A nonlinear variable structure (VS) system is presented, suitable for smooth trajectory generation in motion control system. Joined to a rough reference trajectory generator (step, ramp, etc.) it provides smooth output signals according to user-selectable bounds on trajectory derivatives. The bounds on output derivatives can be changed during system operation without impairing system stability. Moreover, minimum time response with guaranteed no overshoot is ensured both in the continuous and discrete-time implementations. The main contribution of the paper lies in the discrete-time version of the trajectory generator. The performance of the proposed nonlinear filters is tested through simulation experiments. Simulation results concerning the use of the discrete filter in a position tracking control system are also presented.