US-12617296-B2 - Hybrid powertrain system and method

US12617296B2US 12617296 B2US12617296 B2US 12617296B2US-12617296-B2

Abstract

A hybrid powertrain system and method includes a prime mover driving a generator/motor to produce an AC power output. The AC power output is applied to a rectifier which is controlled to transform the applied AC power to DC power to supply a DC Power bus at a selected voltage and current. An energy storage device is also connected to the DC power bus and the current flow between the energy storage device and the DC power bus is monitored and compared to preselected values and the results of that comparison are used to alter the operation of the rectifier to increase or decrease, as needed, the current provided to the DC power bus as electrical loads on the DC power bus change.

Inventors

Matthew McRoberts
Joseph Kinsella
John Biskey
Carl Engelmann

Assignees

PEGASUS AERONAUTICS CORPORATION

Dates

Publication Date: 20260505
Application Date: 20241216

Claims (12)

1 . An unmanned aerial vehicle comprising: at least one rotor electrically coupled to a DC power bus and operable to generate aerodynamic lift, the rotor powered by direct current from the DC power bus; and a hybrid powertrain system comprising: an energy storage device electrically coupled to the DC power bus; a prime mover operable to combust a fuel and produce a rotational output; an engine controller controlling the operating parameters of the prime mover, including at least its operating speed; a generator/motor operable, in a first state, to produce an electrical alternating current when rotated by the rotational output of the prime mover and operable, in a second state, to produce a rotational output to rotate the prime mover when provided with an electrical alternating current input; an active rectifier operable in a first state to convert the electrical alternating current produced by the generator/motor into the direct current at a selected voltage and to provide that direct current to the DC power bus and operable in a second state to invert direct current energy provided from the energy storage device into an alternating current which can be provided to the generator/motor; and a generator control unit operable to select the state of the active rectifier and to select the voltage of the direct current provided to the DC power bus; wherein the operation of the prime mover can be suspended for a selected period of time, during which power is supplied to the DC power bus from the energy storage device, after which alternating current power, inverted from the direct current power from the energy storage device by the active rectifier, is applied to the generator/motor to rotate the prime mover and the engine controller operates to restart the prime mover.
2 . The unmanned aerial vehicle of claim 1 wherein the energy storage device is a battery.
3 . The unmanned aerial vehicle of claim 1 wherein the generator control unit monitors the flow of direct current between the DC power bus and the energy storage device when the active rectifier is in the first state and adjusts the operation of the active rectifier to select an output voltage such that the monitored current flow is substantially the same as a preselected target current flow.
4 . The unmanned aerial vehicle of claim 3 wherein, in response to a command received when the prime mover is not operating, the generator control unit is operable to place the active rectifier into the second state to invert direct current power from the energy storage device to an alternating current energy provided to the generator/motor causing the generator/motor to rotate the prime mover and the engine controller operating to start the prime mover.
5 . The unmanned aerial vehicle of claim 1 wherein at least two electrical loads are supplied from the DC power bus, a first electrical load comprising the at least one rotor and a second electrical load comprising a camera.
6 . The unmanned aerial vehicle of claim 1 wherein, after restarting the prime mover, the active rectifier operates in the first state to convert alternating current produced by the generator/motor to direct current provided to the DC power bus.
7 . The unmanned aerial vehicle of claim 3 wherein the preselected target current flow is set to a value required to substantially recharge the energy stored in the energy storage device within a selected timeframe.
8 . The unmanned aerial vehicle of claim 1 wherein the unmanned vehicle is a multi-rotor unmanned aerial vehicle.
9 . The unmanned aerial vehicle of claim 8 wherein the unmanned aerial vehicle is a tilt-wing unmanned aerial vehicle.
10 . The unmanned aerial vehicle of claim 1 wherein the prime mover is mechanically decoupled from the remainder of the structure of the unmanned aerial vehicle.
11 . The unmanned aerial vehicle of claim 1 wherein the prime mover is a two stroke engine.
12 . The unmanned aerial vehicle of claim 1 wherein the prime mover is operated at a constant speed.

