Device, method and system for extending range and improving tracking precision of mortar rounds

A system, device and method provide a glide kit that can attach to a conventional mortar round to create a glide-enabled round. The glide-enabled round can fit within a mortar tube. When the munition exits the mortar tube, it sequentially deploys wings and canards to initiate the glide maneuver and increase the mortar range. A state estimator subsystem can be employed with a canard control subsystem to actively guide the mortar to a fixed location. The combination of the estimator and canard control subsystems improves the tracking precision of the mortar round.

TECHNICAL FIELD

The present disclosure pertains to mortar rounds, and more particularly, to a mortar augmentation system, device and method that extends range, reduces impact dispersion and approximates the range and deflection of a mortar round.

BACKGROUND AND SUMMARY

Conventional mortar rounds, such as the M934 mortar round, are limited in their range, generally have a broad impact dispersion and are subject to a wide circular error probable (CEP). CEP is the radius of a circle within which fifty percent of the rounds would land corresponding to perturbations in launch conditions, winds, and other factors.

Embodiments of the present disclosure provide a mortar augmentation system, which can include an add-on glide kit for an existing mortar round, a state estimator subsystem to approximate the mortar range and deflection and a canard control subsystem to actively guide the mortar to a fixed location. According to embodiments described herein, the glide kit does not replace whole sections of the mortar round but is rather an add-on kit that enhances range and reduces impact dispersion. In various embodiments, the precision control comprises a mechanical articulation combined with a software algorithm as described herein.

The glide kit can be employed with various sizes of rounds, including 120 mm, 81 mm and 60 mm mortar rounds. In various embodiments, the glide kit consists of flight surfaces that attach to the front and rear of a standard mortar round. The flight surfaces are adapted to fold-up against the body of the mortar round in order to fit within a mortar launch tube. After launching from the mortar tube, the flight surfaces deploy to provide aerodynamic glide capability to the mortar. The aerodynamic glide capability can increase the nominal range of a 120 mm mortar, for example, by approximately forty percent.

In various embodiments, the flight surfaces consist of front flight surfaces referenced as canards herein and rear flight surfaces referenced as wings herein. The canards and wings attach to the mortar round using distinct housings, which may be formed of metal, for example. The front or canard housing contains the deployable canards. The rear or wing housing contains the deployable wings. In various embodiments, the canard housing is secured around the front of the round just behind the fuse location and the wing housing is secured around the tail fin assembly.

In some embodiments, the wing housing includes springs to deploy the wings, and a ratchet-style spring tab to hold the deployed wings in place. When the wings are stowed, i.e., folded against the mortar body, a cord such as an Aramid cord, for example, can be wrapped around the wings to prevent them from unfolding. During the launch from the mortar tube, the heat from the igniting charges disintegrates the cord. This allows the wings to deploy once the round exits the mortar tube. Initially, only the wings deploy and the mortar round climbs to its maximum altitude. At the peak altitude, the canards can be deployed such as by an electrical circuit, for example.

In certain embodiments, the canard housing can include springs to deploy the canards and a ratchet-style spring tab to hold the deployed canards in place. When the canards are stowed, i.e., folded against the mortar body, a cord can be wrapped around them to prevent them from unfolding. The cord can be fastened using Nichrome resistance heating wire, for example. The canards can be deployed by electrically connecting a battery to the Nichrome wire, whereby, once the battery is connected to the wire, the wire disintegrates, allowing the canards to deploy.

In certain embodiments, a restraint cord such as a Vectran cord can wrap around each of the canards to prevent them from unfolding. The Nichrome wire can be wrapped around the Vectran restraint cord. When the battery is connected to the Nichrome wire, it heats up and cuts through the restraint cord, allowing the canards to deploy.

In various embodiments, the canard housing includes a circuit board to time the deployment of the canards based on the measured shock load, for example. The circuit board can measure the launch shock using an onboard shock sensor. This initiates a timer onboard a microprocessor or controller. Once a determined amount of time has passed, the controller uses a switch to electrically connect a battery to the Nichrome wire. The current from the battery connection heats the Nichrome wire so that it burns through the restraint cord. The cord releases, and the canards spring-deploy to unfold from the body. The ratchet-style spring tab holds the canards in their deployed configuration. When the canards deploy, they cause the gliding mortar round to pitch upward into an optimal flight angle for maximum range glide performance.

