小型无人机载云台高性能控制方法研究

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题名	小型无人机载云台高性能控制方法研究
作者	朱志强
学位类别	博士
答辩日期	2014-12-05
授予单位	中国科学院沈阳自动化研究所
授予地点	中国科学院沈阳自动化研究所
导师	韩建达
关键词	机载云台 PID控制二自由度控制扰动抑制前置滤波器
其他题名	Reasearch on high-performance control method for platform used on small unmanned helicopter
学位专业	模式识别与智能系统
中文摘要	机载云台能够隔离载体的扰动，在动态环境下精确保持探测设备的姿态基准，并实现对机动目标自动跟踪，因此在动平台传感探测系统特别是航空航天遥感与测量系统中应用广泛。机载云台的作用有两个：1. 隔离动态基座（如飞机）的晃动、振动，以避免对负载造成影响，从而保证所承载的感知类设备（如摄像机、雷达等）获得稳定而清晰的探测信息，如视频等；2. 对这些感知类负载设备的视轴进行实时控制，从而实现对动态目标的跟踪。对于小型无人机机载云台的控制而言，除了要满足上述普通云台的振动抑制与伺服跟踪两个基本功能要求以外，还有其自身的特殊性要求。第一个问题源于小型无人机的载重能力限制。为了减小云台的自身重量，云台本体采用了碳纤维结构。这就造成了云台本体结构的刚性不足，导致控制系统设计过程中的被控对象建模困难。为了绕开建模困难或者模型不确定性严重的问题，本文探索研究了无模型条件下的控制器参数调整问题。其次，小型无人直升机的发动机所造成的振动和螺旋桨所造成的风扰都比较大，因此对云台的抗扰动能力提出了更高的要求；第三个问题是关于云台的伺服跟踪性能，绝大部分情况下，小型无人直升机载云台被用于在低空情况下对地面快速目标的实时跟踪，因此云台的控制系统需要具备良好的伺服跟踪能力。为了满足上述小型无人机机载云台的控制系统设计要求，本文针对云台自身特性及性能要求进行了一系列的控制方法研究。首先，针对云台系统建模难的问题，作者探索了已有的频域控制思想并在此基础上提出了一种无模型条件下的PID控制器参数调整方法。在研究过程中，通过参数变换以及借助bode图分析了PID控制器参数与PID控制器开环幅相特性的关系；通过对系统Nyquist曲线及其所在复平面性质的分析得到了系统的开环幅相特性与闭环幅值特性之间的关系。利用这两种关系便可以得出PID控制器的各个参数是如何影响PID控制系统在各个频段处的幅值的。基于上述分析结果，最终给出了一套无模型条件下的PID控制器的参数调整规则。这套准则能够在保证系统稳定性良好（系统响应输出中无振荡或振荡很小）的前提下，控制器的参数值尽可能地大，以保证系统伺服响应速度较快或扰动抑制能力较强。采用这套规则，便可以直接根据系统的响应输出曲线特性对PID控制器参数进行调整，从而避开了系统建模这一难点。相关内容详见本文第二章。其次，为了进一步增强系统的抗扰动性能，本课题在速度反馈的基础上增加了加速度反馈。然而，反馈回路之间的参数耦合增加了参数调整的难度，导致两种反馈信息不能得到充分地利用。为此，本文提出了一种基于扰动补偿器的2DOF控制方法，这种方法具有一系列优点：结构简单，易于实现；扰动补偿器增益的变化对整体系统的伺服跟踪特性影响微弱；适用于内环路的加速度反馈设计。采用这一控制方法，解决了双环路控制系统中角速度反馈与角加速度反馈之间的耦合问题。使得角加速度信息得到充分的利用以提高系统的抗扰动性能。详见本文第三章。再次，云台控制系统的设计目标是要使系统同时具有良好的伺服跟踪性能和扰动抑制性能。然而一般的单自由度控制方法只能其中的某一性能达到最优。针对这一问题，本文创新地提出了基于前置预滤波二自由度控制方法。并给出了一种前置预滤波器的基于最小二乘法的设计方法。这套方法能够使得系统的抗扰动性能和伺服跟踪性能得到解耦，即分开设计。从而避免了单自由度控制系统中的性能耦合所导致的两个性能不能同时到达最优的问题。详见本文第四章。最后，本课题创新地设计了一套两轴云台性能验证实验系统。采用这套系统，对本文所提出的各个控制方法进行了实验验证。实验结果表明，云台具有良好的扰动抑制性能和伺服跟踪性能，从而验证了所提方法的有效性。具体详见本文第五章。
索取号	TP273/Z83/2014
英文摘要	Airborne platform could isolate the vibration of the carrier, precisely keep the attitude reference for the detection equipments, and realize the automatic tracking of the maneuvering target, thus gained extensive application in the field of mobile platform sensing and detecting system such as aerospace remote sensing and measuring systems. There are two functions of airborne platform: 1. Isolating the waving and vibration of the carrier to avoid their affection on the detection equipments to ensure them (like cameras, radars) obtaining stable and clear detected information, such as videos; 2. Maneuvering the line of sight in a realtime maner to realize the automatic target tracking. As to the platform used on the small unmanned helicopter, beside the two aforesaid basic function requirements, there are other special problems of its own. The first problem comes from the limited load capacity of the small unmanned helicopter. To reduce the weight of the platform, the mechanical body is built of carbon fiber which leads to poor rigidity of the platform. Thus the object model building for the control system designing is difficult. To avoid the problem of model building, the author explored the method of controller parameter tuning without object model. The second problem is the higher requirement on disturbance suppression due to the engine’s vibration and the wind disturbance caused by the rotor. The third problem is about the servo tracking performance. In most cases, the platform on the small unmanned helicopter is used for the real time tracking of fast target on the ground under the case of low altitude conditions, thus the platform control system needs to have fine servo tracking capacity. To fulfill the aforesaid requirements on the design of platform for the small unmanned helicopter, this paper carried out a series of studies on the controller design methods based on the characteristics of the platform as well as the performance requirements. First, to solve the problem of modeling difficulty, the author explored the existing frequency control ideas and proposed a PID parameter tuning method that can be applied under the condition of no object modeling. In the process of researching, through parameter transformation and with the help of bode diagram, the relationship of PID parameters and open loop magnitude and phase properties; through the analysis of Nyquist curve of the object system and the corresponding complex plane, the relationship between the open loop magnitude and phase properties and the closed loop magnitude is obtained. Using these two relationships, it can be found how each on of the PID parameters influence the closed loop magnitude of PID control system at different frequency sections. Based on these analysis results, a set of tuning rules of PID parameters that necessitates only the system outputs of the closed-loop responses is devised. This set of rules can maximize the controller parameters to make the sytem be of quick response speed and fine disturbance suppression while the system stability is ensured (there is no or little vibration in the system output). Applying this set of tuning rules, PID controller parameters can be tuned directly based on the characteristics of the system response outputs, and the difficulty of modeling is avoided. The detailed content can be found in chapter 2. Next, the designing aim of platform control system is to make the system be of fine servo tracking and disturbance suppression performance. However, the common single degree of freedom control method can only optimize one of these performances. To solve this problem, this paper introduces the 2DOF (2 degree of freedom) control method and carried out detailed research on the concrete realization including the controller structure design and parameter tuning. Two 2DOF controller structures are proposed: disturbance compensation based 2DOF control and pre-filter based 2DOF control. The former has fine real time property but is confronted with the problems of incomplete decoupling between the two sub-controllers and that the parameters can’t be tuned in an analytical way; while that later is poor in real time application but has a set of complete tuning methods and the two sub-controllers are totally decoupled. In this paper, the transformation between these two control structures is analyzed and the merits of them can be possessed by the finally designed control system. The detailed contented is given from chapter 3 to chapter 5.
语种	中文
产权排序	1
页码	145页
内容类型	学位论文
源URL	[http://ir.sia.ac.cn/handle/173321/16806]
专题	沈阳自动化研究所_机器人学研究室
推荐引用方式 GB/T 7714	朱志强. 小型无人机载云台高性能控制方法研究[D]. 中国科学院沈阳自动化研究所. 中国科学院沈阳自动化研究所. 2014.