Solar sensor and method to detect the position of the sun with respect to the transverse axis of the

专利摘要:
Solar sensor and method to detect the position of the sun with respect to its transverse axis. The invention consists of a solar sensor with a matrix of pixels that measure the luminous intensity. The reading of the pixels is asynchronous and based on the communication protocol Address Event Representation. The pixels send asynchronously to the outside events with a frequency proportional to the luminous intensity. Each pixel can, at most, fire once after an initial reset (Time-to-first-spike). The AER communication logic is modified to allow a maximum programmable number of pixels that fire. The calculation of the position of the Sun is made by means of a digital block of computation that determines the centroid of the most illuminated pixels and that are the only ones that send information. The scientific-technical area of the invention is that of physical technologies, specifically microelectronics.
公开号:ES2675048A1
申请号:ES201601091
申请日:2016-12-22
公开日:2018-07-06
发明作者:Juan Antonio LEÑERO BARDALLO
申请人:Universidad de Cadiz；
IPC主号:

专利说明:

SOLAR SENSOR AND METHOD TO DETECT THE POSITION OF THE SUN REPECTED TO THE TRANSVERSAL AXIS OF THE SAME.
SECTOR OF THE TECHNIQUE.
The proposed invention falls within the discipline of technologies
5 physical Particularly within the area of microelectronic design of optical sensors in standard eMOS technology. The invention is intended to be used to detect the position of the Sun with respect to its transverse axis. The industrial sectors in which the invention can be applied are several:
- Industry dedicated to the generation of electric energy from energy
10 solar, for any of the variants that exist and that require to know with precision the position of the Sun, to optimize the generation of energy, by means of the suitable positioning of the devices dedicated to it: panels, solar reflectors, etc.
- Space navigation systems that require knowing the relative position 15 of the Sun to orient and move through space: satellites, space probes, space rockets, etc.
- Home automation applications that require knowing the position of the Sun to program and configure electromechanical devices present in the home.
- Meteorological systems that require knowing the position of the Sun and the intensity of the radiation emitted by it.
- Therefore, any industrial sector that requires systems for measuring the position of the Sun.

STATE OF THE TECHNIQUE.
Existing solar sensors can be cataloged into two major fundamental groups: digital and analog.
Digital sensors are based on vectors [A. AIi and F. Tanveer, "Low-cost design and development of 2-axis digital sun sensor," in Journal of 5pace Technology, vol. 1, VI 2011); [JP PatentJPH0299811] or pixel arrays [N. Xie and A. Theuwissen, "A miniaturized micro-digital sun sensor bymeans of lowpower low-noise CM05 imager," 5ensors Journal, IEEE, vol. 14, no. 1, pp. 96-103, Jan 2014.]; [and. Liebe and S. Mobasser, "Mems based sun sensor," in Aerospace Conference, IEEE Proceedings., Vol. 3, 2001, pp. 3 / 1565-3 / 1572.]; that measure the light intensity of a visual scene. These values are read sequentially (one by one). Later they are digitized and processed to determine the position of the Sun in the scene, based on algorithms that look for the position of the star in the image. The main limitation of these sensors is that they need to read and process all the output values of all pixels. This entails a high response time and excessive power consumption, due to the algorithms that determine the position of the Sun. Comparing implementations based on pixel vectors with those based on pixel matrices, it should be noted that the former, although they are simpler and occupy less area, require a much more precise and dedicated optics, to illuminate the pixel vector. In contrast, pixel arrays occupy more area, but do not require such a complex optics.
The analog sensors consist of a small group of photodiodes. The position of the Sun is determined based on the ratios of the photodiode currents [F. Delgado, J. Quero, J. Garcia, e. Tarrida, P. Ortega, and S. Bermejo, "Accurate and wide-field-of-view mems-based sun sensor for industrial applications," Industrial Electronics, IEEE Transactions on, vol. 59 no. 12, pp. 4871-4880, Dec 2012); [P. Ortega, G. López-Rodríguez, J. Ricart, M. Domínguez, L. Castañer, J. Quera, C. Tarrida, J. García, M. Reina, A. Gras, and M. Angula, "A miniaturized two axis sun sensor for attitude control of nano-satellites, "5ensors Journal, IEEE, vol. 10 no. 10, pp. 1623-1632, Oct 2010.). These sensors are fast and simple. Their main limitation is that they are not robust to distractors present in the scene. That is, they can confuse the Sun with other sources of light present in the environment. In addition, the process of processing low intensity photocurrents limits their accuracy. Another limitation they have is that they usually make use of optics designed specifically for them, which makes the product more expensive and limits the applicability of the devices.
