US20220178658A1

US20220178658A1 - Method of controlling ejection of a missile from a canister and system therefor

Info

Publication number: US20220178658A1
Application number: US17/602,672
Authority: US
Inventors: Rabin Shaltiel; Ofer AVISHAI
Original assignee: Israel Aerospace Industries Ltd
Current assignee: Israel Aerospace Industries Ltd
Priority date: 2019-04-11
Filing date: 2020-03-19
Publication date: 2022-06-09
Also published as: IL265993B2; IL265993A; EP3953656A4; WO2020208625A1; EP3953656A1

Abstract

A method for reducing or eliminating “Missile Tip-off Effect” (MTE) of a missile ejected from a canister. The method includes: receiving data of desired canister state in response to a launch command. The method further include perform repeatedly until an MTE control criterion is met: (a) receiving, from a sensor associated with the canister, data of measured canister state, and (b) processing the data of the measured canister state and desired canister state, for outputting data indicative of a command to an actuator associated with the canister for modifying at least the angular position of the canister, thereby reducing or eliminating the (MTE) effect.

Description

TECHNICAL FIELD

The presently disclosed subject matter relates to a method of controlling ejection of a missile from a canister and a system therefor.

BACKGROUND

While ejecting a missile from a canister, the missile may develop angles and angular rates due to parasitic initial conditions. There are several parasitic effects that the missile may encounter while ejecting from the canister. These effects are commonly known as the “Missile Tip-off Effect” (MTE).
MTE may occur due to various reasons, such as:

- Acoustic effects and canister-missile elasticity can resonate in the canister whilst the missile is ejecting. The canister interacts with the missile, and due to contact between the canister and the missile, MTE develops.
- When the missile's centre of gravity passes outside the canister upper plane, and if the canister is not aligned with the vector of gravity. The reaction due to contact between the missile and canister and the gravity force creates a moment that develops angular rates, and hence MTE.
- Missile geometric tolerances such as missile centre of gravity not aligned with the symmetry axis, thrust misalignment, etc.
- Flow turbulences due to gas ejecting from the missile, and aerodynamic effects, may cause forces and moments that cause MTE.

Solving each of the above causes of MTE may be complex and thus very costly. Therefore most solutions deal with controlling the missile after launch.
Common solutions for MTE may use known per se existing or improved missile actuators, or add a Thrust Vector Control (TVC) that alleviates the MTE effect. If the current actuators are aerodynamic actuators, they may not effectively deal with MTE, since they are effective only at high velocities. In order to render the aerodynamic actuators effective at low velocities, the aerodynamic fins need to be redesigned. Such redesign can decrease missile performance at higher velocities. If one chooses to integrate into the missile design TVC units such as jet-vanes, a gimbaled nuzzle etc., MTE may be reduced. However, such TVC units are costly and add extra weight to the missile, and hence decrease missile performance.
There is thus a need in the art to provide for a new technique for controlling ejection of a missile from a canister.
The discussion above teach background information that may be applicable to the presently disclosed subject matter.

GENERAL DESCRIPTION

- According to one aspect of the presently disclosed subject matter there is provided a method for reducing or eliminating “Missile Tip-off Effect” (MTE) of a missile ejected from a canister comprising, by a processor and associated storage:
  - a. receiving data indicative of desired canister state in response to a launch command,
  - perform repeatedly until an MTE control criterion is met:
  - b. receiving, from at least one sensor associated with the canister, data indicative of measured canister state;
  - c. processing at least said data indicative of measured canister state and desired canister state, for outputting data indicative of a command to at least one actuator associated with the canister for modifying at least the angular position of the canister;
  - thereby reducing or eliminating said (MTE) effect.

In addition to the above features, the system according to this aspect of the presently disclosed subject matter can comprise one or more of features listed below, in any desired combination or permutation which is technically possible:

- The measured canister state includes measured canister angle and wherein desired canister state includes desired canister angle.
- The measured canister state includes measured canister rate and wherein desired canister state includes desired canister rate.
- The processing for outputting data indicative of said command complies with Equation 1:

$M_{c} = - K \cdot (I_{z z_{c a n i s t e r}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot (θ_{canist e r} - θ_{c o m})))$

- The said measured canister state includes measured missile angle and wherein desired canister state includes desired canister angle.
- The measured canister state includes measured missile rate and wherein desired canister state includes desired canister rate.
- The processing for outputting data indicative of said command complies with Equation 2:

