A height difference sensor

Abstract

The present invention discloses an altitude difference sensor, comprising an electromagnetic valve connected to an air path and closed upon receiving a fixed altitude signal; an absolute pressure sensor for sensing the altitude of an aircraft in real time; a differential pressure sensor for sensing altitude changes when the electromagnetic valve is closed; a first multiplier for outputting a corrected altitude difference signal according to the sensing results of the absolute pressure sensor and the differential pressure sensor; a second multiplier for modulating the aircraft altitude after differentiation and outputting an ascending and descending speed signal in an alternating current form; and a third multiplier for modulating the corrected altitude difference and outputting an altitude difference signal in an alternating current form. The altitude difference sensor of the present invention is a purely electronic product with a simple structure, convenient debugging, and reliable performance.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a height difference sensor. Background Art

[0002] The altitude difference sensor is an important component in the aircraft autopilot system. The system consists of a vacuum diaphragm, a differential mechanism, a hairspring, a positioner motor, an electromechanical converter motor, a servo motor and a speed measuring motor, a reduction gear system, an electromagnetic clutch, a power amplifier and other electromechanical systems. The basic principle is that the mechanical diaphragm senses the change in air pressure. When the altitude is "fixed" (the electromagnetic clutch is engaged and the motor stator is fixed), the displacement of the diaphragm is converted into the rotation angle of the motor rotor, and the motor winding outputs the "altitude difference" signal; in addition, by converting the displacement change rate of the diaphragm into the motor speed, the motor winding outputs the "lifting speed" signal. The existing altitude difference sensors have complex structures, are difficult to debug, and have low reliability. Summary of the invention

[0003] In view of the above problems in the prior art, an object of the present invention is to provide a height difference sensor with simple structure, convenient debugging and high reliability.

[0004] To achieve the above object, the technical solution of the present invention is:

[0005] A height difference sensor, comprising:

[0006] An electromagnetic valve, which is connected to the gas circuit and is closed when receiving a fixed height signal;

[0007] An absolute pressure sensor, which is connected to the gas path and is used to sense the aircraft altitude in real time;

[0008] A differential pressure sensor, one input end of which is connected to the gas circuit, and the other input end of which is connected to the output end of the electromagnetic valve, for sensing the change in air pressure (i.e., the change in altitude) when the electromagnetic valve is closed;

[0009] a first multiplier, the first multiplier being used to output a corrected height difference signal according to sensing results of the absolute pressure sensor and the differential pressure sensor;

[0010] A differential circuit, used for differentiating the aircraft altitude sensed in real time by the absolute pressure sensor;

[0011] A second multiplier is used to modulate the differentiated signal and output an AC lifting speed signal; the modulation is the multiplication of the differentiated signal and the intermediate frequency signal;

[0012] a subtractor for correcting the corrected height difference signal;

[0013] The third multiplier is used to modulate the corrected signal and output a height difference signal in an AC form.

[0014] The height difference sensor also includes a first signal threshold determination circuit connected to the first multiplier, which is used to output a return-to-zero gate signal when the output of the first multiplier is greater than a first threshold, and the first signal threshold is 0.3V.

[0015] The second signal threshold determination circuit is used to output a limit switch signal when the output of the first multiplier is greater than a second threshold, and the second signal threshold is 0.5V.

[0016] The height difference sensor of the present invention is a purely electronic product, abandoning the original electromechanical structure, and has a simple structure, convenient debugging and reliable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a principle diagram of the height difference sensor of the present invention. DETAILED DESCRIPTION

[0018] The height difference sensor of the present invention will be described in more detail below in conjunction with specific embodiments with reference to the accompanying drawings.

[0019] Figure 1 The schematic diagram of the altitude difference sensor of the present invention. As shown in the figure, the altitude difference sensor of the present invention includes: an electromagnetic valve, which is connected to the air circuit and is closed when receiving a fixed height signal (when the altitude is "set" at a certain altitude, the electromagnetic valve is closed); an absolute pressure sensor, which is connected to the air circuit and is used to sense the altitude of the aircraft in real time; a differential pressure sensor, one input end of the differential pressure sensor is connected to the air circuit, and the other input end is connected to the output end of the electromagnetic valve, which is used to sense the pressure change (i.e., altitude change) when the electromagnetic valve is closed. Since the same altitude change (such as ±30m) differs several times in the air pressure change on the ground and at high altitude, the first multiplier is used to correct the sensing results of the absolute pressure sensor and the differential pressure sensor, and output the corrected altitude difference signal. The absolute pressure sensor and the differential pressure sensor are silicon piezoresistive sensors.

[0020] The differential circuit differentiates the aircraft altitude sensed in real time by the absolute pressure sensor, and the differentiated signal is modulated by the second multiplier, and the modulation is the multiplication of the differentiated signal and the intermediate frequency signal (36V400Hz), and then the DC is isolated by capacitor coupling, and the AC form of the ascending speed signal is output through the transformer. When the aircraft is ascending, the phase of the signal is the same as that of the intermediate frequency signal, and the amplitude is proportional to the ascending speed; when the aircraft is descending, the phase is opposite to that of the intermediate frequency signal, and the amplitude is proportional to the descending speed.

[0021] The subtractor is used to calibrate the corrected height difference signal. Another input of the subtractor is a reference level, which is 10V in this example. The output of the subtractor is modulated by a third multiplier, which is a multiplication of the subtracted signal and the intermediate frequency signal (36V400Hz). After being isolated by capacitor coupling, the height difference signal in AC form is output through a transformer. When the aircraft is ascending, the phase of the signal is the same as that of the intermediate frequency signal, and the amplitude is proportional to the ascending height; when the aircraft is descending, the phase is opposite to that of the intermediate frequency signal, and the amplitude is proportional to the descending height.

[0022] As shown in the figure, the height difference sensor can also include a first signal threshold judgment circuit connected to the first multiplier, which is used to output a return to zero gate signal through voltage identification, photoelectric isolation, etc. when the output of the first multiplier is greater than the first threshold. In this example, the first signal threshold is 0.3V.

[0023] The height difference sensor may further include a second signal threshold determination circuit, which is used to output a limit switch signal through voltage identification, photoelectric isolation, etc. when the output of the first multiplier is greater than a second threshold. In this example, the second signal threshold is 0.5V.

[0024] The present invention is a purely electronic replacement product, which abandons the electromechanical structure of the original system and does not change the appearance and connection method of the original product, thereby realizing in-situ replacement, having a simple structure, convenient debugging and reliable performance.

Claims

1. A height difference sensor, characterized in that include: An electromagnetic gas valve, which is connected to the gas circuit and is closed when receiving a fixed height signal; An absolute pressure sensor, which is connected to the gas path and is used to sense the aircraft altitude in real time; A differential pressure sensor, one input end of which is connected to the gas circuit, and the other input end of which is connected to the output end of the electromagnetic valve, for sensing the height change when the electromagnetic valve is closed; a first multiplier, the first multiplier being used to output a corrected height difference signal according to sensing results of the absolute pressure sensor and the differential pressure sensor; A differential circuit, used for differentiating the aircraft altitude sensed in real time by the absolute pressure sensor; The second multiplier is used to modulate the differentiated signal with an intermediate frequency signal and output an AC speed signal; a subtractor for correcting the corrected height difference signal; The third multiplier is used to modulate the corrected signal with an intermediate frequency signal to output a height difference signal in an alternating current form.

2. The height difference sensor according to claim 1, wherein the intermediate frequency signal is a 36V400Hz signal.

3. The height difference sensor according to claim 1, wherein the height difference sensor further comprises a first signal threshold determination circuit connected to the first multiplier, for outputting a return-to-zero gate signal when the output of the first multiplier is greater than the first threshold. The height difference sensor according to claim 3 , wherein the first signal threshold is 0.3V.

5. The height difference sensor according to claim 1, further comprising a second signal threshold determination circuit connected to the first multiplier, for outputting a limit switch signal when the output of the first multiplier is greater than a second threshold. The height difference sensor according to claim 5 , wherein the second signal threshold is 0.5V.

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