CN1588093A - Vehicle speed detection device - Google Patents

Abstract

The present invention discloses a vehicle speed detection device, which estimates the instantaneous vehicle speed of the vehicle by detecting the existing noise frequency of the vehicle power supply and the vehicle acceleration value measured by an accelerometer through interactive calculation. The vehicle speed detection device comprises a vehicle power supply noise detection unit for detecting the vehicle power supply noise frequency and an accelerometer for detecting the vehicle acceleration value. The estimated instantaneous vehicle speed is obtained through integral calculation, thereby enabling the vehicle navigation device to continue to perform navigation during the window period when the GPS signal is disconnected, and has the convenience of plug-and-play.

Description

Vehicle speed detection device

technical field

The invention relates to a vehicle speed detection device, in particular to a vehicle speed detection device for obtaining an estimated instantaneous vehicle speed by detecting the noise frequency of the vehicle power supply and the acceleration value of the vehicle.

Background technique

General car navigation devices use the signals transmitted by satellites all over the sky to obtain the longitude and latitude of the car after calculation, and then locate the position of the car on the electronic map on the car to guide the driver in real time; but It is known that car navigation devices often experience poor signal reception or disconnection due to terrain, features or road constructions, such as in tunnels, under viaducts, or in roadways with tall buildings on both sides of the city. The device cannot operate because the satellite signal cannot meet the positioning requirements; in order to solve this deficiency, some higher-level navigation devices 11 will use the detection of the gyroscope 12 and the speed line 13 to estimate the driving position of the vehicle (as shown in Figure 1 Show), to make up for the absence of the navigation device 11 being unable to locate when the satellite 14 signal disappears.

The position and signal format of the speed line 13 of different vehicles are different, which causes installation troubles, and ordinary users who purchase higher-level navigation devices cannot install them by themselves, and must pay an additional installation fee to ask a professional technician Come to install.

Contents of the invention

The purpose of the present invention is to provide a vehicle speed detection device, so that it can provide a vehicle speed signal in time for the continued execution of the car navigation when the car navigation encounters a GPS signal disconnection, and can further overcome the problem of the navigation system connecting the car. The installation of the speed signal is troublesome, so that the convenience of plug-and-play can be achieved without the installation of a professional professional.

The vehicle speed detection device of the present invention at least includes a vehicle power supply noise detection unit, utilizes the vehicle power supply noise detection unit to detect the frequency of the vehicle power supply noise, and obtains the estimated real-time vehicle speed through integral calculation, which is used for the car navigation device in the GPS signal Can continue to perform navigation when lost connection.

The vehicle speed detecting device of the present invention also includes an accelerometer, utilizes the vehicle power supply noise detection unit to detect the power supply noise frequency on the vehicle, and utilizes the accelerometer to detect the acceleration value of the vehicle, and obtains the estimated instant vehicle speed through integral calculation, It is used for the car navigation device to continue to perform navigation when the GPS signal is lost.

The vehicle speed detection device of the present invention can be plugged into the car cigarette lighter to obtain the noise frequency signal of the car power supply, and at the same time, its power supply is connected to the cigarette lighter to provide the vehicle speed detection device and the navigation device. Power supply for plug-and-play convenience.

The vehicle speed detection device of the present invention also includes a navigation device, so that the navigation device can be installed together with the present invention in order to facilitate the original installation of the navigation device.

The automobile power supply noise detection unit of the present invention is provided with a computing unit, and the computing unit can also be included in the navigation device.

The present invention can solve the installation problem that the known navigation system is not easy to connect to the speed signal of the car, so that the convenience of installation can be achieved through the plug-in of the cigarette lighter; at the same time, the car navigation device can be solved by the present invention The problem that it cannot be implemented during the GPS signal loss window period is used to improve the error of gyroscope positioning correction.

The above and other objects, effects and features of the present invention will become more clear through the following detailed description of preferred embodiments in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic block diagram of a traditional car navigation system;

Fig. 2 is a schematic diagram of a circuit block of the present invention;

Fig. 3 is a schematic circuit block diagram of another embodiment of the present invention;

Fig. 4 is the characteristic diagram of the relationship curve between engine speed and vehicle speed of the present invention;

Fig. 5 is the vehicle speed look-up table of file position and engine speed of the present invention;

Fig. 6 is an action flowchart of the present invention.