$M_{c} = - K_{canister} \cdot (I_{z z_{c a n i s t e r}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q_{canister} - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{canister}}{I_{zz - canister}}) \cdot (θ_{canister} - θ_{com}))) + - K_{missile} \cdot (I_{{zz}_{canister}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q_{missile} - {\dot{θ}}_{com}) + (ω_{n}^{2} - \frac{K_{canister}}{I_{zz - canister}}) \cdot (θ_{missile} - θ_{com})))$

- The larger the difference between the desired canister state and the measured canister state, the larger is said command
- The measured canister state includes data indicate of remaining flight time of the missile in the canister, such that for the same difference in measured angle or rate vs. desired angle or rate, the shorter the remaining flight time, the larger the command.
- Modifying on-the-fly said data indicative of desired canister state.
- At least one of said sensors is fitted on the canister.
- At least one of said sensors is fitted on the missile.
- An array of canisters.
- The data indicative of measured canister state is obtained by averaging the data indicative of the canister state of each canister of said array.
  - According to one aspect of the presently disclosed subject matter there is provided a system for reducing or eliminating “Missile Tip-off Effect” (MTE) of a missile ejected from a canister comprising, a processor and associated storage configured to:
- receiving data indicative of desired canister state in response to a launch command, perform repeatedly until an MTE control criterion is met:
  - a. receiving, from at least one sensor associated with the canister, data indicative of measured canister state;
  - b. processing at least said data indicative of measured canister state and desired canister state, for outputting data indicative of a command to at least one actuator associated with the canister for modifying at least the angular position of the canister;
    - thereby reducing or eliminating said (MTE) effect.

This aspect of the disclosed subject matter can comprise one or more of features listed above and applied to the system, mutatis mutandis, in any desired combination or permutation which is technically possible.
According to another aspect of the presently disclosed subject matter there is provided a non-transitory program storage device readable by a computer, tangibly embodying computer readable instructions executable by the computer to perform a method for reducing or eliminating “Missile Tip-off Effect” (MTE) of a missile ejected from a canister.
This aspect of the disclosed subject matter can comprise one or more of features listed above and applied to the non-transitory program storage device, mutatis mutandis, in any desired combination or permutation which is technically possible.
Among advantages of certain embodiments of the presently disclosed subject matter is the use of sensors fitted on the canister (rather than on the missile) and utilization of the canister's actuator, thereby utilizing a lighter missile considering that the need to fit larger and heavier actuators on the missile (as is the case in some prior art solutions) may be obviated. Yet another non-limiting advantage is the “shift” of using hardware components (such as sensors and actuators) to a sustainable multi-use canister assembly rather than fitting them for one-time use on a disposable missile, thereby drastically reducing the overall system costs.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it can be carried out in practice, embodiments will be described, by way of non-limiting examples, with reference to the accompanying drawings, in which:

FIG. 1 illustrates an exemplary operational scenario, in accordance with certain embodiments of the presently disclosed subject matter;

FIG. 2 illustrates a schematic illustration of a system, in accordance with certain embodiments of the presently disclosed subject matter;

FIG. 3 illustrates a functional block diagram of a system in accordance with certain embodiments of the presently disclosed subject matter;

FIG. 4 illustrates a functional block diagram of a control system in accordance with certain embodiments of the presently disclosed subject matter;

FIG. 6 illustrates a generalized flow-chart of a system in accordance with certain embodiments of the presently disclosed subject matter;

FIG. 7 illustrates schematically a simplified chart comparing canister configuration with and without utilization of a technique in accordance with certain embodiments of the presently disclosed subject matter;

FIG. 8 illustrates a generalized flow-chart of a system in accordance with certain other embodiments of the presently disclosed subject matter; and

