Designed for the highly coupled throttle and yaw channels of the helicopter, the Gyro / Gov is a high performance Heading Hold Gyro and Rotor Speed Governor in a single package.  It was designed from the ground up with the full dynamics of the helicopter in mind and exploits the relationship between the throttle and yaw channels to improve upon both rotor speed and yaw stabilization control, while offering capabilities not possible with two independent devices.  Programming is performed using a detachable LCD and 4-direction joystick to navigate through the highly intuitive hierarchical menus, with all setup parameters stored for up to 8 models.  The Gyro / Gov is also universally compatible with all governor sensor types and throttle / rudder servo types, so once setup, swapping between 8 models with different governor sensor types, servo types, gear ratios, sign conventions, travel limits, flight mode settings, governor enable criteria, gains, etc... is done by simply loading that model's name into memory.  The Gyro / Gov also tracks the total engine run-time on each of 8 models for help with scheduled maintenance... designed to support the entire fleet.

Heading-Hold / Yaw Stabilization Control
 

Rotor speed control options include Governor & Limiter modes as well as an electronic Correlator which can be independently enabled.  Governor mode regulates rotor speed at the target RPM associated with each flight mode, Limiter mode ensures that a target RPM is not exceeded while utilizing the Tx-based throttle curves otherwise, and the electronic Correlator feeds-forward the predicted throttle position from your Tx-based throttle curves while either the Governor or Limiter are active adding anticipatory action to the rotor speed control.  The particular control type is associated with each flight mode (i.e. Normal, Idle-Up1 & Idle-Up2) and the control is activated by either Stick, Switch, or a Stick/Switch combination.  Stick activation utilizes a dual threshold criteria allowing a de-activation threshold lower than the activation threshold if desired, reducing the chance of an unintended disengagement. 

All-Digital Pre-Calibrated Control Set
 

All Gyro/Gov parameters are entered in a purely digital pre-calibrated format.  For example, maximum pirouette rates for each flight mode are entered in degrees per second and target rotor speeds are entered in RPM.  Gear ratios are entered digitally to the hundredths place, i.e. 8.18, etc... although this parameter is pre-populated with the default value from many common helicopter models selectable during setup for user-friendly programming.  At no point is the pilot required to use Tx endpoint adjusts with look-up tables to estimate RPM or pirouette rates during programming.  In this way, a max pirouette rate of 360 deg/s will command a piro rate of precisely 1 revolution per second when the rudder is fully deflected... a max pirouette rate of 720 deg/s will command a 2 rev/s piro rate... a max pirouette rate of 1440 deg/s will command a 4 rev/s piro rate, etc... 

Flight Mode Customization
 

So, in this example, Normal Mode sets base gyro & governor gains for a "Camera Ship" flying style while running a head speed of 1500 rpm with a max pirouette rate of 1 rev per second.  Idle-Up 1 sets base gyro & governor gains for a "3-D" flying style while regulating 1800 rpm utilizing throttle feed-forward (e Correlator enabled) with a max pirouette rate of 4 rev/s, etc... Although not shown in this table, the individual gains of the Gyro & Governor controllers can also be modified independently from their Flying Style base gains for each flight mode if desired for an even greater degree of customization.

By setting the "Tx Gain Function", the Gyro/Gov can be configured to use the receiver's "gain" channel for either in-flight gyro gain adjusts or in-flight governor RPM bias adjusts.  If setup for Gyro Gain adjusts, the Gyro base gains can be modified remotely from the transmitter.  Furthermore, if the "Gyro Gain Mode" is set to "H-Hold/Normal", the upper [0,100] gain values specify Heading-Hold mode while the lower [0,100] gain values specify Normal mode.  With "Gyro Gain Mode" set to "Normal Only" or "H-Hold Only", the gyro mode stays fixed regardless of what side the gain value is set on.  With the "Tx Gain Function" configured to "RPM Bias", the transmitter's "gain" value is now used as an RPM bias, where the upper [0,100] will increase the target RPM from 0-100 and the lower [0,100] will decrease RPM from 0-100.  For example, if your Gyro/Gov has Flight Mode "Idle-Up 1" programmed for 1800 rpm, and the "Tx Gain Function" is set to "RPM Bias", a transmitter gain value of 0 will have no effect; an upper transmitter gain value of 25 will command 1825 rpm; a lower transmitter gain value of 50 will command 1750 rpm, etc...  In this way, the gain channel can be used for either Gyro Gain or RPM Bias as desired.   

Compact Design
 

New users of the Gyro/Gov will be pleasantly surprised at how well their radio trays "clean up" after realizing that all that is now required is the Gyro/Gov, receiver, and battery.  The gyro sensor is housed within the electronics package, eliminating the need for mounting a separate gyro on an umbilical cable, as yaw rate is constant at all points on the helicopter, whether at the CG or out at the nose.  The Gyro/Gov also saves on battery life using only one processor for both Gyro and Governor functions, and limits the current intensive LCD power to programming or data review only.

