Robust Tracking Control of a Quadrotor Helicopter

In this paper, a robust tracking control method for automatic take-off, trajectory tracking, and landing of a quadrotor helicopter is presented. The designed controller includes two parts: a position controller and an attitude controller. The position controller is designed by the static feedback control method to track the desired trajectory of the altitude and produce the desired angles for pitch and roll angles. By combining the proportional-derivative (PD) control method and the robust compensating technique, the attitude controller is designed to track the desired pitch and roll angles and stabilize the yaw angle. It is proven that the attitude tracking error of each channel can converge to the given neighborhood of the origin ultimately. Experimental results demonstrate the effectiveness of the designed control method.     

Implementation of Hard Real-Time Embedded Control Systems

Although the domain of hard real-time systems has been thoroughly elaborated in the academic sphere, embedded computer control systems –- being an important component in mechatronic designs –- are seldom dealt with consistently. Often, off-the-shelf computer systems are used, with no guarantee that they will be able to meet the requirements specified. In this paper, a design for embedded control systems is presented. Particularly, the paper deals with the hardware architecture and design details, the operating system, and high-level real-time language support. It is shown how estimates of process run-times necessary for schedulability analysis can be acquired on the basis of deterministic behavior of the hardware platform.     

面向可重构控制器实时中间件的设计与实现

可重构控制器的出现要求系统软件模块不但要满足性能和精度要求,还应具有模块化、可集成、可重用等特性.如果将实时中间件引入到控制器的设计中,由中间件管理模块间的交互,可实现控制器的可重构.建立基于RTLinux和实时CORBA的实时中间件平台,需要将CORBA引入RTLinux实时内核空间.该文给出了RTLinux实时内核中的实时CORBA和minimum CORBA实现RTCK的设计,并基于RTLinux MBuff共享内存驱动和实时FIFO设计和实现了GIOP通信协议,最后给出了RTCK与TAO的延迟抖动测试结果并做了相关的分析.     

A New Nonlinear Controller for Trajectory Tracking of the Longitudinal Dynamics of a Small Scale Helicopter

A nonlinear control scheme is proposed for the trajectory tracking problem of a small scale helicopter’s longitudinal dynamics. The control scheme is based on a control design procedure that constructs static feedback regulators for nonlinear systems which are linearizable by dynamic feedback. Besides, the flatness characteristics of the helicopter’s longitudinal dynamics are used to design the desired trajectory. The controller proposed is based on the longitudinal model of the small scale helicopter including the main rotor and stabilizer bar dynamics. Sufficient conditions are given to guarantee asymptotic convergence to zero of the tracking error and to keep the main rotor thrust always negative assuming that all the helicopter’s parameters are known and that all helicopter’s states are measured. Numerical simulations are given to show the performance of the controller in the presence of the main rotor and stabilizer bar dynamics.     

小型四旋翼直升机的建模与仿真控制

针对实现对小型四旋翼直升机的飞行控制,为提高飞行性能和加强稳定性,根据四旋翼直升机特有的机械结构和飞行原理,利用牛顿-欧拉方程建立了小型四旋翼直升机的飞行动力学数学模型,而且对该型进行了合理的简化.同时在Matlab/Simulink仿真环境下,采用直升机动力学模型搭建了模块化、层次化的系统仿真图,并通过PID控制算法对直升机悬停状态进行仿真,实现了直升机姿态控制.仿真结果表明在具有小扰动的条件下,模型能够仿真小型四旋翼直升机的飞行状态,满足直升机飞行姿态的控制要求.     

四旋翼自主飞行与轨迹跟踪控制

研究四旋翼自主飞行控制和轨迹跟踪控制。建立四旋翼动力学模型,通过实验测量与曲线拟合测得旋翼升力和力矩系数。在姿态控制中引入加速度反馈控制,增加闭环零点提升系统稳定和快速跟踪能力,抵消不确定干扰影响。提出一种基于切向速度和法向位置误差反馈控制的轨迹跟踪控制策略,对设定轨迹进行分段逼近跟踪,通过室外轨迹跟踪飞行试验,验证控制策略设计的有效性。     

四旋翼自主飞行器的控制器设计与仿真

四旋翼自主飞行器是一类具有强耦合性和欠驱动特点的空中机器人.从空气动力学和飞行运动学两方面分析并建立了其机理模型,提出了相应的参数辨识方法.根据模型的串级结构,设计了一种新型的控制器,在考虑白噪声的影响下建立了Simulink仿真并验证了该控制方案的稳定性和鲁棒性.     

