In this paper a simplified triangular model is suggested for approximating the impulse response of a stable system. The triangular model has only three parameters and is easy to identify. Both dead-beat controller and extended horizon predictive controller are redesigned based on this triangular model. Under simple conditions the robust stability and zero tracking error of the resulted closed-loop system are guaranteed. Simulations show that two kinds of robust controllers are effective and work well even with unknown piecewise-constant disturbances.