Disturbance rejection for space‐based manipulators

Most industrial manipulators operate from a fixed base. Hence, there are no disturbances from the environment to alter the position of the end‐effector. On the other hand, manipulators that are mounted on mobile platforms are subject to disturbances emerging from unwanted motion at the base. Similarly, manipulators that perform delicate operations in space while on board in‐orbit spacecraft experience disturbances. This article describes the design and implementation of a disturbance rejection controller for a 6 degree‐of‐freedom (DOF) programable universal manipulator for assembly (PUMA) manipulator mounted on a 3‐DOF platform. A control algorithm is designed to track the desired position and attitude of the end‐effector in inertial space, subject to unknown disturbances in the platform axes. Experimental results are presented for step, sinusoidal, and random disturbances in the platform rotational axis and in the neighborhood of kinematic singularities. ©1999 John Wiley & Sons, Inc.     

Fuzzy control-based real-time robust balance for a humanoid robot

This paper studies and implements a real-time robust balance control for a humanoid robot under three environment disturbances which are an external thrust, an inclinable platform, and a see-saw. More precisely to say, the robot with robust control can resist an external thrust, stand on a two-axis inclinable platform, or walk on a see-saw successfully. The main feature of the robot is that it has a waist joint which has three degrees of freedom. With the aids of the proposed fuzzy controllers, the robot can change the posture of the body nimbly by adjusting the waist joint and two ankle joints to strengthen the stabilization capacity. The sensory system of the robot includes eight force sensors and one inertial measurement unit sensor in order to measure the center of pressure and the slant angle of the robot’s body. According to the measured data from the sensors and by imitating human reflex actions, the proposed fuzzy controllers perform real-time balance control for the robot under three environment disturbances. According to the experiment results, the stability of the robot is increased at least 32.2 and 61.7% under the first two environment disturbances, respectively. In addition, the robot walking on a see-saw has a success rate of about 95%.     

Precision gyro-stabilized platform on the base of gas-static supported gyros

The principles of construction and design features of inertial devices with gas-static support developed for using on booster rockets and space vehicles of different types are set up for the first time. The gyro-stabilized platform of space application created on their base and successfully tested at injection of the heavy telecommunication satellite “Horizon” into geostationary orbit in June 2000, is described. The capability of extension of the field of application of the created means of motion control is underlined.     

惯性仪器通用测试与故障诊断系统设计

针对在分析惯性仪器测试需求和基本功能的基础上,提出一种通用测试的理念和方法。针对惯性平台测试与故障诊断系统的特点和设计要求,给出了基于VXI总线的惯性平台自动测试与故障诊断系统的开发设计方法,重点探讨了VXI总线测试硬件与软件的组成和实现方法。所提出的系统成功应用于某些型号惯性仪器的性能测试过程,实现了测试过程的优化控制和优化运行,取得了明显的应用成效。     

Robust adaptive control for mobile manipulators

This paper addresses the trajectory tracking control of a nonholonomic wheeled mobile manipulator with parameter uncertainties and disturbances. The proposed algorithm adopts a robust adaptive control strategy where parametric uncertainties are compensated by adaptive update techniques and the disturbances are suppressed. A kinematic controller is first designed to make the robot follow a desired end-effector and platform trajectories in task space coordinates simultaneously. Then, an adaptive control scheme is proposed, which ensures that the trajectories are accurately tracked even in the presence of external disturbances and uncertainties. The system stability and the convergence of tracking errors to zero are rigorously proven using Lyapunov theory. Simulations results are given to illustrate the effectiveness of the proposed robust adaptive control law in comparison with a sliding mode controller.     

非伪控制解决惯性稳定平台的非线性时变干扰

非伪控制是一种基于在线数据的驱动控制方式.本文通过进化策略实现候选控制器的多样性操作,结合滞后算法切换控制器,从而实现系统自适应的PID稳定控制.在惯性稳定平台中,由于非线性时变干扰的存在令被控对象不能提供精确的控制模型,今将非伪控制算法用于惯性稳定平台中,能使惯性稳定平台准确地稳定框架,其方位轴稳定误差小于3.4mrad,俯仰轴稳定误差小于4.36mrad.     

