阅读说明：本技术 一种基于惯性传感器的海浪起伏幅度检测方法及系统 (Method and system for detecting fluctuation amplitude of sea waves based on inertial sensor ) 是由 文捷 王永才 任勤雷 张明睿 李春旭 耿雄飞 姚治萱 于 2019-10-14 设计创作，主要内容包括：本发明公开了一种基于惯性传感器的海浪起伏幅度检测方法及系统,该方法基于在海面上设备安装的惯性传感器实现,所述方法包括：获取惯性传感器采集的加速度和角速度；基于加速度和角速度,在消除惯性传感器的重力加速度影响的基础上,计算惯性传感器在世界坐标系下的线加速度；利用带通滤波器对惯性传感器在世界坐标系下的z轴线加速度进行滤波,获取海浪频谱范围内的z轴线加速度；基于海浪频谱范围内的z轴线加速度,通过二次积分计算海浪在z轴方向的起伏幅度。本发明的方法能够在任意海浪情况下,实时检测海浪的起伏幅度；而且能够消除噪声的累积误差的影响,获得较为准确的海浪的运动位移的结果。(The invention discloses a method and a system for detecting the fluctuation amplitude of sea waves based on an inertial sensor, wherein the method is realized based on the inertial sensor installed on equipment on the sea surface, and the method comprises the following steps: acquiring acceleration and angular velocity acquired by an inertial sensor; on the basis of the acceleration and the angular velocity, on the basis of eliminating the influence of the gravity acceleration of the inertial sensor, calculating the linear acceleration of the inertial sensor under a world coordinate system; filtering the z-axis acceleration of the inertial sensor under a world coordinate system by using a band-pass filter to obtain the z-axis acceleration in a sea wave frequency spectrum range; and calculating the fluctuation amplitude of the sea waves in the z-axis direction through quadratic integration based on the z-axis acceleration in the sea wave frequency spectrum range. The method can detect the fluctuation amplitude of the sea waves in real time under the condition of any sea waves; and the influence of the accumulated error of the noise can be eliminated, and a more accurate result of the movement displacement of the sea waves is obtained.)

1. An inertial sensor-based wave fluctuation amplitude detection method is realized based on an inertial sensor installed on a sea surface device, and comprises the following steps:

acquiring acceleration and angular velocity acquired by an inertial sensor;

on the basis of the acceleration and the angular velocity, on the basis of eliminating the influence of the gravity acceleration of the inertial sensor, calculating the linear acceleration of the inertial sensor under a world coordinate system;

filtering the z-axis acceleration of the inertial sensor under a world coordinate system by using a band-pass filter to obtain the z-axis acceleration in a sea wave frequency spectrum range;

and calculating the fluctuation amplitude of the sea waves in the z-axis direction through quadratic integration based on the z-axis acceleration in the sea wave frequency spectrum range.

2. An inertial sensor-based wave fluctuation amplitude detection method according to claim 1, wherein the linear acceleration of the inertial sensor in the world coordinate system is calculated based on the acceleration and angular velocity acquired by the inertial sensor, on the basis of eliminating the influence of the gravitational acceleration of the inertial sensor; the method specifically comprises the following steps:

at the time t and in a sensor body coordinate system, detection data of the inertial sensorComprises the following steps:

wherein

according to the rotation matrix R (t) of the inertial sensor, the world coordinates of the inertial sensor are calculatedLinear acceleration under tether

Subtracting the gravity acceleration from the linear acceleration to obtain an acceleration f (t) after eliminating the influence of gravity:

wherein the content of the first and second substances,

3. An inertial sensor-based wave fluctuation amplitude detection method according to claim 2, wherein the calculation step of the rotation matrix r (t) of the inertial sensor specifically includes:

wherein s is a weighting parameter;then k is_PDetermines the cut-off frequency, k, of the complementary filter_IDetermines the time, k, for eliminating the static deviation_IHas a size of k_P0.01-0.1 times of;

R_w(t) is a gyroscope-based rotation matrix of the inertial sensor at time t, and is set to transmitThe period of sensor data acquisition is delta_tThen the inertial sensor is at t + delta_tThe moment gyroscope-based rotation matrix is R_w(t+δ_t)：

When t is 0, R_w(t) is an identity matrix;

R_a(t) is the rotation matrix of the inertial sensor at time t based on the acceleration sensor:

wherein θ (t), Φ (t), and ψ (t) are the pitch angle, roll angle, and yaw angle detected by the acceleration sensor, respectively:

4. an inertial sensor-based wave fluctuation amplitude detection method according to claim 1, wherein a band-pass filter is used to filter z-axis acceleration of the inertial sensor in a world coordinate system, so as to obtain z-axis acceleration in a wave spectrum range; the method specifically comprises the following steps:

designing a band-pass filter with cut-off frequencies of 0.04Hz and 0.25Hz, sampling frequency of 100Hz and transfer function of H(s):

using the band-pass filter to pair z-axis accelerations f superimposed with low and high frequency noise_z(t) filtering.

5. An inertial sensor-based wave fluctuation amplitude detection method according to claim 4, wherein the fluctuation amplitude of the waves in the z-axis direction is calculated by quadratic integration based on z-axis acceleration in a wave spectrum range, specifically:

acceleration f based on z axis_z(t), calculating the fluctuation amplitude of the sea waves in the z-axis direction by a quadratic integration method:

wherein p is_z(t) and v_z(t) displacement and speed of motion, p, of the sea wave in the z direction at time t_z(0)＝0，v_z(0)＝0。

6. A method of detecting the heave amplitude of a sea wave based on an inertial sensor according to claim 5, further comprising: filtering the displacement and the movement speed of the sea waves in the z direction:

with a transfer function of H₁High pass filter pair of(s)_z(t) and v_z(t) filtering:

the cut-off frequency of the high-pass filter is 0.01 Hz.

7. An inertial sensor-based wave amplitude detection system, the system comprising:

the detection module is used for acquiring the acceleration and the angular velocity acquired by the inertial sensor;

the calculation module is used for calculating the linear acceleration of the inertial sensor under a world coordinate system on the basis of eliminating the influence of the gravity acceleration of the inertial sensor on the basis of the acceleration and the angular velocity; filtering the z-axis acceleration of the inertial sensor under a world coordinate system by using a band-pass filter to obtain the z-axis acceleration in a sea wave frequency spectrum range; and calculating the fluctuation amplitude of the sea waves in the z-axis direction through quadratic integration based on the z-axis acceleration in the sea wave frequency spectrum range.

Technical Field

The invention relates to the field of ocean monitoring, in particular to a method and a system for detecting the fluctuation amplitude of sea waves based on an inertial sensor.

Background

Sea waves are the propagation of sea surface fluctuation shapes, water particles leave an equilibrium position, do periodic vibration and propagate in a certain direction to form a fluctuation, the vibration energy of the water particles forms kinetic energy, the fluctuation energy of the sea waves generates potential energy, and the accumulated amount of the two energies is surprising. In global oceans, the total energy of only the storms and swells is equivalent to half the solar energy reaching the outside of the earth. The energy of the ocean waves rolls forward in the direction of wave propagation. Thus, sea waves are in fact wave propagation of energy. The wave period of the sea waves ranges from a few tenths of a second to more than hours, the wave height ranges from a few millimeters to tens of meters, and the wavelength ranges from a few millimeters to thousands of kilometers.

The wave height of the wind waves, the surge waves and the near-shore waves is several centimeters to more than 20 meters, and the maximum wave height can reach more than 30 meters. The wave is the wave generated by the sea water under the action of wind force, a plurality of waves with different heights and lengths can be generated at the same time, the wave surface is steep, the wavelength is short, wave flowers or piece foams are often arranged near the wave crest, and the propagation direction is consistent with the wind direction. Generally speaking, the longer the wind in the same state acts on the sea surface, the larger the sea area range is, and the stronger the wind waves are; when the wind waves reach a fully grown state, the wind waves do not increase any more. The waves formed after the waves leave the area where the wind blows are called swell. The wind waves are generally classified into 10 levels and the swell into 5 levels according to the wave height. The level 0 is free of waves and surges, and the sea level is as same as the mirror; 5-grade large waves and 6-grade large waves correspond to 4-grade large surges, and the wave height is 2-6 meters; level 7, rough billows, level 8, rough billows, level 9, corresponding to level 5 billows, with wave height of 6.1 m to more than 10 m.

