Patent Publication Number: US-11661191-B2

Title: UAV configurations and battery augmentation for UAV internal combustion engines, and associated systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 16/559,420, entitled “UAV CONFIGURATIONS AND BATTERY AUGMENTATION FOR UAV INTERNAL COMBUSTION ENGINES, AND ASSOCIATED SYSTEMS AND METHODS,” filed on Sep. 3, 2019, now issued as U.S. Pat. No. 11,142,315, which was a continuation of U.S. patent application Ser. No. 16/432,753, entitled “UAV CONFIGURATIONS AND BATTERY AUGMENTATION FOR UAV INTERNAL COMBUSTION ENGINES, AND ASSOCIATED SYSTEMS AND METHODS,” filed on Jun. 5, 2019, now issued as U.S. Pat. No. 10,676,191, which is a divisional of U.S. patent application Ser. No. 15/261,780, entitled “UAV CONFIGURATIONS AND BATTERY AUGMENTATION FOR UAV INTERNAL COMBUSTION ENGINES, AND ASSOCIATED SYSTEMS AND METHODS,” filed on Sep. 9, 2016, now issued as U.S. Pat. No. 10,351,238, which was a continuation of International Patent Application No. PCT/US2015/019004, entitled “UAV CONFIGURATIONS AND BATTERY AUGMENTATION FOR UAV INTERNAL COMBUSTION ENGINES, AND ASSOCIATED SYSTEMS AND METHODS,” and filed on Mar. 5, 2015, which claims priority to U.S. Provisional Patent Application No. 61/952,675, entitled “BATTERY AUGMENTATION FOR INTERNAL COMBUSTION ENGINE, AND ASSOCIATED SYSTEMS AND METHODS” and filed on Mar. 13, 2014, and U.S. Provisional Patent Application No. 62/037,021, entitled “BATTERY AUGMENTATION FOR INTERNAL COMBUSTION ENGINE, AND ASSOCIATED SYSTEMS AND METHODS” and filed on Aug. 13, 2014, each of which are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to DC power supplies for driving motors, and in particular to a DC power supply for an unmanned aerial vehicle (UAV) with multiple rotors. The DC power supply can be used to power a variety of UAVs, including UAVs with combinations of variable-incidence wings and multiple rotors. 
     BACKGROUND 
     Conventional power supplies for multi-rotor UAVs are generally direct current (DC) batteries. However, most batteries have limited energy density. Accordingly, a battery-only power source provides limited endurance and cannot sustain long range travel for the UAV. Other alternative power sources used by existing multi-rotor vehicles introduce additional problems, such as unpredictable fluctuations in the power supplied to the rotors, thus causing instability in flight. 
     SUMMARY 
     Disclosed are DC power supply systems (e.g., a genset subsystem of a UAV) that utilizes high energy density liquid fuel to increase the travel endurance of multi-rotor vehicles. The disclosed DC power supply system includes a lightweight and high powered energy conversion pipeline that drives an electronic powertrain. The energy conversion pipeline is at least partially powered by liquid fuel. In at least one embodiment, the energy conversion pipeline includes an internal combustion engine (ICE) and a brushless direct current (BLDC) alternator. Embodiments of the disclosed DC power supply system also include a battery module having one or more batteries. Embodiments of the disclosed DC power supply system provides a stable DC voltage to drive multiple rotors under various operational modes including an Engine Start Mode, a generator only mode, a generator-based ripple mitigation mode, a generator with automated Battery Augmentation Mode, a generator with Assisted Augmentation Mode, a Battery-Only Mode, or any combination thereof. 
     The disclosed DC power supply system can implement a hybrid vehicle power supply that uses both an internal combustion engine and a set of batteries. This implementation is superior to traditional hybrid power supplies that are “in series”, where an internal combustion engine charges a battery, and a motor is driven only by the power supplied from the battery. This implementation is also superior to traditional hybrid power supplies that operate as “alternatives” of one another, where the motor is driven either by the ICE or the battery. 
     Some embodiments of the disclosure have other aspects, elements, features, and steps in addition to or in place of what is described above. Several of these potential additions and replacements are described throughout the rest of the specification 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a block diagram of a representative system architecture of a multi-rotor vehicle, in accordance with at least some embodiments. 
         FIG.  1 B  is an illustration of a portion of a representative vehicle on which embodiments of the systems disclosed herein can be installed. 
         FIG.  2    is a block diagram of a representative system architecture of an avionics subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  3    is a block diagram of a representative system architecture of a genset subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  4    is a current flow diagram within the genset subsystem of  FIG.  3    in a Ground-Level Engine Start Mode, in accordance with at least some embodiments. 
         FIG.  5    is a current flow diagram within the genset subsystem of  FIG.  3    in an Inflight Engine Start Mode, in accordance with at least some embodiments. 
         FIG.  6    is a current flow diagram within the genset subsystem of  FIG.  3    in a Generator-Only Mode, in accordance with at least some embodiments. 
         FIG.  7    is a current flow diagram within the genset subsystem of  FIG.  3    in a Ripple Mitigation Mode or a Battery Augmentation Mode, in accordance with at least some embodiments. 
         FIG.  8    is a current flow diagram within the genset subsystem of  FIG.  3    in a Battery-Only Mode, in accordance with at least some embodiments. 
         FIG.  9    is a current flow diagram within the genset subsystem of  FIG.  3    in a Battery Charging Sub Mode, in accordance with at least some embodiments. 
         FIG.  10    is a block diagram of a representative system architecture of a motor-gen controller in a genset subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  11    is a first exemplary circuit diagram of phase controllers within a motor-gen controller in a genset subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  12    is second exemplary circuit diagram of phase controllers within a motor-gen controller in a genset subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  13    is a first exemplary circuit diagram of an augmentation controller within a motor-gen controller in a genset subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  14    is second exemplary circuit diagram of an augmentation controller within a motor-gen controller in a genset subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  15    is a partially schematic plan-view illustration of a vehicle having lift rotors and axial thrust rotors in combination with a power generation system configured in accordance with an embodiment of the present technology. 
         FIG.  16    is a partially schematic, plan-view illustration of a vehicle having multiple lift rotors, a tractor rotor, and dynamically modifiable wing geometries in accordance with an embodiment of the present technology. 
         FIG.  17    is a partially schematic, plan-view illustration of an air vehicle having a configuration generally similar to that described above with reference to  FIG.  16   , without a tractor rotor. 
         FIG.  18    is a partially schematic plan-view illustration of an air vehicle having dynamically modifiable wings and lift rotor pods in accordance with another embodiment of the present technology. 
         FIG.  19    is a partially schematic, plan-view illustration of an air vehicle having dynamically modifiable lift rotor pods in combination with a power generation system in accordance with an embodiment of the present technology. 
         FIG.  20    is a partially schematic, side view of an air vehicle having a fixed wing and a movable rotor boom in accordance with yet another embodiment of the present technology. 
         FIG.  21    is a partially schematic, top isometric view of an air vehicle having lift rotor pods that are controllable in accordance with another embodiment of the present technology. 
         FIG.  22    is a third exemplary circuit diagram of phase controllers within a motor-gen controller in a gen-set subsystem of a vehicle, in accordance with at least some embodiments. 
         FIG.  23    is a block diagram illustrating a health monitor system in accordance with at least some embodiments. 
     
    
    
     The figures depict various embodiments for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein. 
     DETAILED DESCRIPTION 
     The present technology is directed generally to unmanned aerial vehicle (UAV) configurations and battery augmentation for UAV internal combustion engines. Several details describing structures and processes that are well-known and often associated with these types of systems and processes, but that may unnecessarily obscure some significant aspects of the presently disclosed technology, are not set forth in the following description for purposes of clarity. Furthermore, although the following disclosure sets forth several embodiments of different aspects of the disclosed technology, several other embodiments can have different configurations and/or different components than those described in this section. Accordingly, the disclosed technology may include other embodiments with additional elements not described below with reference to  FIGS.  1 A- 23    and/or without several of the elements described below with reference to  FIGS.  1 A- 23   . 
     Several embodiments of the technology described below may take the form of computer-executable instructions, including routines executed by a programmable computer and/or controller. For example, embodiments relating to methods of powering, controlling, flying and/or otherwise operating a UAV can be implemented via computer-executable instructions. Persons having ordinary skill in the relevant art will appreciate that the technology can be practiced on computer and/or controller systems other than those described below. The disclosed technology can be embodied in a special-purpose computer, controller or data processor that is specifically programmed, configured or constructed to perform one or more of the computer-executable instructions. Accordingly, the terms “computer” and “controller” as generally used herein refer to any suitable data processor and can include Internet appliances and hand-held devices (including palm-top computers, wearable computers, cellular or mobile phones, multi-processor systems, processor-based or programmable consumer electronics, network computers, mini computers and the like). Information handled by these computers can be presented at any suitable display medium. 
     The technology can also be practiced in distributed environments, where tasks or modules are performed by remote processing devices that are linked through a communications network. For example, a controller in a system in accordance with the present disclosure can be linked with and control other components in the system. In a distributed computing environment, program modules or subroutines may be located in local and remote memory storage devices. Aspects of the technology described below may be stored or distributed on computer-readable media, including magnetic or optically readable or removable computer disks, as well as distributed electronically over networks. 
     1.0 Overview 
     The present disclosure describes both UAV configurations and power systems to provide battery augmentation for internal combustion engines used by UAVs. In some embodiments, the disclosed UAV configurations include the battery augmentation systems, and in other embodiments, the disclosed UAV configurations need not include the disclosed battery augmentation systems. Similarly, the disclosed battery augmentation systems can be implemented on UAV configurations other than those shown and described below. In general, the battery augmentation aspects of the disclosure are described below under headings 2.0-8.0, and further UAV configurations are described under heading 9.0. 
     2.0 Multi-Rotor Vehicle System 
       FIG.  1 A  is a block diagram of a representative system architecture of a multi-rotor vehicle  100 , in accordance with at least some embodiments. A representative vehicle platform is shown in  FIG.  1 B . The multi-rotor vehicle, for example, can be a rotary wing vehicle utilizing eight electrically driven fixed pitch rotors. As used herein, the term “rotor” is used to include rotors, propellers and any other suitable rotating blade or blade-type structure that imparts a force to a vehicle via interaction with the surrounding fluid medium. The multi-rotor vehicle can include multiple subsystems. The subsystems can include an avionics subsystem  102 , a genset subsystem  104 , one or more of electronic speed controllers (ESCs)  106  (e.g., 8 controllers in a vehicle with 8 rotors), and one or more drive motors  108  that drive one or more rotors  110  (e.g., propellers). In some embodiments, a drive motor is “coupleable” to a rotor/propeller. That is, the drive motor is adapted in a structure that is capable of being coupled to the rotor/propeller. 
     The multi-rotor vehicle  100  can contain one or more avionics batteries  112  and one or more vehicle batteries  114 . One or more (e.g., all) drive motors  108  and rotors  110  combinations can be powered by three phase alternating current (AC) electrical power, supplied by one of the dedicated electronic speed controllers (ESC)  106 . 
     The ESCs  106  can be powered by a common direct current power bus (hereinafter, the “DC motor bus  116 ”). The DC motor bus  116  is powered by the genset subsystem  104 , whose primary role is to convert liquid fuel into DC power via a microcontroller-managed motor-generator conversion pipeline. The genset subsystem  104  can include a microcontroller to manage the motor-generator conversion pipeline. The thrust produced by each of the ESCs  106 , the drive motors  108 , and the rotors  110  combination can be controlled via dedicated, unidirectional serial links that use pulse width modulation (PWM) encoded control signals, connected to the avionics subsystem  102 . 
       FIG.  1 B  is an illustration of a portion of a representative vehicle, such as the multi-rotor vehicle  100 , on which embodiments of the systems disclosed herein can be installed. 
