Microwave wireless energy transmission system for unmanned aerial vehicle wireless power supply and test method

Abstract

The invention discloses a microwave wireless energy transmission system for unmanned aerial vehicle wireless power supply and a test method. The test method comprises the following steps: calibrating the irradiation power density of a space where a rectification antenna array is located; testing the direct-current output power of the rectification antenna array under a static condition, and calculating the rectification efficiency of the rectification antenna sub-array; in the continuous flight process of the unmanned aerial vehicle, the direct current output power of the rectification antenna array and the direct current output power of the central rectification antenna sub-array are tested, and the average value of the direct current output power of the rectification antenna array and the rectification efficiency of the central rectification antenna sub-array are calculated. The system comprises a ground suspension experiment platform used for calibrating irradiation power density and testing rectification antenna array output direct current power and an energy transfer flight experiment platform used for testing rectification antenna array output direct current power and center rectification antenna subarray direct current output power in the flight process. The invention realizes long-time microwave energy irradiation for the rectification antenna array, and is suitable for high-power microwave wireless energy transmission of a moving target.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and relates to a microwave wireless power transmission system and a test method for wireless power supply to drones. Background Art

[0002] For long-endurance flight, a drone needs to carry enough fuel or a large enough battery to ensure reliable execution of its flight mission. To meet the flight requirements, the weight of the fuel or battery carried by the drone is relatively large. When the fuel or battery runs out, the drone needs to land for refueling or charging to replenish energy, which is difficult to meet the needs of its long-endurance flight. With the rapid development of wireless energy transmission technology, microwave wireless power transmission has become an energy transmission method with broad application prospects. It has the characteristics of long transmission distance, large transmission power, flexible direction, etc. These characteristics can be used to provide continuous energy supply for drones, reduce the weight of the drone's energy system, and continuously provide electrical energy for the electrical equipment on the drone.

[0003] The microwave wireless power transmission system can be divided into two parts: a transmitting system and a receiving system. The transmitting system consists of a microwave source, a transmitting antenna, a control system, etc. Due to its high power capacity, high gain, and low cost, a reflector antenna is often used as the transmitting antenna in the microwave wireless power transmission system; while the receiving system consists of a rectenna array, a drone, a power acquisition device, etc. The rectenna array is attached to the drone's web to achieve conformal of the rectenna array and the drone.

[0004] However, in the microwave wireless power transmission system, the traditional microwave wireless power transmission system has a low transmitting power, usually from dozens of watts to hundreds of watts. If high-power power transmission is to be carried out, requirements are put forward for the power capacity of the equipment, and a system suitable for high-power microwave power transmission and its test scheme need to be designed; at the same time, the traditional microwave wireless power transmission system usually transmits energy to stationary targets. As a moving target, the traditional microwave wireless power transmission system can no longer meet the needs. Therefore, a microwave wireless power transmission system and its test method applicable to the case of moving targets need to be designed. Summary of the Invention

[0005] The present invention aims to solve the technical problem that the microwave wireless power transmission system in the prior art can only transmit energy to stationary targets. The present invention provides a microwave wireless power transmission system and a test method for wireless power supply to drones, and the technical solution adopted is:

[0006] A microwave wireless power transmission test method for wireless power supply to drones, including the steps of:

[0007] S1. Calibrate the irradiation power density in the space where the rectenna array is located;

[0008] S2. Test the DC output power of the rectenna array under static conditions, calculate the DC output power density of the rectenna sub-array, and calculate the rectification efficiency of the rectenna sub-array according to the DC output power density of the rectenna sub-array and the illumination power density;

[0009] S3. Based on the rectification efficiency of the rectenna sub-array, test the DC output power of the rectenna array during the continuous flight of the UAV, and calculate the average value of the DC output power of the rectenna array;

[0010] S4. Test the DC output power of the central rectenna sub-array during the continuous flight of the UAV, calculate the average value of the DC output power of the central rectenna sub-array and the DC output power density of the central rectenna sub-array, calculate the rectification efficiency of the central rectenna sub-array according to the DC output power density of the central rectenna sub-array and the illumination power density, and evaluate the effect of microwave wireless power transmission by combining the average value of the DC output power and the rectification efficiency of the central rectenna sub-array.

[0011] In one embodiment of the present invention, the step S1 includes:

[0012] S11. Build a ground suspension experimental platform for the rectenna array;

[0013] The ground suspension experimental platform for the rectenna array includes a ground microwave transmission system and a receiving antenna system;

[0014] The ground microwave transmission system includes a microwave transmitter, a water cooling device, a control host computer, and a reflector antenna. The microwave transmitter is respectively connected to the reflector antenna, the water cooling device, and the control host computer;

[0015] The receiving antenna system includes a receiving antenna unit and a power probe. An SMA interface is provided on the receiving antenna unit, and the SMA interface is connected to the power probe. The received power data is transmitted to the control host computer through the LAN port on the power probe;

[0016] S12. Calculate the illumination power density at different height positions and calibrate the illumination power density.

[0017] In one embodiment of the present invention, the step S12 includes:

[0018] Assume that the input power of the reflector antenna is P t , and the gain is G t . The maximum radiation direction points to the receiving antenna unit at a distance of r. The illumination power density ρ at the receiving antenna unit is expressed as:

[0019]

[0020] Assume that the gain of the receiving antenna unit is G r , the wavelength at the operating frequency point is λ, and the maximum radiation direction also points to the reflector antenna. The maximum received power of the receiving antenna unit is expressed as:

[0021]

[0022] In Formulas (1) and (2), P t is the input power of the reflector antenna, G t is the gain of the reflector antenna, G r is the gain of the receiving antenna unit, λ is the wavelength at the operating frequency point, ρ is the irradiation power density at the receiving antenna unit, and P r is the maximum received power of the receiving antenna unit;

[0023] Calculate the irradiation power density at different height positions through the received power of the receiving antenna unit.

