Analytical Guidance Laws and Integrated Guidance/Autopilot for Homing Missiles

An approach to integrated guidance/autopilot design is considered in this study. It consists of two parts: 1) recognizing the importance of polar coordinates to describe the end game in terms of problem description and measurement acquisition, the terminal guidance problem is formulated in terms of polar coordinates; 2a) through the use of the state transition matrix of the intercept dynamics, a closed form solution for the transverse command acceleration is obtained; and 2b) through a commonly used approximation on time-to-go and a coordinate transformation, a family of proportional navigation optimal guidance laws is obtained in a closed form. A typical element of such a guidance law is combined with the autopilot dynamics to result in a feedback control law in terms of output variable

Approximate Analytical Guidance Schemes for Homing Missiles

Closed form solutions for the guidance laws are developed using modern control techniques. The resulting two-point boundary value problem is solved through the use of the state transition matrix of the intercept dynamics. Results are presented in terms of a design parameter

Spacecraft Position and Attitude Control with Theta-D Technique

A new optimal control approach, Theta-D technique, is employed to control the position and altitude of a spacecraft accurately m order to capture and remove large space targets. Spacecrafts are required to be able to perform large position and angle maneuvers: their dynamics are highly nonlinear. To control this highly nonlinear dynamic system, we formulate it as a nonlinear optimal regulator problem. The proposed Theta-D technique can give an approximately closed-form suboptimal controller in the sense that it obtains an approximate solution to the Hamilton-Jacobi-Bellman (HJB) equation through a perturbation method. By adjusting perturbation terms, asymptotic stability can be achieved in the large and the system transient performance can also be tuned in a flexible way. Compared with the popular SDRE technique, this approach does not need on-line computations of algebraic Riccati equation. With high-dimensioned systems, this feature presents a tremendous implementation advantage. A six degree of freedom simulation of the spacecraft and target are used to demonstrate the effectiveness of the Theta-D controller

Nonlinear Bank-To-Turn / Skid-To-Turn Missile Outer-Loop / Inner-Loop Autopilot Design with Θ - D Technique

In this paper, a new nonlinear control method is used to design a full-envelope, hybrid bank-to-turn (BTT)/skid-to-turn (STT) autopilot for an air-breathing air-to-air missile. Through this new approach, called the θ − D method, we find approximate solutions to the Hamilton- Jacobi-Bellman (HJB) equation. An interesting and important feature of this new technique is that the nonlinear feedback law can be expressed in a closed form. In this autopilot design, a θ − D outer-loop and inner-loop controller structure is adopted. A hybrid BTT/STT autopilot command logic is used to convert the commanded accelerations from the guidance laws to reference angle commands for the autopilot. The outerloop θ − D controller converts the angle-of-attack, the sideslip, and the bank angle commands to body rate commands for the inner loop. An inner-loop θ − D nonlinear controller converts the body rate commands to fin commands. The nonlinear design is evaluated using a detailed six-degrees-of-freedom simulation. Simulation results show that the new controllers achieve excellent tracking performance and exhibit insensitivity to parameter variations over a wide flight envelope

Nonlinear Missile Autopilot Design with Θ - D Technique

In this paper, a new nonlinear control method is used to design a full-envelope, hybrid bank-to-turn (BTT)/skidto- turn (STT) autopilot for an air-breathing air-to-air missile. Through this new approach, called the θ − D method, we find approximate solutions to the Hamilton- Jacobi-Bellman (HJB) equation. An interesting and important feature of this new technique is that the nonlinear feedback law can be expressed in a closed form. In this autopilot design, a θ − D outer-loop and inner-loop controller structure is adopted. A hybrid BTT/STT autopilot command logic is used to convert the commanded accelerations from the guidance laws to reference angle commands for the autopilot. The outerloop θ − D controller converts the angle-of-attack, the sideslip, and the bank angle commands to body rate commands for the inner loop. An inner-loop θ − D nonlinear controller converts the body rate commands to fin commands. The nonlinear design is evaluated using a detailed six-degrees-of-freedom simulation. Simulation results show that the new controllers achieve excellent tracking performance and exhibit insensitivity to parameter variations over a wide flight envelope