Skeleton pruning as trade-off between skeleton simplicity and reconstruction error

The position and orientation of moving platform mainly depends on global positioning system and inertial navigation system in the field of low-altitude surveying, mapping and remote sensing and land-based mobile mapping system. However, GPS signal is unavailable in the application of deep space exploration and indoor robot control. In such circumstances, image-based methods are very important for self-position and orientation of moving platform. Therefore, this paper firstly introduces state of the art development of the image-based self-position and orientation method (ISPOM) for moving platform from the following aspects: 1) A comparison among major image-based methods (i.e., visual odometry, structure from motion, simultaneous localization and mapping) for position and orientation; 2) types of moving platform; 3) integration schemes of image sensor with other sensors; 4) calculation methodology and quantity of image sensors. Then, the paper proposes a new scheme of ISPOM for mobile robot — depending merely on image sensors. It takes the advantages of both monocular vision and stereo vision, and estimates the relative position and orientation of moving platform with high precision and high frequency. In a word, ISPOM will gradually speed from research to application, as well as play a vital role in deep space exploration and indoor robot control.     

Development and Flight Testing of a Turbulence Mitigation System for Micro Air Vehicles

There are significant challenges associated with the flight control of fixed‐wing micro air vehicles (MAVs) operating in complex environments. The scale of MAVs makes them particularly sensitive to atmospheric disturbances thus limiting their ability to sustain controlled flight. Bio‐inspired, phase‐advanced sensors have been identified as promising sensory solutions for complementing current inertial‐only attitude sensors. This paper describes the development and flight testing of a bio‐inspired, phase‐advanced sensor and associated control system that mitigates the impact of turbulence on MAVs. Multihole pressure probes, inspired by the sensory function of bird feathers, are used to measure the flow pitch angle and velocity magnitude ahead of the MAV's wing. The sensors provide information on the disturbing phenomena before it causes an inertial response in the aircraft. The sensor output is input to a simple feed‐forward control architecture, which enables the MAV to generate a mitigating response to the turbulence. The results from wind‐tunnel and outdoor testing in high levels of turbulence are presented. The disturbance rejection performance of the phase‐advanced sensory system is compared against that of a conventional inertial‐based control system. The developed sensory system shows significant improvement in terms of disturbance rejection performance compared to that of standard inertial‐only control system. It is concluded that a phase‐advanced sensory systems can complement conventional inertial‐based sensors to improve the attitude‐tracking performance of MAVs.     

Digital stabilization of motion of precision controlled base platforms with inertial sensitive elements. I. Application of float angular velocity sensor

The problem of synthesis of a complex digital controller for a control system of a new generation precision calibration testbed is considered; the specific feature is the application of inertial float angular velocity sensor as the sensitive element of the system. The problem is connected with finding two algorithms of digital control realized in one processor; one of these algorithms determines the controller of the angular velocity sensor and the second one, the controller of the main loop (stabilization loop) providing stabilization of the given motion of the controlled base platform. Solution of this problem underlying the method of synthesis of such systems is given; obtained solution is analyzed in the time and frequency domains.     

Indirect disturbance compensation control of a planar parallel (2-PRP and 1-PPR) robotic manipulator

This study addresses the dynamic modelling and indirect disturbance compensation control of planar parallel robotic motion platform with three degrees of freedom (3-DOF) in the presence of parameter uncertainties and external disturbances. The proposed planar parallel motion platform is a singularity free manipulator and has three manipulator legs located on the same plane linked with a moving platform. Of the three aforementioned manipulator legs, two legs have a prismatic–revolute–prismatic (PRP) joint configuration each with only one prismatic joint deliberated to be active, and the other leg consists of prismatic–revolute–prismatic (PPR) joint configuration with one active prismatic joint. The closed form kinematic solution (both forward and reverse kinematics) for the platform has been obtained in completion. In addition, the dynamic model for the platform has been communicated using the energy based Euler–Lagrangian formulation method. The proposed controller is based on a computer torque control with disturbance compensation integrated with it. Disturbance vectors comprising disturbances due to parameter variations, payload variations, frictional effects and other additional effects have been estimated using an extended Kalman filter (EKF). The EKF proposed for this specific platform uses only position and orientation measurements for estimation and noise mitigation. Simulations with a characteristic trajectory are presented and the results have been paralleled with traditional controllers such as the proportional integral derivative (PID) controller and computed torque controller (CTC). The results demonstrate satisfactory tracking performance for the proposed controller in the presence of parameter uncertainties and external disturbances.     

