Novel capacitance reading circuit for controlling triggering of automobile safety air bag

Abstract

The invention relates to the technical field of capacitance measurement, in particular to a novel capacitance reading circuit for controlling triggering of an automobile safety air bag. The novel capacitance reading circuit comprises an acquisition module, a core controller, a signal processing module and an accident processing module. A core controller outputs a 0-degree sinusoidal signal and a 90-degree sinusoidal signal with different phases, the 0-degree signal is input to an acquisition module, and the acquired signal is processed; wherein the 90-degree signal generates a square wave signal with the amplitude of + / -5V through the comparator for controlling the switching-on and switching-off of the analog switch, the demodulated output signal passes through the second-order low-pass filter to obtain stable direct current which is input into the AD conversion module of the core controller, and finally, the core controller judges whether the vehicle has an accident or not. If an accident occurs, the accident is recorded in the SD card module while alarm processing is carried out and the safety air bag is popped up; the method has the advantages of accurate measurement effect and high accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of capacitance measurement, in particular to a novel capacitance readout circuit for controlling the triggering of an automobile safety airbag. Background Art

[0002] With the continuous development of social economy, people's requirements for life are getting higher and higher, and cars have become a necessity for almost every family. However, in recent years, the number of people who died in accidents while driving has been increasing year by year, and the situation that the car airbag cannot be safely deployed when an accident occurs accounts for a large proportion. Therefore, it is very important to have a device that can accurately sense the arrival of an accident and automatically deploy the airbag immediately.

[0003] At present, the commonly used airbag triggering methods include electromechanical collision sensors and piezoresistive collision sensors. Electromechanical collision sensors have poor stability and are prone to ejecting airbags when not necessary; piezoresistive sensors are easily affected by external temperature and are prone to large errors in measurement results, leading to misjudgment.

[0004] Based on this, the present invention provides a novel capacitance readout circuit for controlling the triggering of automobile airbags to solve the above-mentioned technical problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a novel capacitance readout circuit for controlling the triggering of automobile airbags, which has a more precise measurement effect and a higher accuracy.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a novel capacitance readout circuit for controlling the triggering of an automobile airbag, the novel capacitance readout circuit comprising an acquisition module, a core controller, a signal processing module and an accident processing module, wherein:

[0008] The acquisition module is used to complete the acquisition of external signals, and the acquisition module includes an adjustable capacitance acquisition sensor Cx and a leakage resistor Gx;

[0009] The core controller is used to realize the timing control of the acquisition module;

[0010] The signal processing module is used to complete the amplification, flipping and selection of the collected signal, and the signal processing module includes a capacitor-voltage converter A1, an inverter A2, a comparator A3, a selection switch A4 and a filter A5;

[0011] The capacitance-to-voltage converter A1 is used to perform capacitance-to-voltage conversion processing on the signal collected by the adjustable capacitance collection sensor Cx;

[0012] The inverter A2 is used to perform a reverse operation on the amplified signal to provide an output signal for subsequent selection;

[0013] The comparator A3 is used to compare the 90° phase sine wave with the high level, and generate a square wave signal with an amplitude of ±5V to control the closing of the analog switch and perform switch demodulation;

[0014] The selection switch A4 is used to select the signal amplified by the capacitor-to-voltage converter A1 and the signal inverted by the inverter A2;

[0015] The filter A5 is used to convert the AC signal outputted at last into a relatively stable DC signal;

[0016] The accident handling module is used for response processing after an accident occurs, and the accident handling module includes an airbag trigger, a parking device, an alarm and an SD card storage module;

[0017] The SD card module is used to record various parts when an accident occurs for subsequent processing.

[0018] The present invention is further configured as follows: the core controller outputs sinusoidal signals with different phases of 0° and 90° respectively through the DAC module therein; the 0° phase sinusoidal wave is used to be input into the adjustable capacitance acquisition sensor Cx for collecting external signals; the 90° phase sinusoidal wave is used to be output to the comparator A3, and a square wave signal with an amplitude of ±5V is generated by the comparator A3, which is used to simulate the closing of the switch and perform switch demodulation.

