CN108062023B - Gravity-center-based ROV thrust distribution method - Google Patents

Abstract

The invention relates to a center-of-gravity-based ROV thrust distribution method, comprising the following steps: collecting a motion operation excitation signal of a joystick through an on-site acquisition module, or obtaining a motion excitation signal through automatic motion control; substituting the motion excitation signal into a preliminary thrust distribution formula, Obtain the thrust control signal of each thruster and transmit it to the control circuit of each thruster; adjust the center of gravity coefficient in the thrust distribution formula to keep the forward, backward and lateral movement as straight as possible; fit the obtained two sets of center of gravity coefficients, Obtain the center of gravity coefficient that can be shared during advance, retreat and side shift; the fitting formula and the preliminary thrust distribution formula together form the thrust distribution formula of the ROV. The invention is simple and practical, does not significantly increase the complexity of the thrust distribution algorithm, can improve the motion performance of the ROV, and at the same time allows slight deviation of the center of gravity in the design, thereby reducing the design difficulty of the ROV.

Description

A method of ROV thrust distribution based on the center of gravity

technical field

The invention relates to the technical field of ROV navigation motion control, in particular to an ROV thrust distribution algorithm based on the center of gravity.

Background technique

With the increasing demand of human beings for ocean development, ROV remote-operated submersible, as an underwater equipment that can complete operations such as observation, photography, salvage and construction, has a very broad range in military, civilian and scientific research fields. application prospects. The quality of the thrust distribution method determines whether the ROV can complete the navigation motion control well, which is one of the key technologies for the ROV to successfully complete the operation.

The thrust distribution method is usually to calculate the thrust setting signal of each thruster according to the motion manipulation excitation signal calculated from the joystick or automatic control, and then send it to the control circuit of the thruster to drive each thruster to output the corresponding thrust. There are 6 motion control excitation signals, including advance and retreat, side shift, steering, snorkeling, heeling, and trim.

The conventional thrust distribution algorithm usually ignores the influence of the slight deviation of the center of gravity on the motion control performance, resulting in a large deviation in the heading when only maneuvering forward, backward or sideways in clean water, that is, the ROV will not drive in a straight line. , it can be seen that the conventional thrust distribution algorithm cannot effectively suppress the interference caused by the offset of the center of gravity.

Therefore, researching a simple and practical thrust distribution method, reducing the interference of the center of gravity offset on the ROV, and improving the performance of motion control, especially automatic motion control, is a practical problem that needs to be solved in the current ROV motion control.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the traditional ROV thrust distribution method, the present invention provides a simple and practical thrust distribution method, which can effectively reduce the interference caused by the offset of the center of gravity, improve the performance of ROV motion control and reduce the operation intensity of operators. At the same time, compared with the traditional thrust distribution method, the increased computational complexity is also negligible.

The technical scheme that the present invention adopts for realizing the above-mentioned purpose is:

A method of ROV thrust distribution based on the center of gravity, comprising the following steps:

Collect the motion operation excitation signal and substitute its value into the preliminary thrust distribution formula to obtain the thrust of each thruster;

Fit the center of gravity coefficient of ROV forward and backward and the center of gravity coefficient of side shift to obtain the common center of gravity coefficient;

Re-substitute the shared center of gravity coefficient into the preliminary thrust distribution formula to obtain the thrust of each thruster, and control the thrust output of each thruster.

The preliminary thrust distribution formula is:

F1=C _x F _x +C _y F _y +M _z

F2=F _x -C _y F _y -M _z

F3=C _x F _x -F _y +M _z

F4 ₌ Fx+ _Fy - _Mz

l1至l4分别为水平矢量布置的四台推进器在ROV旋转时的力臂，F1至F7分别为水平左前、水平右前、水平左后、水平右后、垂直左前、垂直右前、垂直后位置的推进器产生的推力，F_x、F_y、F_z分别为ROV在x方向、y方向、z方向上的推力运动操作激励信号，M_x、M_y、M_z分别为绕ROV x轴、y轴、z轴的力矩运动操作激励信号，l则为垂直后位置的推进器与垂直左前或垂直右前推进器在纵倾方向上的力臂比。where: C _x and C _y are the centroid coefficients,

l1 to l4 are the lever arms of the four propellers arranged in the horizontal vector when the ROV rotates, and F1 to F7 are the horizontal left front, horizontal right front, horizontal left rear, horizontal right rear, vertical left front, vertical right front, and vertical rear positions respectively. The thrust generated by the thruster, F _x , F _y , and F _z are the thrust motion operation excitation signals of the ROV in the x direction, y direction, and z direction, respectively, M _x , My _y , and M _z are about the ROV x axis, y The torque motion operation excitation signal of the axis and z-axis, l is the ratio of the thruster in the vertical rear position to the vertical left front or vertical right front thruster in the pitch direction.

