Improving Circular Path Control Using Extended State Observers for an Industrial Overhead Crane

Abstract

In industrial overhead cranes, inverters and motors are used to control motor position, velocity, and acceleration. However, higher-order derivatives depend on load characteristics, leading to inconsistent jerk profiles and deviations in circular path. Payload sway further contributes to path deviation, and although sway suppression techniques are beneficial, they extend the transient response time. This paper proposes a position feedback control technique based on extended state observers to compensate for the higher-order dynamics, and address uncertainties in the driven unit through disturbance rejection. A command smoother is analyzed to provide an equation used for path deviation prediction. The trapezoidal trajectory, expressed as a function of sine and cosine, is analyzed to use in this circular path study. A command smoother with feedforward control, is used to mitigate payload sway, demonstrating advantages over existing techniques by enabling smoother and faster motion. Several experiments were conducted on an industrial-grade overhead crane to evaluate the effects of different high-order dynamics and the effect from utilizing the sway suppression technique. The extended state observers parametrically compensate for the high-order dynamics of the trolley, resulting in better path deviation. With the proposed controller, the percent overshoot was measured as 2.1%, compared to 16.8% without the controller. The equation used to predict path deviation in circular paths is proposed. In conclusion, the use of extended state observers significantly improves circular path deviation in overhead crane applications. The proposed equation highlights the tradeoff between path deviation and rapid motion in curved paths.