JPS61263895A - Auto pilot for ship - Google Patents

Abstract

PURPOSE:To obtain optimum control of a steering gear with disturbance and noise removed, and save a fuel consumption, by utilizing a Kalman filter and a comparator for input of an actual rudder angle and computation of estimates of a bow azimuth and a turn rate as well as computation of an instruction rudder angle. CONSTITUTION:An actual rudder angle delta is input into a hull motion predicting section 12 for computing respective predictors psiP and psiP' of a bow azimuth psiand a turn rate psi'. The predictors psiP and psiP' are corrected according to a Kalman gain K computed from a system noise covariance Q and an observed noise covariance R, thereby obtaining respective estimates psiD and psiD'. The estimates psiD and psiD' are filtered by an estimating section 16 to output an estimated bow azimuth psi and an estimated turn rate psi', which are then compared with set values psim and psim', respectively. According to the result of comparison, an instruction rudder angle Ud for controlling a steering gear 8 is computed by a controller 7. In the course of computation, disturbance and noise which will inadvertently affect a steering operation are removed to thereby obtain high performance of course change and course maintenance and minimize a fuel consumption.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention uses the actual rudder angle of the hull and the Kalman gain to filter harmful disturbances, noise, etc. contained in the hull turn rate and heading. This invention relates to a marine autopilot in which a comparator compares a set value with a set value, and a controller calculates an optimal commanded rudder angle based on the comparison result.

<Conventional technology> The conventional technology will be described below with reference to the drawings.

FIG. 6 is a block diagram of a conventional marine autopilot.

In Fig. 6, 1 is the ship's hull, 2 is a gyro compass that outputs the heading ψ, and 3 is a turn rate calculation unit that outputs the turn rate φ (. represents the first-order differential) (in the figure, a differential circuit that calculates the heading ψ). (You may also use a separate turn rate meter (not shown)), and in step 4, enter the turn rate ψ and heading ψ to calculate the complex disturbance elements (waves, etc.) included in these.
This is a filter section that removes (filters) high-frequency components that have a harmful effect on internal steering, such as disturbances caused by tidal currents, wind, etc., noise, etc. - This is a filter section that consists of a second-order lag or second-order lag low-pass filter. Note that the cutoff frequency of the low-pass filter can be changed by changing the filter time constant. That is, a filter setting value Mf manually set in advance using an external input device is input to the input filter section 4, and each input value is filtered based on this value. 5 is a subtractor that takes the difference between the input cuff and a set turn rate φm set mechanically from the outside and outputs an estimated turn rate deviation ΔX\ψ; 6 is an estimated bow filtered by the input filter section 4; Input the difference Δψ between the heading ψ and the set heading ψm set mechanically from the outside, and calculate the proportional, integral, differential (P
ID) A controller which performs calculations and outputs the commanded rudder angle Udo, and 8 is a rudder machine which drives the rudder 9 based on the commanded rudder angle UdoS.

<Problems to be solved by the invention> By the way, a marine autopilot with such a configuration has
There were the following problems.

Since the input filter section 4 is configured with a first-order lag filter or a second-order lag filter, it is difficult to expect a sufficient filtering effect to remove complex disturbances, noise, etc. included in the heading ψ. That is, when the filter time constant is increased, the cutoff frequency of the input filter section 4 is decreased, and the frequency band for removing disturbances and noise is expanded, but the phase delay of the output signal with respect to the input signal is increased, which reduces the stability of the entire autopilot. The quality deteriorates. For this reason,
The cutoff frequency of the input filter section 4 can only be set in a frequency band higher than the cutoff frequency of the hull itself. This can be illustrated in a diagram as shown in the filter characteristic diagram of FIG.

In Fig. 7, the horizontal axis is the frequency, the vertical axis is the gain, A is the cutoff frequency of the hull itself, and B is the input filter section 4.
, then the cutoff frequency A of hull 1 is
and the cutoff frequency B of the input filter section 4.

In the conventional technology, the autopilot also works for disturbances, noise components, etc. included in the bandwidth τ, so in reality, the steering is wasted (hull 1 does not respond to steering in the bandwidth τ). ), it is difficult to achieve energy savings (improvement in fuel efficiency) of the pilot system.

The present invention has been made in view of the above-mentioned problems of the prior art, and is capable of filtering turn rate and heading without deteriorating the stability of the autopilot itself, and which eliminates disturbances that have a detrimental effect on steering. The purpose of the present invention is to provide a marine autopilot that eliminates noise, noise, etc. by using the actual steering angle and Kalman gain, performs steering that always enables optimal navigation, and minimizes fuel consumption.

Means for Solving the Problems> In order to achieve the above-mentioned object, the marine autopilot of the present invention inputs the actual steering angle of the hull, calculates a predicted heading value and a predicted turn rate value, and reduces system noise. Based on the Kalman gain obtained from the covariance value and the observed noise covariance value, the predicted heading value and predicted turn rate that were previously calculated are respectively corrected and input based on the corrected values. A filtering device configured using a Kalman filter that calculates an estimated heading and an estimated turn rate, which are estimated values of the turning rate and heading of the ship, respectively, and an estimated heading and heading obtained by filtering with this filtering device. The present invention is characterized by comprising a comparator that compares the estimated turn rate and a set value, and a controller that calculates a command rudder angle for controlling the rudder based on the comparison result.

