CN113777620B

CN113777620B - High-precision passive positioning and energy transmission system based on resonance light beams

Info

Publication number: CN113777620B
Application number: CN202111114914.7A
Authority: CN
Inventors: 刘庆文; 刘明清; 徐梦圆; 姜清伟; 熊明亮; 方稳
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2023-08-29
Anticipated expiration: 2041-09-23
Also published as: CN113777620A

Abstract

The invention relates to a high-precision passive positioning and energy-transferring system based on resonance light beams, which comprises: positioning a base station: the system comprises a pumping source, a laser ToF module for ranging, a first micro-processing unit, a demodulator, a gain medium, a first retro-reflector and a CMOS image sensor, wherein the gain medium, the first retro-reflector and the CMOS image sensor are sequentially arranged along an optical path; positioning a target: comprises a second retro-reflector as a retro-reflector, a photovoltaic cell PV for realizing photovoltaic power generation, a battery, a second micro-processing unit, a liquid crystal switch and an LCD driving source. Compared with the prior art, the invention has the advantages of passive target positioning, communication, high-precision passive positioning and the like.

Description

High-precision passive positioning and energy transmission system based on resonance light beams

Technical Field

The invention relates to the technical field of resonant light positioning, in particular to a high-precision passive positioning and energy transmission system based on a resonant light beam.

Background

Complete positioning systems based on LED systems are currently emerging in the field of resonant light positioning. An LED-based positioning system with the ability to identify a target, which transmits positioning accuracy of 2cm, requires an external power source of several tens of μw for transmitting ID data. Whereas passive LED-based positioning systems eliminate the need for any electronic components in the target entirely and with accuracy in the order of centimeters. However, the above solution cannot provide enough power for the target to overcome the cruising bottleneck of the internet of things device, and in addition, the above system faces the challenge of improving the positioning accuracy to the millimeter level.

Chinese patent 201910294606.3 discloses a tracking positioning system based on separation chamber, it carries out angle measurement and distance measurement through intracavity laser, and a part intracavity laser passes through the optical sensing element and surveys the angle, and a part intracavity laser is through utilizing the interference ranging principle to carry out range finding, but this system transmitting end needs rotation motor and the communication module of transmitter, receiver department to realize the location.

Chinese patent 202110825793.0 discloses a high-precision passive positioning system based on resonant beams, which uses resonant beams to perform AOA estimation and uses a ToF module to perform distance measurement, so that three-dimensional space positioning with millimeter-level precision can be realized, but the system disclosed by the invention does not have the capability of simultaneously supplying power to a positioning target and cannot acquire ID information of the positioning target.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a high-precision passive positioning and energy transmission system based on a resonant beam.

The aim of the invention can be achieved by the following technical scheme:

a simultaneous high-precision passive positioning and energy-transfer system based on a resonant beam, the system comprising:

positioning a base station: the device comprises a pumping source, a laser ToF module for ranging, a first micro-processing unit, a demodulator, a gain medium, a first retro-reflector and a CMOS image sensor, wherein the gain medium, the first retro-reflector and the CMOS image sensor are sequentially arranged along an optical path, the CMOS image sensor is arranged at the rear part of the first retro-reflector and used for carrying out AoA estimation, and the first micro-processing unit is respectively connected with the demodulator and the CMOS image sensor;

at least one positioning target: the dual-reflector resonant cavity comprises a second retro-reflector serving as a retro-reflector, a photovoltaic cell PV, a battery, a second micro-processing unit, a liquid crystal switch and an LCD driving source, wherein the photovoltaic cell PV is used for realizing photovoltaic power generation, the photovoltaic cell PV is arranged behind the second retro-reflector and is connected with the battery, the battery supplies power for the second micro-processing unit and the LCD driving source respectively, the liquid crystal switch is arranged in front of the second retro-reflector and controls the LCD driving source to realize linear modulation of a resonant beam through the micro-processing unit, and the first retro-reflector and the second retro-reflector which are separated in space form the dual-retro-reflector resonant cavity.

The first and second retro-reflectors respectively adopt cat eye type retro-reflectors, pyramid prism retro-reflectors or array structures composed of the retro-reflectors, when the first and second retro-reflectors adopt cat eye type retro-reflectors, the cat eye type retro-reflectors are composed of reflectors and thin lenses, and the reflectors all adopt reflectors with partial reflectivity.