LCD Programming Interface
 

Glitch-Proof Setup
 

One of the most critical steps in the setup of any Gyro or Governor system is that of setting the sign convention for the controllers.  With Gyros this is usually ensured by manually twitching the sensor and monitoring the reaction of the tail rotor pitch to try to determine if the sign is correct.  With Governors there is sometimes no way to determine sign convention but through trial and error.  Additionally, setting the servo travel limits is extremely important so as to make use of the full range of motion and to prevent binding.  The Gyro / Gov has a setup utility called "Tx Model Calibration" which is used to set travel limits and sign conventions for both the Gyro and Governor functions by simply prompting the user to move the throttle and rudder sticks to their extents in sequence.  For example, "Throttle to Max" is displayed, then "Throttle to Min", next is "Rudder to Right" followed by "Rudder to Left".  Once this is done, sign conventions and travel limits are established removing all guess-work from this process.  Stick calibration results are displayed for verification, and in the event you have forgotten to perform the Tx model calibration for the active model & gyro sign convention has not yet been established, the Gyro/Gov will actually inhibit takeoff preventing a possible mishap since it has control of the throttle as well.  Governor enable logic (by switch and/or stick) can also be verified before flight with a setup screen that lets you test your setup as you manipulate the stick and/or switch.

System Stats
 

Within the "System Stats" submenu, one can view rotor control statistics for each flight mode including max rpm, average rpm, and rpm standard deviation throughout the entire flight.  The position of the flight mode switch determines which statistic is shown on the LCD, with the designations (N), (1), or (2) used to further clarify whether the Normal, Idle-Up1, or Idle-Up2 mode statistics are being shown.  A unique "Time on Engine" display provides the total engine run-time for the active model loaded into memory.  This display can be used to perform scheduled maintenance on your engine, and the time can be re-set when that maintenance has been performed to start the timer from zero again.  The Gyro/Gov also monitors the maximum yaw rate achieved in each flight mode, which is also presented in the "System Stats" submenu.  This is useful to make sure your model is actually physically capable of achieving the digital yaw rates you are commanding. 

The Gyro/Gov was specifically designed to work with all governor sensor types and all servo types for maximum flexibility.  Thus if you have already installed a governor sensor and your favorite servos on a particular machine and would like to purchase a Gyro/Gov for use on this helicopter, you do not have to change a thing on your existing setup.  Simply configure the Gyro/Gov to match your throttle and rudder servo types and your model's governor sensor type.  Taking advantage of the "Model Utilities" feature, the universal compatibility allows you to swap a single Gyro/Gov between up to 8 models with completely different servo types and/or governor sensor types by simply loading that model's name into memory.  So, for example, one model might be equipped with an analog hall-effect governor sensor type, digital rudder servo with super-narrow pulse-width capability, and an analog throttle servo, while another model is equipped with a digital optical governor sensor using digital throttle and rudder servos each with super-narrow pulse-width capability, etc... Once setup, the Gyro/Gov can be swapped between these models by just loading the custom model name into memory.  The Gyro/Gov is then automatically configured to work with that model.  

The task of the governor is to maintain rotor speed in an inertial (non-rotating) reference frame, i.e. with respect to fixed ground.  With a fuselage mounted governor sensor, measurements are actually taken from a rotating coordinate frame and represent rotor speed relative to the helicopter's pirouette rate.  The Gyro/Gov can correct these RPM measurement errors with gyroscopic feedback and knowledge of the active helicopter model's gear ratio and provide the governor controller measurements in an inertial frame of reference if this feature is enabled, providing more consistent rotor speed control through high pirouette rate maneuvers.

Gyro Gain Adapt with RPM
 

The Gyro / Gov uses inertial rotor speed feedback within the Heading-Hold / Yaw Stabilization control to automatically adapt the gyro gain with rotor speed changes to hold a consistent yaw loop gain, and hence consistent general flight handling qualities, in the presence of possible rotor speed droops, over-speeds, or pilot selected RPM changes.  The necessity of this feature is due to the fact that the main and tail rotors of the helicopter are mechanically linked, driven by a common gear mechanism, and tail rotor thrust (and hence yaw gain) varies with the square of tail rotor speed.  Thus any changes in main rotor RPM have a direct impact on yaw gain.  In order to compensate for these yaw gain variations with main rotor speed, the gyro gain is adjusted on-the-fly to cancel these nonlinear variations within the hybrid controller providing a constant yaw loop gain and more consistent feel to the remote pilot.  This technique is of particular usefulness to the average model helicopter pilot that changes rotor speed RPM selections frequently within the course of a given flight, and does not wish to spend the time re-tuning the yaw controller gain with each new main rotor RPM setting.

Control Mixing Terms
 

The Gyro/Gov utilizes "throttle to rudder" and "rudder to throttle" control mixing to reduce the off-axis vertical to yaw and yaw to vertical coupling that occurs with changes in throttle and/or tail rotor pitch commands respectively.  The throttle to rudder control mixing applies a corrective tail rotor pitch angle change with changes in throttle, which compensates for the anti-torque requirement changes with throttle (and proportional collective pitch) changes, sending a feed-forward correction to the tail rotor before a yaw rate error is even sensed by the Gyro/Gov's Heading-Hold function.  The rudder to throttle control mixing applies a corrective throttle change with changes in tail rotor pitch, to address the torque requirement changes by the engine with yaw rate, sending a feed-forward correction to the throttle before a rotor speed error is even sensed by the Gyro/Gov’s governor function.  Although many transmitters provide control mixing functionality, such as collective to rudder or throttle to rudder mixing, etc..., they apply mixing at the command level, rather than the actuator level, which is interpreted by their respective controllers as an unintended change in command.  The Gyro/Gov, however, provides control mixing terms that leave the commands intact, and alter only the final outputs to the servo actuators.