I don't believe you're allowed to call non-static class methods from within the constructor itself. Until the constructor returns, the variable "this" is not known to be of class Module.
Since you're passing in Parameters, StateVariables, and ControllableInputs as inputs to the FindStateSpace method, I think an easy work around is to make it a static method.
Before the final "end" statement of this file, do something like:
function StateSpace = FindStateSpace(Parameters, StateVariables, ControllableInputs)
In the constructor, use the static method as follows:
this.StateSpace = Module.FindStateSpace(Parameters,StateVariables,ControllableInputs);