Damage-mitigating control of space propulsion systems for high performance and extended life

Abstract

A major goal in the control of complex mechanical systems such as spacecraft rocket engines, advanced aircraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current practice of decision and control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the materials degradation. In view of the high performance requirements of the system and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea in this repon is that a significant improvement in service life could be achieved by a small reduction in the system dynamic performance. The major task is to characterize the damage generation process, and then utilize this information in a mathematical form to synthesize a control law that would meet the system requirements and simultaneously satisfy the constraints that are imposed by the material and structural properties of the critical components.The concept of damage mitigation is introduced for control of mechanical systems to achieve high performance with a prolonged life span. A model of fatigue damage dynamics is formulated in the continuous-time setting, instead of a cycle-based representation, for direct application to control systems synthesis. An optimal control policy is then formulated via nonlinear programming under specified constraints of the damage rate and accumulated damage. The results of simulation experiments for the transient upthrust of a bipropellant rocket engine are presented to demonstrate efficacy of the damage-mitigating control concept

Damage-mitigating control of hypersonic flight vehicle based on prescribed performance

“…According to Ray and Wu (1993), no damage occurs when the equivalent stress l is decreasing (decreasing reversal). Therefore, we have…”

“…where is the nonlinear damage and ð l Þ is a function of l . The approach to evaluate ð l Þ is based on selected discrete level of stress amplitude by interpolation which was reported by Ray and Wu (1993). According to the result of Ray and Wu, ð l Þ ¼ ð2=3Þ À0:4 l is considered here.…”

Adaptive Life Extending Control of Aircraft Engine

“…Lorenzo et al. first introduced LEC in the early 1990s [3][4][5] , which was applied to the Space Shuttle Main Engine (SSME).…”

Analysis of damage characteristics of an aeroelastic model for air-breathing hypersonic vehicles

“…Porowski et al (1985) established a linear cumulative damage model for the cooling jacketed spacer of a rocket engine, however, this model could only calculate the damage offline. Ray et al (1993) established a time-based continuous damage dynamic model based on the strain life method, which can realize the online damage calculation for the key components of space propulsion systems; however, the two adjacent cyclic stress peaks were needed to be known, which increases the computational complexity. To reduce the number of online calculations, Lorenzo (1994) established a model for calculating damage based on the current stress and strain.…”