Based on the system, the stable resonance, power output, toF ranging, angle measurement, photoelectric conversion and ID information acquisition functions of the resonance light system can be respectively realized.

For stable resonance, the first retro-reflector of the positioning base station, the gain medium and the second retro-reflector at the positioning target together form a resonant optical system, the gain medium omnidirectionally transmits photons given the pumping power of the pumping source, and the dual-retro-reflector resonant cavity enables the photons to be reflected back and forth in the cavity, so that the photons are amplified through the gain medium for multiple times, and stable resonance can be established when the gain in the cavity is enough to compensate the transmission loss and the output coupling loss in the cavity.

For power output, a part of resonance beams are output at the positioning base station for positioning, a part of resonance beams are output at the positioning target, and energy of the resonance beams is converted into electric power, and then laser output powers at the positioning base station and the positioning target are calculated as follows:

I _base ＝(1-R ₁ )I _circ

I _targt ＝(1-R ₂ )f _circ

I _- (z)≈I ₊ (z)≈I _circ

wherein R is ₁ 、R ₂ Reflectivity of the reflector in the first and second retro-reflectors, respectively, I _base To locate the laser output power at the base station, I _target To locate the laser output power at the target, I _circ For unidirectional intensity of circulating light beam in resonant cavity, I _- (z) and I ₊ (z)The intensity of the left traveling wave and the right traveling wave.

For ToF ranging, using a self-triggering pulsed laser ToF sensor ranging by measuring the time of flight of a laser pulse from the emitter to the target and back to an avalanche photodiode at the emitter, then there are:

τ＝t ₂ +t ₃ +t ₄

wherein τ is the total delay time, t ₂ Circuit delay time, t, for the return laser pulse to be received by the avalanche photodiode and converted into an electrical signal ₃ The number of laser pulses emitted by the counting unit is smaller than N _p On the premise of outputting a trigger signal to the delay time of the transmitting unit, t ₄ For the response time consumed by the semiconductor laser diode, c is the speed of light,for the distance of the target relative to the base station, T _N To measure the time interval, N _p Is the number of continuous laser pulses.

For angle measurement, after one space transmission, the light beam transmitted from the first reflector M1 of the first retro-reflector is transmitted to the CMOS image sensor, light field distribution on the CMOS image sensor is obtained, the centroid position of a light spot on the CMOS image sensor is obtained according to a centroid algorithm, the position of a positioning target is determined according to the position of the light spot on the CMOS image sensor, and then the angle between the base station and the target is obtained.

For photoelectric conversion, the system converts the power of the light beam passing through the second reflector in the second retro-reflector into electric energy through the photovoltaic cell PV, and obtains the nonlinear relation between the output current and the voltage of the photovoltaic cell PV through a PV equivalent circuit model, so as to calculate the output power of the photovoltaic cell PV, and then the system comprises the following steps:

wherein I is _o And V _o For output current and voltage at photovoltaic cell PV, R _sh R is the resistance of the shunt resistor _s Is the resistance of the series resistor, I _d Is the forward current of the diode, I _ph Is a parameter related to the intensity of light incident on the PV.

The system modulates a resonant beam based on linear modulation by an LCD shutter comprising two linear polarizers to selectively block the beam incident thereon and a liquid crystal as a modulator, the first linear polarizer converting the resonant beam into a linearly polarized beam, the liquid crystal determining a polarization angle between the beam and the second linear polarizer, and the second linear polarizer blocking or unblocking the resonant beam according to the polarization angle.

For ID information acquisition, an OOK modulation scheme is adopted for modulation, specifically:

if the CMOS image sensor detects the intensity of the light beam, the modulation symbol is set to be 1, if the CMOS image sensor does not detect the intensity of the light beam, the modulation symbol is set to be 0, the state of the liquid crystal shutter is controlled by changing the voltage applied to the liquid crystal shutter through the coding logic, whether the CMOS image sensor detects light spots exist or not is realized, a signal is sent to a decoding module, and further ID information of a positioning target is sent to a base station from the target.