基于FPGA的模糊逻辑控制器的硬件实现

提出了一种基于现场可编程门阵列(FPGA)的模糊逻辑控制器的硬件实现方法,并将其用于倒立摆控制系统。实验研究表明,在倒立摆倾角小于10°时,软件或硬件控制效果相当,在倾角大于10°时硬件模糊控制器的控制效果明显优于软件模糊控制器的控制效果,而且前者的抗扰动性能更好。当倾角大于30°时,由于机械性能方面的原因,倒立摆的稳定性有所降低。因此,采用该方法不仅快,而且是一种足以灵活完成数字模糊控制器的方法。该设计方法稍加修改亦可应用于其他控制场合,具有良好的通用性。     

An Efficient Model Predictive Control Scheme for an Unmanned Quadrotor Helicopter

In this paper, an efficient Model Predictive Control (eMPC) algorithm deploying fewer prediction points and less computational requirement is presented in order to control a small or miniature unmanned quadrotor helicopter. A model reduction technique associated with the dynamics of an unmanned quadrotor helicopter is also put forward so as to minimize the burden of calculations in application of MPC into an airborne platform. For three-dimensional tracking control of the quadrotor helicopter, simulation results corresponding to the algebraic formulation—presented in this paper—versus the standard MPC formulation commonly found in the literature further illustrate effectiveness of this study. Unsuccessful implementation of the standard formulation on the testbed due to computational burden proves the necessity and advantages of this new approach. Eventually, to demonstrate effectiveness of the developed MPC algorithm, the suggested algebraic-based MPC framework is successfully implemented on an unmanned quadrotor helicopter testbed (known as Qball-X4) available at the Networked Autonomous Vehicles Lab (NAVL) of Concordia University for tracking control of the unmanned aerial vehicle.     

A Real-Time Implementation of Nonlinear Unsharp Masking with FPLDs

Real-time performance of image enhancement algorithms is required in many applications. In this paper we present a real-time image contrast enhancement scheme using non-linear unsharp masking, implemented with FPLDs (Field Programmable Logic Devices). A quadratic filter has been chosen for the nonlinear unsharp masking. The implementation performs well on real images from medical and non-medical fields. Performance figures of the nonlinear filter on mammograms show substantial improvements over software-only and other filter implementations using linear schemes, thus achieving real-time image enhancement of large images. The implementation has been tested as an application-specific co-processor to a standard PC, but can also be used as a functional unit of an application-specific image enhancement processor.     

基于PD-ADRC的四旋翼控制器设计

针对四旋翼无人机强耦合、非线性的控制难点,研究设计了一种基于自抗扰控制和比例微分控制的双闭环控制器。首先,分析了小型四旋翼飞行器动力学模型,确定四旋翼无人机的六自由度方程。然后,利用自抗扰控制技术对强耦合、非线性的姿态模型进行了解耦,设计扩张状态观测器对其总扰动进行观测与补偿。其次,设计比例微分控制器对解耦后的系统进行位置跟踪,从而与姿态控制器组成双闭环系统。最后,通过仿真及试飞实验测试系统性能。仿真和试飞结果表明该系统能够完成对控制指令的实时跟踪,并且对干扰具有极强的抑制力。     

基于自适应单神经元PID的四旋翼飞行控制研究

针对传统增量式PID控制算法在四旋翼飞行器的姿态控制中自整定参数不足的缺点,提出了一种改进的自适应单神经元PID控制算法,该算法在单神经元加权系数调整的基础上引入PSD自适应控制方法,增加了对比例系数的自适应调整;通过建立四旋翼飞行器的动力学模型和飞行试验平台对该改进算法进行仿真验证;仿真结果表明,采用自适应单神经元PID算法的控制器结构简单且响应速度快,精度高,具有更高的鲁棒性和自适应能力,能有效的实现四旋翼飞行器姿态的稳定控制。     

基于模糊自整定PID 四旋翼无人机悬停控制

四旋翼无人直升机是一种多输入、强耦合、多变量、欠驱动的系统,其可以应用到航拍、考古、边境巡逻、反恐侦查等多个领域,具有广阔的前景。根据欧拉定理以及牛顿定律建立四旋翼无人直升机的动力学模型,并且考虑了空气阻力、转动力矩对于桨叶的影响,而后基于经典PID 算法设计了双环控制系统,之后在此基础上结合模糊控制技术设计了模糊自整定PID 控制器。通过Matlab /Simulink 对两种控制算法设计的控制器进行仿真比较,从仿真结果可以看出两种控制算法均可使四旋翼无人直升机到达指定位置并且保持悬停状态,但模糊自整定PID 算法设计的控制系统在响应时间以及稳定性方面优于经典PID 下的控制系统的控制效果。     

一种用于硬实时Java处理器的类转换器设计及实现

通过分析Class文件处理过程及其中影响实时性的操作，提出一种用于硬实时Java处理器的类转换器，它读取标准Class文件，处理并生成适合Java处理器直接执行的内存映像文件．由于装载、连接过程中大量操作（如符号引用的解析）都由类转换器提前处理完毕，使得Java处理器操作大为简化．同时，由于所有影响Java处理器实时性的操作也由类转换器提前处理，Java处理器最坏情况执行时间（Worst Case Execution Time）完全可预测．     

A Learning-Based Fault Tolerant Tracking Control of an Unmanned Quadrotor Helicopter

