DESIGN: ~ Electrotor-SloMo - Control - Electric

• The idea of a Torque-pitch coupling may be flawed. This is because if the blade experiences a downdraft, the induced drag will initially decrease. This will result in the blade advancing in the plane of rotation and this will cause the pitch to decrease. This may be a terminal flaw. Conversely, and updraft would have the same effect but in reverse, in that the pitch will increase. Any damping (delaying) of the pitch response will slow down the cyclic speed.
• Locating the pitch joint (CG) ahead of the center of the rotor disk may help.
• Locating the pitch axis in the blade slightly ahead of the chordwise aerodynamic center may help.
• The use of Free Tip (Aerodynamic Active Blade Twist) may negate this concern. This is because as the downdraft will initially result in a lower torque and thereby a reduced pitch at the root, this downdraft will cause a greater pitch at the tip ~ if the rotor has a 'free tip'.
• Increasing the electrical power to both halves of the motor will cause the rotor's RPM to increase, thereby increasing the thrust.
• The upper limit to pitch rotation is set by an elastomeric stop. Increasing the individual half-motor's torque will increase the pitch of that motor's blade.
• To tilt the rotor disk down at the front, the power will be increased on the half-motors when the are on the retreating side of the disk and decreased when they are on the advancing side.

• The future use of sensors, which would be integrated into the electronic control system, may very likely overcome any difficult flight control problems that initially arise.

• Each rotor has a pair of Pitch-torque coupling mechanisms. See; Electrotor-SloMo - Control Flight - Auto-Collective by Torque-Pitch and Auto-Collective Rotor Hub
• Autorotation: This is the default pitch setting of all six blades. Concern: What effect will different weight of the pilot etc have on the rotors' RPM and achieving the minimum descent rate? Could it be viable to use the regenerative ability of the controller to automatically slow rotors that are overspeeding?
• Collective: The throttle increases or decreased the torque and the pitch in all blades in unison.
• This means that the advancing and retreating blades on the same rotor must be interlocked so that they have the same pitch, even though they do not have the same angle of attack in horizontal flight.
• It may be viable to balance the torque of the two rotors by a pilot operated trim-wheel of automatically by sensors and/or gyros.
• Pitch: For forward pitch; the blades will experience a decrease in power (torque and pitch) when on the advancing side and an increase in power (torque and pitch) when on the retreating side. Conversely, the opposite will be true for a backward pitch.
• Roll: The same as the above pitch except the power requirement of the individual blades is moved 90º azimuth.
• Yaw:
• See; DESIGN ~ Electrotor-SloMo ~ Control Flight - Weight-Shift - Yaw ~ Method 3. This link is here because the yaw is achieved by electric control.

• The same as pitch except one rotor has its longitudinal pitch increased while the other rotor has its longitudinal pitch decreased.
• Consider the use of Blade Tip Cooling of Motor and a short term and the variable blockage of the tip exhausts on one of the two rotors.
• Sensor:
• Rotor Azimuth: There will be an azimuth sensor on both rotor hubs. Its output will be fed to the onboard ESC. See Group B [Absolute Encoder].
• Synchronization of Rotors: Increasing the power to one rotor while decreasing it to the other will allow the former rotor to catch up.
• Regeneration:
• Consider using regeneration to act as a brake on the rotors after landing.
• The pilot could set a switch before landing that will cause the system to go into regeneration mode upon the full release of the 'throttle' at landing.
• Alternatively, the function of braking (regeneration) might be operated by a separate momentary contact switch, which can only be activated when the throttle is fully off.
• The regeneration might also be used to charge up the capacitors.

• Braking:
• Postings on Rotary Wing by Karl;

• There is an electric motor in each rotor. The motors direct drive their rotorhubs. The motor's rotors are connected to the blades. The torque on the blade determines the blade pitch. To maintain a specific rotor rpm and thrust while pitching the blade forward. The torque would be increased on the blade near 270º azimuth while the torque was decreased on the blade near 90º azimuth.

• The intended rotation is outside forward. On the Intermeshing configuration the braking of the rotors will want to rotate the top aft about the lateral (Y) axis.
• This may not place a moment on the fuselage (back leg) because the gimbal is a bearing.
• This may not place a force on the back leg because the moments of the aero-rotors and the motors may be balanced about the Y-axis.
• This will place a forward acting force on the front legs (control arms).
• This may result in a large distance between the front and the back legs, giving greater stability upon touchdown.
• This may pull the legs out of the pilot's hands. ~ BAD.
• The risk of an inadvertent actuation of the brake may be worse than the risk of not having a brake.
• At this time ~ do not consider any means of braking the rotors other than that of electrical regeneration.

• Locate the Controller(s) low on the X-frames so as to locate the gimbal near the centers of mass, lift and drag, etc. This particularly relates to the Intermeshing configuration where the gimbal will be physically lower due to the proximity of the blades and hublettes.

• Consider the potential advantages (and disadvantages) of having a pair of separate + & - MOSFETs or IGBTs for each coil.
• This should allow the electrical removal of a single coil should it develop a short.
• This may also allow for switching between 3-phase and 4-phase; if the PMs are located properly and there is any reason to.
• They might be located in the large central area of the stator, at their respective coils

• Aerogel: ~ Used by Pascal

• There should probably be a slight capability for adjustment of the azimuth between the stator and its mount so that the 2 motors can be aligned with each other.

• Is there the possibility of static electricity discharge apron landing, which is done by the feet on the backpack.
• Potential Solutions:

1. The pilot wears rubber boots.
2. The frame trails a cable, which the pilot might trip on.
3. Insulated discharge cables that run from seat, which is part of the rear leg, or from battery holders, which are attached to the gimbal and pilot's harness, down to metallic pads on the bottom of both the pilot's insulated shoes.

• The current intention is;
  
  There will be a pair of totally separate electrical systems, in power source (batteries) and in conversion (motors). Either system will be able to provide the energy for a powered descent, should one system fail.
  
  In addition, at some point in an prolonged flight, the system will make the pilot aware that an automatic power reduction is about to start. It will then implement this power reduction, which will force a powered descent.
  
  When the craft is approaching the ground, under full-power or partial-power the pilot will 'unlock' the emergency power (capacitor). It will then be available to him for the touchdown.
  
  Also, before takeoff, the pilot will 'unlock' the emergency power for a short period of time.
• This is a blade that has no, or limited, autorotative capability. See; DESIGN ~ Electrotor-SloMo ~ Rotorhead - Blade-P - General

• Patent search on "Ultralight Helicopter"
• US 2,461,347 Helicopter Adapted To Be Attached To a Pilot
• US 5,370,341 Ultralight Helicopter and Control System
• 7,128,293 Helicopter
• 7,134,840 Rotor system for a remotely controlled aircraft November 14, 2006

• Patent search on "Ultralight Helicopter"
• Nothing of interest

• DESIGN: Electrotor-SloMo ~ Motor - Axial Flux - Miscellaneous - Blade Pitch Control
• Also look at AeroVantage -~ Control - Motor binder.

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