Patent Application
20190162846
Disclosed embodiments relate generally to the field of distance measurements. More particularly, and not by way of any limitation, the present disclosure is directed to methods and an electronic device for dynamic distance measurements.
Providing dynamic measurements of distances that can have a large relative range can be accomplished using an Analog to Digital Converter (ADC), and an ultrasonic transducer to measure Time of Flight (TOF) of a signal. In this situation, ADC-based TOF can provide high resolution, but can require a very long sampling period to cover a relatively large TOF range. The long sampling period incurs high power consumption and requires large amounts of memory. In many situations, such a large capture window can increase system cost and/or limit the distance range, while being unable to provide the needed temporal resolution due to limitations on power and memory. Improvements are needed.
Disclosed embodiments provide methodologies that provide a rough knowledge of the anticipated arrival time of a measurement pulses in a signal. Using the anticipated arrival time, the high resolution data sampling period can be triggered just prior to the anticipated arrival time of the measurement pulses, allowing the length of time that the ADC window is open to both be based on the length of the measurement pulses and to remain constant regardless of the distance to measure. Several example methods to accomplish this task are disclosed, as well as an electronic device capable of performing the methods. The disclosed methods can provide one or more of the following advantages: lower power consumption, lower memory requirements, and faster tracking without increasing system cost and power consumption.
In one aspect, an embodiment of an electronic device for providing distance measurements is disclosed. The electronic device includes a first connector for coupling to a transmitter; a second connector for coupling to a receiver to receive a signal; a pulse generator coupled to provide pulses to the first connector; a memory; an analog-to-digital converter (ADC) coupled to the second connector, the ADC being coupled to convert a received signal to a stream of digital data for storage in the memory; a timer; a comparator coupled to compare the signal to a threshold value; a processing unit coupled to each of the pulse generator, the memory, the ADC, the timer and the comparator; and instructions stored in the memory that when performed by the processing unit, performs a method that comprises determining an estimated time of arrival of a series of measurement pulses in the signal and turning on, prior to the estimated time of arrival, the ADC to capture the series of measurement pulses, wherein the ADC operates at a first resolution provided by sampling the signal at a rate equal to or greater than the Nyquist rate and the ADC remains on for a fixed period of time that is sized to capture the series of measurement pulses.
In another aspect, an embodiment of a non-transitory computer readable medium having a sequence of program instructions which, when executed by a processing unit in an electronic device that is coupled to a transceiver and that comprises a pulse generator and an analog-to-digital converter (ADC), perform a method for providing distance measurements is disclosed. The method on the non-transitory computer readable medium includes determining, at an electronic device coupled to a receiver, an estimated time of arrival of a series of measurement pulses in a signal; and turning on, prior to the estimated time of arrival, an analog-to-digital converter (ADC) to capture the series of measurement pulses, wherein the ADC has a first resolution provided by sampling the signal at a rate equal to or greater than the Nyquist rate and the ADC remains on for a fixed time period that is sized to capture the series of measurement pulses.
Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that different references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references may mean at least one. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. As used herein, the term “couple” or “couples” is intended to mean either an indirect or direct electrical connection unless qualified as in “communicably coupled” which may include wireless connections. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.
The accompanying drawings are incorporated into and form a part of the specification to illustrate one or more exemplary embodiments of the present disclosure. Various advantages and features of the disclosure will be understood from the following Detailed Description taken in connection with the appended claims and with reference to the attached drawing figures in which:
Specific embodiments of the invention will now be described in detail with reference to the accompanying figures. In the following detailed description of embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.
To determine the location of target 1008, measuring system 1010 causes transceiver 1002 to transmit an outgoing signal 1006A that contains a series of transmitted pulses 1012A. In order to achieve the best resolution, outgoing signal 1006A is sent at an ultrasonic frequency, which may be, for example, 1 MHz. At some point within the range 1004, outgoing signal 1006A strikes target 1008. Some portion of outgoing signal 1006A is reflected back towards transceiver 1002 as reflected signal 1006B and the pulses look similar to the series of reflected pulses 1012B. As long as the level of paper changes slowly, measuring system 1010 can estimate the current location of the target 1008 by searching for series of reflected pulses 1012B in a narrow time frame. If, however, a handful of paper is added to or removed from the tray all at once, measuring system 1010 will generally need to search across the entire range of possible locations to determine where the target 1008 is currently located. How costly this search is depends on the method of measuring distances to the target.
In one method, known as Time-to-Digital Conversion (TDC), a counter is started when the series of pulses 1012A are transmitted. The reflected series of pulses 1012B are detected by measuring system 1010 by comparing reflected signal 1006B to a threshold. When reflected signal 1006B exceeds the threshold, the counter is stopped and the total count is converted to a digital value that is proportional to the distance to the target. In a second, ADC-based method, after sending outgoing signal 1006A, measuring system 1010 stores a digital copy of the reflected signal 1006B for the entire period of time in which series of reflected pulses 1012B might be located. Software is then utilized to examine the stored copy of reflected signal 1006B and locate the beginning of series of reflected pulses 1012B. The ADC-based method is able to determine the distance to target 1008 with greater resolution than TDC measurements, but when the range is large, the costs in terms of memory needed and power consumed in determining the start of the signal are also large.
The electronic device and methods disclosed in this application address the long range by determining a rough time that series of reflected pulses 1012B will arrive at measuring system 1010 and turning on the ADC-based method shortly before the pulses are expected to arrive. The time frame for the signal capture is fixed and extends only long enough to capture the returning pulses.