       FIG.  2    is a block diagram of a representative system architecture for an avionics subsystem  200  of a vehicle (e.g., the multi-rotor vehicle  100  of  FIG.  1   ), in accordance with at least some embodiments. For example, the avionics subsystem  200  can be, or be part of, the avionics subsystem  102  of  FIG.  1 A . 
     The avionics subsystem  200  can facilitate remotely piloted flight control and/or autonomous flight control. The avionics subsystem  200  can include at least the following functional blocks: a flight controller  202 , an autopilot module  204 , a DC-DC Converter  206 , a micro air vehicle link (MAVLink) Interface  208 , a telemetry transceiver  210 , an auxiliary remote control receiver  212 , a global positioning system (GPS) receiver  214 , a magnetometer  216 , a barometric pressure sensor  218 , or any combination thereof. 
     Most multi-rotor vehicles are neither dynamically nor statically stable, and thus require active flight stabilization. The flight controller (FC)  202  can be a module contained within the operating code of an avionics controller  220  (e.g., an avionics microcontroller). The avionics controller  220  can be connected to the vehicle ESCs, thus controlling the thrust produced by each drive motor/rotor combination and providing stabilized flight. 
     The flight controller  202  can use a six-axis accelerometer array  222  to ascertain the specific thrust levels that each motor/prop combination needs to produce, in order to maintain, or change, desired acceleration values over three rotational axes and three translational planes. The flight controller  202  is also capable of holding a preset vehicle orientation (i.e., maintaining zero velocity across all three axis). The flight controller  202  can either be commanded by a ground based pilot (under a Fully Manual Remotely Piloted Operation Mode), an autopilot (under an Autonomous Operation Mode), or a combination of manual commands from a ground based pilot and an autopilot-based augmentation (under a Fly-By-Wire Operation Mode). The flight controller  202  receives control information from any individual or combination of command sources depending on which mode is active and/or whether the avionics subsystem  200  is using primary or backup radio frequency (RF) control links. The command sources can include: the telemetry transceiver  210  (e.g., interfaced through the MAVLink interface  208  via interprocess communication (IPC)); the auxiliary remote control receiver  212  (e.g., PWM links); and an Inter-Process Communication (IPC) link from the autopilot module  204 . 
     The autopilot module  204  can be contained within the operating code of the avionics controller  220 . The autopilot module  204  provides at least two functions, including execution of stored flight plans during the autonomous flight operation mode and integration of GPS, barometric altimetry, and magnetometer data during the Fly-by-Wire modes operation mode. 
     The autopilot module  204  can be connected to both the GPS receiver  214  (e.g., via a TTL Serial Link) and the magnetometer  216  (e.g., via an I2C link). The autopilot module  204  can be connected to the barometric pressure sensor  218  via its IPC link. External to the vehicle, the autopilot module  204  can also connect with a control station via the MAVLink interface  208  (e.g., IPC-connected interface) and the telemetry link. The autopilot module  204  can further be connected to a dedicated remote handheld flight controller via PWM links through the auxiliary remote control receiver  212  (e.g., a radio receiver). 
     All avionics functions in the avionics subsystem  200  can be powered by the DC-DC converter  206  (e.g., a dedicated DC-DC converter). The DC-DC converter  206  is powered by one or more avionics batteries in the vehicle. Alternatively, the DC-DC converter  206  can also be powered by a genset subsystem, such as the genset subsystem  104  of  FIG.  1 A  or the genset subsystem  300  of  FIG.  3   . The DC-DC converter can also receive backup power or power augmentation from the genset subsystem. 
       FIG.  3    is a block diagram of a representative system architecture of a genset subsystem  300  of a vehicle (e.g., the multi-rotor vehicle  100  of  FIG.  1   ), in accordance with at least some embodiments. For example, the genset subsystem  300  can be the genset subsystem  104  of  FIG.  1   . The genset subsystem  300  implements the disclosed DC power supply system that enables battery power to augment power generated from an internal combustion engine (ICE)  302 . In some embodiments, another fuel-based power source can replace the ICE  302 . For example, a fuel-based power source can generate mechanical movement and couple the mechanical movement input to an alternator  306 . 
     The genset subsystem  300  implements an energy conversion pipeline that converts liquid fuel to electrical energy through the ICE  302  and the alternator  306 , such as a brushless DC alternator. The alternator  306  can have a mechanical movement input and a multiphase alternating current output. The energy conversion pipeline can have a high ratio of conversion pipeline weight to power density. This ratio is referred to as the pipeline conversion efficiency (PCE). The genset subsystem  300  can advantageously use lightweight hardware controlled by a complex power management system implemented by a microcontroller  308 . The microcontroller  308  receives monitor sensor links to determine the state of the genset subsystem  300  and outputs various control links to adjust various components of the genset subsystem  300 .  FIG.  3    illustrates examples of the sensor links and the control links as shaded boxes. This combination enables the use of the ICE  302  by implementing a way to stabilize the DC power output of the ICE  302 . The genset subsystem  300  is able to reach higher levels of PCE that are normally unreachable by conventional power management systems. 
     The disclosed vehicle uses the ICE  302  (e.g., a lightweight ICE) to mechanically drive the alternator  306 . For example, the alternator  306  can be a multi-phase alternator (e.g., The alternator  306  through a transmission. In at least some cases, neither the ICE  302 , nor the alternator  306  are necessarily well suited for powering electrically driven multi-rotor vehicles due to the ripples in the power they generate. The ICE  302  and the alternator  306  are, however, among the highest density (e.g., watt per lbs) components for converting liquid fuel to raw electrical energy. 
     In order to gain the benefit of these components (e.g., the very high conversion density), the disclosed vehicle implements control modules via the microcontroller  308  to carefully monitor and actively control both the ICE  302  and other components within the conversion pipeline. 
     The energy conversion pipeline can begin with fueling the ICE  302 . The microcontroller  308  can implement a DC motor bus regulation (MBR) module  310  that controls the power output and rotational frequency (revolutions per minute (RPM)) of the ICE  302 . The DC MBR module  310  can be a module implemented by the microcontroller  308  executing digital instructions stored on a persistent digital memory within or outside the microcontroller  308 . The DC MBR module  310  controls the ignition, throttle and fuel/air mixture of the ICE  302 . The DC MBR module  310  also monitors the current and voltages on both a DC motor bus  312  and the vehicle&#39;s battery bus  314 , such as when starting up the ICE  302 . 
     A transmission  316  can mechanically connect the ICE  302  and the alternator  306 . The alternator  306  can be a multi-phase alternator having three external phase outputs that nominally create a three phase AC. Each external phase connection can be connected to multiple internal phases within the alternator  306 . 
     This multi-phase configuration of the alternator  306  can maximize the mechanical conversion efficiency of the alternator  306  (e.g., in terms of watts per unit torque). This configuration of the alternator  306 , however, can produce AC electrical power that contains a highly complex set of waveforms, along with transient inductances. 
     To address these potential inefficiencies, the genset subsystem  300  converts the AC power feed into a direct current (DC) power feed in the DC motor bus  312  by actively rectifying the AC signal and reducing inductance-related power conditioning deficiencies via a motor-gen controller (MGC)  318 . The MGC  318  can also compensate for ripples in the converted direct-current power feed. 
     The genset subsystem  300  can also operate by using the alternator  306  as a starter motor for the ICE  302 . In order to facilitate this mode of operation, the three AC phases of the alternator  306  are connected to the MGC  318 . The MGC  318  can be actively controlled by the microcontroller  308 . The MGC  318  can provide lossless rectification of the complex AC power feed into a DC power feed on the DC motor bus  312 . The MGC  318  can also provide active and dynamic cancelation of synchronous reactance (e.g., Power Factor correction) and provide three phase power to the alternator  306  in order to drive the alternator  306  as a motor during a start sequence of the ICE  302 . The MGC  318  can further enable dynamic integration of the vehicle&#39;s battery power both during periods of transient power deficits and during a complete failure of the ICE  302  or the alternator  306  (e.g., the vehicle can operate in a Battery-Only Mode, which can be commanded by ground-based operators if such operation is desired). The MGC  318  can yet further provide active mitigation of ripple in the DC output of the genset subsystem  300 . 
     Typical passive rectifiers use a diode that imposes a forward voltage drop during rectification. This property of a passive rectifier “clips” the peak of an AC input voltage by exactly the amount of the forward voltage drop. As an example, if a single phase AC signal with a peak-to-peak voltage of 20V is introduced into a bridge rectifier (e.g., 4 diodes configured to invert the “negative” side of the AC signal), the resulting peak of the DC output would be 10V minus the voltage drop across the diodes used in the rectifier. For example, for a typical power diode, the forward voltage drop is 1.7V, or a 17% drop in the peak voltage in the above example. Power generally scales as the square of voltage. Hence, for example, reducing the voltage to 83% (i.e., 17% drop) reduces the power to around 69% (i.e., 0.83 2 ), resulting in an approximately 31% power loss. This effect is particularly significant in low voltage AC applications (e.g., AC power generated from the alternator  306 ). 
     In embodiments where the alternator  306  generates lower voltage AC, implementation of passive rectifiers in the MGC  318  would cost a reduction in power and would create potential cooling problems in the passive rectifiers (i.e., from power dissipation associated with the voltage drop across the diodes). In these embodiments, the MGC  318  implements phase controllers to perform active rectification. In several embodiments, with active rectification, instead of using power diodes, transistors are used as diodes in each of the phase controllers to minimize forward voltage drop (e.g., see  FIGS.  11  and  12   ). For example, the transistors can be field effect transistors (FETs) or bipolar transistors. As a specific example, the FETs can be metal oxide semiconductor field effect transistors (MOSFETs). As another specific example, the bipolar transistors can be insulated gate bipolar transistors (IGBTs) Each transistor can include a “body diode.” The MGC  318  can reduce resistance and the forward voltage drop across the body diode by turning the transistor on (e.g., by applying a suitable gate voltage to the transistor). The transistors of the phase controllers enable the MGC  318  to emulate a diode-based rectifier without the power reduction. In some embodiments, diodes are still used as part of the phase controllers (e.g., see  FIG.  22   ). 
     This reduction of resistance is enabled by use of the N channel in each FET to cancel the forward voltage drop of the FET&#39;s body diode (e.g., 1.7V drop). The MGC  318  turns on a respective FET&#39;s N channel (e.g., by applying suitable gate voltage to the FET) any time the body diode of the FET is conducting. The MGC  318  can detect whether the body diode is conducting in at least two ways. The MGC  318  can include a current shunt in each phase controller to sense current flow across the body diode and locally (e.g., within the phase controller). If the current flow indicates the body diode is conducting, a suitable gate voltage is applied to the respective FET to turn the FET into saturation. In other embodiments, the AC phase outputs of the alternator  306  are monitored by the microcontroller  308 . The microcontroller  308  can drive the gate voltage of respective FETs into saturation based at least partly on the monitored voltage from the alternator  306  (e.g., by determining whether the monitored voltage relative to the DC motor bus  312  would cause the body diode to conduct). 
     Because a saturated FET can conduct current at very low power loss, the rectification process described above can be considered a “lossless rectification.” This feature is advantageous because the FETs can behave like a diode with an almost immeasurably low forward voltage drop, thus avoiding power loss through the forward voltage drop. 
     The genset subsystem  300  can operate in different operational modes. For example, these operational modes can include an Engine Start Mode, a Generator-Only Mode, a generator with Ripple Mitigation Mode, a generator with Battery Augmentation Mode, and a Battery-Only Mode. At any time the alternator  306  is producing power, a battery charging sub mode may be activated. The battery charging sub mode can be operational together with the Generator-Only Mode, the generator with Ripple Mitigation Mode, and the generator with Battery Augmentation Mode. 
