Showing 3 results for Optimal Control
A. Ebrahimi, S. A.a. Mousavian, and M. Mirshams,
Volume 24, Issue 2 (1-2006)
Abstract
The rapid growth of space utilization requires extensive construction, and maintenance of space structures and satellites in orbit.
This will, in turn, substantiate application of robotic systems in space. In this paper, a near-minimum-time optimal control law is developed for a rigid space platform with flexible links during an orientating maneuver with large angle of rotation. The time optimal control solution for the rigid-body mode is obtained as a bang-bang function and applied to the flexible system after smoothening the control inputs to avoid stimulation of the flexible modes. This will also reflect practical limitations in exerting bang-bang actuator forces/torques, due to delays and non-zero time constants of existing actuation elements. The smoothness of the input command is obtained by reshaping its profile based on consideration of additional first-order and second-order derivative constraints. The platform is modeled as a linear undamped elastic system that yields an appropriate model for the analysis of planar rotational maneuvers. The developed control law is applied on a given satellite during a slewing maneuver. The simulation results show that the modified realistic optimal input compared to the bang-bang solution agrees well with the practical limitations and also alleviates the vibrating motion of the flexible appendage, which reveals the merits of the new control law developed here.
A. Hosseini, M. Keshmiri, and M. J. Sadigh,
Volume 26, Issue 1 (7-2007)
Abstract
The optimal path planning of cooperative manipulators is studied in the present research. Optimal Control Theory is employed to calculate the optimal path of each joint choosing an appropriate index of the system to be minimized and taking the kinematics equations as the constraints. The formulation has been derived using Pontryagin Minimum Principle and results in a Two Point Boundary Value Problem, (TPBVP). The problem is solved for a cooperative manipulator system consisting of two 3-DOF serial robots.
Z. Z. Ahangari Sisi, M. Mirzaei, S. Rafatnia, B. Alizadeh,
Volume 39, Issue 2 (2-2021)
Abstract
Active vehicle suspension system is designed to increase the ride comfort and road holding of vehicles. Due to limitations in the external force produced by actuator, the design problem encounters the constraint on the control input. In this paper, a novel nonlinear controller with the input constraint is designed for the active suspension system. In the proposed method, at first, a constrained multi-objective optimization problem is defined. In this problem, a performance index is defined as a weighted combination of the predicted responses of the nonlinear suspension system and control input. Then, this problem is solved by the modified firefly optimization algorithm to find the constrained optimal control input. To evaluate the performance of the proposed method, the results of the unconstrained and constrained controllers are provided and discussed for various road excitations. The results show a remarkable increase in the ride comfort with the limited force, while other suspension outputs including the suspension travel and tire deflection being in the acceptable ranges. In addition, these controllers are compared with Sliding Mode Control (SMC) and Nonlinear Model Predictive Control (NMPC) in the presence of model uncertainty.
