Although communication delays can disrupt multiagent systems, most of the existing multiagent trajectory planners lack a strategy to address this issue. State-of-the-art approaches typically assume perfect communication environments, which is hardly realistic in real-world experiments. This paper presents Robust MADER (RMADER), a decentralized and asynchronous multiagent trajectory planner that can handle communication delays among agents. By broadcasting both the newly optimized trajectory and the committed trajectory, and by performing a delay check step, RMADER is able to guarantee safety even under communication delay. RMADER was validated through extensive simulation and hardware flight experiments and achieved a 100% success rate of collisionfree trajectory generation, outperforming state-of-the-art approaches.

The multiphysics model of ionic polymer-metal composite (IPMC) sensors proposed by Zhu has a significant advantage of being able to describe the dynamic sensor response, which highly depends on humidity, by explicitly considering solvent dynamics. However, it is difficult to perform analysis and simulation because Zhu’s model is represented by complex non-linear partial differential equations. This paper describes the symbolic finite element discretization of Zhu’s model and further discusses the essential dynamics of the reduced-order model extracted from the finite element model. The obtained linear ordinary differential equations, or the state equation, can be easily implemented in simulators via common programming languages. The simulation results of an in-house simulator implemented by MATLAB code show good agreement with those of direct numerical simulation by using commercial software, COMSOL. To further simplify the model, the minimum order required for an appropriate approximation is numerically investigated by using a model order reduction technique. This paper reveals that the dynamic response of an IPMC sensor can be consequently approximated by a first-order or second-order linear time-invariant system.

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This paper proposes a simple but effective method for characterizing dielectric elastomer actuators (DEAs), especially for thin stacked DEAs, which are promising for haptic devices but which measure the dynamic elastic modulus with great difficulty. The difficulty of the measurement of such a thin stacked DEA arises from the friction and local deformation of the surface between the DEA and a contact, as shown in this paper. In the proposed method, a DEA is vertically suspended and a weight is attached to it. The proposed method requires no contact with the surface of a DEA and uses only a weighting mass. Experimental results demonstrated the proposed method can estimate almost essential constants, such as the dynamic elastic modulus (Young’s modulus and damping time constant), the electrical constants (permittivity and resistivity), and the coefficient of electromechanical coupling, through the forced vibration induced by voltage actuation.

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