     Any time the alternator  306  is producing power (e.g., the Generator-Only Mode, the generator with Ripple Mitigation Mode and the generator with Battery Augmentation Mode), the MGC  318  can provide rectification of the AC power feed from the alternator  306 . The MGC  318  can operate under two rectification modes as well, including an autonomous rectification mode and an assisted rectification mode. 
     The genset subsystem  300  can further include a motor bus monitor  320 , a battery charger  322 , a fuel tank  324 , a battery monitor  326 , and a battery bus switch  328 . The motor bus monitor  320  monitors the voltage and current flow through the DC motor bus  312  for the microcontroller  308 . The battery charger  322  charges and monitors the vehicle batteries  114 . The fuel tank  324  stores fuel for the ICE  302 . The battery monitor  326  monitors the voltage and current through the battery bus  314  for the microcontroller  308 . The battery bus switch  328  connects zero or more of the vehicle batteries  114  to the battery bus  314  (zero meaning disconnecting the battery bus  314  from any battery). 
       FIG.  4    is a diagram of current flow within the genset subsystem  300  of  FIG.  3    in a Ground-Level Engine Start Mode, in accordance with at least some embodiments. In this mode, the microcontroller  308  initially monitors the battery bus  314  (labeled as “VBATTERY”) and a fuel level (labeled as “LEVELFUEL”) to ensure both are adequate for the ICE  302  to start. 
     The microcontroller  308  then commands 3 phase power (commutated DC) to be directed toward the alternator  306  via a combination of control signals (e.g., control voltage low signal and control voltage high signal, labeled as “CTRLVL”, “CTRLVH”, respectively) to the MGC  318 . In response, the MGC  318  generates the 3 phase commutated DC power. The microcontroller  308  also controls the engine throttle of the ICE  302  and the fuel mixture of the ICE  302  via control signals (e.g., pulse width modulated signals) to the ICE  302  (labeled as “PWMTHROTTLE” and “PWMMIXTURE” respectively). 
     Sensor signals can be fed back to the microcontroller  308 . For example, engine rotational speed (e.g., RPM, labeled as “RPMENGINE”), exhaust gas temperature (labeled as “TEMPEGT”), cylinder head temperature (labeled as “TEMPCHT”), and battery bus current (to label as “CBATTERY”) can be monitored by the microcontroller  308 . The battery charge can be used as a proxy for startup torque of the ICE  302 . The sensor signals can close the feedback loop for the ICE  302  startup sequence. 
     The ICE  302  can be started while the vehicle is on the ground, as well as while the vehicle is in flight.  FIG.  4    depicts a current flow state of the genset subsystem  300  when starting the ICE  302  on the ground. One or more of the vehicle batteries (e.g., the vehicle batteries  114 ) can be utilized in this mode.  FIG.  5    is a diagram of current flow within the genset subsystem  300  of  FIG.  3    in an Inflight Engine Start Mode, in accordance with at least some embodiments. In this mode, the DC motor bus  312  is energized by the MGC  318  (e.g., an augmentation controller of the MGC  318 ). The DC motor bus  312  delivers power and thus enables the vehicle&#39;s drive motors (e.g., the drive motors  108 ) to propel the vehicle. The MGC  318  at the same time can commutate power to the alternator  306  so that the alternator  306  can start the ICE  302 . For example, phase controllers that are used for rectifying AC power from the alternator  306  in other modes can now be used to communicate power to the alternator  306 . 
     3.0 Genset System Operational Modes 
     3.1 Generator-Only Mode 
       FIG.  6    is a diagram of current flow within the genset subsystem  300  of  FIG.  3    in a Generator-Only Mode, in accordance with at least some embodiments. In the Generator-Only Mode, all motive power for the vehicle is supplied by the alternator  306 . In this mode, the microcontroller  308  can actively manage both ICE  302 &#39;s torque production, as well as the various power conditioning functions of the MGC  318 . 
     The microcontroller  308  monitors voltage at the DC motor bus  312  (via a sensor link labeled “VMOTOR”). The microcontroller  308  can also manage ICE  302 &#39;s torque output (via a controller link labeled “PWMTHROTTLE”). The microcontroller  308  also manages the efficiency of the ICE  302  by optimizing mixture by monitoring the exhaust gas temperature (via the sensor link labeled “TEMPEGT”) as a combustion efficiency feedback loop. Rectification of the AC power provided through the alternator  306  is provided by the MGC  318 , either via autonomous or assisted modes. 
       FIG.  7    is a current flow diagram within the genset subsystem  300  of  FIG.  3    in a Ripple Mitigation Mode or a Battery Augmentation Mode, in at least some embodiments. 
     3.2 Generator with Ripple Mitigation Mode 
     Operation in the Ripple Mitigation Mode can be identical to the Generator-Only Mode, with the exception that the one or more of the vehicles&#39; batteries are used by the MGC  318  to remove ripple from the rectified output power, prior to output to the DC motor bus  312 . In some embodiments, the augmentation controller is configurable to prevent the direct current from the DC motor bus  312  from flowing into the battery bus  314 , and to allow current to flow from the battery bus  314  to the DC motor bus  312  when a first voltage of the DC motor bus  312  falls below a second voltage of the battery bus  314 . 
     One feature of this operating mode is the combination of the augmentation controller&#39;s functionality within the MGC  318 , and the microcontroller  308 &#39;s regulation of the output of the alternator  306 . In the Ripple Mitigation Mode, the microcontroller  308  monitors the nominal voltage on the battery bus  314  and utilizes that to control the throttle of the ICE  302 . Via the throttle control of the ICE  302 , the microcontroller  308  can ensure that the peak voltage of the DC ripple from the rectification process (e.g., via phase controllers in the MGC  318 ) matches the nominal bus voltage of the battery bus  314 . For example, the augmentation controller is configurable to provide that the alternator produces less voltage than a nominal voltage of a battery in the battery set. 
     As a result, during transient troughs in DC ripple in the output of the rectification process, the augmentation controller connects the battery bus  314  to the DC motor bus  312 . This connection effectively “fills in” the troughs in the DC output with power from the battery bus  314 , and creates a substantially ripple-free output from the MGC  318  to the DC motor bus  312 . 
     A control link labeled “SELECTBAT” allows the microcontroller  308  to select which of the vehicle batteries should be used in this mode. The microcontroller  308  can select one or more of the vehicle batteries. For example, the microcontroller  308  can use one battery for ripple mitigation and charge another battery with the DC power from the DC motor bus  312 . 
     3.3 Generator with Battery Augmentation Mode 
     Operation in this mode can be identical to the Generator-Only Mode, with the exception that the one or more of the vehicle batteries  114  are used by the MGC  318  to augment the power supplied by the alternator  306 . There are two augmentation sub modes when operating under this mode including an automated augmentation and a selected augmentation. 
     3.3A Automated Augmentation Sub Mode 
     This sub mode is used when the vehicle requires more power than the alternator  306  can provide. This sub mode can either be triggered by a catastrophic failure of some component in the ICE  302 , the transmission  316 , or the alternator  306 , or a momentary power deficit due to unusual/extreme flight conditions. This sub mode can also be commanded from the microcontroller  308 . In some embodiments, when in this sub mode, the ICE  302 &#39;s throttle is at a maximum, and the augmentation controller mediates transfer of power from the battery bus  314  to the DC motor bus  312 , thus augmenting the power output of the alternator  306  with battery power. 
     The augmentation controller can accomplish this mediation by utilizing the voltage differential between the DC motor bus  312  and the battery bus  314  to regulate augmentation from the battery, such that as much of the power from the alternator  306  as possible is used by the vehicle&#39;s drive motors (e.g., the drive motors  108 ), and thus the ship&#39;s battery usage is limited only to that which is needed beyond the maximum power provided by the alternator  306 . 
     In particular embodiments, whenever the voltage on the DC motor bus  312  (e.g., the root mean square (RMS) voltage produced by the alternator  306  and the rectification process) falls below that of the battery bus  314 , the augmentation controller directs power from the battery bus  314  to the DC motor bus  312 . Conversely, as the system load decreases such that the RMS voltage produced by the alternator  306  and rectification process rises above that of the battery bus  314 , the augmentation controller ceases augmenting power on the DC motor bus  312 . 
     3.3B Selected Augmentation Sub Mode 
     This sub mode allows the microcontroller  308  to command one or more of the vehicle batteries  114  to contribute a set amount of current to the DC motor bus  312 . This sub mode can be used to reduce the power load on the ICE  302  when one or more of the ICE  302 &#39;s thermal limits have been reached (e.g., the exhaust gas temperature limit or the cylinder head temperature limit). 
     This sub mode combines the augmentation controller&#39;s functionality and the microcontroller  308 &#39;s regulation of voltage output from the alternator  306  into the rectification process. When operating in this sub mode, the microcontroller  308  manages the throttle control of the ICE  302 , e.g., ensuring the measured current from the battery bus  314  (via a sensor link labeled “CBATTERY”) remains at a set current contribution level. 
     If “CBATTERY” falls below the selected set point, the ICE  302 &#39;s throttle is reduced, thus reducing the torque to the alternator  306 . In turn, the RMS voltage of the output from the rectification process to the augmentation controller is also reduced. This reduction increases the voltage imbalance between the DC motor bus  312  and battery bus  314 , eventually causing the voltage at the DC motor bus  312  to fall relative to the voltage at the battery bus  314 . The falling of the voltage at the DC motor bus  312  causes an increase to the current contribution from the battery bus  314  through the augmentation controller to the DC motor bus  312 . 
     Conversely, if “CBATTERY” rises above the selected set point, the ICE  302 &#39;s throttle is increased, thus increasing the RMS voltage of the output from the rectification process in the MGC  318  to the augmentation controller. This increases the voltage imbalance between the DC motor bus  312  and the battery bus  314 , causing the DC motor bus  312  to rise relative to the battery bus  314 . This rise thus decreases the current contribution from the battery bus  314  through the augmentation controller to the DC motor bus  312 . 
     3.4 Battery-Only Sub-Mode 
       FIG.  8    is a diagram of the current flow within the genset subsystem of  FIG.  3    in a Battery-Only Mode, in accordance with at least some embodiments. This mode can be considered a special case of the Automated Augmentation sub mode described above, used when no power is available from the alternator  306 . This mode can either be triggered by a failure of a component in the ICE  302 , the transmission  316 , or the alternator  306 , or via command from the microcontroller  308 . 
     As with the Automated Augmentation sub mode, when in the Battery-Only Mode, the augmentation controller connects the battery bus  314  to the DC motor bus  312 . This ensures that the battery bus  314  provides all the power required by the DC motor bus  312  to drive the drive motors (e.g., the drive motors  108 ). 
     3.5 Battery-Charging Sub-Mode 
       FIG.  9    is a diagram of the current flow within the genset subsystem of  FIG.  3    in a battery charging sub mode, in accordance with at least some embodiments. In a particular embodiment, any time the alternator  306  is producing power, one or more of the vehicle batteries  114  can be charged. When all of the vehicle batteries  114  are being charged, none of the battery-augmented modes are available (e.g., the Ripple Mitigation Mode or the Battery Augmentation Mode). 
     If only a subset of the vehicle batteries  114  are being charged, then one or more other batteries can be used to enable any of the battery-augmented modes, and thus ensuring adequate battery charge levels can be maintained. This enables battery charging to occur even during periods when ripple suppression or battery augmentation are necessary or beneficial.  FIG.  9    depicts only one of many battery charging mode permutations available with the genset subsystem  300 . In this example, a first battery is being used for one of the battery-augmented modes, and a second battery is being charged. 
       FIG.  10    is a block diagram of a representative system architecture of a motor-gen controller (MGC)  1000  in a genset subsystem of a vehicle, in at least some embodiments. For example, the motor-gen controller  1000  can be the MGC  318  in the genset subsystem  300 . 