[0024] In one embodiment of the present invention, the step S2 includes:

[0025] Replace the receiving antenna unit with a rectenna array, test the DC output power of the rectenna array under static conditions, calculate the DC output power density according to the area of the rectenna sub-array, and calculate the rectification efficiency of the rectenna sub-array at different input powers according to the DC output power density of the rectenna sub-array and the irradiation power density. The rectification efficiency of the rectenna sub-array at different input powers is expressed as:

[0026]

[0027] In Formula (3), ρ is the DC output power density of the rectenna sub-array, and ρ 照射 is the calibrated irradiation power density.

[0028] In one embodiment of the present invention, the method for testing the DC output power of the rectenna array in the step S2 includes:

[0029] Connect a large ground power resistor box to the output end of the rectenna array with a wire, record the voltage on the resistor box, after measuring a set of data, change the resistance value of the resistor box, and test again to obtain the voltage and current conditions of the rectenna array at different load resistance values, and calculate the DC output power according to the voltage and the current.

[0030] In one embodiment of the present invention, the step S3 includes:

[0031] S31. Build a power transmission flight experiment platform;

[0032] The ground microwave transmission system is installed on a vehicle platform. The rectifying antenna array is attached to the web of the unmanned aerial vehicle (UAV). The output end of the rectifying antenna array is connected to a load on the UAV, and a data acquisition module is installed at the output end of the rectifying antenna array. The data acquisition module is used to transmit the energy data received by the UAV back to the control host computer;

[0033] S32. During the continuous flight of the UAV, test the DC output power of the rectifying antenna array to obtain the average value of the DC output power for continuous energy transfer.

[0034] In one embodiment of the present invention, the step S32 includes:

[0035] Measure the voltage and current at the power input end of the ground microwave transmission system with a multimeter to obtain the input power of the ground microwave transmission system, and combine the microwave conversion efficiency to obtain the power value of the microwave emission source;

[0036] Examine the time history data of the output current of the reflector antenna recorded by the on-board recorder. According to the output data of the on-board recorder, calculate the DC output power of the rectifying antenna array to obtain a graph of the DC output power of the rectifying antenna array changing with time. Process the data in the graph to obtain the average value of the DC output power of the rectifying antenna array.

[0037] In one embodiment of the present invention, the step S4 includes:

[0038] Collect the DC output current of the central rectifying antenna sub-array and the connected load resistance value, and calculate the DC output power of the central rectifying antenna sub-array;

[0039] Intercept a section of data of the central rectifying antenna sub-array for processing and drawing to obtain a graph of the DC output power of the central rectifying antenna sub-array changing with time, and calculate the average value of the DC output power of the central rectifying antenna sub-array;

[0040] Calculate the DC output power density of the central rectifying antenna sub-array from the average value of the DC output power of the central rectifying antenna sub-array and the area of the central rectifying antenna sub-array to obtain the DC output power density of the central rectifying antenna sub-array;

[0041] Compare the DC output power density of the central rectifying antenna sub-array with the calibrated value of the irradiation power density, and calculate the rectification efficiency of the central rectifying antenna sub-array. The formula is expressed as:

[0042]

[0043] In formula (4), ρ 中心 is the DC output power density of the central rectifying antenna sub-array, ρ 照射is the calibrated value of the irradiation power density;

[0044] Process the data to obtain the graphs of the DC output power density and rectification efficiency of the central rectenna sub-array varying with time.

[0045] A microwave wireless power transfer system for wireless power supply to drones, used to implement the microwave wireless power transfer test method for wireless power supply to drones, includes:

[0046] A ground suspension experimental platform, used to calibrate the irradiation power density in the space where the rectenna array is located and test the DC output power of the rectenna array under static conditions;

[0047] A power transfer flight experimental platform, used to test the DC output power of the rectenna array and the DC output power of the central rectenna sub-array during the continuous flight of the drone.

[0048] In an embodiment of the present invention, the ground suspension experimental platform includes a ground microwave transmission system and a receiving antenna system;

[0049] The ground microwave transmission system includes a microwave transmitter, a water cooling device, a control host computer, and a reflector antenna. The microwave transmitter is respectively connected to the reflector antenna, the water cooling device, and the control host computer;

[0050] The receiving antenna system includes a receiving antenna unit, a rectenna array, and a power probe. SMA interfaces are provided on the receiving antenna unit and the rectenna array. The SMA interfaces are connected to the power probe, and the received power data of the receiving antenna unit and the rectenna array are transmitted to the control host computer through the LAN port on the power probe;

[0051] On the basis of the ground suspension experimental platform, the power transfer flight experimental platform further includes a vehicle platform, a drone, and a data acquisition module;

[0052] The microwave transmitter is installed on the vehicle platform. The rectenna array is attached to the belly of the drone. The output end of the rectenna array is connected to the load of the drone, and a data acquisition module is installed at the output end of the rectenna array. The data acquisition module is used to transmit the energy data received by the drone back to the control host computer.

