Midcourse Guidance Law Research Articles

Real-Time Midcourse Guidance Robust to Missile Launch Conditions

In this paper, an real-time suboptimal midcourse guidance law robust to missile launch conditions, which is a neural network approximation of the optimal feedback strategy, is proposed. It is obtained by the appropriate representation of input data of the neural network, which guarantees robustness. Computer simulations show that the proposed guidance law allows the missile to intercept a given target almost exactly with only a limited number of the neural network weights.

Real-time midcourse guidance with intercept point prediction

In this paper, an on-line suboptimal midcourse guidance law, which is a neural-network approximation of the optimal feedback strategy, is proposed to eliminate the need for solving two-point boundary-value problems in real time. Moreover, for intercept point prediction, a fast converging, iterative algorithm based on a neural network time-to-go estimator is devised. Computer simulations confirm that the closed-loop behavior of the proposed guidance law is so close to the optimal trajectory that it outperforms nonoptimal guidance laws such as g-biased proportional navigation.

Midcourse guidance for a short-range attack missile using error compensation

A midcourse guidance law is developed for a short range attack missile of the SRAM I1 class which has a very high thrust-teweight ratio. The optimal control formulation is to minimize the flight time from a low altitude, subsonic launch to a fixed ground target 100 300 nm from the launch aircraft at any azimuth. An approximate optimal guidance law is developed by neglecting the aerodynamics and creating burnout conditions which enable the zero angle of attack coast to get close to the target. Simultaneously, error compensation terms are included in the state differential equations and final conditions that lead to a control law which can be tuned to improve the performance of the missile and enable it to hit the target. The error compensation weights are obtained by solving the true optimal control problem numerically. In practice, weights could be stored for each target range and azimuth and obtained from a table.

Analysis of optimal midcourse guidance law

An optimal midcourse guidance law is presented that maximizes the final speed for missiles against a target at far distance or at low attitude in which the final speed is a prime factor. An explicit acceleration command is derived analytically in which the trajectory-dependent optimal control gains are written in terns of thrust, lift, drag, and intercept boundary condition. The optimal guidance law can be implemented either in airframe coordinates or inertia coordinates. It is shown that the acceleration commands with constant control gain are adequate when the range is relatively short; during midcourse guidance, however, the optimal control gains are required to enhance the performance.

Guidance law for hypersonic gliders based on piecewise constant control

A midcourse guidance law is developed for the descent of a hypersonic glider, initially in level flight, to a fixed target on the ground. It is based on an optimal piecewise constant control (N intervals) obtained from an approximate physical model (flat Earth, exponential atmosphere, parabolic drag polar, etc). The resulting optimal control equations can be integrated either analytically or by quadrature, and the guidance algorithm requires the solution of 2N + nonlinear algebraic equations. The guidance law is implemented in a realistic glider simulation, the intercept is achieved, and final velocities within 14% of the true values are obtained for the downrange and crossranges considered.

Optimal midcourse guidance for medium-range air-to-air missiles

An advanced midcourse guidance law for medium-range air-to-air missiles is proposed. The law consists of two different guidance modes: the final velocity maximum or the final time minimum, depending on the initial missile-target geometry. The former is preferable against a highly maneuverable target at a great distance, whereas the latter is demanded against a near target. This midcourse guidance law is combined with augmented proportional navigation in the homing phase. Performance is evaluated by computer simulations against conventional and advanced targets. The results show that the proposed guidance law is far superior to the guidance law that employs only augmented proportional navigation throughout the interception course, in regard to extending the launch boundaries or minimizing the interception time.

Near-optimal midcourse guidance for air-to-air missiles

Singular perturbation theory is used to derive a near-optimal mid-course guidance law incorporating a linear combination of flight time and terminal specific energy as the performance index. State variables in the slow time-scale model consist of down range, cross range, specific energy, and heading angle. A near-optimal approach using feedback linearization is developed to account for altitude and flight-path-angle dynamics neglected in the slow time-scale solution. Implementation logic and simulation results for an engagement scenario are given.

Reduced-order pulse-motor ignition control logic

The higher total impulse and energy management potential available in a pulse motor can be exploited with optimal guidance and propulsion control methods to improve missile performance. Under the assumptions of same propellant formulation and similar grain configuration of the pulses, a pulse motor can generally deliver higher specific impulse than its boost-sustain counterpart, leading to higher total impulse with the same launch weight despite a weight penalty on the pulse motor due to barrier insulation and an additional igniter; moreover, the pulse motor also allows arbitrary pulse delays between pulses. To fully exploit such energy management capabilities requires a real-time on-board pulse ignition controller. This paper studies the pulse ignition problem for a generic medium-range air-to-air missile from an optimal control viewpoint, using a minimum flight-time performance index. To make real-time mechanization feasible with state-of-the-art microprocessors, the optimal control solution is reduced to an implementable algorithm using singular-perturbation arguments and engineering approximations for the midcourse guidance problem. The resulting ignition control used in conjunction with the midcourse guidance law is then shown to command pulse ignition within the desirable period, leading to significant performance improvement over the boostsustain motor.