     The MGC  1000  provides a direct linkage within the genset subsystem between alternator phases  1002  of an alternator (e.g., the alternator  306  of  FIG.  3   ) and either or both a DC motor bus  1014  (labeled as “V MOTOR ”) and the vehicle&#39;s battery bus  1012  (labeled as “V BATTERY ”). The alternator phases  1002  can act as either input or output from the alternator, depending on the operation mode of the genset subsystem. 
     The MGC  1000  includes at least a phase detector  1004  coupled to one of the alternator phases  1002 . The phase detector  1004  can transmit a sensor link labeled “PHASE DETECT ” back to a microcontroller of the genset subsystem (e.g., the microcontroller  308  of  FIG.  3   ). The sensor link can report the progression of the AC phases to or from the alternator. For example, because the phase difference between the alternator phases  1002  is constant, determining the AC phase of one of the alternator phases  1002  enables the microcontroller to determine others of the alternator phases  1002  at any given time. The phase detector  1004  provides the microcontroller with an angular reference point for the alternator&#39;s rotor. 
     The MGC  1000  also has several phase controllers coupled to the alternator phases  1002 , such as two phase controllers per phase. For a three phase alternator, the MGC  1000  can include six phase controllers, including high-side phase controllers (e.g., phase controllers  1006   a ,  1006   b , and  1006   c , collectively referred to as “high-side phase controllers  1006 ”) and low-side phase controllers (e.g., phase controllers  1008   a ,  1008   b , and  1008   c , collectively referred to as “low-side phase controllers  1008 ”). 
     The DC motor bus  1014  and the battery bus  1012  can each have a higher voltage line and a lower voltage line. Each of the high-side phase controllers  1006  can be coupled to the higher voltage line of the DC motor bus  1014  and the low-side phase controllers  1008  can be coupled to the lower voltage line of the DC motor bus  1014 . An augmentation controller  1010  can be coupled to the battery bus  1012  on one side and the DC motor bus  1014  on the other, enabling some DC current to flow from the battery bus  1012  to the DC motor bus  1014  in some operational modes of the MGC  1000  and/or the genset subsystem. 
     In the illustrated example, there are a total of six phase controllers in the MGC  1000 . Each alternator phase (e.g., labeled as “U”, “V”, and “W”) is wired into a pair of phase controllers. Each of these alternator phases  1002  has a phase controller (e.g., one of the high-side phase controllers  1006 ) connected to the positive side of the DC motor bus  1014 , and a phase controller (e.g., one of the low-side phase controllers  1008 ) connected to the ground of the DC motor bus  1014 . 
     In a particular embodiment, any time the alternator  306  is producing power, the genset subsystem  300  provides rectification of that power, thus providing DC power to the vehicle. All six of the phase controllers  1006  and  1008  can operate together in at least one of three modes: Engine Start Mode, Autonomous Rectification Mode, and Assisted Rectification Mode. The microcontroller of the genset subsystem can instruct the phase controllers in specific operational modes via control links (e.g., labeled as “MODE R ” in  FIG.  10   ). 
     3.6 Engine Start Mode 
     In the Engine Start Mode, each of the phase controllers  1006  and  1008  acts as a high speed and low impedance switch, enabling current flow from its respective side of the DC motor bus  1014  to its respective alternator phase. Switching is controlled by the microcontroller of the genset subsystem, via individual control lines  1016  (e.g., one for each of the phase controllers  1006  and  1008 , labeled as “CTRL UH ”, “CTRL UL ”, “CTRL VH ”, “CTRL VL ”, “CTRL WH ”, and “CTRL WL ”). 
     The control lines allow the microcontroller of the genset subsystem to connect either ground or positive to any of the alternator phases  1002 . Through this, the phase controllers  1006  and  1008  provide commutated power to the alternator during the Engine Start Mode. 
     4.0 Phase Controller Rectification Modes 
     4.1 Autonomous Rectification 
     The Autonomous Rectification Mode of the phase controllers  1006  and  1008  enables rectification of AC power from the alternator (e.g., the alternator  306 ) without external control processes. In this mode, each of the phase controllers  1006  and  1008  behave like a diode with a very low (e.g., below 1 mV) forward voltage drop. As a result, the six phase controllers  1006  and  1008  can behave similar or identical to a 3 phase bridge rectifier, except without any meaningful voltage drop. 
     Like diodes, the high-side phase controllers  1006  connect to respective alternator phases  1002  to the positive side of the DC motor bus  1014  when the high-side phase controllers  1006  sense a positive slope zero crossing on their respective alternator phases  1002 . In similar fashion, the low-side phase controllers  1008  connect to respective alternator phases  1002  to the ground side of the DC motor bus  1014  when the low-side phase controllers  1008  sense a negative slope zero crossing on their respective alternator phases  1002 . 
     4.2 Assisted Rectification 
     This rectification mode is used when the alternator characteristics and the system load create synchronous reactance (e.g., phase differences between the voltage and current consumed by the electronic speed controllers of the vehicle, such as the ESCs  106  of  FIG.  1   ) that exceeds the electronic speed controllers&#39; capacity for compensation. That is, the microcontroller instructs the phases controllers  1006  and  1008  to perform assisted rectification when the power factor of the combined load falls too far below unity. 
     In this mode, each of the phase controllers  1006  and  1008  act as a high speed and low impedance switch, enabling current flow from its respective alternator phase to its respective side of the DC motor bus  1014 . Switching is controlled by the microcontroller of the genset subsystem via the individual control lines  1016 . The microcontroller can use the phase indication from the phase detector  1004  during assisted rectification to determine the timing of all phase controller switching. 
     Once the microcontroller determines the timing of the phase controller switching, the microcontroller can provide both exact “zero crossing” based switching. This type of switch can provide the same rectification properties as in the Autonomous Rectification Mode. The microcontroller can also implement “off axis” switching (e.g., in advance of zero crossing). The microcontroller implements the “off axis” switching during power factor correction modes. 
     The microcontroller can selectively switch some of the phase controllers  1006  and  1008  prior to zero crossing, in order to disconnect the alternator phases  1002  during periods of transient induction (e.g., what happens with Wye-connected alternator architectures during the latter part of each power cycle). By disconnecting a phase prior to induction being exhibited in the phase, the net inductance of the phase is reduced. This type of switching increases the power factor of the phase and thus reduces the induced voltage and current phase delta. 
     5.0 Augmentation Controller Modes 
     The augmentation controller  1010  can operate in at least 3 modes, including Engine Start Mode, Assisted Augmentation Mode and Isolation Mode. 
     5.1 Engine Start Mode 
     In this mode, the augmentation controller  1010  connects the DC motor bus  1014  directly to the battery bus  1012  enabling battery power to flow through the various phase controllers  1006  and  1008  to the alternator (e.g., through the alternator phases  1002 ) during engine start. 
     5.2 Assisted Augmentation 
     In this mode, the augmentation controller  1010  behaves like a diode with a very low (e.g., below 1 mV) forward voltage drop, allowing current to flow from the battery bus  1012  to the DC motor bus  1014  whenever the voltage on the DC motor bus  1014  drops below the battery bus  1012  voltage. 
     The microcontroller can select the assisted augmentation mode for the augmentation controller  1010  when the genset subsystem is in the Ripple Mitigation Mode and in the Battery Augmentation Mode (e.g., including applicable sub modes). In these genset subsystem modes, the microcontroller can modulate the RMS voltage output of the alternator (e.g., by controlling the ICE in the genset subsystem) as its primary control mechanism for these augmentation modes. For example, the microcontroller can modulate the RMS voltage output by controlling the throttling of the internal combustion engine coupled to the alternator. 
     The microcontroller can also put the augmentation controller  1010  in the Assisted Augmentation Mode when the genset subsystem is in the Generator-Only Mode. This enables fully autonomous battery backup in the event of sudden loss of power output from the alternator (e.g., ICE failure, transmission failure, etc.). 
     5.3 Isolation Mode 
     In this mode, the battery bus  1012  and the DC motor bus  1014  are completely isolated from each other. This mode would only be used in the event of a battery bus fault (e.g., failure of the battery bus  1012 , one or more of the batteries, or the battery switch). The Isolation Mode disables the automatic battery backup function provided by the Assisted Augmentation mode and leaves the vehicle vulnerable to a loss-of-power event. 
     6.0 Example of Transistor-Based Phase Controllers 
       FIG.  11    is a first representative circuit diagram of phase controllers  1100  within a motor-gen controller in a genset subsystem of a vehicle, in at least some embodiments. For example, the motor-gen controller can be the MGC  318  in the genset subsystem  300  of  FIG.  3   . The motor-gen controller can include a microcontroller  308  of  FIG.  3   . The illustrated pair of the phase controllers  1100  include a high-side phase controller and a low-side phase controller. 
     The phase controllers  1100  is coupled to an alternator phase  1102  labeled “BLDC MPhase,” a DC motor bus  1104  labeled “VMotor_Bus,” a battery bus  1106  labeled “VbatteryD.” The alternator phase  1102  is a bi-directional connection to one of the phases from the alternator. The alternator phase  1102  can be one of the alternator phases  1002  of  FIG.  10   . The DC motor bus  1104  can be the DC motor bus  312  of  FIG.  3    or the DC motor bus  1014  of  FIG.  10   . The battery bus  1106  can be the battery bus  314  of  FIG.  3    or the battery bus  1012  of  FIG.  10   . 
     The phase controllers  1100  are further connected to control links from the microprocessor of the genset subsystem. For example, the phase controllers  1100  can receive inputs from the microcontroller including a high-side phase control link  1108 , a low-side phase control link  1110 , a high-side power factor correction (PFC) enable link  1112 , and a low-side PFC enable link  1114 . 
     The phase controllers  1100  includes two pairs of current switches, such as field effect transistors, corresponding to a high-side phase controller and a low-side phase controller. For example, a high-side PFC switch  1116  and a high-side control switch  1118  correspond to the high-side phase controller and a low-side PFC switch  1120  and a low-side control switch  1122  correspond to the low-side phase controller. 
     As described above, the phase controllers  1100  can operate in an Autonomous Rectification Mode and Assisted Rectification Mode. In the Autonomous Ratification Mode, the microcontroller can keep the high-side PFC switch  1116  and the low-side PFC switch  1120  turned on. In the Assisted rectification Mode, the microcontroller can turn on and off the high-side PFC switch  1116  and the high-side control switch  1118  at the same time and turn on and off the low-side PFC switch  1120  and the low-side control switch  1122  at the same time. 
     6.1 Autonomous Rectification Mode for the Transistor-Based Phase Controllers 
     The phase controllers  1100  include a current detection circuit  1124  coupled to the alternator phase  1102 . The current detection circuit  1124  determines either if a body diode of the high-side control switch  1118  is flowing or if a body diode of the low-side control switch  1122  is flowing and indicates which body diode is flowing through voltage terminals labeled “VGateAutoHi” and “VGateAutoLo”. 
     A gate control circuit  1126  receives such an indication from the current detection circuit  1124 . If the body diode of the high-side control switch  1118 , then higher voltage is applied to a gate of the high-side control switch  1118 . If the body diode of the low-side control switch  1122 , then higher voltage is applied to a gate of the low-side control switch  1122 . 
     6.2 Assisted Rectification Mode for the Transistor-Based Phase Controllers 
     Assisted Rectification Mode is enabled by a PFC driver circuit  1128 . The PFC driver circuit  1128  is driven by the high-side PFC enable link  1112  and the low-side PFC enable link  1114 . These control links allow the microcontroller to disconnect the alternator phase  1102  during periods of transient induction as determined by the microcontroller. By disconnecting the alternator phase  1102  prior to induction being exhibited, the net inductance of the alternator phase is reduced. 
     6.3 Engine Start Mode for the Transistor-Based Phase Controllers 
     As described in  FIG.  10   , the battery bus  1106  is connected to the phase controllers  1100  and supplies current to the phase controllers  1100  when the genset subsystem is in Engine Start Mode. In this mode, the microcontroller manipulates the various phase control lines, such that each pair of the phase controllers  1100  sends commuted DC power to each of the three phases of the alternator. This enables the pairs of the phase controllers  1100  to run the alternator as a BLDC motor. 