FIG. 9 illustrates schematically a simplified chart comparing canister configuration with and without utilization of a technique in accordance with certain other embodiments of the presently disclosed subject matter.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the presently disclosed subject matter.
Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing”, “computing”, “representing”, “comparing”, “generating”, “assessing”, “matching”, “updating”, “reducing”, “eliminating”, “outputting”, “modifying”, receiving”, “obtaining” or the like, refer to the action(s) and/or process(es) of a computer that manipulate and/or transform data into other data, said data represented as physical, such as electronic, quantities and/or said data representing the physical objects. The term “computer” should be expansively construed to cover any kind of hardware-based electronic device with data processing capabilities including, by way of non-limiting example, the processor disclosed in the present application.
The terms “non-transitory memory” and “non-transitory storage medium” used herein should be expansively construed to cover any volatile or non-volatile computer memory suitable to the presently disclosed subject matter.
The operations in accordance with the teachings herein may be performed by a computer specially constructed for the desired purposes or by a general-purpose computer specially configured for the desired purpose by a computer program stored in a non-transitory computer-readable storage medium.
Embodiments of the presently disclosed subject matter are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the presently disclosed subject matter as described herein.
As used herein, the phrase “for example,” “such as”, “for instance” and variants thereof describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to “one case”, “some cases”, “other cases”, “one example”, “some examples”, “other examples” or variants thereof means that a particular described method, procedure, component, structure, feature or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the presently disclosed subject matter, but not necessarily in all embodiments. The appearance of the same term does not necessarily refer to the same embodiment(s) or example(s).
Usage of conditional language, such as “may”, “might”, or variants thereof should be construed as conveying that one or more examples of the subject matter may include, while one or more other examples of the subject matter may not necessarily include, certain methods, procedures, components and features. Thus such conditional language is not generally intended to imply that a particular described method, procedure, component or circuit is necessarily included in all examples of the subject matter. Moreover, the usage of non-conditional language does not necessarily imply that a particular described method, procedure, component or circuit is necessarily included in all examples of the subject matter.
Attention is first drawn to FIG. 1, illustrating an exemplary operational scenario, in accordance with certain embodiments of the presently disclosed subject matter. As shown, a missile 4 is ejected from a canister 2 in an array of canisters 3.
Note that by virtue of the MTE, the missile may be ejected in an undesired angle e.g. as depicted schematically in 5.
Turning now to FIG. 2, it illustrates a schematic illustration of a system, in accordance with certain embodiments of the presently disclosed subject matter. Thus, in order to cope with the specified Missile Tipoff Effect (MTE) (as will be explained in greater detail below), in response to a launch command (including meeting certain conditions such as time elapse after launch), the angular position of the canister 21 (fitted on carrier 22) may be modified by an actuator 23 in response to data indicative of an appropriate command. The command is determined based on processing data indicative of canister state as measured by at least one canister sensor measurements (depicted schematically as 24) and/or at least one missile sensor measurement depicted schematically as 25. Note that the sensor associated with the canister may be e.g. fitted on the canister and/or the missile and may generate data indicative of canister state (e.g. canister angle and/or canister angular rate and/or missile's angle and/or missile's angular rate).
Note that for simplicity of explanation, the description below focuses on the specified non-limiting examples of measured canister state. There may be other factors that are included in the measured canister's state, such as data indicative of the remaining flight of the missile inside the canister.
Note also that there may be more than one canister sensor, and, likewise, more than one missile sensor, depending upon the particular application. The specified sensor or sensors may be mounted on the canister and/or the missile in a known per se manner (e.g. the sensors may be fitted e.g. in/on the canister, and/or in/on the missile).
Note also that in certain embodiments there may be an array of canisters configured to launch a plurality of missiles. Operation of the system may be adapted to utilize the input from the plurality of sensors fitted on the array of canisters, all as will be explained in greater detail below.
Note that whenever reference is made to “an actuator”, “a canister”, or “a sensor”, this may likewise apply to actuators or canisters, mutatis mutandis.
Note also that the structure of the (canister's) carrier, as well the operation of an actuator (in response to a command), is generally known per se.
Note also that the term “measured” may embrace also other operations such as pertinent processing of raw measured data.
Bearing this in mind, attention is drawn to FIG. 3, illustrating a functional diagram of a system 300. The illustrated system includes a control system 301 operatively coupled to a canister's actuator 302. The canister's actuator controls the angular position of the canister 303 (e.g. angle and/or angular rate).
The control system 301 is also operatively coupled to the canister's sensor(s) 304 and missile's sensors 305 for obtaining data indicative of measured canister state (utilizing the canister and/or missile sensors) as well as desired canister's state (e.g. extracted from to database 307) for outputting a command to the actuator affecting the canister's angular position (angle and/or rate), and consequently also modifying the missile's angular position (305). The whole sequence is repeated, e.g. in a closed loop fashion until a Missile Tip-off Effect (MTE) control criterion is met. This occurs for example when data indicative of the measured canister state matches data indicative of the desired canister state.
The desired canister's state (e.g. desired angle of canister) is determined for instance in a manner that guarantees that when the missile is ejected from the canister, its flight trajectory “compensates” for the inherent parasitic effects that the missile encounters while ejecting from the canister, thereby reducing or eliminating the undesired MTE effect. As a result, the missile may fly in a designated trajectory, obviating the need to utilize cumbersome hardware, such as large steering surfaces, for coping with the MTE effect, as is the case in prior art solutions.
Note that when reference is made to sensing, measuring, receiving and/or processing data from sensors, this should be construed (whenever applicable) to include “data indicative of . . . ”, for instance following A/D, if necessary, and/or possible preprocessing of the data.
Turning now to FIG. 4, it illustrates a functional block diagram of a control system (CS) (301) in accordance with certain embodiments of the presently disclosed subject matter.
The CS system 301 may in some examples be a computer. It may, by way of non-limiting example, comprise a processing circuitry 405. Processing circuitry 405 may comprise at least one processor 401 (e.g. a general purpose processor), and memory 402. Processor 401 may be specially configured for the desired purpose by a computer program stored in a non-transitory computer-readable storage medium.
Each may be configured to execute several functional modules in accordance with computer-readable instructions, e.g. in accordance with flow charts disclosed with reference to FIGS. 6 and 8.
The CS system may include input/output (I/O) 407, that may have conventional input/output peripherals such as a keyboard, mouse or touchscreen and/or other peripherals. System 301 may also include network interface 409 to provide connectivity to network 110 for sending or receiving data. The CS may reside fully or partially on board the system 10 or be placed at least partially in a remote location and communicate with other portions thereof residing in system 10.
It is noted that the teachings of the presently disclosed subject matter are not bound by the system described with reference to FIGS. 3 and 4. Equivalent and/or modified functionality can be consolidated or divided in another manner and can be implemented in any appropriate combination of software with firmware and/or hardware and executed on a suitable device.
The equation below describes, by way of example, data indicative of the actuation command to the canister actuator, and assumes, for simplicity, that only canister sensor(s) are utilized.
Thus,
$\begin{matrix} M_{c} = - K \cdot (I_{zz_canister} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot (θ_{canist e r} - θ_{c o m}))) & Eq1 . \end{matrix}$

Where:

M_c—an actuation command to the canister's actuator for modifying the angular position of the canister.
K—normalizing gain
Izz_canister—canister moment of inertia around perpendicular to missile ideal ejection direction
ξ—desired closed loop damping coefficient
ω_n—desired natural frequency mode
K_canister—canister stiffness
q—measured canister angular rate
{dot over (θ)}_com—desired canister angular rate
θ_canister—measured canister angle
θ_com—desired canister angle
Note, that the measured canister angle θ_canistermay be obtained from the canister's sensor and the measured canister's angular rate q may be measured or calculated therefrom.
Note also that the desired canister angle θ_comis obtained and the desired {dot over (θ)}_comcanister angular rate may be obtained or calculated therefrom. It is thus noted that whenever a reference is made to “measured” e.g. angle or rate, it encompasses also processing. Note that the resulting activation command M_cthat is fed to the canister actuator will result in modification of its angular position (angle and possibly rate). In the latter example illustrated with reference to Eq. 1, both the measured angular rate q and the angle position θ_canisterare controlled in the sense that the activation command will be nulled in cases where both the angular rate and angle match their corresponding desired values {dot over (θ)}_comand θ_com. In accordance with certain other embodiments, only the angle is considered, e.g. θ_canister(measured) vs. θ_com(desired), yielding possibly a different flight trajectory of the missile for eliminating or reducing the MTE effect. The latter are obviously only non-limiting examples for overcoming the MTE effect. These examples are not limiting (e.g. only the rate may be controlled) and/or other parameters for control may be added or modified, all depending upon the particular application.
As readily arises from the equation above, there are various coefficients (including in the non-limiting example above: K, Izz_canister, ξ, ω_n, K_canister) and the command M_cis based by this example on the difference between the measured canister angle and the desired one, as well as on the difference between the respective rates. Note that the other coefficients (e.g. K) may also affect the missile trajectory as it ejects from the canister for coping with the MTE effect, all depending upon the particular application.
The invention is not bound by the specified coefficients.
Note also that the control may cease in case the “MTE control criterion is met”. This criterion may be met, e.g. in cases where the desired and measured controlled parameters (e.g. angular position and/or rate) match, or when the missile ejects from the canister, or when the command to the actuators violates system specifications (e.g. is overly large), to the extent that following it may damage the canister and/or missile, and/or others, depending upon the particular application.
Note that whenever the term match (or alike) is used, it may embrace also a possible error, say ±up to 10% or in accordance with other embodiments ±up to 5%.
Note also that the specified Eq. 1 is by no means binding. Thus, by way of non-limiting example, if additional parameters are monitored, such as, for instance, the position of the missile within the canister, and the remaining flight duration of the missile within the canister, a more accurate control (e.g. applied by way of non-limiting example mutatis mutandis to equation I or II—see below) may be achieved with possibly better results for coping with the MTE effect.
Note also that in case of an array of canisters, the actuation command may depend upon input from sensors fitted on two or more of the canisters and/or two or more of the missiles. Thus, by way of non-limiting example, measured canister angular rate (q) may refer to averaging the measured canister angular rates as obtained (or derived) from two or more sensors that are fitted on respective two or more canisters of the array. The same holds true for averaging canister's angle(s) over an array of canisters, mutatis mutandis. Averaging is, of course, only a non-limiting example.
Referring to FIG. 6, there is illustrated a generalized flow chart of a sequence of operations in accordance with certain embodiments of the presently disclosed subject matter. The specified Eq. 1, illustrates a non-limiting example of the specified sequence of operations.
Note that the flow chart with reference to FIG. 6 assumes, for simplicity, that only canister sensors are utilized.
Thus, in step 601, data indicative of desired canister state (e.g. desired canister's angle and angular rate) is received in response to a launch command.
Then, until an MTE control criterion is met (602,603):

