Surrounding line differential signal transmitting and detecting method based on GNSS (Global Navigation Satellite System) time service and CDMA (Code Division Multiple Access)

Abstract

The invention relates to a surrounding line differential signal transmitting and detecting method based on GNSS (Global Navigation Satellite System) time service and CDMA (Code Division Multiple Access). The method comprises the following steps of: initially setting; the transmitting end generates positive and negative pulse signals; the detection end collects signals and obtains information; and judging the position. Positive and negative direction states are added to a single-direction transmission pulse, ADC detection voltage value difference is carried out at a detection end, noise interference contained in maximum and minimum values is eliminated through difference operation, and the influence of a site environment on a detection effect is reduced; a sequence is added to positive and negative pulses, a chip with a previously specified length is transmitted, and a correct surrounding wire signal is obtained through decoding at a detection end, so that interference of other surrounding wires is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of lawn mower enclosure detection technology, and in particular to an enclosure differential signal transmission and detection method based on GNSS timing and spread spectrum multiple access CDMA. Background Art

[0002] Mower wire, especially for smart mowers or wire-type mowers, is a cable used to demarcate the boundaries of the mower's working area. This wire can not only help the mower identify and limit its working range, but also improve mowing efficiency and accuracy. The traditional method of demarcating the mower's wire is to use physical wire to demarcate the boundary, and to set the boundary directly on the ground with physical materials such as ropes and wires to limit the movement range of the mower, but it requires a lot of manpower costs for installation and maintenance.

[0003] With the advancement of technology, most fence-type lawn mowers currently use electronic fence lines for identification. This type of fence is usually used for smart lawn mowers. Through electromagnetic induction or signal transmission technology, the fence wire is connected through the fence signal transmitter to send out a pulse signal of a specific frequency. The changing current on the wire will generate a magnetic field, and the inductor on the detection board will be affected by the magnetic field to produce voltage changes. By collecting signals at both ends of the inductor, the boundary information and range of the working lawn can be determined, so that the lawn mower can identify and follow the boundaries defined by the fence to work. However, this solution also has some disadvantages. The detection board not only senses the signal of the transmitter, but is also easily affected by the surrounding environmental magnetic field and other transmitters. This may cause the detection signal amplitude to change abnormally, affecting the analysis and judgment, etc. In addition, if there are other fences near the fence, it will also affect the detection effect. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for transmitting and detecting a contour differential signal based on GNSS timing and spread spectrum multiple access CDMA, so as to solve one or more problems in the prior art.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA includes the following steps:

[0007] Initial setup;

[0008] The transmitting end generates positive and negative pulse signals;

[0009] The detection end collects signals and obtains information;

[0010] Position determination.

[0011] Furthermore, the initial settings include the following:

[0012] Equipped with GNSS modules at the transmitter and the detector;

[0013] Set the interval between the sending pulse and the rising or falling edge of PPS;

[0014] Set the time when the detection terminal opens the detection window.

[0015] Furthermore, the positive and negative pulse signals are generated alternately at different transmitting ends.

[0016] Furthermore, the positive and negative pulse signals generated by the transmitting end have a positive and negative sequence.

[0017] Furthermore, the positive and negative sequence is preset by introducing spread spectrum multiple access technology to send code chips with a preset length of N and a content of 1 or 0 in a cycle. When the code chip is defined as 1, it is positive first and then negative, and when the code chip is 0, it is negative first and then positive.

[0018] Furthermore, the detection end collects signals and obtains information including the following steps:

[0019] Introduce differential algorithm and collect inductor voltage signal;

[0020] Find the extreme values ​​and determine the order of precedence, the highest value represents a positive pulse, and the lowest value represents a negative pulse;

[0021] Calculate the value of the enclosure signal detection.

[0022] Furthermore, the calculated contour signal detection value is obtained by subtracting the second extreme value from the first extreme value in the current cycle.

[0023] Furthermore, the position determination comprises the following steps:

[0024] Information confirmation: Check whether the received signal is the expected signal through similarity. If not, it is considered not to exist. If so, proceed to the next step.

