CN201659856U - Automobile tire detection device based on CAN bus - Google Patents

Abstract

The utility model relates to an automobile tire detection device based on a CAN bus. The automobile tire detection device comprises a tire module and a TPMS node module, wherein the tire module is connected with the TPMS module via radio frequency signals, and a TPMS is used as a node of the CAN bus. The automobile tire detection device can monitor parameters of each automobile tire dynamically and transmit the dynamic parameters to an automobile cab instrument via the CAN bus, thereby realizing automobile tire fault early warning functions, real-time monitor to automobile tires, and then increasing stability and interference resistance of signal transmission.

Description

Automobile tire detecting device based on the CAN bus

Technical field

The utility model relates to the auto electric field, is specifically related to a kind of tyre detection device.

Background technology

Along with improving constantly of Freeway Development and automobile dynamic quality, blowing out and having become to threaten the No.1 killer of people's safety, a lot of people to talk " quick-fried " look especially becomes.According to the authoritative department statistics, on the express highway at home, the traffic accident that causes accounts for 70% of total number of accident by blowing out.In the U.S., this ratio is more up to 80%.Investigation statistics according to AIAE American institute of automobile engineers shows that there is more than 20 ten thousand traffic accidents every year in the U.S. owing to tire fault causes, and 75% tire fault is caused by low tyre or seepage.Therefore how to detect the thing that tire temperature, tire pressure have become people more and more to be concerned about in real time.The famous J.b.Power.and.Associates of research firm of the U.S. has announced the care degree of investigation customer to the automobile pioneering technology recently.By the investigation to 25 kinds of automobile pioneering technologys: the result shows that safety product has accounted for 9 in preceding 10 of care degree rank.And tire pressure telltale wherein makes number one.Most customers compare at safety air bag, safety strap and automobile tire pressure monitoring system, tend to the utilization of automobile tire pressure monitoring system more.

Automobile tire pressure monitoring system (TPMS) is exactly to arise at the historic moment under this demand.At western developed country, the tyre pressure sensor technology just begins development in the eighties, has arrived the nineties middle period, has been equipped with this class sensor in some European luxury cars.But the attention to the vehicle tire pressure problem is the latter stage that starts from the nineties, at that time, some car pools (RMA) of the U.S. to one 999 year car accedent study, finding wherein has 647 fatal accidents relevant with tire pressure.Simultaneously, another research (ATZ) just proves that also the damage of 85% tire is gradually to be lost by the insufficient pressure of tire or pressure to cause.Thus, the accident of blowing out of tire, cause a large amount of personal casualty, caused that United States Government shows great attention to, in November, 2000, United States Government formally issued federal transportation act-TREAD decree, and the lilliput car 50% equipment tire pressure monitoring system that sell in the new legislation regulation U.S. on the 1st market September in 2005 was by 2006, this ratio will be increased to 90%, then implements in full to 2007 September 1 end of the year.Though areas such as Japan, Europe do not have compulsory legal provisions, be demand with the safety performance that promotes automobile, some main motor planies have all begun to adopt successively this decree.

At present, the TPMS system of comparative maturity all has a style of one's own at home, is independent of other ECU on the automobile, is mainly used in other miniature car.The application at full size vehicle that increases along with the vehicle electronics kind with TPMS, the electronic control unit number increases, the wiring complexity strengthens, with traditional TPMS system acquisition pressure, the transducing signal of temperature, will be faced with long transmission distance, disturb big, emissive power is big and problem such as transmission signals instability.

Summary of the invention

For addressing the above problem, the technical scheme that the utility model is adopted is: a kind of automobile tire detecting device based on the CAN bus, comprise tire module and TPMS node module, adopt radiofrequency signal to be connected between described tire module and TPMS node module, described tire module comprises:

A sensor of gathering tire pressure, temperature signal,

A first processor that is used for the signal of code sensor collection,

A RF transmission circuit that is used to send the signal behind the first processor coding;

Described TPMS node module comprises

Second treater of the signal that RF acceptor circuit that is used to decode receives,

One with the total wire joint of CAN and realize second treater and CAN interface that the CAN bus signals transmits.

More preferably scheme of the present utility model is: described CAN interface comprises controller SJA1000, photoelectrical coupler 6N137 and CAN driving interface chip PCA82C250, and controller SJA1000 is connected with CAN driving interface chip through photoelectrical coupler 6N137.

Technical conceive of the present utility model is: the assembly that tire module comprises has first processor, RF transmission circuit, sensor.Sensor whenever detects once and wakes up the data process coding that sensor is arrived in first processor work after a while, and the signal that is modulated into 433.92MHz sends, and first processor is in dormant state to save battery electric quantity when not sending data.TPMS receiver module hardware comprises RF acceptor circuit, second treater, CAN interface.RF acceptor circuit received signal data, through second processor decodes, by CAN interface and the total wire joint of CAN, send data to automobile existing central alarm module by the CAN bus, the central alarm module links to each other by the data output end of data line with the CSRC processing module, show each tire pressure, temperature, voltage, realized the real-time monitoring of tire pressure.

