Abstract
The design of unmanned aircraft system (UAS) control stations was initially based on an aircraft cockpit. It was to make them familiar to the pilots of manned aircraft who were originally chosen to operate them. However, since a UAS pilot is not aboard the aircraft, all the information related to the system must be obtained visually with audible cues from various alerts. This research investigates the use of haptic feedback to provide additional sensory cues to improve performance and enhance safety. Giving the pilot information in other than visual methods will allow them to concentrate on piloting the UAS. Different methods of haptic feedback include force feedback to the controls, inputs to the pilot’s seat, wearables the give feedback such as helmets, gloves, vests, and other garments. Haptic feedback increases the spatial awareness of the pilot. It informs them of upcoming hazards that may include stalls, loss of control, in-flight malfunctions, excessive structural loading, and rates of climb or descent to keep the aircraft within its operating envelope.
Keywords: haptic feedback, unmanned aircraft system, safety, human-machine interface
Summary
Remote pilots of UAS face unique challenges in relation to control of the aircraft as they are not on board and, therefore, cannot experience the same forces acting upon the airframe (Fu, 2018). In addition, almost all the information related to the status of the aircraft must be obtained visually from the control station displays for remote pilots that operate UAS beyond the line of sight. With smaller UAS, the pilot must divide their attention between keeping the unit within sight and operating the controls, resulting in an increased workload. There are different technologies available to address these problems, not all are feasible depending on the size of the platform and control station, but haptic feedback has the possibility of increasing spatial awareness of the pilot as to the state of the aircraft and the forces it is experiencing (Rajappa, 2017). Introducing feedback into the control station allows the pilot a higher degree of situational awareness concerning the aircraft; the feedback can be in different formats, including resistance to movement, the vibration of a control or wearables on the pilot to alert of obstructions or other hazards. No longer will pilots be detached from the aircraft but will have the ability to be virtually linked as to what the airframe is experiencing and the ability to react quickly to changing conditions (Rajappa, 2017). The haptic feedback need not be relegated to warnings; it is also used to alert the pilot of conditions such as preset fuel quantity readings or other conditions by calling their attention to a particular display, not in the direct line of sight. Visual cues have the possibility of distracting the pilot; an alert displayed on a screen can cover up the camera feed resulting in a missed hazard or other traffic potentially putting the UAS in danger (Zhang S. &., 2018). Haptic feedback has the potential to make operating UAS safer while increasing efficiency. Miniaturization has allowed the development of wearables such as gloves to simulate touch or provide resistance, vests that indicate the direction of hazards, and modules placed into seats and controls such as stick shakers to alert the pilot of adverse conditions or operations outside of the flight envelope (Music, 2019). The feedback modifications can either be planned for the next generation or modified for existing control stations depending on their size.
Problem Statement
The operation of a UAS relies heavily upon the visual sense; this creates a problem when most of the information is acquired in this manner (Fu S. S., 2016). Critical alerts concerning the aircraft’s attitude can interfere with what the pilot sees as they can display over the video feed, causing the pilot to act and diverting attention away from flying the vehicle. Typically, the control station varies by manufacturer; the larger models tend to resemble aircraft cockpits as the operators originally drafted to fly them were pilots, so the controls were familiar. Problems are encountered when a pilot that is used to experiencing the various forces associated with flying an aircraft are absent. The added delay with a remote system’s teleoperation can cause the operator to overcorrect, operate the aircraft outside of its performance envelope, or not detect a hazardous condition that will result in the loss of the aircraft (Mouloua, 2020).
Throughout the history of modern UAS operations, human factors have played a large part in the incidents resulting from a lack of spatial awareness and their effect on the vehicle. The incidents rarely make the news as they typically occur in military or other government operations and are not sensational enough for the news media to broadcast. Because of their nature and how expensive a loss of a vehicle can be, sometimes in the millions of dollars, investigations do occur. In 2006 a General Atomics Predator B was lost by the Department of Homeland Security, which was directly attributable to human factors issues (Carrigan, n.d.). The use of automation does reduce the workload of pilots. Still, it can also hinder them, particularly with highly autonomous systems, as they may not recognize a danger or failure because of the remote nature of the pilot and the delays associated with teleoperation (Zhang, 2020).
