## 5 Conclusions  
Overall, this study shows that it is generally possible to adapt control elements to different modalities in VR and optimize operation. Factors that have a significant impact on user experience, presence, and perceived workload when operating control elements in VR were identified. The results showed that rotary controls in VR should have a resolution of 10-15\({}^{\circ}\)/value, a diameter of 33-45 mm, and knurling. Haptic feedback in the form of vibration pulses and acoustic feedback in the form of clicks should be implemented. Joysticks in VR should have a maximum rate of change of 11 values/s, a maximum deflection of \(\pm\)10-17\({}^{\circ}\), a length of 240 mm, and a diameter of 43 mm. The feedback when operating joysticks in VR should be acoustic.  
With VR-adapted control elements, prototypes of machines and devices can be better tested by users in VR by minimizing distortion due to the altered modalities in VR. Possible applications include cranes, drilling rigs, agricultural machines, or medical devices. In these tests, the usability of the new product as well as initial user evaluations can be examined without the need to manufacture real prototypes or control elements. It can be examined whether the selection of control elements and their layout are suitable for the work tasks. These completely virtual tests should be followed by tests in mixed-reality environments in which the selected control elements can be operated as realistically as possible. Overall, this approach could improve the development process, reduce manufacturing costs, and optimize the HMIs of products.  
How well control elements can be operated in VR depends strongly on the type of interaction. In this study, VR controllers were used to interact with the virtual joysticks and rotary controls. Currently, more and more interaction types based on hand and eye tracking are entering the market. Data gloves, some of which provide force feedback, are also being developed further. This study shows that haptic feedback in the form of vibration pulses significantly improves the operation of rotary controllers in VR. Therefore, VR controllersor data gloves should be used for user testing of prototypes in VR. Especially, the possibility of force feedback could make the interaction with VR prototypes even more realistic. The influence of the use of data gloves and force feedback on the factors investigated in this study, e.g., user experience, needs to be investigated in further studies.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app13158668/s1](https://www.mdpi.com/article/10.3390/app13158668/s1)]([https://www.mdpi.com/article/10.3390/app13158668/s1](https://www.mdpi.com/article/10.3390/app13158668/s1)), Figure S1: VR controllers examined; Table S1: Test design rotary control; Table S2: Test design joystick.  
[PERSON] and [PERSON] carried out the experiment. [PERSON] wrote the manuscript with support from [PERSON] and [PERSON]. [PERSON] conceived the original idea. [PERSON] supervised the project. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The work presented does not include any studies on humans or animals. Due to the study design, no formal vote of an ethics committee was required. The VR experiments performed do not result in any hazards that increase the general risk to life of the persons concerned. All participants gave their informed consent for inclusion before they participated in the study.  
Informed Consent Statement: Informed consent was obtained from all participants involved in the study.  
The raw data supporting the conclusion of this article will be made available by the authors without undue reservation.  
The authors declare no conflict of interest.  
References