DISPLACEMENT CONTROL HYDROSTATIC PROPULSION SYSTEM FOR MULTIROTOR VERTICAL TAKE OFF AND LANDING AIRCRAFT
A hydraulic propulsion system is disclosed. The system includes one or more input interfaces configured to receive mechanical power from a power source, four or more variable displacement pumps coupled to the one or more input interfaces adaptable to generate a controlled variable quantity of fluid to be pumped out of each of the variable displacement pumps in response to a control input from a corresponding control interface, and four or more positive displacement motors each fluidly coupled to a corresponding variable displacement pump and configured to receive the pumped fluid, wherein each motor is configured to be mechanically coupled to one or more aerodynamic rotors of a multi-rotor vertical take-off and landing aircraft to control thrust and attitude.
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The present patent application is related to and claims the priority benefit of U.S. Provisional Patent Application Ser. No. 62/571,183 filed Oct. 11, 2017, U.S. Provisional Patent Application Ser. No. 62/571,192 filed Oct. 11, 2017, and a counterpart international application to be filed the same day as the present disclosure having the title Aviation Hydraulic Propulsion System Utilizing Secondary Controlled Drives, the contents of each of which are hereby incorporated by reference in their entirety into the present disclosure.
TECHNICAL FIELDThe present disclosure relates to a hydraulic propulsion system for rotary-wing aircrafts.
BACKGROUNDThis section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
Multi-rotor vertical take-off and landing (VTOL) aircrafts are becoming commonplace. These VTOL aircrafts have to be equipped with a minimum of four independently controlled rotors to control motion of the aircraft including pitch, roll, and yaw as well as attitude and translational motion without inclusion of any other motion controlling device. Two important limitations associated with these aircrafts include weight and ability to independently control each rotor. Various propulsion systems are used, such as electrical, mechanical, and electromechanical. However, each suffer from excessive weight and/or lack of responsiveness limiting their utility. In particular, in order to dynamically control each rotor independently so that a desired attitude can be achieved for the aircraft, a number of complicated devices are typically used which are both heavy and require constant maintenance.
Therefore, there is an unmet need for a novel approach for propulsion of VTOL aircrafts.
SUMMARYA hydraulic propulsion system is disclosed. The system includes one or more input interfaces configured to receive mechanical power from a power source, four or more variable displacement pumps coupled to the one or more input interfaces adaptable to generate a controlled variable quantity of fluid to be pumped out of each of the variable displacement pumps in response to a control input from a corresponding control interface, and four or more positive displacement motors each fluidly coupled to a corresponding variable displacement pump and configured to receive the pumped fluid. Each motor is configured to be mechanically coupled to one or more aerodynamic rotors of a multi-rotor vertical take-off and landing aircraft to control thrust and attitude.
According to one embodiment of the system, the power source is one or more internal combustion engines.
According to one embodiment of the system, the power source is one or more electric motors.
According to one embodiment of the system, the power source is one or more turbine engines.
According to one embodiment of the system, the positive displacement motors are fixed displacement motors.
According to one embodiment of the system, the positive displacement motors are variable displacement motors adapted to further change the rotor speed for the corresponding pump fluid flow and wherein the motor displacement is controlled by a motor displacement control device which is one of an electro-hydraulic displacement control device, mechanical displacement control device, electro-mechanical displacement control device, and a combination thereof.
According to one embodiment of the system, the quantity of fluid to be pumped out of each of the variable displacement pumps is controlled by a pump displacement control device which is one of an electro-hydraulic displacement control device, mechanical displacement control device, electro-mechanical displacement control device, and a combination thereof.
According to one embodiment of the system, the control input is provided from one of a flight control computer, a pilot, and a combination thereof.
According to one embodiment of the system, the system further includes a flight control computer coupled to each of the variable displacement pumps and configured to control the quantity of fluid to be pumped from each.
According to one embodiment of the system, the system is further configured to receive a signal corresponding to the speed of each motor and to provide the speed information as speed feedback signals to the flight control computer.
According to one embodiment of the system, the system further includes a closed-loop control arrangement using the speed feedback signals.
According to one embodiment of the system, the system is further configured to receive a signal corresponding to the displacement of each positive displacement motors and to provide the displacement information as displacement feedback signals to the flight control computer.
According to one embodiment of the system, the system further includes a closed-loop control arrangement using the displacement feedback signals.
According to one embodiment of the system, the flight control computer further configured to receive signals corresponding to one or more of position, attitude, and motion of the aircraft and control fluid flow from the variable displacement pumps accordingly to achieve a desired position, attitude and motion of the aircraft.