Significance of the Problem
The pilot’s inability to experience the forces acting upon the aircraft can directly affect the inputs to the controls. The remote pilot does feel the forces of gravity pushing them into the seat, nor will they be able to judge their effect on the airframe through the video monitors (Zhang, 2020). Adding strain gauges to the aircraft can prompt a warning. Still, it may distract them by diverting their attention to read what it is; the other senses must be incorporated into the control scheme to increase safety. The integration of haptic feedback into the flight controls, displays, and the seat will afford the pilot a greater amount of detail as to the condition of the aircraft in the operating environment (Hace, 2019). Currently, there is no feedback into the controls of a UAS due to the nature of their design. In some cases, depending on the operator’s position, even if the control is identical, it can have a different function between pilot and payload operator (Carrigan, n.d.).
To counteract these deficiencies, the pilot must have a way of obtaining the information using the other senses, while not increasing the load on the visual aspect of piloting the aircraft. This may require the redesign of the control stations as the haptic feedback equipment will need to be incorporated into the design (Fellah, 2016). If a redesign is not feasible, then wearable technology can be integrated with minimal changes to the control station while still maintaining the same functions. Smaller portable control stations may not be adaptable to this type of technology, but at the rapid pace to which UAS technology is advancing, there may be a solution soon. Even small UAS pilots may be able to benefit from wearable technology, allowing them to concentrate on piloting the craft while still obtaining the necessary information to maintain stability or avoid hazards (Music, 2019). The problem is integrating the technology with existing platforms in a cost-effective manner. It must be affordable enough to warrant its inclusion as an extra safety precaution or by regulation because the value of such equipment has been demonstrated to the governing authorities.
A Brief History of Haptic Feedback
Haptic feedback is not a new concept; it was developed to allow operator feedback of teleoperated systems (Stone, 2000). It has since spread to other systems and vehicles, such as a stick shaker in an aircraft to warn the pilot of an impending stall. When a touchscreen vibrates at the push of a simulated button is also a form of haptic feedback. Haptic feedback in robotic systems attempted to correct a deficiency because of a lack of feedback. In some instances, like the manipulation of dangerous materials such as radioactive substances, it is crucial to give the operator a feel for the task as it is accomplished. The technology has progressed to the point where wearables are now available; gloves can simulate the sensation of touch in virtual systems, even providing resistance to give the impression of grasping an object (Zubrycki, 2017). The development of robotic surgery, where the doctor performs the operation, can be in another state relies heavily on haptic feedback to the operator. Although much more sensitive than what is needed for the operations of UAS, the principals are still the same (Neupert, 2016). Haptic feedback is an essential tool in the use of teleoperated machines that give the operator a feel for what the machine is experiencing; a UAS pilot will benefit from haptic feedback to alleviate the strain on using vision for a majority of the information. Studies have shown that even when operating a manned aircraft, the visual sense can be overloaded, causing a misinterpretation of the sensations and an incorrect action by the pilot (Zikmund, 2020). The study also learned that the pilot’s body could misinterpret haptic signals if they are not accustomed to them in training; furthermore, the most effective signal was to warn the pilot of a slip (Zikmund, 2020). The principles are proven, the technology has improved and miniaturized, and can be adapted to increase the safety of UAS. Haptic feedback is a promising technology for the operation of UAS, but it can also cause sensory overload and confusion of the pilot (Belcastro, 2017).
Flight Control Modifications
Ground control stations were initially designed to resemble an aircraft cockpit as the early pilots of these systems were re-tasked military aircraft pilots. It was theorized that familiar layouts would assist in the transition. The challenge is to modify the flight controls to provide information to the pilot in a way that reduces visual load but does not induce sensory overload. Traditionally, most of the haptic feedback systems have been reactionary, meaning they give a signal based upon the feedback from the controlled item or are designed to draw the attention of the pilot, research has suggested that active resistance to the control and processing the signals through a filter to reduce lag and overcorrection by the pilot (Fu, 2019).