Overview of Filtering Device> When noise such as disturbance is present, a difference occurs between, for example, the calculated heading and turn rate and the actually measured heading φ and U-turn rate ψ.

Disturbances occur in the hull as periodic movements (yawing), but if the hull is cut in front each time, resistance increases and energy is lost. However, in response to low-period disturbances, unless the ship is steered to a certain extent, there is a risk that the ship will move in an unexpected direction. Regarding the heading and turn rate, the Kalman filter separates what is really caused by the ship's hull from what is caused by disturbances and noise.The Kalman filter removes the frequency components that are harmful to steering between what is caused by the actual movement of the ship and what is caused by disturbances, and Predict the ship's heading by extracting the disturbances and values necessary for steering.
111 and turn rate predicted values are obtained, the predicted values are corrected using the Kalman gain from the Kalman gain calculation section, and the input values are filtered to output respective estimated values.

<Example> Hereinafter, a specific example of the above-described configuration will be described using the drawings. In the following drawings, parts that overlap with those in FIG. 6 are given the same numbers, and their explanations will be omitted.

FIG. 1 is a block diagram of a marine autopilot showing a specific embodiment of the present invention.

In FIG. 1, 10 is a filtering device. This filtering device 10 has an actual rudder angle input interface (hereinafter referred to as rADC function) that has an analog-to-digital conversion function (hereinafter referred to as rADC function) that inputs the actual rudder angle (analog value) δ of the hull 1 and converts it into a digital value of the actual rudder angle δD. Below II/F
11 (abbreviated as J) and the actual rudder angle δ0, go to the predicted heading value △ which is the predicted value of the heading ψ and turn rate φ from the current time (e.g. n) to the next time (e.g. n+1). A ship motion prediction unit 12 that calculates ψP and turn rate predicted value ψP, and a system noise covariance value Q (noise related to the ship) and an observation noise covariance value R (noise related to the observation device) which are fixed values in this embodiment. a Kalman gain calculation unit 13 that calculates the Kalman gain K at the current time (for example, n) by inputting the noise), and the heading (analog value) ψ
A heading human input I/F 14 inputs and converts the heading into a digital value of heading φ0, and a turn rate calculation unit 15 calculates a turn rate ψ0 by time-varying differentiation of the heading ψD.
Then, enter the heading ψ0, turn rate ψD, Kalman gain, predicted heading value ψP, and predicted turn rate A (ψP, calculate the bow correction based on the Kalman gain K, and calculate the calculated value based on the corrected value. The digital-to-analog conversion function (hereinafter referred to as rDAcIIllJ) that converts the digital value into an analog value and outputs it is output to 1/F17 and is also fed back to the hull motion prediction unit 12. Estimated heading ψ is 8
The command is guided to a controller 7 which calculates a command steering angle Ud.

By the way, the hardware when the filtering device 10 is constituted by a microprocessor is shown in FIG.

102 is a random access memory (RAM), 103 is a read-only memory (ROM), +04 is a heading that has an ADC II function that inputs an analog value of the heading ψ and converts it into a digital value. r/F 105 is an output 17F having an ADC function which inputs an analog value of the actual steering angle δ and converts it into a digital value, and a DAC Ill function which converts it into an analog value and outputs it.

FIG. 3 is a flow sheet of FIG. 1.

The filtering device of the present invention will be described below based on FIGS. 1 to 3. ! The functions of each part constituting 10 will be explained in detail.

Generally, when the rudder is turned to a certain angle, the hull 1 gradually starts turning, and continues turning steadily when it reaches a certain turn rate ψ. The initial setting value of the steering angle is the followability index Ts, which is the time it takes to reach approximately 63% of a constant angular velocity.
can be determined from the turning index Kg, which is the turn rate per degree of steering angle (in general, for the ship speed,
The followability index T5 is inversely proportional, and 3 is directly proportional to the turning index).

The algorithm of the filtering device 10 is as follows.

Using the tracking index TgI and the turning index Kg, the movement of the hull 1 (equation of motion of the hull) can be expressed approximately as follows: Ts・ψ+ψ−Ks・δ (1)
becomes. However, φ is the turning angular acceleration (... represents the second-order differential). Here, (1/Ts) of the equation is α, (K
s/Ts) as β and then converting it into a matrix, it can be expressed as follows. Here, X-F-X+8 ・δ
...(4) Y-H-X
...(5). Here, F, B, and H are matrices indicating the dynamic characteristics of the ship, X is the amount S of the ship's motion, Y is the amount observed by humans, and H is the observation matrix. Therefore, the filtering device 9=H-gold (7). However, '9'& tfi/L, *After the ring. Becomes an observation value engineer. The algorithm of each part for obtaining the equations (8) and (9) will be explained below.

