## 3 Results and Discussion
### Subjective Measures  
Overall, all subjects completed the telemanipulation experiments under the three conditions. In the post-experiment questionnaire, the Baseline case was rated as the most difficult task condition by the majority of participants. Most subjects preferred the MRS vision/motion mapping scheme condition and commented that the MRS scheme enabled robot control with natural movements and reduced fatigue and stress during the robotic manipulation process.  
The NASA-TLX score shows how participants rated their qualitative experiences of mental demands, physical demands, temporal demands, performance, effort, and frustration. The TAM was used for evaluating acceptance and measuring participant perception of different HRI modules, and scales to measure usefulness and ease-of-use were presented to the subjects in each post-task questionnaire. Three items on a seven-point rating scale (1 = strongly disagree; 7 = strongly agree) were included for each of the two aspects. As shown in Figure 6, all average NASA-TLX scores were lower for the MR-subspace-enhanced motion-mapping tasks compared with the 2D Baseline and MR SpaceMouse cases. In particular, the MR subspace motion-mapping module significantly reduced the physical and mental demand as well as the frustration of participants.  
Figure 5: Boxplots of quantitative measures on the user performance for each HRI scheme across two manipulation tasks. **(a)** Time to complete the pick-and-place tasks; **(b)** the assembly task completion time; **(c)** the aggregate task completion time; **(d)** the mean training completion time. MRD and MRS denote MR SpaceMouse and MR subspace, respectively.  
In general, the Overall Workload (OW) decreased from Baseline (M = 75.81) compared to the MR SpaceMouse module (M = 66.89) and the MR subspace module (M = 51.92), as shown in Figure 6f. As a result, the average score of NASA-TLX decreased significantly by 32% (F(1.663, 38.247) = 74.408; \(p<0.001\); Partial = 0.87) when the MR subspace mapping was used.  
The TAM results indicate that there was a substantial disparity between the means of the users appeals of the three different HRI modules. Participants found that the MR-subspace-imitation-based HRI module (M = 5.50) had better usability than the 2D Baseline (M = 2.67), and was marginally easier to use than the MR SpaceMouse module (M = 3.25), as shown in Figure 7a. The MR subspace method (M = 4.75) was reported to be slightly more acceptable than the MR SpaceMouse module (M = 3.08) and 2D Baseline interfaces (M = 2.83) in terms of perceived usefulness, as shown in Figure 7b. The subjective measures analysis proved that the MR-subspace-enhanced spatial motion mapping approach for telemanipulation outperformed the other typical teleoperation modules in task workload and user perception.  
Figure 6: Boxplots of workload measures for each HRI scheme across two tasks. MRD and MRS denote MR SpaceMouse and MR subspace, respectively.  
In this paper, the isometric-rate tele-control paradigm through MR-based 3D motion and visualization retargeting scheme for telerobotics is compared to the isotonic-position 3D interaction condition and a conventional 2D Baseline. The system performance analysis indicates that the MRS scheme improved the tele-control performance of manipulation tasks and reduced the workload on operators. The results of this study will benefit the research community moving forward by providing experimental groundwork for other researchers to select appropriate command/control schemes to construct intuitive HRI systems. Furthermore, the results provide a fundamental platform for ongoing research to incorporate haptic feedback and machine learning strategies, aiming to further improve the immersive teleoperation platform developed.