JP3385474B2 - Measurement system of three components of wave drift force and six components of unconstrained oscillating displacement of floating body in waves - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for measuring wave drift force and unrestrained wobble displacement of a floating body in waves.

[0002]

2. Description of the Related Art An extremely low frequency component of a force or moment applied to a floating body by a wave is called a wave drift force, and is used for predicting the drifting direction of a wrecked ship. There are three components: longitudinal force, lateral force, and turning moment. This wave drift force changes depending on whether the floating body is shaking in the encounter cycle with the wave,
When measuring the drift force of a wave acting on an actual floating body by experiment, it is necessary to measure the fluctuation of the encounter period with the wave freely. As for the up-down, horizontal and vertical swaying of the floating body, it is possible to freely move the floating body because there is a restoring force. Since there is no restoring force, the movement of the floating body cannot be completely freed for these three components. This is because the floating body drifts due to the wave drift force, and in this case, the force cannot be measured.

Therefore, in order to measure the three components of the wave drift force in the set towed state or in the stopped state, a force or moment (hereinafter referred to as the anti-wave Called drift force.)
In addition, during towing, in addition to this, the force or moment necessary for towing in plain water is applied to the floating body to maintain the average position and attitude of the floating body with respect to the device in a neutral state, and It is necessary to measure the force or moment by freeing the sway of the encounter cycle with. However, since the anti-wave drift force to be given is an unknown amount to be measured in this case, it has been impossible to measure the three components of the wave drift force without restraining the motion of the floating body. It had been.

At present, the following means are known as means for measuring the three components of the wave drift force without restraining the fluctuation of the encounter period with the wave as much as possible. (1) For all front-back sway, side-to-side sway, and bow sway, adjust the average position and attitude with weak springs and weights. (See FIG. 1) In FIG. 1, reference numeral 21 is a heaving rod, 22 is a surging carriage, 23 to 25 are pulleys, 26 and 27 are soft springs, 28 is a weight,
Reference numeral 29 denotes a swaying carriage, 30 denotes a gimbal for detecting a wave drift force, and 31 denotes a gimbal for detecting a roll probe and a wave drift force. (2) For forward and backward sway and left and right sway, the average position is adjusted with a weak spring and a weight, and for bow sway, the bow direction is adjusted with a strong spring. (3) A constant torque motor has a role of a spring and a weight for all of front-back sway, left-right sway, and bow sway.
Adjust the average position and posture of each. (See FIG. 2) In FIG. 2, reference numeral 41 is a constant torque motor for surge, 42 is a constant torque motor for sway, 43 is a constant torque motor for yaw, 44 is a three-component force meter, and 45 is a model ship as a floating body. Indicates. (4) The front and rear sway and the left and right sway are adjusted by adjusting the average position with a weak spring and a weight, and adjusting the bow sway by steering.

In all of the above-mentioned means, the common use of springs for at least back-and-forth and left-right swaying is that the generation of the anti-wave drifting force corresponding to the unknown wave-driving force is caused by the weight in the rough part. The fine adjustment part was intended to be realized by displacement of the floating body by a spring.

The means (1) is intended to realize this idea as it is. However, regarding front-back swaying and side-to-side swaying, the meeting angle between the wave and the floating body does not change even if the balance position of the wave drifting force and the counter wave drifting force changes. If you do not properly, the meeting angle between the wave and the floating body will change,
Not only cannot the set experimental conditions be realized, but also slight deviations appear as changes in longitudinal force and lateral force, which makes experimental measurement extremely difficult. For this reason, it is very difficult to adjust the means (1) for adjusting the swinging of the bow with a weak spring and a weight, and it is almost impossible to adjust especially when there is a forward speed. For this reason, the means (2) uses a strong spring only for the swinging of the bow.

