1987 American Control Conference

This paper considers the problem of passing from a linear time-invariant high order controller designed for a linear time-invariant plant (of presumably high order) to a low order approximation of the controller. The approximation problem is often best posed as a frequency weighted L∞approximation problem. Many different controller representations are possible, giving different performa... View full abstract»

A sub-optimal nonlinear controller which is synthesized by using the external linearization approach is applied to the optimal control of stochastic parametrically and externally excited nonlinear systems with complete state information. Algebraic necessary conditions are derived for the minimization of the quadratic cost function through the concepts of equivalent external excitation. The concept... View full abstract»

In this paper, a method is given for stabilizing compensation design for a large class of discrete time nonlinear stochastic systems with incomplete state information. The nonlinearity is contained either in the state or the output equation and it involves a zero mean white noise sequence. The proposed compensator is a constant gain observer together with a constant feedback control gain. The stab... View full abstract»

A multi-model formulation is obtained for the Hierarchical Dynamic Resource Allocation Problems. which is a class of two-level, multi-decision maker control problems with non-deterministic dynamics and feasibility objective. Each decision maker in the lower hierarchical level (known as a Local Manager) is assumed to possess a different incomplete model of the underlying dynamical system. The fesib... View full abstract»

This paper studies a class of renewable resource allocation problems for the processing of dynamically arriving tasks with deterministic deadlines. This class of problems has many applications, however, it conforms to neither the standard resource allocation model nor the standard optimal control model. A new problem formulation has to be developed and analyzed to provide a satisfactory solution. ... View full abstract»

Under large mathematical conditions, the kowledge of the state probability density of a nonlinear stochastic distributed system is completely equivalent to the knowledge of all its state moments; and as a consequence, it may be interesting to investigate analysis techniques based on the study of these moments only. A method is herein proposed, which avoids the use of stochastic partial differentia... View full abstract»

The non-classical nature of multi-person stochastic control problems of team problems was first pointed out by Witsenhausen [1] via a simple example, which has since been known as Witsenhausen's counterexample. The example is a simple two-person two-step team problem: The first person 1 observes exactly the system's initial state x0, and based on it, chooses his action x1. Th... View full abstract»

In this paper we propose a controller for the path tracking problem of robotic manipulators. The proposed controller structure is very similar to that of the "computed-torque" scheme widely known in the literature. However, unlike the "computed-torque" scheme this controller is robust with respect to parameter uncertainty and disturbances. The robustness is provided by a high gain mechanism that w... View full abstract»

This paper proposes a hybrid, multivariable, adaptive model-matching scheme for controlling robotic manipulators and demonstrates its advantages over similar discrete schemes. In the hybrid approach, the controller itself is a continuously adjustable one, but the adaptation mechanism uses discrete algorithms. Thus it offers the advantages of less parameterization and complete freedom in the choice... View full abstract»

The hydraulic coupling in the series-bypass circuit is examined in this paper. Application of multivariable techniques to the series-bypass circuit is also presented. The series-bypass circuit combines variable displacement pumps and serially connected, bypass flow modulated actuators. A prototype series-bypass circuit is mathematically modeled and analyzed using linear dynamic models and a nonlin... View full abstract»

The controller synthesis procedure proposed in Jayasuriya, et. al (1984), for precise tracking of reference inputs in the sense of spheres is applied to a 3 d.o.f. robotic manipulator. Their methodology applies to a class of nonlinear systems with input uncertainty and parameter uncertainty. The 3 d.o.f. manipulator to be controlled is subjected to varying payloads and is required to follow specif... View full abstract»

Two recursive dynamic models, based on the Newton-Euler formulation, are proposed to model the dynamics of manipulators with link flexibility. In both models, the displacement and rotation due to the link flexibility are assumed to be measurable. For a small link deformation, a first-order lumped mass/spring approximation model is proposed, in which the parameters of each link are lumped to its jo... View full abstract»

In this article the slow manifold of a system with actuator parasitics is used as a sliding surface on which a Variable Structure Controller recovers the qualitative properties of the reduced order, closed loop system obtained from an ideal actuator-based feedback controller design. Illustrative examples are presented, where 1) the simplicity of reduced order singular perturbation design methods; ... View full abstract»

In this paper we study sliding mode controllers, in particular those intended for tracking. It is well known that a sliding motion occurs if s_i s_i < 0 in the neighborhood of the sliding surface s_i = 0. Our studies appear to show that the guarantee of "stability" on the sliding manifold is quite delicate. Only simulation eviden... View full abstract»

This paper examines the problem of the control of multivariable linear time-invariant dynamical systems with bounded controllers using the Variable Structure Control (VSC) approach. New type of Lyapunov functions is introduced. The domain of attraction for this class of systems is obtained. A coordinate transformation for decoupling the "fast" and "slow" states is also presented. This transformati... View full abstract»

Model reference variable structure controllers are applied to switched-mode circuits, and their performance robustness is investigated. A generalized formulation together with its solution is presented for a class of problems, in variable structure control, involving state-space analysis of inherently time-varying regulators. The effects of the design averaging model and its description on trackin... View full abstract»

One step ahead optimization has been recently proposed for spacecraft attitude maneuvers as well as for robot manipulator maneuvers. Such a technique yields a discrete time control algorithm implementable as a sequence of state-dependent, quadratic programming problems for acceleration optimization. Its sensitivity to model accuracy, for the required inversion of the system dynamics, is shown in t... View full abstract»