JPH0834396A - Automatic steering gear for ship - Google Patents

Abstract

PURPOSE:To remove the instability of an automatic steering system resulting from the non-linear element of an automatic steering gear by coming the combination of the automatic steering system and a generalized control object to be controlled into an Hinfinity control problem. CONSTITUTION:When a set course thetaIN is input into an automatic steering system, a first adder 11 obtains deviation ERR between the set course thetaIN and a bow bearing thetaOUT. The automatic steering gear 12 obtains a command steering angle deltaC by the deviation ERR, and outputs it to a second adder 13. Also the second adder 13 controls the results obtained by deducting the disturbance (d) of angle conversion from the command steering angle deltaC, and outputs it to an object 14. Then a third adder 15 deducts a detected disturbance dv of a bow bearing detector from an output signal phi of the control object 14, and generates a bow bearing thetaOUT. The bow bearing thetaOUT is fed back to the first adder 11. Thus a stable closed loop is formed so that the deviation ERR becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for an automatic steering system for a ship, and more particularly to improvement of an autopilot for such a control system.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram schematically showing a control system of a conventional automatic steering system for ships. Hereinafter, such a control system will be simply referred to as an automatic steering system. The automatic steering system includes an adder 11, an automatic steering device, that is, an autopilot 12, a steering device 16, a hull 14-1, and a heading detector 14-2.

Set course θ _IN as an input signal to the automatic steering system
Is entered. The adder 11 has a set course θ _IN and a heading θ
_Calculate the deviation ERR of _OUT . The automatic steering device, that is, the autopilot 12 inputs the deviation ERR and inputs the command steering angle δ.
Output _C. The command steering angle δ _C is supplied to the steering gear 16.

The steering machine 16 has a servo mechanism for causing the steering angle δ to quickly follow the command steering angle δ _C , and corresponds to a first-order lag element. A disturbance d such as wind and waves acts on the hull 14-1. The hull 14-1 can be considered as a motion system that rotates around the azimuth axis of the ship. The hull 14-1 has a rudder angle δ
The angle-converted disturbance d is used as an input signal, and the angular velocity dθ / dt in the bow direction is used as an output signal.

The heading detector 14-2 calculates the heading θ _OUT from the angular velocity dθ / dt of the heading. The heading detector 14-2 may include a gyro compass, a magnetic compass, or the like. The heading θ _OUT is fed back to the adder 11. A stable closed loop is configured so that the deviation ERR output from the adder 11 becomes zero. At this time, the heading θ _OUT is output as an output signal of the automatic steering system.

The structure and operation of the conventional automatic steering device, that is, the autopilot 12, will be described with reference to FIG. The autopilot 12 has a linear element 12-1 and a non-linear element 12-2.
And inputs the deviation ERR and outputs the command steering angle δ _C.
The linear element 12-1 has a function of proportional + integral + derivative (PID) control and a function of a filter. Non-linear element 12
-2 has a weather adjustment mechanism.

The proportional (P) operation and the derivative (D) operation function to maintain the stability of the hull during automatic steering in the frequency band of the normal automatic steering system, and the integral (I) operation causes the disturbance d to affect the hull. When it acts on 14-1, it functions to steadily reduce the deviation ERR of the heading θ _OUT generated in the hull 14-1 to zero, and operates in the low frequency range used in normal operation. The filter function operates so as to remove the disturbance d in the high frequency range.

The weather adjusting mechanism operates so as to reduce an unnecessary operation amount of the steering gear 16 caused by the disturbance d. Thus, the deviation signal ERR is processed by each operation of the linear element 12-1 and the non-linear element 12-2 of the autopilot 12, and the command steering angle δ _C is generated.

[0009]

A conventional autopilot 12 has a linear element 12-1 and a non-linear element 12-2, each of which is configured to independently achieve its function and purpose. Has been done. The stability of the automatic steering system is ensured mainly by the proportional action (P) and the differential action (D) of the linear element 12-1.

However, the weather adjusting mechanism which is the non-linear element 12-2 causes, for example, continuous swinging of the bow (yawing) called self-excited oscillation, which may impair the stability of the automatic steering system. It is pointed out that there is. In particular, in the case of a ship with an unstable course, it is also reported that self-excited oscillation by such a weather adjustment mechanism is inevitable even within the adjustment range of a normal automatic steering system.

The weather adjusting mechanism includes a non-linear element (backlash, double steering angle ratio, etc.) without a phase delay, and based on the amplitude of the disturbance d included in the deviation ERR, the backlash width, the gain switching width, etc. Are in control. this is,
This means that it is difficult for the weather control mechanism to consider the frequency characteristic of the disturbance d. As a result, as described above, it is not possible to expect the function of the weather adjusting mechanism to reduce the unnecessary operation amount generated in the steering device 16 due to the disturbance d.

