Min-Max Design of Feedback Quantizers for Netorwked Control Systems

In a networked control system, quantization is inevitable to transmit control and measurement signals. While uniform quantizers are often used in practical systems, the overloading, which is due to the limitation on the number of bits in the quantizer, may significantly degrade the control performance. In this paper, we design an overloading-free feedback quantizer based on a ∆Σ modulator, composed of an error feedback filter and a static quantizer. To guarantee no-overloading in the quantizer, we impose an l∞ norm constraint on the feedback signal in the quantizer. Then, for a prescribed l∞ norm constraint on the error at the system output induced by the quantizer, we design the error feedback filter that requires the minimum number of bits that achieves the constraint. Next, for a fixed number of bits for the quantizer, we investigate the achievable minimum l∞ norm of the error at the system output with an overloading-free quantizer. Numerical examples are provided to validate our analysis and synthesis. Index Terms quantization, overloading, delta-sigma modulation, networked control, linear matrix inequalities