       FIG.  12    is second exemplary circuit diagram of phase controllers  1200  within a motor-gen controller in a genset subsystem of a vehicle, in at least some embodiments. The phase controllers  1200  are similar to that of the phase controllers  1100  of  FIG.  11    except that the current detection circuit  1124  is replaced by a first current detection circuit  1224  and a second current detection circuit  1225 . The first current detection circuit  1224  can detect current flow through a body diode of the high-side control switch  1118  and the second current detection circuit  1225  can detect current flow through a body diode of the low-side control switch  1122 . The current detection circuits  1224  and  1225  can be implemented respectively by rectifier chips. Each rectifier chip can couple to respective drain terminal and source terminal of the control switches to determine whether the body diodes are active. The current detection circuits  1224  and  1225  can then output indication of which body diode is active to the gate control circuit  1126 . 
       FIG.  12    also illustrates a phase position output signal  1250  to the microcontroller of the genset system. The phase position output signal is labeled as “BLDC Phase Out” in  FIG.  12   . The phase position output signal is an output to the microcontroller that indicates the phase position of the alternator phase  1102  when the phase controllers  1200  are in the Generator Mode. In some embodiments, only one of the three pairs of the phase controllers  1200  has this output. For example, the “U” pair of phase controllers has this output. A voltage scaler can be used to bring a peak of the phase position output signal  1250  down to a 5V max input voltage to be used by the microcontroller. The phase position output signal  1250  can also be fed into a voltage comparator so as to send the microcontroller a square pulse whenever the alternator phase  1102  passes every 30 degrees increment of rotation. In either case, the phase position output signal  1250  allows the microcontroller to sense when the microcontroller should switch the various phase controller control links  1108  and  1110  for each pair of the phase controllers  1200  during the microcontroller-directed “Assisted Rectification Modes.” 
     7.0 Example of Diode-Based Phase Controllers 
       FIG.  22    is third exemplary circuit diagram of phase controllers  2200  within a motor-gen controller in a genset subsystem of a vehicle, in at least some embodiments. The phase controllers  2200  have similar functionalities as the phase controllers  1100  of  FIG.  11    and the phase controllers  1200  of  FIG.  12   . The phase controllers  2200  include motor bus terminals  2202 , ESC terminals  2204  (e.g., respectively coupled to the ESCs  106  of  FIG.  1   ), alternator phase terminals  2206  (e.g., respectively coupled to different phases of a permanent magnet synchronous motor, such as the alternator phase  1102  of  FIG.  11   ), or battery bus terminal  2208 . The motor bus terminals  2202  are coupled to a motor bus of the vehicle (e.g., the DC motor bus  312  of  FIG.  3   ). The motor bus terminals  2202  can couple in parallel to a three-phase rectifier circuit  2210 . The three-phase rectifier circuit  2210  can include three sets of diode pairs. The phase controllers  2200  include three relays  2212 . As illustrated in  FIG.  22   , each of the relays  2212  can be respectively coupled to the ESC terminals  2204 , respectively coupled to the alternator phase terminals  2206 , and respectively coupled to nodes between the diode pairs of the three-phase rectifier circuit  2210 . 
       FIG.  13    is a first representative circuit diagram of an augmentation controller  1300  within a motor-gen controller in a genset subsystem of a vehicle, in at least some embodiments. For example, the motor-gen controller can be the MGC  318  in the genset subsystem  300  of  FIG.  3   . The motor-gen controller can include a microcontroller, such as the microcontroller  308  of  FIG.  3   . While in some embodiments the augmentation controller  1300  can be modeled as a diode, the following first exemplary circuit diagram illustrates an embodiment of the augmentation controller that tolerates high voltage drop/wattage dissipation (e.g., 5 kA-6 kA to dissipate), whereas a diode would easily break down at the operating current of the augmentation controller  1300 , The first exemplary circuit diagram further enables detection of when the augmentation controller  1300  is active, in order to give feedback to the microcontroller. 
     The augmentation controller  1300  is coupled to a DC motor bus  1302  labeled “Vmotor,” a battery bus  1304  labeled “Vbattery,” an active indicator control link  1306  labeled “active.” The DC motor bus  1302  can be the DC motor bus  312  of  FIG.  3    or the DC motor bus  1014  of  FIG.  10   . The battery bus  1304  can be the battery bus  314  of  FIG.  3    or the battery bus  1012  of  FIG.  10   . The active indicator control link  1306  maintains a first range of voltage when the augmentation controller  1300  is active (e.g., when an electric current above a threshold, such as zero amp, is flowing from the battery bus  1304  to the DC motor bus  1302 ). The active indicator control link  1306  maintains a second range of voltage when the augmentation controller  1300  is not active. 
     A current switch  1308 , such as a transistor and more particularly a field effect transistor (e.g., metal-oxide-semiconductor field effect transistor (MOSFET)), can be coupled in between the battery bus  1304  and the DC motor bus  1302 . In some embodiments, the current switch  1308  can be a bipolar transistor, such as an insulated-gate bipolar transistor (IGBT). The current switch  1308  may include a body diode, that enables some amount of the current to flow from the battery bus  1304  to the DC motor bus  1302  when the current switch  1308  is off, but not vice versa. 
     The augmentation controller  1300  includes a current detector circuit  1310 . The current detector circuit  1310  here is illustrated as a comparator implemented by an op-amp. The comparator can detect when the body diode of the current switch  1308  is active. That is, when current is flowing from the battery bus  1304  to the DC motor bus  1302 , a voltage drop across a resistor on the battery bus  1304  can be detected by the comparator. The comparator and thus the current detector circuit  1310  can indicate activity (i.e., current flowing from the battery bus  1304 ) by maintaining a third voltage range at its output terminal. The comparator and thus the current detector circuit  1310  can indicate non-activity (i.e., no or minimal current flowing from the battery bus  1304 ) by maintaining a fourth voltage range at its output terminal. For example, the fourth voltage range is lower than the third voltage range. 
     The output of the current detector circuit  1310  feeds into a transistor driver circuit  1312 . The transistor driver circuit  1312  applies a voltage to a gate of the current switch  1308  to turn on the current switch  1308  allowing more current to flow through the current switch  1308  when the output of the current detector circuit  1310  indicates activity. 
     The output of the current detector circuit  1310  is also coupled to a timer circuit  1314 . The timer circuit  1314  also has a second terminal coupled to the active indicator control link  1306 . The timer circuit  1314  can maintain the first range of voltage at the active indicator control link  1306  when the current detector circuit  1310  indicates activity. The timer circuit  1314  can maintain the second range of voltage at the active indicator control link  1306  when the current detector circuit  1310  indicates non-activity. The timer circuit  1314  can maintain the first range of voltage at the active indicator control link  1306  when the current detector circuit  1310  switches between indicating activity and non-activity at a frequency higher than a preset threshold (e.g., around 900 Hz). For example, when the genset subsystem is operating in the Ripple Mitigation Mode, the augmentation controller  1300  and hence the current switch  1308  may be turned on and off in accordance with a frequency of the voltage ripples from the rectification process. The timer circuit  1314  presents a solid “on” state to the microcontroller even during the Ripple Mitigation Mode. 
       FIG.  14    is second exemplary circuit diagram of an augmentation controller  1400  within a motor-gen controller in a genset subsystem of a vehicle, in at least some embodiments. The motor-gen controller can include a microcontroller, such as the microcontroller  308  of  FIG.  3   . The augmentation controller  1400  is similar to the augmentation controller  1300  of  FIG.  3    except that the augmentation controller  1400  includes a rectifier chip  1410  instead of the current detector circuit  1310  of  FIG.  13   . The augmentation controller  1400  includes a DC motor bus  1402  labeled “Vmotor,” a battery bus  1404  labeled “Vbattery,” an active indicator control link  1406  labeled “active.” The DC motor bus  1402  can be the DC motor bus  312  of  FIG.  3    or the DC motor bus  1014  of  FIG.  10   . The battery bus  1404  can be the battery bus  314  of  FIG.  3    or the battery bus  1012  of  FIG.  10   . The active indicator control link  1406  is similar to the active indicator control link  1306  of  FIG.  13   . 
     A current switch  1408 , such as a transistor and more particularly a field effect transistor, can be coupled in between the battery bus  1404  and the DC motor bus  1402 . The current switch  1408  may include a body diode similar to the current switch  1408 , that enables some amount of the current to flow from the battery bus  1404  to the DC motor bus  1402  when the current switch  1408  is off, but not vice versa 
     The rectifier chip  1410  may be separately coupled to a source terminal and a drain terminal of the current switch  1408 . The rectifier chip  1410  can detect whether the body diode of the current switch  1408  is active by monitoring the source and drain terminals. If the body diode is active, the rectifier chip  1410  outputs a signal to a transistor driver circuit  1412 , similar to the transistor driver circuit  1312 , to instruct the transistor driver circuit  1412  to apply a turn-on voltage to a gate of the current switch  1408  and thus lowering the resistance from the source terminal and the drain terminal. 
     8.0 Flight Control 
       FIG.  23    is a block diagram illustrating a health monitor system  2300 , in accordance with at least some embodiments. The health monitor system  2300  can be implemented in the avionics subsystem  200 , such as in the flight controller  202 . The flight controller can receive commands from an autopilot module (e.g., the autopilot module  204  and translate those commands into signals to ESCs (e.g., the ESCs  106  of  FIG.  1   ). The flight controller can be operatively coupled to the autopilot module  204  and at least one of the ESCs  106  to control the ESC based on a command from the autopilot module  204 . In at least some embodiments, the flight controller can also implement the health monitor system  2300  to prevent and/or recover from various failure scenarios of the vehicle. 
     Without the health monitor system  2300 , the autopilot module may not realize that a failure (e.g., in the motor or other control circuitry) has occurred until the vehicle starts to lose altitude or begins to spin out of control (e.g., as exhibited by variation in orientation). In these scenarios, even a 10 millisecond heads-up to the autopilot module can enable the autopilot module to maintain altitude and recover from the failure. Absent the early warning from the health monitor system  2300 , the autopilot module may not be able to recover from the failure. 
     Failure scenarios can include damage to a propeller/rotor, damage to the bearings of the motor, electrical failures (e.g., to the ESCs), or any combination thereof. To detect these rotor scenarios, the health monitor system  2300  can couple to temperature probes  2302  (e.g., a temperature probe  2302   a  and a temperature probe  2302   b , collectively referred to as the “temperature probes  2302 ”), electrical probes  2306  (e.g., a current probe  2306   a  and voltage probe  2306   b , collectively referred to as the “electrical probes  2306 ”), and an inertial sensor  2310 . 
     For example, the temperature probe  2302   a  can be attached at or substantially adjacent to the base of a motor (e.g., the drive motor  108  of  FIG.  1   ) and the temperature probe  2302   b  can be attached at or substantially adjacent to an ESC (e.g., one of the ESCs  106 ). In some embodiments, the health monitor system  2300  can include only a single temperature probe. In some embodiments, the health monitor system  2300  can include more than two temperature probes. In some embodiments, the health monitor system can include multiple pairs of temperature probes, where each pair correspond to each pair of motor driver and ESC. The health monitor system  2300  can use the readings from the temperature probes  2302  to detect an electrical failure to at least one of the ESCs or bearing damage to at least one of the motor drivers. 
     For example, the current probe  2306   a  and the voltage probe  2306   b  can be attached to the circuitry of an ESC. The current probe  2306   a  can monitor the current usage of the ESC and detect short-circuits. The voltage probe  2306   b  can detect wiring failures (e.g., open circuits). In some embodiments, the health monitor system  2300  can include multiple pairs of electrical probes  2306 . For example, each pair can correspond to one of the ESCs  106  of  FIG.  1   . The health monitor system  2300  can use the readings from the electrical probes  2306  to detect an electrical failure at one or more of the ESCs. 