[0025] The surrounding signal is decoded and restored. If the code chip is 1, multiply it by positive 1. If the code chip is 0, multiply it by negative 1.

[0026] Position recognition determines whether the current machine is inside or outside the enclosure by the positive or negative value of the signal. If it is positive, it is judged to be inside the enclosure, and if it is negative, it is judged to be outside the enclosure.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0028] (I) The present invention proposes a differential signal transmission and detection scheme based on GNSS timing and spread spectrum multiple access CDMA. On the basis of the precise timing of the GNSS module, the time synchronization error between the transmitting end and the detecting end is controlled at the microsecond level, so that the transmission and detection of the differential signal can be in the same time period.

[0029] (ii) Positive and negative direction states are added to the single-directional transmission pulse, and the ADC detection voltage value is differentiated at the detection end. The noise interference contained in the maximum value is eliminated through differential operation, reducing the influence of the site environment on the detection effect.

[0030] (iii) A sequence is added to the positive and negative pulses. By transmitting code chips of a previously specified length, the correct surrounding line signal is decoded at the detection end, avoiding interference from other surrounding lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The flowchart of the method for transmitting and detecting a contour differential signal based on GNSS timing and spread spectrum multiple access CDMA according to an embodiment of the present invention is shown.

[0032] Figure 2 A schematic diagram of a line transmission and detection scheme of a line differential signal transmission and detection method based on GNSS timing and spread spectrum multiple access CDMA according to an embodiment of the present invention is shown.

[0033] Figure 3 A schematic diagram of the timing of transmitting long and short perimeter lines at the transmitting end of a perimeter differential signal transmitting and detecting method based on GNSS timing and spread spectrum multiple access CDMA according to an embodiment of the present invention is shown.

[0034] Figure 4 A schematic diagram showing the difference in PPS pulse signals of different GNSS modules in timing according to a method for transmitting and detecting a contour differential signal based on GNSS timing and spread spectrum multiple access CDMA in an embodiment of the present invention is shown.

[0035] Figure 5 A schematic diagram of a long perimeter line transmitting end sending and a detecting end detecting signal in a perimeter line differential signal transmitting and detecting method based on GNSS timing and spread spectrum multiple access CDMA according to an embodiment of the present invention is shown.

[0036] Figure 6 A schematic diagram of a short-circuit transmitting end sending and a detecting end detecting signal in a method for transmitting and detecting a circuit differential signal based on GNSS timing and spread spectrum multiple access CDMA according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present invention clearer, the following is a further detailed description of the differential signal transmission and detection method based on GNSS timing and spread spectrum multiple access CDMA proposed by the present invention in combination with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structure, proportion, size, etc. illustrated in the accompanying drawings of this specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effect that the present invention can produce and the purpose that can be achieved, should still fall within the scope of the technical content disclosed by the present invention.

[0038] This embodiment is described by taking a “lawn mower” as an example.

[0039] See also Figure 1 , a method for transmitting and detecting a differential signal based on GNSS timing and spread spectrum multiple access CDMA, comprising the following steps:

[0040] Step 1: Initial Setup:

[0041] Step 1.1: Equip the transmitter and detector with GNSS modules:

[0042] Install a transmitter module, i.e., a transmitter end, on the charging base of the lawn mower, and connect both ends of the wire of the site fence to the transmitter module as a long fence line. Similarly, install a shorter fence line under the charging pile base as a short fence line.

[0043] At the same time, multiple detection sensors, i.e., detection terminals, can be arranged at different parts of the front of the machine to provide a variety of information. In order to accurately determine the specific positional relationship between the vehicle body and the boundary of the enclosure, they can be arranged on the left and right sides of the front of the vehicle respectively.

[0044] GNSS modules are configured at both the transmitting end and the detecting end. The GNSS receiver can generate a PPS signal by solving the time information obtained by the navigation satellite signal. The PPS signal is transmitted to other devices as an accurate time reference, thereby achieving time synchronization of the entire system.

