Temperature control of cryogenic wind tunnel with a modified L1 adaptive output feedback control

Rusong Zhu,Zili Guo,Shuangxi Zhang,Guofu Yin,Zhenhua Chen

doi:10.1177/0020294018808672

Abstract

Background: Temperature is one of the main variables need to be regulated in cryogenic wind tunnel to realize the true flight Reynolds number. A new control methodology based on L1 output feedback adaptive control is deployed in the temperature control. Methods: This design is composed of three parts: linear quadratic Gaussian baseline control, L1 adaptive control and nonlinear feedforward control. A linear quadratic Gaussian controller is implemented as the baseline controller to provide the basic robustness of temperature control. A L1 output feedback adaptive controller with a modified piecewise constant adaptive law is deployed as an augmentation for the baseline controller to cancel the uncertainties within the actuator’s bandwidth. The modified adaptive law can guarantee better steady-state tracking performance compared with the standard adaptive law. A global nonlinear optimization process is carried out to obtain a suboptimal filter design for the L1 controller to maximize the performance index. The nonlinear feedforward control is to cancel the coupling effects in control of the tunnel. Results: With these design techniques, the augmented L1 adaptive controller improves the performance of the baseline controller in the presence of uncertainties of dynamics. The simulation results and analysis demonstrate the effectiveness of the proposed control architecture. Conclusion: The modification of adaptive law plus the global nonlinear optimization of the filter in the L1 adaptive control architecture helps the controller achieve good control performance and acceptable robustness for the temperature control over a wide range of operations.

Highlights

Reynolds number is one of the main parameters used to evaluate the similarity between wind tunnel tests and true flight tests in aerodynamics
Some cryogenic wind tunnels with high Reynolds number capabilities have been built in some well-known research institutes in the world, such as the DNW-KKK cryogenic wind tunnel in Koln, Germany; 0.3 m Transonic Cryogenic Tunnel (TCT) and the National Transonic Facility (NTF) at NASA in the United States; and the European Transonic Wind (ETW) tunnel in Germany.[3,4]
The uncertainties mainly cover parameter uncertainties, and the ranges of the uncertainties can characterize possible parameter variations at operation points. This result shows that the linear quadratic Gaussian (LQG) baseline controller and L1 augmented controller have much better control performance than the conventional PI, and the L1 augmented controller outperforms the LQG baseline controller

Summary

Introduction

Reynolds number is one of the main parameters used to evaluate the similarity between wind tunnel tests and true flight tests in aerodynamics. Because the Reynolds number is directly related to temperature in cryogenic wind tunnel, the temperature is one of the main parameters need to be controlled precisely over a wide range, which is regulated by injecting the liquid nitrogen into. Temperature is one of the main variables need to be regulated in cryogenic wind tunnel to realize the true flight Reynolds number. Conclusion: The modification of adaptive law plus the global nonlinear optimization of the filter in the L1 adaptive control architecture helps the controller achieve good control performance and acceptable robustness for the temperature control over a wide range of operations

Objectives

Results

Conclusion