초록 ▼

Higher Order Sliding Mode (HOSM) control techniques are applied to the Guidance Control (G&C) of interceptor missile in which velocity may be steered by combination of main thrust, aerodynamic lift and lateral on-off divert thrusters, and attitude may be steered by continuous or on-off actuators. Me

Higher Order Sliding Mode (HOSM) control techniques are applied to the Guidance Control (G&C) of interceptor missile in which velocity may be steered by combination of main thrust, aerodynamic lift and lateral on-off divert thrusters, and attitude may be steered by continuous or on-off actuators. Methods include the pointing of the seeker, its associated estimation processes, a guidance law that uses concurrent divert mechanisms, and an attitude autopilot. The insensitivity of the controller to matched disturbances allows the concurrent usage of the divert mechanisms without adverse effect on the accuracy. The controller also allows the de-coupling of the control of roll, pitch and yaw channels, and usage quaternions to represent body attitude and it provides control perfect robustness. While it conceivable to design separately the components of the G&C method, it is widely accepted that designing them in an integrated fashion usually produces a better result.

대표청구항 ▼

1. A system for guiding a missile to intercept a target comprising: a target sensor providing line of sight information relating to a position of said target relative to said missile;an inertial measuring unit providing inertial states of said missile;an attitude autopilot controlling said missile a

