Actuators for exoskeleton robots comprise various types such as electric, hydraulic, and pneumatic and it is necessary to apply the correct actuator according to the purpose. Most exoskeleton robots mainly use electric actuators, and some special-purpose robots, such as for heavy-load transport requiring large force, use hydraulic actuators. In this paper, friction of the actuation module consisting of a harmonic drive and a brushless DC motor is measured through experiments. And the friction characteristics of the actuation module are analyzed. The harmonic drive transmission system has various advantages, but it also has hysteresis and nonlinear friction characteristics. The friction compensation control of the actuation module enables precise control of the exoskeleton robot, and improves the robot’s performance. Appropriate friction model selection and design affects friction compensation performance. In this study, static and dynamic friction models are designed and analyzed based on the friction data of the actuation module.

The objective of this study was to address the parameter estimation of the line-of-sight stabilization system on temperature variation, which is a significant element in regulating the control performance of mobile platform with visual targeting system. To this end, the LuGre friction model in this study was used both to represent the characteristic of the friction behavior and to design a control algorithm for the friction compensation. Results from both simulation and experimental tests helps to identify the friction parameters on LuGre friction model. Based on LuGre with parameter estimation, PI-LEAD control algorithm is designed to compensate nonlinear characteristic of the line-of-sight stabilization system on the variation of temperature. Finally, through simulation, the good control performance of line-of-sight stabilization system was evaluated according to the temperature variation.