摘要
质量矩控制技术是近些年来提出的一种新型飞行器控制方式,它通过快速改变飞行器内部可移动质量块的位置来改变飞行器的质心,从而产生控制力矩以达到飞行器快速姿态响应和获得所需过载的目的。而欠驱动系统是指控制输入个数少于系统自由度个数的控制系统,它广泛存在于机器人、航空航天和交通运输等各个领域,由于控制输入的缺失使得欠驱动控制问题成为控制领域具有挑战性的研究热点之一。当质量矩飞行器内部可移动质量块的个数少于需要控制的姿态自由度个数时,该质量矩飞行器的姿态控制系统就是一种典型的欠驱动系统,研究其控制问题不但具有很强的实用价值,而且有助于促进欠驱动系统控制理论的发展。
本文以欠驱动系统的能控度分析和控制设计作为理论研究基础,对大气层内欠驱动质量矩飞行器的特征参数优化设计方法和姿态控制设计方法进行了研究。
对于大气层内工作的质量矩飞行器,考虑飞行器内部空间的限制,提出一种姿态控制的欠驱动配置方案,该方案采用两个沿直线导轨运动的质量块。通过推导两个质量块运动对转动惯量矩阵和气动力矩的影响,并基于拉格朗日方法建立欠驱动质量矩飞行器姿态控制系统的动力学模型。为了降低特征参数优化设计和姿态控制设计过程中的复杂性,对动力学模型进行简化处理,为后续研究奠定了基础。
针对欠驱动系统的能控度分析问题,提出将欠驱动状态的恢复区域作为欠驱动系统能控度分析的度量指标。一方面,考虑了欠驱动系统的控制输入具有幅值限制的条件,通过研究欠驱动系统模型的级数展开形式,提出欠驱动系统时间最优能控度的分析方法。另一方面,考虑了欠驱动系统的控制输入具有能量限制的条件,通过求解欠驱动系统的能量最优控制问题,提出欠驱动系统能量最优能控度的分析方法。
基于欠驱动系统的时间最优能控度分析及其指标,提出欠驱动质量矩飞行器特征参数的优化设计方法。将质量块位置输入有界情况下欠驱动自由度方向上姿态角的恢复区域定义为欠驱动质量矩飞行器的能控度指标,并将该能控度指标作为优化设计的目标函数,建立能控度指标与特征参数之间的函数关系。基于静稳定性分析、质量块功率限制和滚转角与俯仰角机动能力分析,提出欠驱动质量矩飞行器特征参数优化设计时需要满足的约束条件。在此基础上,提出欠驱动质量矩飞行器特征参数优化设计方法的具体步骤。仿真验证特征参数优化设计方法的有效性。
基于欠驱动系统的无源化控制设计思想,提出欠驱动质量矩飞行器的姿态控制设计方法。通过研究欠驱动系统的无源化控制方法,设计得到在平衡点处的渐近稳定控制规律。为了保证欠驱动系统反馈控制规律的存在性,给出了选择Lyapunov函数时需要满足的匹配条件。由于该匹配条件是难于求解的非线性偏微分方程,进一步研究了匹配条件的简化和求解方法。基于无源化控制提出欠驱动质量矩飞行器姿态控制设计方法,为了满足求解匹配条件解析解过程中的假设条件,对姿态控制模型进行部分反馈线性化处理,并基于求解匹配条件得到姿态系统的无源化控制规律。仿真验证姿态控制设计方法的有效性。
将特征参数优化方法和姿态控制设计方法应用到大气层内某型欠驱动质量矩飞行器的姿态控制设计中。通过分析欠驱动质量矩飞行器的机动方式,提出欠驱动质量矩飞行器姿态控制系统的性能指标要求,在此基础上,基于特征参数优化设计方法得到最优特征参数值。然后,基于以攻角、侧滑角和滚转角作为状态变量的数学模型,应用无源化控制方法设计姿态控制规律,使得攻角、滚转角跟踪期望的指令值,侧滑角保持在零值附近;最后,在闭环情况下仿真验证特征参数优化设计的有效性,并在考虑干扰力矩、质量块动态特性和气动参数摄动的情况下分别验证姿态控制设计的有效性。
The mass moment control technique is proposed as a new control method for space-craft in recent years, whose principle is to change the mass-center of the spacecraft bymoving the position of the masses inside the spacecraft with high-speed, so as to producemoment to obtain the fast attitude response and the required overload of the spacecraft.Underactuated systems are control systems with fewer control inputs than the numberof configuration variables, which are widely existed in robotics, aerospace vehicles, andtransportation vehicles. And the control of underactuated systems is becoming an activeand challenging field of research due to the lack of control inputs . Since the mass mo-ment spacecraft holds fewer actuators than the number of attitude freedom, the attitudecontrol systems of the mass moment spacecraft are typical underactuated systems.Thecontrol of underactuated attitude system is not only a practical but also a helpful work tothe development of control theory on underactuated systems.
In the framework of control theory on underactuated systems , this dissertation isdevoted to special parameter optimal design and attitude control of underactuated massmoment spacecraft based on degree of controllability and control design.
Firstly, due to the limitation of the internal space of the craft, an underactuatedconfiguration for attitude control, which holds two masses moving along linear lines, isproposed subjected to the mass moment spacecraft. The dynamical model of underac-tuated mass moment spacecraft is established by Lagrangian method, considering theimpacts to the inertia and aerodynamic torque caused by the moving of the masses. Fur-thermore, a simplified model of underactuated mass moment spacecraft is derived forreducing the complexity for design.
Secondly, it is proposed that taking the recovery region of the underactuated statesas the index measurement, in terms of degree of controllability analysis. On one hand, atime optimal degree of controllability analysis method is derived by studying the seriesexpanding form of underactuated systems, considering the limitation of amplitude ofthe inputs. On the other, an energy optimal degree of controllability analysis method isderived by solving the energy optimal control problem due to the limitation of energyinputs.
Thirdly, an optimization design method of special parameters is studied based on time optimal degree of controllability of the underactuated mass moment spacecraft. Thefunctional relation between the index of degree of controllability and the special param-eters is established based on the definition of index of degree of controllability for under-actuated systems, taking the recovery region of the attitude angle, which belongs to thedirection of degree of freedom that is underactuated when the position input is bounded,as the index measurement. An optimization design of special parameters is operated bytraversal in order to enhance the capability to change the attitude angel. The effectivenessof the design is proved by a simulation example.
Furthermore, the attitude control method of underactuated spacecraft is studied, and an asymptotically stable control law is driven by passivity control method at equilibria.The matching condition is proposed to make sure that the control law is existed. Due tothe complexity of the nonlinear partial differential equations, the matching conditionis simplified and solved. The effectiveness of the control law is proved by simulationexamples.
Lastly, on the basis of utilizing optimization and passivity method to implementthe underactuated system control design, the attitude control problem for a certain un-deractuated mass moment spacecraft in atmosphere is provided. Based on the analysisof the maneuver manner of the underactuated mass moment spacecraft, performance in-dex requirement of attitude control system is presented. The characteristic parametersoptimal design is implemented by considering restriction conditions of these parameters.The attitude controller law considering the Euler attitude angles as state variables is pre-sented to allow angles of attack and roll to track desired commands and angle of slide tostay close to zero, which satisfies the performance index requirement of attitude controlsystem. Finally, the close loop simulation shows the effectiveness of the characteristicparameters optimization and the attitude control method by considering disturbance mo-ment, the dynamics of mass displacement and atmospherical parameters perturbation,respectively.
引文
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