     The inertial sensor  2310  can be a sensor for detecting mechanical vibrations. For example, the inertial sensor  2310  can be an accelerometer or other type of motion sensor. The inertial sensor  2310  can be attached to or substantially adjacent to the motor driver, the rotor/propeller, the shaft of the rotor, or any combination thereof. In some embodiments, the health monitor system  2300  can include at least one inertial sensor  2310  in each set of rotor/propeller/motor. The health monitor system  2300  can use the readings from the inertial sensor  2310  to detect abnormal vibration as a precursor to an impending failure to at least one of the rotor/propeller/motor. For example, wearing of a motor bearing or damage to a rotor may result in abnormal vibration. 
     The health monitor system  2300  can send a warning message to the autopilot module in response to detecting an existing or impending failure. In response to the warning message, the autopilot module can execute precautionary measures. For example, the autopilot module can shut down one or more of the propeller/rotor/motor/ESC sets that have been detected to be failing or about to fail. For another example, the autopilot module can implement a power reduction to one or more of the propeller/rotor/motor/ESC sets that have been detected to be failing or about to fail. 
     The health monitor system  2300  can provide direct and immediate feedback to the flight controller and/or the autopilot module that a propulsion system (e.g., a set of propeller/rotor/motor/ESC) has failed. For example, the health monitor system  2300  can determine that some part of a combination of a single rotor operate, a propeller, a motor, and an ESC has failed. The health monitor system  2300  can then implement in the flight controller and/or the autopilot module&#39;s flight control configurations that enable a much more graceful recovery from the failure. 
     In several embodiments, the autopilot module and/or the flight controller can make power adjustments to the remaining propulsion systems (e.g., non-failing propulsion systems) prior to a vehicle&#39;s attitude degrading (e.g., departing from level flight, or otherwise controlled flight). This resolves the problem of the flight controller being unable to recover a degraded flight plan when failure detection relies on altitude or other flight data. The health monitor system  2300  can not only sense a propulsion failure, but also predict an impending propulsion failure (e.g., vibration detected by the inertial sensor  2310 ). The health monitor system  2300  enables the flight controller and/or the autopilot module to apply flight control laws in advance of hazardous conditions before it even occurs. This enables the vehicle to have much more time to plan for flight recovery. As an example, rather than waiting until a propulsion module fails, a flight controller and/or an autopilot module can be configured to either reduce lift power, or even shut down on or more propulsion modules in advance of catastrophic failure. These options can be activated, on a pre-cautionary basis, in response to detection of a potential or impending failure. 
     In these embodiments, the health monitor system  2300  enables a flight controller and/or an autopilot module to avoid having to make sudden (e.g., not always successful) adjustments to flight control to compensate for failures. The vehicle protected by the health monitor system  2300  can prevent secondary effects of a propulsion module (e.g., lift module) failure, which include possible onboard fire, vehicle damage due to prop/motor fragments, and/or structural damage to due vibration. 
     Referring again to  FIGS.  1 - 3    and  FIG.  23   , portions of components and/or modules associated therewith may each be implemented in the form of special-purpose circuitry, or in the form of one or more appropriately programmed programmable processors, or a combination thereof. For example, the modules described can be implemented as instructions on a tangible storage memory capable of being executed by a processor or a controller. The tangible storage memory may be volatile or non-volatile memory. In some embodiments, the volatile memory may be considered “non-transitory” in the sense that it is not transitory signal. Modules may be operable when executed by a processor or other computing device, e.g., a single board chip, application specific integrated circuit, a field programmable field array, a network capable computing device, a virtual machine terminal device, a cloud-based computing terminal device, or any combination thereof. Memory space and storages described in the figures can be implemented with the tangible storage memory as well, including volatile or non-volatile memory. 
     Each of the modules and/or components may operate individually and independently of other modules or components. Some or all of the modules may be executed on the same host device or on separate devices. The separate devices can be coupled together through one or more communication channels (e.g., wireless or wired channel) to coordinate their operations. Some or all of the components and/or modules may be combined as one component or module. 
     A single component or module may be divided into sub-modules or sub-components, each sub-module or sub-component performing separate method step or method steps of the single module or component. In some embodiments, at least some of the modules and/or components share access to a memory space. For example, one module or component may access data accessed by or transformed by another module or component. The modules or components may be considered “coupled” to one another if they share a physical connection or a virtual connection, directly or indirectly, allowing data accessed or modified from one module or component to be accessed in another module or component. In some embodiments, at least some of the modules can be upgraded or modified remotely. The systems described in the figures may include additional, fewer, or different modules for various applications. 
     One feature of particular embodiments of the disclosed technology is that they can include a set of phase controllers for rectifying multiple AC phases from an alternator into a single DC voltage. An advantage of this feature is that the phase controllers enable a bi-directional AC to DC conversion. That is, the phase controllers can convert the AC phases into the DC voltage or commutate the alternator using a DC voltage supplied from a battery. Another advantage of this feature is the ability to provide timed disconnection of the AC phases during the rectification process, allowing an external microcontroller to provide power factor correction during the rectification process. Another feature is that the embodiments include an augmentation controller. An advantage of this feature is the ability to increase DC voltage supplied to an aerial vehicle&#39;s motor bus by combining the rectified voltage output from the phase controllers and the DC voltage output of a battery. Another advantage of this feature is the ability to remove voltage ripples from the rectified voltage output from the phase controllers. Yet another feature is that the embodiments include an ICE to provide DC power to drive the rotors of a multi-rotor vehicle. An advantage of this feature is that the ICE extends the endurance of the multi-rotor vehicle by utilizing high energy density liquid fuel. 
     9.0 UAV Configurations 
       FIG.  1 B , discussed above, illustrates a representative vehicle on which power generation systems in accordance with any of  FIGS.  1 A and  2 - 14    can be installed. In further embodiments, such power generation systems can be installed on air vehicles having other configurations. For example, such power generation systems can be installed on air vehicles having a quad-rotor (rather than an octorotor) configuration. In still further embodiments, the configurations may be implemented without necessarily including power generation systems of the type described above with reference to  FIGS.  1 A and  2 - 14   , and can instead include other power generation systems. Representative configurations can provide long endurance flight in both hover and cruise modes, as well as providing robust vertical take-off and landing capabilities, and are described below with reference to  FIGS.  15 - 20   . 
       FIG.  15    illustrates an air vehicle  1500  having a fuselage  1510  that carries wings  1520  and a tail or empennage  1540 . The tail  1540  can include dual vertical stabilizers  1542  carried on corresponding tail booms  1541 , and a horizontal stabilizer  1543  extending between the vertical stabilizers  1542 . Although not shown in  FIG.  15   , the wings  1520  can include suitable leading edge devices, trailing edge devices, flaps, and/or ailerons, and the tail surfaces can include suitable control surfaces, e.g., elevator surfaces, rudders, and/or trim tabs. 
     The vehicle  1500  can include multiple propellers or rotors  1532 , including a plurality of lift rotors  1532   a  that can be used to provide the vehicle  1500  with a vertical takeoff and landing capability. Each of the lift rotors  1532   a  (four are shown in  FIG.  15   ) can be driven by a corresponding electric motor  1531 , and can be carried by a corresponding rotor boom  1533 . The motors  1531  can be powered via a power generation system  1530 . In particular embodiments, the power generation system  1530  can include a configuration generally similar to any of those described above with reference to  FIGS.  1 A and  2 - 14   , and can accordingly include an internal combustion engine coupled to an alternator, which is in turn coupled to one or more motor/generator controllers, batteries, and/or other associated features. 
     The vehicle  1500  can also include one or more additional rotors, for example, a tail-mounted pusher rotor  1532   b  and/or a nose-mounted tractor rotor  1532   c . In a particular embodiment, all of the foregoing rotors are driven by electric motors, with electrical power being supplied by the power generation system  1530 . In a relatively simple embodiment of this arrangement, each of the rotors  1532  has a fixed geometry, e.g., a fixed pitch. 
     In operation, the lift rotors  1532   a  are activated for vertical takeoff. Once the vehicle  1500  has achieved a suitable altitude, the vehicle  1500  transitions to horizontal flight. This can be accomplished by increasing the thrust provided by the aft pair of lift rotors  1532   a  and/or decreasing the thrust provided by the forward pair of lift rotors  1532   a . This procedure pitches the aircraft forward and downwardly and causes the thrust of each of the lift rotors  1532   a  to include a horizontal component. At the same time, the pusher rotor  1532   b  and tractor rotor  1532   c  are activated to provide an additional forward thrust component. As the vehicle  1500  gains speed in the forward direction, the wings  1520  provide lift. As the lift provided by the wings  1520  increases, the lift required by the lift rotors  1532   a  decreases. The transition to forward flight can be completed when the lift rotors  1532   a  are stopped (e.g., with the rotors aligned with the flight direction so as to reduce drag), while the wings  1520  provide all the necessary lift, and the tractor rotor  1532   c  and/or pusher rotor  1532   b  provide all the necessary thrust. The foregoing steps are reversed when the air vehicle  1500  transitions from forward flight to hover, and then from hover to a vertical landing. 
     In at least some embodiments, the foregoing configuration can be difficult to control during transitions between vertical and horizontal flight. In particular, when the vehicle transitions from vertical takeoff to horizontal forward flight, the vehicle pitches forward to allow the lift rotors  1532   a  to provide a thrust vector component in the forward direction. However, pitching the air vehicle  1500  forward reduces the angle of attack of the wings  1520 , thereby reducing the ability of the wings  1520  to generate lift at just the point in the process when the wings  1520  are expected to increase the lift they provide. Conversely, during the transition from forward flight to hover (in preparation for a vertical landing), the typical procedure is to cut power to any axial thrust rotors (e.g., the pusher rotor  1532   b  and/or the tractor rotor  1532   c ) and allow the vehicle air speed to decrease to the point that the lift rotors  1532   a  may be activated. The time and distance it takes for the air vehicle speed to decrease sufficiently may be difficult to predict and/or adjust for (e.g., in changing wind conditions) and can accordingly make it difficult for the aircraft to land accurately at a predetermined target, without engaging in multiple attempts. In other embodiments, described further below with reference to  FIGS.  16 - 18   , the configurations can include wing geometries that are dynamically modifiable, variable, and/or configurable to address the foregoing drawbacks. 
       FIG.  16    illustrates an air vehicle  1600  having wings  1620 , a fuselage  1610 , a tail  1640 , and a power generation system  1630 . The power generation system  1630  provides power to a tractor rotor  1632   c  and multiple lift rotors  1632   a.    
     In a particular aspect of this embodiment, the wings  1620  can be configured to change orientation and/or geometry in a manner that accounts for the different pitch attitudes of the air vehicle  1600  as it transitions between vertical and horizontal flight. In particular, each of the wings  1620  can be coupled to the fuselage  1610  with a wing joint  1621  that allows the wing  1620  to move relative to the fuselage  1610 . In a particular embodiment, the wing joint  1621  is a pivot joint and can accordingly include an axle  1623  that allows the wing  1620  to rotate relative to the fuselage  1610 , as indicated by arrows W 1  and W 2 . The pivot point can be at approximately the mid-chord location of the wing  1620  in some embodiments, and at other locations in other embodiments. Wing pivot motors  1622 , which can receive power from the power generation system  1630 , rotate the wings  1620  in the appropriate direction. 
     In operation, as the air vehicle  1600  transitions from hover to horizontal flight, the aircraft pitches forward (nose down) so that the lift rotors  1632   a  generate a thrust component along the horizontal axis, as described above with reference to  FIG.  15   . At the same time, the wings  1620  can pivot in an aft direction as indicated by arrows W 1  so as to provide and/or maintain a suitably high angle of attack, even as the fuselage  1610  pitches forward. As a result, when the tractor rotor  1632   c  is activated, the wings  1620  will provide lift more quickly than if they were fixed and pitched downwardly in the manner described above with reference to  FIG.  15   . 