- Data indicative of a measured canister state (e.g. canister's rate and angle) is received from at least one sensor associated with the canister (604);
- Thereafter, the data indicative of measured canister state (e.g. canister's rate and angle), and desired canister state, is processed (e.g. in compliance with Eq. 1), for outputting data indicative of a command to at least one actuator associated with the canister, for modifying at least the angular position of the canister 605.

As will be exemplified in greater detail below, the MTE criterion may be modified, depending upon the particular application.
By way of non-limiting example, the specified Equation (Eq. 1) exemplifies, in a non-limiting manner, the specified steps 601-605.
By way of non-limiting example, the specified Equation (Eq. 1) exemplifies in a non-limiting manner the specified steps 601-605 and the MTE criterion may be met if the measured and desired values match, or when the missile is ejected from the canister.
Turning to FIG. 7, this illustrates schematically a simplified chart comparing canister configuration with and without utilization of a technique in accordance with certain embodiments of the presently disclosed subject matter.
Before moving on, note that the solid line graphs 703, 704, 706 and 707 in charts 710, 720, 730 and 740, respectively indicate, as will be explained in detail below, the behaviour of the canister (angle and angular rate), as well as the missile flying inside the canister (angle and angular rate) in an unsupervised mode of operation, i.e. without utilizing the technique in accordance with certain embodiments of the presently disclosed subject matter. The hashed line graphs 7005, 7003, 7007 and 7011 (in charts 710, 720, 730 and 740, respectively) indicate, as will be explained in detail below, the behaviour of the canister (angle and angular rate), as well as the missile flying inside the canister (angle and angular rate) when utilizing the technique in accordance with certain embodiments of the presently disclosed subject matter, e.g. in accordance with Eq. 1 described above.
Bearing this in mind, and as shown by oscillating graph 703 (in chart 710), an unsupervised angular position of the canister stems e.g. from an unsupervised angular rate thereof see graph 704 in chart 720 (wherein the ordinate represents angular rate).
It is noted that the oscillating angular position of the canister by no means converges to the desired angle position 902 indicated by straight line n chart 910.
The angle and the rate of the missile ( charts 730 and 740, respectively) substantially follow suit. Namely, the angle (see graph 706 in chart 730) and angular rate (see graph 707 in chart 740) of the missile flying inside (and constrained by) the canister follow more or less the respective angle (graph 703) and angular rate (graph 704) of the canister (excluding some lateral degree of freedom of the missile inside the canister—as shown for instance by interferences 708 and 709).
The net effect is that, at the point of ejection, when the missile departs from the canister (see 7001 in chart 730), the missile has a certain angular rate above 0 (7002 in chart 740) which results in an ever-increasing angle 7010 while flying in the boost phase, thereby intensifying the undue tip-off effect.
In contrast, and as readily arises from graph 7003, by following the sequence of operation (e.g. in accordance with FIG. 6—for instance in compliance with Eq. 1—utilizing canister sensor(s)), the angular rate of the canister will coincide with the desired angular rate of the canister, e.g. 0, while the actual angle 7005 coincides with the desired angle 702. The missile angular rate will substantially follow suit (graph 7011 in chart 740) and coincides with the desired angular rate 7006 (in chart 740), e.g. 0, while the actual missile's angle coincides (matches) with the desired missile's angle (7007 and 7008 of chart 730).
The net effect is that unlike the variable angular position of the missile (7010 in chart 730) in the unsupervised mode of operation, in accordance with certain embodiments of the invention, by virtue of the desired angular rate (e.g. 0—see 7006 in chart 740) the missile's angular position will retain the desired angular position after departing from the canister, e.g. 0 (see 7009 in chart 730) (constituting an example of meeting the specified MTE control criterion, when the desired and measured value match, or when the missile ejects from the canister, thereby substantially reducing or eliminating the tip-off effect.
Note that in the latter example, the measured canister's state embraces measured canister angle and angular rate, and the desired canister's state embraces desired canister angle and angular rate.
The equation below describes, by way of yet another non-limiting example, the actuation command to the canister actuator, and assumes, for simplicity, that canister sensor(s) and missile sensors are utilized.
$\begin{matrix} M_{c} = - K_{c a n i s t e r} \cdot (I_{z z_{canister}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q_{caniste r} - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot (θ_{c a n i s t e r} - θ_{c o m}))) + - K_{m i s s i l e} \cdot (I_{z z_{canister}} \cdot (\begin{matrix} 2 \cdot ξ \cdot ω_{n} \cdot (q_{m i ssile} - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot \\ (θ_{missile} - θ_{c o m}) \end{matrix})) & Eq 2. \end{matrix}$