Explanation of reference signs: 11 navigation device; 12 gyroscope; 13 vehicle speed line; 14 satellite; 2, 2' vehicle speed detection device; 21, 21' automobile power supply noise detection unit; 212' first high-pass circuit; 213, 213' first amplifying circuit; 214, 214' window comparison circuit; 215, 215' second low-pass circuit; 216, 216' second high-pass circuit; 217, 217' second Amplifying circuit; 218, 218' privy circuit; 219, 41' computing unit; 22, 22' accelerometer; 3 cigarette lighter; 4, 4' navigation device; 42' navigation system; 5 satellites; G1, G2, G3 , G4, G5 fixed ratio; NF frequency; CS speed; ES engine speed; r parameter; Vt instant speed; a acceleration value; a0 set value; T time interval; T0 set time.

Detailed ways

Referring to the circuit block schematic diagram of the preferred embodiment of the present invention shown in Fig. 2, vehicle speed detection device 2 of the present invention comprises an automobile power supply noise detection unit 21 and an accelerometer 22, wherein:

The automobile power supply noise detection unit 21 is used to detect the existing noise frequency NF (noise frequency) of the automobile power supply, and convert it to the engine speed ES (engine speed), and then obtain an estimated instant vehicle speed;

The accelerometer 22 (accelerometer) is used to detect the acceleration value a of the car.

The automobile power supply noise detection unit 21 of the present invention includes:

The first low-pass circuit 211 is used to filter out the noise of the high frequency part in the noise frequency NF;

The first high-pass circuit 212 is used to filter out the noise of the low frequency part in the noise frequency NF;

The first amplifying circuit 213 amplifies the noise frequency NF signal for comparison;

Window comparator circuit 214, using the window comparator circuit to generate a digital waveform for the signal waveform part in the noise frequency NF;

The second low-pass circuit 215 filters out the noise of the high-frequency part of the signal in the noise frequency NF again;

The second high-pass circuit 216 filters out the noise of the low frequency part in the noise frequency NF again;

The second amplifying circuit 217 amplifies the noise frequency NF signal for comparison;

The Schmidt circuit 218 uses the Schmidt circuit to organize the waveform part of the noise frequency NF signal to generate a digital waveform;

The calculation unit 219 converts the detected noise frequency NF generated by the generator into a digital signal, adds the acceleration value a detected by the accelerometer, and calculates an estimated instant vehicle speed Vt after interactive calculation.

By the composition of the above components, the present invention is directly plugged into a car cigarette lighter 3, and the car power supply noise frequency NF signal is obtained through the cigarette lighter 3, and the cigarette lighter 3 also provides the required Power supply, so the convenience of installation and plugging can be achieved.

The present invention utilizes the automobile power supply noise detection unit 21 to detect the power supply noise frequency NF (noise frequency) on the vehicle, because the source of the noise may be caused by the ignition of the generator or the engine, and the rotation speed of the generator is related to the engine rotation speed ES are connected, so the noise frequency NF has the following relationship with the engine speed ES (engine speed):

ES=NFxr is that engine speed ES is the r times of noise frequency NF (r is a parameter value); Simultaneously in the present invention detects the relative relation of automobile engine speed ES and vehicle speed CS, we can classify following several situations (please See Figure 4):

1. When in neutral: only the engine is running, and the vehicle speed CS remains at zero.

2. When the car gear is in the first gear: the car speed CS will have a fixed ratio G1 relationship with the engine speed ES, that is, CS=ESxG1.

3. When the car gear is in the second gear: the car speed CS will have a fixed ratio G2 relationship with the engine speed ES, that is, CS=ESxG2.

4. When the car gear is in the third gear: the car speed CS will have a fixed ratio G3 relationship with the engine speed ES, that is, CS=ESxG3.

5. When the car gear is in the fourth gear: the car speed CS will have a fixed ratio G4 relationship with the engine speed ES, that is, CS=ESxG4.

