Abstract:
Haptic feedback system that simulates a detonation or explosive event. The system includes a power supply, an energy storage circuit, a switching circuit, and a conductor operatively connected to said energy storage circuit through said switching circuit whereby said conductor causes a haptic event when said energy storage circuit is electrically connected to said conductor by operation of said switching circuit. The system creates real explosions, shock waves and pressure waves in a safe manner for use in a simulator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/052,652, filed Sep. 19, 2014. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    1. Field of Invention 
         [0004]    This invention pertains to a haptic feedback device for a simulator. More particularly, this invention pertains to devices for simulating detonation or explosive events. 
         [0005]    2. Description of the Related Art 
         [0006]    Haptic communication recreates the sense of touch by applying forces, vibrations, or motions to the user, for example in a virtual reality system or computer simulation. An early example is the video game Moto-Cross, where the handlebar controllers would vibrate during a collision with another vehicle. Other examples include force feedback for remote controlled robotic tools, to feel what the robot arm is “feeling”; steering wheels in virtual reality that resist turns or slip out of control during a turn; smart phone vibration in response to touch; and force magnitude and body orientation in a flight simulator. 
         [0007]    Realistic explosions are desired in many virtual reality simulators and video games, for example, in military and rescue virtual reality training. The embodiments herein disclose safe, controlled, and realistic haptic feedback in the form of explosions, soundwaves, and shockwaves. 
       BRIEF SUMMARY 
       [0008]    According to one embodiment of the present invention, a haptic generator system is provided. The haptic generator system includes a power supply, a controller, an energy storage unit, and a conductor in a driver or containment tube having a nozzle. In one such embodiment the conductor is an electro-exploding wire (EEW) array of one or more wires. 
         [0009]    The power supply provides power for the haptic generator system and also charges the energy storage unit. The controller provides control functions for the system, including switching the capacitors in the energy storage unit to be in electrical connection with the electro-exploding wire. The energy storage unit includes one or more capacitors that are charged by the power supply. The energy storage unit also includes a switching network that connects the capacitors to the electro-exploding wire. The electro-exploding wire is a replaceable conductor that vaporizes upon application of sufficient energy. In one embodiment the wire is a single conductor. In another embodiment the wire includes multiple, independent conductors forming an array, such as for producing a rapid series of explosive events. In various embodiments the wire is carbon, nichrome, copper, aluminum, water, or other metal or conductive material. The driver is a cylindrical housing with the electro-exploding wire oriented axially at one end and with a focused air blast nozzle at the opposite end. 
         [0010]    The energy storage unit includes one or more capacitors that are charged by the power supply. After charging the capacitors, the haptic generator system is triggerable to fire at various haptic effect power levels with no or minimal delay. Multiple switches are closed in various ways to change the number of capacitors fired in series into the output. This in turn provides options in the energy delivered to the haptic generation head. Changing the charge voltage scales these selectable haptic levels together, but that adjustment requires time to charge or discharge the energy storage capacitors to the new voltage level before firing. The controller operates the various switches that interconnect the capacitors to provide a desired voltage and current output of the energy storage unit. In one embodiment the energy storage unit includes sets of capacitors where one set is being charged while another set is delivering energy to the electro-exploding wire. 
         [0011]    The energy storage unit provides energy to the conductor in order to create an explosive event. For the embodiment with the conductor being an electro-exploding wire, during the explosive event the electro-exploding wire is converted to plasma. The explosive event generates a shockwave and a pressure wave that simulates the visual, audio, and tactile response of a range of explosive detonations. The shockwave generated by the explosive event has spatial and temporal characteristics determined by the current pulse applied to the electro-exploding wire. Accordingly, the shockwave is tailored by the controller and energy storage unit to match a desired signature of an explosive device at desired stand-off distances. 
         [0012]    The conversion to plasma of the electro-exploding wire array minimizes any shrapnel or environmental contaminants from the explosive event. The system does not harm the simulation facility and leaves minimal trace of its operation. In one embodiment the driver includes a screen-type shield of conductive material. The shield covers the opening of the nozzle and serves two purposes. First, the shield prevents inadvertent operator contact with potentially energized components inside the driver. Second, the shield is grounded and forms one wall of a Faraday cage to attenuate electromagnetic interference while still allowing the shock and pressure waves to propagate through the shield. 
