JPH10268039A - Radio wave altimeter with automatic zero altitude correction function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave altimeter in which an altimeter measurement value in a state of an airframe apron is zero-corrected as a zero correction value in view of a fact that it is unreasonable that a zero correction value changing by an external factor is set as a constant. SOLUTION: Radio waves from an oscillator 11 are formed in a transmission pulse generating circuit 12 and transmitted from transmitting means 2. Reflection waves from a ground 6 are detected by a receiving pulse detecting circuit 13, and a time width from transmission to reception is measured by a pulse width measuring circuit 14. This actual value is subtracted a zero correction value of a memory circuit 18 by a subtracting circuit 15, and is converted into altitude data by a data outputting circuit 17 to be output. When the zero correction value is input according to an on signal of a leg switch in a state of apron and the state of apron is judged by an apron judging circuit 20, the memory circuit 18 stores the measurement value of the pulse width measuring circuit 14 in the apron state as a zero correction value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio altimeter mounted on an aircraft.

[0002]

FIG. 4 shows an aircraft 4 equipped with a radio altimeter (ALT) 1. The transmission means (T
X) 2, receiving means (RX) 3, ALT1 and TX2
During it is connected by cable length l _1, ALT1 and RX3
During is connected by a cable length l _2, the radio waves from ALT1 are transmitted and received. There aircraft 4 are legs 5 grounded to parked state in Figure, radio waves emitted toward the ground 6 TX2 is reflected by the ground 6, a reciprocating propagation distance l ₃ between the body bottom and ground.

[0003] As described above, even when the aircraft is parked, there is a predetermined separation distance l ₃ between the bottom surface of the aircraft and the ground surface.
The radio wave transmitted from LT1 is transmitted through cables l ₁ and l ₂ ,
Advanced does not become zero even in parked state space distance l ₃ from the reciprocating propagation. Therefore the measurement data output H of the altimeter in flight, it is necessary to subtract to zero corrects the zero correction value H ₀ commensurate from the measured values H ₁ in parked state. This zero-correction calculation equation is given by Equation 1.

[0004]

## EQU1 ## Measurement data output H of the radio altimeter = measured data actual measurement value H ₁ −zero correction value H ₀ Conventionally, the zero correction value H ₀ is embedded as a known fixed numerical value in the arithmetic circuit of the radio altimeter.

FIG. 5 is a system configuration diagram of a conventional radio altimeter 1. An oscillator 11 oscillates at 4.3 GHz, and a radio wave pulse-formed by a transmission pulse generation circuit 12 is transmitted from the TX 2 to the ground 6; RX3 reflected radio wave from earth 6
To receive. The reception signal is detected by the reception pulse detection circuit 13, and the time width from transmission from the transmission pulse generation circuit 12 to detection by the reception pulse detection circuit 13 is measured by the pulse width measurement circuit 14. A zero correction value storage circuit 16 for fixing and holding the zero correction value H ₀ in the parked state in advance is provided, and the subtraction circuit 15 calculates the zero correction value of the circuit 16 from the measurement value H ₁ of the pulse width measurement circuit 14. Subtract H ₀ . The subtraction result H = H ₁ −H ₀ is converted into altitude data by the data output circuit 17 and output as altitude output of the altimeter.

[0006]

However, the zero correction value H ₀ set as a known fixed value in the related art changes the length of the cable used, the mounting location of the airframe, and the like in the mounted airframe structure and the antenna-separated radio altimeter. Will change if This necessitated strict management of each mounted aircraft and the cables used, which made maintenance of the radio altimeter troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to consider the fact that it is unreasonable to embed a zero correction value, which changes due to external factors, as a constant in hardware or software as described above. It is another object of the present invention to provide a radio altimeter capable of automatically obtaining a zero correction value and automatically performing the zero correction.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radio altimeter mounted on an aircraft, a memory for storing, as a zero correction value, a measurement value measured when the mounted body is parked, and a measurement performed while the mounted body is in flight. And subtraction means for subtracting the zero correction value stored in the memory from the measured value and outputting altitude data.

The object of the present invention is to provide a memory for storing, as a zero correction value, a measurement value measured when the onboard aircraft is parked, and a zero correction value stored in the memory from a measurement value measured during flight of the onboard aircraft. Subtracting means for subtracting and outputting altitude data, and control means for controlling a parking state by a switch which is turned on / off when the onboard vehicle is parked and controlling the memory so that a zero correction value can be stored in the memory. Is achieved by

According to the above-described means, the measured value measured by transmitting and receiving radio waves while the onboard machine is parked is automatically stored as a zero correction value in the memory. Then, the subtraction means subtracts the zero correction value stored in the memory from the measurement value measured during the flight of the onboard aircraft, and outputs altitude data.

When the onboard machine is parked, the control means determines the parked state, controls the memory so that the zero correction value can be stored, and stores and updates the zero correction value measured during parking.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram of an embodiment of the present invention. A radio altimeter (ALT) 1 is mounted on an aircraft body, and a transmitting means (TX) 2 provided on a bottom surface of the mounted body.
From the ground to the ground 6, and the receiving means (RX) 3 receives the radio wave reflected from the ground. The ALT 1 measures a propagation time width of a transmission / reception radio wave to measure a distance (altitude) between the aircraft body and the ground.

