The concept and construction of quantitative measures of regular languages have been recently reported in literature. Major applications of the language measure include quantitative analysis and synthesis of discrete-event supervisory control algorithms. This paper formulates and experimentally validates an on-line parameter identification procedure for the language measure based on a deterministic finite state automaton model of the physical plant. The recursive algorithm of this identification procedure relies on observed simulation and/or experimental data. Efficacy of the language parameter identification procedure is demonstrated for real-time supervisory control by experiments on a mobile robotic system.