Vincent C. Lam

Bio: Vincent C. Lam is an academic researcher from Raytheon Missile Systems. The author has contributed to research in topics: Trajectory & Constraint (information theory). The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

Circular Guidance Laws With and Without Terminal Velocity Direction Constraints

Abstract: Two circular guidance laws have been developed based on a 3-D vector approach: one circular guidance law without terminal velocity direction constraint and the other circular guidance law with terminal velocity direction constraint. Both approaches can be implemented easily with predictable time to go and trajectory. They are effective for both stationary and moving targets.

Optimal guidance of extended trajectory shaping

Abstract: To control missile’s miss distance as well as terminal impact angle, by involving the time-to-go-nth power in the cost function, an extended optimal guidance law against a constant maneuvering target or a stationary target is proposed using the linear quadratic optimal control theory. An extended trajectory shaping guidance (ETSG) law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile’s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.

A New Method for Initial Parameters Optimization of Guided Projectiles

Abstract: A new algorithm was developed for the initial parameters optimization of guided projectiles with multiple constraints. Due to the relationship between the analytical guidance logic and state variables of guided projectiles, the Radau pseudospectral method was used to discretize the differential equations expressed by control variables and state variables with multiple constraints into series algebraic equations, only expressed by state variables. The initial parameter optimization problem was transformed to a nonlinear programming problem, and the sequential quadratic programming algorithm was used to obtain the optimal combinations of initial height and range to target, and make the final velocity of guided projectiles maximum with constraints. Comparing with the appropriate initial conditions solved by Monte Carlo method and the flight characteristics solved by integrating the original differential equations in the optimal initial parameters computed by the new algorithm, the feasibility of new algorithm was validated.

Geometrical guidance algorithm for soft landing on lunar surface

Abstract: Augmented design of a guidance algorithm previously developed for intercepting target in a missile-target engagement scenario, but catering to powered descent soft landing on lunar surface is the main focus of this paper. When it comes to lunar soft landing guidance formulation, it is required that the Lander reach the desired position with terminal velocity constraints. An existing circular guidance law developed for missile guidance is modified to be applied for the fine braking phase of lunar powered descent. Presently in the algorithm, at the beginning of each guidance cycle, there will be an assumed varying circular path from missile to target and the guidance solution lies in finding the acceleration towards the centre of the circle so that the missile moves towards the target. The design augmentation proposed for lunar landing introduces a quadratic acceleration term opposite to the instantaneous tangential velocity vector to ensure terminal conditions. Coefficients of the quadratic acceleration profile are determined by the length of the circle as well as the magnitude of instantaneous tangential velocity. Finally a simple compensation scheme based on comparison of actual velocity from sensors and expected velocity from the algorithm is also proposed to take care of the variation in gravity and error in initial mass estimate.

A New Method for Initial Parameters Optimization of Guided Projectiles

Abstract: A new algorithm was developed for the initial parameters optimization of guided projectiles with multiple constraints. Due to the relationship between the analytic guidance logic and state variables of guided projectiles, the Radau pseudospectral method was used to discretize the differential equations including control variables and state variables with multiple constraints into series algebraic equations that were expressed only by state variables. The initial parameter optimization problem was transformed to a nonlinear programming problem, and the sequential quadratic programming algorithm was used to obtain the optimal combinations of initial height and range to target for the final velocity of guided projectiles maximum with constraints. Comparing with the appropriate initial conditions solved by Monte Carlo method and the flight characteristics solved by integrating the original differential equations in the optimal initial parameters computed by the new algorithm, the feasibility of new algorithm was validated.

Study on practical application of a guidance law for overhead-attack

Abstract: This paper investigates a new concept of “overhead-attack”. Firstly, a guidance law with the terminal angle restraint proposed, which is given by establishing the right Hamiltonian. Furthermore the practical application in Engineering is also given in this paper. The guidance law provides a trajectory scheme with terminal angle restraint, which is efficient for penetration bombs or missiles. Simulations show that the guidance law is effective for overhead-attack, which requires higher overload for the bomb as the increase of the terminal angle. Secondly, this paper investigates four important factors for penetration bombs: the guidance system, the homing head, the range, and the maneuverability. The analyses of those four factors are also given. It has been proven that this guidance law works effectively for a bomb that needs to attack an “overhead” target. It confirms that the method works in practical application.