According to one embodiment of the system, the system further includes a charge pump adapted to provide power for the pump displacement control device.
According to one embodiment of the system, the system further includes a fluid cooling device adapted to cool fluid used therein.
According to one embodiment of the system, the variable displacement pumps are coupled to each other in series manner.
According to one embodiment of the system, the variable displacement pumps are coupled in pairs in a series manner, and each pair is coupled to at least one other pair in a parallel manner.
According to one embodiment of the system, each pair is coupled to a dedicated power source.
According to one embodiment of the system, each pair is coupled to the one or more input interfaces.
According to one embodiment of the system, the one or more input interfaces is a gearbox.
According to one embodiment of the system, each pair is coupled to a dedicated input interface which is coupled to a dedicated power source.
According to one embodiment of the system, the fluid is a compressible fluid.
According to one embodiment of the system, the compressible fluid is air.
According to one embodiment of the system, the fluid is an incompressible fluid.
According to one embodiment of the system, the incompressible fluid is one of hydraulic oil, water, fuel, antifreeze, and a combination thereof.
For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended.
In the present disclosure, the term “about” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range.
In the present disclosure, the term “substantially” can allow for a degree of variability in a value or range, for example, within 90%, within 95%, or within 99% of a stated value or of a stated limit of a range.
The propulsion system according to the present disclosure is related to a family of multi-rotor aircrafts that include at least four rotors which are independently speed controlled. The propulsion system according to the present disclosure is used to control the different speeds of a minimum of four rotors to achieve motion in pitch, roll, and yaw directions as shown in
The propulsion system according to the present disclosure utilizes at least four hydrostatic transmissions to distribute and transmit mechanical power from a power source (e.g., single or multiple internal combustion engines, or turbine engines, or electric motors) to the rotors (which can be single or multiple propellers, fans, or compressors). Each hydrostatic transmission contains a variable displacement hydraulic pump, at least one fixed or variable displacement motor, and the pipes and hoses that connect the pump and the motor. The rotor speed is controlled by the displacement of the pump. The displacement of the pump is controlled by a control arrangement including electrical, mechanical, electromechanical, hydraulic, electrohydraulic, mechanical-hydraulic actuators, by human power through appropriate linkages, or any combination thereof, further described below.
This hydrostatic propulsion system of the present disclosure is configured to control the speed of each individual rotor with faster response and lower weight in comparison with prior art propulsion system counterpart owing to the bandwidth of the displacement control and the compactness of hydraulic units. As a result, a more stable flight and more useful payload capability can be achieved. The reliability of the aircraft increases due to the highly reliable nature of hydraulic systems. Furthermore, the aircraft power source (e.g., internal combustion engine) can be arranged to run at relatively constant speed, which extends the lifetime of such power source. Furthermore, since hydraulic components are made of metal, the propulsion system of the present disclosure can be made with less cost and is further readily recyclable.
The present disclosure is related to a counterpart application to be filed the same day as the present disclosure having the title Aviation Hydraulic Propulsion System Utilizing Secondary Controlled Drives. The difference between the present disclosure and this counterpart application lies in control strategies. In the present disclosure the control scheme is based on primary or displacement control in which the hydraulic propulsion system controls the rotational speed of the hydraulic motor by changing the pump displacement. As such, the motors can be fixed displacement or variable displacement. In case of using variable displacement motor, the motor displacement changes only to assist the pump to achieve improved overall performance. In the displacement control hydraulic propulsion system of the present disclosure, the bandwidth of the thrust is substantially determined by the bandwidth of the pump. According to the present disclosure, in order to control four propeller speeds independently, at least 4 pumps and 4 motors are required for the displacement control hydraulic propulsion system. In contrast, the disclosure found in the counterpart application is based on a secondary control hydraulic propulsion system which controls the output (i.e., speed of the propellers) by changing the motor displacement. As such, the pumps can be fixed displacement or variable displacement. In case of using fixed displacement pump, the system pressure is adjusted by utilizing a valve network. In case of using variable displacement pump, the pump displacement changes to adjust the system pressure. In the secondary control hydraulic propulsion system, the bandwidth of the thrust is substantially determined by the bandwidth of the motor. In case of multiple motors, each motor speed can be controlled independently. Therefore, in order to control, e.g., 4 propeller speeds independently, at least 1 pump and 4 motors are required for the secondary control hydraulic propulsion system. Comparing to the counterpart application, the present disclosure benefits from the control strategy simplicity and the lightweight owing to the fixed displacement motors.