This paper presents a novel learning-based fault tolerant tracking control approach by using an extended Kalman filter (EKF) to optimize a Mamdani fuzzy state-feedback tracking controller. First, a robust state-feedback tracking controller is designed as the baseline controller to guarantee the expected system performance in the fault-free condition. Then, the EKF is employed to regulate the shape of membership functions and rules of fuzzy controller to adapt with the working conditions automatically after the occurrence of actuator faults. Next, based on the modified fuzzy membership functions and rules, the baseline controller is readjusted to properly compensate the adverse effects of actuator faults and asymptotically stabilize the closed-loop system. Finally, in order to verify the effectiveness of the proposed method, several groups of numerical simulations are carried out by comparing the performance of a tracking control scheme and the presented technique. Simulation results demonstrate that the proposed method is effective for optimizing the fuzzy tracking controller on-line and counteracting the side effects of actuator faults, and the control performance is significantly improved as well.     

基于FPGA的非线性PID控制器设计与实现

行车取力发电技术的核心问题是如何实现液压泵控马达系统输出转速恒定.而由变量泵一定量马达组成的液压变转速泵控马达系统输出转速存在非线性波动现象,为实现其恒转速输出,提出一种以基于转速偏差的指数函数为参数的非线性PID控制算法.该指数函数实质是一种新型、具有自动修正功能的非线性函数,能反映PID控制器各参数的变化规律.利用FPGA完成非线性PID算法的硬件实现,采用“FPGA+ SOPC架构”技术设计了泵控马达恒转速输出控制系统.实验结果表明,在系统负载突变工况下,泵控马达系统输出瞬间转速波动量最大为80 r/min,瞬时超调量小于3.5％,调节时间不超过2.8s,发电参数达到了国家三类发电要求.     

Attitude Stabilization of a Quadrotor by Means of Event-Triggered Nonlinear Control

In this paper, a quaternion-based feedback is developed for event-triggered attitude stabilization of a quadrotor mini-helicopter. The feedback is derived from the universal formula for event-triggered stabilization of general nonlinear systems affine in the control. Event-triggered control is a resource-aware sampling strategy that updates the control value only when a certain condition is satisfied, which denotes event instants. Such a technique allows a reduction of the control computational cost and communications demand. The proposed feedback ensures asymptotic stability to the desired attitude. Real-time experiments are carried out in order to show the convergence of the quadrotor states to the desired attitude as well as robustness with respect to external disturbances. Results show that the proposed strategy can reduce by 80 % the number of control function calls and consequently reduce the communications of the embedded system without sacrificing performance of the whole system. To the best of the authors’ knowledge, this is the first time that a nonlinear event-triggered controller is experimentally applied to the attitude stabilization of an unmanned aircraft system.     

直升机着舰实时目标定位姿态预测仿真

直升机着舰需要精确定位机舰相对位置,但海浪运动和光照情况复杂,对目标的检测定位十分困难,导致直升机着舰安全性难以保证,因此对目标实现精确的实时定位姿态预测有重要作用。首先,设计易于识别检测的合作目标,保证在各种角度下有效识别,以应对复杂的海浪运动;然后采用可变阈值分割,自适应多种光照条件。之后对于单目视觉下得到的连续帧图像进行图像处理,获取特征点数据,满足实时性要求。最后利用EPnP算法进行2D-3D场景重建,为直升机着舰提供实时的相对位姿信息,并利用增强现实技术显示,帮助驾驶员准确操作。通过理论分析和计算机半实物仿真,所提方法可以在不同光照不同角度下实现精度较高的姿态预测。上述仿真为直升机着舰视觉引导提供了一种新的解决思路。     

Experimental Test of a Two-Stage Kalman Filter for Actuator Fault Detection and Diagnosis of an Unmanned Quadrotor Helicopter

This paper addresses the problem of Faut Detection and Diagnosis (FDD) of a quadrotor helicopter system in the presence of actuator faults. To this end a Two-Stage Kalman Filter (TSKF) is used to simultaneously estimate and isolate possible faults in each actuator. The faults are modelled as losses in control effectiveness of rotors. Three fault scenarios are investigated: loss of control effectiveness in one single actuator, simultaneous loss of control effectiveness in all motors, and loss of control effectiveness in three motors with different magnitudes. The developed FDD algorithm is evaluated through experimental application to an unmanned quadrotor helicopter testbed available at the Department of Mechanical and Industrial Engineering of Concordia University, called Qball-X4. The obtained results show the effectiveness of the proposed FDD method.     

基于强化学习的四旋翼高度控制器设计

针对四旋翼飞行器高度控制通道易受干扰的问题,在先验飞行数据基础上,利用局部加权线性回归算法建立了四旋翼飞行器的非参数模型,该模型考虑了实际飞行中干扰因素对高度控制的影响.以此非参数模型为基础,运用强化学习算法构建了四旋翼飞行器高度控制算法,并以离线方式优化了控制算法的结构参数.最后通过实际的飞行实验验证了控制算法的合理性.