The necessity of improving the air traffic and reducing the aviation emissions drives to investigate automatic steering for aircraft to effectively roll on the ground. This paper addresses the path following control problem of aircraft-on-ground and focuses on the task that the aircraft is required to follow the desired path on the runway by nose wheel automatic steering. The proposed approach is based on dynamical adaptive backstepping so that the system model does not have to be transformed into a canonical triangular form which is necessary in conventional backstepping design. This adaptive controller performs well despite the lack of information on the aerodynamic load and the tire cornering stiffness parameters. Simulation results clearly demonstrate the advantages and effectiveness of the proposed approach.
Directing to the strong position coupling problem of electro-hydraulic load simulator(EHLS),this article presents an adaptive nonlinear optimal compensation control strategy based on two estimated nonlinear parameters,viz.the flow gain coefficient of servo valve and total factors of flow-pressure coefficient.Taking trace error of torque control system to zero as control object,this article designs the adaptive nonlinear optimal compensation control strategy,which regards torque control output of closed-loop controller converging to zero as the control target,to optimize torque tracking performance.Electro-hydraulic load simulator is a typical case of the torque system which is strongly coupled with a hydraulic positioning system.This article firstly builds and analyzes the mathematical models of hydraulic torque and positioning system,then designs an adaptive nonlinear optimal compensation controller,proves the validity of parameters estimation,and shows the comparison data among three control structures with various typical operating conditions,including proportion-integral-derivative(PID) controller only,the velocity synchronizing controller plus PID controller and the proposed adaptive nonlinear optimal compensation controller plus PID controller.Experimental results show that systems' nonlinear parameters are estimated exactly using the proposed method,and the trace accuracy of the torque system is greatly enhanced by adaptive nonlinear optimal compensation control,and the torque servo system capability against sudden disturbance can be greatly improved.
This paper intends to provide theoretical basis for matching design of hydraulic load simulator (HLS) with aerocraft actuator in hardware-in-loop test, which is expected to help actuator designers overcome the obstacles in putting forward appropriate requirements of HLS. Traditional research overemphasizes the optimization of parameters and methods for HLS controllers. It lacks deliberation because experimental results and project experiences indicate different ultimate performance of a specific HLS. When the actuator paired with this HLS is replaced, the dynamic response and tracing precision of this HLS also change, and sometimes the whole system goes so far as to lose control. Based on the influence analysis of the preceding phenomena, a theory about matching design of aerocraft actuator with HLS is presented, together with two paired new concepts of "Standard Actuator" and "Standard HLS". Further research leads to seven important conclusions of matching design, which suggest that appropriate stiffness and output torque of HLS should be carefully designed and chosen for an actuator. Simulation results strongly support that the proposed principle of matching design can be anticipated to be one of the design criteria for HLS, and successfully used to explain experimental phenomena and project experiences.
This paper deals with the high performance force control of hydraulic load simulator. Many previous works for hydraulic force control are based on their linearization equations, but hydraulic inherent nonlinear properties and uncertainties make the conventional feedback proportional-integral-derivative control not yield to high-performance requirements. In this paper, a nonlinear system model is derived and linear parameterization is made for adaptive control. Then a discontinuous projection-based nonlinear adaptive robust force controller is developed for hydraulic load simulator. The proposed controller constructs an asymptotically stable adaptive controller and adaptation laws, which can compensate for the system nonlinearities and uncertain parameters. Meanwhile a well-designed robust controller is also developed to cope with the hydraulic system uncertain nonlinearities. The controller achieves a guaranteed transient performance and final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities; in the absence of uncertain nonlinearities, the scheme also achieves asymptotic tracking performance. Simulation and experiment comparative results are obtained to verify the high-performance nature of the proposed control strategy and the tracking accuracy is greatly improved.
YAO JianyongJIAO ZongxiaYAO BinSHANG YaoxingDONG Wenbin