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The propulsion system according to the present disclosure can also have more than four rotors. Schematics of exemplary embodiments with 6 and 8 rotors are shown in
Besides the arrangements shown in
In another embodiment, according to the present disclosure, with reference to
In yet another embodiment, according to the present disclosure, with reference to
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It should be appreciated that each motor described herein can be a fixed or variable displacement motor. In the variable displacement embodiments of the motor, the displacement of the motor is changed in order to further change the rotor speed based on the corresponding pump flow.
Those having ordinary skill in the art will recognize that numerous modifications can be made to the specific implementations described above. The implementations should not be limited to the particular limitations described. Other implementations may be possible.
Claims
1. A hydraulic propulsion system, comprising:
- one or more input interfaces configured to receive mechanical power from a power source; four or more variable displacement pumps coupled to the one or more input interfaces adaptable to generate a controlled variable quantity of fluid to be pumped out of each of the variable displacement pumps in response to a control input from a corresponding control interface; and four or more positive displacement motors each fluidly coupled to a corresponding variable displacement pump and configured to receive the pumped fluid, wherein each motor is configured to be mechanically coupled to one or more aerodynamic rotors of a multi-rotor vertical take-off and landing aircraft to control thrust and attitude.
2. The system of claim 1, wherein the power source is one or more internal combustion engines.
3. The system of claim 1, wherein the power source is one or more electric motors.
4. The system of claim 1, wherein the power source is one or more turbine engines.
5. The system of claim 1, wherein the positive displacement motors are fixed displacement motors.
6. The system of claim 1, wherein the positive displacement motors are variable displacement motors adapted to further change the rotor speed for the corresponding pump fluid flow and wherein the motor displacement is controlled by a motor displacement control device which is one of an electro-hydraulic displacement control device, mechanical displacement control device, electro-mechanical displacement control device, and a combination thereof.
7. The system of claim 1, wherein the quantity of fluid to be pumped out of each of the variable displacement pumps is controlled by a pump displacement control device which is one of an electro-hydraulic displacement control device, mechanical displacement control device, electro-mechanical displacement control device, and a combination thereof.
8. The system of claim 1, wherein the control input is provided from one of a flight control computer, a pilot, and a combination thereof.
9. The system of claim 1, further comprising a flight control computer coupled to each of the variable displacement pumps and configured to control the quantity of fluid to be pumped from each.
10. The system of claim 9, further configured to receive a signal corresponding to the speed of each motor and to provide the speed information as speed feedback signals to the flight control computer.
11. The system of claim 10, further comprising a closed-loop control arrangement using the speed feedback signals.
12. The system of claim 10, further configured to receive a signal corresponding to the displacement of each positive displacement motors and to provide the displacement information as displacement feedback signals to the flight control computer.
13. The system of claim 12, further comprising a closed-loop control arrangement using the displacement feedback signals.
14. The system of claim 10, the flight control computer further configured to receive signals corresponding to one or more of position, attitude, and motion of the aircraft and control fluid flow from the variable displacement pumps accordingly to achieve a desired position, attitude and motion of the aircraft.
15. The system of claim 7, further comprising a charge pump adapted to provide power for the pump displacement control device.
16. The system of claim 1, further comprising a fluid cooling device adapted to cool fluid used therein.
17. The system of claim 1, wherein the variable displacement pumps are coupled to each other in series manner.
18. The system of claim 1, wherein the variable displacement pumps are coupled in pairs in a series manner, and each pair is coupled to at least one other pair in a parallel manner.
19. The system of claim 18, wherein each pair is coupled to a dedicated power source.
20. The system of claim 18, wherein each pair is coupled to the one or more input interfaces.
21. (canceled)
22. (canceled)
23. The system of claim 1, wherein the fluid is a compressible fluid.
24. The system of claim 23, wherein the compressible fluid is air.
25. The system of claim 1, wherein the fluid is an incompressible fluid.
26. The system of claim 24, wherein the incompressible fluid is one of hydraulic oil, water, fuel, antifreeze, and a combination thereof.
Type: Application
Filed: Oct 8, 2018
Publication Date: Jun 24, 2021
Applicant: Purdue Research Foundation (West Lafayette, IN)
Inventors: Lizhi SHANG (West Lafayette, IN), Monika IVANTYSYNOVA (West Lafayette, IN)
Application Number: 16/755,526