In view of the above point, the present invention aims to eliminate the instability of the automatic steering system due to the non-linear element 12-2 of the autopilot 12.

In view of this point, the present invention has an object to secure the stability of the automatic steering system by configuring the autopilot 12 with only the linear element 12-1.

[0014]

According to the present invention, as shown in FIG. 1, for example, a closed loop control of an automatic steering device that inputs a signal indicating a deviation of a heading from a set course and outputs a commanded steering angle. In the marine vessel automatic steering apparatus configured as described above, the generalized controlled object 100 as an object to be controlled and the automatic steering apparatus 12 are combined to result in the H∞ control problem.

According to the present invention, for example, as shown in FIG. 2, in the automatic steering device for a ship, the generalized controlled object 100 does not apply unnecessary operation to the automatic steering device due to disturbance. A first weighting function 17 having a stable frequency characteristic, a second weighting function 18 having a frequency characteristic that prevents a steady error caused by a disturbance in a low frequency range from remaining in the deviation, and the controlled object 14 are integrated. It is characterized in that it is configured by converting.

According to the present invention, in the automatic steering system for a ship, the generalized control target 100 further subtracts the angle conversion value of the disturbance from the commanded steering angle which is the output signal of the automatic steering system 12, and steers the steering angle. It is characterized by having an adder 13 for obtaining

According to the present invention, in the marine vessel automatic steering device, the controlled object 14 is formed by integrating a hull and a heading detector.

According to the present invention, in the marine vessel automatic steering system, the transfer function from the disturbance to the output signal of the automatic steering system is less than or equal to the reciprocal of the first weighting function.

According to the present invention, in the marine vessel automatic steering system, the transfer function from the disturbance to the input signal of the automatic steering system is less than or equal to the reciprocal of the second weighting function.

[0020]

According to the present invention, the automatic steering system is treated as H∞ control, and the problem of such automatic steering system is solved by reducing it to the H∞ control problem.

The automatic steering system is composed of two elements, an automatic steering device, that is, an autopilot 12 and a generalized controlled object 100, and the generalized controlled object 100 is composed of a controlled object 14 and two weighting functions 17 and 18. The controlled object 14 is formed by integrating the hull 14-1 and the heading detector 14-2.

The first weighting function 17 has a frequency characteristic that avoids an unnecessary amount of operation of the steering gear 16 due to the disturbance d, and the second weighting function 18 has a low frequency range. The frequency characteristic is such that a steady error does not remain in the deviation ERR with respect to the disturbance d.

The H∞ control problem is reduced by quantifying the frequency characteristics of the evaluation quantities Z _T , Z _Q and the deviation ERR of the command steering angle δ _{C with} respect to the disturbance d.

According to the present invention, the automatic steering device, that is, the autopilot 12 guarantees the stability of the automatic steering system against the disturbance d having a frequency ranging from the low range to the high range, and the steering system 1
6 has a frequency characteristic that eliminates the occurrence of an unnecessary manipulated variable.

[0025]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 2, the corresponding parts in FIGS. 5 to 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a block diagram of a control system, that is, an automatic steering system of an automatic steering system for a ship according to the present invention. Such an automatic steering system includes a first adder 11, an automatic steering device, that is, an autopilot 12, a second adder 13, a control target 14, and a third adder 13.
And an adder 15 of. The control target 14 is an integration of the hull 14-1 and the heading detector 14-2 shown in FIG. The steering gear 16 is omitted because the response of the steering gear 16 is about one digit faster than the response of the automatic steering system, and the dynamic characteristics thereof can be ignored.

Set course θ _IN as an input signal to the automatic steering system
Is entered. The first adder 11 obtains the deviation ERR between the set course θ _IN and the heading θ _OUT . The automatic steering device, that is, the autopilot 12 inputs the deviation ERR and outputs the command steering angle δ _C. The command steering angle δ _C is supplied to the second adder 13.

The second adder 13 subtracts the angle-converted disturbance d from the command steering angle δ _C and outputs the result to the controlled object 14. The third adder 15 subtracts the detection disturbance d _V of the bow direction detector 14-2 from the output signal φ of the controlled object 14,
Generate heading θ _OUT . Such a heading detector 14
The detected disturbance d _{V of} −2 is not shown in the block diagram of FIG.
It is newly added here.

The heading θ _OUT is fed back to the first adder 11. Deviation ERR which is the output of the adder 11
A stable closed loop is constructed so that is zero. At this time, the heading θ _OUT is output as an output signal of the automatic steering system.