         [0013]    In one embodiment, the haptic generator system includes a power supply, an energy storage circuit, a switching circuit, and a wire operatively connected to said energy storage circuit through said switching circuit whereby said wire converts to plasma when said energy storage circuit is electrically connected to said wire by operation of said switching circuit. In one such embodiment the haptic generator system further includes a housing with a central bore and a nozzle positioned at one end of the housing, the wire positioned at one end of the central bore that is opposite the nozzle. In one embodiment the haptic generator system further includes a vortex generator. In one embodiment the electro-exploding wire is automatically replaceable from a spool. In one such embodiment the electro-exploding wire is suspended between a terminal end and a feed tube, the terminal end is supported inside the central bore and the feed tube is at the base of bore, in this way the wire is oriented axially with the central bore. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0014]    The above-mentioned features will become more clearly understood from the following detailed description read together with the drawings in which: 
           [0015]      FIG. 1  is a functional block diagram of one embodiment of a haptic generator system. 
           [0016]      FIG. 2  is a perspective view of one embodiment of a containment tube. 
           [0017]      FIG. 3  is a cross-sectional view of a containment tube showing one embodiment of a electro-exploding wire assembly. 
           [0018]      FIG. 4  is a front view of one embodiment of a nozzle end of the containment tube. 
           [0019]      FIG. 5  is a symbolic view of one embodiment of an automatic electro-explosive wire feed assembly. 
           [0020]      FIG. 6  is a flow diagram of one embodiment of the operation of the automatic electro-explosive wire feed assembly. 
           [0021]      FIG. 7  is a simplified schematic diagram of the haptic generator system. 
           [0022]      FIG. 8  is a front view of a second embodiment of a nozzle end of the containment tube. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Apparatus for a haptic generator system  100  is disclosed. The haptic generator system is generally indicated as  100 , with particular embodiments and variations shown in the figures and described below having an alphabetic suffix, for example,  100 -A. 
         [0024]      FIG. 1  illustrates a functional block diagram of one embodiment of a haptic generator system  100 . The system  100  includes a power supply  102 , a controller  104 , an energy storage unit  106 , and a conductor embodied here as an electro-exploding wire (EEW) assembly  108  that is coupled to a containment tube  110  having a nozzle  112 . The electro-exploding wire assembly  108  causes an explosive event  114  when it is energized by the energy storage unit  106 . The explosive event  114  includes both a shockwave and a pressure wave that emanates from the nozzle  112 . 
         [0025]    In other embodiments, the conductor  108  is a stream of liquid that causes an explosive event  114  when energy from the energy storage unit  106  is applied to the stream. The feed tube  306  for the liquid is a nozzle that produces the liquid stream, where the conductor feed system  500  includes a device for propelling the stream, for example, a diaphragm pump. In other embodiments, the conductor  108  is other material responsive to an electrical charge or current, including other conductive or semi-conductive material. 
         [0026]    The power supply  102  provides power for the system  100  and, in particular, the energy storage unit  106 . The controller  104  is operatively connected to the energy storage unit  106 , which is electrically connected to the electro-exploding wire assembly  108 . 
         [0027]    The explosive event  114  includes both a shockwave and a pressure wave that emanates from the nozzle  112 . The shockwave and the pressure wave provide audible and physical stimuli, and the plasma flash provides a visual stimulus. For example, the pressure wave provides physical stimulus, such as with the pressure wave interacting with an observer or with the physical environment of the simulator. In this way haptic feedback is provided. The containment tube  110  and nozzle  112  focuses and shapes the emanated pressure wave from the explosive event  114  to form a focused air blast. In one embodiment the containment tube and the electro-exploding wire assembly  108  are configured as a vortex generator. 
         [0028]      FIG. 2  illustrates a perspective view of one embodiment of a containment tube  110  with a nozzle  112 .  FIG. 3  illustrates a cross-sectional view of a containment tube  110  showing one embodiment of a electro-exploding wire assembly  108 .  FIG. 4  illustrates a front view of one embodiment of a nozzle end  112  of the containment tube  110 . 
         [0029]    The containment tube  110  is cylindrical with the electro-exploding wire assembly  108  at one end and the nozzle  112  at the opposite end. A central opening  204  at the nozzle  112  end extends into the cylindrical body  202  of the containment tube  110  with a cylindrical sidewall  302 . In one embodiment the body  202  of the containment tube  110  includes a surrounding chamber  316  that provides cooling for the generator  110  after an explosive event  114 . In one such embodiment the chamber  316  circulates a fluid, such as air, water, or other media suitable for heat transfer. In another such embodiment, the chamber  316  includes openings in sidewall  302  such that a negative air pressure in the chamber  316  draws particulate byproducts from an explosive event  114  out of the containment tube  110 , thereby preventing contamination and/or soiling of the environment. 
         [0030]    The electro-exploding wire assembly  108  includes terminal end  304 , a pair of struts  308 , a length of electro-exploding wire  312 , and a feed tube  306 . The struts  308  support the terminal end  304  centrally in body  202  of the containment tube  110 . The illustrated embodiment shows a pair of struts  308  extending in opposed relationship to support the terminal end  304 . In other embodiments the number of struts  308  varies. In each embodiment the number of struts  308  is sufficient to support the terminal end  304  during an explosive event  114 . 
