CN201352107Y - Air suspension bus body height detecting system - Google Patents

Abstract

The utility model discloses a body height detection system of an air suspension passenger car. A height sensor is installed between the frame and the axle. The height sensor is fixed at one end of a swing rod, and the other end of the swing rod is movably connected with a connecting rod. The other end of the connecting rod is fixed on the axle; the height sensor includes a coil and an iron core that can move up and down in the coil, and the coil is connected with the detection circuit. The utility model realizes the height measurement by making the iron core in the sensor frequently move in the coil to change the inductance value through the angle of the pendulum rod. The analog switch is controlled by the single-chip microcomputer to charge and discharge the inductance of the height sensor, and the single-chip microcomputer captures the signal to obtain the sensor's value. The output value can instantly compensate for temperature drift, provide accurate height information, and fully meet the requirements for vehicle height detection.

Description

An Air Suspension Bus Body Height Detection System

technical field

The utility model relates to a body height detection system of an air suspension passenger car, more specifically a system capable of compensating temperature drift and accurately measuring the variation value of the body height.

Background technique

Vehicle height is one of the most important information in the air suspension control system. During the control process of an air suspension bus, it is necessary to detect the height of the vehicle body in real time, the inflation and deflation of the air spring, and the height switching, etc., all of which need to be based on accurate vehicle height information, but the driving environment of the vehicle is complex, especially the change of the ambient temperature. Changes in the parameters of the electronic components of the hardware circuit will lead to an increase in the error of height detection. These factors will cause the suspension control to deviate from the ideal state, which is not conducive to the control of the air suspension bus. At present, the temperature sensor is mainly used to compensate the deviation of the output signal by software, which increases the manufacturing cost of the controller, and the temperature change of the hardness circuit itself cannot be effectively compensated.

Contents of the invention

In view of the deficiencies in the above detection, the utility model provides a height detection system for an electronically controlled air suspension system, which can compensate temperature drift and provide accurate height information for the air suspension controller.

In order to achieve the above object, the utility model adopts the following technical scheme: a height sensor is installed between the vehicle frame and the axle, the height sensor is fixed on one end of the swing rod, the other end of the swing rod is movably connected with the connecting rod, and the connecting rod The other end is fixed on the axle; the height sensor includes a coil and an iron core that can move up and down in the coil, and the coil is connected to the detection circuit.

The detection circuit includes connecting the coil and the freewheeling diode D1 in parallel to the inverting terminal of the operational amplifier IC2, a resistor R3 is connected between the inverting terminal of the operational amplifier IC2 and its output terminal, and the output terminal of the operational amplifier IC2 is connected through a resistor R6 ^* To the inverting terminal of the operational amplifier IC3, the input terminal of the operational amplifier IC3 is connected to a resistor R5 ^* between the input terminal of the operational amplifier IC3 and the power supply Vcc, its output terminal is connected to the base of the transistor Q1, the collector is connected to the power supply Vcc1 through the resistor R8, and its emitter is connected to Pin 2 of the photocoupler IC4; pin 6 of the output end of the photocoupler IC4 is connected to pin 5 of the Schmitt trigger IC5, and pin 6 of the Schmitt trigger IC5 outputs a height signal; resistors R1 and R2 are connected in series with the capacitor After C1 is connected in parallel, it is connected between the power supply Vcc and the ground to form a given circuit, and after voltage division, it is connected to the 13-pin of the analog switch IC1, the 11-pin of the analog switch IC1 is connected to the microcontroller, and the 3-pin of the output terminal of the analog switch IC1 is connected to the operational amplifier IC2. Non-inverting terminal.

In the utility model, when the height of the vehicle body changes, the iron core in the sensor moves frequently in the coil through the rotation angle of the swing rod, thereby changing the inductance value to realize height measurement. The analog switch IC1 is controlled by the single-chip microcomputer to charge and discharge the inductance L of the height sensor. At the same time, the single-chip microcomputer needs to capture the signal to obtain the output value of the sensor. The resistors R5 ^* and R6 ^* of the utility model are resistors to be adjusted, and R3 selects a carbon film resistor with a negative temperature coefficient, so that in the circuit design and debugging process, the difference between the resistors R5 ^* and R6 ^* can be adjusted according to the actual situation to compensate for the temperature Drift, so as to ensure the accuracy of vehicle height measurement. Under the condition of 28°C, the fluctuation range of the height signal is 0.3μs, and the error is less than 1%. However, when the ambient temperature rises from 28°C to 80°C, the fluctuation range of the height signal is 1.5μs, and the error is less than 5%. It can instantly compensate for temperature drift, provide accurate height information, and fully meet the requirements for vehicle height detection.