Compared with the prior art, the invention has the following advantages:

1. the invention provides a complete positioning scheme, through which the position and ID information of the target can be obtained under the condition of no external power supply, and enough energy is provided for the target, meanwhile, the two main bottlenecks of 'target positioning' and 'terminal cruising' in the world are solved, and through system simulation, the system can realize millimeter-level positioning precision and watt-level wireless energy transmission power in the range of a meter-level transmission distance and a field angle of tens of degrees.

2. The invention provides a SLAPT system which can realize high-precision passive positioning, and has the advantages of high-precision passive positioning, which is realized by utilizing a resonance beam to realize high-precision passive positioning, and has the characteristics of narrow beam transmission, high signal-to-noise ratio (SNR) and self-alignment based on a resonance optical system (RBS), wherein active signal emission (for example, wiFi/Bluetooth positioning) from a target is not needed, and a positioning base station is not needed to carry out beam control (for example, radar/laser radar).

3. The resonant beam is essentially intracavity laser, has the characteristics of collimation, narrow beam transmission and high transmission efficiency, provides a foundation for realizing millimeter-level positioning and watt-level wireless energy transmission power, and can realize high-efficiency conversion from optical power to electric power by adopting a laser photovoltaic cell (PV) with high conversion efficiency.

4. The LCD switch is adopted, the polarization characteristic of the light beam is utilized to realize the ID information transfer from the positioning target to the positioning base station, the energy provided by the wireless energy transmission of the system itself obtains the position and ID of the target under the condition of no external power supply, and the complete passive positioning is realized.

Drawings

Fig. 1 is a SLAPT application scenario and basic principle.

FIG. 2 is a schematic diagram of a high-precision passive positioning system based on resonant light.

Fig. 3 shows the output laser power model, where (a) is the circulating power model in the resonant cavity and (b) is the output intensity on both sides of the resonant cavity.

Fig. 4 is a schematic diagram of a ToF module ranging structure and principle.

Fig. 5 is an angle measurement principle.

Fig. 6 is a PV equivalent circuit model for energy harvesting.

Fig. 7 is an ID recognition model.

Fig. 8 shows the relationship between the angle measurement error and the charging power and the angle between the positioning target and the positioning base station, respectively, at different system pump powers when the positioning target is 1m away from the positioning base station.

Fig. 9 shows the relationship between the angle measurement error and the charging power and the angle between the positioning target and the positioning base station, respectively, at different system pump powers when the positioning target is 2m away from the positioning base station.

Detailed Description

The invention will now be described in detail with reference to the drawings and specific examples.

High precision positioning and providing wireless power to small objects are two key requirements in the internet of everything (IoE) era. Existing positioning systems can be divided into the following categories:

i) Active positioning schemes, such as Wi-Fi, bluetooth, zigbee, etc., require an external power source to enable the target to send signals to the base station;

ii) passive positioning schemes, such as lidar or LED-based schemes, typically require beam steering at the base station.

However, none of the above solutions provides both high precision positioning and sufficient power supply for the target. Furthermore, for complete target positioning, i.e., obtaining accurate location and Identity (ID) information of the target, the passive scheme may require an external power source to send the ID data.

The present invention thus proposes a simultaneous localization and power transfer (SLAPT) system by means of a resonant beam, obtaining the position and ID of the target with millimeter-level accuracy, without the need for an external power source, while providing the target with watt-level power.

As shown in fig. 1, the invention adopts a cat eye as a target in a retro-reflector (other optional structures can be pyramid prisms) embedded in a base station and a SLAPT system, the base station can perform self-alignment with a target in a system field of view (FoV) through a resonance beam carrying power and data, the resonance beam is output at the base station and used for acquiring a position and an ID, the output beam is output at the target and used for supplying power, the output beam irradiates on a Complementary Metal Oxide Semiconductor (CMOS), the position of a beam spot on the CMOS correspondingly changes along with the change of the included angle between the base station and the target, so that the position of the target can be automatically obtained, the output beam irradiates on a Photovoltaic (PV) panel to be converted into electric energy, preparation is made for battery charging, wireless power supply is favorable for permanently continuous voyage of the target, in addition, the power supply can support the function of transmitting ID data from the target to the base station, in fig. 1, the target adopts a Liquid Crystal Display (LCD) shutter, and the on/off state of the LCD shutter is changed to transmit an ID code to the base station.

