Sonar-based guidance of unmanned underwater vehicles

This paper addresses the problem of the design and coordination of guidance and sonarbased motion estimation algorithms for unmanned underwater vehicles. In the framework of a two-layered hierarchical architecture uncoupling the system's dynamics and kinematics, a couple of guidance laws for approaching a target with the desired orientation and following an environmental feature have been designed with Lyapunov-based techniques. Suitable acoustic-based estimators of the corresponding operational variables have been designed and integrated with the guidance and control system. A finite state machine combined with a suitable interface for event generation allows the coordinated execution of basic guidance and motion estimation tasks to carry out more complex functions. Experimental results of pool trials of a prototype unmanned underwater vehicle executing free-space maneuvering, wall-following tasks and the more complex mission of following the perimeter of the trial pool are reported and discussed.     

Security in transport of radioactive material

Abstract

The basis of safety regulation and practice in the handling (including transport) of radioactive materials has been the premise that any mishaps or accidents occur unintentionally, with a desire among all parties involved to avoid such incidents and to minimise their effects. The strategic importance of nuclear materials for military purposes has made these materials a potential target for unauthorised acquisition, however, and international conventions have been in place for many years to ensure the security of nuclear materials from theft and from interception during transport. Until recently, only nuclear materials were subject to such security measures, but concern over the consequences of incidents involving radioactive sources has led to a review of security measures for non-nuclear radioactive materials. The IAEA has encouraged governments to institute effective systems of control to ensure the security of radioactive materials and has published its 'Code of conduct on the safety and security of radioactive sources' and other guidance material. Three principal stages are recommended for the maintenance of security. The first and most important is the prevention of malevolent acts through the fostering of a security culture, the effective management of material within a regulated legal framework, the appropriate design of sources and the use of secure vehicles and physical means to deter unauthorised access. The second line of defence is the detection of any breach of security, by means of radiation monitoring, accounting checks and reports of unusual occurrences. The third stage, response, includes means to ensure that the effect of a breach of security on public safety is minimised, and to take steps to recover any material that has fallen outside secure control. Specific provisions for security have been added to the UN Model Regulations for the Transport of Dangerous Goods (the Orange Book) and these have been incorporated in the international modal regulations and enacted in the domestic legislation of individual states. The regulations include general provisions applicable to all dangerous goods including radioactive materials and additional provisions for 'high consequence dangerous goods', which include radioactive materials in quantities above 3000 A ₁ (special form radioactive material) or 3000 A ₂, in Type B(U), Type B(M) or Type C packages. Training in security, including the nature of risks and methods to address them is also required. The Department for Transport in the United Kingdom has produced guidance material in support of the regulatory security requirements for transport by rail and road. The rail transport guidance follows the structure of the regulations and the road transport guidance is grouped into three main aspects of security, namely people, procedures and assets. Therefore, the importance of ensuring a reliable and trustworthy workforce and the use of known and trusted contractors is stressed, together with assurance of adequate and verifiable standards of education and training. Procedural matters include the establishment of standards of responsibility, the supervision of contractors, the maintenance of contacts and risk assessment. The control of assets includes surveillance and access control of premises, and the secure storage of vehicles, which should be fitted with appropriate alarms and immobilisers. The guidance material is available from the Department for Transport and may be viewed on its website www.dft.gov.uk/security/dangerousgoods.     

Design of a vision-guided microrobotic colonoscopy system

In this paper presents a novel design of a microrobotic colonoscopy (MRC) system. The proposed microrobotic colonoscope is an autonomous vision-guided device, which is designed to navigate inside a human colon for the purpose of observation, analysis and diagnosis. It is developed to alleviate the shortcomings in the existing manual colonoscopy procedure, which is generally cumbersome and tedious for the colonoscopist and painful to the patients. The MRC system is divided into three areas, i.e. design of the microrobotic device, path planning and guidance, and offboard control system. A novel design of the microrobot is presented which utilizes a pneumatic mechanism to achieve locomotion and steering. A new concept of clamping the colon wall based on passive vacuum devices is suggested. General mathematical analysis governing the differential steering of the robotic tip is also described. The path planning of the microrobot is carried out based on the sensory fusion utilizing the quantitative parameters derived from the captured images and the tactile sensors. An off-board control system to control the directional movements of the microrobot is explained. The proposed colonoscopy system was tested with physical models and animal colons, and the experimental observations are presented.     

Visual control of two aerial micro-robots by insect-based autopilots

In the framework of our research on biologically inspired microrobotics, we have developed two novel Automatic Flight Control Systems (AFCs): OCTAVE ( Optical flow Control sysTem for Aerospace VEhicles) and OSCAR ( Optical Scanning sensor for the Control of Autonomous Robots), both based on insects' visuomotor control systems. OCTAVE confers upon a tethered aerial robot (the OCTAVE robot) the ability to perform terrain following. OSCAR gives a tethered aerial robot (the OSCAR robot) the ability to fixate and track a contrasting target with a high level of accuracy. Both OCTAVE and OSCAR robots are based on optical velocity sensors, the principle of which is based on the results of previous electrophysiological studies on the fly's Elementary Motion Detectors (EMDs) performed at our laboratory. Both processing systems described are light enough to be mounted on-board Micro-Air Vehicles (MAVs) with an avionic payload small enough to be expressed in grams rather than kilograms.     

Guidance of an ultrasound probe by visual servoing

A new visual servoing technique based on two-dimensional (2-D) ultrasound (US) image is proposed in order to control the motion of an US probe held by a medical robot. In opposition to a standard camera which provides a projection of the three-dimensional (3-D) scene to a 2-D image, US information is strictly in the observation plane of the probe and consequently visual servoing techniques have to be adapted. In this paper the coupling between the US probe and a motionless crossed string phantom used for probe calibration is modeled. Then a robotic task is developed which consists of positioning the US image on the intersection point of the crossed string phantom while moving the probe to different orientations. The goal of this task is to optimize the procedure of spatial parameter calibration of 3-D US systems.     

Optimal Guidance for Autonomous Underwater Vehicle Navigation within Undersea Areas of Current Disturbances

Simulated navigations of an autonomous underwater vehicle (AUV) achieved by the minimum time guidance within undersea areas of current disturbances are presented. When an AUV has to transit to a given destination within an area of current disturbance, ingenious guidance enables the minimum time navigation. In this study, a numerical solution procedure for an optimal heading guidance law is developed. As the optimal heading reference, the solution of the optimal guidance law is fed to the heading controller. Simulated optimal navigations are realized on the basis of the dynamics of an AUV 'r2D4'. The r2D4 is a deep-ocean-exploring AUV, developed by the Institute of Industrial Science, University of Tokyo. The developed procedure never fails to derive the optimal heading sequence within a finite computational time, provided that the current velocity in the navigation region is known a priori. As a fail-safe strategy in achieving the optimal navigation, the concept of quasi-optimal navigation is presented. The quasi-optimal navigation is implemented by on-site updates of optimal guidances followed by the heading tracking control.     

Guidance-机器人视觉传感平台

视觉传感器作为智能机器人的关键技术,可以实现机器人定位、导航和目标跟踪。但是,当前市场上缺乏高性能的机器人视觉传感器平台。本文将介绍一个功能强、效率高的视觉传感平台Guidance,其包含一个中央处理器和多个(五个以上)伺服传感单元,内置的基础功能有:视觉定位、避障、景深图像生成。此外,Guidance配套有完整的SDK文档,可供使用者灵活使用并开发相关的项目,譬如自主导航、目标跟踪、定位和地图构建等