Patent Application
20130325287
The present invention is related to propulsion systems, and in particular to a system and method for providing propulsion to a vehicle using a flywheel energy storage (FES) device.
Vehicles such as advanced military land vehicles require long-range autonomous power supplies to complete their missions in adverse ambient conditions and difficult terrains. With the changing military doctrine of terrorism, suburban warfare, and covert mission reconnaissance, the advanced unmanned ground vehicle (UGV) has come to require fully-integrated thermal power and communications. It is expected that such small UGVs can be employed in a variety of roles, such as minesweeping, explosives and chemical/biological agents detection, missile guidance, and active reconnaissance.
Unlike typical land vehicles where power is delivered to the power train continuously over long periods of time, advanced military UGVs typically operate in a “stop-and-go” pattern either probing the ground carefully for hidden mines, or checking the underbodies of parked vehicles in a busy city street for hidden items such as explosives, drugs, and chemical/biological agents. Therefore, it is desirable to provide a prime mover device that not only provides long autonomous operation, but also delivers high bursts of concentrated energy to provide torque to move the UGVs in this typical “stop-and-go” pattern.
A propulsion system includes a prime mover for providing primary power to propel a vehicle, a flywheel energy storage device for providing secondary power to propel the vehicle when primary power is not being provided, and a controller for commanding the prime mover on and off. The flywheel energy storage device stores power provided by the prime mover.
The present invention is a propulsion system primarily intended for advanced military unmanned ground vehicles (UGVs), but also applicable to a wide range of other drive systems. This invention provides primary power with a conventional prime mover such as a gas turbine, a microturbine, or an internal combustion engine. The prime mover transmits torque to a flywheel energy storage (FES) device via a one-way or two-way torque transmission shaft. The FES device comprises a flywheel and a brushless machine on a shared axis driven by the torque transmission shaft. The brushless machine (operating as a generator) allows flywheel kinetic energy to be converted into electrical energy. Electrical energy can also be discharged through the brushless machine (operating as a motor) to drive the flywheel. The shared axis of the FES connects to a propulsion driveshaft, such as a driveshaft for wheels of a ground vehicle. Thus, stored energy in the FES device can be used to propel the vehicle when the prime mover is commanded off.
Prime mover 14 is commanded on and off using controller 34 which may be implemented, for example, as a microcontroller. In the present embodiment, controller 34 includes vehicle input/output 36. Vehicle input/output 36 is implemented using any sufficient wireless communication known in the art, such as a wireless transponder. This allows remote control of vehicle 12. Controller 34 contains digital logic to receive external commands and operate the vehicle accordingly, as well as transmit data regarding current operating conditions. In a separate embodiment, controller 34 may be implemented with digital logic to autonomously control propulsion of vehicle 12. Controller 34 may also be implemented to control aspects of the vehicle such as the direction of travel, speed and other common travel variables.
When commanding prime mover 14 on, FES device 18 may be used to initiate startup. FES device 18 includes flywheel 40 for storing kinetic energy, and PM brushless machine 42. PM brushless machine 42 can operate as a generator or a motor. During startup of prime mover 14, battery 32 provides electrical energy through battery charger 30 to drive FES device 18. PM brushless machine 42 of FES device 18 is used to convert the electrical energy from battery 32 into kinetic energy to turn flywheel 40 of FES device 18. Once FES device 18 is turning, torque is transmitted to prime mover 14 through torque transmission shaft 16. In the present embodiment, torque transmission shaft 16 is a typical rigid two-way shaft. In another embodiment, torque transmission shaft 16 may be a one-way torque transmission shaft (such as a shaft-within-a-shaft construction) which transmits torque only from prime mover 14 to FES device 18, and not vice versa. If utilizing a one-way shaft, FES device 18 cannot be used to start prime mover 14.
During primary power operation in which prime mover 14 is providing power to propel vehicle 12, torque from torque transmission shaft 16 energizes FES device 18. This spins flywheel 14 up to a high revolutions per minute (RPM), such as 30,000-50,000 RPM. The greater part of the mechanical energy supplied by prime mover 14 goes through FES device 18 to step-down gear 22, and then to transaxle/gearbox 26, driveshaft 28, and wheels 24 in order to propel vehicle 12. Transaxle/gearbox 26, driveshaft 28, and UGV wheels 24 may be replaced with other drive components for applications other than ground vehicle propulsion. When prime mover 14 is transmitting torque to FES device 18, PM brushless machine 42 acts as a generator to charge battery 32 through battery charger 30. Electricity from PM brushless machine 42 may also be used to power other electronics within vehicle 12. This provides redundancy for electric energy availability between PM brushless machine 42 and battery 32.
When prime mover 14 is commanded off by controller 34, power is provided to propel vehicle 12 from FES device 18. During this time, kinetic energy stored in flywheel 40 turns FES output shaft 20. This energy goes through FES output shaft 20 to step-down gear 22, and then to transaxle/gearbox 26, driveshaft 28, and wheels 24 in order to propel vehicle 12. Battery 32 may be used to provide further energy while prime mover 14 is commanded off. In this case, battery 32 provides electrical energy through battery charger 30 to PM brushless machine 42. PM brushless machine 42 acts as a motor to provide further energy to turn FES output shaft 20. While FES device 18 is providing power and prime mover 14 is commanded off, vehicle 12 creates very little noise, which is ideal for advanced military applications.
FES device 18 can be used to propel vehicle 12 for a period of time, for example, of 4-6 minutes. This is ideal for short time duty operations such as vehicle maneuvering, stealth operations, and supplying power to communications systems, targeting systems, and navigation systems. During this time, controller 34 may also operate electromagnetic clutch 38 in order to decouple prime mover 14 from FES device 18. This removes friction, allowing for more efficient use of the energy stored in FES device 18.
In this way, the present invention describes a system and method for propelling a vehicle utilizing a flywheel energy storage device. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