Where:
M_c—an actuation command to the canister's actuator for modifying the angular position and the angular rate of the canister.
K_canister—normalizing gain for the canister
K_missile—normalizing gain for the missile
Izz_canister—canister moment of inertia around perpendicular to missile ideal ejection direction
ξ—desired closed loop damping coefficient
ω_n—desired natural frequency mode
K_canister—canister stiffness
q_canister—measured canister angular rate
q_missile—measured missile angular rate
{dot over (θ)}_com—desired canister angular rate θ_canister—measured canister angle
θ_missile—measured missile angle
θ_com—desired canister angle
Note, that the measured canister angle θ_canistermay be obtained from the canister's sensor and the measured canister's angular rate q_canistermay be measured or processed therefrom.
Note also that the measured missile angle θ_canistermay be obtained from the canister's sensor and the measured canister's angular rate q_missilemay be measured or calculated therefrom.
Note also that the desired canister angle θ_comis obtained (received or calculated) and the desired {dot over (θ)}_comcanister angular rate may be received or calculated therefrom.
It is thus noted that whenever a reference is made to “measured” e.g. angle or rate, it encompasses also processing.
Similarly to Eq. 1 described above, note that the resulting activation command M_cthat is fed to the canister actuator will result in modification of its angular position (angle and possibly rate). In the latter example illustrated with reference to Eq. 1, both the measured angular rate q and the angle θ_canisterare controlled in the sense that the activation command will be nulled in the case that both the rate and angle will match their corresponding desired values {dot over (θ)}_comand θ_comand also when the measured angle and angular rate of the missile will match the corresponding desired angle and angular rate of the canister. The latter conditions, if met, exemplify meeting the MTE control criterion.
In accordance with certain other embodiments, only the angle is controlled (constituting a different MTE control criterion), e.g. θ_canister(measured) vs. θ_com(desired) and θ_missile(measured) vs. θ_com(desired), yielding possibly a different flight trajectory of the missile for eliminating or reducing the MTE effect. The latter are obviously only non-limiting examples for overcoming the MTE effect. These examples are not limiting (e.g. only the rate of either or both or the missile and the canister are controlled; the missile measured angle may be compared to the missile's desired angle rather than to the canister's desired angular position, and, similarly, the measured and desired rates of the missile are compared; and/or other parameters for control may be added or modified, all depending upon the particular application.
Those versed in the art will readily appreciate that in accordance with certain embodiments, the MTE control criterion may be changed depending upon some or all of the parameters that are measures and/or controlled.
As readily arises from the equation above, there are various coefficients (including in the non-limiting example above: K, Izz_canister, ξ, ω_n, K_canister, K_missile) and the command M_cis based by this example on the difference between the actual canister angle and the desired one, as well as on the difference between the respective rates, and, by the same token, on the difference between the measured missile angle and the desired canister angle, as well as on the difference between the respective rates.
Note that the other coefficients (e.g. K) may also affect the missile trajectory as it ejects from the canister for coping with the MTE effect, all depending upon the particular application.
Note also that the control may cease in case the MTE control criterion is met. This criterion may be met in case that the desired and measured controlled parameters (e.g. angular position and/or rate) match, or when the missile ejects from the canister, or when the command to the actuators violates system specifications (e.g. is overly large to the extent that following it may damage the canister and/or missile.
Note also that the specified equation is by no means binding. Thus, for example, in accordance with certain embodiments, using K_canisterand K_missileone can choose how to incorporate the amount of data fusion between the two sensors. By assigning K_missileto be zero, the algorithm will use data only from the canister, and by assigning K_canisterto be zero, the algorithm will use data only from the missile. Any other combination will fuse data from both of the sensors.
Referring to FIG. 8, there is illustrated a generalized flow chart of a sequence of operations in accordance with certain embodiments of the presently disclosed subject matter. The specified Eq. 2, illustrates a non-limiting example of the specified sequence of operations.
Thus, in step 801, data indicative of desired canister state (e.g. desired canister's angle and angular rate) is received in response to a launch command.
Then, until an MTE control criterion is met (802,803):