[0053] Advantages of the present invention:

[0054] 1. The microwave wireless power transfer test method for unmanned aerial vehicle (UAV) wireless power supply according to the present invention is based on the Friis transmission formula. By using a receiving antenna unit and a rectenna sub-array, the irradiation power density of the space where the rectenna is located is calibrated at different power transfer distances with low power, laying a foundation for subsequent testing of the rectification efficiency of the rectenna. A high-power ground microwave transmitting system is designed, which can achieve long-term high-power microwave output on the basis of ensuring safe operation. This microwave transmitting system can irradiate microwave energy on the rectenna array for a long time, providing practical guidance for a high-reliability high-power microwave wireless power transfer experimental platform. On the basis of the ground suspension experiment, the present invention designs a power transfer flight experimental platform, which can provide practical guidance for the high-power microwave wireless power transfer experiment of moving targets.

[0055] 2. The microwave wireless power transfer system for UAV wireless power supply according to the present invention builds a power transfer flight experimental platform on the basis of the ground suspension experiment. The ground transmitting system is mounted on a vehicle platform, and the rectenna array is attached to the UAV's web. When the vehicle is driving on the runway, the UAV follows and flies at a certain height above it and continuously receives microwave energy. This power transfer flight experimental platform can transfer power to moving target devices. Brief Description of the Drawings

[0056] Figure 1 is a flowchart of the microwave wireless power transfer test method for UAV wireless power supply provided by an embodiment of the present invention;

[0057] Figure 2 is a graph of the DC output power of the rectenna array at different power transfer distances provided by an embodiment of the present invention;

[0058] Figure 3 is a schematic diagram of vehicle-mounted tracking power transfer provided by an embodiment of the present invention;

[0059] Figure 4 is a graph of the variation of the DC output power of the rectenna array with time provided by an embodiment of the present invention;

[0060] Figure 5 is a graph of the variation of the DC output power of the central rectenna sub-array with time provided by an embodiment of the present invention;

[0061] Figure 6 is a graph of the variation of the DC output power density and rectification efficiency of the central rectenna sub-array with time provided by an embodiment of the present invention. Detailed Embodiments

[0062] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0063] The present invention provides a microwave wireless power transfer test method for unmanned aerial vehicle (UAV) wireless power supply, which can be used for high-power microwave wireless power transfer and can analyze and calculate the rectification efficiency of a rectenna sub-array and the DC output power of a rectenna array. Referring to the attached Figure 1 , the microwave wireless power transfer test method for UAV wireless power supply includes the following steps:

[0064] S1. Calibrate the irradiation power density in the space where the rectenna array is located;

[0065] S2. Test the DC output power of the rectenna array under static conditions, calculate the DC output power density of the rectenna sub-array, and calculate the rectification efficiency of the rectenna sub-array according to the DC output power density and the irradiation power density of the rectenna sub-array;

[0066] S3. Based on the rectification efficiency of the rectenna sub-array, test the DC output power of the rectenna array during the continuous flight of the UAV and calculate the average value of the DC output power of the rectenna array;

[0067] S4. Test the DC output power of the central rectenna sub-array during the continuous flight of the UAV, calculate the average value of the DC output power of the central rectenna sub-array and the DC output power density of the central rectenna sub-array, calculate the rectification efficiency of the central rectenna sub-array according to the DC output power density and the irradiation power density of the central rectenna sub-array, and evaluate the effect of microwave wireless power transfer by combining the average value of the DC output power and the rectification efficiency of the central rectenna sub-array.

[0068] Step S1 of the present invention includes:

[0069] S11. Build a ground suspension experimental platform for the rectenna array, which includes a ground microwave emission system and a receiving antenna system.

[0070] The ground microwave emission system includes a microwave emitter, a water cooling device, a control host computer, and a reflector antenna. The microwave emitter is respectively connected to the reflector antenna, the water cooling device, and the control host computer. Specifically, first connect the reflector antenna to the microwave emitter, then connect the water cooling device to the microwave emitter, and finally use the host computer to remotely control the microwave emitter. In an embodiment of the present invention, the experimental platform is built directly below the receiving antenna unit, and the power supply of the microwave emitter and the water cooling device are placed on both sides of the reflector antenna. Adjust the position of the horn antenna of the reflector antenna so that its phase center is located at the focus. Use an infrared rangefinder to adjust the distance between the microwave emitter and the receiving antenna unit to achieve alignment.

[0071] The receiving antenna system includes a receiving antenna unit and a power probe. An SMA interface is provided on the receiving antenna unit. Connect the SMA interface to the power probe, and transmit the received power data to the control host computer through the LAN port on the power probe. The receiving antenna unit and the power meter probe need to be installed on a rigid frame and suspended to the target height by three poles with ropes. The target height in this embodiment is 10 - 15m. To keep the rectenna array horizontal in the air, a level is installed on the frame. During the hoisting process, attention should be paid to the level to determine whether the receiving antenna unit is horizontally suspended in the air.

[0072] The microwave source of the present invention uses a 1.5kW microwave source. When the 1.5kW microwave source is in use, it will generate a large amount of heat and needs to be cooled by air cooling, and a water cooling device is configured for cooling. The cooling water must be pure water, and the water flow rate is required to be not less than 2.5L / min, and the inlet water temperature needs to be controlled at 0 - 30°C.

[0073] Connect the high-frequency microwave power supply, the 1.5kW microwave head and the water cooling device. It should be noted that the output frequency of the microwave source fluctuates within a range of ±15MHz. From the simulation results of the rectenna unit, it can be seen that the frequency fluctuation of ±15MHz has little impact on the performance of the rectenna unit, and the rectenna unit can still be used. In addition, the maximum output power of the microwave source can reach 1.5kW, and a waveguide-to-waveguide connection form needs to be used to dock with the feed of the reflector antenna.

[0074] S12. Test the power transceiver path of the rectenna array to ensure that no instruments are damaged during the experiment and all equipment is operating normally. Calculate the irradiation power density at different height positions through the received power of the receiving antenna unit, and calibrate the irradiation power density.

