System and method for acquiring bus passenger flow information

[0055] Examples:

[0056] This embodiment uses the technical scheme of the present invention to construct a bus passenger flow information collection system. The dual-core RFID bus card is used as a citizen public transportation bus card, and a vehicle information collection subsystem is installed on each bus of the bus system. .

[0057] In the system, the dual-core RFID travel card includes a passive RFID tag, a wake-up circuit and an active RFID tag that are electrically connected in sequence. Passive RFID tags are obtained from commercially available mature products. The working frequency of the RFID chip in the passive RFID tags is 13.56MHz and follows the ISO14443 protocol. The active RFID tag is developed and obtained by using the commercially available wireless transmission control chip CC2510 as the core. The CC2510 chip contains an 8-bit MCU (ie 8051), a 2.4GHz radio frequency transceiver (its data transmission and reception rate is 250kbps), and a 32 KB Programmable flash memory and a 4 KB RAM memory. It also contains analog/digital converter (A/DC), timer (Timer), AES128 co-processor, etc. The CC2510 chip can set sleep mode, and only when in sleep mode With 0.5μA current consumption, the time to wake up from sleep mode to working state is also very short, and external interrupts or the internal RTC (Real Time Clock) of the chip can wake up to working state, which is especially suitable for requiring battery life Longer application environment; this embodiment uses the external interrupt pin INT of the CC2510 chip as a wake-up trigger terminal. The wake-up circuit is mainly composed of energy storage capacitor C2 and switching transistor Q, such as image 3 Shown in image 3 Where L and C1 represent the inductive antenna and resonant capacitor of the passive RFID tag respectively. The inductive antenna L and the resonant capacitor C1 form an LC oscillation circuit and its oscillation frequency is 13.56MHz; the two ends of the energy storage capacitor C2 are connected to the passive RFID Both ends of the tag’s inductive antenna L, and one end of the connection is provided with a unidirectional conducting diode D, and the two ends of the energy storage capacitor C2 are also connected to the base and emitter of the switching transistor Q; the switching transistor Q The collector is connected to the INT terminal of the CC2510 chip and then connected to the power supply VCC through a current-limiting resistor, while the emitter of the switching transistor Q is grounded to GND; when the passive RFID tag senses the radio frequency signal and generates an induced current, the induced current will pass After the unidirectional conducting diode D is accumulated in the energy storage capacitor C2, when the voltage across the energy storage capacitor C2 is large enough, the switching transistor Q will be turned on, thereby causing a voltage drop change on the collector of the switching transistor Q. This voltage drops The edge is used as a wake-up trigger signal. When the INT terminal of the CC2510 chip receives the wake-up trigger signal, it wakes up to the working state, thereby achieving the function of waking up the active RFID tag.

[0058] The vehicle information collection subsystem in the system includes a geographic positioning module, a first RFID reader, a second RFID reader, a data collection module, and a wireless communication module. In this embodiment, both the geolocation module and the first RFID reader are commercially available mature products; the wireless transmission control chip CC2510, memory and peripheral circuits are used to develop the functions of the second RFID reader and data acquisition module, namely In this embodiment, the second RFID reader and the data collection module are integrated into one, and this design is mainly to save hardware costs; the first RFID reader and the second RFID reader are connected through a serial port to realize data communication; wireless communication The module is realized by the commercially available GPRS data remote transmission module. At the same time, in the bus passenger flow information collection system of this embodiment, the upper limit number of unanswered times K=3, the polling period Tp=10s, and the offline time limit Tout=30s.