[0019] The present invention is further configured as follows: the output end of the adjustable capacitance acquisition sensor Cx in the acquisition module is connected to the capacitance-to-voltage converter A1, which is used to convert and amplify the capacitance-to-voltage acquisition signal of the acquisition capacitance sensor Cx, and divide the converted signal into two paths, L1 and L2, L1 is directly input to the input end of the selection switch A4, and L2 is input to the inverter A2 for inversion and then input to the input end of the selection switch A4; the leakage resistor Gx is used to eliminate errors in the circuit.

[0020] The present invention is further configured as follows: the output signal of the comparator A3 in the signal processing module is input to the selection section of the selection switch to select the signal of the input end L1, L2.

[0021] The present invention is further configured as follows: the filter A5 in the signal processing module performs a filtering operation on the signal output by the selection switch A4 to filter out the high-frequency components in the signal, and finally obtains a DC signal V ADC .

[0022] The second aspect of the present invention is to provide a novel capacitance readout circuit detection method for controlling the triggering of an automobile airbag, comprising the following steps:

[0023] S1. Turn on the core controller, initialize it, and output 0° and 90° sinusoidal signals;

[0024] When the output phase angle is 0°, the output signal is:

[0025] When the output phase angle is 90°, the output signal is:

[0026] Among them, V m is the amplitude of the excitation signal;

[0027] S2. After completing step S1, by changing the capacitance of the adjustable capacitance acquisition sensor Cx, the circuit error is processed by the leakage resistor to obtain:

[0028] i1=G x sinwt+C x wcoswt

[0029] And the capacitance voltage conversion is performed through C / V converter A1:

[0030]

[0031] S3. After completing step S2, the output V2(t) is divided into two paths, one of which is input to the input end of the selection switch through L1, and the other is reversed through inverter A2:

[0032] V3(t)=-V2(t)

[0033] Substituting V2(t) into the formula, we get:

[0034]

[0035] And input the signal into L2;

[0036] S4, the input V2(t) and V3(t) are used as the input of the analog switch for adjustment, wherein the control signal of the analog switch demodulation is passed through the comparator A3 by the orthogonal phase shift unit, and the orthogonal phase shift unit performs a 90° phase shift operation on the excitation signal, and generates a square wave signal with an amplitude of ±5V through the comparator, wherein the maximum value of the square wave is 5V and the minimum value is -5V. The newly generated square wave is used to control the closing of the analog switch for switch demodulation. When the output square wave is 5V, the analog switch allows the output of V3(t), otherwise, the analog switch allows the output of V2(t);

[0037] After completing S1, S2, S3, and S4, analog switch A4 selects the output, which is:

[0038]

[0039] S5: V4(t) can filter out the high-frequency components of the signal through a second-order low-pass filter, and the output signal V ADC It can be expressed as follows:

[0040]

[0041] Considering that the signal output by the orthogonal phase shift unit is the excitation signal phase shifted by 90°, we can substitute =90 into the above formula to get the new V ADC Output expression:

[0042]

[0043] Assumptions In the expression for k, V m and f are the amplitude and frequency of the excitation signal, R1 and C3 are fixed resistance and capacitance, so k is a fixed constant. Substituting k in the above formula, we get:

[0044] V ADC =kC x ;

[0045] In the above formula, k is a constant, so the detected capacitance value is linearly related to the output voltage.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] In the present invention, the core controller outputs two sinusoidal signals of different phases, 0° and 90°, wherein the 0° signal is input to the acquisition module to process the acquired signal; wherein the 90° signal generates a square wave signal with an amplitude of ±5V through a comparator to control the closing of an analog switch, and performs switch demodulation. The demodulated output signal passes through a second-order low-pass filter to obtain a stable direct current input to the AD conversion module of the core controller, and finally the core controller determines whether an accident occurs to the vehicle. If an accident occurs, the accident is recorded in the SD card module while performing alarm processing and popping out the airbag; the present invention has a more precise measurement effect and a higher accuracy rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The schematic diagram of the novel capacitance readout circuit for controlling the triggering of the automobile safety airbag according to the present invention.

[0049] Figure 2The present invention is a circuit diagram of a novel capacitance readout circuit for controlling the triggering of an automobile safety airbag.

