Zhou Jiajia

Mission and motion control of AUV for terrain survey mission using discrete event system theory

This paper presents the mission and motion control method of an Autonomous Underwater Vehicle (AUV) for ocean terrain survey. The motion modes of AUV in the terrain survey mission are analyzed and defined, including: way-point tracking motion and trajectory tracking motion. For terrain survey mission, AUV needs to track a series of points and paths in horizontal plane and keeps depth in vertical plane. The motion control of AUV in the two motion modes are introduced briefly. Because of series of paths in terrain survey mission for AUV to track, so, there must be a mission control as path changed. When AUV sails from one path to another path or from one point to another point, its state is changed which may be cause poor tracking result. In order to keep optimal terrain survey task, this paper proposes a mission control method using discrete event system (DES) theory by treating the path change as an event transition. Petri net (PN) formalism is used to model and describe the whole mission, specially, when the path changes. At last, simulations in normal and degraded situations are established to verify the method mentioned above. The simulation results indicate that the method is feasibility and effectiveness for AUV.

Coordinate control of multi-UUVs formation under double independent topologies with time-vary delays

This paper provides a new method which uses consensus algorithm to solve the coordinate control problems of multi-UUVs in the case of leaderless formation. As band width is constraint in the water, a new topology method is proposed which divides the communication topologies into two independent parts, position communication topology and velocity communication topology. And in the novel communication topologies there are different time-varying delays. In additions, the math model of UUV is nonlinear and coupled. With the help of state feedback linearization method, the nonlinear math model of UUV can be transferred into a double-integrator dynamic model. Based on the result of linearized model, the UUVs formation coordinate control can be regarded as a consensus problem with time-varying communication delays. As a result, sufficient conditions for the stability of system are proposed and they are proven by using the Laypunov-Razumikhin theorem. In the end, the simulation results are presented to confirm and illustrate the theoretical results.

Observer based 3-D path following control of underactuated underwater vehicle in the presence of ocean currents

Spatial path following is an important but difficult technology for underwater vehicle in the complicated ocean environment, especially for an underactuated vehicle. This paper addresses the problem of 3-D Path Following of an underactuated underwater vehicle in the presence of constant unknown ocean currents. The nonlinear controller including dynamics and kinematics levels assuming that there is no current are derived firstly. The controller steers the vehicle along the path and make position and velocity errors between vehicle and virtual reference point on path converge to zero. Then, considering currents as the disturbance to vehicle kinematics, an observer is designed to obtain the unknown current estimate. The kinematics controller is revised to compensate the errors caused by the currents. Simulation results with and without currents are presented. The results show that the controllers and observer designed in this paper are effective and performing well.

Coordinate control of multi-AUVs under double independent topologies and time delay

This paper introduces a new method which uses the consensus algorithm to solve the coordinate control problems of multi-AUVs. As the communication between the AUVs is difficult and easy to be interfered under the water, there must be time delay and data drop during the members communicate with each other. On the other hand, the math model of AUV is nonlinear and coupling, the feedback linearization can be used to make the complex model of AUV into double-integrator dynamic. With this simplified math model, the AUV formation coordinate control can be regarded as consensus problem. In addition, the double independent position and velocity topologies are used to responded to the shortage of bandwidth in real communication under the water.