In the construction process, the need for the use of construction lifts for the transport of goods and personnel 1 in the construction of the lift operation, how to accurately locate the construction lift is particularly important 2. Therefore, the exact positioning of the construction lift technology has become the field of engineering At the present stage, the main methods of positioning the construction lifts include positioning method of construction lifts based on infrared sensors, positioning method of image-based construction lifts and positioning of construction hoists based on UHF RFID technology.Elevator Control Cabinet The most commonly used method is UHF RFID-based positioning of the construction lift. The positioning of the construction lift is realized by using UHF RFID tag identification technology. Assuming that the frequency of the tag transmission is too high, High, in the channel capacity of the same situation, it is prone to channel conflict 7. With the expansion of the scope of application, this conflict is obvious. At present, the anti-tag collision algorithm based on the time-slice is more popular. In the condition of high-frequency tag sending, the time slice needs to become extremely small to meet the requirements, resulting in the conflict adjustment effect is not ideal and can not meet the actual production demand 8. In order to avoid the above-mentioned shortcomings, a UHF RFID-based construction lift-point positioning method is proposed. The tag time slot estimation method is used to estimate the number of UHF RFID tags in the channel per unit time, which will lay a foundation for the anti-collision operation of the tags in the channel. By using the method of tag search, the probability of tag collision in the channel is calculated, and the anti-collision operation of UHF RFID tag is realized. In this way, the point positioning of the construction lift is completed without the conflict of labels in the channel. Experimental results show that the proposed method can effectively improve the accuracy of positioning of construction lifts.Elevator Traction System
2 Construction hoist positioning principle bookmark4 In the process of construction lift operation, assuming that the label transmission frequency is too high, the channel capacity in the case of constant, it is easy to produce channel preemption. Therefore, a label anti-collision operation is required. The anti-collision principle can be described.
3 Construction lift point location method bookmark5 The positioning of the construction lift using the traditional algorithm can not avoid the label conflict in the channel due to the high frequency of the sending label, which reduces the accuracy of the positioning of the construction lift. Therefore, this paper presents a point positioning method of construction lift based on UHF RFID.
In the process of positioning the UHF RFID construction lift, the timeslot of the construction elevator tag is set to be / = 丨 (0), / (1), / (Q-1) T, and the total number of tags is r, The transmit timeslots for these tags should be subject to the tag distribution ep / r.
According to formula (3) to calculate the number of all labels: set construction lift load is 10 meters of construction hoist run time is t, the number of tags sent at the specified time is M, the label used to send the number of channels is n All tags constitute a set of data is 1,2, all the data set is Ui channel, signed send frequency is.
In the anti-collision operation of the tag, the number of tags of the specified channel can be calculated by the following formula: The time slice of the tag for UHF RFID construction hoist can be calculated using the following formula: function, which is the tag sending speed, (4) Calculation: the number of maximum. (3), it is possible to obtain the absolute-estimate function of the label as follows: The above-mentioned formula is brought into the equation (3), and the label-cost function can be expressed by the following formula: We can get the following results: According to the method described above, it is possible to calculate the time slot of the tag transmission when the channel does not collide and send the tag through the channel to realize the control information transmission and finally finish the positioning of the construction elevator.
Construction lifts in the course of the work of the use of ultra-high frequency RFID tag identification technology, once the label transmission frequency is too high, the channel capacity unchanged, it is easy to have channel preemption. The traditional anti-tag collision algorithm based on the time-rotating discs in the construction of high-frequency tags to send tags, the time slice needs to become extremely small to meet the requirements, resulting in conflict adjustment effect is not good, thereby reducing the accuracy of positioning. According to equation (1), it can be known that if the frequency of RFID tags is increased, the number of tags will increase. According to Eq. (2), it can be known that the number of tags of the specified channel increases, which will result in shortened time slice of UHF RFID construction elevator tag transmission, resulting in lower positioning accuracy.
The maximum number of tags in the channel can be estimated according to the following formula: Calculating the number of tags in the channel: According to the method described above, the number of tags in the UHF RFID construction lift channel can be estimated to provide for the construction lift point location Accurate data foundation.
3.2 Implementation of the construction lift point positioning In the construction of UHF RFID tags based on the elevator to send the process, the control side needs to send tags to read, so the label is sent. The energy required to set the label to be transmitted is Tt and the energy required by the receiver is yv in the process of positioning the construction lift, and the energy relationship at the time of tag transmission can be expressed by the following formula: where Sp is the number of transmissions , Wp is the number of response times when the tag is sent.
Set the construction lift based on UHF RFID The number of tags in the process of point locating is p The tag transmission time slot is H The number of binary tree levels in the search process is N The number of slots can be calculated using the following formula: Nth layer binary tree tag The probability of transmission in a designated time slot can be represented by Rn. The probability that the tag is successfully transmitted in this slot can be calculated according to the following formula: In a unit time, a single tag can be calculated to be transmitted in unit time according to the following formula, and all tags can be calculated according to the following formula: Probability: In a unit time, the probability of tag collision can be calculated according to the following formula: where Rqe = H / H (Hm). In the process of tag search, the probability of tag collision per unit time can be calculated according to the following formula: 1-Rqe (H, p), according to the following formula, the label in the Nth layer binary layer search layer can be calculated in the y- The probability of collision: The number of UHF RFID tags in the channel per unit time is estimated, which will lay a foundation for the anti-collision operation of the tags in the channel. By using the method of tag search, the probability of tag collision in the channel is calculated, and the anti-collision operation of UHF RFID tag is realized. In this way, the point positioning of the construction lift is completed without the conflict of labels in the channel.
IV. EXPERIMENTAL RESULTS In order to verify the effectiveness of the UHF RFID-based point-location method for construction lifts, a simulation experiment is required. During the experiment, set the number of experiments to 100. The experimental environment can be described.
Setting During the positioning of the construction lift, the average length of data per frame in the tag to be transmitted is N = 128. During the experiment, the tag needs to be sent. The relationship between the number of tags to be transmitted and the transmission time can be expressed. According to the above formula, it is possible to obtain the probability of collision of the label, so as to realize the anti-collision operation of the label in the channel, and to transmit the label successfully. The probability of collision of the tag in the construction lift can be calculated by the following formula: To the control side, according to control needs, based on UHF RFID construction point-type positioning of the lift.
Through the method described above, the relationship between the arrival rate of the tag and the transmission frequency can be expressed in the process of positioning the construction hoist with different algorithms using the tag slot estimation method.
Successfully sent the label, you can label the contents of the construction lift control, control error can be used to describe.
Using this algorithm to carry out the positioning of construction hoist based on UHF RFID, it can quickly transfer a large number of labels to the control end, thus realizing the accurate positioning of the construction lift, which fully embodies the superiority of the algorithm. According to the above experiment, it can be known that using this algorithm to locate the construction elevator can effectively avoid the traditional algorithm due to the high frequency of sending tags caused by the frequency of the label is too high. Of the channel to seize the defect, thereby enhancing the positioning accuracy of construction lifts.
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5 Conclusion This paper presents a UHF RFID-based construction lift point positioning method. The tag time slot estimation method is used to estimate the number of UHF RFID tags in the channel per unit time, which will lay a foundation for the anti-collision operation of the tags in the channel. By using the tag search method, the probability of tag collision in the channel is calculated, and the anti-collision operation of the UHF RFID tag is realized, and the point positioning of the construction lift is completed without colliding the tags in the channel. Experimental results show that the proposed method can effectively improve the accuracy of positioning of construction lifts.
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