A modeling system for a control parameter of a vehicle comprises a first model that formulates the control parameter in terms of linear spline basis functions, coefficients, and knots. A second model is derived according to the first model, includes coefficients that are derived according to the linear spline basis functions, coefficients, and knots, and forms a linear equation for the control parameter. A memory module stores the linear equation. A control module calculates the control parameter according to the linear equation.