[0050] Description of the numbers in the figure:

[0051] 1. Core controller; 2. Power module; 3. Acquisition module; 4. Signal processing module; 5. Accident handling module. DETAILED DESCRIPTION

[0052] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Example:

[0054] This embodiment provides a novel capacitance readout circuit for controlling the triggering of an automobile airbag, as follows:

[0055] like Figure 1 As shown, the novel capacitance readout circuit includes a core controller 1, a power module 2, a collection module 3, a signal processing module 4 and an accident processing module 5;

[0056] The signal processing module 4 includes a capacitor-to-voltage converter A1, an inverter A2, a comparator A3, a selection switch A4 and a filter A5;

[0057] The acquisition module 3 is used to collect the change value of the external capacitance, one end of which is connected to the 0° phase output end of the core controller 1 as the input signal, and the other end is connected to the capacitance-voltage converter of the signal processing module 4 for signal processing;

[0058] The core controller 1 is used to output signals with a phase difference of 0° and 90°, which are respectively input into the acquisition capacitor Cx of the acquisition module 3 and the comparator A3 of the signal processing module 4, for capacitor acquisition and controlling the closing of the analog switch;

[0059] The power module 2 is used to supply power to each module; the power module 2 is powered by a 12V lithium battery, and uses a TPS5430DDAR chip to output a 5V digital voltage for the main control module 1 and the signal processing module 4, and the 12V voltage is directly supplied to the accident processing module 5;

[0060] The accident handling module 5 includes an airbag trigger, a parking brake, an alarm and an SD card storage module;

[0061] The airbag trigger, parking device and alarm are used to eject the airbag, park the vehicle and give an alarm when receiving a signal from the main control module 1;

[0062] The SD card storage module is used to store accident information in the SD card for subsequent accident processing;

[0063] The core controller 1 is used to output a sinusoidal signal with a phase angle of 0° to the acquisition module 3 for collecting the external capacitance change value, and output a sinusoidal signal with a phase angle of 90° to the comparator A3 of the signal processing module 4 for generating a ±5V square wave signal to control the closing of the analog switch, which is used for the selection input end of the selection switch A4 in the signal processing module 4; it is also connected to the AD conversion end of the signal processing module 4, and determines whether to pop out the airbag by reading the output value of the final signal;

[0064] like Figure 2 As shown, the signal processing module 4 includes a capacitance-to-voltage converter A1, which is used to convert the capacitance value in the acquisition module 3 into a voltage value and input it to the input end of the selection switch A4; an inverter A2, which is used to reversely convert the voltage converted by A1 and input it to the other input end of the selection switch A4; the comparator A3 inputs a sinusoidal signal with a phase angle of 90° output by the core controller 1 to its reverse input end to simulate the closing of the switch and perform switch demodulation; the selection switch A4 selects and outputs the signal by judging the signal input to the selection end of the comparator A3; the filter A5 obtains a DC signal by filtering the output signal twice, and finally inputs it to the AD conversion part in the core controller 1;

[0065] Among them, the core controller 1 is used to generate a sinusoidal excitation signal , the starting state

[0066] At this time, the acquisition module 3 performs acquisition, the acquisition capacitance value is Cx, the leakage resistance value is Gx, and after the acquisition of the external capacitance signal by Cx and the processing of Gx, the following is obtained:

[0067] i1=G x sin wt+C x wcos wt

[0068] The output signal V2(t) obtained by capacitor voltage conversion is:

[0069]

[0070] After outputting V2(t), the signal is inverted by inverter A2 to obtain V3(t):

[0071] V3(t)=-V2(t)

[0072] Substituting into V2(t) we get:

[0073]

[0074] At this time, the input V2(t) and V3(t) are used as the input of the analog switch for demodulation, where the control signal of the analog switch demodulation is transmitted by the orthogonal phase shift unit through the comparator A3. The orthogonal phase shift unit performs a 90° phase shift operation on the excitation signal, and generates a square wave signal with an amplitude of ±5V through the comparator A3, where the maximum value of the square wave is 5V and the minimum value is -5V. The newly generated square wave is used to control the closing of the analog switch for switch demodulation. When the output square wave is 5V, the analog switch allows the output of V3(t), otherwise, the analog switch allows the output of V2(t);

[0075] At this time, the output voltage of the analog switch is:

[0076]

[0077] At this time, V4(t) is filtered by a second-order low-pass filter (i.e., filter A5) to obtain a DC signal V ADC :

[0078]

[0079] It is known that the signal output by the orthogonal phase shift unit is the excitation signal phase shifted by 90°, so Substituting into the above formula, we can get the new V ADC Output expression:

[0080]

