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two-level-control
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Optimal Control Approach to Formtaion Flight of Quadrotors
, M.Sc. Thesis Sharif University of Technology ; Pourtakdoost, Hossein (Supervisor)
Abstract
The problem of quadrotors formation flying via optimal approach is investigated using the idea of cooperative and multi-level control. In this respect, a low level optimal control formulation of quadrotors is formulated for stability and tracking where the required tracking commands are generated via the high level controller over a simpler translational dynamics of quads. The idea of multi-level controllers enables one to develop formation keeping controls for complex dynamics systems, where varying agents in terms of dynamics and platform could be utilized. Due to inherent difficulties in implementing acceleration commands emanated out of the high level controller, an inverse dynamic...
Hierarchical optimal robust load-frequency control for power systems
, Article IET Generation, Transmission and Distribution ; Volume 6, Issue 4 , 2012 , Pages 303-312 ; 17518687 (ISSN) ; Sadati, N ; Sharif University of Technology
Abstract
In this study, a hierarchical optimal robust controller is presented for the power system load-frequency control problem. In this approach, the multi-area power system is first decomposed into several sub-systems (areas). Then by using a two-level control strategy, the overall optimal solution is obtained. At the first level, the optimal control of each area is obtained with respect to local information and also considering interactions coming from other areas. At the second level, by using a coordination strategy, the local controllers will converge to global solution and optimal robust controller is achieved. This approach is applicable to both single-area and multi-area interconnected...
Hierarchical optimal control of a binary distillation column
, Article Optimal Control Applications and Methods ; 2018 ; 01432087 (ISSN) ; Sadati, N ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
This paper presents a two-level optimal control for the binary distillation column. From the control point of view, the binary distillation column is a high-order system consisting of several interconnected subsystems (trays) that aim to maximize output purity. Controlling the system in a hierarchical manner not only decreases complexity and solution time but also can improve the control structure's reliability. In this study, the distillation column is decomposed into NT second-order subsystems, each representing one stage (one tray). Accordingly, the cost function is decomposed, and thus, the overall problem is converted into NT lower-order subproblems where each tray has its own...
A Novel Approach to Mixed Model and Goal Coordination of Large-Scale Systems
, Ph.D. Dissertation Sharif University of Technology ; Sadati, Naser (Supervisor)
Abstract
In this thesis, a new approach is proposed for two-level optimal control of large-scale nonlinear systems. In this approach, by defining some parameters as coordination parameters the overall system is decomposed into several interactive subsystems, where the optimization problem redefines for each one of them. The obtained sub-problems which are in the form of standard optimal control problems with lower dimension are solved in the first level. To obtain the overall optimal solution, coordination of the first level solutions is performed in the second level. For solving the first level problems, the indirect gradient and Newton methods are used. The gradient method is applied in the first...
Design of Continuous and Time-Invariant Controllers for Exponential Stabilization of Periodic Walking and Running Locomotion in Planar Bipedal Robots
, Ph.D. Dissertation Sharif University of Technology ; Sadati, Nasser (Supervisor)
Abstract
During the last decades there have been enormous advances in robot control of dynamic walking and running. The desire to study legged locomotion has been motivated by 1) the desire to replace humans in hazardous occupations, 2) the desire to assist disabled people to walk and 3) the desire to investigate the complicated motions of the mankind. The control of dynamic walking and running is complicated by (i) limb coordination, (ii) hybrid nature of running due to presence of impact and takeoff, (iii) underactuation and overactuation, (iv) inability to apply the Zero Moment Point (ZMP) criterion, (v) lack of algorithms to achieve feasible period-one orbits, and (vi) conservation of angular...
Stabilization of periodic orbits for planar walking with noninstantaneous double-support phase
, Article IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans ; Volume 42, Issue 3 , 2012 , Pages 685-706 ; 10834427 (ISSN) ; Sadati, N ; Gruver, W. A ; Dumont, G. A ; Sharif University of Technology
Abstract
This paper presents an analytical approach to design a continuous time-invariant two-level control scheme for asymptotic stabilization of a desired period-one trajectory for a hybrid model describing walking by a planar biped robot with noninstantaneous double-support phase and point feet. It is assumed that the hybrid model consists of both single- and double-support phases. The design method is based on the concept of hybrid zero dynamics. At the first level, parameterized continuous within-stride controllers, including single- and double-support-phase controllers, are employed. These controllers create a family of 2-D finite-time attractive and invariant submanifolds on which the dynamics...
Two-level control scheme for stabilisation of periodic orbits for planar monopedal running
, Article IET Control Theory and Applications ; Volume 5, Issue 13 , Sept , 2011 , Pages 1528-1543 ; 17518644 (ISSN) ; Dumont, G. A ; Hamed, K. A ; Gruver, W. A ; Sharif University of Technology
2011
Abstract
This study presents an online motion planning algorithm for generating reference trajectories during flight phases of a planar monopedal robot to transfer the configuration of the mechanical system from a specified initial pose to a specified final one. The algorithm developed in this research is based on the reachability and optimal control formulations of a time-varying linear system with input and state constraints. A two-level control scheme is developed for asymptotic stabilisation of a desired period-one orbit during running of the robot. Within-stride controllers, including stance and flight phase controllers, are employed at the first level. The flight phase controller is a feedback...