93C05 Linear systems
93C10 Nonlinear systems
93C15 Systems governed by ordinary differential equations [See also 34H05]
93C20 Systems governed by partial differential equations [See also 35B37]
93C23 Systems governed by functional-differential equations [See also 34K35]
93C25 Systems in abstract spaces
93C30 Systems governed by functional relations other than differential equations
93C35 Multivariable systems
93C40 Adaptive control
93C41 Problems with incomplete information
93C42 Fuzzy control  
93C55 Discrete-time systems
93C57 Sampled-data  systems
93C62 Digital systems
93C65 Discrete event systems
93C70 Time-scale analysis and singular perturbations
93C73 Perturbations 
93C80 Frequency-response methods
93C83 Control problems involving computers (process control, etc.)
93C85 Automated systems (robots, etc.) [See also 68T40, 70B15, 70Q05]
93C95 Applications
93C99 None of the above, but in this section