高超声速飞行器快速平滑自适应二阶滑模控制

Fast and smooth adaptive second-order sliding mode control for hypersonic vehicles

摘要:

为解决高超声速飞行器在爬升的过程中存在严重匹配/非匹配不确定性的问题,提出了一种新型的自适应超螺旋滑模控制方法以抑制爬升段存在的匹配不确定性,并将该方法与滑模微分器相结合,以解决爬升段存在的非匹配不确定性.首先用滑模微分器估计反馈线性化模型中速度和高度的各阶导数,以缩小反馈线性化模型与原模型的差距；其次在传统超螺旋滑模的基础上,加入线性项以提高收敛速度；将积分项中不连续的符号函数连续化,保证控制输入的平滑性,更大程度削弱抖振；针对未知上界复合干扰,设计了一种自适应参数可增大可减小的自适应律,保证参数既不过大估计,又可放宽初值的选取,保证收敛速度. 仿真结果表明:改进后的控制方法可实现状态量在有限时间内跟踪上指令信号,完成控制要求；且相较于传统超螺旋滑模控制算法,改进的控制方法控制输入更加平滑,收敛速度更快,从而验证了该方法的有效性以及先进性.

Abstract:

To solve the problem of severe matching/non-matching uncertainty of hypersonic vehicles in the process of climbing, a new adaptive super-twisting sliding mode control method was proposed to suppress the matching uncertainty of the ascent phase, and the method was combined with a sliding mode differentiator to resolve the non-matching uncertainty of the ascent phase. Firstly, the sliding mode differentiator was used to estimate the derivatives of the velocity and height in the feedback linearization model to narrow the gap between the feedback linearization model and the original model. Secondly, on the basis of the traditional super-twisting sliding mode, a linear term was added to increase the convergence speed. Then, the discontinuous symbolic functions in integral terms were made continuous to ensure the smoothness of the control input, which eliminated or attenuated the chattering to a greater extent. Lastly, since the upper bound of the composite disturbance was unknown, an adaptive law was designed to ensure that the parameters were not overestimated and the initial value could be chosen to ensure the convergence speed. Simulation results show that the improved control method can meet the control requirements, and compared with the traditional super-twisting sliding mode control algorithm, the improved control method had smoother control input and faster convergence speed, which verifies the effectiveness and advancement of the proposed method.