[0059] The specific process of the system for collecting bus passenger flow information is as follows:

[0060] 1) The first RFID reader sends out radio frequency card reading signals;

[0061] 2) When the dual-core RFID travel card is close to the first RFID reader until the passive RFID tag senses a sufficient strength of the RF card reading signal, the stored tag ID is sent to the first RFID reader by the induced current, and the circuit is awakened at the same time. The passive RFID tag senses the induced current obtained by the radio frequency signal with sufficient strength to trigger the active RFID tag. The active RFID tag enters the working state after being triggered by the wake-up circuit, waiting to receive the radio frequency polling information sent by the second RFID reader ;

[0062] 3) When the first RFID reader receives the tag ID sent by the passive RFID tag, the geographic location information is obtained from the geolocation module as the boarding position information corresponding to the received tag ID, and the received tag ID is sent to the second RFID reader;

[0063] 4) The second RFID reader receives the tag ID sent by the first RFID reader, records the received tag ID in the tag list, and sends out radio frequency polling information with a polling period Tp=10s;

[0064] 5) The active RFID tag in the working state of the dual-core RFID travel card will send response information containing its stored tag ID to the second RFID reader when receiving the radio frequency polling information; if the active RFID tag is in If the RF polling information is not received within 30s of continuous Tout=30s, it will enter the dormant state and wait for the trigger by the wake-up circuit;

[0065] 6) The second RFID reader aligns the received response information with the tag ID recorded in the tag list according to the tag ID it contains, and judges whether there is a tag ID in the tag list and there is no response information; if the tag list is There are three consecutive times (this embodiment takes the upper limit of unanswered times K=3) tag IDs that have not been aligned and have response information, and the second RFID reader deletes the tag IDs that have not been aligned and have response information for three consecutive times from the tag list , And obtain geographic location information from the geolocation module every time a tag ID is deleted as the drop-off location information corresponding to the deleted tag ID;

[0066] 7) The data collection module counts the number of tag IDs in the tag list in real time as the real-time number of passengers on the bus, and obtains the boarding position information and the drop off location information corresponding to the tag ID from the first RFID reader and the second RFID reader in real time. Vehicle location information is used as the OD information of bus passengers;

[0067] 8) The wireless communication module obtains the real-time number of people on the bus and the OD information of the bus passengers in real time and releases it to the outside through the wireless communication module.

[0068] In this embodiment, in order to reduce the energy consumption of the active RFID tag in the dual-core RFID travel card, the working mode of the active RFID tag is also improved. The improved solution requires the cooperation of the second RFID reader in the vehicle information collection subsystem. The radio frequency polling information sent by the second RFID reader should include the polling period Tp of the radio frequency polling information and the tags in the tag list. ID and the sequence number of each tag ID in the tag list; in step 5) in the process of collecting bus passenger flow information, the active RFID tag in the dual-core RFID boarding card is receiving After the radio frequency polling information, obtain the polling period Tp and the sequence number N of the tag ID stored in the active RFID tag itself in the tag list from the radio frequency polling information, and calculate the response delay Tack as follows:

[0069] Tack=N·Tans;

[0070] Tans represents the polling response delay time; the active RFID tag sends the response information containing the stored tag ID to the second RFID reader at the time of delay Tack after receiving the radio frequency polling information, and then immediately enters the sleep state, and Re-enter the working state before the time delay Tp after receiving the radio frequency polling information, and wait to receive the radio frequency polling information from the second RFID reader; if the active RFID tag does not receive the radio frequency polling within the preset offline time limit Tout Information, it enters the dormant state, waiting to be triggered by the wake-up circuit.

[0071] Through this improved scheme, on the one hand, each dual-core RFID travel card in the bus can communicate with the second RFID reader at different times to avoid mutual signal interference; on the other hand, it can effectively reduce the dual-core RFID travel card. The time that the active RFID tag in the car card is in the working state helps to further reduce the power consumption of the active RFID tag and prolong the service life of the battery in the dual-core RFID car card. Among them, the range of the polling response delay time Tans is preferably between 5 and 100 milliseconds to ensure higher polling efficiency; of course, those skilled in the art can also adjust the polling response delay time Tans according to actual application needs. Value.

[0072] The foregoing embodiment only provides an implementation manner of the technical solution of the present invention as an example, but does not represent a limitation to the technical solution of the present invention. For example, in the vehicle information collection subsystem, the second RFID reader and the data collection module do not necessarily need to be integrated, and they can be set independently, or the data collection module can also be read with the first RFID reader in the vehicle information collection subsystem. At the same time, in the system, the system parameters such as the polling cycle Tp, the upper limit of unanswered times K, the offline time limit Tout, and the polling response delay time Tans can be set according to the needs of the actual application environment.