Showing papers on "Variable structure control published in 1979"

Optimal feedback control via block-pulse functions

Abstract: Using block-pulse functions, a method is presented to determine the piecewise constant feedback controls for a finite linear Optimal control problem of a power system. The method is simple and computationally advantageous.

A singular perturbation analysis of optimal aerodynamic and thrust magnitude control

Abstract: This paper illustrates the application of singular perturbation methods to optimal thrust magnitude control (TMC) and optimal lift control in flight mechanics. The modeling is restricted to horizontal plane dynamics. A multiple time scale analysis results in nonlinear feedback control solutions for lift and thrust during a turn to a specified down range position. The analysis is carried out to rust order with respect to the position state variables. Numerical results for a medium range and a short range air-launched missile are given, and comparisons are made to two alternative propulsion control concepts. The multiple time scaling procedure used here is applicable to solving a wide class of optimal control problems. It avoids the problem in asymptotic methods of picking the unknown adjoints to suppress unstable modes in the boundary layer and reduces the two-point boundary value problem to a series of pointwise function extremizations. Hence, the optimal control solution is essentially analytic and algebraic.

Position control system of the discontinuous feedback type

Abstract: A position control system is disclosed for aiming a mobile rocket launcher having positionable axes in the azimuth and elevation planes. The control system has a separate control subsystem for each axis of movement, and each such subsystem includes an initial aiming signal processor providing a course positioning function and a reaiming signal processor providing a fine positioning function. The initial aiming processor receives signals representing a desired position (DP), a feedback signal representing the actual position (AP) updated at predetermined sampling intervals, and an error signal (E) representing the difference between DP and AP. From signals representing AP and E, and a constant representing the stopping time of the launcher mechanism for a given control axis, the initial aiming processor produces a predicted position signal (PP) which represents the position that the launcher will reach upon termination of the actuator drive for that axis. The signal PP is then compared with the signal representing DP and depending upon a predetermined relationship between the predicted and desired positions of the launcher an actuator control signal is generated for driving the associated actuator at either a full forward or full reverse speed, or stopping and braking the associated launcher mechanism. The reaiming processor incorporates an error averaging network and an actuator signal function generator. The former averages, over a given time interval, the magnitude and directon of the error signal E, and the latter is responsive to the time average error (AE) to generate a forward or reverse actuator drive signal for an incrementally variable duration T c , that increase or decrease with the magnitude of AE and is timed to remove any remaining error in the position of the launcher for the given control axis. The reaiming processor is reactivated after each rocket launching to reaim the launcher to correct for any disturbance to its original position caused by the firing recoil, and the correlation provided by the function generator between the average error AE and the signal duration T c is updated from time to time to compensate for varying actuator drive characteristics due to wear and environmental conditions.

Load frequency control using Lyapunov's second method: Bang-bang control of speed changer position

Abstract: This letter reports a bang-bang load frequency control policy based on the second method of Lyapunov. The proposed method is simple and practically feasible for implementation. A numerical illustration on a two-area load frequency control system is presented in order to verify the practicality of the proposed method.

Suboptimal regulator design of linear systems with quantized controls

Abstract: This short paper presents a design technique for determining a suboptimal feedback control law for linear systems actuated by the quantized control signals. This control law is easily implemented in the form of the switching hyperplanes characterized by a nonlinear matrix difference equation for discrete-time systems or by a differential equation for continuous-time systems. The properties of this control law are investigated in detail.

Comparative study of flare control laws

Abstract: A digital 3-D automatic control law was developed to achieve an optimal transition of a B-737 aircraft between various initial glid slope conditions and the desired final touchdown condition. A discrete, time-invariant, optimal, closed-loop control law presented for a linear regulator problem, was extended to include a system being acted upon by a constant disturbance. Two forms of control laws were derived to solve this problem. One method utilized the feedback of integral states defined appropriately and augmented with the original system equations. The second method formulated the problem as a control variable constraint, and the control variables were augmented with the original system. The control variable constraint control law yielded a better performance compared to feedback control law for the integral states chosen.