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.     

An omni-directional mobile millimeter-sized microrobot with 3-mm electromagnetic micromotors for a micro-factory

This paper presents an omni-directional mobile microrobot for micro-assembly in a micro-factory. A novel structure is designed for omni-directional movement with three normal wheels. The millimeter-sized microrobot is actuated by four electromagnetic micromotors whose size is 3.1 mm × 3.1 mm × 1.4 mm. Three of the micromotors are for translation and the other one is for steering. The micromotor rotors are designed as the wheels to reduce the microrobot volume. A piezoelectric micro-gripper is fabricated for grasping micro-parts. The corresponding kinematics matrix is analyzed to prove the omni-directional mobility. A control system composed of two CCD cameras, a host computer and circuit board is designed. The macro camera is for a global view and the micro camera is for local supervision. Unique location methods are proposed for different scenarios. A microstep control approach for the micromotors is presented to satisfy the requirement of high positioning accuracy. The experiment demonstrates the mobility of the microrobot and the validity of the control system.     

Design and Optimization of an Omnidirectional Permanent-Magnetic Wheeled Wall-Climbing Microrobot with MEMS-Based Electromagnetic Micromotors

The paper presents a compact omnidirectional permanent-magnetic wheeled wall-climbing microrobot. A millimeter-sized axial flux electromagnetic micromotor based on MEMS technology has been specially fabricated for the microrobot and its size is 6.8 mm × 7.8 mm × 3.9 mm. A novel permanent-magnetic wheel is designed, which is directly integrated with the stators and rotor of the electromagnetic micromotor. The omnidirectional wall-climbing mechanism is realized by a set of steering gears and three standard permanent-magnetic wheels. By static and dynamic force analysis of the microrobot, the required magnetic force and the required torques for its translational and steering movements are derived. To reduce the unnecessary torque consumption of the microrobot, its structural parameters are optimized in combination with its design constraints by ANSOFT and Pro/Engineer simulation. A prototype of the proposed microrobot with the maximum designed load capacity of 3 g is developed, whose size is 26 mm in diameter and 16.4 mm in height. Experimental and simulation results demonstrate the feasibility of these concepts.     

Genetic algorithms (GAs) to evolve multiple-agent cooperative systems

In this paper, a microrobot soccer-playing game, such as that of MIROSOT (Microrobot World Cup Soccer Tournament), is adopted as a standard test bed for research on multiple-agent cooperative systems. It is considerably complex and requires expertise in several difficult research topics, such as mobile microrobot design, motor control, sensor technology, intelligent strategy planning, etc., to build up a complete system to play the game. In addition, because it is an antagonistic game, it appears ideal to test whether one method is better than other. To date there have been two different kinds of architecture for building such system. One is called vision-based or centralized architecture, and the other is known as robot-based or decentralized architecture. The main difference between them lies in whether there exists a host computer system which responds to data processing and strategy planning, and a global vision system which can view the whole playground and transfer the environment information to the host computer in real time. We believe that the decentralized approach is more advanced, but in the preliminary step of our study, we used the centralized approach because it can lighten any overload of the microrobot design. In this paper, a simplified layer model of the multiple-agent cooperative system is first proposed. Based on such a model, a system for a microrobot soccer-playing game is organized. At the same time a simple genetic algorithm (SGA) is used for the autonomous evolution of cooperative behavior among microrobots. Finally, a computer simulation system is introduced and some simulated results are explained. This work was presented, in part, at the Third International Symposium on Artificial Life and Robotics, Oita, Japan, January 19–21, 1998.     

Automatic pick-and-place using a magnetically navigated microrobot and a motorized micromanipulator

This paper demonstrates the automatic pick-and-place of a small object in 2D using a magnetically navigated microrobot (MNM) and a motorized micromanipulator (MM). A master/slave control mechanism is used in the manipulation process. The MM is the master manipulator. The MNM is the slave manipulator. To avoid damaging the object by large holding force and to maintain successful holding, a position-based impedance control algorithm is implemented to the slave side. The feedback force to the impedance controller is obtained from an off-board force determination mechanism which overcomes the disadvantages of installing an on-board force sensor on the MNM. The performance of the proposed manipulation system was examined experimentally by transporting a hard-shell object to its desired destinations with predefined holding force. To the authors knowledge, this is the first work reported using a magnetically navigated microrobot to complete manipulation tasks with a screw type manipulator. The proposed system has potential utility in microinjection if the MNM was scaled down to proper size.