After obtaining the thrust of each thruster, determine the center of gravity coefficient:

C _x >1, C _y >1; the center of gravity is biased to the left front;

C _x <1, C _y >1; the center of gravity is shifted to the right front;

C _x >1, C _y <1; the center of gravity is shifted to the left rear;

C _x <1, C _y <1; the center of gravity is shifted to the right rear.

The fit is achieved by the following formula:

Among them, C _x and C _y are the center of gravity coefficients; C _x1 , C _y1 are the center-of-gravity coefficients when the forward and backward motion moves in a straight line, C _x2 , C _y2 are the center-of-gravity coefficients when the side-shift motion moves along a straight line; F _x , F _y are ROVs respectively Thrust motion in the x-direction, y-direction operates the excitation signal.

The present invention has the following beneficial effects and advantages:

1. The thrust distribution method of the present invention, by directly adjusting the center of gravity coefficient, can effectively reduce the interference of the small deviation of the center of gravity on the ROV motion performance, and in the absence of water flow disturbance, the ROV can be kept approximately in a straight line in the horizontal plane.

2. The thrust distribution method of the present invention can be used in combination with a buoyancy trim block. After continuously adjusting the position of the trim block and adjusting the center of gravity coefficient, the center of gravity of the ROV is finally adjusted to the design center of gravity.

3. The thrust distribution method of the present invention allows slight deviation of the center of gravity in the design, which reduces the design difficulty of the ROV body.

4. The thrust distribution method of the present invention only adds two coefficients (Cx, Cy) and a fitting formula on the basis of the traditional thrust distribution method, without increasing the complexity of the distribution method, and debugging is also simple and easy.

Description of drawings

Figure 1 is the layout of the ROV thruster;

Fig. 2 is the method flow chart of the present invention;

FIG. 3 is a flow chart of the execution of the thrust distribution program.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

A method of ROV thrust distribution based on the center of gravity, including the following steps:

Step 1: Collect the movement operation excitation signals of the joystick, such as advancing and retreating, lateral movement, steering, snorkeling, etc., through the on-site acquisition module, or obtain movement excitation signals through automatic depth setting, automatic orientation, automatic height setting, and automatic positioning, etc.;

Step 2: Substitute the collected motion excitation signal into the preliminary thrust distribution formula, obtain the thrust control signal of each thruster, and transmit the control signal to the thruster control circuit through the on-site acquisition module and peripheral drive circuit to adjust the thrust of each thruster output.

Step 3: Adjust the center of gravity coefficients (Cx, Cy) in the preliminary thrust distribution formula according to the ROV's advance, retreat and side shift, respectively, to keep the advance, retreat and side shift as straight as possible.

Step 4: Fit the two sets of gravity center coefficients obtained by advancing, retreating and sideways, and obtain the center of gravity coefficients that can be shared by advancing, retreating and sideways.

Step 5: The fitting formula and the preliminary thrust distribution formula together form the thrust distribution formula of the ROV.

The ROV body is approximately symmetrical left and right and front and rear, and the arrangement of its thrusters is: 4 thrusters are arranged in the horizontal direction, forming a rhombus, and are respectively installed on the left front, right front, left rear, and right rear positions of the ROV frame. The longitudinal axis is arranged at an angle of 45 degrees; 3 thrusters are arranged vertically for the submersible motion of the ROV, of which the front two are distributed on the left and right sides, and the rear one is arranged in the center.

The preliminary thrust distribution formula of the ROV is:

F1=C _x F _x +C _y F _y +M _z

F2=F _x -C _y F _y -M _z

F3=C _x F _x -F _y +M _z

F4 ₌ Fx+ _Fy - _Mz

l1至l4分别为水平矢量布置的四台推进器在ROV旋转时的力臂，F1至F7分别为水平左前、水平右前、水平左后、水平右后、垂直左前、垂直右前、垂直后等推进器产生的推力，F_x、F_y、F_z分别为ROV x方向、y方向、z方向上的推力运动操纵激励信号，M_x、M_y、M_z分别为绕ROV x轴、y轴、z轴的力矩运动操纵激励信号，l则为垂直后和垂直左前(右前)在纵倾方向上的力臂比。where: C _x and C _y are the centroid coefficients,

l1 to l4 are the lever arms of the four propellers arranged in the horizontal vector when the ROV rotates, F1 to F7 are the horizontal left front, horizontal right front, horizontal left rear, horizontal right rear, vertical left front, vertical right front, vertical rear, etc. The thrust generated by the device, F _x , F _y , and F _z are the thrust motion manipulation excitation signals in the x, y, and z directions of the ROV, respectively, and M _x , _My , and M _z are the x-axis, y-axis, The moment motion of the z-axis manipulates the excitation signal, and l is the ratio of the force arm to the vertical rear and vertical left front (right front) in the pitch direction.