We have not found reported solar sensors, based on pixel matrices and with a simple optics, that combine the advantages of both families of existing sensors: reliability, in the case of digital, and low response time and low computational cost, in the analog case. The present invention proposes to use a matrix of pixels similar to that of digital sensors, but which generate a reduced data flow, with a low response time, as well as analog ones. For this, it is proposed to use pixels that can send information based on events asynchronously at any time, through a shared bus using the Address Event Representation (AER) communication protocol. The pixels will follow the discipline Time-to-First-5pike (TF5): maximum one event per pixel; and the Winner Take AII (WTA) discipline: only a small number of pixels are allowed to shoot. The calculation of the position of the Sun will be done by computing the centroid of the pixels that have fired. If a certain number of events is not received during a time interval, the position of the Sun will be calculated using the available information. The sensor will make use of a simple commercial and low cost optics. The pixel matrix dimension will be chosen to be compatible with standard optics. DESCRIPTION OF THE INVENTION.
The Sun is the largest and brightest celestial body in the solar system. For this reason, many space navigation systems take it as a reference when traveling and orienting. Proper operation of these systems requires determining the position of the Sun quickly, accurately and reliably. In addition, a low power consumption of the ordered systems is desirable.
A solar sensor based on a matrix of pixels of dimensions MxN with M> l and N> l and a simple wide-angle lens is proposed. The pixels that form the sensor matrix have the particularity that, after an initial reset, they trigger pulses with a frequency proportional to the light intensity. Those pixels that detect more light shoot first and, at most, once, according to the discipline Time-to-First-5pike (TF5). Pixels generate information asynchronously that they send using the Address Event Rep resentation (AER) protocol abroad. When a pixel generates a pulse, it requests access to a shared bus in order to send information about its spatial location (X-Y coordinates). Next, the module in charge of receiving said information stores the address of the pixel that has been triggered and returns an assent to that pixel, to indicate that the communication process is over. At that time, the pixel will remain inactive until the next global reset. In the event that two pixels shoot simultaneously, a set of peripheral arbitrators will ensure that only one of them has access to the bus, while the other waits to be serviced.
In the proposed invention, the peripheral circuitry performs two novel functions. The first one is to let only a certain number of pixels shoot. The user can program a maximum number of pixels that can send information outside, so that those that detect the most intense light source (the Sun in this case) are the only ones that send information outside. The luminous intensity of the pixels that they shoot will be coded according to the time elapsed from the global reset until their firing. If after a while, there is not a sufficient number of pixels that have fired, the Sun will be estimated, based on the information available at that time (timer function). The second of the functions is to determine the position of the Sun, from the shots of the matrix pixels.
On the periphery of the pixel matrix, there will be three blocks of digital circuitry. The first one will be in charge of managing the asynchronous digital communication between the pixel matrix and another digital block responsible for determining the position of the Sun. The second of the blocks is a programmable counter / timer that allows counting the number of pixels that have been sent information outside and stop the operation of the pixel array, once a certain number of shots has been received. The third of the blocks is responsible for calculating the pixel that corresponds to the common centroid of the pixels that have fired. The position of the Sun with respect to the axis of the sensor will be determined by a simple calculation of the inverse tangent of the quotient of the X-y coordinates of said pixel.
As for the physical implementation of the system, it is proposed to make use of a low-cost commercial wide-angle (fisheye) optic that can be easily replaced. The sensor must be placed on a flat surface, covered with an opaque housing and with the optics attached to it. The fact that the optics are standard, will give the user flexibility when adapting the sensor to the environment where you want to use. For example, in solar power plants, the optics can be chosen based on the space region where the position of the Sun is to be detected. The objective will focus the points, above the horizon, from the East to the West, through which the Sun can move throughout the day.
The advantages of the proposed invention, compared to the current state of the art, are several. With respect to digital sensors, as the number of pixels that send information is reduced, the computational cost of processing is much lower. Another advantage is that the pixels send the information immediately and asynchronously. It is not necessary to read each of the pixels of the matrix, as is done with a traditional approach, so the response time is much faster. With respect to analog sensors, having a matrix of pixels, the system is more robust to possible failures, by confusing other light sources in the scene with the Sun. Also when working with digital pulses, the system is more robust to noise and to the tolerances of the electronic components during the manufacturing process. In addition, the optics we intend to use is simple and compatible with commercial lenses, which lowers the total cost of the system, being an advantage over sensors based on pixel vectors.
DESCRIPTION OF THE CONTENT OF THE FIGURES.