Description of drawings

Fig. 1 is the connection schematic diagram of the present utility model;

Fig. 2 is a working principle diagram of the height sensor 5 of Fig. 1;

FIG. 3 is a hardware circuit connection diagram of the vehicle height detection circuit 8 in FIG. 1 .

Detailed ways

Figure 1 is a schematic diagram of the positions of the air suspension passenger car frame 1, the axle 4 and the height sensor 5, that is, the vehicle height detection is to obtain the relative displacement change between the frame 1 and the axle 4, and the principle of the inductive height sensor 5 is shown in Figure 2 Shown, it comprises a coil 7 and an iron core 6 that can move up and down in the coil 7. The height sensor 5 is fixed on one end of the swing rod 2, the other end of the swing rod 2 is flexibly connected to one end of the connecting rod 3, and the other end of the connecting rod 3 is fixed on the axle 4; the coil 7 in the height sensor 5 is connected to the detection circuit 8. Its working principle is that when the height of the vehicle body changes, the iron core 6 in the sensor moves frequently in the coil 7 through the rotation angle of the pendulum 2, thereby changing the inductance value to realize height measurement. The hardware circuit is combined with the controller to detect the time constant of the inductive sensor to obtain the vehicle height value. Resistors R1 and R2 are connected in series with the protective capacitor C1 in parallel and then connected between the power supply Vcc and the ground to form a given circuit. After voltage division, they are connected to pin 13 of the analog switch IC1, in which the microcontroller and pin 11 of the analog switch IC1 Connection control, its output terminal 3 pins are connected to the non-inverting terminal of the operational amplifier IC2, while the coil 7 of the height sensor 5 (the dotted line frame part in Fig. 3) and the freewheeling diode D1 are connected in parallel to the inverting terminal of the operational amplifier IC2, and the operational amplifier IC2 Resistor R3 is connected between the inverting terminal of the operational amplifier IC2 and its output terminal, and the output terminal of the operational amplifier IC2 is connected to the inverting terminal of the operational amplifier IC3 through a resistor R6 ^* , and a resistor R5 ^* is connected between the input terminal of the operational amplifier IC3 and the power supply Vcc, which The output terminal is connected to the base of the triode Q1, the collector is connected to the power supply Vcc1 through the resistor R8, and its emitter is connected to pin 2 of the optocoupler IC4, and pin 6 of the output terminal of the optocoupler IC4 is connected to pin 5 of the Schmitt trigger IC5. The pin 6 of the Schmitt trigger IC5 outputs the height signal. Its working principle is to charge and discharge the coil inductance L of the height sensor 5 by controlling the analog switch IC1 through the single-chip microcomputer. At the same time, the single-chip microcomputer needs to capture the signal to obtain the output value of the sensor. The detection circuit here is a part of the air suspension controller.

Example

The control unit of the hardware circuit design of the vehicle body height detection system of the utility model is a measurement and control system composed of an 8-bit single-chip microcomputer as the core.

As shown in Fig. 3, in the vehicle body height detection circuit 8, all operational amplifiers are powered by plus or minus 9V power supply, converted from 24V bus power supply. The 5V standard power supply VCC is divided by resistors R1 and R2. in,

R1: 3.3kΩ R2: 680Ω R3: 1kΩ R4: 120Ω R5 ^* : 10kΩ

R6 ^* : 0Ω R7: 22kΩ R8: 1.3kΩ R9: 10kΩ R10: 10kΩ

C1: 0.1μF C2: 0.1μF

Vcc: 5V Vcc1: 9V Vcc2: 3V V ₊ : +9V _V- : -9V

IC1: CD4051 IC2: TL082 IC3: TL082 IC4: 6N137 IC5: 40106

Q1: 9031 D1: 1N5024

The following specifically introduces the working process of the vehicle body height detection system: the single-chip microcomputer controls the on-off of the analog switch IC1, the height sensor 5 is connected with the inverting terminal of the operational amplifier IC2, the CONTROL terminal is directly connected with the I/O port of the single-chip microcomputer, and the OUTPUT terminal is connected with the single-chip microcomputer The port of the time base module is connected, and the port is set to input falling edge capture mode. The working process of the circuit is as follows: In the initial state, the CONTROL terminal is at a high level, and the pin 3 of the analog switch IC1 is connected to the ground at pin 14. At this time, the inductor is not charged, and the output of the operational amplifier IC2 is close to 0V, so the output of the comparator IC3 is close to When the high-level signal of 9V, the triode Q1 conducts, the input terminal 2 of the photocoupler IC4 flows a current of about 6mA. It can be seen from the circuit that the output terminal 6 of the photocoupler IC4 is a low-level signal, Schmidt Flip-flop IC5 outputs a high-level signal of 3V. The optocoupler IC4 and Schmitt trigger IC5 at the output end complete signal conditioning and level conversion. The single-chip microcomputer sends low level at the CONTROL end, the analog switch IC1 pin 3 and pin 13 are connected, the single-chip microcomputer captures the falling edge signal of the OUTPUT port and starts timing. The voltage signal starts to charge the inductor, and the inductor current starts to rise. When the reverse terminal of IC3 is greater than 5V, the output terminal of comparator IC3 is at low level, the transistor Q1 is cut off, and the current at pin 2 of the input terminal of photocoupler IC4 is basically zero. , so that pin 6 of the output terminal of IC4 is a high level signal, and pin 6 of the output terminal of Schmitt trigger IC5 is a low level signal. At this time, the single-chip microcomputer captures the falling edge of the signal at the OUTPUT end, and the single-chip microcomputer timing ends, thus calculating the charging time of the inductor. At the same time, a high-level signal is sent to the input end to make the inductor continue to flow through the freewheeling diode D1, and prepare for the next measurement height. Adjust the size difference of resistors R5 and R6 in the circuit to compensate for temperature drift; at the same time, the internal resistance R4 of the sensor (the copper wire resistance containing the inductance coil) is actually measured as a negative temperature coefficient, so R3 also uses a carbon film resistor with a negative temperature coefficient to compensate for temperature. Variety.

The main part of the detection circuit 8 can be understood as an RL series circuit under step signal excitation (the height sensor can be equivalent to an RL series circuit), then the relationship between the inductor current and the charging time is

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; t</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}}<span\; class="notranslate">\; )</span>$

Among them, I _S is the inductor current tending to infinity, and τ is the charging time constant. Since the inductor current rises most sharply when t<τ, the voltage rises the fastest. If compared with the standard voltage, the voltage comparator IC3 outputs a steep falling edge, and the error generated is the smallest. Therefore, when designing the circuit, it is most appropriate to keep the charging time of the inductor within a τ. The height sensor 5 inductance value that selects among the present invention is between 8-35mH, according to τ=L/R, therefore τ is between 67 μ s-292 μ s, and the single-chip microcomputer clock cycle is set to 0.18 μ s, and the count value n of such single-chip microcomputer is 372 Between -1622, if the value of n is large enough, the accuracy of the single-chip microcomputer to measure the charging time can be improved. Therefore, while the charging time t should be less than τ, it should be as close to τ as possible, so that t is slightly smaller than τ.

The above detection circuit 8 is used to detect the height sensor 5. According to the actual measurement, when the ambient temperature is 28°C, every time the height sensor 5 rotates counterclockwise by 1 degree, the charging time of the inductance increases by 4 μs, and the height of the vehicle body increases by 4 mm. Under the condition of 28°C, the fluctuation range of the height signal is 0.3μs, and the error is less than 1%. However, when the ambient temperature rises from 28°C to 80°C, the fluctuation range of the height signal is 1.5 μs, and the error is less than 5%, which can fully meet the requirements for vehicle height detection.

Claims (2)

1. The utility model provides an air suspension passenger train body height detecting system, installs height sensor (5) between frame (1) and axle (4), characterized by: the height sensor (5) is fixed at one end of the swing rod (2), the other end of the swing rod (2) is movably connected with the connecting rod (3), and the other end of the connecting rod (3) is fixed on the axle (4); the height sensor (5) comprises a coil (7) and an iron core (6) which can move up and down in the coil (7), and the coil (7) is connected with a detection circuit (8).

2. The method of claim 1The utility model provides an air suspension passenger train automobile body height detecting system which characterized by: the detection circuit (8) comprises a coil (7) and a freewheeling diode D1 which are connected in parallel to the inverting terminal of an operational amplifier IC2, a resistor R3 is connected between the inverting terminal of the operational amplifier IC2 and the output terminal of the operational amplifier IC2 through a resistor R6^*Connected to the inverting terminal of the operational amplifier IC3, and a resistor R5 connected between the input terminal of the operational amplifier IC3 and the power supply Vcc^*The output end of the transistor is connected with the base electrode of a triode Q1, the collector electrode of the transistor is connected with a power supply Vcc1 through a resistor R8, and the emitter electrode of the transistor is connected with a pin 2 of a photoelectric coupler IC 4; a pin 6 at the output end of the photoelectric coupler IC4 is connected with a pin 5 of a Schmidt trigger IC5, and a pin 6 of the Schmidt trigger IC5 outputs a height signal; the resistors R1 and R2 are connected in series and then connected in parallel with the capacitor C1 to be connected between a power supply Vcc and the ground to form a given circuit, and after voltage division, the given circuit is connected to a pin 13 of the analog switch IC1, a pin 11 of the analog switch IC1 is connected with a single chip microcomputer, and a pin 3 of the output end of the analog switch IC1 is connected with the non-inverting end of the operational amplifier IC 2.

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