Ocean wave motion is one of the important forms of movement of seawater. There are fluctuations from the sea surface to the interior of the ocean. In big oceans, if the sea surface is wide, the wind speed is high, the wind direction is stable, and the blowing time is long, sea waves are necessarily strong, such as the frequent billows rolling on the ocean surface of the west wind belt of the northern and northern hemispheres; although the sea area of the equatorial calm zone and the calm zone of the auxiliary tropical zone of the south and north hemispheres is wide, the sea waves are generally very small because the wind power is weak and the wind direction is uncertain.

Sea waves can be seen as being composed of an infinite number of component waves of different amplitudes, different frequencies, different directions, and disordered phases. These component waves constitute the wave spectrum. This spectrum describes the distribution of ocean wave energy relative to the individual component waves, hence the name "energy spectrum". It is used to describe the distribution of energy within ocean waves with respect to frequency and direction. To study the important concept of sea waves. It is generally assumed that ocean waves are formed by the superposition of a number of random positive arcs. The constituent waves of different frequencies have different amplitudes and thus different energies. A function S (ω) of the circular frequency ω is provided, and the energy of each component wave of the sea wave is proportional to S (ω) ω, in the interval from ω to (ω + ω), and S (ω) represents the energy of these component waves, which represents the distribution of energy over frequency, and is therefore called the frequency spectrum or energy spectrum of the sea wave. Similarly, a function S (ω, θ) is provided which includes the circular frequency ω and wave direction θ of the component waves, and the energy of each component wave is proportional to S (ω, θ) ω θ in the interval from ω to (ω + ω) and from θ to (θ + ω), so that S (ω, θ) represents the distribution of energy to ω and θ, referred to as the directional spectrum of the ocean wave. Converting the circular frequency of the component wave into a wave number to obtain a wave number spectrum; the frequency ω is converted to 2 π (the frequency is the reciprocal of the period), resulting in the number of S () spectra expressed. The above various spectra are collectively referred to as the wave spectrum.

The method for calculating the wave spectrum comprises two methods: the first is to derive a semi-theoretical and semi-empirical wave spectrum by utilizing the wave height and period obtained by observation; the second method is to calculate the correlation function by using the record of the time variation of the wave surface measured by a fixed point, and then calculate the spectrum. Spectra were also developed by establishing energy balance equations. The spectrum obtained at present is mainly determined on the basis of observation data. However, due to the lack of accurate wind and wave observation, some of the proposed spectra are very different from each other. The analysis and research of the wave spectrum are very important, the reflection parts of the breakwater and the sea surface to the radar can be reasonably designed according to the wave spectrum, and wave factors such as wave height, period and the like can be calculated by utilizing the wave spectrum.

For ships and buoys at sea, it is very important to detect the motion amplitude of sea waves, but currently, there is no relevant effective means and method.

Disclosure of Invention

The invention aims to overcome the technical defects and provides a method for detecting the fluctuation amplitude of sea waves based on an inertial sensor.

In order to achieve the above object, the present invention provides a method for detecting a wave fluctuation amplitude based on an inertial sensor, the method being implemented based on the inertial sensor installed on a sea surface, the method comprising:

on the basis of the acceleration and the angular velocity acquired by the inertial sensor, calculating the linear acceleration of the inertial sensor in a world coordinate system on the basis of eliminating the influence of the gravity acceleration of the inertial sensor;

filtering the z-axis acceleration of the inertial sensor under a world coordinate system by using a band-pass filter to obtain the z-axis acceleration in a sea wave frequency spectrum range;

and calculating the fluctuation amplitude of the sea waves in the z-axis direction through quadratic integration based on the z-axis acceleration in the sea wave frequency spectrum range.

As an improvement of the above method, the linear acceleration of the inertial sensor in the world coordinate system is calculated based on the acceleration and the angular velocity acquired by the inertial sensor and on the basis of eliminating the influence of the gravitational acceleration of the inertial sensor; the method specifically comprises the following steps:

at the time t and in a sensor body coordinate system, detection data of the inertial sensor

Comprises the following steps:

wherein

The unit of the acceleration of the inertial sensor in the three directions of x, y and z is m/s2 under a sensor body coordinate system;

the angular velocity of the inertial sensor in three angles of overturning, pitching and yawing is in unit of rad/s under a sensor body coordinate system;

according to the rotation matrix R (t) of the inertial sensor, calculating the linear acceleration of the inertial sensor in the world coordinate system

Subtracting the gravity acceleration from the linear acceleration to obtain an acceleration f (t) after eliminating the influence of gravity:

wherein the content of the first and second substances,

is composed of

Three components of (a); f. of_x(t),f_y(t),f_z(t) is the linear acceleration of the inertial sensor in the x, y, z directions, respectively.