In a simultaneous high-precision passive positioning and energy-transferring system based on resonance light of the present invention, a positioning base station is composed of a gain medium, a cat eye with a first mirror M1 and a first thin lens L1, a beam power attenuator Att, a CMOS image sensor, a laser ToF module, a micro processing unit (MCU) and a demodulator, and a target is composed of a cat eye including a second mirror M2 and a second thin lens L2, a Liquid Crystal (LCD) switch, a photovoltaic cell (PV), a battery, an MCU and an LCD driving source. The retro-reflector can adopt an array structure formed by a cat eye type retro-reflector or a pyramid prism retro-reflector or the retro-reflector. The position of the resonant beam spot on the retro-reflector will also change when the target changes its angle relative to the base station. The invention can thus estimate the angle between the target and the locating base station by obtaining the position of the resonant beam spot on the retro-reflector. Complementary Metal Oxide Semiconductor (CMOS) image sensors are used in the base station to capture the corresponding spot locations and to estimate the angle using an angle of arrival (AoA) algorithm.

The resonant light based high precision passive positioning system also incorporates a laser time of flight (ToF) module to estimate the distance between the base station and the target. Thus, the three-dimensional position of the target can be acquired. In addition, the resonance light beam is essentially intracavity laser, has the characteristics of collimation, narrow beam transmission and high transmission efficiency, provides a foundation for realizing millimeter-level positioning and watt-level wireless energy transmission power, can realize the conversion from optical power to electric power by adopting a laser photovoltaic cell (PV) with high conversion efficiency, and realizes the ID information transmission from a positioning target to a positioning base station by adopting an LCD switch and utilizing the polarization characteristic of the light beam. The system can provide energy by wireless energy transmission, and the position and ID of the target can be obtained under the condition of no external power supply, so that complete passive positioning is realized.

Examples

A. SLAPT system structure and function principle

The SLAPT system adopts the laser ToF module to measure the distance, and utilizes the resonance light beam generated between the base station and the target to perform AoA estimation, thereby realizing the acquisition of the three-dimensional position information of the positioning target; in addition, by utilizing the characteristics of high transmission efficiency of the resonant light beam and the like, the photovoltaic cell (PV) is integrated at the positioning target to convert the output resonant light power into electric power; the power supply function is provided, and the positioning target can realize the functions of sending signals and the like under the condition of not integrating a large-capacity battery; for example, in the system, the energy is used for realizing that the positioning target transmits information to the positioning base station, so that the positioning base station is helped to determine the ID information of the target. The system can realize complete passive positioning (simultaneously acquire three-dimensional position information and ID information, and power supply outside the system is not required to be transposed to power supply for a positioning target), and in addition, the power supply for the positioning target can support the positioning target to realize other additional functions.

The structure of the SLAPT system is shown in fig. 2, and the base station of the SLAPT is composed of a gain medium, a cat eye with M1 and L1, a beam power attenuator Att, a CMOS image sensor, a laser ToF module, a micro processing unit (MCU), and a demodulator, and the target is composed of a cat eye containing M2 and L2, a Liquid Crystal (LCD) switch, a photovoltaic cell (PV), a battery, an MCU, and an LCD driving source.

In the SLAPT system, the retro-reflector of the positioning base station, the gain medium and the retro-reflector at the positioning target together form a resonant optical system (RBS), and the two spatially separated retro-reflectors form a dual-retro-reflector resonant cavity. Given the pump power of the pump source, the gain medium transmits photons omnidirectionally. Even if the two retroreflectors are not exactly aligned, the dual retroreflective cavities enable photons to be reflected back and forth within the cavities, thereby enabling photons to be amplified multiple times through the gain medium. If the mirror in the cavity is partially reflective, some of the photons will be coupled out of the cavity. Furthermore, due to the limited size of the cell, intra-cavity transmission loss will occur, however, once the intra-cavity gain can compensate for the intra-cavity transmission loss and the out-coupling loss, stable resonance can be established.