Performance of instructions 128 by processing unit 124 causes pulse generator 114 to be triggered to send pulses 108 through SPI 116, where they are sent to transceiver 104 to be broadcast. When TDC is being utilized to measure the distance to target 110, timer 120 is started when transmitted pulses 108 are sent; then when reflected pulses 109 are detected by comparison to a threshold at comparator 118, timer 120 is stopped and the distance to target 110 is determined. When ADC 122 is being utilized to determine the distance to target 110, the reflected signal is converted to digital information and stored in memory 126, where the digital information can be analyzed by processing unit 124 to determine the start of reflected pulses 109 and therefore the distance to target 110.
Instructions 128 are directed to the method 200 shown in
In addition to determining the distance to a top sheet of paper in a paper tray and thus the number of sheets remaining in the tray, system 100 combined with method 200 can be utilized for determining distance in many other situations. For example, system 100 can be utilized to measure the distance, within a humidifier, to the surface of the water in a reservoir, demonstrating how full the reservoir is. The level of other liquids, such as gasoline, can also be measured. Mounted a few feet above the ground behind a tractor, system 100 can measure the depth of a furrow being plowed by the tractor. System 100 can also be utilized in collision avoidance systems, such as in an automobile, drone or other vehicle. For the longer distances, such as needed by a drone, ultrasonic wavelengths become impractical due to their attenuation over larger distances. Lower wavelengths can be utilized, e.g., 20-40 KHz, which do not suffer as much attenuation as ultrasonic frequencies, but which cannot provide the same high degree of accuracy as with ultrasonic frequencies.
In diagram 300, a series of pulses 302A are transmitted beginning at time T0 by transceiver 104. Although five pulses are shown in this and the following examples, typically a series of 15-30 pulses are sent. Starting at a time T1, which represents the earliest time that reflected pulses 304A could possibly return, rough ADC sampling window 306 is opened by performing sampling at considerably less than the Nyquist rate and feeding the samples to ADC 122 for conversion and storage. While this sampling rate may miss the start of the pulses being measured, the pulses can be detected in successive samples and a rough TOF for the pulses can be determined. Because of the low sampling rate, the rough ADC sampling window 306 can remain on for the entire period in which reflected pulses 304A may possibly appear. In an alternate embodiment, once the reflected pulses 304A has been recognized, rough ADC sampling window 306 can be closed at time T2.
At time T3, a second series of pulses 302B is transmitted from transceiver 104. Since the time of transmission of transmitted pulses 302B is known and the rough TOF of transmitted pulses 302A is known, the TOF of transmitted pulses 302B can be estimated from these two values and adjusted for possible errors in the detection of reflected pulses 304A. ADC 122 can then be triggered at time T4 to open ADC sampling window 308. For this second measurement, reflected pulses 304B are sampled at the Nyquist rate or higher in order to provide a determination of the TOF of transmitted pulses 302B that is of the desired resolution. ADC sampling window 308 will be turned on for a fixed length of time that has been determined to be sufficient to contain reflected pulses 304B, then terminated at time T5.
Shortly thereafter, a second series of pulses 602B are sent by transceiver 104 at time T2. The time T2 can be added to the TOF for transmitted pulses 602A to determine an expected time of arrival of the series of reflected pulses 604B. This expected time is not entirely accurate, but provides enough accuracy that the sampling window necessary to detect the reflected pulses 604B is much smaller than the entire range. That, is, the ADC can be triggered to open ADC sampling window 608 at a time T3, which is slightly less than time T2 plus the estimated TOF as corrected to account for inaccuracies in the initial measurements. It will be understood that this expected time of arrival of reflected pulses 604B can be adjusted as necessary to ensure that the ADC-based method is operating when reflected pulses 604B arrive. Since the time of arrival of reflected pulses 604B is generally known, ADC 122 is turned on at time T3, opening ADC sampling window 608 to capture reflected pulses 604B and can be turned off at T4, a fixed time later, saving both memory space and power. As in the first method, a cross-correlation between the transmitted pulses 602B and received pulses 604B can then be utilized to determine the TOF with the desired accuracy.
Once the preliminary pulse 801 is transmitted, comparator 118 starts comparing the signal from amplifier 106 to a threshold value. The value of reflected preliminary pulse 803 crosses this threshold at a time T1. When the crossing of the threshold is detected, timer 120 is turned on. It is known that the reflected series of pulses 804 will follow reflected preliminary pulse 803 by a time interval that is equal to TINT1. Therefore, timer 120 times for a second interval TINT2 that is slightly less than TINT1. TINT2 can be adjusted as necessary to ensure that the reflected series of pulses 804 will be captured in the ADC capture window. When second interval TINT2 ends, processing unit 124 turns on ADC 122 to provide ADC sampling window 808, which is able to capture the entire reflected series of pulses 804 and determine the TOF of the series of pulses 802 very accurately. As in the previous examples, ADC 122 is able to be turned on for a fixed period of time and will sample the reflected signal at the Nyquist rate or higher.
At least some example embodiments are described herein with reference to block diagrams and/or flowchart illustrations of computer-implemented methods, and/or computer program products. These computer-implemented methods can be stored as computer program instructions in a non-transitory tangible computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the functions/acts specified in the block diagrams and/or flowchart block or blocks.
In at least some additional or alternative implementations, the functions/acts described in the blocks may occur out of the order shown in the flowcharts. For example, two blocks shown in succession may be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Moreover, the functionality of a given block of the flowcharts and/or block diagrams may be separated into multiple blocks and/or the functionality of two or more blocks of the flowcharts and/or block diagrams may be at least partially integrated. Finally, other blocks may be added/inserted between the blocks that are illustrated.
Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above Detailed Description should be read as implying that any particular component, element, step, act, or function is essential such that it must be included in the scope of the claims. Reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Accordingly, those skilled in the art will recognize that the exemplary embodiments described herein can be practiced with various modifications and alterations within the spirit and scope of the claims appended below.