In FIG. 1, the transfer function from the disturbance d to the command steering angle δ _C , that is, the first transfer function T (s) is

[0031]

## EQU1 ## T (s) = P (s) K (s) / [1 + P (s)
K (s)]

## EQU1 ## The transfer function from the disturbance d to the deviation ERR, that is, the second transfer function Q (s) is

[0033]

## EQU00002 ## Q (s) = P (s) / [1 + P (s) K (s)]

It becomes K (s) is auto pilot 12
, P (s) is the transfer function of the controlled object 14, and s is the Laplace operator.

Next, the first and second transfer functions T (s), Q
(S) Set quantitative specifications. Such specifications are defined by two weighting functions W _T (s) and W _Q (s).
The first weighting function W _T (s) has a predetermined frequency characteristic so as not to give unnecessary operation to the steering gear 16 due to the disturbance d,
The second weighting function W _Q (s) has a predetermined frequency characteristic so that a steady error does not remain in the deviation ERR with respect to the disturbance d having a low wave number.

The quantitative specifications of the transfer functions T (s) and Q (s) are expressed by the gain of the frequency expression as follows.

[0037]

[Equation 3] | T (jω) | <1 / | W _T (jω) |, ∀ω | Q (jω) | <1 / | W _Q (jω) |, ∀ω

Where ω is the frequency and j is the imaginary unit.

An automatic steering system which satisfies the specifications and guarantees the stability of the autopilot 12 can be reduced to a so-called H∞ control problem. For details of the H ∞ control problem, see, for example, “SIC Summer Seminar '92 -Automatic Steering System Design Method Based on New Control Theory”,
See The Society of Instrument and Control Engineers, 1992.

An example of the present invention will be described in detail with reference to FIG. In order to reduce the automatic steering system shown in FIG. 1 to the H ∞ control problem, it is replaced with an automatic steering system including the generalized controlled object 100 and the autopilot 12. Here, the generalized controlled object 100 is one in which the first and second weighting functions 17 and 18 and the controlled object 14 are integrated, as shown in the figure. Note that the set course θ _IN = 0 is set for simplification.

The first weighting function 17 inputs the command steering angle δ _C and outputs the signal Z _T , and the second weighting function 18 inputs the output signal φ of the controlled object 14 and outputs the signal Z _Q. . First
The output signal Z _T of the weighting function 17 represents the evaluation value of the Specification (first type number 3) required for the instruction steering angle [delta] _C to the disturbance d, the output signal Z _Q of the second weighting function 18 is the disturbance It represents the evaluation amount of the required specification (the second expression of the equation 3) of the deviation ERR with respect to d _V.

The generalized controlled object 100 inputs the disturbances d, d _V and the command steering angle δ _C , and evaluates Z _T , Z _Q and the deviation ER.
Output R. When the transfer function of the controlled object 100 is G (s), the following relationship is established.

[0043]

[Equation 4]

However, the Laplace operator s is omitted unless otherwise specified. Substituting the relational expression of the autopilot 12, that is, the expressions of the equations 1 and 2 into this equation, the following equation is obtained.

[0045]

[Formula 5] Z _T = W _T · [PK / (1 + PK)] · d = W _T Td Z _Q = W _Q · [P / (1 + PK)] · d = W _Q Qd

In this way, the specifications of the equation (3) are formulated. As a result, the autopilot 12 capable of guaranteeing the stability of the automatic steering system is obtained.

Next, the operation of the automatic steering system of this example will be described.
First, the second transfer function Q (s) and the second weighting function W
Consider the relationship of _Q (s). Second transfer function Q
(S) is the deviation ER even when the disturbance d including the DC component acts.
It is necessary for R to have a frequency characteristic such that a steady error does not occur. The transfer function P (s) of the controlled object 14 is expressed as follows.

[0048]

## EQU6 ## P (s) = K _S / s (sT _S +1)

K _S is a turning gain, T _S is a time constant,
Both are maneuverability indexes of the hull 14-1. s is a Laplace operator. The fact that s is included in the denominator factor depends on the integral characteristic of the bow direction detector 14-2. By substituting the equation (6) into the equation (2), the following equation is obtained.

[0050]

## EQU00007 ## Q (s) = K _S / [s (sT _S +1) + K _S K (s)]

The transfer function K (s) of the autopilot 12 must include an integral element in order to reduce the steady-state error of the deviation ERR due to the disturbance d to zero. Therefore, the second weighting function W _Q (s) may be selected as follows, for example.

