attempt failed, or ionized air is disrupted).
In a path testing stage, a voltage waveform is sourced
and impressed across a pair of electrodes to determine whether the path has one
or more electrical characteristics sufficient for entry into a path formation, strike,
or hold stage. Path impedance may be determined by any conventional technique, for
instance, monitoring an initial voltage and a final voltage across a capacitor that
is coupled for a predetermined period of time to supply current into electrodes.
In one implementation, the shape of the voltage pulse is substantially rectangular
having a peak amplitude of about 450 volts, and having a duration of about 10 microseconds.
A path may be tested several times in succession to form an average test result,
for instance from one to three voltage pulses, as discussed above. Testing of all
combinations of electrodes may be accomplished in about one millisecond. Results
of path testing may be used to select a pair of electrodes to use for a subsequent
path formation, strike, or hold stage. Selection may be made without completing
tests on all possible pairs of electrodes, for instance, when electrode pairs are
tested in a sequence from most preferred to least preferred.
In a strike stage, a voltage waveform is sourced and impressed
across a pair of electrodes. Typically this waveform is sufficient to interfere
with voluntary control of the target's skeletal muscles, particularly the muscles
of the thighs and/or calves. In another implementation, use of the hands, feet,
legs and arms are included in the effected immobilization. The pair may be as selected
during a test stage; or as prepared for conduction by a path formation stage. According
to various aspects of the present invention, the shape of the waveform used in a
strike stage includes a pulse with decreasing amplitude (e.g., a trapezoid shape).
In one implementation, the shape of the waveform is generated from a capacitor discharge
between an initial voltage and a termination voltage.
The initial voltage may be a relatively high voltage for
paths that include ionization to be maintained or a relatively low voltage for paths
that do not include ionization. The initial voltage may correspond to a stimulus
peak voltage (SPV) as in FIG. 3 (e.g., at about a skeletal muscle nerve action potential).
The SPV may be essentially the initial voltage for a fast rise time waveform. The
SPV following ionization may be from about 3 Kvolts to about 6 Kvolts, preferably
about 5 Kvolts. The SPV without ionization may be from about 100 to about 600 volts,
preferably from about 350 volts to about 500 volts, most preferably about 400 volts.
The termination voltage may be determined to deliver a
predetermined charge per pulse. Charge per pulse minimum may be designed to assure
continuous muscle contraction as opposed to discontinuous muscle twitches. Continuous
muscle contraction has been observed in human targets where charge per pulse is
above about 15 microcoulombs. A minimum of about 50 microcoulombs is used in one
implementation. A minimum of 85 microcoulombs is preferred, though higher energy
expenditure accompanies the higher minimum charge per pulse.
Charge per pulse maximum may be determined to avoid cardiac
fibrillation in the target. For human targets, fibrillation has been observed at
1355 microcoulombs per pulse and higher. The value 1355 is an average observed over
a relatively wide range of pulse repetition rates (e.g., from about 5 to 50 pulses
per second), over a relatively wide range of pulse durations consistent with variation
in resistance of the target (e.g., from about 10 to about 1000 microseconds), and
over a relatively wide range of peak voltages per pulse (e.g., from about 50 to
about 1000 volts). A maximum of 500 microcoulombs significantly reduces the risk
of fibrillation while a lower maximum (e.g., about 100 microcoulombs) is preferred
to conserve energy expenditure.
Pulse duration is preferably dictated by delivery of charge
as discussed above. Pulse duration according to various aspects of the present invention
is generally longer than conventional systems that use peak pulse voltages higher
than the ionization potential of air. Pulse duration may be in the range from about
20 to about 500 microseconds, preferably in the range from about 30 to about 200
microseconds, and most preferably in the range from about 30 to about 100 microseconds.
By conserving energy expenditure per pulse, longer durations
of immobilization may be effected and smaller, lighter power sources may be used
(e.g., in a projectile comprising a battery). In one implementation, a AAAA size
battery is included in a projectile to deliver about 1 watt of power during target
management which may extend to about 10 minutes. In such an embodiment, a suitable
range of charge per pulse may be from about 50 to about 150 microcoulombs.
Initial and termination voltages may be designed to deliver
the charge per pulse in a pulse having a duration in a range from about 30 microseconds
to about 210 microseconds (e.g., for about 50 to 100 microcoulombs). A discharge
duration sufficient to deliver a suitable charge per pulse depends in part on resistance
between electrodes at the target. For example, a one RC time constant discharge
of about 100 microseconds may correspond to a capacitance of about 1.75 microfarads
and a resistance of about 60 ohms. An initial voltage of 100 volts discharged to
50 volts may provide 87.5 microcoulombs from the 1.75 microfarad capacitor.
A termination voltage may be calculated to ensure delivery
of a predetermined charge. For example, an initial value may be observed corresponding
to the voltage across a capacitor. As the capacitor discharges delivering charge
into the target, the observed value may decrease. A termination value may be calculated
based on the initial value and the desired charge to be delivered per pulse. While
discharging, the value may be monitored. When the termination value is observed,
further discharging may be limited (or discontinued) in any conventional manner.
