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It is challenging that Autonomous Surface Vehicle (ASV)  navigated in the riverine environment since the unknown and unstructured waterway, and the non-uniform riverbanks makes the waterway tracking difficult. This paper presents a catamaran type Autonomous Surface vessel (ASV) for autonomous bathymetry survey and environmental monitoring at riverine areas. The ASV is equipped without rudder, thus it is driven by differential thrust to control the speed and heading. The theoretical 3 DOF model of ASV and differential thrust steering dynamics is discussed. The aim is to perform the visual navigation that track along with the river by keeping in the center of river. Meanwhile, the speed is required to vary with the width of river to avoid collision. In order to perform the control aims, a balance control scheme is designed. The results indicate that the proposed control scheme is successful for the navigation task.

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This paper presents a modified artificial potential field (APF) based method for an Autonomous Surface Vessel (ASV) obstacles avoidance in a dynamic riverine environment. The APF method is combined with a balance control scheme to achieve river tracking and obstacles avoidance simultaneously. The APF method is further modified modification to comply with marine collision avoidance regulations (COLREGs). The overtaking and head-on scenarios are simulated in MATLAB platform. The simulation results are compared with other APF methods to prove that the proposed method is efficient for the ASV riverine navigation.

In order to improve the reliability of SpaceWire Bus, this paper makes a study of SpaceWire redundancy. In a spacecraft where SpaceWire is used, Redundancy is an important fault-tolerant technology to improve the reliability of the system. However, the regulation of redundancy does not be involved in the current standard of SpaceWire, so, it is necessary to study redundancy technology of SpaceWire. In this paper, without changing SpaceWire bus protocol, SpaceWire bus node with redundant functions is designed and redundant switching function is achieved on the node boards, routers and backbone links. IP logic of SpaceWire node is implemented in the FPGA. The scheme presents an Auto-Protection-Switch (APS) module which makes two independent SpaceWire nodes linked as mutual backup to achieve standby redundant switched function of SpaceWire bus. Redundancy switching process is as follows: APS continuously detects the working state of two mutual backup SpaceWire nodes in one board. When the Loss of Signal for Node A (LOS-A) is detected, APS uses Remote Defect Indicator forNode B (RDI-B) to send switching request code to the remote end through the altemate link. After receiving the switchover request data code, spare receiver module in the remote end generates switching signal to APS module at the same board and APS module immediately switches to the standby SpaceWire bus. At the same time, the confirming data is send to the local standby node. Then, local APS switches to the standby SpaceWire bus. Test results show that the switch time is 33us under the conditions of 200MHz transmission rate.