In SLAPT systems, the principle of generation of a resonant beam in the RBS brings the following three key advantages for SLAPT:

i) Intrinsic safety. Once foreign matters (i.e. human bodies) invade the cavity, the vibration condition of the RBS is destroyed, and the resonance light beam is immediately cut off, so that the human bodies are not damaged by high-power light beams, and the safety is ensured;

ii) self-alignment. Since both the base station and the target have retro-reflectors, the RBS allows the beam to retroreflect in the cavity, and the base station can self-locate the target within the system field of view (FoV) even if the two retroreflectors are not facing each other;

iii) The resonant beam is essentially an intracavity laser. Therefore, the resonance light beam inherits the narrow light beam transmission characteristic of the laser, so that the air transmission efficiency of the resonance light beam is high, and the resonance light beam is not as high as the radio frequency has huge loss in long-distance transmission.

Due to the architecture of the SLAPT system, the angle between the target and the base station can be reflected on the resonance beam spot position on the optical element, namely M1, part of resonance beams pass through M1 to generate output laser beams, the laser beams are attenuated by the attenuator and then irradiate on the CMOS, and the CMOS can detect the spot center through a centroid algorithm, so that the angle of the target relative to the base station can be deduced. In addition, the distance measurement is performed by using a TOF sensor, and the distance between the target and the base station is estimated by measuring the time of transmitting laser and receiving reflected laser.

To simultaneously power the target, the SLAPT system transmits energy to the photovoltaic cells PV in the target. Since M2 is also transmissive, a portion of the resonant beam will couple out of M2 to form a laser beam, the laser beam is incident on the photovoltaic panel, the beam power is converted to electrical energy, ready to charge a battery embedded in the target, and by means of the power source, the target can perform functions of transmitting a signal to the base station for target identification, etc. As shown in fig. 2, the present system employs an LCD shutter to transmit ID information, which allows or blocks a light beam. The battery supplies power to the MCU and the LCD driver, and whether the LCD shutter is transparent or not is judged through the coding logic, so that the CMOS can detect the state without the light spot. In this way, a sequence code can be transmitted to the base station, and the MCU and decoder embedded in the base station can identify the target by the ID code.

B. Power output

In the SLAPT system, a part of the resonance beam is output at the positioning base station for positioning, and a part of the resonance beam is output at the positioning target, and its energy is used for conversion into electric power. The invention calculates the laser output power at the positioning base station and the positioning target by adopting a circulating power model (under small output coupling approximation) based on Rigrod analysis. As shown in fig. 3 (a), the SLAPT system is assumed to have a simple uniform saturable gainA standing wave laser resonator of a medium. Intensity I of left and right traveling wave _- (z) and I ₊ (z) increases with passage through the gain medium and decreases due to intra-cavity transmission loss and output coupling loss. Under a small output coupling approximation where the reflectivities R1 and R2 of M1/M2 at the base station and target are both close to 1, the intensity I can be assumed _- (z) and I ₊ (z) remains constant along the length of the resonator: i _- (z)≈I ₊ (z)≈I _circ . According to FIG. 3 (b), once I is known _circ Given R1 and R2 close to 1, the output laser power at the positioning base station and the target can be obtained, and there are:

I _base ＝(1-n ₁ )I _circ

I _target ＝(1-R ₂ )I _circ

C. ranging scheme

In the SLAPT system, a self-triggering pulsed laser ToF sensor as shown in fig. 4 is employed to measure the ranging by measuring the time of flight of a laser pulse from the transmitter to the target and back to an Avalanche Photodiode (APD) at the transmitter. The laser pulse is first emitted from the emitter, part of the laser light is reflected by the mirrors M3 and M4, reaches the PIN photodiode, and is used to record the start time of the laser emission. Another portion of the laser pulse passes through M3 and lens L3 and is transmitted in air and reflected by a target within the field of view of the system. The reflected laser pulse then reaches the APD through lens L4 and enters a counter to count the number of laser pulses to record the stop time of laser beam transmission. If the ToF sensor transmits and receives laser pulses at intervals Δt, the distance of the target from the base station can be expressed as:

where c is the transmission speed of the laser beam in air, Δt is measured by the ToF time measuring unit, and the ranging accuracy depends on the time measuring accuracy.