[0075] Assume the input power of the reflector antenna is P t , and the gain is G t , the maximum radiation direction points to the receiving antenna unit at a distance of r. The irradiation power density ρ at the receiving antenna unit is expressed as:

[0076]

[0077] Assume the gain of the receiving antenna unit is G r , the wavelength at the operating frequency point is λ, and the maximum radiation direction also points to the reflector antenna. The maximum received power of the receiving antenna unit is expressed as:

[0078]

[0079] In formulas (1) and (2), P t is the input power of the reflector antenna, G tis the gain of the reflector antenna, G r is the gain of the receiving antenna element, λ is the wavelength at the operating frequency point, ρ is the irradiation power density at the receiving antenna element, P r is the maximum received power of the receiving antenna element.

[0080] Calculate the irradiation power density at different height positions through the received power of the receiving antenna element.

[0081] Formulas (1) and (2) are the Friis transmission formulas. Using the receiving antenna element and the rectenna subarray, the irradiation power density of the space where the rectenna is located is calibrated at different energy transfer distances with low power. Before the high-power experiment, it is necessary to use low power for testing. Any power can be used to calibrate the power density. Using low power ensures the safety of equipment and personnel.

[0082] In one embodiment of the present invention, a collection module is connected to the output end of the rectenna, and a long wire is used to connect to a high-power resistor box on the ground. Record the voltage on the resistor box. After measuring a set of data, change the resistance value of the resistor box and test again to observe the optimal load and its corresponding power value.

[0083] Use a microwave source to emit a power of 5 dBm, and the gain of the receiving antenna element is 5.5 dBi. Measure the received power of the receiving antenna element at different height positions in the receiving area, and calculate the irradiation power density at this height position through the received power of the receiving antenna element, as shown in Table 1.

[0084] Table 1

[0085]

[0086] As can be seen from Table 1, in the actual energy transfer experiment, as the energy transfer distance increases, the microwave power that the antenna can receive also decreases slightly. When the energy transfer distance increases to 15 m, the received microwave power decreases by 34 dB compared to the transmitted power. At this point, the power density in the central area within the range of 10 - 15 m of the energy transfer distance can be calibrated.

[0087] Step S2 of the present invention includes:

[0088] Based on the experimental platform built in step S1, replace the receiving antenna element with a rectenna array and test the DC output power of the rectenna array under static conditions. The test method is: use a wire to connect to a high-power resistor box on the ground at the output end of the rectenna array, record the voltage on the resistor box. After measuring a set of data, change the resistance value of the resistor box and test again to obtain the voltage and current conditions of the rectenna array at different load resistance values, and calculate the DC output power according to the voltage and current.

[0089] Calculate the DC output power density according to the area of the rectenna sub-array, and calculate the rectification efficiency of the rectenna sub-array at different input powers according to the DC output power density and the irradiation power density of the rectenna sub-array. The rectification efficiency of the rectenna sub-array at different input powers is expressed as:

[0090]

[0091] In formula (3), ρ is the DC output power density of the rectenna sub-array, and ρ 照射 is the calibrated irradiation power density.

[0092] In step S2, based on the experimental platform built in step S1, replace the test target from the receiving antenna unit with the rectenna array, and test the DC output power capability of the rectenna array at different heights. In order to keep the integrated rectenna array horizontal in the air, a spirit level is installed on the rectenna array. During the experiment, the rectenna array needs to be suspended to a certain height by three poles with ropes. During the hoisting process, observe the spirit level and adjust the attitude of the rectenna array. Since the integrated rectenna array has a large area and is prone to breakage, in order to hang it in the air intact, a support frame is required to place the rectenna array. Each sub-array of the rectenna array is fixed on the foam board of the composite skin with double-sided tape. A total of 114 rectenna sub-arrays are installed. The connection relationship between the sub-arrays is parallel, and they are isolated by nylon terminal caps and high-temperature resistant insulating tapes to prevent short circuits. Finally, connect the output wires of the rectenna array to the resistance box. Fix the foam board to the frame with nano glue, and tie 3 traction ropes to the frame. Hang the foam board in the air and adjust the foam board to the required attitude through the 3 traction ropes.

[0093] Suspend the rectenna array to the target test height (10 - 15 m), and use the maximum input power (1.5 kW) of the microwave transmission system to test the DC output power of the rectenna array.

[0094] In order to test the DC output power of the rectenna array, connect the rectenna array with all sub-arrays in parallel to a high-power adjustable resistance box. By changing the resistance value of the resistance box, measure the voltage and current of the rectenna array at different load resistances, and calculate the DC output power according to the voltage and current. Plot the data in a chart, and the specific situation is shown in Table 2 and the appendix Figure 2 as shown.

[0095] Table 2

[0096]

[0097]

[0098] From Table 2 and the appendixFigure 2 It can be seen that when the energy transmission distance is 10 m, the rectenna array can output a maximum DC output power of 74.52 W. As the energy transmission distance increases, the DC output power gradually decreases. When the energy transmission distance is 15 m, the maximum DC output power is 63.94 W. Combining Table 2 and the appendix Figure 2 Analysis shows that the optimal load of the rectenna array is around 40 Ω.

[0099] Then, take the rectenna sub-array at the center of the array as the object. When the energy transmission distance is 15 m, the DC output power density is measured according to the area of the rectenna sub-array. Combining the transmission power attenuation calibrated in Table 1, the irradiation power density under different microwave input powers is given, and the rectification efficiency of the rectenna sub-array under different microwave input powers is calculated based on the irradiation power density and the DC output power density. The specific situation is shown in Table 3.

