Design of Fixed- and Multi-Rate Sample-Data Control Systems
The focus of this research is on the modeling and design of practical sample-data (fixed-and multi-rate) digital control systems.
Relevant Application Areas
Relevant application areas include:
- Aerospace systems
- Robotic systems
- Thermal processes
- Low power DC-DC converters
Relevant Control Challenges
Designing digital controllers with reasonable measurement (sampling) and actuation rates that address each of the following issues:
- selection of sampling/actuation rates (bandwidth management)
- time delays and quantization effects associated with A/D converters
- nonlinear finite precision arithmetic and wordlength/quantization effects associated with embedded processors
- time delays associated with D/A and zero-order-hold (ZOH)
- lag associated with anti-aliasing filter (AAF)
- uncertain nonlinearities (e.g. variable constraints),
- uncertain high frequency dynamics (i.e. unmodeled differential equations),
- parametric uncertainty,
- uncertain actuator and sensor dynamics,
- centralized versus decentralized control architectures,
- controller complexity and implementation issues,
- multiple time-scale dynamics; e.g. multiple measurement/actuation rates,
- selection of weighting function parameters for dynamical optimization,
- assessment of fundamental performance limitations and tradeoffs,
- stabilization,
- following of varying (typically low frequency) reference commands,
- attenuation of (stochastic, typically low frequency) disturbances,
- attenuation of (stochastic, typically high frequency) measurement noise,
- state estimation,
- parameter and uncertainty estimation (system identification).
Embedded controller implementation platforms include:
- PC104s, field programmable gate array (FPGA) technologies.
High-level development tools are exploited to facilitate rapid prototyping for the above embedded system platforms.
Objectives and Goals
The main objective of this research is to develop a systematic design methodology which addresses each of the above sample-data control system design challenges.
Approaches
Synchronous sampled-data systems are periodic systems provided that there is a common sampling/actuation period (frequency); i.e. sampling/actuation periods/rates are integer multiples of a fundamental periods/rate. Given this, modern lifting concepts can be used to exploit the inherent periodicity and permit time invariant representations which can be used for analysis/design purposes. Here, performance-based optimization is the main design approach.
Collaborators and Sponsors
Collaborators include: Professor Petros Voulgaris (University of Illinois, Urbana-Champaign).
This work has been sponsored by the following organizations:
- National Science Foundation (NSF) and the Consortium for Embedded and Inter-Networking Technologies (CEINT).
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