A radio wave is oscillated by a 4.3 GHz oscillator 11, pulse-shaped by a transmission pulse generation circuit 12, and transmitted from a TX 2. The radio wave received by the RX 3 is detected by the reception pulse detection circuit 13, and the time width from emission of the radio wave to reception is measured by the pulse width measurement circuit 14. The measured value is subtracted by the subtraction circuit 15.
And the zero correction value stored in the zero correction value memory circuit 18 is subtracted. The subtracted time data is converted by the measured data output circuit 17 from the air propagation speed of the radio wave into altitude data, and is obtained as altitude output.

FIG. 2 shows a flight state (a) and a parked state (b) of the aircraft 4. The leg switch 7 is off during the flight, but the leg 5 is grounded in the parked state (b). The switch 7 is turned on by applying a load to the switch 7. This switch-on signal is input to the leg switch input circuit 19 in FIG. The judgment output is input to the memory circuit 18 to control the memory so that it can be stored. At this time, the measured value of the pulse width measurement circuit 14 measured when the onboard machine is parked is stored in the memory circuit 18 as a zero correction value.

FIG. 3 illustrates a processing flow of the measurement of the zero correction value to the storage in the memory circuit 18 and the subtraction of the subtraction circuit 15. First, time data is measured by the pulse width measurement circuit 14 (FIG. 3). Step 1). It is determined whether the measured value is within a predetermined zero correction value range (step 2). If the measured value is within the range, the leg ground switch 7 is turned on and it is determined whether the mounted body is parked (step 3). If the vehicle is parked, the measured value is stored in the memory 18 and set as a zero correction value (step 4). According to the determinations in steps 2 and 3, the measured value during the flight is directly input to the subtraction circuit 15 and the zero correction value in the memory 18 is subtracted (step 5), thereby obtaining zero-corrected measurement data (step 6). .

As described above, it is possible to provide a function of automatically performing the altitude zero correction by recognizing the measured data in the parked state of the onboard aircraft as the zero correction value. Even in the parked state, the radio altimeter can measure the altitude in the aircraft parked state by emitting and receiving radio waves. The altitude measured at this time includes the distance from the bottom of the aircraft to the ground, the delay due to the radio altimeter body and the length of the antenna cable used, etc., but the measured value in the parked state is used as the zero correction value This makes it possible to sufficiently cancel them from the measurement data output. The problem of guaranteeing the reliability here is how to correctly grasp the state of the aircraft parked. Generally, aircraft need to know that their legs are grounded on the ground, and often have a leg grounding switch that is activated by body gravity applied to the legs. By inputting this leg ground switch information, it can be reliably determined that the aircraft is landing on the ground,
By performing the zero correction function based on the leg ground switch information, high reliability can be guaranteed.

[0018]

As described above, according to the present invention, there is provided a function of automatically performing zero correction in consideration of all the changing conditions by mounting the altitude zero correction function required for a radio altimeter on an actual aircraft. By doing so, the reliability of the measurement data can be ensured. It is particularly useful in rotorcraft, where altitude measurements at low altitudes are important.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a state of a leg grounding switch of an aircraft body.

FIG. 3 is a flowchart illustrating the operation of FIG. 1;

FIG. 4 is an explanatory view of an aircraft body equipped with a radio altimeter.

FIG. 5 is a configuration diagram of a conventional radio altimeter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Radio altimeter, 2 ... Radio transmission means, 3 ... Radio reception means, 4 ... Aircraft body, 5 ... Leg, 6 ... Ground, 7 ... Leg switch, 11 ... Oscillator, 12 ... Transmission pulse shaping circuit, 13 ...
Received pulse detection circuit, 14 ... Pulse width measurement circuit, 15 ...
Subtraction circuit, 17: measurement data output circuit, 18: zero correction value memory circuit, 19: leg switch input circuit, 20: parking state determination circuit.

Claims (2)

[Claims] 1. An aircraft launches radio waves toward the ground,
A radio altimeter that measures the altitude between an aircraft and the ground by measuring the propagation time from the launch to the reception of the radio waves reflected by the ground, and the measured values when the onboard aircraft is parked Memory as a zero correction value, and subtraction means for outputting altitude data by subtracting the zero correction value from the measured value measured during the flight by the onboard aircraft in the memory and subtracting the zero correction value. Altimeter with automatic zero altitude correction function. 2. An aircraft emits radio waves toward the ground,
A radio altimeter that measures the altitude between an aircraft and the ground by measuring the propagation time from the launch to the reception of the radio waves reflected by the ground, and the measured values when the onboard aircraft is parked , As a zero correction value, subtraction means for subtracting the zero correction value stored in the memory from the measurement value measured during the flight of the onboard aircraft and outputting altitude data, and the onboard aircraft parked A radio altimeter with an automatic zero-altitude correction function, comprising: a control means for determining a parking state by a switch which is turned on / off by the controller and controlling the zero correction value to be stored in the memory.