Development of a coordinated controller for underwater vehicle-manipulator systems

The <xref ref-type="bibr" rid="bib2">2009 Marine Advanced Technology Education (MATE)</xref> remotely operated vehicle (ROV) competition focuses on a submarine rescue training exercise. There are four tasks outlined for the Ranger class, each providing its own challenge. Our ROV was designed to carry out these tasks with precision and agility.The team spent numerous hours planning, building, and field testing our ROV. We had to be prepared to combat technical problems and overcome the challenge of differing opinions. Because of the diversity of the tasks, Suijin had to be very well designed. This required the creation of a rigid frame, useful end effectors, and a versatile propulsion system; a form of buoyancy, effective sensors, and proper wiring were also necessary. There were many ideas to consider and obstacles to overcome, but finally, we completed our masterpiece.Heritage Robotics is very pleased to present the following technical report, which communicates the details of Suijin, an ROV created by students from Heritage Collegiate, Lethbridge, Newfoundland, Canada. This document includes detailed descriptions and diagrams of Suijin’s components, possible future improvements, trouble shooting techniques, the lessons we learned, the challenges we faced, information on the Submersible LR5, reflections, a thorough budget, and acknowledgments of all those who helped along the way.

Hydrodynamic forces are an important input value for the design, navigation and station keeping of underwater Remotely Operated Vehicles (ROVs). The experiment investigated the forces imparted by currents (with representative real world turbulence) and waves on a commercially available ROV, namely the BlueROV2 (Blue Robotics, Torrance, USA). Three different distances of a simplified cylindrical obstacle (shading effects) were investigated in addition to the free stream cases. Eight tethers held the ROV in the middle of the 2 m water depth to minimise the influence of the support structure without completely restricting the degrees of freedom (DoF). Each tether was equipped with a load cell and small motions and rotations were documented with an underwater video motion capture system. The paper describes the experimental set-up, input values (current speed and wave definitions) and initial processing of the data. In addition to the raw data, a processed dataset is provided, which includes forces in all three main coordinate directions for each mounting point synchronised with the 6DoF results and the free surface elevations. The provided dataset can be used as a validation experiment as well as for testing and development of an algorithm for position control of comparable ROVs.

The use of underwater vehicle manipulator systems (UVMS) equipped with cameras has gained significant attention due to their capacity to perform underwater tasks autonomously. However, controlling both the manipulator and the remotely operated vehicle (ROV) based on the vision system information is not an easy task, especially in situations where the vehicle cannot be parked/held stationary. Most of the existing approaches work based on complex matrix calculations for the inverse kinematics (IK), which can lead to high computational costs and the need to deal with singularity problems. A problem arises when the amount of time needed to calculate the UVMS configuration can result in reduced frequency of target pose estimation, beyond the point where the target has moved out of the camera field of view. Therefore, this paper proposes an autonomous visual servoing approach for UVMS, including an extension of a heuristic technique named M-FABRIK (Mobile - Forward and Backward Reaching IK) to calculate the UVMS inverse kinematics in a simple and fast way. This approach aims to control both the configuration of the manipulator and ROV position in order to allow underwater intervention in situations where the ROV cannot be parked/held stationary. This solution allows the vehicle to be positioned according to additional criteria, besides avoiding matrix inversion and being robust to singularities. Trials have been performed with a manipulator mounted on a work-class ROV for an autonomous underwater monitoring task and results demonstrate a simple and fast approach, which is able to set the configuration of the manipulator as well as the ROV for visual servoing applications in real-time, such as for monitoring, tracking and intervention tasks underwater.

Offshore petroleum reserves have been discovered in depths approaching 3050 m (10000 ft) in the Gulf of Mexico. Therefore, there is a need for the design of a remotely operated vehicle (ROV) and a launch and recovery system for the vehicle that is capable of working in this water depth. The ROV is an observational vehicle used to observe underwater systems and operations. The design criteria is 3050 m (10000 ft) depth, Gulf of Mexico, free swimming, tethered, able to cut 0.64 cm (0.25 in) steel cable, capable of lifting 22.7 kg (50 lb), and a 1.04 m/s (2 kt) forward speed, 5.2 m/s (1 kt) lateral speed, 5.2 m/s (1 kt) vertical speed. The ROV must be capable of being launched in a sea state 4, recovered in a sea state 5, shipped on one truck without permit, and the launch system must provide a 2.4 m (8 ft) clearance from the ROV to the side of the support ship.