In an alternate implementation, delivered current is integrated to provide a measure
of charge delivered. The monitored measurement reaching a limit value may be used
to limit (or discontinue) further delivery of charge.
Pulse durations in alternate implementations may be considerably
longer than 100 microseconds, for example, up to 1000 microseconds. Longer pulse
durations increase a risk of cardiac fibrillation. In one implementation, consecutive
strike pulses alternate in polarity to dissipate charge which may collect in the
target to adversely affect the target's heart.
During the strike stage, pulses are delivered at a rate
of about 5 to about 50 pulses per second, preferably about 20 pulses per second.
The strike stage continues from the rising edge of the first pulse to the falling
edge of the last pulse of the stage for from 1 to 5 seconds, preferably about 2
In a hold stage, a voltage waveform is sourced and impressed
across a pair of electrodes. Typically this waveform is sufficient to discourage
mobility and/or continue immobilization to an extent somewhat less than the strike
stage. A hold stage generally demands less power than a strike stage. Use of hold
stages intermixed between strike stages permit the immobilization effect to continue
as a fixed power source is depleted (e.g., battery power) for a time longer than
if the strike stage were continued without hold stages. The stimulus signal of a
hold stage may primarily interfere with voluntary control of the target's skeletal
muscles as discussed above or primarily cause pain and/or disorientation. The pair
of electrodes may be the same or different than used in a preceding path formation,
path testing, or strike stage, preferably the same as an immediately preceding strike
stage. According to various aspects of the present invention, the shape of the waveform
used in a hold stage includes a pulse with decreasing amplitude (e.g., a trapezoid
shape) and initial voltage (SPV) as discussed above with reference to the strike
stage. The termination voltage may be determined to deliver a predetermined charge
per pulse less than the pulse used in the strike stage (e.g., from 30 to 100 microcoulombs).
During the hold stage, pulses may be delivered at a rate of about 5 to 15 pulses
per second, preferably about 10 pulses per second. The strike stage continues from
the rising edge of the first pulse to the falling edge of the last pulse of the
stage for from about 20 to about 40 seconds (e.g., about 28 seconds).
A rest stage is a stage intended to improve the personal
safety of the target and/or the operator of the system. In one implementation, the
rest stage does not include any stimulus signal. Consequently, use of a rest stage
conserves battery power in a manner similar to that discussed above with reference
to the hold stage. Safety of a target may be improved by reducing the likelihood
that the target enters a relatively high risk physical or emotional condition. High
risk physical conditions include risk of loss of involuntary muscle control (e.g.,
for circulation or respiration), risk of convulsions, spasms, or fits associated
with a nervous disorder (e.g., epilepsy, or narcotics overdose). High risk emotional
conditions include risk of irrational behavior such as behavior springing from a
fear of immediate death or suicidal behavior. Use of a rest stage may reduce a risk
of damage to the long term health of the target (e.g., minimize scar tissue formation
and/or unwarranted trauma). A rest stage may continue for from 1 to 5 seconds, preferably
In one implementation, a strike stage is followed by a
repeating series of alternating hold stages and rest stages.
In any of the deployed electrode configurations discussed
above, the stimulation signal may be switched between various electrodes so that
not all electrodes are active at any particular time. Accordingly, a method for
applying a stimulus signal to a plurality of electrodes includes, in any order:
(a) selecting a pair of electrodes; (b) applying the stimulus signal to the selected
pair; (c) monitoring the energy (or charge) delivered into the target; (d) if the
delivered energy (or charge) is less than a limit, conclude that at least one of
the selected electrodes is not sufficiently coupled to the target to form a stimulus
signal delivery circuit; and (e) repeating the selecting, applying, and monitoring
until a predetermined total stimulus (energy and/or charge) is delivered. A microprocessor
performing such a method may identify suitable electrodes in less than a millisecond
such that the time to select the electrodes is not perceived by the target.
A waveform generator, according to various aspects of the
present invention may perform a method for delivering a stimulus signal that includes
selecting a path, preparing the path for the stimulus signal, and repeatedly providing
the stimulus signal for a sequence of effects including in any order: a comparatively
highly immobilizing effect (e.g., a strike stage as discussed above), a comparatively
lower immobilizing effect (e.g., a hold stage as discussed above), and a comparatively
lowest immobilizing effect (e.g., a rest stage as discussed above). For example,
method 400 of FIG. 4 is implemented as instructions stored in a memory device (e.g.,
stored and/or conveyed by any conventional disk media and/or semiconductor circuit)
and installed to be performed by a processor (e.g., in read only memory of processor
Method 400 begins with a path testing stage as discussed
above comprising a loop (402-408) for determining an acceptable or preferred electrode
pair. Because the projectile may include numerous electrodes, any subset of electrodes
may be selected for application of a stimulus signal. Data stored in a memory accessible
to the processor of circuit 220 may include a list of electrode subsets (e.g., pairs),
preferably an ordered list from most preferred for maximum immobilization effect
to least preferred. In one implementation, the ordered list indicates one preference
for one subset of electrodes to be used in all stages discussed above. In another
implementation, the list is ordered to convey a preference for a respective electrode
subset for each of more than one stage. Method 400 uses one list to express suitable
electrode preferences. Alternate implementations include more than one list and/or
more than one loop (402-408) (e.g., a list and/or loop for each stage). In another
alternate implementation a list includes duplicate entries of the same subset so
that the subset is tested before and after intervening test or stimulus signals.