Hull Motion Prediction Unit> At time n, the hull motion prediction unit 12 predicts the bow direction ψ and turn rate φ, which are the hull motion at the next time (n+1), based on the actual rudder angle δ.

This is expressed in a table using the determinant of the algorithm corresponding to equation (8). The predicted value φp is the value one step ahead from the current time n.

Kalman gain calculation section> The algorithm calculated by the Kalman gain calculation section 13 is K-PH MAR''...0
0P-FP+PFma -PH' R→ HP+Q・-(
12). However, (') is the transposition, the Kalman gain is the one that minimizes the variance of the estimation error due to system noise and IQIII noise, and P is the error covariance of the estimated value, which solves the above Ma] Rick-Riccati equation. It is obtained by

Estimating Unit> The estimating unit 16 corrects and predicts the predicted heading value ψp and predicted turn rate ψp predicted at the previous time (n-△1) at time n using the Kalman gain K. Ta. It is m. Based on this corrected value,
The estimated values of the input turn rate ψ and heading ψ of the hull 1 are calculated (13), and the result of equation (9) is obtained and output.

By the way, this filtering device 10 is not limited to the configuration shown in FIG. 11.

For example, in FIG. 1, the system noise covariance Q,
Although we have explained the case where the I-measured noise covariance R is set to a fixed value within filtering, as shown in Figure 4 (a block diagram in which the system noise covariance Q can be input from an external setting device), the system noise It is also possible to configure the filtering device 10 so that the covariance Q can be inputted from an external setting device, thereby adding a manual weather adjustment m*° function.

Here, if both sides of equation (4) are Laplace-transformed and summarized by X1%, we get:
becomes. However, S is the Laplace operator and (F+K) is the cutoff frequency of the filter. In equation (12),
When Q increases, K and (F+K) increase, and conversely, Q
It can be seen that when , K and (F+K) become smaller.

In addition, the observation noise covariance R is expressed as follows (14), (1
An automatic weather adjustment function can also be realized by defining as shown in equation 5). A block diagram of this specific configuration is shown in FIG.

R-R+[Y-Rei12...(14)K
-PH"[HPH' +l(] '...
・(15) Since the value of Y-Y during stormy weather becomes large, the Kalman gain K becomes small, and the cutoff frequency △ in equation (13) becomes small, and conversely, the value of Y-Y during calm water becomes small, The cutoff frequency increases (14).

It can be seen from equation (15).

Note that the filtering device 10 is not limited to implementation by a microcomputer as shown in FIG. 2, but can also be implemented by conventional discrete circuit elements.

<Effects of the Invention> As described above, the present invention has been specifically explained with reference to the real j1 tsuba. Correct calculations are made for the value and turn rate prediction value respectively,
A filtering device having a Kalman filter configuration is provided to obtain an estimated heading and turn rate by filtering the actually measured turn rate and heading based on the corrected values, and the estimated heading and turn rate from this filtering device are According to the marine autopilot of the present invention, which has a configuration in which the commanded rudder angle is calculated by the controller after comparing the respective set values, the Kalman filter does not have a phase delay of the output signal with respect to the input signal, so it has a negative effect on the steering. Disturbances, noise, etc. can be removed without compromising the stability of the autopilot system, which prevents unnecessary rudder.It has high course changing and course keeping abilities, and is highly reliable for ship transportation. . Therefore, fuel consumption can be minimized while satisfying high course keeping performance. Further, as shown in other embodiments, manual or automatic weather adjustment *i* can be added, so that filtering characteristics tailored to sea conditions can be obtained. Effects such as this can be obtained.

[Brief explanation of drawings]

115! 2 shows a block diagram of a marine motorcycle lot without showing a specific embodiment of the present invention, FIG. 4 and 5 are diagrams showing other embodiments of the present invention, FIG. 68 is a block diagram of a conventional marine autopilot, and FIG. 7 is a filter characteristic diagram. DESCRIPTION OF SYMBOLS 1... Hull, 2... Gyro compass, 3... Turn rate calculation part, 4-... Filter part, 7... Controller, 10... Filtering device, 11...
Tiger rudder angle input interface, 12... Hull motion prediction unit, 13... Kalman gain calculation unit, 15... Turn rate calculation unit, 16... Estimation unit, 17... Output 1
/F.

Claims (1)

[Claims] After filtering the turn rate of the ship and the heading obtained from the gyro compass, a comparator compares it with a set value, and based on the comparison result, a controller calculates a command rudder angle to control the rudder. In the marine autopilot of the above configuration, the predicted heading value and predicted turn rate calculated from the actual steering angle of the hull are corrected based on the Kalman gain obtained from the system noise covariance value and the observed noise covariance value. and a filtering device configured to calculate an estimated heading and an estimated turn rate, which are estimated values of the turn rate and heading of the hull input based on the corrected calculated values, and output them to the comparator. A marine autopilot that is characterized by: