Simplified Analysis of IMU Sensor Corruptions on Existing Pendulation Control System For Ship-Mounted Crane

Abstract

Ship-mounted boom cranes play an important role in the ship-to-ship offshore cargo transport process. In recent years, there has been significant need to increase stability of the payload during the cargo transport process for both safety and efficiency reasons. However, the stability of the payload during the transport process directly correlates to the ship's pitch and roll motion that in turn relates to the current particular sea-state.

In this study, we analyze an existing Pendulation Control System (PCS) developed by Sandia National Laboratories that reduces the payload's pendulation movement during transport. This system measures the ship motion through a complex inertial navigation system using an IMU and dual GPS receivers. In trying to simplify the analysis of the IMU sensor, we simulate new control solutions based solely on an IMU-only ship motion measurement system using both position- and velocity-based controllers. This study shows that an optional bandpass filter in the new control solution can reject a bias that appears in the estimated accelerometer data at the expense of higher sensitivity for the control. This study also shows that the velocity-based solution provides comparable if not better results than the position-based solution. Both methods are sensitive to the difference between the ship motion period and the center frequency of its bandpass filter. Lastly, it is shown that the bias of an accelerometer is not a large source of payload disturbance as compared to the scale factor error.