Adding resistance to movement on a flight control can give the pilot the sensation of wind resistance over a control surface. The faster an aircraft flies, the more force is required to actuate the flight controls. Small electromagnets could be used to increase resistance to movement based on the airspeed of the vehicle. A small vibrating motor embedded into the control stick would suffice, for example, if the pilot is climbing at to step of an angle of attack and were approaching a stall, the control would vibrate. Small haptic generators can be placed on the control so that only specific zones of the hand can be stimulated corresponding to a predetermined signal (Wang, 2019). The same could be done to the throttle control; if the aircraft is supposed to be in takeoff configuration and the flaps are not extended to the proper angle, then the throttle control will vibrate, and an aural warning could be given as well (Hace, 2019). There are problems when the control does not have the physical capability to be modified; smaller control stations may not be able to implement this type of technology within the device. Unlike aircraft which have a standardized layout on the controls, there is no standard with UAS control stations. With many different manufacturers, it will most likely take either an industry agreement or governing authority to accomplish standardization (Hobbs, 2015). The addition of wearable haptic devices such as gloves and vests that give feedback to the pilot is the solution to control stations that cannot be modified. But these wearables must not be cumbersome, nor must they interfere with the pilot’s ability to operate the aircraft.
Wearables
Haptic feedback has been proven to work in manned aircraft, stick shakers warn of an impending stall, and the pusher will attempt to put the nose down. The theories and techniques are verified; they just need to be miniaturized to work on UAS platforms. Existing sensor data is utilized so that feedback occurs when a specific range is exceeded by the vehicle or pilot. But for platforms that are mature in their development, ground control stations may not be easily upgradable. In that case, the pilot may wear accessories that warn them of problems such as small vibrating motors to give them warnings. Wearables have the potential to supplement the visual cues given off by the system without significant upgrades to the control station but still allowing enhanced sensory input to the pilot.
As mentioned previously, gloves can be worn by the pilot and feedback given for certain actions or conditions of the aircraft; in addition, a vibrating garment can be worn as well. The pilot could also wear belts or vests, and the haptic feedback could set as a signal to the pilot concerning the status of the aircraft (Socha, 2017). The use of haptics is intended primarily to get the attention of the pilot relating to a condition or status of the aircraft; their use must also be selective. Placing too many vibratory signals close together can cause confusion in the pilot and a misinterpretation of the warnings leading to sensory overload. One study showed that pilots moved a modified joystick in the correct direction based on signals from vibratory motors placed on four different points on the control. The error rate slightly increased with an additional motor designed to induce interference (Socha, 2017). There is some concern as to how the pilot positions their hand on the control so the signal may not be interpreted correctly; this can be overcome with the use of a glove, negating the need for precise had positioning. Small vibratory motors can be sewn into the glove, and the pilot will not need to be in contact with the control to receive the feedback. In addition to the wearables or instead of them, the pilot’s seat could also contain haptic feedback devices. An indication could be given when the vehicle has touched down successfully tied to a weight on wheels indicator. Gloves can be worn that provide resistance to certain actions of the operator; jamming devices have been integrated into the finger joints to restrict the movement of the operators (Zubrycki, 2017). These devices can give the pilot the sensation of interacting with virtual controls, although their complexity and the resources required to use them may prevent their adoption on UAS platforms.
There are some problems with wearables, the sensitivity to the haptic signal depends on the wearer, and how much other clothing they have on (Fellah, 2019). The frequency and direction of the signal are also crucial to proper interpretation by the pilot; feedback along a vertical axis is harder to determine that along a horizontal axis. For example, the vest worn by the research subjects that Fellah conducted has rows of small vibrating motors along the sides, front, and back, a signal generated by more than one motor on the same horizontal plane was easier to differentiate than those that were sensed with vertical separation (Fellah, 2019). The use of wearables must also not interfere with the comfort of the operator. If they are distracted, they will not be able to effectively interpret the signals from the devices or reject wearing the devices as they hinder the operation of the aircraft. Because of the possibility to impact operations, the wearables should take a minimalist approach to be able to integrate with existing equipment
Spatial Awareness
The teleoperation of a UAS can be quite complicated since the pilot is not within the aircraft. Spatial awareness is reduced, and the pilot can only view the surroundings through the camera view or from the ground. Increasing the awareness of the remote pilot concerning the aircraft and its surroundings results in safer operations. Sometimes a UAS will need to be operated near obstructions that could damage it, such as in a disaster situation doing search and rescue. To aid the pilot, research has been conducted where pilots operated a UAS within a simulation, and a “force field” around the vehicle was simulated and presented on the display (Ho, 2017). The research combined haptic feedback and augmented it with a visual representation of the vehicle’s danger zone. Researchers found that although performance was not appreciably increased, the study participants responded that the visual cues from the system reduced confusion of the haptic feedback and allowed the pilot to better interpret the feedback signals (Ho, 2017). Another method of generating haptic feedback uses a virtual simulation of a teleoperated robot is experiencing, this is particularly useful for increased latency as it acts as a filter smoothing out the operators commands (Valenzuela-Urrutia, 2019). This type of set up may not be entirely feasible in long-distance UAS operations. Within a building or other enclosed structure where a signal can quickly degrade because of interference, it can assist the operators of the smaller units. This type of interface may require a high level of autonomy for the UAS to operate properly.
