某新型远程自主水下航行器建模研究

根据某新型远程自主水下航行器的组成和特点,通过对其进行动力学和运动学分析,基于经典的动量和动量矩定理,建立了该新型自主水下航行器的数学模型。该模型不仅可以用来模拟航行器的正常巡航状态,而且可以用来模拟航行器的悬停状态,可用于航行器的操纵性分析及控制系统的设计与仿真。     

新型随控布局水下航行器近水面运动非线性模型研究

采用随控布局的新型水下航行器配备有多个不同方向的推进器,实现了直接升力控制和直接侧向力控制,具有巡航和悬停2种运动模式。文中详细分析并建立了不同运动模式下的流体动力模型以及环境因素的扰动作用模型,建立了新型水下航行器的6自由度非线性低频运动模型以及波浪作用下的高频运动模型,并进行了计算机仿真。仿真结果表明,该模型不仅可以模拟航行器的巡航以及悬停运动状态,还可以描述航行器的低频运动和高频运动状态,为航行器近海面运动的控制系统设计与仿真提供了参考。     

四旋翼飞行器悬停算法设计与实现

以自制四旋翼飞行器为研究对象,对四旋翼飞行器悬停算法进行详细研究。控制中心通过传感器MPU6050获取飞行数据,通过获取的数据计算得到飞行姿态,然后结合气压传感器和摄像头相结合进行悬停算法的设计。程序算法主要包括四元数、PID、卡尔曼滤波和视觉定位等算法,计算得出相应的数据,最后通过控制电子调节系统驱动无刷电机完成其悬停与控制。     

A Bio-Inspired Global Finite Time Tracking Control of Four-Rotor Test Bench System

A bio-inspired global finite time control using global fast-terminal sliding mode controller and radial basis function network is presented in this article, to address the attitude tracking control problem of the three degree-of-freedom four-rotor hover system. The proposed controller provides convergence of system states in a pre-determined finite time and estimates the unmodeled dynamics of the four-rotor system. Dynamic model of the four-rotor system is derived with Newton’s force equations. The unknown dynamics of four-rotor systems are estimated using Radial basis function. The bio-inspired global fast terminal sliding mode controller is proposed to provide chattering free finite time error convergence and to provide optimal tracking of the attitude angles while being subjected to unknown dynamics. The global stability proof of the designed controller is provided on the basis of Lyapunov stability theorem. The proposed controller is validated by (i) conducting an experiment through implementing it on the laboratory-based hover system, and (ii) through simulations. Performance of the proposed control scheme is also compared with classical and intelligent controllers. The performance comparison exhibits that the designed controller has quick transient response and improved chattering free steady state performance. The proposed bio-inspired global fast terminal sliding mode controller offers improved estimation and better tracking performance than the traditional controllers. In addition, the proposed controller is computationally cost effective and can be implanted on multirotor unmanned air vehicles with limited computational processing capabilities.     

三倾转旋翼无人机直升机模式建模与控制研究

针对一种新型三旋翼构型的倾转旋翼无人机的直升机模式控制问题进行研究,采用牛顿欧拉法对这种新型三旋翼构型的倾转旋翼无人机直升机模式进行了详细的动力学建模分析,建立了该无人机悬停模式6自由度非线性模型;在对该模型进行线性化的基础上,设计了这种三倾转旋翼无人机直升机模式下的高度、俯仰通道、滚转通道以及偏航通道的PID控制器,并在Matlab/Simlink环境下建立其仿真模型,对所设计的控制算法进行验证;实验结果表明,所设计的控制器能够满足系统的控制性能要求。     

一种共轴双旋翼飞行器悬停控制联合仿真

利用Adams/MATLAB联合仿真平台,对一种具有周向均匀分布3个舵机的操纵机构共轴双旋翼飞行器悬停控制问题进行了研究。考虑到目前对上旋翼和下旋翼之间气动干扰没有准确的数学模型,在动力学建模时利用叶素理论和Pitt-Peters动态入流模型对飞行器的气动干扰和挥舞运动进行近似建模,其他未准确建模的部分用控制算法进行补偿。选用鲁棒性较强的滑动模态控制算法并与PID算法相结合对飞行器姿态进行控制,同时利用PID算法建立姿态和位置的关系,使其具备按照空间坐标点悬停的能力。将装配模型导入Adams中建立动力学模型,在Simulink搭建控制器并进行联合仿真。研究结果验证了所设计控制方法的有效性,飞行器悬停位置的最大动态误差小于±0.2 m.     

小型无人直升机悬停小速度段位置控制技术

无人直升机在悬停/小速度飞行阶段具有特殊的物理特性,给控制系统的设计带来了诸多技术难题;针对无人直升机悬停/小速度段位置控制的需求,提出了一种基于"姿态角阻尼内回路"的位置控制结构,该控制结构采用内回路姿态角阻尼增稳,外回路位置控制的控制方式;并且针对增稳回路自适应性、抗风补偿和位置控制精度等问题,分别采用前馈自动配平机制与非线性PID控制方法对常规控制律进行改进;仿真验证表明,所提出的控制策略和控制律设计结果达到了较好的控制效果。     

自抗扰控制器在AUV悬停定深控制的应用

针对传统控制方法在水下自主航行器(AUV)悬停定深控制中难以满足高精度快速性要求的问题,提出了将自抗扰控制应用到该系统中的方法;建立了在推进器停止工作状态下的悬停定深控制模型,介绍了一种自抗扰控制算法以及模型仿真方法,提出参数整定的一些经验结论,在此基础上对自抗扰控制算法与经典PID控制算法进行仿真比较,结果表明,自抗扰控制器在AUV悬停定深控制中超调量小,调节时间短,抗干扰能力强,并且在海况较复杂时能进行快速稳定调节,具有一定的实用性和推广价值。     

Getting Wet About Urban Design

Neil Spiller is thrilled by IwamotoScott's Hydro-Net - a futuristic design proposal for San Francisco that thinks about water in an entirely new way. Copyright © 2008 John Wiley & Sons, Ltd.     

Chandavarkar and Thacker

The first architectural firm in Bangalore, founded in 1947 by Narayan Chandavarkar, Chandavarkar and Thacker is currently under the directorship of Prem Chandavarkar and Sai Shankar Bharatan. Continuing the collaborative nature of the practice during its many reorganisations over the years, Prem Chandavarkar has also given the firm a new intellectual edge by confronting Bangalore's new urbanity, and as such is a role model for many younger-generation architects. The practice's current work represents thoughtful and reflective responses as architecture finds itself at a critical juncture in this city of a euphoric present.With the practice's 60-year history, Chandavarkar is particularly aware of the humility and ‘backgroundness’ that once characterised the culture of the city in contrast to the present voluble environment. He has written (including in his essay in this issue) about the nature of practice and production, and has argued why a critical and self-reflexive practice needs to be the order of the day. Chandavarkar and Thacker speak of an ‘aesthetics of absorption’ and a ‘negotiated practice’, both of which should inform a much needed criticality of the exuberant conditions today. ‘A building does not convey meaning as much as it slowly absorbs it,’ declares the practice, and so the test of a building is not the initial impression of its spectacular presentation, but the accrued experiences and memories of its everyday inhabitation. In their understanding of culture as an active and ongoing phenomenon, and hence one not yet susceptible to definition, the architects bring an open-endedness to their own practice. The result is an avoidance of a predetermined language of expression, and thus the variety of spatial, volumetric, site and technofunctional responses, in their array of works. Copyright © 2007 John Wiley & Sons, Ltd.