In various embodiments, additional circuitry and actuators are provided to make small changes in the canard sweep angle to achieve precision control. For example, the canard housing can include an accelerometer and a barometric pressure sensor. Based on measurements received from the accelerometer and barometric pressure sensor, the on-board controller can determine a launch angle and barrel speed of the mortar round. The controller can further determine a charge weight for the mortar round based on the barrel speed, a desired impact point based on the launch angle and charge weight, and a position and velocity of the mortar round based on the launch angle and barrel speed. Based on the determined position and velocity, the controller can determine a projected impact point for the mortar round. By understanding the desired impact point and the projected impact point, the controller can adjust the canard rotation angle to a position between the fully undeployed position and the fully deployed position so as to more accurately control the mortar round and reduce impact dispersion, for example.

In various embodiments, small rigid wing segments or passive fin connector vanes are secured between the existing mortar fins. These “fin-vanes” provide additional stabilization during the initial mortar launch and also help to improve the aerodynamic glide performance.

The state estimator subsystem according to the present disclosure can approximate the mortar range and deflection without using GPS, according to various embodiments. The range and deflection estimates can be integrated into the canard control system of the present disclosure to actively guide the mortar to a fixed location.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments such as disclosed herein can incorporate a controller having a processor and an associated memory storing instructions that, when executed by the processor, cause the processor to perform operations as described herein. It will be appreciated that reference to “a”, “an” or other indefinite article in the present disclosure encompasses one or more than one of the described element. Thus, for example, reference to a controller encompasses one or more controllers, reference to a measurement encompasses one or more measurements, reference to a canard or wing encompasses one or more canards or wings and so forth.

FIG.1shows a munition12according to the present disclosure in its stowed10and deployed15configurations. A mortar round body20is stowed in a mortar tube22with an attached glide kit having wings24secured to a tail fin assembly42of the munition12and canards26secured around or to a nose28of the munition12. After the glide munition12exits the mortar tube22, it sequentially deploys wings24and canards26to initiate the glide maneuver and increase the mortar range. Embodiments of the glide-kit include pop-out wings and canards and employ shape memory alloy (SMA) technology as described elsewhere herein to deploy, lock, and control the flight surfaces.

FIG.2is an exemplary graph30that compares the range of a munition with the glide kit of the present disclosure attached and without a glide kit under identical launch conditions. As can be seen, the range32of a munition with glide kit attached is much further than the range34of a munition without the glide kit of the present disclosure attached. For example, the mortar round range34without glide kit is shown as 7.1 km and the mortar round range32with glide kit is shown as 10.1 km inFIG.2. In various embodiments as described herein, the canards26are deployed at the peak altitude33of the munition12after launch.

As shown inFIGS.3A through23, embodiments of the present device provide variations of glide kits38. Certain variations of glide kits as disclosed herein provide only range extension. In such variations, the canards26fully deploy one-time and lock in-place for the remainder of the glide maneuver. There are reduced sensor and active control requirements and corresponding lower cost associated with such a design. Other variations of glide kits as disclosed herein have adjustable canards26which achieve both range increase and CEP decrease (i.e., range extension with greater precision control). Such variations combine a state estimator subsystem and canard control subsystem with active canard sweep control as disclosed herein to guide the mortar round out to a desired impact distance regardless of the launch perturbations or atmospheric conditions.

As can be seen from the drawings, embodiments of the glide kit38include separate front50and rear40modules. The front module50incorporates deployable canards26. As described above with reference toFIGS.1and2, the canards26can be deployed at the peak altitude33after launch. In various embodiments, the front module50can contain batteries, sensor hardware, and a deployment system to actuate and lock the canard rotation. The front module50can further contain SMA wire to actuate and lock the canard rotation. In various embodiments, the front module50mounts behind the mortar round fuse51and wraps around the mortar body20such as by interference or friction fit to secure in-place. The rear module40contains deployable wings24. In various embodiments, the wings24deploy and lock-in place immediately after launch. Embodiments of the rear module40can be provided as purely mechanical with no sensors or power system in accordance with the present disclosure.