[0100] Table 3

[0101]

[0102] As can be seen from Table 3, when the input power of the microwave transmission system reaches 1.5 kW and the energy transmission distance is 15 m, the rectenna sub-array can obtain a DC output power of 3.75 W. At this time, the output DC power density is 371.46 W / m2, and the irradiation power density is 654.32 W / m2. The rectification efficiency of the rectenna sub-array can be obtained as 56.77%.

[0103] Step S3 of the present invention includes:

[0104] S31. Build an energy transmission flight experiment platform.

[0105] Install the ground microwave transmission system on the vehicle platform to enable the UAV to continuously receive microwave energy during following flight with the vehicle. Since the vehicle is relatively bumpy during driving, a turntable is needed to fix and finely adjust the reflector antenna. An air shock absorber device is arranged at the turntable base to reduce the bumps caused by the vehicle during driving to the transmission system and the damage to in-vehicle equipment, and ensure the normal operation of in-vehicle equipment. Install a camera on the reflector antenna to observe whether the UAV is aligned with the reflector antenna. A servo device is installed on the turntable to finely adjust the reflector antenna to align with the scaled verification aircraft in flight. Install a GPS on the vehicle body to obtain the real-time position information of the vehicle, and use a radio to send the position information to the UAV flight control end in real time to adjust the UAV flight information.

[0106] Attach the rectenna array to the web of the drone. To better fit the belly of the drone, cut the rectenna array according to the size of the reserved space. It consists of 98 rectenna sub-arrays in total. Two rectenna arrays are made, one of which is the test object in step S3: the DC output power test of the rectenna array, and the other is the test object in step S4: the DC output power density test of the central rectenna sub-array. For the rectenna array used in the DC output power density test of the central rectenna sub-array, the center is a single rectenna sub-array, and the remaining 97 rectenna sub-arrays are grouped in a fully parallel manner.

[0107] Connect the output end of the rectenna array to the load on the drone. The voltage and current on the load can be measured by using the analog input module and transmitted to the ground station control host computer through the telemetry antenna. And a data acquisition module is installed at the output end of the rectenna array, which is used to transmit the energy data received by the drone back to the control host computer.

[0108] S32. During the continuous flight of the drone, test the DC output power of the rectenna array to obtain the average value of the DC output power of continuous energy transmission. The DC output power of the rectenna array intuitively represents the magnitude of the output energy transferred from microwave wireless energy transmission to the load.

[0109] On the basis of building the energy transmission flight experiment platform in step S31, the vehicle platform travels at a constant speed, and the drone follows the vehicle at a certain height above the vehicle. The real-time position information is transmitted to the ground microwave transmission system through the guiding device, and the beam control system adjusts the transmission direction according to the real-time position to ensure that the main beam always points, so that the drone continuously receives microwave energy.

[0110] Measure the voltage and current at the power input end of the ground microwave transmission system with a multimeter to obtain the input power of the ground microwave transmission system, and combine the microwave conversion efficiency to obtain the power value of the microwave transmitter. Examine the time history data of the output current of the reflector antenna recorded by the on-board recorder. According to the output data of the on-board recorder, calculate the DC output power of the rectenna array to obtain the graph of the DC output power of the rectenna array changing with time, and perform calculation and processing on the data in the graph to obtain the average value of the DC output power of the rectenna array.

[0111] Specifically, it is implemented according to the following steps:

[0112] S321. Turn on the ground microwave transmission system, set the power to the maximum value, and perform path debugging on the transmission link to ensure stable transmission power;

[0113] S322. The vehicle platform travels along the fixed route of the test site at a speed not less than 70 km / h to match the flight speed of the drone, as shown in the appendix Figure 3 as shown.

[0114] S323. Obtain flight altitude data by examining the GPS altitude information data during the pre-takeoff and the flight of the scaled aircraft. After takeoff, the flight platform carrying the rectifying antenna array (scaled aircraft composite rectifying antenna array) flies at a height of 15 m (planned flight path) along the test site.

[0115] S324. Activate the function of the drone tracking vehicle at the flight end, and the drone follows the vehicle in flight.

[0116] S325. During the flight energy transfer process, transmit the real-time position information to the ground microwave transmission system through the guiding device, and the reflector antenna servo device fine-tunes the reflector antenna to align with the flying scaled verification aircraft according to the real-time position information; measure the power input of the microwave transmission source power supply with a multimeter and a clamp meter, and obtain the microwave transmission source power value in combination with the microwave conversion efficiency.

[0117] S326. The ground station control host monitors the DC power output by the array. The DC output power of the rectifying antenna array can be calculated by examining the DC current and voltage output by the telemetered antenna. Due to the influence of the positioning accuracy and wind disturbance during the flight of the drone, the rectifying antenna array at the receiving end may deviate from the high-power microwave coverage area, resulting in fluctuations in the received power. Therefore, in this embodiment, the average value of the DC output power during 3.1 h of continuous energy transfer is used as the test result.

[0118] S327. The drone flies continuously for 3.1 h. Examine the data of the time history of the output current of the airborne antenna recorded by the airborne recorder, and the energy supply time of the microwave transmission system to the rectifying antenna array during the flight process can be known.

[0119] Test results: Measure the voltage and current at the power input end of the microwave energy emission device with a multimeter to obtain the input power of the microwave energy emission device, and obtain the emission end power value of 1.5 kW in combination with the microwave conversion efficiency. Examine the data of the time history of the output current of the airborne antenna recorded by the airborne recorder. It can be known that the energy supply time of this flight experiment reaches 3.1 h. Examine the output data of the airborne recorder, calculate the DC output power of the rectifying antenna array, and finally draw a graph of the DC output power of the rectifying antenna array changing with time, as shown in the appendix Figure 4 as shown.