- Data indicative of measured canister state (e.g. measured canister's rate and angle, as well as measured missile's angle and angular position) is received from at least one sensor associated with the canister (804);
- Thereafter, the data indicative of measured canister state and desired canister state is processed (e.g. in compliance with Eq. 2), for outputting data indicative of a command to at least one actuator associated with the canister, for modifying at least the angular position of the canister 805.

Note that the command may be issued based on e.g. at least one of: angular position of the canister (measured and desired), angular position of the missile (measured and desired), angular rate of the canister (measured and desired), angular rate of the missile (measured and desired); possibly other parameters, such as for instance, the position of the missile within the canister, remaining flight duration of missile within the canister having a more accurate control (e.g. applied by way of non-limiting example mutatis mutandis to Equation 1 or 2—see below), and others.
As specified above, control may cease in case of a MTE control criterion being met. This criterion may be met also e.g. when the missile ejects from the canister, or e.g. when the command to the actuators violates system specifications (e.g. is overly large to the extent that following it may damage the canister and/or missile).
By way of non-limiting example, the specified Equation (Eq. 2) exemplifies, in a non-limiting manner, the specified steps 801-805.
The same modifications apply mutatis mutandis to the sequence of operations described with reference to FIG. 6.
Turning to FIG. 9, this illustrates schematically a simplified chart comparing canister configuration with and without utilization of a technique in accordance with certain embodiments of the presently disclosed subject matter.
Before moving on, note that the solid line graphs 903, 904, 906 and 907 in charts 710, 720, 730 and 740, respectively indicate, as will be explained in detail below, the behaviour of the canister (angle and angular rate) as well as the missile flying inside the canister (angle and angular rate) in an unsupervised mode of operation, i.e. without utilizing the technique in accordance with certain embodiments of the presently disclosed subject matter. The hashed line graphs 9005, 9003, 9007 and 9011 (in charts 910, 920, 930 and 940, respectively) indicate, as will be explained in detail below, the behaviour of the canister (angle and angular rate) as well as the missile flying inside the canister (angle and angular rate) when utilizing the technique in accordance with certain embodiments of the presently disclosed subject matter, e.g. in accordance with Eq. 2 described above.
Bearing this in mind, and as shown by oscillating graph 903 (in chart 910), an unsupervised angular position of the canister stems e.g. from an unsupervised angular rate thereof see graph 904 in chart 920 (wherein the ordinate represents angular rate).
It is noted that the fluctuating angle of the canister by no means converges to the desired angle 902 indicated by straight line n chart 910.
The angle and the rate of the missile ( charts 930 and 940, respectively) substantially follow suit. Namely, the angle (see graph 906 in chart 930) and angular rate (see graph 907 in chart 940) of the missile flying inside (and constrained by) the canister follow more or less the respective angle (graph 903) and angular rate (graph 904) of the canister (excluding some lateral degree of freedom of the missile inside the canister—as shown for instance by interferences 908 and 909).
The net effect is that at the point of ejection, when the missile departs from the canister (see 9001 in Chart 930), the missile has a certain angular rate above 0 (9002 in chart 940) which results in an ever increasing angle 9010 while flying in boost phase, thereby intensifying the undue tip-off effect.
In contrast, and as readily arises from graph 9003, by following the sequence of operation (e.g. in accordance with FIG. 8—for instance in compliance with Eq. 2—utilizing canister sensor(s) and missile sensors(s)), the angular rate of the canister will coincide with the desired angular rate of the canister, e.g. 0, while the actual angle 9005 coincides with the desired angle 902. The missile angular rate will substantially follow suit (graph 9011 in chart 940) and substantially coincides with the desired canister rate 9006 (in chart 940), e.g. 0, while the measured missile's angle coincides with the desired canister angle (9007 and 9008 of chart 930).
Note incidentally that in accordance with certain embodiments, there are minor fluctuations (e.g. graph 9011 around 9006, and 9007 around 9008), stemming from the fact that the missile motion is measured, and, based thereon, the canister's actuators are controlled.
The net effect is that unlike the variable angular position of the missile (9010 in chart 930) in the unsupervised mode of operation, in accordance with certain embodiments of the invention, by virtue of the desired angular rate (e.g. 0—see 9011 in chart 940) the missile's angle will retain the desired angle after departing from the canister, e.g. 0 (see 9009 in chart 930, IF 9011 9009), thereby substantially reducing or eliminating the tip-off effect.
It is noted that the teachings of the presently disclosed subject matter are not bound by the flow chart illustrated in FIGS. 8 and 9 and that the illustrated operations can occur out of the illustrated order. It is also noted that whilst the flow chart is described with reference to control system (301), this is by no means binding, and the operations can be performed by elements other than those described herein.
It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.
It will also be understood that the system according to the invention may be, at least partly, implemented on a suitably programmed computer. Likewise, the invention contemplates a computer program being readable by a computer for executing the method of the invention. The invention further contemplates a non-transitory computer-readable memory tangibly embodying a program of instructions executable by the computer for executing the method of the invention.
Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.