[0052]

## EQU8 ## W _Q (s) = (s + 1 / T _Q ) a _Q / (s + ε)

Here, T _Q is a time constant, a _Q is a constant, ε is a sufficiently small constant, and s is a Laplace operator.

FIG. 3 shows a Bode diagram of the second transfer function Q (s). The vertical axis represents the gain, and the horizontal axis represents the frequency ω (rad /
s). It can be seen that the second transfer function Q (s) is frequency-shaped by the second weighting function _WQ (s) and conforms to the specifications shown in the equation (3). As shown, the second transfer function Q (s) has a differential characteristic in the low frequency range (ω <1 / T _Q ). Therefore, according to the equation (7), the autopilot 12 has an integral element.

Next, consider the relationship between the first transfer function T (s) and the first weighting function W _T (s). The second transfer function Q (s) is a transfer function from the disturbance d to the command steering angle δ _C , but from the set course θ _IN to the heading θ _OUT .

Therefore, the first weighting function W _T (s) is used to secure the frequency range necessary for the automatic steering system and to cause the disturbance d in the steering machine 16.
It must have a frequency characteristic that does not give unnecessary operation due to. First weighting function W
_T (s) is selected as follows, for example.

[0057]

## EQU00009 ## W _T (s) = (s + 1 / T ₁ ) a _T / (s + 1 / T ₂ )

Here, T ₁ and T ₂ are time constants (T ₁ >
T ₂ ), a _T is a constant, and s is a Laplace operator.

FIG. 4 shows a Bode diagram of the first transfer function T (s). The vertical axis represents the gain, and the horizontal axis represents the frequency ω (rad /
s). As shown in the figure, it can be seen that the first transfer function T (s) is frequency-shaped by the first weighting function W _T (s) and conforms to the specifications shown in the equation (3). In FIG. 4, T _R is the time constant of the equivalent first-order lag element of the steering gear 16. It can be seen that the first transfer function T (s) is limited by the first weighting function W _T (s) in the frequency region lower than the response frequency of the steering device 16.

The time constants in FIGS. 3 and 4 have the following relationship.

[0061]

[Equation 10] T _Q ＞ T ₁ ＞ T _R ＞ T ₂

Next, the first and second transfer functions T (s),
Transfer function K of the autopilot 12 that satisfies Q (s)
Derive (s). The transfer function P (s) of the controlled object 14,
The first and second weighting functions W _T (s) and W _Q (s) are expressed in the state space as follows.

[0063]

X _Q '= A _Q x _Q + B _Q u _Q y _Q = C _Q x _Q + D _Q u _Q x _T ' = A _T x _T + B _T u _T y _T = C _T x _T + D _T u _T x _P '= A _P x _P + B _P u _P y _P = C _P x _P + D _P u _P

Here, x, u, and y are time functions and represent a state vector, an input vector, and an output vector, respectively. The sign 'is a differential symbol. A, B, C, and D respectively represent a matrix of states, a matrix of inputs, a matrix of outputs, and a matrix of direct terms from inputs to outputs. The subscripts T, Q, P are
It means that they belong to the weighting functions W _T (s), W _Q (s) and the transfer function P (s) of the controlled object 14, respectively. The elements of each matrix are represented as follows.

[0065]

(Equation 12)

[Mathematical formula-see original document] Using the equations of equation 11 and equation 12,
The transfer function G (s) of the controlled object 100 shown in the equation is expressed in the state space as follows.

[0067]

X '= Ax + B ₁ w + B ₂ u z = C ₁ x + D ₁₁ w + D ₁₂ u y = C ₂ x + D ₂₁ w + D ₂₂ u

Here, x, w, u, z, and y are time functions, and the state vector, the disturbance input vector, and
It is a control input vector, an evaluation output vector, and an observation output vector. These vectors are represented as:

[0069]

X 14 [x _T , x _Q , x _P ] ^T w ≡ [d, d _V ] ^T u ≡ δ _C z ≡ [z _T , z _Q ] ^T y ≡ ERR

Further, the matrices A, B ₁ , B ₂ , C ₁ , C ₂ , D
₁₁ , D ₁₂ , D ₂₁ , and D ₂₂ are expressed as follows.

[0071]

(Equation 15)

The subscript T on the right shoulder indicates a transposed matrix. At this time, the transfer function K (s) of the autopilot 12 that satisfies the above-mentioned specifications is expressed as follows, for example.

[0073]

## EQU16 ## K (s) = C _K (sI−A _K ) ⁻¹ B _K

In this equation, the subscript (-1) on the right shoulder indicates an inverse matrix, and A _K , B _K and C _K are expressed as follows.

