Abstract
Cryogenic wind tunnel is a sophisticated aerodynamics ground test facility, which operates in cryogenic temperature with injection of liquid nitrogen. The multi-variable, nonlinear and coupled dynamics existing between the temperature, pressure and Mach number in the tunnel, poses great challenges for the effective control of the tunnel. L1 adaptive control is a new control methodology developed in recent years with good robustness properties, which has good potentials to address these challenges. But this control method does not provide full adaptive feedforward control in its generic structure. In the paper, adaptive feedforward control action is introduced into the standard L1 adaptive control architecture for nonlinear systems in the presence of matched un-modeled dynamics. This new control structure is applied to the stagnation pressure control in a cryogenic wind tunnel, which could also be used for the control of temperature and Mach number in the tunnel. This new method could effectively compensate known disturbances with linear gain uncertainty, which occur in the nonlinear systems, while retaining the closed-loop control performance of L1 adaptive control. After the proof and discussions on the stability of this method, simulations of the stagnation pressure control in the wind tunnel are presented. The results and analysis demonstrate the effectiveness of the proposed control architecture.
Highlights
Cryogenic wind tunnel is a sophisticated aerodynamics ground test facility which can provide real flight Reynolds number by operating the wind tunnel in cryogenic temperature with the injection of liquid nitrogen into tunnel circuit [1]
This paper mainly introduces adaptive feedforward control into the standard L1 norm of signal in math (L1) adaptive control for nonlinear system to provide full compensation for known disturbances with linear gain uncertainty
The adaptive feedforward control is based on conventional adaptive scheme, while it is fully integrated into the L1 adaptive control structure
Summary
Cryogenic wind tunnel is a sophisticated aerodynamics ground test facility which can provide real flight Reynolds number by operating the wind tunnel in cryogenic temperature with the injection of liquid nitrogen into tunnel circuit [1]. The purpose of this paper is to deploy a new adaptive control method with guaranteed transient performance, L1 adaptive control [9], to implement the control of cryogenic wind tunnel. The main advantage is that it could equip the control system with some self-learning capabilities and would find proper control parameters automatically to achieve desired control performance under uncertainties in the system or model inaccuracies of the tunnel. This paper mainly introduces adaptive feedforward control into the standard L1 adaptive control for nonlinear system to provide full compensation for known disturbances with linear gain uncertainty. The adaptive feedforward control is based on conventional adaptive scheme, while it is fully integrated into the L1 adaptive control structure This new control structure is applied in the stagnation pressure control of a cryogenic wind tunnel.
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