Further, the means (3) makes it possible to easily and continuously adjust the spring and the weight by an electric signal. Basically, the means (1) or (2) is used. It is based on the same idea, and when a human directly adjusts it, it is unavoidable to use a strong spring for swaying the bow when there is a forward speed. It is possible to adjust the signal to the constant torque motor by using an appropriate feedback system, but as long as a spring system is used,
In principle, it is impossible to find the equilibrium point unless the deviation from the target position occurs. Further, in the means of (3), since the constant torque motor is placed on the moving portion and the floating body is integrated with the floating body, the additional mass influences the motion of the floating body. The degree of exertion is greater than that of the means (1) or (2).
In this way, using a strong spring or using a constant torque motor is nothing but restraining the motion of the floating body to some extent. Therefore, it must be said that this immediately affects the measured value of the wave drift force. Also, as long as a spring system is used, it is impossible in principle to realize the towed state or the stopped state of the floating body as set.

By the way, only the means of (4) is realized by adjusting the swing of the bow by means of a rudder, and as far as the swing of the bow is concerned, the degree of restraining the swing with the wave by a strong spring is small. It is considered to be superior to the methods up to (3). However, consider that steering requires lateral and lateral sway, and the measured force data must be analyzed in consideration of the longitudinal force, lateral force, and turning moment generated by the rudder. Therefore, the method (4) is not necessarily superior to the methods (1) to (3), and it is considered that each of these current measuring means has serious drawbacks.

[0009]

SUMMARY OF THE INVENTION The present invention uses a servomotor in place of the constant torque motor in the conventional measuring system, so that the average position of the floating body in the wave with respect to the device in the set towed state or the stopped state can be improved. The wave drift force of the floating body in the waves was determined by maintaining the posture in a neutral state, freeing the fluctuation of the encounter period with the wave, and accurately measuring the wave drift force and the unconstrained shaking displacement. An object of the present invention is to provide a measurement system for 6 components of restraint shaking displacement.

[0010]

In order to solve the above-mentioned problems, the measuring system for wave drift force 3 component and unconstrained wobbling displacement 6 component of a floating body in waves of the present invention is a mechanism connected to a floating body in waves. And a control unit for controlling the mechanical unit, wherein the mechanical unit connects the floating body by a connecting means that does not restrain movement of the floating body in six degrees of freedom in waves.
The displacement body is provided with six displacement gauges for measuring six components of motion displacement of the floating body, and a three-component force meter for measuring longitudinal force, lateral force, and turning moment acting on the floating body at the connecting portion to the floating body by the connecting means. And controls the front-back sway, left-right sway, and bow sway of the floating body 3
It is equipped with a single servo motor, and the control unit is configured to measure the displacement of the floating body in the longitudinal direction, lateral displacement, and bow displacement measured by the displacement gauge, and the longitudinal force and lateral force measured by the three-component force meter. And the respective measured values of the turning moment are used to eliminate the effects of additional inertial force of the device in the set towed state or stopped state via the servo motor, and It is characterized by being provided with a control system capable of controlling so as to maintain an average position and posture with respect to the apparatus in a neutral state.

Further, in the measuring system of the wave drift force 3 component and the unconstrained wobbling displacement 6 component of the floating body in the wave according to the present invention, the above control system makes the displacement x (t), and the measured force or moment F ( t), the force or moment F * (t) as the target value is given by the following equations [Equation 1], [Equation 2],
[Equation 3], [Equation 4] and [Equation 5]
It is characterized in that the servo motor is controlled so that the displacement x (t) is changed so that the equation [6] is satisfied.

[Number 1] _{^{F * (t) = F S}} * (t) + F V * (t)

[Equation 2]

[Equation 3]

[Equation 4]

[Equation 5]

[Equation 6]