[0081] Assumptions In the expression for k, V m and f are the amplitude and frequency of the excitation signal, R1 and C3 are fixed resistors and capacitors, so k is a fixed constant. Substituting k in the above formula, we get:

[0082] V ADC =kC x

[0083] In the above formula, k is a constant, so the detected capacitance value is linearly related to the output voltage;

[0084] In the present invention, the core controller 1 generates two different sinusoidal excitation signals with phase angles of 0° and 90°, wherein 0° is input to the signal acquisition module 3 to acquire the external capacitance value; 90° is input to the reverse input end of the comparator A3 to form an analog clock input to the selection end of the selection switch A4; the acquisition module 3 acquires the external capacitance value, outputs a stable and clear voltage signal through capacitance voltage conversion, outputs a stable DC signal through the selection switch A4 and the filter A5 in the middle, and finally inputs it to the core controller 1 for AD conversion, and finally draws the conclusion: the detection capacitance Cx and the final output voltage V ADC呈线性关系 . Through the core controller 1 to V ADC The reading determines whether the vehicle has an accident. If an accident occurs, the airbag will be deployed and the alarm will be processed. At the same time, the accident information will be recorded on the SD card storage module for subsequent processing.

[0085] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0086] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A novel capacitance readout circuit for controlling the triggering of automobile airbags, characterized in that: The novel capacitance readout circuit comprises an acquisition module, a core controller, a signal processing module and an accident processing module, wherein: The acquisition module is used to complete the acquisition of external signals, and the acquisition module includes an adjustable capacitance acquisition sensor Cx and a leakage resistor Gx; The core controller is used to realize the timing control of the acquisition module; The signal processing module is used to complete the amplification, flipping and selection of the collected signal, and the signal processing module includes a capacitor-voltage converter A1, an inverter A2, a comparator A3, a selection switch A4 and a filter A5; The capacitance-to-voltage converter A1 is used to perform capacitance-to-voltage conversion processing on the signal collected by the adjustable capacitance collection sensor Cx; The inverter A2 is used to perform a reverse operation on the amplified signal to provide an output signal for subsequent selection; The comparator A3 is used to compare the 90° phase sine wave with the high level, and generate a square wave signal with an amplitude of ±5V to control the closing of the analog switch and perform switch demodulation; The selection switch A4 is used to select the signal amplified by the capacitor-to-voltage converter A1 and the signal inverted by the inverter A2; The filter A5 is used to convert the AC signal outputted at last into a relatively stable DC signal; The accident handling module is used for response processing after an accident occurs, and the accident handling module includes an airbag trigger, a parking device, an alarm and an SD card storage module; The SD card module is used to record various parts when an accident occurs for subsequent processing.

2. A novel capacitance readout circuit for controlling the triggering of an automobile airbag according to claim 1, characterized in that: The core controller outputs sinusoidal signals with different phases of 0° and 90° respectively through the DAC module therein. The 0° phase sinusoidal wave is used to input into the adjustable capacitance acquisition sensor Cx for collecting external signals; the 90° phase sinusoidal wave is used to output to the comparator A3, and a square wave signal with an amplitude of ±5V is generated by the comparator A3, which is used to simulate the closing of the switch and perform switch demodulation.

3. A novel capacitance readout circuit for controlling the triggering of an automobile airbag according to claim 1, characterized in that: The output end of the adjustable capacitance acquisition sensor Cx in the acquisition module is connected to the capacitance-to-voltage converter A1, which is used to convert and amplify the capacitance-to-voltage acquisition signal of the acquisition capacitance sensor Cx, and divide the converted signal into two paths, L1 and L2. L1 is directly input to the input end of the selection switch A4, and L2 is input to the inverter A2 for inversion and then input to the input end of the selection switch A4; the leakage resistor Gx is used to eliminate errors in the circuit.

4. A novel capacitance readout circuit for controlling the triggering of an automobile airbag according to claim 1, characterized in that: The output signal of the comparator A3 in the signal processing module is input to the selection section of the selection switch to select the signals of the input terminals L1 and L2.

5. A novel capacitance readout circuit for controlling the triggering of an automobile airbag according to claim 1, characterized in that: The filter A5 in the signal processing module performs a filtering operation on the signal output by the selection switch A4 to filter out the high-frequency components in the signal and finally obtain a DC signal V ADC .

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