Towards Effective and Efficient Sensing-Motion Co-Design of Swarming Cyber-Physical Systems

Abstract:

The overall research objective of the project is to establish and demonstrate a generic motion sensing co-design procedure that significantly reduces the complexity of mission design for swarming CPS, and greatly facilitates the development of effective and efficient control and sensing strategies. The objective of the project will be achieved through the integration of three main components: the design of cooperative control and sensing strategies, the development of Magneticinduction-based underwater communication and localization technique, and the design of smartmaterial actuated biorobotic fish. Source seeking is one of the fundamental and representative missions for swarming CPS with a wide range of practical applications. To achieve source seeking with maximum convergence speed with limited resources, we propose a dual-module control approach that achieves fast source seeking using nonholonomic mobile robots. The key idea is velocity decomposition. We design the angular velocities of the two robots to keep them in a formation, and the linear velocities to be determined by the instantaneous measurements of the field value without gradient estimation. The method makes full use of the maximum speed of the robots to achieve fast overall convergence rate to the source with only two robots and reduced computational and communication cost. The proposed approach is validated in a multi-robot testbed. Collision avoidance is an important requirement in vehicle swarms. We employ the collision cone approach to determine analytical guidance laws for collision avoidance. These analytical guidance laws lead to computational savings on resource-constrained robotic platforms. These guidance laws are determined for objects of arbitrary shapes, and do not require the objects to be approximated by circles/polygons as is commonly done in the literature. Besides collision avoidance, the collision cone approach has also been used for: analytical laws governing safe trajectories for a robot to make a precision 3-D maneuver through a small orifice, and analytical laws for area coverage by mobile robot sensor networks. To provide an enabling mobile platform to verify the proposed strategies, we develop a 2D maneuverable robotic fish propelled by multi-IPMC fins. One caudal fin is used for forward swimming. Two pectoral fins are used for turning. A wireless control system is developed for controlling the speed and direction of the swimming robotic fish, where a Xbee device is used for receiving commands from a PC station. We have fabricated the robotic fish at Wichita State University. The total weight of the robot was 290 grams. We have tested the robotic fish in a water tank. The free swimming tests show that the robotic fish can achieve 0.5 cm/sec forward speed and 1.5 rad/sec turning speed. To allow robotic fish to exchange messages with reliably controllable performance in the harsh underwater environment, we develop novel Magnetic Induction (MI)-based underwater communication module. The range of underwater MI communication can reach 20 m in lake water but less than 1 m in sea water. We find that the reflection and surface wave can significantly increase the communication range of underwater MI. The original MI coil antenna is highly directional, which cause unreliable network connectivity. We introduce the 3-directional coil antenna, which can cover the whole 3D space no matter how the wireless node rotates. By using the 3D coil antenna, we can accurately estimate the relative locations between two wireless nodes. The MI channel is reliable and not influenced by multipath fading, which guarantees accurate distance estimation. The 3D coil provide the direction estimation. Together with the distance estimation, the relative localization is achieved.