|RO 1||Distributed Data Fusion for Multirobot Search||This paper presents novel data fusion methods that enable teams of vehicles to perform target search tasks without
guaranteed communication. Techniques are introduced for merging estimates of a target’s position fromvehicles that regain contact after long periods of time, and a fully distributed team-planning algorithm is proposed, which utilizes limited shared information as it becomes available. The proposed data fusion techniques are
shown to avoid overcounting information, which ensures that combining data from different vehicles will not decrease the performance of the search.Motivated by the underwater search domain, a realistic underwater acoustic communication channel is used to determine the probability of successful data transfer between two locations. The channel model is integrated into a simulation of multiple autonomous vehicles in both open water and harbor environments. The results demonstrate that the proposed distributed
coordination techniques provide performance competitive with full
|RO 2||Multirobot Rendezvous Planning
for Recharging in Persistent Tasks
|This paper addresses a multirobot scheduling problem in which autonomous unmanned aerial vehicles (UAVs) must be recharged during a long-term mission. The proposal is to introduce a separate team of dedicated charging robots that the UAVs can dock with in order to recharge. The goal is to schedule and plan minimum cost paths for charging robots such that they rendezvous with and replenish the UAVs, as needed, during the mission. The
approach is to discretize the 3-D UAV flight trajectories into sets of projected charging points on the ground, thus allowing the problem to be abstracted onto a partitioned graph. Solutions consist of charging robot paths that collectively charge each of the UAVs. The problem is solved by first formulating the rendezvous planning problem to recharge each UAV once using both an integer linear program and a transformation to the Travelling Salesman Problem. The methods are then leveraged to plan recurring rendezvous’
over longer horizons using fixed horizon and receding horizon strategies. Simulation results using realistic vehicle and battery models demonstrate the feasibility and robustness of the proposed approach.
|RO 3||Closed-Loop Control of Local Magnetic Actuation for Robotic Surgical Instruments||We propose local magnetic actuation (LMA) as an approach to robotic actuation for surgical instruments. An LMA actuation unit consists of a pair of diametrically magnetized singledipole cylindrical magnets, working as magnetic gears across the abdominalwall. In this study,we developed a dynamic model for an LMA actuation unit by extending the theory proposed for coaxial magnetic gears. The dynamic model was used for closed-loop control, and two alternative strategies—using either the angular velocity at the motor or at the load as feedback parameter—were compared. The amount of mechanical power that can be transferred across the abdominal wall at different intermagnetic distances was also investigated. The proposed dynamicmodel presented a relative
error below 7.5% in estimating the load torque from the system parameters. Both the strategies proposed for closed-loop control were effective in regulating the load speed with a relative error below 2%of the desired steady-state value. However, the load-side closed-loop control approach was more precise and allowed the system to transmit larger values of torque, showing, at the same time, less dependence from the angular velocity. In particular, an average value of 1.5 mN·m can be transferred at 7 cm, increasing up to 13.5 mN·m as the separation distance is reduced down to 2 cm. Given the constraints in diameter and volume for a surgical instrument, the proposed approach allows for transferring a larger amount of mechanical power than what would be possible to achieve by embedding commercial dc motors.
|RO 4||Hand Impedance Measurements During Interactive Manual Welding With a Robot||This paper presents a study of hand impedance measurements comparatively across ten professional and 14 novice
manual welders, when they are performing tungsten inert gas (TIG) welding interactively with the KUKA lightweight robot arm (LWR). The results show that hand impedance differs across professional
and novice welders. The welding torch is attached to the KUKA LWR, which is admittance controlled via a force sensor to give the feeling of a free floating mass at its end-effector. The subjects perform TIG welding on 1.5-mm-thick stainless steel plates by manipulating the torch. Impedance is measured by introducing
external force disturbances and fitting a mass–damper–spring model to human hand reactions. The quality of welding is measured using the variance of the position signals above 0.1 Hz. Professional welders demonstrate less variance and, in general, apply larger hand impedance (larger damping and stiffness) than the
novice welders. The variance of position during nominal welding is minimal for both professional and novice welders in the direction perpendicular to the welding line in the plane of the plate, which is the most important direction for the quality of the weld. For both professional and novice welders, the mass and damping values are
largest in this direction compared with the other two directions. Professional welders demonstrate larger damping than the novice welders in this direction.