         [0031]    The terminal end  304  is cylindrical and axially oriented with respect to the bore  204  in the body  202 . The terminal end  304  has a cylindrical bore  318  parallel with the outer cylindrical surface of the terminal end  304 . The cylindrical bore  318  is a blind bore that has an inside end that is conical. In the illustrated embodiment the terminal end  304  includes a series of openings  310  between the outer cylindrical surface and the cylindrical bore  318 . Those skilled in the art will recognize that the terminal end  304  has a configuration that aids in receiving the wire  312  without unduly restricting the plasma from an explosive event. The electro-exploding wire  312  extends into the cylindrical bore and is seated against the inside point of the conical end, thereby making an electrical connection between the terminal end  304  and the electro-exploding wire  312 . In one embodiment at least one of the struts  308  is conductive and provides an electrical pathway to connect to the electro-exploding wire  312  where it contacts the inside point of the conical end. 
         [0032]    The terminal end  304  also includes a series of openings in the cylindrical sidewalls. These openings are configured to allow the expanding plasma from the electro-exploding wire  312  to escape the terminal end  302  in a manner that allows the plasma to form a shockwave in a predetermined form and direction. 
         [0033]    Extending from the inside end  314  of the body  202  is a feed tube  306  with the electro-exploding wire  312  extending from the feed tube  306  into the terminal end  304 . The wire  312  extends axially relative to the sidewalls  302  from the feed tube  306  to the terminal end  304 . 
         [0034]    Opposite the electro-exploding wire assembly  108  is the nozzle  112 . In the illustrated embodiment the nozzle  112  is a focused air blast nozzle. The nozzle  112  focuses the sound pressure wave to a smaller area compared to the containment tube  110  without the nozzle  112 . The nozzle  112  has an outer surface  206  that is arcuate and functions to isolate and separate the emitted pressure wave from the ambient air. 
         [0035]      FIG. 5  illustrates a symbolic view of one embodiment of a conductor feed system  500 , which is illustrated as an automatic electro-explosive wire feed assembly  500 . In one embodiment the haptic generator system  100  is a one-shot device. In such an embodiment the electro-exploding wire  312  must be manually replaced after each explosive event  114 . In the illustrated embodiment the haptic generator system  100  is a multi-shot device, that is, the electro-exploding wire  312  is automatically replaced after each explosive event  114  without requiring operator intervention. 
         [0036]    In the illustrated embodiment of the automatic electro-explosive wire feed assembly  500  a spool  502  provides a supply of electro-explosive wire  312 . The wire  312  is routed through idler wheels  504  to the wire drive  510 . The wire drive  510  includes a capstan that pulls the wire  312  from the spool  502  and forces it through straightening mechanism  506  which in this embodiment comprises a series of straightening wheels  508 . After the wire  312  is straightened it is fed through the feed tube  306  where the wire  312  is forced into the terminal end  304 . In other embodiments the configuration of the spool  502 , idler wheels  504 , wire drive  510 , and straightening mechanism  506  varies. For example, in a different embodiment the wire drive  510  and corresponding idler wheels  504  are located subsequent to the straightening mechanism  506  and thus the wire drive  510  pulls the wire  312  through the straightening mechanism  506 . The wire  312  passing through the feed tube  306  is sufficiently straight that it is readily feed into the terminal end  304 . 
         [0037]    The electro-exploding wire  312  is an electrical circuit element. With the application of sufficient voltage and current from the energy storage unit  106  the electro-exploding wire  312  will vaporize. The portion of the wire between the terminal end  304  and the feed tube  306  is the portion desired to be volatized for an explosive event  114 . Accordingly, the energy storage device electrically connects to the wire  312  through the terminal end  304  and the feed tube  306 . In one embodiment the outboard tip  512  (relative to the inside end  314  of the body  202 ) of the feed tube  306  is conductive and it is the tip  512  that makes electrical contact with the wire  312 . Also illustrated in  FIG. 5  is another embodiment of an electrode  512 ′ positioned adjacent the outboard tip  512  of the feed tube  306 , The end of the electrode  512 ′ is separated from the wire  312  by a spark gap  514 . Upon being energized, a spark completes the circuit between the electrode  512 ′ and the wire  312 , thereby allowing the wire  312  to vaporize between the spark gap  514  and the terminal end  304 . In this way the portion of the wire  312  that vaporizes is external to the feed tube  306 , thereby ensuring that the wire  312  remains free to pass through the feed tube  306  without being fused to the feed tube  306 . 