[0120] From the appendix Figure 4It can be seen that the maximum DC output power of the rectenna array is around 61.5W, the minimum is around 43W, and there is a fluctuation of 18.5W within 3.1h. The DC output power decreases in a short period of time. At this time, the effect of the drone following the vehicle-mounted microwave transmission system is poor. The reason is that the rectenna array at the receiving end is offset from the high-power microwave coverage area due to the influence of positioning accuracy, wind disturbance, etc. during the flight of the drone. When the drone follows the vehicle-mounted microwave transmission system well, the DC output power of the rectenna array is maintained above 50W. Figure 4 By calculating and processing the data, it can be obtained that the average DC output power of the rectenna array within 3.1 hours is 52.7W.

[0121] Step S4 of the present invention comprises:

[0122] Replace another drone and rectenna array, replace the detection target with the central rectenna subarray, and test the DC output power of the central rectenna subarray during flight. The central rectenna subarray is located at the center of the array. The DC output power density of the central rectenna subarray represents the point with the highest energy density in the array, and is the point with the best theoretical performance in the array. Similarly, the rectification efficiency of the central rectenna subarray represents the point with the best energy conversion efficiency in the array, and represents the best performance at the unit level in the microwave wireless energy transmission test. If the rectenna array carried by the drone is not aligned with the vehicle-mounted microwave transmission system (that is, the central subarray is not located at the irradiation center of the transmission system), the performance of the central rectenna subarray will be compromised. In the case of alignment, the rectenna array including the central rectenna subarray can achieve the best performance.

[0123] The present invention collects the DC output current of the central rectenna subarray and the connected load resistance value, and calculates the DC output power of the central rectenna subarray. A section of data of the central rectenna subarray is intercepted, processed and plotted, and a graph of the DC output power of the central rectenna subarray over time is obtained, and the average DC output power of the central rectenna subarray is calculated. The DC output power density of the central rectenna subarray is calculated based on the average DC output power of the central rectenna subarray and the area of the central rectenna subarray, and the DC output power density of the central rectenna subarray is obtained. The DC output power density of the central rectenna subarray is compared with the irradiation power density calibration value to calculate the rectification efficiency of the central rectenna subarray.

[0124] Follow the steps below to implement it:

[0125] S41. Turn on the ground microwave transmission system, set the power to the maximum value, and perform path debugging on the transmission link to ensure that the transmission power is stable;

[0126] S42. The vehicle platform travels along a fixed route in the test site at a speed of no less than 70 km / h to match the flight speed of the drone. Figure 3 As shown;

[0127] S43. Obtain flight altitude data by reviewing GPS altitude information data before takeoff and during the flight of the UAV. The flight platform carrying the rectenna array (composite rectenna array of UAV) flies along the test site at an altitude of 15m (planned route) after takeoff;

[0128] S44, turn on the vehicle tracking function on the flight terminal, and the aircraft will fly along with the vehicle;

[0129] S45. During the flight energy transmission process, the real-time position information is transmitted to the ground microwave transmission system through the guidance device, and the reflector antenna servo device fine-tunes the reflector antenna to align with the flying scaled verification aircraft according to the real-time position information; the input power of the microwave transmission source power supply is measured by a multimeter and a clamp meter, and the microwave transmission source power value is obtained in combination with the microwave conversion efficiency;

[0130] S46, the ground station controls the host computer to monitor the DC power output by the central rectifier antenna subarray, and the DC output power of the central rectifier antenna subarray can be calculated by examining the DC current and voltage data output by the telemetry antenna;

[0131] S47. After achieving a continuous stable test of not less than 10 seconds, the ground microwave transmission system is shut down, the UAV lands, and the test ends. The DC output power of the central single-block rectenna subarray is calculated by collecting the DC output current of the central single-block rectenna subarray and the connected load resistance.

[0132] Test results: The telemetry data of the central rectenna subarray for 10 seconds was intercepted and processed and plotted to obtain the central rectenna subarray DC output power variation with time graph, as shown in the attached figure. Figure 5 shown.

[0133] The DC output power density of the central rectenna subarray within 10 seconds can be calculated from the DC output power and area of the central rectenna subarray. The average value is 361.5 W / m2.

[0134] Through the ground suspension experiment of the rectenna array, it is known that when the energy transmission distance is 15m and the microwave source input power is 1.5kW, the rectenna array irradiation power density calibration value ρ 照射 It is 654.32W / m2, and during the second flight test, the UAV followed the vehicle-mounted microwave transmission system well, so it can be considered that the irradiation power density calibration value remains unchanged. By comparing the DC output power density of the central rectifier antenna subarray with the irradiation power density calibration value, the rectification efficiency can be calculated, and the formula is expressed as:

[0135]

[0136] In formula (4), ρ 中心 is the DC output power density of the central rectenna sub-array, and ρ 照射 is the calibrated value of the irradiation power density.

[0137] Processing the data yields a graph showing the variation of the DC output power density and rectification efficiency of the central rectenna sub-array over time, as shown in the appendix Figure 6 as follows.

[0138] As can be seen from the appendix Figure 6 the variation of the DC output power density of the central rectenna sub-array is relatively stable, indicating that during the flight energy transfer experiment, the drone and the vehicle-mounted microwave transmission system follow well. During the intercepted 10 s, the average rectification efficiency is 56%.

[0139] The present invention also provides a microwave wireless energy transfer system for wireless power supply to drones, which is used to implement the microwave wireless energy transfer test method for wireless power supply to drones according to the present invention. The microwave wireless energy transfer system includes: a ground suspension experimental platform and an energy transfer flight experimental platform.