[0045] Step 1.2: Set the interval between the sending pulse and the rising or falling edge of PPS:

[0046] The accuracy and reliability of time synchronization can be ensured by setting the interval between the transmitted pulse and the rising or falling edge of the PPS. This interval should be short enough to reduce the time error caused by delay.

[0047] The PPS timing pulse signal at a specific frequency provided by the GNSS module can ensure the synchronization of the PPS time and control the error, so that the offset of the PPS rising edge or falling edge between different GNSS modules is less than 100ns.

[0048] Step 1.3: Set the time for the detection terminal to open the detection window:

[0049] See also Figure 2 , using the characteristics of GNSS timing, setting the transmission pulse with a fixed interval with the rising or falling edge of PPS, and opening the ADC detection window on the detection end, it can capture the line strength signal at this time and collect it, ensuring the synchronization of time at both ends.

[0050] Step 2: The transmitter generates positive and negative pulse signals:

[0051] Since it is necessary to detect the long fence of the site and the short fence of the charging pile, it is necessary to avoid the emission and detection timing of the two to detect the short fence signal of the charging pile to determine the location of the fence charging pile and avoid collision with the charging pile. Then the positive and negative pulse signals are staggered at different transmitting ends. Please refer to Figure 3 That is, the long fence of the site and the short fence of the charging pile avoid the time from the rising edge or falling edge of PPS, and the corresponding detection windows of the two are also avoided.

[0052] Furthermore, the positive and negative pulse signals generated by the transmitting end have a positive and negative sequence. The positive and negative sequence is introduced by the spread spectrum multiple access technology. The spread spectrum multiple access technology enables only the receiving detection module that matches the transmitting module to correctly receive and process the fence information, realizing the one-to-one matching of the transmitting and detection modules, and avoiding signal interference from other fence devices near the site. The code chips with a preset length of N and a content of 1 or 0 are sent cyclically. Please refer to Figure 4 When the code chip is defined as 1, it is first positive and then negative, and when the code chip is 0, it is first negative and then positive. The content of the code chip is generated by the corresponding well-known mapping algorithm, and a binary number is generated through the numbers in the machine's SN sequence code to obtain the code chip.

[0053] Step 3: The detection end collects signals and obtains information:

[0054] Step 3.1: Introduce the differential algorithm and collect the inductor voltage signal:

[0055] The differential algorithm can filter out environmental noise and only extract the magnetic field strength signal of the surrounding wire current. There is no need to collect environmental background noise, which reduces the impact of environmental background noise on the detection effect. The detection window of the detection device is opened, and the voltage signal at both ends of the inductor is collected to obtain the magnetic field strength information of the surrounding wire.

[0056] Step 3.2: Find the extreme values ​​and determine the order of precedence. The highest value represents a positive pulse and the lowest value represents a negative pulse:

[0057] Furthermore, the difference between the two extreme values ​​of the inductor voltage signal corresponding to the positive and negative pulses on the enclosure, namely the maximum value and the minimum value, is used to characterize the enclosure signal strength. The highest value represents the positive pulse, and the lowest value represents the negative pulse. The order in which the highest and lowest values ​​appear also represents the order in which the positive and negative pulses are sent.

[0058] Step 3.3: Calculate the detection value of the enclosure signal.

[0059] The calculated contour signal detection value is obtained by subtracting the second extreme value from the first extreme value in the current period, and the result can be positive or negative.

[0060] Step 4: Position determination:

[0061] The decoded fence signal can be used to determine whether it is a signal that matches the machine, and then determine whether the fence signal is positive or negative and whether the lawn mower is within the boundary.

[0062] 4.1: Information confirmation

[0063] Since the code piece of the previously specified length is transmitted, the correct surrounding signal should be obtained by decoding at the detection end. The received signal is detected through similarity to see whether it is the expected signal. If not, it is considered not to exist. If so, proceed to the next step.

