How to Accurately Guide a Subsea Lifting Pin into a Conical Bell Mouth[Dayu Electronics]

　　Project Background

　　During offshore construction, a cone-shaped body needs to be lowered into a bell mouth via a lifting operation. Due to the refractive index of seawater and the turbidity of the water, video guidance cannot be used to direct the cone into the bell mouth. Since operations are carried out in shallow waters, severe multipath reflections cause significant errors in ultra-short baseline (USBL) positioning. Therefore, a solution is needed to guide the lifting equipment to accurately place the cone into the bell mouth to complete the connection.

　　System Overview

　　Based on the operating environment, with a maximum water depth of 50 meters, the required horizontal positioning accuracy is ±5–10 cm.

　　Notes:

　　1. The effects of high wind and wave conditions are not considered here.

　　2. Active positioning technology is used for underwater localization.

　　3. The positioning range covers the bell mouth where the locking pin is fixed, with a radius of 50 meters.

　　System Components

　　1. Pin-end communication module

　　2. Bell-mouth-end communication module

　　3. Bell-mouth-end positioning transducer

　　4. Positioning transmitter

　　5. Mounting bracket for the pin-end communication module

　　6. Mounting bracket for the bell-mouth-end communication module and the positioning transducer

　　7. Cable