Although the focus of this research centers on haptic feedback, for UAS operations, research has begun into the addition of augmented reality (AR) to haptic feedback, which can add an additional layer of sensory information, although it is still received visually (Safi, 2019). The operator can wear a set of special glasses that project the information on to the lens while allowing the operator to see through them. As a small UAS gets further away from the operator in line of sight operations, the operator must divert their attention to the control station to maintain proper control. A recent experiment into remote sensing of radioactive materials using a small UAS discovered that participants in the experiment experienced a lower mental stress level when combining augmented reality and haptic feedback into the control scheme (Aleotti, 2017) This may reduce the need to continually scan the displays and only have an alert illuminate when a parameter exceeds the limits by giving a cue in the field of vision such as a translucent red square with a one-word indicator for the warning. Essentially a heads-up display (HUD) worn by the pilot. This may not be necessary on the larger ground control stations but could be beneficial to small UAS that operate within visual range or within a limited distance outside of visual contact with the remote pilot. This will reduce the need to look at a separate telemetry reading while piloting the aircraft, so their focus remains on the operations of the UAS. For this concept to succeed, a standardization adopted by the UAS and control station manufacturers will need to be adopted as currently there is none as they resemble computer stations rather than cockpits (Hobbs, 2015). This
Information Overload
One of the significant concerns that must be addressed when implementing haptic feedback into a human-machine interface (HMI) is the effect it will have on the receiving of that information by the operator. The operation of a UAS requires the use of visual sense to acquire a majority of the information; adding haptics can assist in reducing that workload, but it can also have the opposite effect and cause a condition known as information overload. The condition of information overload is hard to define because they are subjective, and what may exceed the limits of one person can be handled by another. The most recent definition is that an individual will receive so much relevant information that it interferes with the decision-making process and slows it down (Bawden, 2020). The speed at which decisions are made in the aviation environment is critical to safe operation of the aircraft; anything the contributes to latency in the process must be minimized. Haptic feedback could cause sensory overload by diverting the pilot’s attention away from controlling the aircraft at critical phases of flight. In addition to the problem with too much information, age is also a factor with overload but for different reasons. The older a person is, the less they may be able to deal with advanced technology, and the rapidity the information is presented to them (Benselin, 2016). This is a factor that must be figured into any design that is integrated into control stations. The more automation a UAS has, the less direct control the pilot has over the aircraft’s functions (Sherwood, 2018). With highly automated aircraft, a cascade event can trigger multiple alerts; if those alerts are delivered through haptic means, they can overlap and cause confusion for the operator. Although Fellah’s research dealt with wearable haptic technology, too many outputs built into the controls can also deliver sensory overload; therefore, the amount of feedback from each control should be limited (Zikmund, 2020).
Limitations
Haptics are beneficial to getting the attention of pilots to alert them of conditions requiring their attention. The most benefit from the system is that their use must also be limited to conditions that may directly affect the safe operation of the aircraft or alert the pilot to an alert requiring immediate attention. The current generation of control stations may be able to be modified without increasing their size or complexity; this may require the addition of new technologies such as the wearables which may hinder the pilot’s effectiveness if too many devices are worn. Their use must be balanced against the intended use of the UAS. For example, a smaller commercial unit that operates within the line of sight of the operator may not have the capabilities to use haptics as their payload capacity or control station may not be capable of supporting the extra equipment. In contrast, larger standalone control stations for long-endurance aircraft would enhance the awareness of the pilot.
Furthermore, a standard control scheme must be adopted along with signal requirements, with new UAS manufacturers entering the field, this could slow development and increase costs. The haptics may not respond as desired, particularly with the integration of UAS into the national airspace. Sense and avoid technology will need to give the appropriate feedback to the operator, which will have to be a different signal scheme than an aircraft condition warning. If the UAS is operating in controlled airspace, the feedback signals could overwhelm the pilot, causing the alerts to be either ignored or disabled by the operators as a hindrance. The use of haptics is meant to enhance situational awareness of the aircraft, not overwhelm the pilot to the point the information is viewed as cumbersome and a nuisance. Further research is required as to the best placement of the haptic devices. If they are too close together, the signals may be misinterpreted or hard to distinguish based on location (Fellah, 2019).