[0064] The expected signal refers to a certain length of chips at the transmitting end, such as a length of 10, 1-0 alternating chips, which is stipulated to be jointly agreed upon by the transmitting end and the receiving end or generated by the same generation method. When the symbols are the same and the similarity meets the standard, that is, the receiving end calculates and the locally generated chips are consistent with the transmitting end, and the number of the corresponding sequence chips that are the same or opposite reaches 9 or more, the received signal is considered to be a trustworthy signal, that is, the expected signal.

[0065] Step 4.2: Decoding and restoring the enclosure signal:

[0066] The lawn mower obtains the same code chip as the transmitting end through a mapping algorithm based on its own machine serial code. Since the code chip at the transmitting end is consistent with the code chip at the detecting end, both are generated by the device serial number through a mapping algorithm. Therefore, the code chip is used to decode and restore the fence signal during the parsing process. The N original fence detection values ​​received within a period of time are decoded. If the code chip is 1, it is multiplied by positive 1. If the code chip is 0, it is multiplied by negative 1. In this way, a set of original signal steps is obtained.

[0067] Step 4.3: Location Identification:

[0068] The positive or negative value of the signal is used to determine whether the current machine is inside or outside the enclosure. Generally, the second extreme value is subtracted from the first extreme value. If it is positive, the current machine is determined to be inside the enclosure; if it is negative, the current machine is determined to be outside the enclosure.

[0069] Example 2

[0070] For the transmitter to generate positive and negative pulse signals and the detector to collect signals and obtain information:

[0071] Assume that at time t0, the fence transmitting device receives the rising edge or falling edge of the PPS signal, and after a delay of △t, it generates positive and negative pulses with pulse widths of τ and τ respectively. At the same time, at time t0, the fence detection board also receives the rising edge or falling edge of the PPS signal, and correspondingly opens a detection window with a duration of 2τ after a delay of △t. This includes the signals generated by the positive and negative pulses, and finds the extreme value by collecting the inductor voltage signal in the time period from t0+△t to t0+△t+2τ.

[0072] For details, please refer to Figure 5 and Figure 6 In a PPS pulse cycle T, the surrounding line transmitting end and the detecting end send a pulse signal and open a detection window at an interval of △t from the triggering of the rising edge or falling edge of the PPS, and the sending of the pulse signal and the opening of the detection window are set to operate simultaneously.

[0073] For a time period from the rising edge to the falling edge, assuming that the time interval from the rising edge is recorded as △t1=0, the transmitting end and the detecting end of the enclosure both receive the rising edge of the PPS timing signal, then the positive and negative pulses of the long enclosure are sent immediately after the rising edge, and the duration of the positive and negative pulses is τ respectively. A negative pulse is generated immediately after the positive pulse ends, and the total time is 2τ.

[0074] Furthermore, when the long wire positive and negative pulses are sent at the wire transmitting end, the wire detection device synchronously opens the long wire detection window, and collects the voltage extreme value signals V of the left and right inductors during this time period. 1max ,V 1min , subscript 1 represents the signal of the long fence of the site, then the final calculated and detected long fence signal value is V1=(V1max -V 1min )sign(t 1min -t 1max ), sign(t 1min -t 1max ) represents the order in which the maximum and minimum values ​​appear. 1 means the maximum value appears first and then the minimum value, and -1 means the minimum value appears first and then the maximum value.

[0075] Furthermore, it is set that the positive and negative pulses of the short line are emitted after the time interval from the rising edge is recorded as △t2 (△t2>△t1), that is, the positive and negative pulses of the short line are sent △t2 time after the rising edge arrives, and the short line is emitted after the long line signal, and the total maintenance time of the same positive and negative pulses is 2τ.

[0076] Furthermore, after the positive and negative pulses of the short-circuit are emitted on the rising edge, the short-circuit detection window of the charging pile is opened at the same time, and the voltage extreme value signals V of the left and right inductors are collected during this period. 2max ,V 2min Similarly, the final calculated detected short-circuit signal value is V2 = (V 2max -V 2min )sign(t 2min -t 2max ), sign(t 2min -t 2max ) represents the order in which the maximum and minimum values ​​appear. 1 means the maximum value appears first and then the minimum value, and -1 means the minimum value appears first and then the maximum value.