Technical advantage of the present utility model is: by radio signal transmission and be connected into the existing CAN bus system of automotive system, improve communication stability, system reliability and monitoring efficient, save the space on automobile foreground, save each module overlapping development expense.

Description of drawings

Fig. 1 is the utility model overall work module diagram

Fig. 2 is the utility model tire module scheme drawing

Fig. 3 is the utility model TPMS node module scheme drawing

Fig. 4 is central early warning module connection diagram;

Fig. 5 is the main program flow chart of software;

Fig. 6 is experimental system figure;

The specific embodiment

With reference to Fig. 1, in order to satisfy the requirement of real-time, because that automobile electromagnetic disturbs is big, truck particularly, automotive components is many, and the signal transmission is subjected to disturb and shielding easily and complicated, and carries out information exchange with other vehicle electronics element is bad.New scheme adopts the CAN bus architecture, and TPMS is as a node of CAN bus.The parameter of each tire of dynamic monitoring automobile, and dynamical parameter by the CAN bus transfer on the automobile cab instrument, realize motor tire fault pre-alarming function.Frame of broken lines inside is respectively tire module, TPMS node and central early warning module.The frame of broken lines outside is other electronic control unit of automobile, and they all pass through the CAN bus and link to each other realization data sharing and information transmission.The TPMS node module is responsible for receiving the tire module take off data, is converted to the CAN message format, sends on the CAN bus.The CAN bus is many main websites bus, and each node all other nodes on network of active at any time sends information, is regardless of the principal and subordinate.Communication flexibly; Every frame effective word joint number is 8 at most on the CAN bus, and the transmission time is short, is subjected to probability of interference low, and CRC and other verification measures are arranged, and has fabulous error detection effect, and the data error rate is extremely low.The CAN bus has only two leads, when system expands, does not need any change of application layer and any node software and hardware, can directly new node be hung on the bus to get final product, so cabling is few, and system expands easily, and remodeling flexibly; The network struction cost is low, and total line use ratio is high.In order to improve to the differential transmittability of bus with to the differential receiving capability of CAN bus controller, expansion CAN interstitial content needs to increase CAN bus transceiver 82C250.The CANH of 82C250 links to each other with the CAN bus by one 5 ohmage separately with the CANL pin, plays certain metering function, and protection 82C250 avoids the impact of overcurrent.

With reference to Fig. 2, with reference to tire module figure, be that the particular hardware of system for monitoring pressure in tyre projector is implemented circuit diagram, based on the MAX1479 chip of the sensor SP30 of Infineon company, U.S. letter company.Sensor SP30 is an integrated SOC(system on a chip) module of semiconductor pressure sensor, semiconductor temperature sensor, digital signal processing unit and power supervisor.In order to strengthen the tire pressure monitoring function, also increased the ASIC digital signal processing unit of acceleration pick-up, voltage detecting, internal clocking, house dog and other function in the sensor SP30 module.The working environment of motor tire uniqueness has determined the tire pressure high request of the pressure sensor of monitoring in real time: higher precision and reliability in wide warm area, the wide power voltage range; The low-power consumption requirement; The stability requirement of harsh environment transmission of wireless signals.It is by pressure, temperature and the acceleration/accel of SP30 sensor acquisition tire, information after gathering is sent to first processor MAX1479 by MOD and DIN to be handled, the signal that MAX1479 will gather the joint reception carries out a series of processing, transmits the high frequency antenna transmitting terminal (RF transmission circuit) that fed network optimization coupling by port PAOUT high-frequency signal is launched.

With reference to Fig. 3, be TPMS node module connection diagram, the chip that wherein receives the RF acceptor circuit employing of the signal of launching is the MC33596 of Motorola Inc.; The signal processor that decoding RF acceptor circuit receives adopts the MC9S08DZ60 micro controller system.Receiver Module received RF signal data, MC33596 adopts manchester decoder, catches synchronous head by it, sets up synchronized clocke, then decoding and data handing.Experiment showed, with microcomputer series interface communication and compare that use this scheme to carry out RFDC, antijamming capability is strong, data transmission format is flexible.Can find from software codec that simultaneously if change the software delay time then can change the traffic rate of system, the designer can set up on their own according to the actual needs of data communication.By spi bus data are sent the signal after the demodulation to signal processor unit; Signal processor module is finished data handing by MC9S08DZ60.MC9S08DZ60 will arrive the information of finishing data handing and send the CAN bus to.The CAN bus mainly is made up of controller SJA 1000, photoelectrical coupler 6N137 and CAN driving interface chip PCA82C250.Send the data of handling to controller SJA 1000 earlier earlier, controller SJA1000 is connected with CAN driving interface chip through photoelectrical coupler 6N137.By the CAN bus, controller and actr are coupled together by serial data line.A node among the CAN can be monitored the signal that oneself sends.Therefore, the station that sends message can be observed bus level and survey the difference that sends the position and receive the position.The preparation ratio of CAN network is easier to, and allows directly to communicate between any station, handles and need not that all data all are aggregated into behind the upper computer row again.By the application of CAN bus, follow radio communication to compare and to improve communication stability, system reliability and monitoring efficient.