Recommendations
The use of haptic devices has been proven to increase the spatial awareness of pilots of manned aircraft. The problem is modifying them to suit the needs of the remote pilots. For example, stick shakers and pushers may not be needed on the more advanced UAS, but the control station can have vibrating flight controls when limits are exceeded to warn the pilot of impending stalls. Wearables can also achieve the same effect, but the system must be able to generate the proper outputs to the gear to accommodate them. Wich requires that aftermarket equipment conforms to a standard protocol. Manufacturers must adopt a single signal scheme so that the equipment will be able to process the inputs from the equipment; this may require action through the governing authority or an agreement between producers of the equipment.
Operators of smaller UAS may not have as many options as the larger-scale vehicles, and their control stations may not be compatible with the technology. For this purpose, Bluetooth technology can be utilized, but this would require the establishment of parameters by the operator before the flight begins to set the limits of the UAS. The vehicle’s telemetry must be capable of transmitting the required data back to the control station so that it can be utilized with the wearable haptic technology.
Conclusion
The development of UAS control stations has been a haphazard process where there is no standardization across platforms, with the only similarity being that they have attempted to resemble an aircraft cockpit. This has caused a multitude of human factors issues and research on how to improve the HMI. Haptic feedback is one method that can be utilized, but it is not a universal solution, the implementation of this technology must not degrade the operator’s performance. Instead, it should alleviate the strain on the visual sense while only alerting the pilot to situations or an aircraft condition that may put it in danger. The manufactures should also adopt standards to enable the implementation of haptic technology across all sizes of platforms and control stations voluntarily. Doing so will improve the safety of UAS operations in both military and commercial platforms.
References
Aleotti, J. M. (2017). Detection of nuclear sources by UAV teleoperation using a visuo-haptic augmented reality interface. Sensors. doi:10.3390/s17102234
Bawden, D. & Robinson, L. (2020). Information Overload: An Overview. Retrieved from City, University of London Institutional Repository: https:// openaccess.city.ac.uk /id/eprint /23544/
Belcastro, C. M., Newman, R. L., Evans, J., Klyde, D. H., Barr, L. C., & Ancel, E (2017). Hazards identification and analysis for unmanned aircraft system operations. 17th AIAA Aviation Technology, Integration, and Operations Conference. Denver: AIAA. doi:10.2514/6.2017-3269
Benselin, J. C., Ragsdell, G. (2016). Information overload: The difference that age makes. Journal of Librarianship and Information Science, 284-297. doi:https://doi.org/10.1177/ 0961000614566341
Carrigan, G. L. (n.d.). Human Factors Analysis of Predator B Crash . Retrieved from http://halab.mit.edu: https:// hal.pratt.duke.edu/ sites/hal.pratt.duke.edu/ files/u13/Human%20Factors%20Analysis%20of%20Predator%20B%20Crash%20.pdf
Fellah, K., Guiatni, M., Ournid, A. K., & Boulahlib, M. A (2016). Fuzzy-PID side-stick force control for flight simulation. The Aeronautical Journal, 845-872. doi:10.1017/ aer.2016.34
Fellah, K., & Guiatni, M. (2019). Tactile display design for flight envelope protection and situational awareness. IEEE Transactions on Haptics, 87-98. doi:10.1109/ TOH.2018.2865302
Fu, S., Saeidi, H., Huang, J., Wang, Y., & Wagner, J. (2018). Customizable unmanned aerial vehicle haptic feedback interface: Theory and test. Journal of Guidance, Control, and Dynamics, 2581-2587. doi:10.2514/1.G003645
Fu, W., van Paassen, M. M., & Mulder, M. (2019). Developing active manipulators in aircraft flight control. Journal of Guidance, Control, and Dynamics: Devoted to the Technology of Dynamics and Control, 42(8), 1755-1767. doi:10.2514/1.G004186