Claims

1. A method for reducing or eliminating “Missile Tip-off Effect” (MTE) of a missile ejected from a canister comprising, by a processor and associated storage:

a. receiving data indicative of desired canister state in response to a launch command,

perform repeatedly until an MTE control criterion is met:

b. receiving, from at least one sensor associated with the canister, data indicative of measured canister state;

c. processing at least said data indicative of measured canister state and desired canister state, for outputting data indicative of a command to at least one actuator associated with the canister for modifying at least the angular position of the canister;

thereby reducing or eliminating said (MTE) effect.

2. The method according to claim 1, wherein said measured canister state includes measured canister angle and wherein desired canister state includes desired canister angle.

3. The method according to claim 1 or 2, wherein said measured canister state includes measured canister rate and wherein desired canister state includes desired canister rate.

4. The method according to claim 3, wherein said processing for outputting data indicative of said command complies with Equation 1:

M_{c} = - K \cdot (I_{z z_{c a n i s t e r}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot (θ_{canist e r} - θ_{c o m})))

5. The method according to any one of the preceding claims, wherein said measured canister state includes measured missile angle and wherein desired canister state includes desired canister angle.

6. The method according to claim 3, wherein said measured canister state includes measured missile rate and wherein desired canister state includes desired canister rate.

7. The method according to claim 6, wherein said processing for outputting data indicative of said command complies with Equation 2:

M_{c} = - K_{canister} \cdot (I_{z z_{c a n i s t e r}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q_{c a n i s t e r} - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot (θ_{canist e r} - θ_{c o m}))) + - K_{m i ssile} \cdot (I_{z z_{c a n i s t e r}} \cdot (2 \cdot ξ \cdot ω_{n} \cdot (q_{missile} - {\dot{θ}}_{c o m}) + (ω_{n}^{2} - \frac{K_{c a n i s t e r}}{I_{z z - c a n i s t e r}}) \cdot (θ_{m i s s i l e} - θ_{c o m})))

8. The method according to any one of the preceding claims, wherein the larger the difference between the desired canister state and the measured canister state, the larger is said command.

9. The method according to any one of the preceding claims, wherein said measured canister state includes data indicate of remaining flight time of the missile in the canister, such that for the same difference in measured angle or rate vs. desired angle or rate, the shorter the remaining flight time, the larger the command.

10. The method according to any one of the preceding claims, further comprising modifying on-the-fly said data indicative of desired canister state.

11. The method according to any one of the preceding claims, wherein at least one of said sensors is fitted on the canister.

12. The method according to any one of the preceding claims, wherein at least one of said sensors is fitted on the missile.

13. The method according to any one of the preceding claims, further comprising an array of canisters.

14. The method according to claim 13, wherein said data indicative of measured canister state is obtained by averaging the data indicative of the canister state of each canister of said array.

15. A system for reducing or eliminating “Missile Tip-off Effect” (MTE) of a missile ejected from a canister comprising, a processor and associated storage configured to:

receiving data indicative of desired canister state in response to a launch command, perform repeatedly until an MTE control criterion is met:

a. receiving, from at least one sensor associated with the canister, data indicative of measured canister state;

b. processing at least said data indicative of measured canister state and desired canister state, for outputting data indicative of a command to at least one actuator associated with the canister for modifying at least the angular position of the canister;

thereby reducing or eliminating said (MTE) effect.

16. A non-transitory computer-readable memory tangibly embodying a program of instructions executable by the processor for executing the method of any one of claims 1 to 14.