1. A system for guiding a missile to intercept a target comprising: a target sensor providing line of sight information relating to a position of said target relative to said missile;an inertial measuring unit providing inertial states of said missile;an attitude autopilot controlling said missile attitude;a guidance processor, said guidance processor having a memory containing processing instructions for guiding said missile to said target based on said line of sight information and said inertial states of said missile; said processing instructions including a high order sliding mode control process wherein said high order sliding mode control process enforces a guidance strategy for guiding said missile to intercept said target; said guidance processor generating a total lateral divert acceleration command;at least one lateral divert actuator receiving said total lateral divert command and producing a primary lateral acceleration component directly responsive to said total lateral divert acceleration command;said attitude autopilot receiving said total lateral divert acceleration command and producing a secondary lateral acceleration component in accordance with said total lateral divert acceleration command; said primary lateral acceleration component and said secondary lateral acceleration command cooperating to produce a total acceleration corresponding to said total lateral divert command;said primary lateral acceleration component and said secondary lateral acceleration cooperate to produce a total acceleration corresponding to said total lateral divert acceleration command wherein said total lateral divert acceleration command is derived based on said high order sliding mode control process;wherein said secondary acceleration component is accommodated in said sliding mode control process as a cooperative component of bounded disturbance that reduces an upper Lipschitz bound of initial disturbance. 2. The system in accordance with claim 1, wherein said a least one lateral divert actuator does not require orienting body attitude to produce said primary lateral acceleration component and said autopilot utilizes a secondary divert actuator that does require orienting body attitude to produce said secondary lateral acceleration component. 3. The system in accordance with claim 2, wherein said at least one lateral divert actuator is a lateral actuator producing lateral force proximal to a center of gravity of said missile to divert said missile laterally with minimal change in an angle of attack. 4. The system in accordance with claim 3, wherein said lateral actuator may be a continuous actuator such as moving control surface, proportional divert thruster or an on-off thruster with a pulse width modulation duty cycle of said on off thruster; commanded lateral thrust is established in accordance with said total lateral divert acceleration command. 5. The system in accordance with claim 3, wherein said high order sliding mode control process comprises a sliding variable in accordance with: {dot over (σ)}(.)=f(.)+g(.)− bΔ(.);(.)=pitch, yaw;wherein said total lateral acceleration designed to drive the sliding variable to zero, that is to the sliding surface is: Δ(.)=1b_⁢{f^(.)+α1⁢σ(.)2/3⁢sign⁡(σ(.))+α2⁢∫σ(.)1/3⁢sign⁡(σ(.))⁢ⅆτ}. 6. The system in accordance with claim 5, wherein said attitude autopilot concurrently acts to set an angle of attack to achieve said secondary lateral acceleration, wherein said secondary acceleration reduces a said disturbance in accordance with: g2(.)=g(.)−ΔΓ(.); |g2(.)|ɛ0ifJ+d⁡(t)≤ɛρ(.)⁢0ifJ+d⁡(t)tgom⁢⁢a⁢⁢xω=1tgo⁢if⁢⁢tgom⁢⁢i⁢⁢n≤tgo≤tgom⁢⁢a⁢⁢x, where V⊥(.) and ZT⊥(.) represent respectively target relative velocity and position with respect to boresight and tgomax and tgomin relate to achieving a time to intercept and to avoiding excessive gains during initial flight. 31. The system in accordance with claim 28, wherein said dynamics of said sliding surface is represented by: {dot over (σ)}=f(t)+u, σ∈where u represents commanded lateral acceleration and unknown, bounded disturbing term f(t) represents unknown dynamical effects; which can be separated into target acceleration Γ⊥(.)T and other terms η(.) as f⁡(t)=Γ⊥(.)T+η(.)={Γ⊥(.)T+V⊥(.)tgomin-V⁢λ.if⁢⁢tgotgomaxwhere η(.) represents the terms other than target acceleration that are compensated explicitly; here target acceleration Γ⊥(.)T is either estimated by an external observer as {circumflex over (Γ)}1⊥(.)T, or as {circumflex over (Γ)}2⊥(.)T calculated by an observer embedded with guidance which not only estimates target acceleration but effects of disturbance terms such as errors in terms V⊥(.), tgo and V∥{dot over (λ)}, and the guidance controller is given by: {u(.)=Γ^⊥(.)T+η^(.)-α1⁢σ(.)2/3)⁢sign⁡(σ(.))+ww.=-α2⁢σ(.)1/3⁢sign(σ(.));⁢(.)=normal⁡(Z),transversal⁡(Y)Γ^⊥(.)T=sel⁡(Γ^⁢⁢1⊥(.)T,Γ^⁢2⊥(.)T). 32. The system in accordance with claim 31, wherein the estimation target acceleration {circumflex over (Γ)}2⊥(.)T is achieved for targets with estimated frequency of maneuvers ≦0.8 Hz by a smooth observer described by:  {z.0=v0+uv0=-2⁢L1/3⁢z0-σ2/3⁢⁢sign⁡(z0-σ)+z1z.1=v1v1=-1.5⁢L1/2⁢z1-v01/2⁢⁢sign⁢⁢(z1-v0)+z2z.2=-1.1⁢Lsign⁡(z2-v1)z1→Γ2⊥(.)T⁢⁢before⁢⁢intercept. 