As a self-triggering system, the control unit firstly triggers the laser emitting unit to emit laser pulses, one of whichA small part is received by the PIN photodiode circuit and triggers the timing circuit to start timing, and consumed circuit delay t ₁ . Another portion of the laser pulse propagates toward the target and is reflected back to the APD for a time Δt. The returned laser pulse is received by the APD and converted into an electrical signal with a circuit delay t ₂ . Setting an integer N _p As a specified number of laser pulses to be transmitted. The counting unit then emits laser pulses with a number less than N _p On the premise of outputting a trigger signal to the transmitting unit, the delay time of this process is denoted as t ₃ . Finally, the semiconductor laser diode consumes t ₄ In response, the laser pulse is again emitted toward the target. Thus, the relationship between the time at which the (n+1) th laser pulse is emitted and the time at which the nth laser pulse is emitted is expressed as:

T _n+1 ＝T _n +ΔT+τ

τ＝t ₂ +t ₃ +t ₄

known measurement time interval T _N And N _p In the case of a number of consecutive laser pulses, the estimated distance between the target and the base station can be expressed as:

the self-triggering pulse laser ranging method adopted by the invention can realize higher measurement precision and measurement speed.

D. Angle measurement scheme

In the SLAPT system, in order to obtain a beam spot on the CMOS for AoA estimation, the resonant beam intensity distribution on M1 may be calculated first, and according to the diffraction theory and the self-reproduction mode theory, the transmission process of the beam in the resonant cavity may be simulated, and finally, the beam intensity distribution of any plane in the resonant cavity may be obtained. Since the proposed system employs two retroreflectors at the transceiver, a resonant beam can still be generated as the target moves, and the location of the beam spot can change. The principle of AOA estimation is expressed below by accurately modeling the beam transport within the resonant cavity.

As shown in fig. 5 (a), in the SLAPT system, two cat-eye retro-reflectors constitute a resonant cavity. Although the two cat eyes are not completely face to face, the resonant beam can still retroreflect in the resonant cavity, and the spot position on the mirror surface can change with the movement of the receiver. For simplicity, only the movement of the receiver along the y-axis is analyzed in this example, since the movement along the x-axis is calculated in the same way. As shown in (b) of fig. 5, the resonant spot positions on the defining receivers moving in the positive y-axis direction are theoretically changed from 0 to +Δy and the beam spot positions on M1 are changed from 0 to- Δy', and the beam field distribution is u (x, y). The angle of the target with respect to the base station is denoted here as θ. Then, the output beam from the left mirror M1 impinges on CMOS with a beam intensity distribution. Thus, we first obtain a resonant beam field distribution u (x, y) over M1 in the resonant cavity.

Based on diffraction integral theory, as shown in (b) of fig. 5, the initial field distribution u at M1 is given ₀ (x, y), the beam field as it passes through the cat-eye structure, the gain medium, the free space between the gain medium and the cat-eye structure, may be correspondingly denoted as T _cat (u)，T _g (u), and T _fs (u). Then, after round-trip transmission in the cavity, the self-consistent equation of the system can be expressed as:

γu＝T _round (u)

T _roun d＝T _cat T _g T _fs T _cat T _cat T _fs T _g T _cat

according to the self-reproducing mode theory, the transmission of a beam field reflected back and forth within a resonant cavity can be equivalently the resonant beam passing through a set of apertures. The amplitude and phase of the beam field will change each time it passes through the aperture. After multiple transmissions, the lateral distribution of the beam field remains unchanged, which means that the resonant cavity forms a stable free mode. A stable resonant beam spot then appears on each element in the resonant cavity.

The above procedure can be expressed mathematically according to the Fox-Li algorithm as: given an arbitrary initial field distribution (here u is chosen ₀ (x, y) =1), onceWill become u after round trip transmission ₁ And (x, y) after t iterations, the model finally becomes a stable free current mode. Then u _t (x, y) Beam field transverse distribution and u _t+1 (x, y) is the same and only amplitude attenuation and phase lag occurs between the two beam fields. In general, when two fields are distributed u _t+1 And u _t The standard deviation of the difference between them is less than 10 ^-4 When the iteration stops.

After one time of space transmission, the light beam transmitted from M1 is transmitted to CMOS to obtain light field distribution on CMOS. The centroid position of the light spot on the CMOS can be obtained according to the centroid algorithm, and the position of the light spot on the CMOS can reflect the position of the positioning target.