Hace, A. (2019). The advanced control approach based on SMC design for the high-fidelity haptic power lever of a small hybrid electric aircraft. Energies, 12(15). doi:10.3390/en12152974
Ho, V., Borst, C., van Paassen, R., & Mulder, M. (2017). Visualizing force fields increases acceptance of haptic feedback in UAV teleoperation. In Proc. of the 19th International Symposium on Aviation Psychology (ISAP). Dayton. doi:https:// pure.tudelft.nl/ portal/files/35661540/ISAP2017_VictorHo.pdf
Hobbs, A., & Lyall, B. (2015). Human factors guidelines for unmanned aircraft ground contorl stations. San Jose: National Aeronautics and Space Administration. Retrieved from NASA Human Systems Integration Division: https://hsi.arc.nasa.gov /publications /GCS_HF%20_Prelim_Guidelines_Hobbs_Lyall.pdf
Mouloua, M., Ferraro, J. C., Kaplan, A. D., Mangos, P., & A. Hancock, P. (2020). Human factors issues regarding automation trust in UAS operation, selection, and training. In Human Performance in Automated and Autonomous Systems, (pp. 166-190). Boca Raton: CRC Press. doi:doi:10.1201/9780429458330-9
Music, S., Salvietti, G., Dohmann, P. B. g., Chinello, F., Prattichizzo, D., & Hirche, S. (2019). Human-robot team interaction through wearable haptics for cooperative manipulation. IEEE Transactions on Haptics, 12(3), 350-362. doi:10.1109/TOH.2019.2921565
Neupert, C., Matich, S., Scherping, N., Kupnik, M., Werthschutzky, R., & Hatzfeld, C. (2016). Pseudo-haptic feedback in teleoperation. IEEE Transactions on Haptics, 9(3), 397-408. doi:10.1109/TOH.2016.2557331
Rajappa, S., Bülthoff, H., & Stegagno, P. (2017). Design and implementation of a novel architecture for physical human-UAV interaction. The International Journal of Robotics Research, 800-819. doi:10.1177/0278364917708038
Safi, M., Chung, J., & Pradhan, P. (2019). Review of augmented reality in aerospace industry. Aircraft Engineering and Aerospace Technology, 1187-1194. doi:10.1108/AEAT-09-2018-0241
Sherwood, S. M. (2018). The effect of task load, automation reliability, and environment complexity on UAV supervisory control performance. Retrieved from Embry-Riddle Aeronautical University Scholarly Commons: https:// commons.erau.edu/ cgi/viewcontent.cgi?article=1433&context=edt
Socha, V., Hanáková, L., & Lalis, A. (Eds.) (2017). New trends in civil aviation : Proceedings of the 19th international conference on new trends in civil aviation 2017. Prague, Czech Republic: Taylor & Francis Group. Retrieved from https:// ebookcentral. proquest.com/ lib/erau/detail.action?docID=5436361
Stone, R. J. (2000). Haptic feedback: A brief history from telepresence to virtual reality. International Workshop on Haptic Human-Computer Interaction, 1-16. doi:https:// doi.org/10.1007/3-540-44589-7_1
Valenzuela-Urrutia, D., Muñoz-Riffo, R., & Ruiz-del-Solar, J. (2019). Virtual reality-based time-delayed haptic teleoperation using point cloud data. Journal of Intelligent & Robotic Systems, 96(3), 387-400. doi:10.1007/s10846-019-00988-1
Wang, D., Li, T., Afzal, N., Zhang, J., & Zhang, Y. (2019). Haptics-mediated approaches for enhancing sustained attention: Framework and challenges. Science China Information Sciences, 1-26. doi:10.1007/s11432-018-9931-1
Zhang, D., Yang, G., & Khurshid, R. P. (2020). Haptic teleoperation of UAVs through control barrier functions. IEEE Transactions on Haptics, 109-115. doi:10.1109 /TOH.2020 .2966485
Zhang, S., & Dai, S. (2018). Workspace analysis for haptic feedback manipulator in virtual cockpit system. Virtual Reality, 321-338. doi:10.1007/s10055-017-0327-y
Zikmund, P., Horpatzká, M. v. c., Dubnický, L., Macík, M., & Jebáček, I. (2020). Pilot-aircraft haptic feedback tests. Aircraft Engineering and Aerospace Technology, ahead-of-print(ahead-of-print), 10.1108/AEAT-12-2019-0265.
Zubrycki, I. Z. (2017). Novel haptic device using jamming principle for providing kinaesthetic feedback in glove-based control interface. Journal of Intelligent & Robotic Systems, 413-429. doi:10.1007/s10846-016-0392-6
tem Pilots
Patrick Carroll 