In the above-described measurement system for wave drift force 3 components and unconstrained wobbling displacement 6 components of the floating body in the wave of the present invention, the average position and attitude of the floating body including the heading in the set towed state or stopped state. Can be retained as set. At this time, since this system does not have a spring system, the force or moment equivalent to a spring is not added unlike the conventional device, and the movement of the additional mass of the moving part of the device is not generated. Since the influence on the is removed by the servo control, the measurement is performed without restraining the fluctuation of the encounter period with the wave. And
In the towed state, subtracting the value of the force or moment required for towing in plain water from the final measured value F (t) of the force or moment gives the wave drift force to be measured, and in the stopped state, the final wave drift force is obtained. The measured value F (t) of the force or moment is the wave drift force itself to be measured. At the same time, six fluctuations of the meeting period with the unrestrained wave are also measured.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to the drawings, an explanation will be given of a measuring system of wave drift force 3 components and unconstrained shaking displacement 6 components of a floating body in waves as an embodiment of the present invention. FIG. And FIG. 4 is a signal flow chart thereof.

As shown in FIG. 3, in the mechanical section K of the present system installed in the towing vehicle, the towing vehicle serves as a floating body which is towed in waves through the mechanical section K or is in a stopped state. Model ship 1 has roll R and pitch P
Is connected to a rotation mechanism 2 which is free, and the rotation mechanism 2 is connected to a column 4 of a moving unit via a three-component force meter 3. The columns 4 and 4a have a structure in which the vertical swing of the model ship 1 is not restrained by the wheels incorporated in the vertical swing guide 4b.

Wheels 5 are provided at the portions supporting the columns 4, whereby the model ship 1 can be rocked back and forth.
Further, a servo motor 6 for swinging back and forth is mounted on a portion of the swinging moving portion that supports the wheels 5, and the swinging moving portion can be controlled via a wire 7.

The portion supporting the swaying / moving portion further has wheels 8 which allow the model ship 1 to sway to the left and right. A left-right swaying servo motor 9 is installed in a portion that supports the left-right swaying moving section, and the left-right swaying moving section can be controlled via a wire 10.

A column 4 which allows the model vessel 1 to swing is passed through a bowing guide 4a which allows the model vessel 1 to freely swing up and down. The column 4 has a connecting mechanism 1 at the upper part of the column.
It is connected to the servomotor 13 via 1, 12. In addition, six displacement gauges 16 (see FIG. 4) for measuring the six motion displacement components of the model ship 1 (forward and backward sway, left and right sway, bow sway, vertical sway, horizontal sway and vertical sway) are provided.

The three-component force meter 3 measures the three components of the longitudinal force, the lateral force, and the turning moment. The measurement signals are recorded as measurement data, and as shown in FIG. Sent. Further, the servo motors 6, 9 and 13 related to the front and rear sway, the left and right sway and the bow sway receive the signals from the control unit 14 to control the respective movement displacements. In addition, a clamp device 15 for restraining the model ship 1 is provided until the start of measurement and after the end of measurement.

Next, referring to FIG. 4, the control unit 14 of the present system.
A mode of control in the above will be described. Assuming that time is t, measured displacement is x (t), and measured force or moment is F (t), the target force or moment F * (t) is calculated by the formula [1]. To be done.

[Number 1] _{^{F * (t) = F S}} * (t) + F V * (t) here, t: time

F _S * (t) is calculated by the equation [2].

[Equation 2]

[Equation 4] Here, it is assumed that T is the encounter period with the wave in the regular wave, and the encounter period of the main wave component in the irregular wave. F _V * (t) is calculated by the equation [3].

[Equation 3] Where K ₂ and K ₃ are control coefficients that change depending on the shape and size of the floating body. Similarly, it is calculated by the formula [5].

[Equation 5]

The servo motor controls the displacement x (t) so that the equation [6] is satisfied.

## EQU6 ## F (t) -F ^* (t) = 0

Next, the analysis of the measurement data and the initial value of the control target value will be explained. Although the final measurement data is the displacement data for the 6 motion displacement components as they are,
Regarding the wave drift force, the obtained measurement data consists of components such as in [Equation 7].

## _EQU00007 ## F (t) = F _calm + F _wave Here, F _calm represents the towing force required when towing in plain water at the same average position as in waves, and F _wave represents the wave drift force. Since F _wave is the final data to be measured, it is necessary to subtract F _calm from the measured value. Therefore, it is necessary to tow through the plain water and measure F _calm in advance.