E. Photoelectric conversion scheme

In the positioning objective of SLAPT systems, photovoltaic cells (PV) are used to convert beam power into electrical energy, powering the LCD modulator and controller. In order to obtain charging power from the PV, the present invention employs a PV equivalent circuit model for energy harvesting as shown in FIG. 7, which model contains a photocurrent source I _ph The forward current of one diode is denoted as I _d A shunt resistor R _sh A series resistor R _s And a load resistor R _L 。R _sh Simulating leakage current in the PV. Photovoltaic panels generally consist of a series of individual photovoltaic cells connected in series; thus, R is _s Simulating internal voltage loss due to battery interconnection, I _o And V _o Is the output current and voltage at PV, and the nonlinear relationship between them is expressed as:

I _ph related to the intensity of light incident on the PV, solve for I _o And V _o The output electric power is solved.

F. ID acquisition scheme

The present invention uses an LCD shutter to modulate a resonant beam based on linear modulation. As shown in fig. 7 (a), the LCD shutter includes two linear polarizers and oneAnd (3) liquid crystal. The linear polarizer may selectively block the light beam incident thereon according to Ma Lusi law. If the intensity of the light beam incident on the linear polarizer is I ₀ The intensity of the light beam passing through it can be expressed as I in the case where the polarization angle between the light beam and the polarizer is θ ₀ cos θ. Thus, if θ=0, the incident beam may pass through the linear polarizer, and if θ=90°, the beam is blocked. The liquid crystal layer acts as a modulator and can rotate the polarization direction of the polarized light beam. Generally, if no voltage is applied, the liquid crystal layer rotates the polarization direction of the light beam by 90 degrees, thereby blocking the light beam. On the other hand, if a voltage is applied, the liquid crystal layer does not rotate the polarization direction of the light beam. Accordingly, as shown in (a) of fig. 7, if the resonant beam reaches the target, the first linear polarizer of the LCD shutter converts the resonant beam into a linearly polarized beam, the liquid crystal layer determines a polarization angle between the beam and the second linear polarizer, and the second linear polarizer blocks or does not block the resonant beam according to the polarization angle. Accordingly, the above-described LCD shutter is "closed" (display is blackened and completely opaque) when no voltage is applied, and is "opened" (becomes transparent) if a voltage is applied.

The present invention employs OOK modulation scheme due to the non-linear nature of the LCD shutter. The symbol "1" is modulated if the CMOS detects the beam intensity, and the symbol "0" is modulated if the CMOS does not detect the beam intensity. As shown in (b) of fig. 7, if the LCD shutter is completely transparent ("on" state) due to the retro-reflective characteristics and the laser principle, the oscillation condition can be satisfied and there will be a beam intensity that can be detected by CMOS. However, if the LCD shutter is completely opaque (the "off" state), the resonant beam will be immediately cut off and the beam on the CMOS will disappear. Thus, the state of the liquid crystal shutter can be controlled by varying the voltage applied to the liquid crystal shutter, as determined by the encoding logic, so that the CMOS can detect whether there is a light spot and send a signal to the decoding module. Finally, the ID information may be sent from the target to the base station. It should be noted that the data transmission speed depends on the switching speed of the LCD. According to the latest references, the response time of the LCD can reach 1.5ms with a shutter speed of 500Hz.

The high-precision passive positioning system based on the resonance light adopts a Resonance Beam System (RBS) for an angle measurement part, and can provide certain passive safety due to the physical principle of resonance beam charging, wherein an optical path controller is used for controlling the on-off of the resonance beams on different optical paths, and specific technical details are disclosed.

The retro-reflectors in the positioning base station and the positioning target are arranged as cat eye retro-reflectors, but a pyramid prism retro-reflector or other retro-reflectors or a retro-reflector array structure can be selected in practical application. The emitting end is integrated with a photoelectric element CMOS for capturing the light spot position to deduce the angle of a positioning target, and the CMOS can be replaced by a CCD or other photoelectric elements capable of capturing the light spot position in practical application. The transmitting end integrates a laser pulse TOF sensor to perform distance measurement of a positioning target, and in practical application, TOF distance measurement can be replaced by other distance measurement algorithms such as time of arrival (TOA), time difference of arrival (TDOA), phase of arrival (POA), received Signal Strength (RSS) and the like, so that target distance measurement in a certain field angle is realized.

