This paper presents a nonlinear control scheme for position control of a flexible beam system using Shape Memory Alloy (SMA) actuators. Due to their interesting properties such as force generation capacity, possibility of miniaturization, and power consumption, these devices have been gaining increased popularity in the past few years. However, SMA actuators possess undesirable characteristics such as nonlinearities, hysteresis, extreme temperature dependencies, and slow response that make them difficult to use in precision applications. By taking into account the nonlinear and thermal characteristics, a control scheme is developed in order to regulate the force exerted by an SMA actuator attached to a flexible beam. The control scheme is based on input-output linearization of the nonlinear system. The control goal is to regulate the force exerted by the SMA actuator to a desired value. The internal dynamics of the system is derived and it is shown that these dynamics can be stabilized by proper choice of controller gain matrices. Simulation results are presented based on the data for a setup that is currently under construction in our laboratory.