In this way, the wave drift force is calculated by the equation [8].

F _wave = F (t) −F _calm Here, although F _wave is formally a function of time, when control is performed by this system, F (t) ≈con
st. Therefore, in practice, the average value of [Equation 8] is taken as the final wave drift force data.

As a special case, when measuring the wave drift force at stop, the towing force or moment is zero,
That is, since F _calm = 0, the wave drift force can be immediately obtained by averaging the measured force or moment data. F * which is the initial value of servo motor control
For (0), F _calm , which is indispensable for the calculation of wave drift force data, is used to accelerate the convergence of control.
* (0) = F _calm .

As described above, according to the present system, the average position and attitude of the model ship 1 with respect to the device including the heading can be maintained in the neutral state in the set towed state or the stopped state. At this time, since this system does not have a spring system, a force or moment equivalent to a spring is not added unlike the conventional device, and the influence of the additional mass of the moving part of the device on the movement. Since it is also removed by servo control, measurement is performed without restraining the fluctuation of the encounter period with the wave.

Then, by subtracting the value of the force or moment required for towing in plain water from the final measured value of the force or moment, the wave drift force data to be measured can be obtained. At the same time, the six fluctuations of the meeting period with the unconstrained wave are also measured.

By the control according to the equation [1], while maintaining the average position and attitude of the model ship 1 in the set towed state or in the stopped state, the average position and posture of the model ship 1 with respect to the device for swinging back and forth, left and right, and the bow are kept neutral. In addition, the influence of the inertial force of the additional mass such as the moving part and the servo motor on the fluctuation of the encounter cycle with the wave of the model ship 1 is affected, while the fluctuation of the encounter cycle with the wave of the model ship 1 is affected. In the case of towing, the force and moment required for towing as set, that is, the force and moment necessary for towing in plain water and the sum of the wave drift force and In the stopped state, a force and a moment corresponding to the wave drift force can be generated. Therefore, the wave period of 6 degrees of freedom can be obtained without restraining the fluctuation of the encounter period with the wave of the model ship 1. It can be performed the measurement of the wave drift force while measuring the upset can be explained as follows.

Considering the converged state of the equation (1), the following equations (9), (10) and (11) are obtained.

## EQU00009 ## F ^* (t) = F ^* (t-.DELTA.t) = F ^* _const

[Equation 10]

[Equation 11]

The formula [9] shows that the force applied to the model ship 1 has a certain constant value, and the formulas [10] and [11] are the average values of the model ship 1, respectively. It shows zero displacement and velocity. It should be noted here that the meaning of [Equation 9] is that the servomotor does not generate a constant force, but only the model ship 1
That is, the force or moment applied to the unit has a constant value as a result of the control.

The fact that the average displacement of the model ship 1 is zero, that is, the average position and attitude with respect to the device is in the neutral state, is immediately towed as set by the model ship 1, Or, on average, it is in a stopped state. Further, the fact that the model ship 1 is applied with a certain force or moment, that is, the applied force or moment does not have a fluctuation component means that the moving part additionally connected to the model ship 1 is This means that the effect of additional inertial force due to the mass of the servo motors 6, 9, 13 has been eliminated. Because
This is because the influence of these additional masses appears only as a fluctuation component due to the acceleration associated with the fluctuation of the encounter period with the waves of the model ship 1.

Furthermore, the force and moment required for towing is the sum of the force and moment required for towing in plain water and the wave drift force, and if a force or moment component other than this is present. Obviously, the average position and attitude of the model ship 1 cannot be maintained as set, so that the forces and moments applied to the model ship 1 are exactly the forces and moments necessary for towing or stopping, that is, towing. In the case of, it is the sum of the force and moment necessary to tow in plain water and the wave drift force,
In the case of stop, it means the wave drift force itself.
The force and moment required only for this towing do not affect the fluctuation of the encounter period with the waves of the model ship 1.

