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In robot-assisted oral surgery, the surgical tool needs to be fed into the target position to perform surgery. However, unmodeled extraoral and complex intraoral environments bring difficulties to motion planning. Meanwhile, the motion is operated manually by the surgeon, causing relatively limited accuracy as well as the risk of misoperation. Moreover, the random movements of the patient's head bring additional disturbance to the task. To achieve the task, a motion strategy based on a new conical virtual fixture (VF) was proposed. First, by preoperatively specifying a conical guiding cone as the VF, virtual repulsive forces were applied on the out-of-range end effector. Then, based on the two-point adjustment model and velocity conversion, the effect of VF was established to prevent the end-effector from exceeding the constraint region. Finally, a vision system corrects the guiding cone to compensate for the random movement of the patient's head to feed to a dynamic target. As an auxiliary framework for surgical operation, the proposed strategy has the advantages of safety, accuracy, and dynamic adaptability. Both simulations and experiments are conducted, verifying the feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

In this paper, the H∞ and H2 time-varying formation tracking problems for multi-agent systems with directed topologies in the presence of external disturbances are investigated. The followers need to achieve the desired time-varying formation during movement and simultaneously track the state trajectory generated by the leader. First, a distributed consensus protocol based on the local state information of neighbors of the agents for solving H∞ and H2 time-varying formation tracking problems are proposed without utilizing global information about the entire agents. The conditions to achieve H∞ and H2 time-varying formation tracking in the presence of external disturbances are suggested respectively. Then, to determine the parameters of the designed protocol which satisfy suitable conditions, algorithms for H∞ and H2 time-varying formation tracking in the form of pseudo-code are presented, respectively. Furthermore, the proofs of the proposed theorems are derived by utilizing algebraic graph theory and Lyapunov analysis theory tools to demonstrate the closed-loop stability of the system in the presence of external disturbances. Finally, the usefulness and effectiveness of the approaches proposed are demonstrated by numerical simulation examples. [ABSTRACT FROM AUTHOR]

Bionic pectoral fins play an essential role in achieving the superior swimming ability of the bio-inspired undersea monitoring platform by producing desired movements and propulsion forces. This paper discusses the hydrodynamic modelling and experiments of a bionic pectoral fin inspired by the cownose ray. A simplified hydrodynamic model of the oscillatory bionic pectoral fin is built. A physical prototype of the bionic pectoral fin is developed based on the structure and movement parameters extracted from the cownose ray. Performances of the bionic pectoral fin in producing lift force and propulsion force are tested using a towing-tank experimental platform and compared with the results from corresponding simulations. Feasibility of the hydrodynamic simulation and the bionic design method are verified. [ABSTRACT FROM AUTHOR]