Research on UUV's heading control based on adaptive robust PD control principle

Modern spacecraft are often equipped with large-scale, complex, and lightweight solar arrays whose deployment involves a highly dynamic movement. This paper proposed a novel adaptive proportional-derivative typed fuzzy logic control scheme for the attitude stabilization of a flexible spacecraft during the deployment of a composite laminated solar array. First, a constrained rigid-flexible coupling spacecraft model consisting of a rigid main body and a flexible solar array was proposed. The solar array, which is composed of composite laminated shells, was described by the absolute nodal coordinate formulation. Then, the detailed derivation of the adaptive fuzzy PD controller for attitude stabilization of the spacecraft was discussed. In addition, the spacecraft dynamic model which integrated the adaptive fuzzy PD controller was derived as a set of differential-algebraic equations. Several simulations were developed to investigate the solar array deployment dynamics and to verify the effectiveness of the proposed adaptive fuzzy PD controller. The results suggested that the proposed dynamic model is able to exactly describe the deployment dynamics of the composite laminated solar array. The solar array deployment causes obvious translational and rotational motions of the spacecraft. The proposed adaptive fuzzy PD control scheme has better performance in terms of the control precision and time response in stabilizing spacecraft during the deployment of the composite laminated solar array, comparing with that of the conventional PD controller.

Simple conventional control methods, such as PD and PID controllers, are widely used in industrial applications. Such controllers exhibit poor performance when applied to systems containing nonlinearities arising from unknown deadzones. In this article, we propose a novel fuzzy logic-based precompensation approach for controlling systems with deadzones. The control structure consists of a fuzzy logic-based precompensator followed by a conventional PD controller. Our proposed control scheme shows superior transient and steady-state performance compared to conventional PD and PID controllers. In addition, the scheme is robust to variations in deadzone nonlinearities, as well as the steady-state gain of the plant. We illustrate the effectiveness of our scheme using computer simulation examples.

Underwater operating platforms face difficulties regarding power supply and communications. To overcome these difficulties, this study proposes a hybrid surface and underwater vehicle (HSUV) and presents the development of the platform, control algorithms, and results of field tests. The HSUV is capable of supplying reliable power to the unmanned underwater vehicle (UUV) and obtaining data in real time by using a tether cable between the UUV and the unmanned surface vehicle (USV). The HSUV uses global positioning system (GPS) and ultra-short base line sensors to determine the relative location of the UUV. Way point (WP) and dynamic positioning (DP) algorithms were developed to enable the HSUV to perform unmanned exploration. After reaching the target point using the WP algorithm, the DP algorithm enables USV to maintain position while withstanding environmental disturbances. To ensure the navigation performance at sea, performance tests of GPS, attitude/heading reference system, and side scan sonar were conducted. Based on these results, manual operation, WP, and DP tests were conducted at sea. WP and DP test results and side scan sonar images during the sea trials are presented.

Although it was recognized that an unmanned underwater vehicle (UUV) in reality might experience changing ocean current along its mission trajectory, most published papers related to the single beacon underwater navigation assumed a constant ocean current over the whole duration. When this assumption is against the reality, those underwater tracking models not only will fail to adequately describe the change of ocean current over the duration, but also may introduce large error to their position estimation. In this paper, by including adequate ocean current uncertainty in the process model at each discrete time, the estimated ocean current can exhibit timevarying and location-dependent characteristics. The effect on the accuracy of underwater tracking due to the inclusion of the ocean current uncertainty is investigated through a kinematic model that treats the unknown effective sound velocity (ESV) as a state variable. In addition to the Kalman filter, the performance of the corresponding Rauch-Tung-Striebel (RTS) smoother is also studied. Both simulation and filed data are used to study the effect on the accuracy of underwater tracking.

The widespread use of Unmanned Underwater Vehicles (UUVs) in seafloor observatory networks highlights the need for docking stations to facilitate rapid recharging and effective data transfer. Floating docks are promising due to their flexibility, ease of deployment, and recoverability. To enhance understanding and optimize UUV docking with floating docks, we employ dynamic fluid body interaction (DFBI) to construct a seabed moored suspended dock (SMSD) model that features a guiding funnel, a suspended body, and a catenary of a mooring chain. This model simulates SMSD equilibrium stabilization in various ocean currents. Then, a UUV docking model with contact coupling is developed from the SMSD model to simulate the dynamic contact response during docking. The accuracy of the docking model was validated using previous experimental data. Through investigation of the UUV docking response results, sensitivity studies relating to volume, moment of inertia, mass, and catenary stiffness were conducted, thereby guiding SMSD optimization. Finally, sea tests demonstrated that the SMSD maintained stability before docking. During docking, the SMSD’s rotation facilitated smooth UUV entry. After the UUV docked, the SMSD was restored to its original azimuth, confirming its adaptability, stability, and reliability.

With the development of the unmanned marine systems, autonomous recovery of Unmanned Underwater Vehicles(UUV) based on the Unmanned Surface Vehicles(USV) has become an important research field. Comparatively analyzing the current mainstream recovery methods, this paper proposes a new recovery scheme based on the previous research results. In this scheme, one end of the cable is connected to a winch fixed to the USV and the other is connected to the V-shaped wing, which can provide downward pressure to keep the line tight, and the rudders mounted on it can be adjusted to assure the attitude stability, which facilitate Docking and Line Capture Line Recovery(LCLR) of the UUV. After structure optimization, the V-shaped wing was modeled in hydrodynamic software STAR-CCM+. The numerical simulation shows that the improved V-shaped wing can provide about 20N downward pressure when the towing speed is 2 knots. In order to improve the reliability of the LCLR system and reduce mechanism sticking, a new type of capture mechanism is designed and it is driven by two motor respectively instead of just one. Besides, the LED beacon ranging tests were conducted in the Xiu Lake. It shows the accuracy of optical guidance algorithm is 2%, and the maximum optical recognition distance is 16m in the air and 10m in the clean water, which satisfies the docking accuracy. From October 2018, two Lake tests were carried out in Xiu Lake in Shenyang and Qiandao Lake in Hangzhou. The performance of the LCLR system was tested, and the V-shaped wing was towed at different speeds range from 1 to 1.5 knots and the length of the cable is 8m. The results show the V-shaped wing can maintain depth and attitude stability. Finally, through the improved acousto-optic joint guidance algorithm, the docking process is successfully completed and the Towed Line and Cable were captured by the UUV line capture mechanism on nose. The feasibility of the presented recovery scheme was indicated by the results from the two trials, which has a certain guiding significance for the dynamic recovery of an UUV in the future.