The ToF distance measurement and the CMOS angle measurement have errors, and given parameters in the following table, the positioning precision and the energy transmission power of the example system can be given:

table 1 parameters of example systems

Therefore, the invention can realize millimeter-level three-dimensional position coordinate acquisition of the positioning target under the field angle of 16 degrees at a distance of 2m, realize high-precision passive positioning and realize wireless power supply of watt-level power.

Claims

1. A high-precision passive positioning and energy transferring system based on resonance light beams is characterized in that the system comprises:

at least one positioning target: the device comprises a second retro-reflector serving as a retro-reflector, a photovoltaic cell PV, a battery, a second micro-processing unit, a liquid crystal switch and an LCD driving source, wherein the photovoltaic cell PV is arranged behind the second retro-reflector and used for carrying out photovoltaic power generation and battery connection, the battery respectively supplies power to the second micro-processing unit and the LCD driving source, the liquid crystal switch is arranged in front of the second retro-reflector and used for controlling the LCD driving source through the micro-processing unit to realize linear modulation of resonant beams, and the first retro-reflector and the second retro-reflector which are spatially separated form a resonant cavity of the double retro-reflector;

the first and second retro-reflectors respectively adopt a cat-eye type retro-reflector, a pyramid prism retro-reflector or an array structure composed of the retro-reflectors, when the first and second retro-reflectors adopt the cat-eye type retro-reflectors, the cat-eye type retro-reflectors are composed of reflectors and thin lenses, and the reflectors adopt reflectors with partial reflectivity;

based on the system, the stable resonance, power output, toF ranging, angle measurement, photoelectric conversion and ID information acquisition functions of the resonance light system can be realized respectively;

I _base ＝(1-R ₁ )I _circ

I _target ＝(1-R ₂ )I _circ

I _- (z)≈I ₊ (z)≈I _circ

wherein R is ₁ 、R ₂ Reflectivity of the reflector in the first and second retro-reflectors, respectively, I _base To locate the laser output power at the base station, I _target To locate the laser output power at the target, I _circ For unidirectional intensity of circulating light beam in resonant cavity, I _- (z) and I ₊ And (z) is the intensity of the left and right traveling waves.

2. The system of claim 1, wherein for stable resonance, the first retro-reflector of the positioning base station, the gain medium and the second retro-reflector at the positioning target together form a resonant optical system, the gain medium omnidirectionally transmits photons, and the dual retro-reflector resonant cavity reflects photons back and forth within the cavity, such that the photons are amplified multiple times through the gain medium, and stable resonance is established when the gain in the cavity is sufficient to compensate for transmission losses and output coupling losses in the cavity.

3. The simultaneous high-precision passive positioning and energy-transfer system of claim 1 wherein for ToF ranging using a self-triggering pulse laser ToF sensor by measuring the time of flight of a laser pulse from an emitter to a target and back to an avalanche photodiode at the emitter is:

τ＝t ₂ +t ₃ +t ₄

4. The system of claim 1, wherein for the angular measurement, after one spatial transmission, the beam transmitted from the first reflector M1 of the first retro-reflector is transmitted to the CMOS image sensor to obtain the light field distribution on the CMOS image sensor, the centroid position of the light spot on the CMOS image sensor is obtained according to the centroid algorithm, and the position of the positioning target is determined by the position of the light spot on the CMOS image sensor, so as to obtain the angle between the base station and the target.

5. The system for simultaneous high-precision passive positioning and energy transfer based on resonant beams according to claim 1, wherein for photoelectric conversion, the system converts the power of the beam passing through the second reflector in the second retro-reflector into electric energy through the photovoltaic cell PV, and obtains the nonlinear relation between the output current and the output voltage of the photovoltaic cell PV through the PV equivalent circuit model, and further calculates the output power of the photovoltaic cell PV, then:

6. The simultaneous high-precision passive positioning and energy-transfer system of claim 1 wherein the system modulates the linearly modulated resonant beam by an LCD shutter comprising two linear polarizers to selectively block the beam incident thereon and a liquid crystal as modulator, the first linear polarizer converting the resonant beam to a linearly polarized beam, the liquid crystal determining the polarization angle between the beam and the second linear polarizer, and the second linear polarizer blocking or unblocking the resonant beam depending on the polarization angle.

7. The system of claim 6, wherein for ID information acquisition, an OOK modulation scheme is used for modulation, specifically: