Luis A. Mateos

In robotics, there are two main methodologies for assembly structures with autonomous robots regardless of the environment (terrestrial / aerial / aquatic). The first is robots transporting the building block for constructing the structure [1] [2]. And the second method is robots attaching themselves to the structure as a building unit [3] [4].

In this study we follow the second methodology, in which the robot is a building unit. But first we introduce developments in Autonomous Undewater Vehicles (AUV) docking stations and present how we embed these concepts in our autonomous latching system for robotic boats.

AUVs have extensive development of docking systems that protect and recharge the underwater robot [5] [6] [7] [8] [9] [10]. However for robotic boats or Autonomous Surface Vehicles (ASV), there are relatively limited research accomplishments in latching systems for docking to a station [11] [12] or to another boat or to multiple boats [13]. The main challenges are due to water and wind dynamics which cause disturbances such as movements, vibration and inclination on the boats.

atching systems for AUV

The process to latch an AUV into a docking station is the following:

The first step is homing. This step utilizes a tracking system to assist in guiding the AUV into the dock. This system is activated once the AUV is within a close range of distance to the docking station. In order to measure the distance between the AUV and a docking station, the following sensors can be applied:

1) Acoustic. This solution consists of an ultra short base line (USBL) with a range up to 30m with the accuracy of ±0.2m. [5] [6] [9] [14].

2) Electromagnets. The electromagnetic solution is able to provide the orentation and is able function within a range up to 10m with the accuracy of ±0.1m [7].

3) Optics. The optical approach can be thermal [15] or visual [10] [16] with a range up to the visibility of the target (1m to 15m) and high accuracy in the milimeter range.

Robotic boats homing (guiding).

The second step of latching is docking, which specifically refers to joining the AUV to a static docking station [17] [15] [16] [14]. Several docking components in AUVs have been widely considered by academy and industry. Among these are:

1) Framed modular garage. The tubular garage is commonly shaped as a cone or funnel, which helps minimizing the level of precision required to dock the AUV by increasing the target size. In this way, the vehicle approaches the funnel entrance, while misalignments are mechanically corrected [15] [16] [14].

2) Stinger. This system is similar to the aircraft base stations, where the airplanes land with the help of a wired hook that latches on a predetermined slot [5].

Robotic boats docking (joining).

Once docking is done, the next step is garaging in which the vehicle is locked, securing its position. In this context, the locking mechanism can be as simple as a hook, or a more elaborated system that involve active devices, such as motorized-screws [18].

Robotic boats garaging (locking). A roboat can tow a another roboat or a floating "dummy" boat.

2019 Luis A. Mateos