As an improvement of the above method, the step of calculating the rotation matrix r (t) of the inertial sensor specifically includes:

wherein s is a weighting parameter;

then k is_PDetermines the cut-off frequency, k, of the complementary filter_IDetermines the time, k, for eliminating the static deviation_IHas a size of k_P0.01-0.1 times of;

R_w(t) is a gyroscope-based rotation matrix of the inertial sensor at time t, and the period of sensor data acquisition is delta_tThen the inertial sensor is at t + delta_tThe moment gyroscope-based rotation matrix is R_w(t+δ_t)：

When t is 0, R_w(t) is an identity matrix;

R_a(t) is the rotation matrix of the inertial sensor at time t based on the acceleration sensor:

wherein θ (t), Φ (t), and ψ (t) are the pitch angle, roll angle, and yaw angle detected by the acceleration sensor, respectively:

as an improvement of the above method, the z-axis acceleration of the inertial sensor in the world coordinate system is filtered by using a band-pass filter, so as to obtain the z-axis acceleration in the sea wave frequency spectrum range; the method specifically comprises the following steps:

designing a band-pass filter with cut-off frequencies of 0.04Hz and 0.25Hz, sampling frequency of 100Hz and transfer function of H(s):

using the band-pass filter to pair z-axis accelerations f superimposed with low and high frequency noise_z(t) filtering.

As an improvement of the above method, based on the z-axis acceleration in the wave spectrum range, the fluctuation amplitude of the wave in the z-axis direction is calculated by quadratic integration, specifically:

acceleration f based on z axis_z(t), calculating the fluctuation amplitude of the sea waves in the z-axis direction by a quadratic integration method:

wherein p is_z(t) and v_z(t) displacement and movement speed of the sea waves in the z direction at the moment t respectively; p is a radical of_z(0)＝0，v_z(0)＝0。

As an improvement of the above method, the method further comprises: filtering the displacement and the movement speed of the sea waves in the z direction:

with a transfer function of H₁High pass Filter pair of(s)'_z(t) and v'_z(t) filtering:

the cut-off frequency of the high-pass filter is 0.01 Hz.

The invention also provides a wave fluctuation amplitude detection system based on the inertial sensor, which comprises:

the detection module is used for acquiring the acceleration and the angular velocity acquired by the inertial sensor;

the calculation module is used for calculating the linear acceleration of the inertial sensor under a world coordinate system on the basis of eliminating the influence of the gravity acceleration of the inertial sensor on the basis of the acceleration and the angular velocity; filtering the z-axis acceleration of the inertial sensor under a world coordinate system by using a band-pass filter to obtain the z-axis acceleration in a sea wave frequency spectrum range; and calculating the fluctuation amplitude of the sea waves in the z-axis direction through quadratic integration based on the z-axis acceleration in the sea wave frequency spectrum range.

The invention has the advantages that:

1. the method can detect the fluctuation amplitude of the sea waves in real time under the condition of any sea waves;

2. the method can eliminate the influence of the accumulated error of the noise and obtain a more accurate result of the movement displacement of the sea waves.

Drawings

FIG. 1 illustrates the acceleration component of an IMU when the IMU is not subject to other external forces, but only gravity, at a given attitude

A schematic diagram of the relationship with the gravitational acceleration g;

FIG. 2 is a schematic diagram of IMU detection signals mixed with high frequency noise and low frequency noise;

FIG. 3 is an amplitude response curve for a band pass filter;

FIG. 4 is a schematic diagram of an IMU detection signal with low frequency noise and high frequency noise filtered;

FIG. 5 is a schematic diagram of a calculated z-direction movement velocity of a sea wave;

FIG. 6 is a schematic diagram of a calculated z-direction motion position of a sea wave;

FIG. 7 is a graph comparing a filtered wave velocity estimate to a true value;

FIG. 8 is a graph comparing a wave displacement estimate to a true value after filtering;

fig. 9 is a schematic diagram of an inertial sensor-based wave amplitude detection system.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.