An analytical model for predicting the characteristics of variable airgap linear force motors is developed. The model takes into account magnetic losses, including the leakage and fringing effects, and the reluctance existing at the contacts between permanent magnets and polepieces. The model is validated by comparing its predicted characteristics with the results obtained from experiments and a finite element program. With the use of the modelled characteristics, computer programs based on the method of constrained steepest descent with state equations, is developed for automating and optimising the design of linear force motors. Numerical studies are made for both minimisation of weight and minimisation of power consumption.