CAREER: Integrated Design of Intelligent Structures with Tailored Distributed Damping

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

This Faculty Early Career Development (CAREER) Program research project aims to investigate a fundamentally new approach for designing intelligent structures for vibration and motion control, create new numerical design strategies, and to generate a foundational understanding for how best to design this new class of intelligent structures. Existing intelligent structures use integrated sensors and actuators, such as piezoelectric materials, distributed across the surface or interior of a flexible elastic material to control dynamic behavior. Here embedded viscoelastic materials (VEMs) are introduced to overcome current performance limitations. Incorporating VEMs is challenging because 1) engineers cannot rely on past experience to design this unprecedented system, and 2) accurate VEM models are computationally expensive. Here new integrated design optimization strategies will be used to accelerate generation of design knowledge for this new type of intelligent structure, and to reduce computational expense. Numerical and physical experiments will center on application to precision pointing for space-based telescopes. More precise pointing has the potential to enhance significantly scientific data gathering, including search for exoplanets. These advances also have potential to advance other domains where ultra-quiet structural stability or precision motion control is critical (e.g., manufacturing, robotics, and defense). Education and outreach components of this CAREER project involve the creation of unique hands-on activities that allow K-12 and undergraduate students to experience the value of design automation tools. These are enhanced by collaborations with the "Girls do Science" program at the Orpheum Children's Museum and a CubeSat project with NASA's Jet Propulsion Laboratory. Intelligent structures (IS) have been studied extensively, but primarily for active damping as opposed to motion control, and have largely avoided incorporation of spatially distributed VEMs for damping. Inclusion of VEMs and extension to motion control could help achieve new performance levels, but introduces a profound design challenge as no design history, validated design guidelines, or expert intuition exist. Current IS technology utilizes spatially distributed control actuation to tailor dynamic behavior. Recent work has combined control tailoring with distributed geometric elastic substructure design. A remaining obstacle is control of high-order structural modes in practical implementations, and is addressed here via strategically distributed VEMs to damp high-order modes passively. VEM distribution can be varied spatially to synergize with elastic material and control distribution. This enhances design flexibility, but this adds a new level of complexity. A new concept for integrated dynamic system design optimization where surrogate models of the state space derivative function are constructed and improved adaptively is planned. This capitalizes on the intrinsic properties of dynamic systems for numerical efficiency. VEMs can be modeled accurately, but with great computational expense, using high-order ordinary differential equation (ODE) approximations. The new derivative function surrogate modeling (DFSM) strategy is posited to produce high-accuracy VEM modeling using efficient low-order ODEs with state-dependent parameters. DFSM adjusts parameter mappings adaptively to improve accuracy, which supports efficient low-order computation. After thorough study of DFSM for damped IS design, DFSM will then be used for rapid design exploration and systematic generation of design data. Machine learning strategies will then be used to identify patterns and relationships within this data. An iterative inductive process will be used to identify possible design guidelines from these results, such as preferred distributed shape relationships or sensor/actuator/VEM placement guidelines. Additional numerical design studies will be used to validate/refine design guidelines.