In this paper, suffering from both complex uncertainties and underactuations, $accurate$ trajectory tracking control problem of an asymmetric underactuated surface vehicle (AUSV) is first addressed by guiding yaw dynamics which are $free of persistent excitation (PE)$ . Using nested coordinate transformations, the AUSV is formulated in a cascade structure consisting of translation and rotation subsystems with complex uncertainties. Finite-time uncertainty observers (FUOs) are devised to exactly estimate transformed uncertainties, and enable $separation principle$ in controller and observer syntheses. By virtue of creating yaw-guided dynamics, rotation tracking is shaped to stabilize yaw and sway tracking discrepancies, simultaneously, in collaboration with yaw controller. Nominal dynamics of translation tracking errors are globally asymptotically stabilized by surge control synthesis using cascade analysis and Lyapunov approach, and thereby contributing to global asymptotic stability of the entire translation-rotation tracking system. Eventually, an FUO-based yaw-guided tracking control (FUO-YTC) scheme of an AUSV with complex uncertainties is established. Simulation studies demonstrate remarkable performance.

In this paper, a novel translation-rotation cascade control (TRCC) scheme is developed for path-following of an autonomous underactuated ship suffering from unknown sideslip and complex disturbances. Salient contributions are as follows: (1) Finite-time observers are devised to exactly estimate lumped unknowns including sideslip, disturbances and virtual yaw acceleration. (2) Complex unknowns are compositely compensated with finite-time convergence such that exact path-following with accurate unknown-rejection is achieved. (3) In lieu of detached guidance-control design in previous works, the TRCC facilitates integrated guidance-control (IGC) system in a cascade manner. (4) Combining cascade analysis with Lyapunov approach, the entire IGC system is ensured to be globally uniformly asymptotically stable. Both simulation and experimental results are provided to validate superiority of the proposed TRCC scheme.

In this paper, a challenging problem of full-state regulation control (FSRC) for an asymmetric underactuated surface vehicle (AUSV) suffering from disturbances is solved. The FSRC objective is divided into 2 sub-tasks, i.e., reaching trajectory (RT) guidance and tracking controller synthesis with underactuation and disturbances. The RT guidance is achieved by devising a circular orbit (CO) accurately passing through the desired full-state waypoint (FWP). Using a series of coordinate transformations, tracking error dynamics are shaped in a translation-rotation cascade form with respect to the CO-center frame. Using finite-time approach, lumped disturbances are accurately estimated by exact observers which facilitate synthesizing surge and yaw controllers. By creating a new coordinate, translation subsystem is converted to a lower-triangular form. Combining with backstepping technique, cascade analysis and Lypunov approach, translation and rotation controllers are derived systematically, and render the entire closed-loop FSRC system globally asymptotically stable. Hence, the AUSV is regulated to the desired FWP. Simulation studies on a benchmark AUSV are conducted to demonstrate remarkable performance.

Detection of living microalgae cells is very important for ballast water treatment and analysis. Chlorophyll fluorescence is an indicator of photosynthetic activity and hence the living status of plant cells. In this paper, we developed a novel microfluidic biosensor system that can quickly and accurately detect the viability of single microalgae cells based on chlorophyll fluorescence. The system is composed of a laser diode as an excitation light source, a photodiode detector, a signal analysis circuit, and a microfluidic chip as a microalgae cell transportation platform. To demonstrate the utility of this system, six different living and dead algae samples (Karenia mikimotoi Hansen, Chlorella vulgaris, Nitzschia closterium, Platymonas subcordiformis, Pyramidomonas delicatula and Dunaliella salina) were tested. The developed biosensor can distinguish clearly between the living microalgae cells and the dead microalgae cells. The smallest microalgae cells that can be detected by using this biosensor are 3 μm ones. Even smaller microalgae cells could be detected by increasing the excitation light power. The developed microfluidic biosensor has great potential for in situ ballast water analysis.