A consensus algorithm proposed in the paper is applied to tackle remarkable problems of unmeasurable velocities, the environmental disturbances, and the limited communication environment for the multiple unmanned underwater vehicles (multi-UUVs). Firstly, for a complex nonlinear and coupled model of the unmanned underwater vehicle (UUV), a technique of feedback linearization is developed to transform the nonlinear UUV model into a second-order integral UUV model. Secondly, to address the problem of the unavailable velocity information and environmental disturbances for the multi-UUVs system, we design a distributed extended state observer (DESO) to estimate the unmeasurable velocities and environmental disturbances using the relative position information. Finally, we propose a protocol based on the estimation information from the DESO and demonstrate that the multi-UUVs system with the switching directed topologies under the protocol can reach consensus asymptotically. The theoretical result proposed in the literature is verified by one numerical example.

In this paper we present PD-AFC (proportional, derivative-active force control) on unmanned hexacopter that has a robust nature to remain the disorder on one propeller and fluctuated disturbance. Hexacopter uses PD controller to achieve stability and AFC to generate a robust disturbance rejection. Gain scheduling method are used in adaptive control to tune PD controller. Based on the results obtained by simulation, hexacopter has stabilized using PD controller. Hexacopter able to robust with PD-AFC of 0.5 on fluctuated disturbance and able to adapt to maintain altitude using adaptive PD controller.

Finite-time sideslip observer-based synchronized path-following control of multiple unmanned underwater vehicles

Unmanned Underwater Vehicles (UUVs) are commonly used in Oceanography due to their relative low cost and wide range of capabilities. Gliders are a type of UUV particularly suitable for long-range missions because of their large autonomy. They change their buoyancy to dive and climb describing a vertical saw tooth pattern, which produces an effective but low horizontal speed. Consequently, gliders are strongly sensitive to ocean currents, so they might have to adapt the heading to the current field. In this article we outline a novel path planning algorithm for gliders using ocean currents. It bases on the A* family of algorithms and incorporates a probabilistic framework. Our approach intends to alleviate some of the drawbacks that A* has with the problem at hand. Instead of discretizing the search space, a set of bearing angles is sampled at each surfacing point and the glider trajectory is integrated. We propose an Adaptive Bearing Sampling (ABS) procedure which reduces the computational time with low impact on the results, as shown by the tests run with ocean currents of a Regional Ocean Model.

Robust fixed-time H∞ tracking control of UUVs with partial and full state constraints and prescribed performance under input saturation

In the last decade, a great effort has been employed in the study of Hybrid Unmanned Aerial Underwater Vehicles, robots that can easily fly and dive into the water with different levels of mechanical adaptation. However, most of this literature is concentrated on physical design, practical issues of construction, and, more recently, low-level control strategies. Little has been done in the context of high-level intelligence, such as motion planning and interactions with the real world. Therefore, we proposed in this paper a trajectory planning approach that allows collision avoidance against unknown obstacles and smooth transitions between aerial and aquatic media. Our method is based on a variant of the classic Rapidly-exploring Random Tree, whose main advantages are the capability to deal with obstacles, complex nonlinear dynamics, model uncertainties, and external disturbances. The approach uses the dynamic model of the HyDrone, a hybrid vehicle proposed with high underwater performance, but we believe it can be easily generalized to other types of aerial/aquatic platforms. In the experimental section, we present simulated results in environments filled with obstacles, where the robot is commanded to perform different media movements, demonstrating the applicability of our strategy.

Unmanned underwater vehicles are crucial for deep-sea exploration and inspection without imposing any danger to human life due to extreme environmental conditions. But, designing a robust controller that can cope with model uncertainties, external disturbances, and time delays for such vehicles is a challenge. This paper implements a sliding mode position control algorithm with a time-delay estimation term to a remotely operated underwater vehicle to deal with disturbances, such as waves, and time delays. The controller is implemented on an underwater vehicle (BlueRov) and compared with a proportional-integral-derivative (PID) controller in a wave tank with different disturbances and when there exist delays within the communication channel. The experimental results show that the proposed control method provides better performance than the conventional PID in the presence of extreme disturbances with less control efforts.

Beam-Based Tether Dynamics and Simulations using Finite Element Model

Aircraft are non-minimum phase, MIMO and highly nonlinear systems which undergo significant disturbances and variation in system parameters during operation. In spite of the prosperous literature in adaptive control, application of the promising control strategy on aircraft control has been restricted by the lack of assurance in closed-loop stability. This paper proposes a robust adaptive control scheme for aircraft. The scheme is composed of an inner-level adaptive fuzzy PD control law and an outer-level supervisory control law. Importantly, the outer-level controller of the two-level scheme is designed based on a fuzzy model which takes non-minimum phase phenomena and modeling error explicitly into account. Numerical studies of the tracking control of a five degree of freedom aircraft system demonstrate the effectiveness of the proposed control strategy in the face of bursting disturbances.