HMI Injury Risk and SMART/Adaptive Control

There are a number considerations that need to be addressed with regard to possible injury that could result from the poor design of human-machine interface airframes. Mechanical  design is critical not only for the sound integrity of any mechanical frame, but also critical when considering the mechanical span of motion in relation to the human span of motion. With regard to human machine interface, the ideal human control axiom is to have both machine and human ranges of motion function together at equal moments.
Any failure in the mechanical range of motion can cause the improper or over extension in the human span of motion and result in injury or prove fatal to the pilot. Problems that develop in ground based machines are affected by the forces of physics and can result in injury and mechanical failure. The same problems in an HMI airframe are also affected by physics in the same manner, but the issues are compounded because the HMI airframe is at altitude. Any injury, even minor, can prevent pilot recovery control input, resulting in fatal descent of the aircraft.

The Human Interface Rotor System is only a “motion” physical-interface system in its current configuration. The weight of the pilot is in balance with the rest of the upper airframe aft and distributed between the two airframes. The goal is to combine haptic and physical interface with a computer system that assists with pilot control. The HIR rotor system can then become an intelligent control system. The informational system can be programmed  to assist pilot input in the form of servo, hydraulic or pneumatic manipulation of control linkages. Regardless of the control measures used, injury may still result if poor design is implemented during fabrication. The pilot moves with the rotor system. There is interaction between the pilot and the two airframes that move with and around the pilot. Consideration should be given to points between the two airframes that could bind any part of the body between moving portions causing injury.

HMI RISKS AND PROPOSED SOLUTIONS
- Risk: Poor ergonomic design with regard to spans of motion between both machine and human extremities. This may cause joint over extension and muscular / tendon strains and tears.
Proposed Solution: static stops between moving components of machine parts and machine frames that will prevent over extension of machine spans of motion and in turn  prevent over extension in human ranges of motion.
- Risk: Flight control over correction or failing to manipulate controls due to a delay in “response to motion” during mechanical morphing of the airframe when at altitude. The complexity of learning the skills of correct responses during HMI operation in conjunction with piloting skills may cause mental strain. How will the natural human response affect the airframe and flight characteristics? Will the pilot be more prone to human error? Mastering piloting skills can cause enough strain. Will the sensation that the pilot feels, as he/she moves slightly with the rotor system, cause over correction of flight control inputs or hesitation of needed reflexes for proper control responses,…. .i.e. reacting too little or not at all? Pilots are familiar with what they feel when flying or learning to fly helicopters with static airframes. The unusual feeling that may be associated with HMI mechanical morphing of airframes in conjunction with all that physics impart to the body during flight may be more than the human mind can process and react to in a timely manner for safe flight. Simulation and testing will tell.
- Proposed Solution: Aside from a great deal of testing, a different approach to informational software for flight simulation will be required. Perhaps even a complete paradigm shift. Any design for a simulator will need to be from the ground up for both mechanical hardware and informational control software. Simulator airframes must function in the exact same manner as the intended flying prototype, to include the moving pilot seat. Traditional helicopter simulators will not provide valid training platforms because it is nothing more than a “box“ on a gimbal utilizing hydraulics and pneumatics to control the “box attitude“ to simulate flight.
Flight controls need to be designed and tested to function correctly to be certain that there are no unwanted control changes during mechanical morphing. With regard to the HIR rotor system, the collective pitch stick is positioned at 40 to 45 degrees rather than vertical. This should prevent unwanted collective pitch change as the upper airframe tilts forward/aft, but it has not been tested. Fly-by-wire may need to be incorporated.
* The end state should be a rotorcraft that utilizes a rotor system and airframe that together form  an intelligent mechanical system. It will combine physical-haptic interface and assisted control in the form of an informational system that predicts human response and assists, but does not take total control. One key goal would be detect unwanted human response in flight controls due to pilot error or a response due to a medical emergency that develops in the health of the pilot. Similar to a form of “guided auto pilot”. Step outside the box for a bit and view it as if you were a child and learning to ride a bicycle again. One of our parents would run along behind us with one hand on the bicycle seat “assisting” or applying lateral “input” to keep us up right in the desired position for riding a bicycle until we internalize the balance required to master it. Rather than a bicycle, we have a helicopter. Instead of one of our parents, we have an informational system programmed to “keep one hand on the seat” and assist when needed to keep the aircraft in the most optimal flight configuration.
A rotorcraft that incorporates this type of Human Adaptive Mechatronics could then be a more efficient aircraft.
-Risk: High Force Input. There are concerns about the physics involved with rotorcraft and the forces that will affect any airframe, let alone an HMI airframe. Will the forces affecting the helicopter develop moments requiring high force control input which could also cause injury or undue strain on the human body as well as the control linkages? This concern is associated with smaller helicopters, but may affect larger aircraft as well.
-Proposed Solution:  With larger rotorcraft, hydraulic assisted control linkages are standard. For smaller rotorcraft the  use of hydraulics has not been an option until recently. Now there is a small self contained hydraulic unit that is light weight. It contains a small internal electric hydraulic pump incased within the cylinder.