## 2 Related Work  
More recent research attention has focused on MR-enhanced tele-welding paradigms [22]. It was verified in [23] that there were no statistically significant differences in the total welding scores between participants in the physical welding group and the mixed reality-based welding groups. The mixed reality welding user interface gives operators the ability to perform welding at a distance while maintaining a level of manipulation [24]. An optical tracking-based telerobotic welding system was introduced in [25]. The Leap Motion sensor captures the trajectory of a virtual welding gun held by a human welder in userspace to control the remote welding robot for the welding task. However, this welding system requires the use of a physical replica of the workpiece for welding in the userspace to project a real-time weld pool state and guide the welders to adjust their hand movements to the shape of the workpiece [26]. [PERSON] et al. [27] developed an MR-based human-robot collaborative welding system. The collaborative tele-welding platform combines the strengths of humans and robots to perform weaving gas tungsten arc welding (GTAW)tasks. The welder can monitor the welding process through an MR display without the need to be physically present. Welding experiments indicated that collaborative tele-welding has better welding results compared to welding performed by humans or robots independently. MR-based robot-assisted remote welding platforms were developed in [28] to provide the welders with more natural and immersive human-robot interaction (HRI) [29]. However, in these systems, the users rely on visual feedback for movement control and have no haptic effects to completely prevent accidental collisions between the robot and the workpiece when the operator controls the robot for welding from a distance. A visual and haptic robot programming system based on mixed reality and force feedback was developed in [30], but the system was not suitable for real-time remote welding operations and was inefficient in unstructured and dynamic welding situations. Haptic feedback provides the welders with additional scene modality and increases the sense of presence in the remote environment, thereby improving the ability to perform complex tasks [31; 32; 33]. The primary benefit of incorporating haptic effects is to enhance the tele-welding task performance and operator's perception [34]. These existing remote robotic welding systems do not take sufficient advantage of the potential performance improvements that various forms of haptic effects can bring to the user. The rapid development of MR-enhanced teleoperation has led to the integration of MR and virtual fixtures (VF) to improve task performance and user perception [35; 36]. The integration of MR and VF in RTWS can effectively address the defects and problems that exist in the above telerobotic welding systems. The immersive and interactive MR environment allows for the effective generation of virtual workpieces in the user space [37] and can be combined with VF technology to provide force feedback and guidance to users, thereby improving the accuracy of robot movements and effectively preventing accidental collisions [38; 39]. The main weakness of the published studies on tele-welding is that existing remote-controlled robotic welding systems do not adequately incorporate MR technology and virtual fixtures to effectively eliminate potentially harmful collisions in the tele-welding process and grant welding robots human-level dynamics for dexterous GMAW welding tasks. No attempt has been made to reduce operational complexity to assist inexperienced welders to perform welding quickly and address the time-consuming training and shortage of a qualified workforce [40]. In this work, an on-site welding experiment was designed to investigate the motion difference between the expert and unskilled welders, extracting the expertise and skills of professional welders to optimize the robotic tele-welding platform.