Methods for Damping Payload Oscillations and Robust Control of an Overhead Crane Trolley Considering the Dynamics of the Electric Drive

Abstract

The control plant is a trolley of a single-girder overhead crane designed to move a suspended payload along the span. Features of the plant: one control with two degrees of freedom, the uncertainty of mass-inertial characteristics, and the action of non-smooth uncontrolled disturbances. We consider the reduced dynamics of the DC motor in the mathematical model, where the power supply voltage of the armature circuit is a control. Here, parametric and external disturbances affecting the mechanical subsystem become unmatched (i.e., they act through different channels with control) and cannot be directly compensated. This paper considers two main problems, each of which uses S-shaped smooth sigmoid functions with saturation. The first problem is to design the trajectory of the trolley considering the design constraints on its velocity and acceleration. Tracking such a trajectory should ensure the smooth transfer of the payload in a given time and the damping of its oscillations. For this purpose, a reference trajectory has been developed in the form of the sum of a sigmoid function and an integral of the swing angle. The proposed solution is not inferior in the efficiency to existing analogs, while its implementation requires less computational costs. The second problem is to develop a robust tracking system. For this purpose, a procedure for block synthesis of discontinuous true control and sigmoid fictitious controls (local feedbacks) has been developed. The latter are smooth analogs of discontinuous control and make it possible to suppress unmatched disturbances with a given accuracy without identifying them. In contrast to standard linear local feedbacks, the boundness of sigmoid fictitious controls does not lead to a large overshoot of state variables, which is critical in the presence of design constraints. In addition, such fictitious controls are implemented in mechanical plants and do not contribute to the wear of the actuator, which inevitably occurs when discontinuous fictitious controls are used. We presented the results of numerical simulation and carried out a comparative analysis of closed-loop systems with various fictitious controls: linear, discontinuous, and sigmoid. The results of the numerical simulation demonstrated the effectiveness of the developed approach.