As a result of the above, this system can
It can be understood that this is a system that can measure the displacement without constraining the fluctuation of the encounter period with the wave of freedom and at the same time measure the wave drift force. The servomotors 6, 9 and 13 in the above-described embodiment are positioning means for realizing displacement control, and the concept of the servomotor in the present invention includes positioning means using a stepping motor.

[0033]

As described above in detail, the following effects can be obtained by the measuring system of the wave drift force 3 component and the unconstrained wobbling displacement 6 component of the floating body according to the present invention. (1) In the set towed state or the stopped state, the average position and attitude of the floating body including the heading can be maintained as set. At this time, since this system does not have a spring system, a force or moment equivalent to a spring is not added unlike the conventional device, and the movement of the additional mass of the moving part of the device is not affected. Since the influence is also removed by the servo control, the measurement is performed without restraining the fluctuation of the encounter period with the wave. Then, in the towing state, by subtracting the force or moment value required for towing in plain water from the final measured value F (t) of the force or moment, the wave drift force to be measured can be obtained, and in the stopped state The final force or moment measurement value F (t) is the wave drift force itself to be measured. (2) At the same time, the six fluctuations of the meeting period with the unrestrained wave are also measured.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a conventional wave drift force measuring device using a spring and a weight.

FIG. 2 is a perspective view schematically showing a conventional wave drift force measuring device using a constant torque motor.

FIG. 3 is a perspective view schematically showing a mechanical unit in a measurement system for measuring a wave drift force of 3 components and an unconstrained shaking displacement of 6 components of a floating body in a wave as one embodiment of the present invention.

4 is a signal flow diagram illustrating aspects of control in the system of FIG.

[Explanation of symbols]

1 Model ship (floating body) 2 rotation mechanism 3 3 component force meter 4 props 5 wheels 6 Servo motor 7 wires 8 wheels 9 Servo motor 10 wires 11 Connection mechanism 12 Connection mechanism 13 Servo motor 14 Control unit 15 Clamp device 16 displacement gauge K mechanism P vertical shaking R roll

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B63B 39/14 G01B 21/00 G01L 5/16

Claims (2)

(57) [Claims] 1. A mechanism section connected to a floating body in waves and a control section for controlling the mechanism section, wherein the mechanism section comprises:
The floating body is connected by a connecting means that does not restrain the movement of the floating body in the waves of 6 degrees of freedom, and the movement displacement 6 of the floating body is connected.
In addition to six displacement gauges for measuring each component, a three-component force meter for measuring the longitudinal force, the lateral force, and the turning moment acting on the floating body is provided at the connecting portion to the floating body by the connecting means, and It is equipped with three servomotors for controlling the front-back sway, left-right sway, and bow sway of the floating body, and the controller controls the displacements of the floating body such as front-back sway, left-right sway, and bow sway measured by the displacement meter. And the measured values of the longitudinal force, the lateral force, and the turning moment measured by the above three-component force meter are used to eliminate the influence of the additional inertial force of the device in the set towing state or stop state via the servo motor. However, a control system is provided that can control so as to keep the average position and attitude of the floating body with respect to the device for swinging back and forth, swinging sideways and swinging the bow in a neutral state. Wherein the are, wave drift force ternary Waves floating and unconstrained upset displacement six components of the measurement system. 2. The measurement system for measuring the wave drift force of a floating body in a wave according to claim 1 having three components and the unconstrained wobble displacement of six components, wherein the control system measures the displacement by x (t), a measured force or When the moment is F (t), the force or moment F * (t) as the target value is given by the formula [1],
[Equation 2], [Equation 3], [Equation 4] and [Equation 5] are used to control the displacement x (t) of the servo motor so that the equation [Equation 6] is satisfied. A system for measuring the wave drift force 3 component and the unconstrained shaking displacement 6 component of a floating body in waves. [Number 1] _{^{F * (t) = F S}} * (t) + F V * (t) [number 2] [Equation 3] [Equation 4] [Equation 5] [Equation 6]