33. The system in accordance with claim 28, when the estimated frequency of target maneuvers is >0.8 Hz wherein target acceleration {circumflex over (Γ)}2⊥(.)T is estimated using an unsmooth observer described by:  {z.0=v0+uv0=-1.5⁢L1/2⁢z0-σ1/2⁢sign⁡(z0-σ)+z1z.1=-1.1⁢Lsign⁡(z1-v0)z1→Γ2⊥(.)T⁢⁢before⁢⁢intercept. 34. The system in accordance with claim 28, wherein the dynamics of the sliding surface is: {dot over (σ)}(.)+α1|σ(.)|2/3 sign(σ(.))+α2∫|σ(.)|1/3 sign(σ(.))dτ={tilde over (Γ)}⊥(.)T+{tilde over (η)}(.)=g(.) and the controller is: {u(.)=Γ^⊥(.)T+η^(.)-α1⁢σ(.)2/3)⁢sign⁡(σ(.))+ww.=-α2⁢σ(.)1/3⁢sign(σ(.));Γ^⊥(.)T=sel⁡(Γ^⁢⁢1⊥(.)T,Γ^⁢2⊥(.)T)where (.)=normal(Z) or transversal(Y). 35. A system for guiding a missile to intercept a target comprising: an optical target sensor providing line of sight information relating to a position of said target relative to said missile;a target state estimator responsive to said line of sight information, said target state estimator generating target dynamic state estimates;an inertial measuring unit providing inertial states of said missile;a guidance processor, said guidance processor having a memory containing processing instructions for guiding said missile to said target based on target dynamic state estimates and said inertial states of said missile; said guidance processor generating a divert acceleration command;a lateral control system responsive to said divert acceleration command for controlling said missile in accordance with said divert acceleration command;wherein said optical target sensor includes a boresight directing process based on a high order sliding mode control having a sliding surface that maintains said position of said target within a field of view of said optical target sensor. 36. The system as recited in claim 35, wherein the optical target sensor includes a focal plane array mounted fixed in relation to a missile body reference for said missile, and a moving mirror is used to direct said field of view of said optical target sensor. 37. The system as recited in claim 36, wherein a slewing function is designed to track the seeker boresight in the direction of the target Line-Of-Sight; this is achieved by steering a moving mirror such that the center or any other point in the target image remains centered on the focal plane array in the presence of target and interception lateral motion and interceptor attitude motion; a quaternion representing the transformation from bore-sight-axes LOS to Earth Centered Inertial Intertial reference is represented by: QBoreECI=(∫[00-ϛ.-υ.00υ.-ϛ.ϛ.-υ.00υ.ϛ.00]⁢QBodyBore⁢ⅆt)⁢QBoreECI where ζ,ν are the rotations in pitch and yaw respectively. 38. The system as recited in claim 37, wherein the slewing of the boresight line is achieved using a nonlinear filter with pulse width modulation controller described by:  {χ.(.)=⁢ξ(.)⁢σ(.)0.5⁢sign⁡(σ(.))-η(.)⁢J(.)0.5⁢sign⁡(J(.));⁢(.)=p,q,rJ(.)=⁢χ(.)+σ(.);u[.]=⁢F(.)⁡(J(.),d(.)⁡(t));⁢[.]=l,m,nwhere F(.)⁡(J(.),d(.)⁡(t))={-ρ(.)⁢0ifJ+d⁡(t)>ɛ0ifJ+d⁡(t)≤ɛρ(.)⁢0ifJ+d⁡(t)<ɛ, where d(t) represents a dither signal, and u(.) are pulse width modulation torque rate commands. 39. The system as recited in claim 35, wherein the sensor includes a focal plane array mounted on a gimbaled platform and the gimbaled platform is moved to direct the field of view of the optical array. 40. The system as recited in claim 39, wherein a slewing function is designed to track the seeker boresight in the direction of the target Line-Of-Sight; this is achieved by orienting the platform such that the center or any other point in the target image remains centered on the focal plane array in the presence of target and interception lateral motion and interceptor attitude motion; a quaternion representing the transformation from bore-sight-axes LOS to an Earth Centered Intertial Inertial reference is represented by: QBoreECI=∫[00-ϛ.-υ.00υ.-ϛ.ϛ.-υ.00υ.ϛ.00]⁢QBoreECI⁢ⅆt where ζ,ν are the rotations in pitch and yaw respectively. 41. The system as recited in claim 35, wherein a fourth order sliding mode observer is used to estimate target relative velocity orthogonal to boresight and target acceleration orthogonal to boresight, said fourth order observer being described by:  {ɛ.^(.)=v0⁢(.);⁢(.)=pitch,yaw;⁢⁢ɛ(.)=normal/transversal⁢⁢target⁢⁢pos⁢⁢w/r⁢⁢boresightv0⁢(.)=-5⁢⁢L1/5⁢ɛ^(.)-ɛ_4/5⁢sign⁡(ɛ^(.)-ɛ_(.))+V^⊥(.)-Ω_(.)⁢r,V.^⊥(.)=v1⁢(.),v1⁢(.)=-3⁢⁢L1/4⁢V^⊥(.)-Ω_(.)⁢r-v0⁢(.)3/4⁢sign⁡(V^⊥(.)-Ω_(.)⁢r-v0⁢(.))+a^(.)T-a_(.)M,a.^(.)T=v2⁢(.)v2⁢(.)=-2⁢⁢L1/3⁢a^(.)T-a_(.)M-v1⁢(.)2/3⁢sign⁡(a^(.)T-a_(.)M-v1⁢(.))+z3⁢(.)z.3⁢(.)=v3⁢(.)v3⁢(.)=-1.5⁢⁢L1/2⁢z3⁢(.)-v2⁢(.)1/2⁢sign⁡(z3⁢(.)-v2⁢(.))+z4⁢(.)z.4⁢(.)=v4⁢(.),v4⁢(.)=-1.1⁢⁢L⁢⁢sign⁡(z4⁢(.)-v3⁢(.)). 42. The system as recited in claim 41, wherein residual disturbing dynamical effects {tilde over (Ω)}(.)=Ω(.)− Ω(.) and a ã⊥(.)M=a⊥(.)M−ā⊥(.)M are accommodated within a disturbance bound in accordance with said Lipshitz constant L.