According to method 400, after path management, processor
220 performs target management. Path management may include path formation, as discussed
above. Target management may be interrupted to perform path management as discussed
below (434). For target management, processor 220 provides the stimulus signal in
a sequence of stages as discussed above. In one implementation a sequence of stages
is effected by performing a loop (424-444).
For each (424) stage of a predefined stage sequence, a
loop (426-442) is performed to provide a suitable stimulus signal. Prior to entry
of the inner loop (426-442), a stage is identified. The stage sequence may include
one strike stage, followed by alternating hold and rest stages as discussed above.
For the duration of the identified stage (426), processor
220 charges capacitors (428) (e.g., C12 used for signal VP) until charge sufficient
for delivery (e.g., 100 microcoulombs) is available or charging is interrupted by
a demand to provide a pulse (e.g., operator command via transceiver 240, a result
of electrode testing, or lapse of a timer). Processor 220 then forms a pulse (e.g.,
a strike stage pulse or hold stage pulse) at the value of SPV set as discussed above
(422 or 414). Processor 220 meters delivery of charge (432), in one implementation,
by observing the voltage (e.g., VC) of the storage capacitors decrease (436) until
such voltage is at or beyond a limit voltage (e.g., about 228 volts). The selection
of a suitable limit voltage may follow the well known relationship: &Dgr;Q = C&Dgr;V
where Q is charge in coulombs; C is capacitance in farads; and V is voltage across
the capacitor in volts.
During metering of charge delivery, processor 220 may detect
(434) that the path in use for the identified stage has failed. On failure, processor
220 quits the identified stage, quits the identified stage sequence, and returns
(402) to path testing as discussed above.
When the quantity of charge suitable for the identified
stage has been delivered (436), the pulse (e.g., signal VP) is ended (440). The
voltage supplied after the pulse is ended may be zero (e.g., open circuit at least
one of the identified electrodes) or a nominal voltage (e.g., sufficient to maintain
If the identified stage is not complete, then processing
continues at the top of the inner loop (426). The identified stage may not be complete
when a duration of the stage has not lapsed; or a predetermined quantity of pulses
has not been delivered. Otherwise, processor 220 identifies (444) the next stage
in the sequence of stages and processing continues in the outer loop (424). The
outer loop may repeat a stage sequence (as shown) until the power source for waveform
generator is fully depleted.
For each (402) listed electrode subset, processor 220 applies
(404) a test voltage across an identified electrode subset. In one implementation,
processor 220 applies a comparatively low test voltage (e.g., about 500 volts) to
determine an impedance of the stimulus signal delivery circuit that includes the
identified electrodes. Impedance may be determined by evaluating current, charge,
or voltage. For instance, processor 220 may observe a change in voltage of a signal
(e.g., VC) corresponding to the voltage across the a capacitor (e.g., C12) used
to supply the test voltage. If observed change in voltage (e.g., peak or average
absolute value) exceeds a limit, the identified electrodes are deemed suitable and
the stimulus peak voltage is set to 450 volts. Otherwise, if not at the end of the
list, another subset is identified (408) and the loop continues (402).
In another implementation, processor 220 applies a comparatively
low test voltage (e.g., about 500 volts) with delivery of a suitable charge (e.g.,
from about 20 to about 50 microcoulombs) to attract movement of the target toward
an electrode. For example, movement may result in impaling the target's hand on
a rear facing electrode thereby establishing a preferred circuit through a relatively
long path through the target's tissue. In one implementation, the rear facing electrode
is close in proximity to electrodes of the subset and is also a member of the subset.
Alternatively, the rear facing electrode may be relatively distant from other electrodes
of the set and/or not a member of the subset.
The test signal used in one implementation has a pulse
amplitude and a pulse width within the ranges used for stimulus signals discussed
herein. One or more pulses constitute a test of one subset. In alternate implementations,
the test signal is continuously applied during the test of a subset and test duration
for each subset corresponds to the pulse width within the range used for stimulus
signals discussed herein.
If at the end of the list no pair is found acceptable,
processor 220 identifies a pair of electrodes for a path formation stage as discussed
above. Processor 220 applies (412) an ionization voltage to the electrodes in any
conventional manner. Presuming ionization occurred, subsequent strike stages and
hold stages may use a stimulus peak voltage to maintain ionization. Consequently,
SPV is set (414) to 3 Kvolts.
The foregoing description discusses preferred embodiments
of the present invention which may be changed or modified without departing from
the scope of the present invention as defined in the claims. While for the sake
of clarity of description, several specific embodiments of the invention have been
described, the scope of the invention is intended to be measured by the claims as
set forth below.