Design and Functional Verification of a Robot Motion Sensor

The outer wall of the rocket tank needs to be sprayed with multi-layer and multi-component thermal insulation coating. To ensure the thickness, uniformity and quality of the coating layer and improve the automation level, it is the best choice to use robot to perform the spraying operation. However, the intricate tank spraying conditions lead to high error rate and great difficulty in planning robot path in the complex structures. In order to tackle above-mentioned problems, this paper designs a robot-end target motion sensor, aiming to realize the robotic spraying movement guided by human direct contact, which transforms the human guiding motion into the robot's motion control quantity. Through the motion experiment, the motion sensor can recognize operator’s motion in the process of grasping the sensor and guiding the robot to move, and using the sensor can control the robot to smoothly run along the desired path. Introduction The tank is a significant component of the carrier rocket storing propellant fuel. Additionally, it also plays an important role in connecting the front and rear functional components and ensuring the overall aerodynamic layout. The outer wall of the rocket tank needs to be sprayed with multi-component, multi-layer insulation coating, and the coating coverage index should be 100%. However, at present, the trajectory planning process of the robot is of great difficulty to implement, and it is hard to ensure that the planned spraying quality meets the requirement of the technical indicators. Due to the limitations of the existing robot spraying method, the challenge is obviously huge in terms of the rocket tank spraying task [1]. In recent years, with the idea of human-computer interaction, human-machine coordination and human-computer integration, the sensing and motion response of robots to external interaction and interaction force has become the focus and hotspot of research. The KUKA iiwa seven-joint cooperative robot [2] is the most representative one that uses the joint torque sensor to realize force interaction. It combines the external moment detection algorithm with the joint torque sensor to estimate the external interaction force, which can realize functions including collision detection, variable stiffness control and robot traction teaching etc. Le Dinh Phong et al. [3] measured the joint torque by the joint torque sensor, and estimated the unknown input of the state space equation based on the time delay estimation, where no precise dynamic equation is needed. But this approach is mainly suitable for the lightweight human-computer collaboration process. It is one of the most common and mature ways to install a six-dimensional force sensor at the robot end to improve the force sensing and force control capabilities. Liu Kun [4] used the UR robot as a platform to sense the teaching ability and torque of the operator with a force/torque sensor, converting into the target displacement, which achieved good demonstration effect. Zhang Jian [5] developed a six-dimensional force sensor to acquire three-dimensional cutting force vector in real time, and composed a method to generate robot deburring trajectory based on impedance control model. SeungHoon Lee et al. [6] installed two six-dimensional force sensors at robot end to sense the operator's teaching force and sense the robot's grinding contact force, thus realizing the teaching task of robot deburring. This paper designs a robot sensor installed between the end joint of robot and the actuator. The sensor can be applied to the guidance of various industrial robots. It is suitable for individualized operation tasks without further programming. For the spraying task of the outer wall of the tank, the