水下运载器多变量鲁棒输出反馈控制方法

针对存在较大参数不确定性和仅具有位置、姿态测量的水下运载器的六自由度位姿控制难题,提出一种基于自适应平滑增益滑模观测器和多变量积分Backstepping控制器的非线性控制方法.解决水下运载器的鲁棒输出反馈控制问题,使用基于Lyapunov稳定性理论的设计方法保证观测器-控制器系统的稳定性.设计的自适应平滑增益滑模观测器,克服常规滑模观测器中所存在的高频颤振现象,从而获得较平滑的速度估计值.当存在模型不确定性和有界未知干扰时,可以保证速度估计误差以指数速率收敛至较小的球域内.设计的多变量积分Backstepping控制器,可以保证系统的跟踪误差同样收敛至较小的球域内.以浙江大学正在研制的海王号ROV六自由度控制为研究对象,使用所提出的控制方法与传统PID控制器进行对比仿真研究.仿真结果表明,当存在较大参数不确定性、较强未知外干扰和测量噪声时,所提出的控制方法具有较强的鲁棒性能,可以很好地跟踪参考轨迹,获得较好的动态性能和稳态控制精度.性能明显优于常规PID控制器,并且解决了PID控制器所存在的转艏角设定值不能大于90°的问题.

Studies on multivariable robust output feedback control for underwater vehicles

For the 6-DOF(degrees of freedom) position and attitude control of underwater vehicles with large parameter uncertainties and only position and angle measurement,a novel nonlinear control algorithm based on adaptive gain smooth sliding observer and multivariable integrated backstepping controller was designed to realize the robust output feedback control of underwater vehicles.By Lyapunov stability design method,the stability of observer-controller system was guaranteed.The adaptive gain smooth sliding observer eliminates the high frequency switching that usually appeared in traditional sliding observer,and obtains a smooth velocity estimation.And in the presence of model uncertainties and bounded unknown disturbances,the velocity estimation error will converge into a small ball field by exponential speed.The multivariable integrated backstepping controller can also guarantee the tracking error converge into a small ball field.For the 6-DOF control of Sea-king ROV which is developing in ZHEJIANG university,some comparative simulation results were performed using new proposed controller and traditional PID cotnroller respectively.The simulation results prove that in the presence of parameter uncertainties,unknown disturbances and measurement noise,the new proposed controller has strong robustness,and the underwater vehicle can track the desired trajectory very well with good dynamic performance and steady accuracy at the same time.Its performance is better than PID controller obviously,and the restriction that the set point of heading can not greater than 90 degrees in PID controller has been removed.