Test your system for stability through different calculations--simulations, eigenvalues of state matrix, internal stability with disturbances/uncertainties, nyquist criterion. The nominal plant, nominal plant with uncertainties, and the full nonlinear plant if any.

Check controllability and observability through transforming to CCF , OCF, diagonal forms, and Kalman decomposition. Comment on how observable or controllable your system states are based on the observability and controllability matrices and their eigenvalues when physical variables are used for the state variables.

This might give you ideas for what sensors to install and where, the type/power of actuators needed and how/where to mount them into your plant. When you return to this portion later after doing some control design, you are likely to identify many paths to significant innovation here.

Note: The system is a "Cruise Control System"