基于单目视觉的水下机器人悬停定位技术与实现

以7000m载人潜水器的水下悬停为应用背景,以单目CCD摄像机为传感器,提出了基于模型的单目视觉定位和基于特征的视觉伺服两种水下机器人视觉悬停技术方案,分别适用于已知模型的观察目标和未知模型的观察目标两种情况．以自行研制的水下机器人控制系统实验平台为实验载体,利用前视摄像机和水下人工目标,建立了水下演示实验验证系统,并在室内实验水池中,分别实现了两种悬停方法的水下演示实验．演示实验表明：在两种视觉悬停方法的闭环控制下,水下机器人能够抵抗恒定水流干扰和人工位置扰动,很好地实现水下悬停作业．     

Inertia‐free attitude stabilization for flexible spacecraft with active vibration suppression

This paper addresses the inertia‐free attitude control problem for flexible spacecraft in the presence of inertia uncertainties, external disturbances, actuator faults, measurement errors, and input magnitude and rate constraints (MRCs). By analyzing the influence of external disturbances, faulty signals, and actual inertial matrix, a lumped disturbance is reconstructed to facilitate the controller design. Then, a new intermediate observer is developed to estimate the attitude and modal information and the lumped disturbance. The Lyapunov stability analysis shows that the developed controller can achieve the objectives of the attitude stabilization and vibration suppression with input MRCs. Finally, numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed control method.     

基于DSP的RS码快速编译码算法的实现

平台光纤传输模块通过光纤完成惯导平台系统中的数据传输,其中一些关键数据如平台控制参数等直接影响到平台系统的状态,为了确保平台系统可以安全可靠地工作,必须对控制参数进行纠错,保证其准确性.由于RS码具有强大的纠突发错误和随机错误的能力,被广泛应用于各种差错控制场合.文章设计了基于DSP的RS（15,11）码的快速实现,完成对惯导平台系统中光纤传输的平台控制参数等关键数据的纠错.     

基于LabVIEW的惯性平台温度检测控制系统设计

设计了一个基于PC工控机的惯性平台温度检测控制系统,并介绍了系统的硬件原理框图和软件流程图。系统采用脉宽调制电路和测温电桥实现了对惯性平台台体精密的温度控制,并使用虚拟仪器开发软件LabVIEW设计了一个界面友好的虚拟面板。实验证明该系统能很好的实现对弹上惯性平台的温度检测和控制。     

Cooperative Multi-Agent Control for Autonomous Ship Towing Under Environmental Disturbances

Among the promising application of autonomous surface vessels (ASVs) is the utilization of multiple autonomous tugs for manipulating a floating object such as an oil platform, a broken ship, or a ship in port areas. Considering the real conditions and operations of maritime practice, this paper proposes a multi-agent control algorithm to manipulate a ship to a desired position with a desired heading and velocity under the environmental disturbances. The control architecture consists of a supervisory controller in the higher layer and tug controllers in the lower layer. The supervisory controller allocates the towing forces and angles between the tugs and the ship by minimizing the error in the position and velocity of the ship. The weight coefficients in the cost function are designed to be adaptive to guarantee that the towing system functions well under environmental disturbances, and to enhance the efficiency of the towing system. The tug controller provides the forces to tow the ship and tracks the reference trajectory that is computed online based on the towing angles calculated by the supervisory controller. Simulation results show that the proposed algorithm can make the two autonomous tugs cooperatively tow a ship to a desired position with a desired heading and velocity under the (even harsh) environmental disturbances.      

