Modular robot is a robot development systemcomposed of a series of standard joint modules  connection modules. Modular joints arethe central component ofmodular robots ,  each modular joint has standard mechanical  electrical interfaces. The outstanding advantages of modular robots are reconfigurable, easy to maintain, high flexibility  reliability,  have a wide range of application prospects.

      In this paper, based on the modular planning thinking proposed in the National 863 Program Project "Integrated Service System for Robots in Space Laboratory Cabin", the planning  discussion of modular joints are carried out. Based on the analysis of the current status of modular joint research at home  abroad, combined with the requirements of the subject, the planning  analysis of the overall scheme of modular joints have been completed.

      According to the task requirements of the modular robot, the method of stepwise recursion  the top (the end of the claw) to the bottom (the base) is used to calculate the maximum torque received by each joint of the module; the geometric error of the module  the end of the robot are established The model of the relationship between the gripper to the large azimuth error,  the model is used to calculate the robot's ending grip to the azimuth.

      Finally, the planning goal of the modular joint is determined,  the selection of the main components of the modular joint is completed. According to the skill requirements of the three-branch modular robot, the modular planning thinking is used to plan a robot modular joint that integrates a mechanical system, a drive system, a sensor system, a control system  a power system,  has a standard mechanical  electrical interface . Specifically, a joint torque sensor based on the principle of strain type  a cross-elastic elastic beam structure is selected, so that the joint has the ability to maintain torque  bending moment overload. Completed the selection of modular joint materials, specific structural planning, wiring planning, system integration planning, multiple connection module planning  other operations.