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SUMMARYThis paper first presents a method of motion planning and implementation for the self-recovery of an overturned six-legged robot. Previous studies aimed at the static and dynamic stabilization of robots for preventing them from overturning. However, no one can guarantee that an overturn accident will not occur during various applications of robots. Therefore, the problems involving overturning should be considered and solved during robot design and control. The design inspirations of multi-legged robots come from nature, especially insects and mammals. In addition, the self-recovery approach of an insect could also be imitated by robots. In this paper, such a self-recovery mechanism is reported. The inertial forces of the dangling legs are used to bias some legs to touch the ground, and the ground reaction forces exerted on the feet of landing legs are achieved to support and push the body to enable recovery without additional help. By employing the mechanism, a self-recovery approach named SSR (Sidewise-Self-Recovery) is presented and applied to multi-legged robots. Experiments of NOROS are performed to validate the effectiveness of the self-recovery motions. The results show that the SSR is a suitable method for multi-legged robots and that the hemisphere shell of robots can help them to perform self-recovery.

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This paper investigates the performance analysis for a novel covert communication system, where a friendly UAV-jammer is used to protect the covert transmission from Alice to Bob against the eavesdropping from Dave. In particular, by exploiting the spatial diversity, the UAV can emit artificial noise (AN) to complicate the noise uncertainty at Dave. In this letter, two scenarios are studied, where the channels from Alice to Bob and Dave experience 1) AWGN and 2) Nakagami-m fading. The closed-form expression for privacy rate expression under AWGN is derived, where evaluating the condition for achieving a positive gain of using UAV-jammer. Furthermore, under the Nakagami-m fading scenario, an approximate expression of ergodic privacy rate is obtained by using Taylor expansion. In the end, simulation results show that significant performance gain in terms of privacy rate can be achieved by employing UAV-jammer for covert communication.

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SUMMARYIn order to provide a novel approach for the operational problems of walking robots, this paper presents a method by which a hexapod robot uses its legs to manipulate an object, and this involves the following two steps. First, two adjacent legs are used to manipulate the object. Next, the supporting legs are required to assist the arms to obtain high manipulability. The manipulation constraints, workplaces, and kinematic models are analyzed using screw theories. Moreover, an optimization algorithm is proposed to reduce energy consumption under stability constraints. We also introduce a manipulation control model that simultaneously considers the supporting and operating legs. Finally, the validity of these methods is proved by the results of experiments and simulations.