# Modifications to ArduSub That Improve BlueROV SITL Accuracy and Design of Hybrid Autopilot
###### Abstract  
Improvements to ArduSub for the BlueROV2 (BROV2) Heavy, necessary for accurate simulation and autonomous controller design, were implemented and validated in this work. The simulation model was made more accurate with new data obtained from real-world testing and values from the literature. The manual control algorithm in the BROV2 firmware was replaced with one compatible with automatic control. In a Robot Operating System (ROS), a proportional-derivative (PD) controller to assist augmented reality (AR) pilots in controlling angular degrees of freedom (DOF) of the vehicle was implemented. Open-loop testing determined the yaw hydrodynamic model of the vehicle. A general mathematical method to determine PD gains as a function of the desired closed-loop performance was outlined. Testing was carried out in the updated simulation environment. Step response testing found that a modified derivative gain was necessary. Comparable real-world results were obtained using settings determined in the simulation environment. Frequency response testing of the modified yaw control law discovered that the bandwidth of the nonlinear system had a one-to-one correspondence with the desired closed-loop natural frequency of a simplified linear approximation. The control law was generalized for angular DOF and linear DOF were operated with open-loop control. A full six-DOF simulated dive demonstrated excellent tracking. ROV; UUV; control; ArduSub; ocean robotics; ROS; AR/VR +
Footnote †: journal: Applied  
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modified consumer-priced ROVs like the Trident OpenROV for conservation planning [11]. OpenROV started out as a crowd-funded project that grew into an open-source platform for affordable ROV hardware and software. They have since been merged into Sofar Ocean Technologies [12] and discontinued their support for Trident, now focusing on passive ocean sensing. Blue Robotics has a similar crowdfunding backstory, but has continued operations to the present day. It has established itself as a prominent source of affordable high-quality marine robotics equipment like thrusters, tethers, and pressure vessels. Their flagship product is the BlueROV2 (BROV2, Blue Robotics, CA, USA) [13], which comes in standard six-thruster or eight-thruster Heavy configurations (Figure 2), which have been popular choices among researchers. The BROV2 has been used in aquaculture to track the length of kelp with machine learning image processing [14] and been modified for under-ice sensing [15]. In light of the popularity of the BROV2, other works have focused on control topics, modeling the BROV2 and incorporating automation techniques. A comprehensive simulation study of the Heavy configuration was conducted in [16] but no real-world validation was performed. The study conducted by [17] looked at the six-thruster configuration and also conducted real-world validation; however, they swapped out the original controller components and implemented an entirely new software library. In this paper, both simulation and real-world testing shall be performed using stock components of a BROV2 Heavy and a modified version of the original software library so that the results may be more immediately applicable to other users. Although ROVs are not suitable for long-distance travel due to their large drag and tether, they are equipped with numerous thrusters granting enhanced mobility over their hydrodynamic torpedo-like (AUV) counterparts. Piloting ROVs can be a daunting control task because of the challenges in underwater station keeping and managing several degrees of freedom, sometimes including one or more manipulator arms simultaneously, often requiring multiple pilots [18].