Ilya Ioslovich

Optimal Steady-State Control for Isolated Traffic Intersections

A simplified isolated controlled vehicular traffic intersection with two movements is considered. A discrete-event max-plus model is proposed to formulate an optimization problem for the green-red switching sequence. In the case when the criterion is a strictly increasing, linear function of the queue lengths, the problem becomes a linear programming problem. Also, in this case, the steady-state control problem can be solved analytically. A sufficient and necessary condition for steady-state control is derived, and the structure of optimal steady-state traffic control is revealed. Our condition is the same as the necessary condition in for both queue lengths to be non-increasing at an isolated intersection.

Dominant parameter selection in the marginally identifiable case

Often a rather limited set of experimental data is available for the identification of a dynamic model, which contains many parameters. This is, e.g. the usual case for crop growth models. In this situation, only some parameter values can be estimated. Based on an analysis of the Fisher information matrix, a method for a reasonable selection of parameters is suggested here. The method chooses the most sensitive parameters, i.e. those to which the model under the considered experimental conditions is most sensitive, and excludes both coupled parameters and those that exhibit multiplecorrelation. A comparison with different ridge regression methods is made. The methodology is illustrated with a simple lettuce growth model.

Brief paper: Hamilton-Jacobi-Bellman formalism for optimal climate control of greenhouse crop

The paper describes a simplified dynamic model of a greenhouse tomato crop, and the optimal control problem related to the seasonal benefit of the grower. A HJB formalism is used and the explicit form of the Krotov-Bellman function is obtained for different growth stages. Simulation results are shown.

Optimal Control of Solar Sludge Dryers

Optimal control (OC) methodology is used to develop a control policy for a batch-operated solar sludge dryer with ventilation as the dominant control. Batch performance criteria and instantaneous optimization criteria are developed for two economic environments: quota limited and capital limited. The general formulation, as well as simplifications resulting from the multiplicative form of the evaporation (drying) rate model, are presented. The multiplicative form results in a single constant number, called here “control intensity,” which is used to guide the on-line control decisions. These decisions turn out to be independent of the dry solids content (DSC) of the sludge. Further simplification, by assuming a strictly constant weather, is used to demonstrate the general effects of the economic and physical (weather) environment on the solution. The OC approach is used to address, via simulation under realistic weather conditions, several design, operation, and pricing problems. In particular, the following have been considered: sizing of the ventilation fans, determination of a fair fee for sludge disposal, finding the best final DSC, and evaluating the effect of the price of electricity. Regarding the particular location represented by the data, it has been shown that the installed capacity of the ventilation fans should be increased and that there seems to be sufficient economic incentive for solar drying.

A non-linear optimal greenhouse control problem with heating and ventilation

A simplified non-linear dynamic model of greenhouse crop growth with constraints on the state and the control signal is considered. The weather is assumed to be known. The optimization criterion is to minimize the heating and ventilation cost. In this paper a novel solution is presented for the case when both the heating cost and the ventilation cost are included in the criterion. Important properties of the optimal solutions are clarified. It is found that neighbouring maxima and minima of a particular function of the outside temperature, the solar radiation and the heat transfer coefficient decide whether heating or ventilation has to be applied. A numerical example is given.

Optimal Steady-State Traffic Control for Isolated Intersections

Abstract In this paper a simplified isolated controlled intersection is introduced. A discrete-event max-plus model is proposed to formulate the optimization problem for the switching sequences. The formulated max-plus problem is converted to be solved by linear programming (LP). In the special case when the criterion is a strictly increasing and linear function of the queue lengths, the steady-state control problem can be solved analytically. In addition, necessary condition for the steady-state control is derived.

A model for the global optimization of water prices and usage for the case of spatially distributed sources and consumers

Different problems addressed to the efficiency of the water use and allocation are of great importance in numerous regions including Middle East. Water scarcity is the foremost problem for which solutions are urgently needed. Water prices can be considered as an instrument for satisfactory water allocation and must be justified in a satisfactory way. The significant water losses in distribution also must be taken into consideration. In this paper, an extended model of the water allocation for urban, agricultural and other secondary users is presented. The spatial system of conveyance channels is considered. These channels are of two kind: channels for fresh water and channels for treated water. Each user is assumed to have an efficiency function for all kinds of the consumed water. For this purpose the model of Chakravorty et al. (CHZ model) [J. Environ. Econ. Manage. 29 (1995) 25] is modified. Use of desalinated water and re-use of the treated waste water are also considered. A global optimization method is applied provided with conditions of optimality (transversality conditions). Both water allocation and shadow prices could be found from these conditions.

Brief Optimal control of crop spacing in a plant factory

A crop growth model is used to investigate the optimal control problem associated with plant factory operation. The aim is to find the optimal age-dependent spacing between individual plants such that the profit of the farmer is maximized, in a situation when the production is quota limited. It is shown that the optimal spacing is such that the crop density is kept constant, corresponding to a constant value of the co-state variable in the associated optimal control problem.

Technical Communique: Arbitrary fuel-optimal attitude maneuvering of a non-symmetric space vehicle in a vehicle-fixed coordinate frame

The current rotation of a space vehicle in a vehicle-fixed coordinate frame often needs to be changed. Arbitrary maneuvers of this kind are considered with unconstrained time and minimal fuel consumption. The problem is solved analytically using a global optimization method based on the Krotov-Bellman sufficient conditions.

Optimal Control of Rigid Body Rotation Around Center of Mass

The problem of axisymmetric rigid body angular velocity vector maneuvering in the body-fixed frame is considered. Control actuators are provided by two pairs of reactive jets with constant torque directions, and with possibly unequal jet characteristics. The transfer time from the initial to endpoint in the body-fixed frame of angular velocities is not specified. Both the initial and endpoint are arbitrary and given in advance. The problem is solved in a closed analytical form, using sufficient conditions of optimality.