A standard form for linear and nonlinear perfect model following control problems is introduced, and the associated control laws developed. The error dynamics of such systems are analyzed with respect to stability of the error. The effects on the error dynamics of measurement errors and parameter variations are also analyzed, and it is seen that the perfect model following control problem is reduced to that of an error regulator.

The linear problem is analyzed to show that virtually all common problems are equivalent to standard form problems through similarity transformations. In the standard form, simple expressions for the control law and error dynamics are used to solve the problem.

The linear problem is also analyzed with respect to problems of different order model and plant systems, resulting in augmented system equations. These augmented systems are chosen so that the original dynamics are retained, and so that the higher order problem is in the standard form. The standard form problem is then solved as before.

Imperfect model following control problems are analyzed, with three associated results. First, a new t€St for perfect model following is developed. Pairs of models and plants that fail this or other tests are imperfect model following control problems. Second, the effect of using perfect model following control laws on such problems is determined to be equivalent to the addition of a forcing function on the error regulator problem. Third, a new approach to the solution of imperfect model following control problems is shown. This approach seeks to find models that simultaneously satisfy the criteria for perfect model following while retaining the desired characteristics of the intended model.

The methods developed in this analysis are applied to problems that illustrate all the principles addressed. The final example is a detailed application to a nonlinear simulation of the F-18 airplane involving control of all degrees of freedom over a large range of angles of attack.