To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of figures is attached as an integral part of this description. in which, by way of illustration and not limitation, the following has been represented:
Figure 1: A possible electrical implementation of the pixels that make up the pixel matrix is presented. The pixels follow the Integrate-and-Fire (I&F) scheme, that is, after the activation of a global reset signal (1) they integrate load into an integration capability (2). When the voltage in it reaches a certain value, by means of a comparator (3), the pixels activate an output digital signal (4) that initiates the transmission of the pixel address (X-Y coordinates), following the AER communication protocol. For this, the digital communication signals (5), (6), (7), (8) and (9) are activated, as established by the protocol. When your request has been answered by the periphery, a signal indicated by the AER logic that ends the communication is stored in an analog memory (10). From that moment, the pixel is blocked by a digital signal (11), connected to the Mn2 transistor door •
Figure 2: a description of system blocks and theirinterconnected It consists of an array of pixels (12) that measure the intensitybright; Arbitrators, decoders, and digital logic of rows (13) andArbitrators, decoders, and digital logic of the columns (14), whichmanage AER communication by rows and columns, respectively; a. programmable counter / timer (15) that counts the number of pixels thathas triggered and blocks the pixel array, when the value is reachedsettled down; and a digital computing block (16), which computes the angle of the Sun
with respect to the transverse axis of the sensor.
Figure 3: On the left, the elevation (17) of a system implementation is shown. It consists of an opaque housing (18) that covers it and protects the electronic part of the sensor (19). In addition, the housing is used to couple the optics (20) to the device. The centroid of the sensor electronics is aligned with the optics (20), which is coupled by screwing the optics to the housing. Focal length and thread type will be required for some of the existing standards: Cmount, CS-mount, T-mount, etc. The field of view of the sensor (21) is determined by the chosen optics, preferably wide angle. On the right, the sensor floor (22) is shown. It is appreciated that the centroid of the sensor electronics is aligned with the optics.
Figure 4: It shows how a visual scene, in which the Sun appears, is detected, by the pixel matrix. The sensor and optics must be positioned so that the horizon (23) appears aligned with the first row of pixels. The pixels will detect the lighting above the horizon. Those who detect sunlight will be the most illuminated and send their position abroad. To determine the position of the Sun (24), the centroid of the pixels that have fired will be calculated. The angle indicating the position of the Sun (25) is calculated based on the centroid. The zenit (26) must correspond to the angle (OQ). The size of the pixel matrix should be such that the Sun illuminates the pixel of coordinates (O, M), the day of the year in which it is at the highest point on the horizon line.
Figure 5: A possible implementation of the system to detect the position of the Sun on the horizon is shown. The sensor is placed on a pole (27), focusing the horizon (23), from East to West. Everything below the horizon should not appear in the visual scene, for this the height of the pole will be adjusted, the zenith (26) being the highest point at which the Sun can be detected. MODE OF CARRYING OUT THE INVENTION.
As a preferred embodiment of the sensor, we will consider Figure 1, where the implementation of the pixels is illustrated. After activating a global reset signal (1), at a high level at the gates of the transistors Mn1 YM n3 And at a low level at the gate of the transistor Mp1, the pixels integrate charge into an integration capacity (2), until the voltage reaches a certain value. At that time, a comparator (3) activates a digital output signal (4), requesting access to the AER bus to transmit pixel coordinates. The digital communication signals (5), (6), (7), (8), (9) are activated or received, depending on whether they are input or output, based on the AER communication protocol. Once the event sent by the pixel has been received, a digital value is stored in an analog memory (10), which blocks the pixel, by activating a digital signal (11) at the Mn2 transistor gate, until a new global reset (1) is received, following the discipline Time-toFirst-5pike (TF5).
A block diagram of the complete system is illustrated in Figure 2. The rows of the pixel matrix (12) are connected to arbitrators, decoders and digital logic of the rows (13), which are responsible for the arbitration and transmission of events, according to the AER communication protocol. The columns of the pixel matrix are connected to arbitrators, decoders and digital logic of the columns (14). Each event causes the outputs of the digital decoders to match the coordinates (row and column number) of the pixel it has fired. In addition, the system consists of a programmable counter / timer (15) that counts the maximum number of pixels it has triggered, after the global reset (1) of the matrix pixels. When the number of events transmitted reaches the maximum value that the programmable counter / timer allows, it blocks the pixel matrix and the AER communication system. Therefore, the programmable counter / timer imposes limits the number of pixels that shoot according to the WTA discipline. In addition, the programmable counter / timer activates the digital computation block (16), which determines the position of the Sun. This block stores the coordinates of the pixels that have fired and computes the centroid of the pixels that have sent events outside. The angle that indicates the position of the Sun with respect to the transverse axis of the sensor is calculated based on the inverse tangent of the quotient between the Y / X coordinates of the centroid.