     When the air vehicle  1600  transitions from forward flight to hover, the foregoing operation can be reversed. The tractor rotor  1632   c  can be stopped and, as the forward air speed decreases, the forward pair of lift rotors  1632   a  can receive more power than the aft lift rotors  1632   a . This will cause the vehicle to pitch nose up as well as providing a reverse thrust vector, so as to more quickly slow the air vehicle  1600  down. At this time, the wings  1620  can pivot forward, as indicated by arrow W 2  so as to avoid stalling despite the relatively high angle of attack of the fuselage  1610 . As a result, the vehicle  1600  can be slowed down and transitioned to hover in a quicker and more predictable manner than that described above with reference to  FIG.  15   . 
     In a particular embodiment, the empennage or tail  1640  of the air vehicle  1600  can be specifically configured to account for the variable angle of incidence of the wings  1620 . In particular, the tail  1640  can include a fixed vertical stabilizer  1642  and rotatable stabilators  1643  rather than fixed horizontal stabilizers with movable elevators. Accordingly, the angle of attack of the entire horizontal stabilizing surface can be adjusted over a wide range of angles as the fuselage  1610  pitches upwardly and downwardly during transitions from and to horizontal flight. In particular, each stabilator  1643  can be coupled to the fuselage  1610  or empennage with an axle  1644 , and can be driven by a corresponding motor (not shown in  FIG.  16   ) which is in turn powered by the power generation system  1630 . Accordingly, the stabilators  1643  can provide sufficient elevation control authority during relatively high pitch-up and pitch-down excursions of the aircraft. 
       FIG.  17    is a partially schematic, plan-view illustration of an air vehicle  1700  configured in accordance with another embodiment of the present technology. In a particular aspect of this embodiment, the air vehicle  1700  has a configuration generally similar to that described above with reference to  FIG.  16   , but lacks a tractor rotor  1632   c . Instead, the air vehicle  1700  includes lift/thrust rotors  1632   d . These rotors can have a configuration generally similar to those discussed above with reference to  FIGS.  15  and  16   , but rather than stopping during horizontal flight, the lift/thrust rotors  1632   d  can remain active during forward flight. To accomplish this result, the fuselage  1610  is pitched forward far enough to allow a component of the thrust provided by the lift/thrust rotors  1632   d  to be in a forward direction. The wings  1620  pivot aft as indicated by arrows W 1  so as to provide lift despite the downward pitch attitude of the fuselage  1610 . 
     One expected advantage of the configuration shown in  FIG.  17    is that it can eliminate the need for a tractor rotor or pusher rotor, while still providing vertical takeoff, vertical landing, and forward flight capabilities. Conversely, an expected advantage of the configuration described above with reference to  FIG.  16    is that the tractor rotor  1632   c  (and/or a pusher rotor) can produce a greater forward air speed, due to the increased forward thrust provided by such rotor(s). The speed and/or endurance of this configuration may also be increased by reducing the drag, which might otherwise result from the pitched-forward attitude of the fuselage  1710  shown in  FIG.  17   . 
     The lift rotors described above with reference to  FIGS.  15 - 17    have rotation axes (i.e., the axes about which the rotors rotate) that are fixed relative to the fuselage of the UAV. In other embodiments, the rotation axes are moveable relative to the fuselage. For example,  FIG.  18    is a partially schematic, plan-view illustration of an air vehicle  1800  having pivotable or otherwise moveable or configurable rotor pods  1834  configured in accordance with still further embodiments of the present technology. The air vehicle  1800  includes a fuselage  1810  that carries the rotor pods  1834 , in addition to wings  1820  and a tail  1840 . The rotor pods  1834  can each include pairs of lift/thrust rotors  1832   d , which receive power from a power generation system  1830  configured generally similar to those discussed above. In a particular embodiment, the air vehicle  1800  can include a tractor rotor  1832   c  (and/or a pusher rotor, not shown in  FIG.  18   ), and in other embodiments, the air vehicle  1800  does not include either a tractor rotor  1832   c  or a pusher rotor, as will be discussed further below. 
     The rotor pods  1834  and the wings  1820  are configured to be rotated independently of each other. For example, the rotor pods  1834  can be moveably coupled to the fuselage  1810  at corresponding pod joints  1837 . Each pod joint  1837  can include a pod pivot axle  1835  driven by a corresponding pod pivot motor  1836  for rotating the corresponding lift rotor pod  1834  in an aft direction (indicated by arrow P 1 ) and a forward direction (indicated by arrow P 2 ). The wings  1820  can also be pivotable. Accordingly, each wing  1820  can be coupled to the corresponding lift rotor pod  1834  with a wing joint  1821 . The wing joint  1821  can include a wing pivot axle  1823  driven by a wing pivot motor  1822  for rotating each wing  1820  relative to the lift rotor pod  1834  in an aft direction (as indicated by arrow W 1 ) and a forward direction (as indicated by arrow W 2 ). 
     In operation, the lift rotor pods  1834  and the wings  1820  can be pivoted independently of each other (e.g., in directions counter to each other) to allow a smooth transition from hover to horizontal flight and back again. In a further aspect of this embodiment, once forward flight is achieved, the lift rotor pods  1834  can be pivoted forward as indicated by arrows P 2  by about 90° so that the lift/thrust rotors  1832   d  are facing directly forward and providing all the necessary forward thrust for the air vehicle  1800 , while the wings  1820  provide the necessary lift. In such an embodiment, the tractor rotor  1832   c  can be eliminated. In still a further embodiment, the rotation of the lift rotor pods  1834  can eliminate the need for the wings  1820  to rotate, as will be described later with reference to  FIG.  19   . 
     With continued reference to  FIG.  18   , the air vehicle  1800  can include a tail  1840  having pivotable stabilators  1843  and a fixed vertical stabilizer  1842 . As discussed above with reference to  FIG.  17   , the stabilator arrangement can provide sufficient control authorities even at high pitch angles. In other embodiments, the stabilator arrangement can be replaced with a fixed horizontal stabilizer arrangement, for example, when the independent rotation of the lift rotor pods  1834  and the wings  1820  eliminates the need for high aircraft pitch angles. 
     In another embodiment, the configuration shown in  FIG.  18    can be simplified, e.g., by eliminating the wing pivot motor  122 . Further aspects of this embodiment can include combining the wing pivot axle  1823  with the pod pivot axle  1835 , so that (on each side of the fuselage  1810 ) a single axle extends from the fuselage  1810 , through the rotor pod  1834  to the wing  1820 . In yet a further aspect of this embodiment, the rotor pod  1834  then pivots freely on the axle. With this baseline configuration, the pivot motor  1836  (which was previously described as driving the rotor pod  1834 ) instead drives the wing  1820 , as indicated by arrows W 1  and W 2 . The rotational position of the rotor pod  1834  about the axle is determined by the normal dynamic lifting forces provided by the forward and aft rotors  1832   d . For example, if the aft rotor  1832   d  provides a greater lifting force than the forward rotor  1832   d , then the rotor pod  1834  will rotate (pitch) forward. For conventional lift, hover and landing maneuvers, the two lift rotors  1832   d  on each rotor pod  1834  can provide a combined lift force that maintains the air vehicle  1800  in a roughly horizontal orientation. 
     In yet a further simplification of the arrangement described immediately above, the pod pivot motor  1836  can be replaced with a releasable brake. When locked, the brake can prevent the rotor pod  1834  from rotating relative to the fuselage  1810 . When the brake is unlocked, the rotor pod  1834  can rotate freely relative to the fuselage  1810 . In either mode, the wing  1820  can remain in a fixed position relative to the fuselage  1810 . During take-off, the brake prevents the fuselage  1810  (which may be nose-heavy) from pitching forward. Once the air vehicle  1810  attains a sufficient forward speed, and/or the tractor rotor  1832   c  provides sufficient airflow over the stabilators  1843 , the stabilators  1843  can provide sufficient pitch control authority to allow the brake to be released. In one embodiment, the brake can be carried by the fuselage  1810 , and in another embodiment, the brake can be carried by the rotor pod  1834 . 
     In still another embodiment, the rotor pods  1834  can be positioned further away from the fuselage  1810 , along the length of the wings  1820 . Accordingly, the rotor pods  1834  are not connected directly to the fuselage  1810 , but are instead connected between an inboard portion of the wing  1820  and an outboard portion of the wing  1820 . In this configuration, the pods  1834  can be fixed or pivotable in accordance with any of the embodiments described above with reference to  FIG.  18   . 
       FIG.  19    illustrates an air vehicle  1900  configured in accordance with still a further embodiment of the present technology. In one aspect of this embodiment, the vehicle  1900  include wings  1920  that are fixed to a corresponding fuselage  1910 . Lift rotors  1932   a  are carried by rotor pods  1934  located at the outboard ends of the wings  1920 . The rotor pods  1934  can be rotated relative to the wing  1920  (as indicated by arrows P 1  and P 2 ) via corresponding pod pivot motors  1936  and pod pivot axles  1935 . The lift rotors  1932   a  are powered by a power generation system  1930 , which can also power an optional pusher rotor  1932   b  or tractor rotor (not shown in  FIG.  19   ). The tail  1940  can include twin booms  1941 , each carrying a vertical stabilizer  1942 , with a horizontal stabilizer  1943  carried by the vertical stabilizers  1942 . In other embodiments, the tail  1940  can have other configurations. In some configurations, the air vehicle  1900  can include a pusher rotor  1932   b , and in other configurations, the pusher rotor  1932   b  can be eliminated. 
     One potential advantage of the configuration shown in  FIG.  18    compared to that shown in  FIG.  19    is that the rotor pods are closer to the fuselage, therefore reducing the bending load on the wing. Conversely, one potential advantage of the arrangement shown in  FIG.  19    relative to that shown in  FIG.  18    is that the number of pivot joints is reduced. 
       FIG.  20    is a partially schematic, side-view illustration of an air vehicle  2000  having a movable, changeable and/or otherwise configurable lift rotor boom in accordance with another embodiment of the present technology. In one aspect of this embodiment, the air vehicle  2000  includes two lift rotor booms  2034  (one of which is visible in  FIG.  20   ), each of which carries a pair of lift rotors  2032   a . Each boom  2034  can be coupled to the fuselage  2010  with a boom joint  2037 . In a particular embodiment, the boom joint  2037  can include a boom pivot axle  2035  that allows the lift rotor boom  2034  to pivot clockwise and counter-clockwise relative to the fuselage  2010 . The air vehicle  2000  can also include a fixed wing  2020 . In a particular aspect of this embodiment, the wing  2020  has a high-wing configuration so as to increase the spacing between the wing  2020  and the boom joint  2037 . This arrangement allows the lift rotor boom  2034  to pivot through a suitable angle without interfering with the wing. 
     In operation, the lift rotor boom  2034  can be positioned (e.g., locked) in the generally horizontal orientation shown in  FIG.  20    during a vertical takeoff (and landing) maneuver. To transition to horizontal flight, the lift rotor boom  2034  pivots counter-clockwise such that the lift rotors  2032   a  are positioned to provide a forward thrust component to the air vehicle  2000 . Because the air vehicle  2000  need not pitch downwardly to place the lift rotors  2032   a  in this orientation, the wing  2020  can remain fixed relative to the fuselage  2010 . In a particular aspect of this embodiment, the air vehicle  2000  can include a tail or empennage  2040  having a vertical stabilizer  2042  and a horizontal stabilator  2043 . The stabilator  2043  (as opposed to an elevator) can provide sufficient control authority to handle pitching moments that may be caused by the moving lift rotor boom  2034 . 
