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In this work, a six degrees-of-freedom (DOF) nonlinear kinematic and dynamic model of a Hybrid Autonomous Underwater Vehicle (H-AUV) is derived for the two modes of locomotion, propelled and gliding modes. A comprehensive linearization algorithm is developed to include both modes of locomotion. Starting with a three-dimensional time-parameterized curve of position history, Frenet-Serret frames are used to specify the unknown nominal states, which in turn are used to obtain the nominal inputs. A linear time-variant (LTV) state-space model is obtained, and a linear quadratic regulator (LQR) is designed and applied to the nonlinear model. The performance of the devised controller is assessed via a metric that computes the error between the actual and the desired position. Simulation results show that the LQR provides accurate tracking performance, even in the presence of underwater currents with bounded flow velocity. Moreover, the controller autonomously switches modes between propulsion and gliding to ensure minimal trajectory tracking error and energy consumption. [ABSTRACT FROM AUTHOR]

Off-highway vehicles have not received the same level of scrutiny that their on-highway counterparts did relative to safety, comfort, fuel economy, and automation. Over the past few decades, various active chassis safety control systems, architectures, and schemes have been researched and developed to improve the stability and handling of on-highway vehicles, including articulated vehicles such as tractor–trailer applications. In this paper, the authors investigate a yaw stability control system for articulated frame steering off-highway vehicles via novel steer-by-wire technology that they have recently developed. A high-fidelity vehicle dynamics model is derived while keeping the yaw rate decoupled from the lateral acceleration, in order to separate the primary path-following task (driver) from the secondary disturbance–attenuation task (controller). The control algorithm is then designed such that the two tasks do not hamper one another, and that the automatic controller is quickly activated for a short period of time to counteract instabilities, and then smoothly relinquishes control back to the human operator. Simulation and experimental testing results are obtained to validate the vehicle dynamics model, the control algorithm design, and the new system's efficacy in counteracting yaw instabilities on low-friction surfaces using standard vehicle dynamic maneuvers. [ABSTRACT FROM AUTHOR]

Stemmed by ever-increasing demand on fossil fuels and increased environmental awareness to reduce carbon emissions, improving the efficiency of components and systems has been receiving paramount attention in most industries during the past few years. This is especially true in the mobile machinery industry, which produces high power equipment with relatively low energy efficiency for the most part. Mobile machines strictly employ fluid power systems owing to the superlative power density of hydraulic components. Nevertheless, no major breakthrough technologies to significantly boost the efficiency of fluid power systems have emerged, except for the recent development of a throttle-less actuation technology, known as pump displacement control (DC), which has been proven to be an energy efficient alternative and a serious contender to state-of-the-art technologies. This paper deals with analyzing the energy efficiency of a DC steering system versus a more conventional valve controlled counterpart, which conveys how effectively the two systems convert the chemical energy stored in the diesel fuel into useful mechanical energy. Experimental testing on a prototype test vehicle showed that DC steering results in 14.5% fuel savings, 22.6% productivity gain, and a grand total of 43.5% fuel usage efficiency increase. [ABSTRACT FROM AUTHOR]

Increased environmental awareness and skyrocketing fuel prices have pressed researchers and engineers to find energy efficient alternatives to traditional approaches. A novel steer-by-wire technology, which is based on pump displacement control actuation, has been proposed by the authors and was shown to improve the fuel efficiency of a wheel loader steering system by 43.5%. Building on this realization, the work in this paper deals with designing an adaptive velocity controller, which takes the forni of an indirect self-tuning regulator that has the facility to cope with parametric uncertainties and uncertain nonlinearities associated with hydraulically actuated systems. The indirect self-tuning regulator algorithm is selected given that the uncertain plant parameters are estimated in the process, which is a useful byproduct that gives insight into system properties that will be considered in future investigation. Furthermore, a discrete adaptive control law with low computational cost is required for the application on hand. The designed self-tuning regulator and the estimation algorithm were validated in numerical simulations as well as experimentally on a designated prototype test vehicle, demonstrating the effectiveness of the proposed adaptive scheme in the face of uncertainties. The controller was able to adapt to varying load mass and inertia, which correlate to varying operating conditions that influence the system dynamics. Hence, besides offering improved fuel efficiency, the new steering technology also results in smarter machines. [ABSTRACT FROM AUTHOR]

Steer-by-wire technologies remain under rigorous research and development given the advantages that they offer over their traditional counterparts. The spectrum of steering systems encompasses applications in the automotive, construction, agricultural, and aerospace industries, to name a few. An original electro-hydraulic steer-by-wire technology based on pump displacement control actuation, an energy efficient alternative to conventional valve control, has been previously proposed by the authors. The new concept was validated and implemented on an articulated steering prototype test vehicle, and resulted in significant fuel savings and machine efficiency increase. This paper investigates the notion of virtual sensing relative to estimating the vehicle?s yaw rate by only measuring the articulation angle and vehicle speed. Virtual sensing is a promising concept for yaw stability control and is an attractive option for vehicle manufactures as it reduces sensor cost, maintenance, and machine downtime. The designed yaw rate sensor is validated in simulation as well as on a test vehicle by devising appropriate steering maneuvers. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) are reaching offshore. In this work, we formulate the novel problem of a marine locomotive quadrotor UAV, which manipulates the surge velocity of a floating buoy by means of a cable. The proposed robotic system can have a variety of novel applications for UAVs where their high speed and maneuverability, as well as their ease of deployment and wide field of vision, give them a superior advantage. In addition, the major limitation of limited flight time of quadrotor UAVs is typically addressed through an umbilical power cable, which naturally integrates with the proposed system. A detailed high-fidelity dynamic model is presented for the buoy, UAV, and water environment. In addition, a stable control system design is proposed to manipulate the surge velocity of the buoy within certain constraints that keep the buoy in contact with the water surface. Polar coordinates are used in the controller design process since they outperform traditional Cartesian-based velocity controllers when it comes to ensuring correlated effects on the tracking performance, where each control channel independently affects one control parameter. The system model and controller design are validated in numerical simulation under different settings, configurations, and wave scenarios. [Display omitted] • A novel robotic system where a UAV manipulates a buoy's velocity by means of a cable. • A tethered UAV-buoy system with advantages over USVs. • A multi-physics dynamic model for marine robotics. • An advanced control system for marine locomotion supervised by a state-machine. • A controller based on polar coordinates for enhanced tracking performance. [ABSTRACT FROM AUTHOR]