     

Motion control of a magnetically levitated microrobot using magnetic flux measurement

Recent advancements in micro/nano domain technologies have led to a renewed interest in ultra-high resolution magnetic-based actuation mechanisms. This paper deals with the development of a novel research-made magnetic microrobotic station (MMS) with promising potential in biological/biomedical applications. The MMS consists of two separate basic components: a magnetic drive unit and a microrobot. The magnetic drive unit produces and regulates the magnetic field for non-contact propelling of the microrobot in an enclosed environment. Our previous research findings have reported that the MMS should be equipped with high accuracy laser sensors for the position determination of the microrobot in the workspace. However, the laser positioning techniques can be used only in highly transparent environments. This paper seeks to address microrobot position estimation in non-transparent environments. A novel technique based on real-time magnetic flux measurement has been proposed for position estimation of the microrobot in the case of the laser beam blockage. A combination of Hall-effect sensors is employed in the structure of the magnetic drive unit to find the microrobot’s position using the produced magnetic flux. The most effective installation position for the Hall-effect sensors has been determined based on the accuracy sensitivity of experimental measurements. We derived a mathematical function which relates Hall-effect sensors’ voltage output and the position of the microrobot. The motion control capability of the Hall-effect-based positioning method is experimentally verified in the horizontal axis, and it was demonstrated that the microrobot can be operated in most of the workspace range with an accuracy of 0.3?mm as the root-mean-square of the position error.     

Microassembly path planning using reinforcement learning for improving positioning accuracy of a 1 cm<Superscript>3</Superscript> omni-directional mobile microrobot

This paper introduces the path planning of a 1 cm³ mobile microrobot that is designed for microassembly in a microfactory. Since the conventional path planning method can not achieve high microassembly positioning accuracy, a supervised learning assisted reinforcement learning (SL-RL) method has been developed. In this mixed learning method, the reinforcement learning (RL) is used to search a movement path in the normal learning area. But when the microrobot moves into the buffer area, the supervised learning (SL) is employed to prevent it from moving out of the boundary. The SL-RL uses a gradient descent algorithm based on uniform grid tile coding under SARSA(λ) to handle the large learning state space. In addition to the uniform grid tile model, two irregular tile models called an uneven grid tile model and a cobweb tile model are designed to partition the microrobot state space. The main conclusions demonstrated by simulations are as follows: First, the SL-RL method achieves higher positioning accuracy than the conventional path planning method; second, the SL-RL method achieves higher positioning accuracy and learning efficiency than the single RL method; and third, the irregular tile models show higher learning efficiency than the uniform tile model. The cobweb tile model performs especially well.     

Enhanced locomotive and drilling microrobot using precessional and gradient magnetic field

We propose a new electromagnetic actuation (EMA) system for an intravascular microrobot with steering, locomotion and drilling functions. The EMA system consists of 3 pairs of Helmholtz coil and 1 pair of Maxwell coil. Generally, Helmholtz coils can align a microrobot in a desired direction by generating a uniform magnetic flux. If the uniform magnetic field generated by Helmholtz coils can be rotated, a microrobot with Helmholtz coils can also be rotated. On the other hand, a Maxwell coil, which generates a constant gradient magnetic flux, can supply the propulsion force for the microrobot. A microrobot actuated by the proposed EMA system has a spiral shaped body containing two magnets with different magnetization directions. With the proposed EMA system, the microrobot can move to the target region and perform drilling there by the precessional magnetic field of the Helmholtz coil pairs. The propulsion force for the microrobot is produced by the gradient magnetic field generated by the Maxwell coil pair. The moving velocity and the drilling performance of the microrobot can be increased by the propulsion force of the Maxwell coil pair. Through various tests, the feasibility and enhancement of the microrobot actuated by the proposed EMA system were verified.     

Human-assisted virtual reality for a magnetic-haptic micromanipulation platform

This paper deals with the development of a virtual reality interface (VRI) for a magnetic-haptic micromanipulation platform (MHMP) (Mehrtash et?al. in IEEE/ASME Trans Mechatron 16(3):459–469, 2011). Our previously developed MHMP has shown a great deal of promise in non-contact micromanipulations. This micromanipulation platform concerns the integration of magnetic actuation technology and a bilateral macro–micro teleoperation. The MHMP has two separate stations: one magnetic microrobotic station and one haptic. The magnetic microrobotic station manipulates micro-sized objects based on the commands from the haptic station. The haptic station uses bilateral communication with the magnetic microrobotic station to allow a human operator the feeling of a micro-domain environment. In this paper, we report a VRI that enables human operators to improve their skills in using the MHMP, before carrying out an actual dexterous task. The VRI is made up of three main components: a haptic station, a simulation engine, and a display unit. The haptic station provides the operator with the force/torque information from virtual or remote environments, and is also used to recognize the operator’s hand motion command. Dynamical computation and control system modeling have been carried out on the simulation engine. Based on the real-time computation, this engine, as the heart of the system, provides force applied to the operator’s hand and the microrobot’s position for the haptic station and the display unit, respectively. The display unit employs 3D computer graphics to demonstrate the micromanipulation tasks and environments. The VRI is also developed in such a way that it can be separately used in parallel with the MHMP for the 3D visualization of a real task by providing multiple virtual viewports. This paper introduces the configuration of the proposed VRI, and reports the result of a preliminary experiment using micromanipulation investigation for validation.     

电磁微马达驱动全方位永磁轮式爬壁微机器人

介绍了一种全方位微型轮式爬壁机器人.将轴向磁通电磁微马达与永磁轮集成在一起,实现驱动吸附一体化设计.采用一套转向齿轮和三个永磁轮,设计了全方位的爬壁机构.通过动力学分析,导出微机器人爬壁所需的力矩和磁力,并结合永磁轮自身的设计约束,采用ANSOFT和Pro/Engineer仿真对其尺寸进行了优化,从而在相司负载的情况下...     

Robust MIMO disturbance observer analysis and design with application to active car steering

A multi‐input–multi‐output extension of the well‐known two control degrees‐of‐freedom disturbance observer architecture that decouples the problem into single‐input–single‐output disturbance observer loops is presented in this paper. Robust design based on mapping D‐stability and the frequency domain specifications of weighted sensitivity minimization and phase margin bound to a chosen controller parameter space is presented as a part of the proposed design approach. The effect of the choice of disturbance observer Q filter on performance is explained with a numerical example. This is followed by the use of structured singular values in the robustness analysis of disturbance observer controlled systems subject to structured, real parametric and mixed uncertainty in the plant. A design and simulation study based on a four wheel active car steering control example is used to illustrate the methods presented in the paper. Copyright © 2009 John Wiley & Sons, Ltd.     

基于微分平坦与MPC的智能车换道控制算法

为了提高智能车换道的安全性,提出了一种基于微分平坦理论与模型预测控制(MPC)算法相结合的智能车换道轨迹规划与跟踪算法。该算法利用约束求解得到基于sigmoid函数的优化路径;将其与多项式参数化时间函数作为平坦输出,利用微分平坦理论构造一个非线性性能指标函数并对其进行优化求解完成车速规划;从而实现对智能车辆路径-速度分解式的轨迹规划。利用动力学模型预测控制算法线上控制的优点,对智能车的车轮转向进行实时控制,使得车辆按照规划好的轨迹行驶完成换道。通过CarSim与MATLAB/Simulink的联合仿真,将提出的轨迹规划算法应用于车辆系统仿真软件中进行验证,结果表明该算法能够实现对智能车进行轨迹规划和跟踪控制,使其安全高效地换至目标车道。     

Nested PID steering control for lane keeping in autonomous vehicles

In this paper a nested PID steering control in vision based autonomous vehicles is designed and experimentally tested to perform path following in the case of roads with an uncertain curvature. The control input is the steering wheel angle: it is designed on the basis of the yaw rate, measured by a gyroscope, and the lateral offset, measured by the vision system as the distance between the road centerline and a virtual point at a fixed distance from the vehicle. No lateral acceleration and no lateral speed measurements are required. A PI active front steering control based on the yaw rate tracking error is used to improve the vehicle steering dynamics. The yaw rate reference is computed by an external control loop which is designed using a PID control with a double integral action based on the lateral offset to reject the disturbances on the curvature which increase linearly with respect to time. The proposed control scheme leads to a nested architecture with two independent control loops that allows us to design standard PID controls in a multivariable context (two outputs, one input). The robustness of the controlled system is theoretically investigated with respect to speed variations and uncertain vehicle physical parameters. Several simulations are carried out on a standard big sedan CarSim vehicle model to explore the robustness with respect to unmodelled effects. The simulations show reduced lateral offset and new stable μ-split braking maneuvres in comparison with the model predictive steering controller implemented by CarSim. Finally the proposed control law is successfully tested by experiments using a Peugeot 307 prototype vehicle on the test track in Satory, 20 km west of Paris.     