     One feature of the configuration shown in  FIG.  20    is that the pivoting lift rotor boom  2034  can eliminate the need for a movable wing. As a result, the wing  2020  can provide suitable lift without changing its incidence angle. In addition, the pivot angle through which the lift rotor boom  2034  travels is sufficient to direct forward thrust from the lift rotors  2032   a  without the need for a pusher or tractor rotor. 
       FIG.  21    is a partially schematic, top isometric illustration of an air vehicle  2100  having lift rotors that can be pitched between a generally forward-facing position and a generally upward-facing position, in accordance with yet another embodiment of the present technology. In one aspect of this embodiment, the air vehicle  2100  includes a fuselage  2110 , wings  2120  extending outwardly from the fuselage  2110 , and a tail or empennage  2140  positioned aft of the wings  2120 . The empennage  2140  can include a vehicle horizontal stabilizer  2143  and a vehicle vertical stabilizer  2142 . The horizontal stabilizer  2143  can include a vehicle rudder  2145  for controlling vehicle yaw, and the horizontal stabilizer  2143  can include vehicle elevators  2144 . The vehicle elevators  2144  can be activated to control the overall pitch attitude of the air vehicle  2100 . 
     The air vehicle  2100  can further include multiple pitch rotors  2132  that can be used to lift the air vehicle  2100  and/or provide forward thrust for the air vehicle  2100 , depending on factors that include the orientation of the rotors  2132 . Accordingly, the rotational axes of the rotors  2132  can be reoriented relative to the air vehicle&#39;s direction of flight. In a particular embodiment, the rotors  2132  can be carried by corresponding rotor pods  2134 . The rotor pods  2134  can be carried toward the ends of the wings  2120 , in an embodiment shown in  FIG.  21   , and can be carried at other locations of the vehicle in other embodiments. In any of these embodiments, the rotor pods  2134  can be rotatable relative to the wings  2120  and/or the fuselage  2110  and can be coupled to the wings  2120  at corresponding pod joints  2137 . Accordingly, each rotor pod  2134  can be rotated toward a forward-facing position (as indicated by arrow F) and can be rotated in the opposite direction toward an upward-facing orientation, as indicated by arrow U. 
     The rotors  2132  can include forward rotors  2132   a  positioned forward of aft rotors  2132   b  when the corresponding rotor pod  2134  is in a generally horizontal, upward-facing position. In at least some multi-rotor aircraft, the rotor pods  2134  are rotated by increasing the force differential between the force provided by the aft rotor  2132   b  and the force provided by the forward rotor  2132   a . For example, if the aft rotor  2132   b  is powered to provide more force than the forward rotor at  2132   a , then it lifts the aft portion of the rotor pod  2134 , causing the rotor pod  2134  to rotate in the forward direction, as indicated by arrow F. To rotate the rotor pod  2134  in the opposite direction (indicated by arrow U), the force deferential is reversed, with the forward rotor  2132   a  providing more force than the aft rotor  2132   b.    
     In at least some embodiments, when the air vehicle  2100  has a significant portion of its lift provided by airflow over the wings  2120 , the available force differential between the aft rotor  2132   b  and the forward rotor  2132   a  can be relatively small. Accordingly, it can be difficult to rotate the rotor pod  2134  when the air vehicle  2100  has a significant forward velocity. To address this potential issue, embodiments of the air vehicle  2100  can include one or more pod elevators  2134  that can be actuated to change the pitch angle of the rotor pod  2134  and therefore the orientation of the rotors  2132 , even at relatively high forward air speeds. In particular, the pod elevators  2134  can rely on the relatively high forward air speed to provide the aerodynamic forces used to pitch the rotor pod  2134  in the directions indicated by arrows F and V. For example, in a representative embodiment, the rotor pods  2134  can each include a pod horizontal stabilizer  2133  that carries the pod elevator(s)  2134 . To pitch the rotor pod  2134  and rotors  2132  forward, as indicated by arrow F the pod elevators  2134  are rotated downwardly relative to the pod horizontal stabilizer  2133 , as indicated by arrow A. To rotate the rotor pod  2134  in the opposite direction, as indicated by arrow U, the pod elevators  2134  are rotated upwardly, as indicated by arrow B. 
     In one aspect of the foregoing embodiments described above with reference to  FIG.  21   , the system can include features to prevent or inhibit Dutch roll. In one embodiment, the system can include a torque tube that extends through the wings  2120  to connect the pods  2134  and synchronize the motion of the pods. In another embodiment, the pods  2134  can be locked, for example, during low speed operation (which is where Dutch roll typically occurs) to prevent or reduce Dutch roll. The pods  2134  can then be unlocked at higher speeds where Dutch roll is less likely. In still another embodiment, the elevator control can be replaced with actuators that drive the pods  2134 , generally in the manner described above with reference to  FIG.  19   . 
     One advantage of at least some of the features described above with reference to  FIG.  21    is that the pod elevator  2134  can improve the ability for the rotors  2132  to rotate at relatively high vehicle air speeds. In particular, at such air speeds, it may be difficult for the rotors to change orientation based solely on the differential force available between the forward and aft rotors  2132   a ,  2132   b.    
     One feature of several of the embodiments described above with reference to  FIGS.  15 - 20    is that they can include power generation systems that provide electric power to one or more rotors via an internal combustion engine coupled to an alternator, battery, and associated switching features. Accordingly, the foregoing power generation arrangements, features, and techniques need not be limited to octo-copters, but can instead be applied to a variety of unmanned air vehicle configurations. 
     Another feature of at least some of the foregoing configurations is that they can include one or more lift rotors in combination with one or more tractor/pusher rotors, all of which can be electrically driven, with electrical power provided by a combustion engine in combination with an alternator, battery and associated switching features. An associated feature is that electrical power can be available to any propeller or rotor at any time, independent of the flight mode of the aircraft (e.g., independent of whether the aircraft is taking off, cruising, hovering, landing or engaging in another maneuver). An advantage associated with this level of flexibility is that it can improve the smoothness, speed, and/or efficiency of transitions between one mode and another. Another advantage is that it allows the operator (human and/or automated control system) to select from multiple possible combinations of lift forces. Accordingly, the operator can select the combination that provides the desired performance characteristic for a given mission and/or portion of a mission. The performance characteristic can include endurance, speed, number of take-off and landing cycles, and/or other measures. For any of these characteristics, the ability to control what fraction of lift is provided by the wings and what fraction is provided by the lift rotors can improve the performance characteristic. For example, the configurations described above can support long endurance forward flight at speeds less than would be permissible by a fixed wing aircraft, due to the lift available from the lift rotors. The endurance can also be greater than that available with a basic quadrotor vehicle, due to the lift provided by the wings. 
     Another feature of at least some of the foregoing embodiments is that the wings can have a variable geometry and/or configuration. An advantage of this feature is that it can improve the transitions between horizontal and vertical flight, for example, by reducing the amount of time required to make the transition, by making the transition smoother, and/or by making the transition more predictable and repeatable, thus improving the accuracy with which the aircraft can be directed. Particular embodiments were described above in the context of pivoting wings, e.g., wings for which the entire chord pivots so as to change the angle of attack of the wing as opposed to conventional pivoting leading and/or trailing edges. In other embodiments the wings can have other arrangements including wing warping arrangements, and/or an arrangement of leading and/or trailing edge devices that allow the angle of attack and center of lift of the wing to be changed dynamically. The foregoing embodiments differ from conventional arrangements of deployable leading and trailing edges devices. Such conventional devices can shift the center of lift of an airfoil, but do not directly change the angle of attack of the airfoil—instead, the angle of attack of the airfoil may change as an end result of the aerodynamic forces acting on the leading and/or trailing edge devices, if those forces are not counteracted. Still further embodiments include any suitable combination of the foregoing features (e.g., variable geometry wings, variable incidence or angle of attack wings, and/or leading or trailing edge devices that vary the center of lift). Configurations in accordance with any of the foregoing embodiments can include the same or a suitable different number of vertical lift rotors, tractor rotors and/or pusher rotors. 
     The foregoing features alone and/or in combination with other features described herein, can provide several advantages when compared with existing quadrotor or quadcopter configurations. For example, conventional quadrotor UAVs that rely exclusively on electric power produced by on-board batteries typically have a relatively short range, at least in part because the lift rotors use a significant amount of power and do not take advantage of lift created by the flow of air over a fixed lifting surface (e.g., a wing). Typical fixed rotor vehicles can have a significantly limited forward flight speed and range, and, due to the power required to maintain a hover configuration, can suffer from poor hover endurance. Still further, the constraints on endurance typically limit such configurations to one takeoff and one landing cycle per battery charge. 
     Conventional hybrid quadrotors, which have a wing in addition to lift rotors, typically use electric motors for lateral motion and lift, or electric motors for lift and gas-driven motors for lateral motion. Both configurations can provide more endurance than an all-electric multi-rotor vehicle. For example, conventional hybrid quadrotors can take off and land more than once. However, such conventional hybrid quadrotors are still limited in the number of takeoff and landing cycles they can complete with the limited on-board energy supply. In addition, such vehicles can have limited endurance because the lift rotors do not contribute significantly to forward thrust during forward flight, and instead are typically stopped during forward flight. 
     Aircraft in accordance with several of the configurations disclosed herein can overcome some or all of the conventional vehicle drawbacks described above. In particular, such aircraft can achieve long endurance in a forward flight mode and long endurance in a hover mode. Such aircraft can take off and land multiple times and may therefore be suitable for missions (e.g., package delivery) that require and/or benefit from this capability. Furthermore, such vehicles can operate at slow forward speeds, e.g., below the normal wing stall speed, by using augmented lift available from the lift rotors, and/or adjusting the angle of attack of the wing such that the wing is unstalled or remains at an angle of attack below the critical angle of attack, even at a low forward speed. 
     Still further embodiments can provide additional advantages. For example, many of the configurations described herein are designed to take off and land vertically and accordingly may not include conventional landing gear. Instead, such vehicles can include skids. However, in particular embodiments, the vehicles can be configured to include wheeled landing gear or other landing gear that allow for a takeoff and/or landing roll. Normally, such vehicles would include flaps to increase lift at low speeds. Vehicles in accordance with embodiments of the present technology need not include flaps, and can instead rely on lift rotors to provide lift at a low forward speed during approach and landing. One instance in which such a capability may be advantageous is if one of the lift rotors (e.g., one of four lift rotors) fails prior to landing. In such a condition, the vehicle cannot be readily controlled in hover and in particular, the non-operational rotor reduces the available yaw authority to the point where a controlled vertical landing is difficult or impossible. However, with configurations in accordance with those described above, the remaining active lift rotors can be re-oriented (e.g., pivoted) to provide air flow over a tail surface of the vehicle to provide stability and control about the yaw axis. In addition to or in lieu of the foregoing, the variable incidence wing can allow the vehicle to land at low forward air speeds without the need for flaps. In a particular aspect of the foregoing embodiments, an additional one of the lift rotors may be deliberately stopped (e.g., so that only two lift rotors are active in a four-rotor configuration, with one rotor inactive due to a malfunction, and the other deliberately shut down) to provide for a symmetric configuration. 
     From the foregoing, it will be appreciated that specific embodiments of the disclosed technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. For example, the number of alternator AC phases may be only two phases or may be more than four phases. Certain aspects of the invention described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, the microcontroller, the augmentation controller, and the phase controllers can be combined into an integrated circuit. An individual motor and/or actuator can power multiple devices, e.g., multiple rotatable wings. Particular embodiments were described above in the context of vehicles with four lift rotors. In other embodiments, the vehicles can include more rotors, e.g., eight rotors arranged in two rows of four, or four pairs of co-axial, counter-rotating lift rotors. Aspects of the foregoing embodiments have been described generally in the context of UAVs. In other embodiments, air vehicles having configurations and/or battery augmented power systems generally similar to those described above can be used for manned flight. Further, while advantages associated with certain embodiments of the disclosed technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein.