Control allocation for linear systems with four or more objectives
11 Aug 2003-
TL;DR: Methods for allocating redundant controls for systems with four or more objectives are studied and the recursive allocator is found to scale linearly with the number of controls.
Abstract: Methods for allocating redundant controls for systems with four or more objectives are studied. The Bisecting Edge Search Algorithm has been presented as a computationally e‐cient method for allocating controls in the three objective problem. A recursive method for extending this algorithm to handle any number of objectives was developed. The recursive algorithm is designed to be similar to the three objective allocator and to require computational efiort which scales linearly with the controls. Numerical results illustrate how the average and worst case performance scales with the problem size. The recursive allocator is found to scale linearly with the number of controls. As the number of objectives increases, the computational time grows much faster. The estimation of solutions if the allocator is forced to exit early is discussed.
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13 Aug 2012
5 citations
TL;DR: This work demonstrates the empirical validity and utility of the switching system through implementation in a developed robotic arm equipped with biarticular actuation redundancy, and finds that resolution allows for equivalent maximum torque requirements as the infinity- norm – an improvement over two-norm – but with improved electrical energy requirements over infinity-norm.
Abstract: Utilization of redundancy endows systems with dexterity and fault tolerance in achieving its desired output, but its utilization implies added complication which must be resolved. Input optimization using the two-norm and the infinity-norm are two methods popularly utilized to address this problem. However, each resolution criteria finds its greatest benefit in opposite circumstances. This fact has long motivated a resolution system which makes use of both norms, switching back and forth when called for. In a previous publication, we introduced and proved the continuity of the first realization of such a switching resolution system, implemented in the resolution of biarticular actuation redundancy. In this work, we demonstrate the empirical validity and utility of the switching system through implementation in a developed robotic arm equipped with biarticular actuation redundancy. It is found that resolution allows for equivalent maximum torque requirements as the infinity-norm – an improvement over two-n...
5 citations
08 Aug 2011
TL;DR: In this paper, the authors present a straightforward technique for assessing and realizing the maximum control moment effectiveness for a launch vehicle with multiple constrained rocket nozzles, where elliptical deflection limits in gimbal axes are expressed as an ensemble of independent quadratic constraints.
Abstract: In this paper we present a straightforward technique for assessing and realizing the maximum control moment effectiveness for a launch vehicle with multiple constrained rocket nozzles, where elliptical deflection limits in gimbal axes are expressed as an ensemble of independent quadratic constraints. A direct method of determining an approximating ellipsoid that inscribes the set of attainable angular accelerations is derived. In the case of a parameterized linear generalized inverse, the geometry of the attainable set is computationally expensive to obtain but can be approximated to a high degree of accuracy with the proposed method. A linear inverse can then be optimized to maximize the volume of the true attainable set by maximizing the volume of the approximating ellipsoid. The use of a linear inverse does not preclude the use of linear methods for stability analysis and control design, preferred in practice for assessing the stability characteristics of the inertial and servoelastic coupling appearing in large boosters. The present techniques are demonstrated via application to the control allocation scheme for a concept heavy-lift launch vehicle.
2 citations
TL;DR: The main feature of the proposed configuration among feasible configuration with minimum number of required thrusters, which has held to optimal configuration, is that this configuration has maximum reliability and minimum fuel consumption.
Abstract: An optimal thruster configuration for attitude control subsystem of a spacecraft is presented in this paper. The optimal configuration is designed according to minimum number of required thrusters for satisfying desired reliability with specific redundancy level. The genetic algorithm is employed for optimization process and feasibility of the results is evaluated using algebraic and geometry methods. The main feature of the proposed configuration among feasible configuration with minimum number of required thrusters, which has held to optimal configuration, is that this configuration has maximum reliability and minimum fuel consumption. In addition to feasibility, attitude control performance of some configurations is also examined through the simulation. The results of simulation confirm that the proposed configuration has desirable performance. It is noteworthy to mention that the configuration with maximum number of required thrusters, which is a conventional configuration such that each thruster belongs to only one control channel, has less fuel consumption than optimal configuration. However, the total mass of optimal configuration is less than that of conventional configuration due to a smaller number of thrusters.
2 citations
04 Nov 2016
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TL;DR: In this article, the problem of the allocation of several airplane flight controls to the generation of specified body-axis moments is addressed, and a direct method of allocating these several controls is presented that guarantees the maximum possible moment can be generated within the constraints of the controls.
Abstract: This paper addresses the problem of the allocation of several airplane flight controls to the generation of specified body-axis moments. The number of controls is greater than the number of moments being controlled, and the ranges of the controls are constrained to certain limits. They are assumed to be individually linear in their effect throughout their ranges of motion and independent of one another in their effects. The geometries of the subset of the constrained controls and of its image in moment space are examined. A direct method of allocating these several controls is presented that guarantees the maximum possible moment can be generated within the constraints of the controls. It is shown that no single generalized inverse can yield these maximum moments everywhere without violating some control constraint. A method is presented for the determination of a generalized inverse that satisfies given specifications which are arbitrary but restricted in number. We then pose and solve a minimization problem that yields the generalized inverse that best approximates the exact solutions. The results are illustrated at each step by an example problem involving three controls and two moments.
527 citations
Dissertation•
19 Dec 1996
TL;DR: The Null-Space Intersection method was derived from the same principles used to compute for a generalized inverse, the principles involved in finding the intersection of a subspace with a higher dimensional polytope.
Abstract: The Null-Space Intersection method was derived from the same principles used to compute for a generalized inverse. Specifically, the principles involved in finding the intersection of a subspace with a higher dimensional polytope are used. When calculating , the subspace represents directions in which the controls should be deflected to generate specified moments. The Null-Space Intersection method involves the use of a subspace which represents directions in which the controls can be deflected without changing the moment generated.
137 citations
108 citations