[0140] The ground suspension experimental platform is mainly used to calibrate the irradiation power density in the space where the rectenna array is located and to test the DC output power of the rectenna array under static conditions; the energy transfer flight experimental platform is mainly used to test the DC output power of the rectenna array and the DC output power of the central rectenna sub-array during the continuous flight of the drone.

[0141] The ground suspension experimental platform of the present invention includes a ground microwave transmission system and a receiving antenna system. The ground microwave transmission system includes a microwave transmission source, a water cooling device, a control host computer, and a reflector antenna. The microwave transmission source is respectively connected to the reflector antenna, the water cooling device, and the control host computer. The receiving antenna system includes a receiving antenna unit, a rectenna array, and a power probe. SMA interfaces are provided on the receiving antenna unit and the rectenna array, and the SMA interfaces are connected to the power probe. The received power data of the receiving antenna unit and the rectenna array are transmitted to the control host computer through the LAN port on the power probe. On the basis of ensuring safe operation, the ground microwave transmission system can achieve long-term high-power microwave output, can perform long-term microwave energy irradiation on the rectenna array, and provides practical guidance for the high-power microwave wireless energy transfer experimental platform.

[0142] In one embodiment of the present invention, the experimental platform is built directly below the receiving antenna unit and the rectenna array, and the power supply and water cooling device of the microwave transmitter are placed on both sides of the reflector antenna. Adjust the position of the horn antenna of the reflector antenna so that its phase center is located at the focal point. Use an infrared rangefinder to adjust the distance between the microwave transmitter and the receiving antenna unit and the rectenna array to achieve alignment.

[0143] During the experiment, the receiving antenna unit and the power meter probe need to be installed on a rigid frame and suspended to the target height by three poles with ropes. To keep the rectenna array horizontal in the air, a level is installed on the frame. During the lifting process, attention should be paid to the level to determine whether the receiving antenna unit is horizontally suspended in the air. The rectenna array needs to be suspended to a certain height by three poles with ropes. During the lifting process, observe the level to adjust the attitude of the rectenna array.

[0144] The energy transmission flight experimental platform of the present invention further includes a vehicle platform, a drone, and a data acquisition module on the basis of the ground-suspended experimental platform. The microwave transmitter is installed on the vehicle platform. The rectenna array is attached to the web of the drone. The output end of the rectenna array is connected to the load of the drone, and a data acquisition module is installed at the output end of the rectenna array. The data acquisition module is used to transmit the energy data received by the drone back to the control host computer.

[0145] Since the vehicle is bumpy during driving, a turntable is needed to fix and finely adjust the reflector antenna. An air-filled shock absorber is arranged at the turntable base to reduce the bumps caused by the vehicle during driving to the transmitting system and damage to in-vehicle equipment, and ensure the normal operation of in-vehicle equipment. Install a GPS on the vehicle body to obtain the real-time position information of the vehicle, and use a radio station to send the position information to the drone flight control end in real time to adjust the drone flight information in real time.

[0146] On the basis of the ground-suspended experiment of the present invention, an energy transmission flight experimental platform is built. The ground microwave transmission system is mounted on the vehicle platform, and the rectenna array is attached to the web of the drone. When the vehicle is driving on the runway, the drone follows and flies at a certain height above it and continuously receives microwave energy. This energy transmission flight experimental platform can transmit energy to moving targets, such as drones and other devices.

[0147] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A microwave wireless power transmission test method for wireless power supply of unmanned aerial vehicles, characterized in that, Including the steps: S1. Calibrate the irradiation power density in the space where the rectenna array is located; S2. Test the DC output power of the rectenna array under static conditions, calculate the DC output power density of the rectenna sub-array, and calculate the rectification efficiency of the rectenna sub-array according to the DC output power density of the rectenna sub-array and the irradiation power density; S3. Based on the rectification efficiency of the rectenna sub-array, test the DC output power of the rectenna array during the continuous flight of the UAV, and calculate the average value of the DC output power of the rectenna array; S4. Test the DC output power of the central rectenna sub-array during the continuous flight of the UAV, calculate the average value of the DC output power of the central rectenna sub-array and the DC output power density of the central rectenna sub-array, calculate the rectification efficiency of the central rectenna sub-array according to the DC output power density of the central rectenna sub-array and the irradiation power density, and evaluate the effect of microwave wireless power transfer by combining the average value of the DC output power and the rectification efficiency of the central rectenna sub-array.

2. The microwave wireless power transfer test method for wireless power supply to unmanned aerial vehicles according to claim 1, wherein The step S1 includes: S11. Build a ground suspension experimental platform for the rectenna array; The ground suspension experimental platform for the rectenna array includes a ground microwave transmission system and a receiving antenna system; The ground microwave transmission system includes a microwave transmitter, a water cooling device, a control host computer and a reflector antenna, and the microwave transmitter is respectively connected to the reflector antenna, the water cooling device and the control host computer; The receiving antenna system includes a receiving antenna unit and a power probe, an SMA interface is arranged on the receiving antenna unit, the SMA interface is connected to the power probe, and the received power data is transmitted to the control host computer through the LAN port on the power probe; S12. Calculate the irradiation power density at different height positions and calibrate the irradiation power density.

