Exoskeletons are used in different applications including the area of physical therapy in order to facilitate the patient's exercises and as an assisting technology to assist the elderly carry out their ordinary activities. At the beginning of this paper, the RoboWalk assistive device is introduced. Before constructing the system, the performance of the device must be analyzed through different simulations. Hence, the dynamics of the human and RoboWalk are then obtained using the Newton-Euler (NE) and the Recursive Newton Euler Algorithm (RNEA). The obtained models are then augmented to the human model to estimate the RoboWalkjoint forces and torques, and those of the human model. then, RoboWalk is imported to the human model in Opensim software and the augmented model is obtained by defining some constraints and joint models. Controllers are then designed for the human and Robo Walk in Opensim. In the next step, The NE and RNEA models are then compared to the models obtained from Opensim software using the same gait data. It is shown that the NE and RNEA methods match very closely and both of the models possess the same behavior as the Opensim model.