[0075]

[Expression 17] A _K = (A−B ₁ D ₂₁ ^T C ₂ ) + Y (C ₁ ^{T
_{C 1 / γ 2 -C 2 T}} C 2) + (B 2 + YC 1 T D 12 / γ
^{_{2) C K B K = B}} 1 D 21 T + YC 2 T C K = - (D 12 T C 1 + B 2 T X) (I-YX / γ 2)
^-1

Here, X and Y are quasi-positive solutions of the following Riccati equation.

[0077]

(A-B ₂ D ₁₂ ^T C ₁ ) ^T X + X (A-B _{2
^{D 12 T C 1) + X}} (B 1 B 1 T / γ 2 -B 2 B 2 T) X
+ C ₁ ^T (I-D ₁₂ D ₁₂ ^T ) C _K = 0 (A-B ₁ D ₂₁ ^T C ₂ ) Y + Y (A-B ₁ D ₂₁ ^T C ₂ )
^{_{T + Y (C 1 T C}} 1 / γ 2 -C 2 T C 2) Y + B 1 (I
-D ₂₁ ^T D ₂₁ ) B ₁ ^T = 0

I is an appropriate unit matrix, and γ is a positive constant satisfying the following eigenvalue condition.

[0079]

[Formula 19] λ _MAX (XY) <γ ²

As described above, according to the present invention, the autopilot 12 is converted into the specification that quantifies the problems of the conventional automatic steering device, and the H∞ control is applied to the generalized control object 100 including the specification and the control object 14. Apply. As a result, the stability of the automatic steering system with respect to the disturbance d is guaranteed, and it is possible to eliminate the occurrence of unnecessary operation of the steering device 16 due to the frequency characteristic of the disturbance d.

[0081]

According to the present invention, the auto pilot 12
In the above, since the non-linear element 12-2 as in the conventional example, that is, the weather adjusting mechanism is unnecessary, there is an advantage that it is not necessary to perform the adjusting work accompanying it.

According to the present invention, since the autopilot 12 is set by applying it to the H∞ control, the stability of the closed loop system of the automatic steering system is not positively taken into consideration and the given or desired specifications are obtained. Is taken in as a weighting function, and there is an advantage that frequency shaping can be performed.

According to the present invention, since the autopilot 12 does not include the non-linear element 12-2, there is an advantage that the mounting cost and the adjustment cost are reduced as compared with the conventional autopilot 12.

[Brief description of drawings]

FIG. 1 is a block diagram showing an automatic steering system according to the present invention.

FIG. 2 is a block diagram when an automatic steering system according to the present invention is applied to H∞ control.

FIG. 3 is a Bode plot of a second weighting function according to the present invention.

FIG. 4 is a Bode plot of a first weighting function according to the present invention.

FIG. 5 is a block diagram showing a conventional automatic steering system.

FIG. 6 is a diagram showing a configuration of a conventional automatic steering device (auto pilot).

[Explanation of symbols]

 11 Adder 12 Automatic steering device (autopilot) 13 Adder 14 Control object 14-1 Hull 14-2 Heading direction detector 15 Adder 16 Steering machine 17, 18 Weighting function

Claims (6)

[Claims] 1. An automatic steering apparatus for a ship, which is configured to control a closed-loop automatic steering apparatus that inputs a signal indicating a deviation of a bow direction with respect to a set course and outputs a command steering angle, to be controlled. An automatic steering apparatus for a ship, characterized in that the generalized controlled object as above and the above automatic steering apparatus are combined to result in an H∞ control problem. 2. The automatic steering system for a ship according to claim 1, wherein the generalized control target has a frequency characteristic such that an unnecessary operation due to a disturbance is not applied to the automatic steering system. And the second weighting function having a frequency characteristic such that a stationary error caused by a disturbance in the low frequency range does not remain in the deviation, and the control target are integrated. Characteristic automatic steering device for ships. 3. The marine automatic steering apparatus according to claim 2, wherein the generalized control target is further provided with a steering angle obtained by subtracting an angle conversion value of the disturbance from a command steering angle which is an output signal of the automatic steering apparatus. An automatic steering device for a ship, comprising an adder for determining 4. The marine automatic steering apparatus according to claim 2 or 3, wherein the transfer function from the disturbance to the output signal of the automatic steering apparatus is less than or equal to the reciprocal of the first weighting function. Automatic steering device for ships. 5. The automatic marine vessel steering system according to claim 2, 3 or 4, wherein the transfer function from the disturbance to the input signal of the automatic steering system is less than or equal to the reciprocal of the second weighting function. An automatic steering device for ships. 6. The automatic marine vessel steering system according to claim 2, 3, 4 or 5, wherein the control target is a vessel body and a heading detector which are integrally formed. Steering device.