高精度自寻北惯性平台的误差建模研究

平台一体化后已不能安装传统的光学棱镜,传统的平台误差建模方法急需改进。基于此现状,对自寻北惯性平台进行了研究。利用加速度表本身的寻北功能来定义坐标基准,通过3个误差角建立了自寻北惯性平台的基准坐标系,在此基础上推导了工程应用中较为实用的惯性仪表误差模型并进行了试验方案设计。该方案可实现无转台、任意初始方位角下自主标定陀螺仪和石英加速度计包括安装误差在内的33项主要误差系数。     

Particle/cell separation on microfluidic platforms based on centrifugation effect: a review

Particle/cell separation in heterogeneous mixtures including biological samples is a standard sample preparation step for various biomedical assays. A wide range of microfluidic-based methods have been proposed for particle/cell sorting and isolation. Two promising microfluidic platforms for this task are microfluidic chips and centrifugal microfluidic disks. In this review, we focus on particle/cell isolation methods that are based on liquid centrifugation phenomena. Under this category, we reviewed particle/cell sorting methods which have been performed on centrifugal microfluidic platforms, and inertial microfluidic platforms that contain spiral channels and multi-orifice channels. All of these platforms implement a form of centrifuge-based particle/cell separation: either physical platform centrifugation in the case of centrifugal microfluidic platforms or liquid centrifugation due to Dean drag force in the case of inertial microfluidics. Centrifugal microfluidic platforms are suitable for cases where the preparation step of a raw sample is required to be integrated on the same platform. However, the limited available space on the platform is the main disadvantage, especially when high sample volume is required. On the other hand, inertial microfluidics (spiral and multi-orifice) showed various advantages such as simple design and fabrication, the ability to process large sample volume, high throughput, high recovery rate, and the ability for multiplexing for improved performance. However, the utilization of syringe pump can reduce the portability options of the platform. In conclusion, the requirement of each application should be carefully considered prior to platform selection.     

Distributed Nash Equilibrium Seeking for General Networked Games With Bounded Disturbances

This paper is concerned with anti-disturbance Nash equilibrium seeking for games with partial information. First, reduced-order disturbance observer-based algorithms are proposed to achieve Nash equilibrium seeking for games with first-order and second-order players, respectively. In the developed algorithms, the observed disturbance values are included in control signals to eliminate the influence of disturbances, based on which a gradient-like optimization method is implemented for each player. Second, a signum function based distributed algorithm is proposed to attenuate disturbances for games with second-order integrator-type players. To be more specific, a signum function is involved in the proposed seeking strategy to dominate disturbances, based on which the feedback of the velocity-like states and the gradients of the functions associated with players achieves stabilization of system dynamics and optimization of players’ objective functions. Through Lyapunov stability analysis, it is proven that the players’ actions can approach a small region around the Nash equilibrium by utilizing disturbance observer-based strategies with appropriate control gains. Moreover, exponential (asymptotic) convergence can be achieved when the signum function based control strategy (with an adaptive control gain) is employed. The performance of the proposed algorithms is tested by utilizing an integrated simulation platform of virtual robot experimentation platform (V-REP) and MATLAB.      

大型空间飞行器的高阶滑模姿态控制律设计

针对大型空间飞行器的大角度姿态控制问题,考虑航天器惯量矩阵中的不确定性和外部扰动力矩,应用高阶滑模控制方法设计了姿态跟踪控制律.采用的二阶滑模控制方法改善了系统针对不确定性及外部扰动的鲁棒性,并减弱了振颤现象.针对所设计的控制器进行了仿真验证,并与一阶滑模控制进行了对比,仿真结果表明了所提出方法的有效性.     

车载惯性平台随动系统的自抗扰控制

针对车载惯性随动平台的扰动特性,提出了随动伺服回路的自抗扰控制算法。该方法不需要精确的系统数学模型,具有强鲁棒性、快速性、高精度、方法简单等特点。仿真和实验结果表明,该方法调转时间短,抗干扰能力强,是一种应用在实际平台系统中的理想的控制器。