Underactuated systems like sea vessels have degrees of motion that are insufficiently matched by a set of independent actuation forces. In addition, the underlying trajectory-tracking control problems grow in complexity in order to decide the optimal rudder and thrust control signals. This enforces several difficult-to-solve constraints that are associated with the error dynamical equations using classical optimal tracking and adaptive control approaches. An online machine learning mechanism based on integral reinforcement learning is proposed to find a solution for a class of nonlinear tracking problems with partial prior knowledge of the system dynamics. The actuation forces are decided using innovative forms of temporal difference equations relevant to the vessel's surge and angular velocities. The solution is implemented using an online value iteration process which is realized by employing means of the adaptive critics and gradient descent approaches. The adaptive learning mechanism exhibited well-functioning and interactive features in react to different desired reference-tracking scenarios.

China agreed Saturday to return an American sea drone it had captured after the Pentagon demanded it back, defusing tensions at the end of a week of confrontations over Beijing's territorial ambitions in the South China Sea. China's Defense Ministry said it would return "in an appropriate manner" the U.S. sea vessel seized this week by the Chinese navy. But the ministry also accused the U.S. of "public hyping" that was "not conducive to solving the problem smoothly." Chinese officials did not specify what happened or when Beijing would hand back the device. The ministry, in a statement, said that the device was unidentified when found and that officials later concluded it was an American drone.

China agreed Saturday to return an American sea drone it had captured after the Pentagon demanded it back, defusing tensions at the end a week of confrontations over Beijing's territorial ambitions in the South China Sea. China's Defense Ministry said it would return "in an appropriate manner" the U.S. sea vessel seized this week by the Chinese navy. But the ministry also accused the U.S. of "public hyping" that was "not conducive to solving the problem smoothly." Chinese officials did not specify what happened or when Beijing would hand back the device. The ministry, in a statement, said the device was unidentified when found and that officials later concluded it was an American drone.