Adaptive Control of a Dual-Mode Scramjet Flow Path Utilizing Optical Emission Optical Emission Spectroscopy

Optical emission spectroscopy (OES) was utilized for shock train leading edge (STLE) location control within a Dual-Mode Scramjet (DMSJ) flow path. Electronically excited chemical species, OH* and C2*, were observed and implemented for control of the STLE within the DMSJ isolator. This control strategy was then experimentally demonstrated with a Proportional-Integral (PI) controller and compared to a more standard method of feedback using pressure measurements. Utilizing an OES sensor for feedback was an effective method to estimate and control the STLE location whereas utilizing the pressure measurements showed evidence of a bias in estimated STLE which provided difficulty when attempting to follow a reference signal in-between pressure measurement locations. A Characteristic Model-Based All-Coefficient Adaptive Control (ACAC) was then experimentally demonstrated and compared to a PI controller response using the OES signal as feedback. Plant changes were introduced in the form of mass addition downstream of the combustor, to increase the plant gain and introduce an offset, and a reduction of fuel valve response, to simulate a malfunctioning fuel valve. Experiments showed that the ACAC and PI controllers behave very similarly both during nominal conditions and with plant changes, though the ACAC controller provided a more efficient control response during all conditions. This is the first time closed-loop control of the STLE location within a scramjet isolator flow path utilizing OES sensor feedback is experimentally demonstrated. This is also the first time adaptive control was experimentally proven viable within this system utilizing OES sensor feedback.