In Figure 3, a physical implementation of the complete sensor is shown. On the left is the elevation (17) of a system implementation. It includes an opaque housing (18) to protect and cover the electronic part of the sensor (19) and fix the optics (20). The centroids of the electronic part of the sensor and the lens are perfectly aligned. The optics are screwed to the housing. Focal length and thread type are chosen to be compatible with a commercial standard: C-mount, C5-mount, T-mount, etc. The field of view of the sensor (21) will be determined by the optics. Preferably it should be wide angle. On the right, the sensor plant (22) is presented.
Figure 4 shows how a typical visual scene should appear on the pixels of the sensor. The sensor should focus on the horizon (23), from East to West. The horizon must be below the pixel matrix, so that the pixels only feel the points that are above the horizon. The position of the Sun (24) will vary throughout the day from East to West. The brightest point of the visual scene must correspond to the Sun. Therefore, the visual scene must not contain distracting elements, that is, additional light sources to the Sun. The angle indicating the position of the Sun (25) that must be calculated to determine the position of the Sun, based on the coordinates of the centroid of the Sun. For a correct operation of the sensor on the day of the year when the Sun is at its highest point, the zenith (26), the pixel that corresponds to that position (O, M), it should be the one that detects more light intensity at noon.
Figure 5 illustrates how the solar sensor should be positioned for proper operation. A pole (27) must be used to adjust the height of the sensor. So that the pixels detect the illumination of all the points that are above the horizon (23). The optics should focus on the points above the horizon through which the Sun can move throughout the day throughout the year. To optimize operation, the Zenith (26) must be the highest point where the sensor can detect the position of the Sun. INDUSTRIAL APPLICATION
The invention is intended for industrial applications. We can cite the following possible industrial applications of it:
- Any type of thermal or electrical power plant that requires to know the position of the Sun precisely, to position its sensors or elements, so that the generation of energy is maximized, depending on the position of the Sun.
5-Navigation systems that require to know quickly and precisely the relative position of the Sun, to orient in space.
- Home automation applications that require knowing the position of the Sun to program and configure electromechanical devices present in the home.
- Meteorological systems that require knowing the position of the Sun and the intensity of the radiation emitted by it.
- Therefore, any industrial sector that requires systems for measuring the position of the Sun.

权利要求:
Claims (5)
[1]
l. Solar sensor to detect the position of the Sun with respect to the transverse axis of the same one that includes the following constituent blocks: i) matrix of pixels (12) of dimension MxN, with M> l and N> l, whose
5 pixels generate asynchronous pulses after an initial reset, with a frequency proportional to the light intensity and transmits them via the AER (Address Event Representation) communication protocol, via a shared bus, the number of pulses per pixel being limited, such as maximum one. Pixels
10 encode the levels of light intensity of the scene according to the discipline Time-to-First-5pike (TF5), which consists in that the most illuminated pixels send information before the less illuminated ones. ii) Arbitrators, decoders, and digital logic of rows (13) and
15 Arbitrators, decoders, and digital logic of the columns (14), to arbitrate and manage the access of a matrix of pixels to a shared bus, according to the AER communication protocol, which are interconnected to the pixel matrix. iii) Programmable counter / timer (15) that counts a
20 maximum number of events, until you reset the pixel matrix and the AER logic, to restrict the maximum number of pixels that send information abroad, according to the discipline Winner Takes it Al! (WTA), with a maximum programmable number of pixels that can generate events. iv) Digital block of computation (16), for the calculation of the centroid of the Sun based on the coordinates of the pixels that have sent events abroad, once the programmable counter / timer has reached its maximum value. The block calculates from the centroid of angle that
It forms the Sun with the transverse axis of the sensor and returns a digital value.
[2]
2. Solar sensor to detect the position of the Sun with respect to the transverse axis thereof, according to Claim 1, characterized in that the pixels of the pixel matrix (12) are implemented, incorporating:
i) An integration capability (2), where load is integrated, after a global reset (1). ii) A comparator (3) used to activate a digital output signal (4) that activates digital communication signals (5), (6), (7), (8) Y (9), which transmit the signals abroad. pixel coordinates that you shot. iii) An analog memory (10).
[3]
3. Procedure for detecting the angle of the Sun, with respect to the transverse axis of a solar sensor, for solar sensors based on the implementation described in Claim 1, which consists of:
i) Computation of the common centroid of the coordinates of the pixels that have generated pulses asynchronously during an established time interval. ii) Computation of the arc-tangent of the X-y coordinates of the centroid of the coordinates of the pixels that have transmitted pulses abroad. iii) Determination of the position of the Sun based on the value of the previous angle.
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ES201601091A|ES2675048B1|2016-12-22|2016-12-22|Solar sensor and method to detect the position of the sun with respect to the transverse axis of the sun.|ES201601091A| ES2675048B1|2016-12-22|2016-12-22|Solar sensor and method to detect the position of the sun with respect to the transverse axis of the sun.|