FIGS.3A through3Dshow how the munition12according to the present disclosure changes configuration during operation. When being loaded into the launch tube22and prior to launch, which is illustrated schematically at10inFIG.1, the flight surfaces are initially stowed, i.e., the wings24and canards26are in the undeployed position as shown inFIG.3A. After barrel exit, which is illustrated schematically at15inFIG.1, the wings24deploy to stabilize the ballistic ascent and the canards26remain stowed as shown inFIG.3B. The deployed wings26provide both pitch stability and roll stability during the initial ascent. At the trajectory peak, illustrated at33inFIG.1, the canards26are deployed into flight configuration to initiate the glide maneuver as shown inFIG.3C. The canards26increase the glide-range and the munition12executes a gliding descent until ground impact. Deploying the canards26causes the equilibrium angle-of-attack to increase which generates greater lift. The munition12with deployed flight surfaces24,26is statically and dynamically stable and requires no active control to maintain its flight trajectory.

During the gliding descent, the canard sweep angle can be actively controlled to control the munition's pitch attitude and corresponding glide range. This is illustrated inFIG.3D, where the canards26are at a position between undeployed (as inFIG.3B) and fully deployed (as inFIG.3C). Varying the canard sweep angle and/or level of deployment assists in decreasing downrange dispersion. The CEP can be reduced by targeting a fixed impact distance that corresponds to the charge weight and launch angle. It will be appreciated that the port and starboard canard sweep angles can be varied independently and asymmetrically to control the munition's bank attitude and the corresponding deflection (i.e., lateral error in the landing point), as described elsewhere herein. It will further be appreciated that the front50and rear40modules are provided so as not to exceed the widest diameter D of the munition without the glide kit attached. For example, as shown inFIG.3A, the tail fin assembly42and the mortar body20can be provided with a diameter D that fits with desired tolerance within a launch tube22for proper launch operation. The front50and rear40modules do not exceed the diameter D when the canards26and wings24are undeployed so as to avoid impeding loading and launch operations. Further, given the shape of the mortar body20, the outer edges124of the wings24face the outer edges126of the canards26when in the undeployed position as there is greater lateral space for the wing housing41and canard housing52in the areas nearer the axial ends of the mortar round.

As shown inFIGS.4through9, the rear module40includes a wing housing41and wings24. The wing housing41includes a wing base ring44secured to wing guides45, wherein each wing guide45is formed with radially outer slots43extending radially outwardly from the mortar body20when secured and axially outer slots46extending in a direction axially aligned with the mortar body20when secured. The slots43,46permit proper wing rotation during operation. In various embodiments, the wing base ring44is formed by joining a first ring piece47to a second ring piece48. The ring pieces47,48may optionally be joined together with a suitable snap49or other mechanical attachment. In various embodiments, the wing base ring44clamps around the mortar tube20at the cylindrical section just aft of the tapered section27and just ahead of the ignition holes140. Additionally, one or more holes146can optionally be formed in the wing base ring44and a pin147can be pressed through the wing base ring144and into the tail shaft148to secure the wing housing41to the shaft148during the high-G launch. Embodiments of the wing surfaces consist of GOE389 flat-bottomed airfoils. In various embodiments, the wing platform is tapered as at144to fit alongside the curvature of the munition body20when in the undeployed position. Each wing can be secured to a relatively flat, cylindrical rotation mount29that rests and is pivotally secured within its respective wing guide45. For example, rotation mount29can be provided with a flange mount141for engaging a rod142(not shown) to permit wing24to rotate within the wing guide45. In various embodiments, the wings24are initially restrained by rope145such as Aramid rope.

In various embodiments such as shown inFIG.8, for example, the wing housing41orients the wing mounts29at a dihedral angle A, measured relative to the horizontal plane P of the mortar body. Therefore, the wings deploy with an initial dihedral angle. Dihedral is used on gliders to maintain an upright wing orientation without requiring active roll control. In various embodiments, the dihedral angle A can be ten degrees. In other embodiments the dihedral angle A can be as low as zero degrees and as high as forty-five degrees.

When the munition12is disturbed from the upright roll orientation, the lift builds up on one side of the wing more than the other. This creates a restoring moment which return the wings to the upright orientation. By deploying the wings24just after tube exit with built-in dihedral, the enhanced munition12according to the present disclosure will settle at a wings-up orientation during the initial ascent even with wind perturbations. The dihedral will cause the munition12to maintain the wings-up orientation during the gliding descent. This provides passive roll stability without high bandwidth actuators to maintain the desired roll orientation.

Wing rotation can be accomplished in various ways. For example, the wing guides45can contain a torsion spring to initiate the wing deployment and a ratchet mechanism to prevent bounce-back. The torsion spring can be mounted below the wing and initiate the unfolding. As the wing unfolds, the ratchet pushes the pawl out of the way, depressing the compression spring. At each increment of the deployment, the compression spring can push the pawl in to mate with the ratchet gear. The shape of the pawl and mating ratchet tooth can prevent the ratchet from pushing the pawl forward. During the deployment, as each ratchet gear tooth passes over the pawl, the wing is prevented from moving in the reverse direction. The one-way wing deployment locks in the final position when the wing contacts the back of the wing housing. The ratchet approach can be simplified to a single spring tab that deploys after the wing rotates and locks the wing in the final, fully extended position. As shown inFIG.23, the spring tab lock,194, is essentially a single-tooth ratchet that engages a slot in the canard,26, to lock it into the fully-extended configuration. An alternative to the ratchet approach described above is a one-way clutch bearing that prevents bounce-back and locks the wings24in place.. The torsion spring deployment previously discussed can be modified to include an upper and lower extension spring to increase the deployment force. Finally, the housing can be modified to incorporate a knurled surface to grip onto the fin shaft when the housing is tightened. The knurled steel surface will deform the aluminum shaft to enhance the grip in order to survive the high-G shock. In various embodiments, the wing system is unpowered and does not require battery or control. In the assisted deployment embodiment, the spring initiates the wing deployment. However, once the wings are unfolded past the mortar round body profile (outside of the flowstream coming off of the mortar body20), the drag force will supplement the spring force to complete the wing deployment. This drag force will apply a constant rearward force against the wings to ensure that the locking mechanism has time to fully engage.

As shown inFIG.10, fin connector vanes60can be provided as part of the tail fin assembly42of the glide kit according to embodiments of the present disclosure. The fin connector vanes60can provide distinct aluminum airfoil surfaces that bridge the space between the original mortar fins62. The fin connector vanes60provide aerodynamic stabilization when the munition12is first launched, until the wings24deploy. The fin connector vanes60are passive stabilization surfaces and can be bolted onto the existing fins62, for example. In embodiments such as shown inFIG.10, a pair of fin connector vanes62sits atop the munition12(together, the upper fin connectors) and another pair of fin connector vanes62sits below the munition (together, the lower fin connectors).

As shown inFIGS.11through22, embodiments of the glide kit38according to the present disclosure include independently controllable canards26which can be modulated symmetrically to control range or modulated asymmetrically to control bank angle and reduce lateral offset. The canards26can be controlled via the canard control subsystem as described herein.

The front module50including the canard housing52and canards26attaches to the front end of the mortar round body20. In various embodiments, the canard housing52includes top54and bottom56members having a portion with a concave shape (e.g.,53in top member54and59in bottom member56), wherein the top54and bottom56members can be joined together such that the concave portions form a substantially frustoconical ring. In at least one embodiment, a screw or similar device is screwed into one or more extractor holes57to secure the canard housing52to the mortar body20, and any remaining holes remain available to extract the mortar body20out of the mortar tube22in case of misfire. In other embodiments, the canard housing52is secured to the mortar body20through an interference fit facilitated by the frustoconical ring shape of the joined concave portions53,59of the top54and bottom56members.

The canard housing52further includes canard deployment shrouds55, which can be formed with and extend from the concave portion59of the canard housing bottom member56. Each canard deployment shroud55is adapted to retain a respective canard26so as to permit the canard26to rotate and/or pivot about a respective canard axis (e.g., X and Y inFIG.14). The canard deployment shrouds55can be formed so as to be diametrically opposite one another, and each canard deployment shroud55can be formed with a top slot150on the top surface152thereof, wherein the top slot150is adapted to receive a corresponding flange160on the top member54of the canard housing52. Each flange160can be secured within a respective top slot150using a screw extending through an opening (e.g.,155) or a similar attachment mechanism.

The canards26are mounted within the canard housing52and rotate about fixed pivot axes to deploy. Like the wings24, the canard surfaces can consist of GOE389 flat-bottomed airfoils. The canards26are tapered so that when they are stowed, they fit alongside the curvature of the munition body20and do not extend beyond the outer moldline of the mortar body20.

The canard housing shrouds can be airfoil-shaped to substantially increase the glide performance of the munition12. In various embodiments, each shroud55is formed with a leading edge156, an outer side edge157and a trailing edge158, wherein the outer side edge157and the trailing edge158of each shroud55is further formed with an outer slot159which permits rotating movement of a respective canard26about its respective axis (e.g., X or Y). As shown inFIG.11, each canard26is secured to a canard rotation mount164, which can be formed with a canard mount opening166for mating with a rotation pin (not shown) secured in the canard housing shroud55along a respective axis X or Y to permit pivoting and/or rotating movement of each canard26within the outer slot159. As further shown inFIG.11, each canard26can be formed with an indentation170on a leading surface172wherein the indentation170can be employed to retain a rope or cord during operation.

As shown inFIG.23, one or more torsion springs190,192are provided and can be mounted onto each rotation pin, operable to simultaneously press against the canard26and the canard housing52to rotate the canard26to its final, fully extended position. In various embodiments, two torsion springs are incorporated for each canard. On each side, a first torsion spring190is mounted above the canard26and a second torsion spring192is mounted below the canard26. The upper190and lower192torsion springs both mount around the rotation pin and press against a second pin (not shown) through the canard26. The canards26can be restrained in their stowed position by a cord such as a Vectran cord that wraps around the canard26and into the outer slot159of the canard shrouds55. In various embodiments, the Vectran cord is stretched across Nichrome wire and secured internally to resist the torsion springs190,192. When an electrical signal is sent to the Nichrome wire, it heats up and burns the Vectran cord, allowing the torsion springs190,192to deploy the canards26.

Similar to the wing deployment, in various embodiments, a spring tab lock194can be employed to restraint the canard26in its fully deployed position. The spring tab lock194can be embodied as a single-tooth ratchet that pops out once the canard26rotates to restrain the canard26in the fully deployed, i.e., fully extended position.

Embodiments of the shroud airfoil can be a NACA 0030 shape with 30% maximum thickness, for example, where the large airfoil thickness is required to cover the one or more batteries. In various embodiments, each canard housing shroud55houses one or more batteries, at least one sensor, a canard deployment mechanism and a canard locking mechanism. The sensor(s) can include a barometric pressure sensor, a shock sensor and/or an accelerometer.

In various embodiments, SMA wire can be used to control the canard26deployment angle. SMA wire is a hybrid blend of Nickel and Titanium formed as small diameter wire (25 μm up to 510 μm). The wire can contract up to a certain percentage (e.g., four to six percent) of its length when electrically driven or heated. The alloy changes its internal structure from Martensite (low temperature state, low Modulus of Elasticity) to Austenite (high temperature state, high Modulus of Elasticity) when it is heated. When the wire is cool (Martensitic state), it can be pre-stretched and when heated, it will contract back to the original length while providing substantial retraction force. In accordance with the present disclosure, the SMA wire is integrated as an actuator to control the canard deployment.

The SMA wire can be configured as a lever mechanism for canard deployment. The lever mechanism provides mechanical advantage which is well suited to SMA wire. In various embodiments, the SMA wire pulls against the torsion spring(s) used to deploy each canard26. Because SMA can only recover a small amount of strain, the lever mechanism enables small wire contraction to create a large rotation of the canard. When the canard26is stowed, the SMA wire175is fully stretched in its low-Modulus Martensitic state. When the canard26is spring-deployed to its maximum position, the SMA wire is still in its fully stretched low-Modulus Martensitic state. When the canard26is to be adjusted, the SMA wire175is electrically heated to contract somewhere between full contraction and full stretch, as shown inFIG.22. This causes the canards to retract to some intermediate sweep angle. To reduce the canard angle, the SMA wire is electrically heated until it is somewhere between the low-Modulus Martensitic state and the high-Modulus Austenitic state. The increases stiffness and contracting of the SMA wire overcomes the torsion spring stiffness to rotate the canards aft, reducing the canard angle. To increase the canard angle, the electrical heating to the SMA is decreases and the stiffness of the SMA reduces, allowing the torsion springs to push the canard out further and simultaneously expand the SMA to its original fully-stretched state. The electrical heating of the SMA can be precisely controlled to achieve intermediate canard angles. As shown inFIGS.21and22, the SMA wire175is secured within the indentation170of the leading surface172of each canard26.

For the embodiments of the present disclosure with canard deployment control, the power to the SMA wire can be modulated based on the canard sweep angle commanded by the controller.

To complete the canard control circuit, a feedback device is required for determining the rotation angle. An exemplary feedback device is a rotary membrane potentiometer which can be positioned on the bottom plane of the canard26. Membrane potentiometers consist of flat resistance tracks printed on either foil or FR4 circuit board. As a wiper rod moves along the circular resistance track, it changes the electrical resistance, which corresponds to a rotation angle. For the canard deployment control aspects according to the present disclosure, the canard lever pin acts as the wiper rod. When the canard26rotates, the lever arm slides across the membrane potentiometer, changing the electrical resistance. The change in electrical resistance is sent to the microcontroller to determine the corresponding sweep angle. This is the feedback signal for active canard sweep control.

An alternative canard deployment system includes an upper and lower extension spring that pulls against a dowel pin in the canard to deploy it. This system can employ a one-way clutch bearing that is secured to the canard's rotation shaft. The outer housing of the bearing is secured to the canard such as by press-fit, for example, while the inner race of the bearing rides on a shoulder bolt proceeding through the canard housing. The shoulder bolt is fixed in place and the canard/bearing is able to rotate forward due to the spring excitation. However, the clutch bearing prevents the canard from rotating backwards. This system prevents “bounce-back” of the canards and holds them in their fully deployed state. The clutch bearing canard locking mechanism can only be implemented on the variations of the glide kit for range extension because the clutch bearing prevents modulation of the canard sweep angle.

It will be appreciated that the wing and canard surfaces can be fabricated with a preset inclination angle to optimize aerodynamic performance. The wings24can be fabricated with the flight surface angled relative to the rotation plane. When the wings24rotate outward to deploy, the flight surface is already inclined relative to the flowstream to provide a pitch-up moment contribution. The axis of inclination is such that the inclined flight surface has negligible impact on the round's aerodynamics when the wings24are stowed. There is substantial impact once the wings24rotate outward. Likewise, the canards26can be fabricated with the flight surface angled relative to the rotation plane. Once the canards26deploy, they are already inclined to provide a pitch-up moment contribution.

It will be appreciated that the canard control subsystem240can be independent for the left and right canards26. In such embodiments, each canard26has its own SMA circuit, battery, and feedback sensor, enabling independent control of each canard26. When the canards26are asymmetrically contracted such as inFIG.20, for example, a small roll moment will be generated which can be used to control the munition's bank angle. This will allow the glide-munition's lateral offset to be modulated as atmospheric winds blow the munition off its nominal course.

FIG.24is a block diagram illustrating components of a processing system200that can be provided to incorporate the onboard state estimator subsystem230and canard control subsystem240. Such system200can be integrated into the glide kit38such as by storage within one or more canard housing shrouds55.

As shown inFIG.24, the system200can include a microcontroller (or “controller”)202, memory204, battery206, a left SMA driver208to actuate the left canard, a right SMA driver210to actuate the right canard, a barometric pressure sensor212, an accelerometer214, a shock sensor216, a canard actuator218and a canard rotation feedback sensor220. The system200can also include state estimator subsystem230and canard control subsystem240. Embodiments of the battery206can include a 4V, 200 mAh, 7 A max current, 50,000 G shock rated lithium metal oxide battery. Embodiments of the left SMA driver208can include an SMA driver with PWM directional output and 2.5 A max current to control the left SMA wire. Embodiments of the right SMA driver210can include an SMA driver with PWM directional output and 2.5 A max current to control the right SMA wire. Embodiments of the barometric pressure sensor212can include a MEMS digital barometer, 3.8-18.2 psi, 10,000 G shock rated, measures altitude up to 30,000 feet. Embodiments of the accelerometer214can include a tri-axial accelerometer, ±4 G up to ±30 G, 10,000 G shock rated. Embodiments of the shock sensor216can include a shock sensor with an electrical trigger at 4,000 G Shock, shock rated to 20,000 G. Embodiments of the canard actuator218can include380μm SMA wire with 4.4 lbs pull force. Embodiments of the canard rotation feedback sensor220can include a resistive potentiometer, printed on FRF circuit board, with 0-90° customized sensing range. It will be appreciated that the microcontroller202, left SMA driver208, right SMA driver210, barometric pressure sensor212, and accelerometer214can be provided on a circuit board secured within the canard housing52.

In various embodiments, the state estimator subsystem230is a two-part state estimator that accurately estimates the launch velocity and angle of a given mortar round with the glide kit38installed, with no inputs from a user. The state estimator subsystem230can also compute the atmospheric winds during the glide maneuver. In various embodiments, the state estimator subsystem230can rely solely on the barometer212and accelerometer214as sensor inputs. A launch estimator portion of the state estimator subsystem230can simultaneously determine the launch conditions and compute the accelerometer bias error, using the first few seconds of post-launch sensor data, for example. A wind and state estimator portion of the state estimator subsystem230can approximate the glide munition's position, velocity, and atmospheric winds. The estimated launch conditions and winds are used to accurately predict the glide-munition's position and velocity. This data and the target point can be used by the microcontroller202and memory204storing programming instructions to determine how the canard rotation angle should be adjusted to guide the munition to the desired impact point. In various embodiments, the programming uses the current state values and wind values to approximate where the glide-munition will impact. The programming internally iterates on the canard rotation angles to find the settings that will minimize deflection and range error. In embodiments, the projection controller programming is recalled at a certain update rate during the gliding descent to generate updated canard commands.

It will be appreciated that the state estimator subsystem230is operable to detect an adjustment-influencing condition such as launch angle and barrel speed and, based on the detected adjustment-influencing condition, instruct the canard deployment subsystem to deploy at least one of the canards into a different position, such as the canard-expanded position or the canard-adjusted position. The state estimator subsystem230can operate with the microcontroller202and at least one of the sensors212,214,216.

In various embodiments, a munition as enhanced according to the present disclosure stores a set of pre-determined target impact points in memory204that correspond to each combination of charge weight and launch angle. Post-launch, the glide-kit estimates the initial conditions and identifies the closest corresponding impact point (i.e., range target). The canard control subsystem240is then used to guide the munition to the range target while minimizing the deflection.

For each mortar launch, the following process can occur:1) Mortar fires with perturbed velocity and launch angle2) State estimator determines charge weight and launch angle, e.g., to within 1-degree3) A lookup table is used to identify corresponding range target based on charge weight and launch angle4) Controller guides glide munition to target impact range at minimum deflection

For bounded perturbations around a nominal launch condition, the estimator algorithm can identify the same range target for each launch. Therefore, repeated mortar launches at the nominal launch condition will all target the same impact point. The estimator and projection controller can guide the mortar to the target despite atmospheric winds and launch perturbations. This CEP attenuation aspect substantially reduces the CEP for a series of mortar launches. As an example, the combination of the state estimator subsystem and canard control subsystem240decreases the M934 CEP from 92 m to 42 m, a decrease of 54%.

The microcontroller202is thus operable to receive a measurement from one or more sensors, and based on the measurement, deploy a sweep angle adjustment to at least one of the two canards. It will be appreciated that the canard control subsystem240is operable to position each of the canards in a canard-undeployed position, a canard-expanded position and a canard-adjusted position between the canard-undeployed position and the canard-deployed position. The canard-adjusted position can represent an adjustment to increase range or improve chances of reaching a desired target, for example.

In various embodiments, the controller202is operable to receive a measurement from the accelerometer214and the barometric pressure sensor212and based on the received measurements from the accelerometer214and the barometric pressure sensor212, determine a launch angle and barrel speed of the mortar round. The controller202is further operable to determine the charge weight of the munition based on barrel speed and the desired impact point of the munition based on launch angle and charge weight. The controller202is further operable, based on the determination of the barrel speed and launch angle, to predict a position and a velocity of the mortar round. The controller202is further operable to determine a projected impact point based on the predicted position and velocity. The controller202is further operable to determine a canard rotation angle adjustment based on the predicted position, predicted velocity, desired impact point and projected impact point of the mortar round.

The determined charge weight and launch angle corresponds to a certain time for the glide munition to reach the peak altitude. The left and right canards are fully-extended at the peak altitude. In certain embodiments, SMA can be used to independently adjust the left and right canard angles after the initial deployment. The time to reach peak altitude is stored in a table in the onboard memory based on the charge weight and launch angle. The delay time is stored in the memory to trigger the Nichrome wire to burn through the restraining Vectran on each side of the canard housing to deploy the left and right canards.

The battery206can provide a sustained, 2.5 A current output and a peak current of 6.5 A. The microcontroller202can run programming stored in memory204and/or in the state estimator subsystem230and canard control subsystem240. The microcontroller202takes inputs from the accelerometer214, barometric pressure sensor212, and rotation feedback sensor220, and sends SMA commands to the right210and left208SMA driver ICs. The right SMA driver IC210provides high current PWM signals to control right canard contraction. The left SMA driver IC208provides high current PWM signals to control left canard contraction.

The shock sensor is rated for 20,000 Gs and will elicit a signal once the 4,000 G shock threshold has been exceeded. This trigger alerts the microcontroller to start processing the estimator algorithms after a determined time delay. The digital barometer provides altitude and altitude-rate date at 25 Hz for the state estimator. It also triggers when the maximum altitude has been achieved so that the canards can be deployed. The electronics module can be mounted at the front of the munition, before the obturator. Therefore, the barometer is not exposed to the high-pressure region around the launch gases.

In various embodiments, the device can be produced using an additive manufacturing process in which a liquid binding agent is deposited to join powder particles. Binder material is placed between each layer. The printed part is placed in an oven to cure and reach full strength. Key benefits of Binder-Jet printing over traditional metal printing (e.g. Direct Laser Metal Sintering) is that a support structure is not required for building the parts, which allows complex internal structures to be fabricated. It also uses far less material than traditional metal printing which greatly reduces the cost.

In various embodiments, the glide-kit components can be fabricated from a420Stainless Steel infiltrated with Bronze in a 60/40 ratio of steel to Bronze. The material yield strength is 62 ksi (427 MPa) and the elastic modulus is 21.4 MPsi (147 GPa). The final parts are both machinable and weldable offering many integration options to attach to the mortar round. In embodiments, the total weight of the steel glide-kit components is 530 g. In various embodiments, the canards and wings can be fabricated from aluminum instead of steel which decreases the weight. The steel fabrication of the canard housing and wing housing supports launch survivability.

As described elsewhere herein, the canard control subsystem240can be driven by SMA wire. The canards are initially spring-deployed to the fully-extended position. When the SMA wire is heated, the torsion spring is compressed and the canards rotate backward, increasing the sweep angle. When the SMA wire is cooled, the torsion spring unwraps, rotating the canard forward and decreasing the sweep angle. Both motions require active electrical control of the SMA wire to control the Austenite to Martensite transition state and provide controlled motion in each direction. The SMA wire can also be cycled electrically to achieve a continuous canard motion.

Unless otherwise stated, devices or components of the present disclosure that are in communication with each other do not need to be in continuous communication with each other. Further, devices or components in communication with other devices or components can communicate directly or indirectly through one or more intermediate devices, components or other intermediaries. Further, descriptions of embodiments of the present disclosure herein wherein several devices and/or components are described as being in communication with one another does not imply that all such components are required, or that each of the disclosed components must communicate with every other component. In addition, while algorithms, process steps and/or method steps may be described in a sequential order, such approaches can be configured to work in different orders. In other words, any ordering of steps described herein does not, standing alone, dictate that the steps be performed in that order. The steps associated with methods and/or processes as described herein can be performed in any order practical. Additionally, some steps can be performed simultaneously or substantially simultaneously despite being described or implied as occurring non-simultaneously.

It will be appreciated that algorithms, method steps and process steps described herein can be implemented by appropriately programmed computers and computing devices, for example. In this regard, a processor (e.g., a microprocessor or controller device) receives instructions from a memory or like storage device that contains and/or stores the instructions, and the processor executes those instructions, thereby performing a process defined by those instructions. Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable media having computer readable program code embodied thereon.

Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, as exemplified above. The program code may execute entirely on a user's computer, partly on a user's computer, as a stand-alone software package, partly on a user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider) or in a cloud computing environment or offered as a service such as a Software as a Service (SaaS).

Where databases are described in the present disclosure, it will be appreciated that alternative database structures to those described, as well as other memory structures besides databases may be readily employed. The drawing figure representations and accompanying descriptions of any exemplary databases presented herein are illustrative and not restrictive arrangements for stored representations of data. Further, any exemplary entries of tables and parameter data represent example information only, and, despite any depiction of the databases as tables, other formats (including relational databases, object-based models and/or distributed databases) can be used to store, process and otherwise manipulate the data types described herein. Electronic storage can be local or remote storage, as will be understood to those skilled in the art. Appropriate encryption and other security methodologies can also be employed by the system of the present disclosure, as will be understood to one of ordinary skill in the art.

The present disclosure contemplates a variety of different systems each having one or more of a plurality of different features, attributes, or characteristics. A “system” as used herein refers to various configurations of: one or more central controllers or microcontrollers, and/or one or more subsystems alone or in communication with one or more central controllers or microcontrollers, for example.

In certain embodiments in which the system includes a server, central controller, or microcontroller, the server, central controller, or microcontroller is any suitable computing device (such as a server) that includes at least one processor and at least one memory device or data storage device. The processor of the additional device, server, central controller, or microcontroller is configured to transmit and receive data or signals representing events, messages, commands, or any other suitable information between the server, central controller, or remote host and the additional device.