With reference to Fig. 4, be central early warning module connection diagram, central process unit uses S3C44BOX as main core, control some other part by it, wherein there is LCD to show, the data of handling can be shown that the FM7843 touch-screen is also arranged by LCD, can watch real-time data by touch-screen.Also by the SJA controller, connect the CAN bus by it, the data that receiver module receives are exactly to give central early warning module by the CAN bus transfer, and the jtag interface circuit is also arranged, and can debug download with program to hardware by it.As vehicle electronics product, preferably also do the function that an audio frequency is play at interface.Will expand it in addition, its memory device has been selected HY57V641620DRAM for use, and it is the most common Installed System Memory of dynamic RAM, and DRAM can only keep the very short time with data.In order to keep data, DRAM uses capacitance stores, so must refresh once AM29LV160BNOR-FLSAH and K9F208U0CN AND-FLA SH every a period of time, the FLASH flash memory is a nonvolatile memory, can carry out erasable and programming again to the memory cell block that is called piece.The write operation of any FLASH device can only be carried out in sky or the unit of having wiped, so in most cases, must carry out earlier before carrying out write operation and wipe.It is foolproof that the NAND device is carried out erase operation, and NOR then requires positions all in the object block all to be written as 0 earlier before wiping.NOR and AND are two kinds of main nonvolatile flash memory technology on the present market.

With reference to Fig. 5, be software single-piece main program flow; The native system The software at present popular embedded real-time multitask open operating system Linux.In order to realize that the TPMS radiofrequency signal well communicates by letter with the CAN bus, adopt the mode of interrupting to accept the data of CAN bus.On the basis of the demand analysis of system, tire pressure intelligent monitor system software is done the summary design.Mainly solved the programming problem of realizing these system requirements, comprised Manchester code demodulation, data monitoring, control setting, warning supervisor module.

The software integral structure is the realization flow of system software as shown in Figure 5.Comprise the steps:

(1) dynamical parameter and initialization fieldbus nodes such as the pressure of read sensor transmission, temperature;

(2) wait for the radiofrequency signal that receives, judge whether to produce and interrupt, obtain the CAN network information, and to the CAN network organizing;

(3) read the node of CAN bus, and wait for interruption;

(4) the chip MC33696 of initialization Motorola Inc., and self check is ready.If the ready acceptance/reception SPI Frame that waits pending data is represented in the LED flicker; The there is carried out the self check of data again if the initialization judgement, is returned in self check more not by just judging the state of LED.

(5) integrity of carrying out data is again judged, at first judges synchronous head.

(6) judge once more whether the ID of tire is correct, and carry out effect.

(7) repeating step (3), (4), (5), (6), the continuous on-cycle operation of program.

In order to verify the feasibility of system for monitoring pressure in tyre, make up experimental system as shown in Figure 6: by the function signal generator of the German BOSCH company that samples,, accept as carrier signal with high-frequency signal, observe the waveform signal that receives with U.S. Imtech oscp again by receiver.To the bandwidth of the complete machine of automobile tire pressure monitoring system and the sensitivity test and the overall bandwidth test of receiver.System's operation is normal, can guarantee integraty of the present invention, operability, practicality and applicability, the test that institute's development product is carried out signal stabilization and detected real-time of bandwidth should can observe complete machine to to(for) the designer of product is a narrow band signal, the sensitivity of receiver is fine, has verified that fully the TPMS system design based on the CAN bus has good communication stability and feasibility.

Though the utility model is done description according to the above embodiments, every technical personnel notice, the invention thought of basic utility model is not limited in the utility model, based on any variation of this invention thought and be escape this patent protection domain.

Claims (2)

1. automobile tire detecting device based on the CAN bus is characterized in that: comprise tire module and TPMS node module, adopt radiofrequency signal to be connected between described tire module and TPMS node module, described tire module comprises:

A sensor of gathering tire pressure, temperature signal,

A first processor that is used for the signal of code sensor collection,

A RF transmission circuit that is used to send the signal behind the first processor coding;

Described TPMS node module comprises

A RF acceptor circuit that is used to receive the signal of described RF transmission circuit emission;

Second treater of the signal that RF acceptor circuit that is used to decode receives,

One with the total wire joint of CAN and realize second treater and CAN interface that the CAN bus signals transmits.

2. the automobile tire detecting device based on the CAN bus according to claim 1, it is characterized in that: described CAN interface comprises controller SJA 1000, photoelectrical coupler 6N137 and CAN driving interface chip PCA82C250, and controller SJA1000 is connected with CAN driving interface chip through photoelectrical coupler 6N137.

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