         [0038]    In another embodiment, the conductor feed system  500  replenishes the stream of liquid used as the conductor  108 . In such an embodiment the feed tube  306  is a nozzle that directs a stream of liquid to the terminal end  304 . The feed system  500  includes a device, such as a pump, for forcing the liquid through the nozzle  306 . The liquid is forced through the nozzle  306  immediately before the controller  104  initiates application of energy to the stream of liquid. In another embodiment, the stream of liquid is continuous while the system is running and the feed system  500  does not change liquid output based on whether the controller  104  is about to initiate application of energy to the stream of liquid. 
         [0039]      FIG. 6  illustrates a flow diagram of one embodiment of the operation of the automatic electro-explosive wire feed assembly  500 . The EEW feed assembly  500  operates continuously after it starts  602 . The assembly  500  includes a sensor that detects if the electro-explosive wire  312  is fully extended. The first step  604  is to determine if the electro-explosive wire  312  is fully extended. If it is not fully extended, then the next step  606  is to drive the motor assembly  510  to advance the wire  312 . The position is checked again  604  and the steps  604 ,  606  repeat until the wire  312  is fully extended. If the electro-explosive wire  312  is fully extended, then the next step  608  is to wait until there is an explosive event. Such an event requires that the wire  312  be advanced such that it fully extends again. 
         [0040]      FIG. 7  illustrates a simplified schematic diagram of the haptic generator system  100 . The power supply  102  is fed from a power source  702 , such as the mains or a battery. 
         [0041]    The energy storage unit  106  includes an energy storage circuit and a switching circuit. In the illustrated embodiment the energy storage circuit includes a capacitor  704  and the switching circuit includes a switch  706 . In other embodiments the energy storage unit  106  includes multiple capacitors  704  and/or switches  706 . The controller  104  is operatively connected to the switches  706  in the energy storage unit  106 . 
         [0042]    The power supply  102  provides power to charge the energy storage unit  106 . The power supply  102  includes a high voltage supply that, for example, operates between 1 to 2 kV dc and charges the capacitor  704 . In one embodiment the power supply  102  is current limited such as with a resistor in series with the capacitor  704 . In this way the capacity of the power supply  704  will not be exceeded. 
         [0043]    The illustrated energy storage unit  106  has a capacitor  704  of 400 μF. The power supply  102  charges the capacitor  704  up to 2 kV (800 J). The energy storage unit  106  has a switch  706  rated to make a connection that carries such high energy. In one embodiment the switch  706  is a thyratron switch. In another embodiment the switch  706  is a high energy relay. Such a switch  706  has a high speed of operation in order to minimize pre-contact arcing. The switch  706  is also rated to carry the energies used to cause the electro-exploding wire  312  to vaporize. 
         [0044]    The electro-exploding wire  312  is a conducting element that vaporizes when exposed to high current. In various embodiments the wire  312  is made of carbon, nichrome, copper, aluminum, doped water, or other metal or conductive material. A wire  312  made of carbon forms carbon dioxide after an explosive event  114 . 
         [0045]    In one embodiment the electro-exploding wire  312  is a thin metal wire with 286 μm diameter. In such an embodiment the capacitor  704  with a 2 kV charge applies approximately 10 kA within about 100 microseconds and the resulting explosive event  114  generates a pressure wave with overpressures on the order of 1 psi (6.9 kPa). Increasing the voltage applied to the wire  312  in this embodiment increases the sound pressure level of the explosive event  114 . 
         [0046]    The electro-explosive wire  312  generates an explosive event  114  with results similar to the detonation of high explosives. The resistive heating of the wire  312  vaporizes the wire  312  and generates plasma that is then expanded by the driving current. The expanding plasma cloud compresses the surrounded gas and generates a shockwave that propagates faster than the plasma itself. The expanding plasma cools quickly once the stored energy dissipates. The surrounding air aids in the cooling process and reacts with the metal vapor in the plasma to form non-conductive particulates, such as aluminum oxide for an aluminum wire  312 . These particulates, in one embodiment, are drawn from the bore  204  and filtered, thereby preventing any soiling or contamination of the surrounding environment. 
         [0047]      FIG. 7  illustrates a simplified schematic of one embodiment of a haptic generator system  100 . The simplified schematic does not illustrate various components and connections, for example, power and ground connections to the various components and a discharge resistor to remove the residual charge on the capacitor  704 . However, those skilled in the art will recognize the need for such components and wiring and understand how to construct such a circuit, based on the components ultimately selected for use. 
         [0048]      FIG. 8  illustrates another embodiment front view of a nozzle end  112 ′ with a conductive shielding  802  placed between the nozzle central opening  204  and terminal end  306 . The body  202 ′ contains sufficient conductive material such that the conductive shielding  802  is grounded to the body  202 ′ to create a Faraday cage that prevents outside EMF interference with the containment tube  108  and nozzle  112 . The shielding  802  also acts as a safety screen to prevent users from inadvertently coming into contact with high voltages and currents. 
         [0049]    While the present invention has been illustrated by embodiments that have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.