Collaborative robots are a relatively new concept in robotics and industrial automation. Traditional industrial robots are relatively expensive, heavy, and dangerous devices for humans since they are enclosed in working cells with fences. Nowadays, in small and medium enterprises (SMEs), instead of traditional robots lightweight and versatile robots are required which can work alongside human co-workers. In such applications, human safety is a critical factor. ISO has produced new standards for these robots to regulate their collaborative work with human co-workers and named these robots as collaborative robots. The subject of the thesis is related to the actuation systems of light-weight collaborative robots. For these robots, a variety of actuation systems are designed in recent years which are usually modular and compact actuation systems. The main aim of the thesis is to analyze and model of a commonly used actuation system in collaborative robots and to verify its model.