In this paper, a robust adaptive controller is designed for the dynamical positioning of a remotely operated vehicle (ROV) with unknown hydrodynamic coefficients and disturbances. Firstly, the Multiple Input Multiple Output (MIMO) system can be divided into several Single Input Single Output (SISO) systems for convenience of controller design. Then, a recurrent wavelet neural network (RWNN) with feedback loops is employed to approach the unknown part of the controller, and it can greatly reduce the number of neural network's inputs. Though the upper bounds of the network's approximation errors and disturbances are often used in the existed work, they are not necessary in this paper by presenting a special robust compensator. The stability analysis is given by Lyapunov theorem, and the tracking errors are proved to convergence to zero. Simulation result are presented for the ROV's positioning system, which indicate that the proposed controller has a good performance.

This paper reports the results of the kinematic redundancy resolution for the Baxter research robot arms. A robot manipulator arm is said to be kinematically redundant if it has more degrees of freedom than strictly needed for executing a given task. The redundant degrees of freedom can be used to achieve additional goals while the given task is executed. In this study, we will use cartesian velocity control to show that a Baxter robot arm can be programmed to improve its manipulability measure, avoid singularities or obstacles while its end effector follows the required six degrees of freedom motion trajectory.

In this paper, robust adaptive control strategies are designed for Underwater Remotely Operated Vehicles (ROVs) with velocity constraints. First, robust control strategies are investigated for under-water ROVs, and then adaptive robust control strategies are further developed with online parameter estimation. To prevent the velocity constraint violation, the Barrier Lyapunov Function (BLF) is employed in Lyapunov synthesis. By ensuring the boundedness of the BLF, we also guarantee that the velocity constraints are not transgressed. The stability analysis of the closed-loop system is provided and all closed-loop signals are ensured to be bounded. Simulation results for 5 degree-of-freedom (DOF) underwater ROV demonstrate the effectiveness of the proposed approach.

Redundant robotic manipulators under kinematic control may exhibit unpredictable behaviors at the joint level. When the end effector describes a closed trajectory, the joint angles may not return to their initial values. Likewise, final configuration in the joint space may depend on the trajectory that is followed by the end effector. In this paper, a complete parameterization of holonomic redundancy resolution techniques that avoid these problems is proposed. The flexibility of the proposed approach is discussed. In particular, it is shown that the selection of the redundancy resolution criterion is totally decoupled from the implementation of a closed-loop inverse kinematics (CLIK) algorithm. Any user-defined redundancy resolution criterion can, thus, be enforced. Potentialities of this new methodology are experimentally verified on an industrial robot in a case study where functional redundancy occurs and is applied in simulation on a 7-degree-of-freedom (7-DOF) anthropomorphic manipulator.

Empirical performance criteria based on geometric and physical properties are commonly used for real-time decision-making (and design) of redundant anthropomorphic manipulators (serial) or workcells (parallel) performing high level tasks while avoiding obstacles, providing safety, and responding to human commands. This requires configuration management of these complex systems by prioritizing candidate configurations relative to quantifiable secondary objectives with clear physical meanings. Clarity is addressed by using position, inertial, kinetic, and potential energy (gravity and deformation) based metrics that are crisply defined from system and input parameters. Scaling differences among derived performance metrics require normalization to determine their relative import and inclusion in multicriteria decision-making techniques. Large dimensional spaces mean statistically reduced representations are necessary to decipher their relative import and allow an operator without extensive robotic knowledge to use them effectively and independent of a redundancy resolution technique (RRT). We propose two global norms: the unit norm and the average norm for a broad set of performance criteria that quantify these systems’ unique constraint, transmission, and energy characteristics. These norms are then used to select relevant criteria for operational decision-making based on intuitive operator commands instead of abstract mathematical notions. Additionally, a modified RRT is presented that is more robust with respect to changes during operation in the secondary objectives, which allows for greater flexibility when formulating new criteria. Results are illustrated using a variety of new and existing criteria on an anthropomorphic dual-arm system.