3. The microwave wireless power transmission test method for wireless power supply of drones according to claim 2, characterized in that The step S12 includes: Assume that the input power of the reflector antenna is P t , and the gain is G t . The maximum radiation direction points to the receiving antenna element at a distance of r. The illumination power density ρ at the receiving antenna element is expressed as: Assume that the gain of the receiving antenna unit is G r , the wavelength at the operating frequency point is λ, and the maximum radiation direction also points to the reflector antenna. The maximum received power of the receiving antenna unit is expressed as: In Formula (1) and Formula (2), P t is the input power of the reflector antenna, G t is the gain of the reflector antenna, G r is the gain of the receiving antenna element, λ is the wavelength at the operating frequency point, ρ is the illumination power density at the receiving antenna element, P r is the maximum received power of the receiving antenna element; Calculate the irradiation power density at different height positions through the received power of the receiving antenna unit.

4. The microwave wireless power transfer test method for wireless power supply to drones according to claim 2, characterized in that The step S2 includes: Replace the receiving antenna unit with the rectenna array, test the DC output power of the rectenna array under static conditions, calculate the DC output power density according to the area of the rectenna sub-array, and calculate the rectification efficiency of the rectenna sub-array at different input powers according to the DC output power density of the rectenna sub-array and the irradiation power density. The rectification efficiency of the rectenna sub-array at different input powers is expressed as: In Equation (3), ρ is the DC output power density of the rectenna subarray, and ρ 照射 is the calibrated irradiation power density.

5. The microwave wireless power transmission test method for wireless power supply to drones according to claim 4, characterized in that The method for testing the DC output power of the rectenna array in the step S2 includes: Connect a ground high-power resistor box to the output end of the rectenna array with a wire, record the voltage on the resistor box, after measuring a set of data, change the resistance value of the resistor box, and test again to obtain the voltage and current conditions of the rectenna array at different load resistance values, and calculate the DC output power according to the voltage and the current.

6. The microwave wireless power transmission test method for wireless power supply to drones according to claim 2, characterized in that The step S3 includes: S31. Build an energy transfer flight experimental platform; The described ground microwave transmission system is installed on a vehicle platform. The rectifying antenna array is attached to the drone web. The output end of the rectifying antenna array is connected to the load on the drone, and a data acquisition module is installed at the output end of the rectifying antenna array. The data acquisition module is used to transmit the energy data received by the drone back to the control host computer; S32. During the continuous flight of the drone, test the DC output power of the rectifying antenna array to obtain the average value of the DC output power for continuous energy transmission.

7. The microwave wireless power transmission test method for wireless power supply to drones according to claim 6, wherein, The step S32 includes: Measure the voltage and current at the power input end of the ground microwave transmission system with a multimeter to obtain the input power of the ground microwave transmission system, and combine the microwave conversion efficiency to obtain the power value of the microwave emission source; Examine the time history data of the output current of the reflector antenna recorded by the on-board recorder. According to the output data of the on-board recorder examination, calculate the DC output power of the rectifying antenna array to obtain a graph of the DC output power of the rectifying antenna array varying with time. Process the data in the graph to obtain the average value of the DC output power of the rectifying antenna array.

8. The microwave wireless power transfer test method for wireless power supply to drones according to claim 2, wherein The step S4 includes: Collect the DC output current of the central rectifying antenna sub-array and the connected load resistance value, and calculate the DC output power of the central rectifying antenna sub-array; Intercept a section of data of the central rectifying antenna sub-array for processing and drawing to obtain a graph of the DC output power of the central rectifying antenna sub-array varying with time, and calculate the average value of the DC output power of the central rectifying antenna sub-array; Calculate the DC output power density of the central rectifying antenna sub-array from the average value of the DC output power of the central rectifying antenna sub-array and the area of the central rectifying antenna sub-array to obtain the DC output power density of the central rectifying antenna sub-array; Compare the DC output power density of the central rectifying antenna sub-array with the calibration value of the irradiation power density, and calculate the rectification efficiency of the central rectifying antenna sub-array. The formula is expressed as: In formula (4), ρ 中心 is the DC output power density of the central rectenna subarray, and ρ 照射 is the calibrated value of the irradiation power density; Process the data to obtain graphs of the DC output power density and rectification efficiency of the central rectifying antenna sub-array varying with time.

9. A microwave wireless power transmission system for wireless power supply of unmanned aerial vehicles, characterized in that, For implementing the microwave wireless power transfer test method for wireless power supply to drones described in any one of claims 1 to 8, it includes: A ground suspension experimental platform for calibrating the irradiation power density in the space where the rectifying antenna array is located and testing the DC output power of the rectifying antenna array in a stationary state; A power transfer flight experimental platform for testing the DC output power of the rectifying antenna array and the DC output power of the central rectifying antenna sub-array during the continuous flight of the drone.

10. The microwave wireless power transmission system for wireless power supply to an unmanned aerial vehicle according to claim 9, wherein, The ground suspension experimental platform includes a ground microwave transmission system and a receiving antenna system; The ground microwave transmission system includes a microwave emission source, a water cooling device, a control host computer, and a reflector antenna. The microwave emission source is respectively connected to the reflector antenna, the water cooling device, and the control host computer; The receiving antenna system includes a receiving antenna unit, a rectenna array, and a power probe. SMA interfaces are provided on the receiving antenna unit and the rectenna array, and the SMA interfaces are connected to the power probe. The received power data of the receiving antenna unit and the rectenna array are transmitted to the control host computer through the LAN port on the power probe. On the basis of the ground suspension experiment platform, the energy transmission flight experiment platform further includes a vehicle platform, a drone, and a data acquisition module. The microwave transmitter is installed on the vehicle platform. The rectenna array is attached to the web of the drone. The output end of the rectenna array is connected to the load of the drone, and a data acquisition module is installed at the output end of the rectenna array. The data acquisition module is used to transmit the energy data received by the drone back to the control host computer.

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