[0077] For the period from falling edge to rising edge, please continue to refer to Figure 5 and Figure 6 Similarly, the transmitting end and the detecting end are set to operate synchronously. Assuming that the time interval from the rising edge is recorded as △t1=0, the transmitting end of the enclosure immediately sends the positive and negative pulses of the long enclosure after the falling edge is triggered, and the total maintenance time of the positive and negative pulses is 2τ.

[0078] Furthermore, after the positive and negative pulses of the long wire are emitted on the falling edge, the wire detection device synchronously opens the long wire detection window, and collects the voltage extreme value signal V1′ of the left and right inductors during this time period. max ,V1′ min , subscript 1 represents the signal of the long fence of the site, then the final calculated and detected long fence signal value is V1′=(V1′ max -V1′ min )sign(t1′ min -t1′ max ), sign(t1′ min -t1′ max) represents the order in which the maximum and minimum values ​​appear. 1 means the maximum value appears first and then the minimum value, and -1 means the minimum value appears first and then the maximum value.

[0079] Furthermore, it is set that the positive and negative pulses of the short line are emitted after the time interval from the falling edge is recorded as △t2 (△t2>△t1), then the positive and negative pulses of the short line are emitted after △t2 time after the falling edge arrives, and the total maintenance time of the positive and negative pulses is 2τ.

[0080] Furthermore, after the positive and negative pulses of the short-circuit are emitted on the falling edge, the short-circuit detection window of the charging pile is opened at the same time, and the voltage extreme value signal V2′ of the left and right inductors is collected during this time period. max ,V2′ min Similarly, the final calculated detected short-circuit signal value is V2′=(V2′ max -V2′ min )sign(t2′ min -t2′ max ), sign(t2′ min -t2′ max ) represents the order in which the maximum and minimum values ​​appear. 1 means the maximum value appears first and then the minimum value, and -1 means the minimum value appears first and then the maximum value.

[0081] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA, characterized in that: The following steps are involved: Initial setup; The transmitting end generates positive and negative pulse signals; The detection end collects signals and obtains information; Position determination.

2. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 1, characterized in that: The initial setup includes the following: Equipped with GNSS modules at the transmitter and the detector; Set the interval between the sending pulse and the rising or falling edge of PPS; Set the time when the detection terminal opens the detection window.

3. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 1, characterized in that: The positive and negative pulse signals are generated alternately at different transmitting ends.

4. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 3, characterized in that: The positive and negative pulse signals generated by the transmitting end have a positive and negative sequence.

5. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 4, characterized in that: The positive and negative sequence is preset by introducing spread spectrum multiple access technology with a length of N and a code chip with a content of 1 or 0 that is sent cyclically. When the code chip is defined as 1, it is positive first and then negative, and when the code chip is 0, it is negative first and then positive.

6. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 1, characterized in that: The detection end collects signals and obtains information including the following steps: Introduce differential algorithm and collect inductor voltage signal; Find the extreme values ​​and determine the order of precedence. The highest value represents a positive pulse and the lowest value represents a negative pulse. Calculate the detection value of the surrounding signal.

7. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 6, characterized in that: The calculated contour signal detection value is obtained by subtracting the second extreme value from the first extreme value in the current cycle.

8. The method for transmitting and detecting differential signals based on GNSS timing and spread spectrum multiple access CDMA as claimed in claim 1, characterized in that The position determination comprises the following steps: Information confirmation: Check whether the received signal is the expected signal through similarity. If not, it is considered not to exist. If so, proceed to the next step. The surrounding signal is decoded and restored. If the code chip is 1, multiply it by positive 1. If the code chip is 0, multiply it by negative 1. Position recognition determines whether the current machine is inside or outside the enclosure by the positive or negative value of the signal. If it is positive, it is judged to be inside the enclosure, and if it is negative, it is judged to be outside the enclosure.

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