6. When shifting gears: no matter from low gear to high gear or from high gear to low gear, the clutch will open or form a half-occlusion state at this time, the noise frequency NF will change suddenly, and the engine speed ES has no certain relationship with the vehicle speed CS. The car is usually in the state of accelerating or decelerating, and the change of the acceleration value a can be measured from the accelerometer 22 .

The above-mentioned relationship between the engine speed ES and the vehicle speed CS of the automobile, in addition to the state of stopping and shifting acceleration and deceleration, the engine speed ES and the vehicle speed CS will form several discontinuous proportional relationships (as shown in Figure 4), and these When the signal of the satellite 5 is good, the vehicle speed CS can be accurately measured by the navigation device 4, and the accelerometer 22 knows that the vehicle has no obvious acceleration and deceleration, and the relationship between the vehicle speed CS and the engine speed ES can be measured. The steps (as shown in Figure 6) are:

1. Detect power supply noise frequency: use the power supply noise detection unit 21 to detect the noise frequency NF and convert it into the engine speed ES.

2. Detecting the acceleration value: using the accelerometer 22 to detect the acceleration value a of the vehicle.

3. Gear position learning: When the GPS signal is received, the engine speed ES will have a speed difference when accelerating (suddenly drops sharply and then continues to rise, and the accelerometer 22 shows an acceleration state), and the caught speed at this time The GPS speed is the conversion point of the file position. After many times of learning and memorizing (the number of times can be set according to the demand, in principle, 5-6 times is suitable), these learning values can be used as an average to calculate An appropriate conversion point, and then when the obtained speed is higher or lower than this point, the judgment of the gear position can be made, and the comparison speed close to the actual value can be obtained.

4. Establish a vehicle speed look-up table: the relationship between the vehicle engine speed ES and the vehicle speed CS, except for the state of parking and shifting acceleration and deceleration, the engine speed ES and the vehicle speed CS form a constant proportional relationship, and these relationships can be found in When the satellite 5 signal is good, the vehicle speed CS is accurately measured, and when the accelerometer 22 measures the car without obvious acceleration and deceleration, the relationship between the vehicle speed CS and the engine speed ES is correctly measured, and then these discontinuous straight lines are calculated (as shown in Figure 4 shown), and establish a vehicle speed look-up table (such as shown in Figure 5) with an appropriate gear position, so that when the satellite 5 signal is lost, the engine speed ES can be converted from the noise frequency NF of the car power supply, and then look up the picture according to the vehicle speed The table is used as the basis for deriving the vehicle speed CS.

5. Determine whether it is effective to detect the vehicle speed according to the acceleration value a: the condition of using the vehicle speed reference table needs to be in the state of the clutch of the car, the condition of the vehicle speed reference table will be established, and the clutch state can be determined Determine according to the acceleration situation of the automobile, and the speed situation of the automobile can be estimated by the acceleration value a of the accelerometer 22, so when the reading value of the accelerometer 22 is less than the set value a0 (for example, below 15) set time T0 (for example 3 seconds), it can be judged that the vehicle has not accelerated significantly, the car will not shift gears, and the clutch has been firmly engaged, so the car noise frequency NF has a fixed relationship with the vehicle speed CS, which can be used as a vehicle speed look-up table to calculate the vehicle speed; otherwise, When the car does not meet the above conditions, we believe that the car power supply noise NF does not necessarily have an absolute relationship with the speed CS.

6. Estimate the real-time vehicle speed: after calculating the vehicle speed CS according to the vehicle speed table, the final confirmed vehicle speed is calculated by the sum of integrals obtained from the acceleration value a of the accelerometer 22 to calculate the real-time vehicle speed Vt, that is, Vt (instant vehicle speed)=Vt- 1 (estimated or confirmed vehicle speed at the previous point in time) + a (acceleration value) T (time interval) According to the above steps, it can be achieved when the satellite 5 signal is not good and the vehicle speed cannot be measured by the satellite 5 signal. An approximate instant vehicle speed Vt is estimated, and the navigation device 4 is provided for continued use.

7. Navigation execution:

(1) When the satellite reception signal is normal, the GPS signal obtained can be used to calculate the vehicle speed to provide navigation execution.

(2) When the satellite receiving signal loses connection, the instant vehicle speed Vt estimated by the present invention is used to provide navigation execution.

