## 5 Conclusions and Future Works  
In this paper, we presented an intuitive CDPR haptic device for user-friendly teleoperation of a fully constrained CDPR at a remote site. We designed the main hardware of the haptic device configured with the CDPR mechanism and built and embedded a controller with driving circuits based on a commercialized microprocessor. For the force control related to the reactive feeling of an operator at the master device, an adjustable admittance control scheme was applied to the control algorithm, where we considered the specifications of existing haptic devices and angle of force measurements for reducing the measurement error of the force sensors.  
For the performance verification, we configured the remote-control environment by using the proposed CDPR haptic device and MINI IPAnema 3. As a result, we verified that the developed master device successfully controlled the remotely connected slave CDPR by an operator. Synchronized movements of the master and the slave device were realized, and adjustable force depending on the object was achieved. Based on the prototyped system, we validated the performance and the advantages of the proposed system for a specific task. The main contributions of this work are: (1) we advanced the conceptual intuitive bilateral teleoperation concept of using two CDPRs in [19] to be able to be used at a user's desk by prototyping a mini CDPR; and (2) the engineering parts required to build a microprocessor-based CDPR are provided in detail, which may be helpful for further relevant research into CDPR development with minimally sized parallel robots. This study shows that the microprocessor can compute an amount of complex numerical computations in a short time.  
Even with the contribution of developing a small-sized haptic device capable of on-desk operation, this study has several limitations. First, in this proposed unilateral teleoperation system, the operator cannot feel the reaction force generated from the slave device when it makes contact with an obstacle in the workspace. Therefore, bilateral teleoperation using force feedback will be incorporated in our future work. Second, position errors caused by pulley size was not considered when calculating the inverse kinematics of the CDPR. This can directly affect the positional accuracy since the size of the pulley is comparably large in a small-scale CDPR, which can be assumed as negligible in a large scale CDPR. Finally, if the proposed haptic CDPR is limited to a CDPR-specific  
Figure 11: Snapshot of the master–slave teleoperation system experiment.  
unique device, then further study to implement it in general-purposed haptic devices will need to be carried out. We would like to consider this effect in our future work.  
Conceptualization, C.-S.K. and E.-S.K.; investigation, E.C.; methodology, M.-C.K., J.-H.P., R.B., and S.A.G.; validation, [PERSON]-H.P., M.-C.K., and E.C.; system analysis--software, M.-C.K., R.B., and J.-H.P.; formal analysis, M.-C.K., S.A.G., and E.-S.K.; writing--draft preparation, [PERSON]-H.P. and M.-C.K.; writing--review and editing, C.-S.K.; supervision, C.-S.K.; funding acquisition, J.-O.P. All authors have read and agreed to the published version of the manuscript.  
This research was supported by a grant from the Korea Health Technology Development R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health and Welfare, Korea (grant number: HI19C0642).  
No institutional board review was necessary for this project.  
Data Availability Statement: Data sharing not applicable.  
The authors declare no conflict of interest.