虚拟内窥镜系统研究进展

简述了虚拟内窥镜系统的特点和发展经历,详细论述了数据采集、图像的组织分割、三维重建、路径规划、实时绘制等处理过程以及基于面绘制和体绘制的主要技术组成,介绍了当前的现状,同时指出了在组织分割、路径规划、实时处理、场景绘制、硬件平台等方面存在的主要问题。     

基于平行泊车路径规划的智能泊车系统设计

针对智能泊车系统对泊车准确度及计费实时性要求,提出一种基于距离和避障信息融合的自动泊车路径规划方法和泊车计费方法,解决当前泊车与计费不能有效融合,不利于进行智能管控的现实问题。系统采用STM32单片机作为系统主控芯片,电机驱动模块RZ7889D驱动直流电机,转向舵机采用MG996,超声波测距传感器HC-SR04用于测量车身与障碍物物理距离并结合LM393实现红外避障,实现智能泊车。系统采用LabVIEW设计智能泊车系统上位机面板,实时显示泊车车位、数量、时长和费用,并具有历史数据查询和车辆数据波形显示功能。经仿真测试和系统微缩物理模型测试,该系统能够实现平行泊车路径规划,可实现平稳、顺滑的良好泊车,平均泊车时长为41s,能够根据停车时长进行计费,满足简单、可靠且准确的智能泊车计费系统设计要求。     

视觉AGV的差速转向控制器设计

简要地介绍了基于机器视觉导向的AGV两轮差速转向的原理和组成，并对计算机控制系统设计，图像信息识别等AGV控制问题进行了阐述，提出了一种采用模糊控制方法对AGV两轮差速转向进行控制。仿真和实验结果均表明，采用模糊控制方法对两轮差速转向进行控制，样车运行过程稳定，路径跟踪可靠，控制性能良好。     

毫米级全方位移动微型装配机器人设计、运动学分析与控制

介绍了一种用于微型工厂的毫米级移动微装配机器人,其具有独特的全方位运动结构．微机器人由4个直径3 mm的电磁微马达驱动,并装备有一对微型夹钳．通过分析运动学矩阵的秩,证明了微机器人的全方位特性,并建立了微夹钳的运动学方程．设计了基于计算机视觉的微机器人控制系统,给出了微机器人定位和驱动方法．实验证明了微机器人的负载能力、机动性以及控制系统的有效性．     

基于双层模糊逻辑的多机器人路径规划与避碰

针对无通信情况下的多机器人系统在未知动态环境下的路径规划问题,设计了基于双层模糊逻辑的多机器人路径规划与动态避碰系统。方向模糊控制器充分考虑了障碍物的距离信息和目标的角度信息,转化为机器人与障碍物的碰撞可能性,从而输出转向角度实现机器人的动态避障;速度模糊控制器将障碍物的距离信息作为输入,将速度因子作为输出,提高了多机器人路径规划与动态避碰系统的效率和鲁棒性。在Pioneer3-DX机器人实体上验证了该系统的可行性。     

Continuous trajectory planning of mobile sensors for informative forecasting

This paper addresses the planning of continuous paths for mobile sensors to reduce the uncertainty in some quantities of interest in the future. The mutual information between the measurement along the continuous path and the future verification variables defines the information reward. Two expressions for computing this mutual information are presented: the filter form extended from the state of the art and the smoother form inspired by the conditional independence structure. The key properties of the approach using the filter and smoother strategies are presented and compared. The smoother form is shown to be preferable because it provides better computational efficiency, facilitates easy integration with existing path synthesis tools, and, most importantly, enables correct quantification of the rate of information accumulation. A spatial interpolation technique is used to relate the motion of the sensor to the evolution of the measurement matrix, which leads to the formulation of the optimal path planning problem. A gradient-ascent steering law based on the concept of information potential field is also presented as a computationally efficient suboptimal strategy. A simplified weather forecasting example is used to compare several planning methodologies and to illustrate the potential performance benefits of using the proposed planning approach.     

考虑输入饱和的农用拖拉机路径跟踪有限时间控制

针对农用拖拉机的路径跟踪控制问题,提出基于有限时间和饱和技术的路径跟踪控制策略.首先,建立农机路径跟踪运动学模型,并通过有限时间控制技术,构造有限时间路径跟踪控制方法;其次,考虑到农用拖拉机的转向系统物理限制,将饱和技术与有限时间控制结合,给出复合的路径跟踪控制方法,通过严格的理论分析验证闭环系统在该控制器下的有限时间稳定性;最后,通过仿真结果表明,所设计的制导方法可以保证农用拖拉机快速、稳定地完成路径跟踪目标.