Description

RELATED APPLICATIONS This application is continuation of U.S. patent application Ser. No. 18/208,251 (filed on Jun. 9, 2023), entitled “HYBRID POWERTRAIN SYSTEM AND METHOD”, which is a continuation of U.S. patent application Ser. No. 17/464,184 (filed Sep. 1, 2021), which is a continuation of U.S. patent application Ser. No. 16/946,155 (filed Jun. 8, 2020), which is a continuation of U.S. patent application Ser. No. 16/324,268 (filed on Feb. 8, 2019), which is a national phase entry application of PCT Application No. PCT/IB2017/054886 (filed Aug. 10, 2017), which claims priority from U.S. Provisional Patent Application No. 62/372,956 (filed on Aug. 10, 2016), entitled, “Systems And Methods For Hybrid Power Distribution Using Battery Measurement Current Control”. The entire contents of these applications are herein incorporated by reference. FIELD OF THE INVENTION The present invention relates to a powertrain system and a method of operating the same. More specifically, the present invention relates to a hybrid powertrain system including a prime mover and an electrical generator to power a variable load. BACKGROUND OF THE INVENTION In many applications, the use of electric motors represents a simple and effective method for delivering mechanical power for traction and/or propulsion systems. This is especially the case for devices such as small-scale single-rotor and multi-rotor unmanned aerial vehicles (“UAVs”). A variety of energy storage methods have been used to provide the power necessary for electric motor driven traction and propulsion applications and examples include, but are not limited to: petrol-electric or diesel-electric powertrains; turbine-electric powertrains; and batteries. In petrol-electric and diesel-electric powertrains, a prime mover combusts petroleum based fuel (typically liquid) to create mechanical energy and that mechanical energy is then converted to electricity by a generator driven by the mechanical energy. Such systems are commonplace in marine, freight, and industrial applications and are commonly used in applications where the electrical load is relatively constant, and the load response of the generator set has little effect on the proper operation of the vehicle. Turbine-electric powertrains represent a similar method of operation as petrol-electric and diesel-electric powertrains, but implement a gas turbine as the prime mover. In other applications, such as electric UAV applications, batteries are most commonly employed due to their ease of use and, with certain battery chemistries with high discharge capabilities, their ability to supply large amounts of power and rapidly meet a variable power demand. Systems such as UAVs can have rapidly changing electrical load requirements which the powertrain must be able to accommodate for proper operation and this is especially true for UAVs, where the vehicle is inherently unstable and relies on the rapid response of the powertrain to stay airborne and stable and batteries have been the preferred power system solution. Despite these advantages, several problems exist with the use of batteries as the energy source in a powertrain system. For example, batteries are typically manufactured with specific chemistries that are a compromise between energy density, capacity, expected lifetime (rechargability and robustness), weight, safety (flammability, chemical reactivity), expense, expected operating temperature range, etc. In particular, even the best currently available batteries offer a very low gravimetric energy density relative to most combustion fuels. Using UAV platforms as an example, the low gravimetric energy density of even the best (and often most expensive) batteries unduly limit payload capacities and flight times, making UAVs unusable in applications for which they would otherwise be well suited. Similar problems exist with the use of batteries in the automotive field, for example the range of Tesla™ battery powered vehicles is generally much less than comparable vehicles powered by combustion engines. Prior attempts to address the limitations of battery powered powertrains have included hybrid powertrain systems which employ a combination of batteries and combustion fuel energy sources. In hybrid powertrain systems, a battery is combined with an electric generator and combustion engine. There are a variety of operating strategies for such hybrid powertrain systems, but to some extent, all of these strategies involve operating the combustion engine to produce an electric power output that can then be applied to electric drive motors in combination with the output of the battery, or to directly recharge the battery. Because these powertrains use the generator as a complement to the battery system, the batteries in these systems are recharged and discharged frequently and are often responsible for meeting all (or most) of the vehicle's power demands for a significant period of time. This necessitates a battery with a very