**1. Introduction**

To design or to assess the exoskeleton robot, it is necessary to simulate human motion with interactive force from exoskeleton robot. Thus, we need the human modeling and simulation which method the interactive force from exoskeleton can be applied at. This is key motivation in this study and we formulate human motion simulation with modular exoskeleton model and predict human motion with interactive from modular waist and knee exoskeleton robot. To do that we formulate human motion with assistive force from exoskeleton robot. There are many good researches based on optimization techniques for simulation in different areas [1–4]. There are couple of human modeling and simulation software such as OpenSim [5]. By given motion OpenSim can generate muscle forces for that motion. Other is Santos which is optimization-based motion simulation so called predictive dynamics [6]. Some of human motion simulation is developed under optimization-based motion simulation [7, 8]. And, lifting motions are studied with optimization based technique as well [9, 10]. The modeling and simulation for human-exoskeleton is developed in [11]. In this study, we also use optimization-based motion prediction and simulation method with recursive Lagrange's equations of motion which is highly nonlinear. It provides predicted human motion as well as joint torques and ground reaction forces for weight lifting. This method also gives us pretty fast calculation time and accurate results.