This paper discusses designing and implementing an adaptive thrust distribution algorithm on the already robust control system for serial split-hull underwater vehicles to maximise operational efficiency. Split-hull underwater vehicles are gaining popularity in subsea operations due to their flexible hyper-redundant design and enhanced manoeuvrability. These features facilitate them to replace conventional solutions, including torpedo-shaped Autonomous Underwater Vehicles (AUVs) and Remotely Operated Vehicles (ROVs). The field of research is currently undergoing a considerable transition toward operations on subsea activities that are more economical and efficient. Thus, implementing a robust and energy-efficient control system is of utmost importance. The robust Super Twisting Algorithm (STA) based control system is used on the vehicle, and an adaptive thrust distribution algorithm is proposed and implemented to optimise the energy efficiency further. The work involves modelling the vehicle, fluid forces, torque effects, and thruster configuration matrix and implementing the adaptive weight distribution on the STA-based control system. With the help of simulations, the improvements in the control system are proved.

This paper presents the development of a haptic driving system for underwater Remotely Operated Vehicles (ROVs). Unlike conventional ROV driving systems, which only transmit commands from the pilots to the vehicle controller, the proposed haptic device has the ability to provide information about the working environment back to the operator via tactile sensing. In this paper, the drag force generated by the fluid interaction is chosen as the feedback objective for the haptic control. Hence, the haptic device helps the operator to sense the drag force via feedback through the joystick. A one degree of freedom (1-DOF) haptic joystick was developed to first control the surge motion of a simulated ROV model, with future work aimed at evaluation on an actual vehicle. The results of the haptic controller linked to the simulation model proved the feedback ability of the controller and identified areas of improvement, especially with regard to noise filtering.

To deal with complex disturbances and the presence of partial loss of propeller effectiveness in work-class remotely operated vehicles (ROVs), a method of robust fault tolerant control is proposed, which is based on adaptive sliding mode control. In this approach, adaptive technique is employed to estimate the bounds’ information of external complex disturbances and the effectiveness loss of the propeller. And a sliding mode controller is then designed to achieve fault tolerant control and external disturbance rejection. Corresponding stability of the closed-loop control system is analyzed using Lyapunov stability theory. Apply this method to trajectory tracking control of work-class ROVs, the simulation results validate that great fault tolerant capability and a good performance of external disturbance rejection can be achieved even under partial loss of propeller effectiveness.

In this paper, an input-output linearisation controller with an adaptive fuzzy outer loop is applied to the depth control of a nonlinear Remotely Operated Vehicle (ROV). The adaptive fuzzy system is added to increase the robustness as well as add 'intelligence' to conventional input-output controllers. The free control parameters are selected using multi-objective fuzzy genetic algorithm optimisation. Simulation results are presented which demonstrate that the proposed control scheme can enhance the closed-loop system performance by reducing the output tracking errors.

In this paper, an image-based uncalibrated visual servo scheme is proposed for image tracking tasks in highly disturbed environment, such as a remotely operated vehicle performing observation or investigation influenced by severe underwater current. Under the conditions of unknown target model and camera parameters, the control framework applies the scale invariant feature transform (SIFT) technique to extract image features. Furthermore, a robust adaptive control law is implemented to overcome the effect caused by camera parameters. Then by using three different types of camera’s motion: pan, tilt, and zoom to achieve the visual servo mission by maintaining the target always at the central position on the image plane.

Nowadays, the increasing availability of commercial off-the-shelf underwater acoustic and non-acoustic (e.g., optical and electromagnetic) modems that can be employed for both short-range broadband and long-range low-rate communication, the increasing level of autonomy of underwater vehicles, and the refinement of their underwater navigation systems pave the way for several new applications, such as data muling from underwater sensor networks and the transmission of real-time video streams underwater. In addition, these new developments inspired many companies to start designing hybrid wireless-driven underwater vehicles specifically tailored for off-shore operations and that are able to behave either as remotely operated vehicles (ROVs) or as autonomous underwater vehicles (AUVs), depending on both the type of mission they are required to perform and the limitations imposed by underwater communication channels. In this paper, we evaluate the actual quality of service (QoS) achievable with an underwater wireless-piloted vehicle, addressing the realistic aspects found in the underwater domain, first reviewing the current state-of-the-art of communication technologies and then proposing the list of application streams needed for control of the underwater vehicle, grouping them in different working modes according to the level of autonomy required by the off-shore mission. The proposed system is finally evaluated by employing the DESERT Underwater simulation framework by specifically analyzing the QoS that can be provided to each application stream when using a multimodal underwater communication system specifically designed to support different traffic-based QoSs. Both the analysis and the results show that changes in the underwater environment have a strong impact on the range and on the stability of the communication link.