Effect of ship steering system parameters to quality of autopilot control
The paper is devoted to study the influence of steering system parameters on the quality of vessel motion under autopilot control. A simplified structure of the mathematical model of the steering machine is considered, which allows taking into account the main nonlinear effects. An electrohydraulic drive is modeled as the most common one; other types of steering drives can be described by similar models. The key element of the electrohydraulic drive is a three-way hydraulic distributor (hereinafter referred to as the valve) that switches the direction of fluid flows. Regardless of the physical implementation of the redirection of working fluid flows (three-way valve, direct control of a variable-capacity pump, or a reversible pump), the mathematical description of the drive motion processes can be reduced to modeling a three-way valve and integrating the rudder shift speed. Two cases are considered: discrete and proportional valve control. Particular attention is paid to the case of discrete control, taking into account the dynamics of opening and closing of the valves. The results of modeling the dynamics of rudder shifting and its influence on the dynamics of vessel motion under autopilot control are presented. The paper presents the results of modeling the vessel's motion during the zigzag maneuver (the maneuver is used to identify the vessel's parameters and synthesize the autopilot controllers) with different parameters of the steering gear, and notes that in some cases this can significantly affect the results of identifying the linearized model for this maneuver. The paper presents the results of modeling the motion under the autopilot with constant disturbance, and shows how, due to the drive parameters, undesirable oscillatory modes arise, leading to deterioration in the quality of heading control, and, as a consequence, to an increase in fuel consumption and rapid wearout of the steering gear.
Authors: E. B. Ambrosovskaya, M. A. Cherniy, D. V. Romaev, V. I. Nikolskiy
Direction: Informatics, Computer Technologies And Control
Keywords: vessel motion control, autopilots, steering systems, motion simulation, identification
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