Referring to the circuit block schematic diagram of another embodiment of the present invention shown in Fig. 3, the vehicle speed detection device 2' of the present invention comprises a vehicle power supply noise detection unit 21' and an accelerometer 22', wherein in the vehicle power supply noise unit 21' The first low-pass circuit 211', the first high-pass circuit 212', the first amplifying circuit 213', the window comparison circuit 214', the second low-pass circuit 215', the second high-pass circuit 216', the second amplifying circuit 217 Components such as ', Schmidt circuit 218' are roughly the same as the embodiment of Fig. 2, the difference is that the calculation unit 41' is set in a navigation device 4', that is, the real-time calculated by the calculation unit 41' The vehicle speed Vt provides for the use of a navigation system 42'.

The above descriptions are only preferred embodiments of the present invention, and cannot limit the scope of the present invention. That is, all simple equivalent changes and modifications made according to the claims of the present invention and the content of the description should still belong to the patent of the present invention. scope of protection.

Claims (13)

1. A vehicle speed detection device, comprising a vehicle power supply noise detection unit, used to detect the existing noise frequency of the vehicle power supply, and convert it into engine speed, so as to obtain an estimated instant vehicle speed. 2. The vehicle speed detection device as claimed in claim 1, wherein the vehicle power supply noise detection unit includes a computing unit. 3. The vehicle speed detecting device according to claim 1, further comprising a navigation device. 4. The vehicle speed detection device according to claim 1, further comprising an accelerometer for detecting the acceleration value of the vehicle. 5. The vehicle speed detection device according to claim 1, wherein the power supply of the vehicle speed detection device is connected to the cigarette lighter to provide the power supply and the detection noise frequency of the vehicle power supply noise detection unit. 6. The vehicle speed detection device as claimed in claim 1, wherein the vehicle power supply noise detection unit comprises: The first low-pass circuit is used to filter out the noise in the high-frequency part of the noise frequency; The first high-pass circuit is used to filter out the noise of the low-frequency part in the noise frequency; The first amplifying circuit amplifies the noise frequency signal for comparison; The window comparator circuit uses the waveform part of the noise frequency signal to generate a digital waveform by using the window comparator circuit. 7. The vehicle speed detection device according to claim 6, wherein the vehicle power supply noise detection unit further comprises: The second low-pass circuit is used to filter out the noise of the high-frequency part in the noise frequency; The second high-pass circuit is used to filter out the noise of the low-frequency part in the noise frequency; The second amplifying circuit amplifies part of the noise frequency signal for comparison; The Schmidt circuit uses the Schmidt circuit to generate a digital waveform by using the waveform part of the noise frequency signal. 8. A vehicle speed detection device, including a vehicle power supply noise detection unit, used to detect the existing noise frequency of the vehicle power supply, and convert it into engine speed, so as to obtain an estimated real-time vehicle speed; and a navigation device. 9. The vehicle speed detection device as claimed in claim 8, wherein the navigation device is provided with a computing unit. 10. The vehicle speed detection device according to claim 8, further comprising an accelerometer for detecting the acceleration value of the vehicle. 11. The vehicle speed detection device as claimed in claim 8, wherein the power supply of the vehicle speed detection device is connected to the cigarette lighter to provide the vehicle power supply noise detection unit with power and detect the power supply noise frequency. 12. The vehicle speed detection device according to claim 8, wherein the vehicle power supply noise detection unit comprises: The first low-pass circuit is used to filter out the noise in the high-frequency part of the noise frequency; The first high-pass circuit is used to filter out the noise of the low-frequency part in the noise frequency; The first amplifying circuit amplifies part of the noise frequency signal for comparison; The window comparator circuit uses the waveform part of the noise frequency signal to generate a digital waveform by using the window comparator circuit. 13. The vehicle speed detection device according to claim 12, wherein the vehicle power supply noise detection unit further comprises: The second low-pass circuit is used to filter out the noise of the high-frequency part in the noise frequency; The second high-pass circuit is used to filter out the noise of the low-frequency part in the noise frequency; The second amplifying circuit amplifies the noise frequency signal for comparison; The Schmidt circuit uses the Schmidt circuit to generate a digital waveform by using the waveform part of the noise frequency signal.

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