The ROV center of gravity coefficients Cx and Cy are about 1, and the adjustment rules for the center of gravity coefficient during initial commissioning are as follows:

When the center of gravity is biased to the left front, C _x >1, C _y >1;

When the center of gravity is shifted to the right front, C _x <1, C _y >1;

When the center of gravity is left behind, C _x >1, C _y <1;

When the center of gravity is shifted to the right, C _x <1, C _y <1;

The fitting formulas of the two groups of gravity center coefficients of the advance, retreat and side shift are:

Among them, C _x1 , C _y1 are the center of gravity coefficients when the forward and backward motion is in a straight line, and C _x2 and C _y2 are the center of gravity coefficients when the lateral movement moves in a straight line.

The propeller arrangement situation of ROV of the present invention is as shown in Figure 1, and the arrangement of propellers is as follows: 4 propellers are arranged in the horizontal direction, forming a diamond shape, and are respectively installed on the left front, right front, left rear, and right rear positions of the ROV frame, It is arranged at an angle of 45 degrees to the longitudinal axis of the ROV, and is responsible for the movement of the ROV in three degrees of freedom: forward and backward, lateral movement and steering; three propellers are arranged in the vertical direction, of which the front two are distributed on the left and right sides, and the rear one is arranged In the center, it is responsible for the movements of the ROV in three degrees of freedom: snorkeling, pitching and heeling.

The flow chart of the inventive method is shown in Figure 2:

Firstly, according to the layout of ROV thrusters, establish the thrust and moment equations of ROV, solve and simplify them, and then abstract the parameters related to the offset of the center of gravity into two coefficients, and obtain the preliminary thrust distribution equation as follows:

F1=C _x F _x +C _y F _y +M _z

F2=F _x -C _y F _y -M _z

F3=C _x F _x -F _y +M _z

F4 ₌ Fx+ _Fy - _Mz

l1至l4分别为水平矢量布置的四台推进器在ROV旋转时的力臂，F1至F7分别为水平左前、水平右前、水平左后、水平右后、垂直左前、垂直右前、垂直后等推进器产生的推力，F_x、F_y、F_z分别为ROVx方向、y方向、z方向上的推力运动操纵信号，M_x、M_y、M_z分别为绕ROV x轴、y轴、z轴的力矩运动操纵信号，l则为垂直后和垂直左前(右前)在纵倾方向上的力臂比。Where: C _x and C _y are the center of gravity coefficients, and the calculation formula is:

l1 to l4 are the lever arms of the four propellers arranged in the horizontal vector when the ROV rotates, F1 to F7 are the horizontal left front, horizontal right front, horizontal left rear, horizontal right rear, vertical left front, vertical right front, vertical rear, etc. The thrust generated by the device, F _x , F _y , and F _z are the thrust motion manipulation signals in the ROV _x direction, _y direction, and _z direction, respectively. is the moment motion control signal, and l is the arm ratio of vertical rear and vertical left front (right front) in the pitch direction.

Using the obtained calculation formula of the center of gravity coefficient, the offset direction of the center of gravity of the ROV can be judged, and the corresponding relationship is as follows:

When the center of gravity is biased to the left front, C _x >1, C _y >1;

When the center of gravity is shifted to the right front, C _x <1, C _y >1;

When the center of gravity is left behind, C _x >1, C _y <1;

When the center of gravity is shifted to the right, C _x <1, C _y <1;

The preliminary thrust distribution equation is programmed into code, embedded in the ROV control program, and the pool thrust distribution debugging is carried out. Since the center of gravity coefficient only affects the ROV's two motion controls, forward, backward and sideways, it is only necessary to obtain the actual value of the center of gravity coefficient when the two motions are approximately straight lines, and fit these two sets of coefficients to obtain the final center of gravity coefficient. The fitting formula is as follows:

Among them, C _x1 , C _y1 are the center of gravity coefficients when the forward and backward motion is in a straight line, and C _x2 and C _y2 are the center of gravity coefficients when the lateral movement moves in a straight line.

The fitting formula and the preliminary thrust distribution equation together form the final thrust distribution equation.

The execution flow chart of the thrust distribution program of the method of the present invention is shown in Figure 3. The program first obtains the motion excitation signal from the operating lever or the output of the automatic motion control, and then performs the fitting of the center of gravity coefficient according to the motion excitation signal of the advance, retreat and side shift, Then, the fitted center of gravity system is substituted into the preliminary thrust distribution equation to obtain the thrust control quantities of each thruster, and finally the obtained control quantities are transferred to the control mechanisms of each thruster to realize the motion control of the ROV.

The above ROV is only the best implementation object of the present invention, and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the present invention. within the scope of protection of the invention.

Claims (3)

1. a ROV thrust distribution method based on the center of gravity, is characterized in that comprising the following steps: Collect the motion operation excitation signal and substitute its value into the preliminary thrust distribution formula to obtain the thrust of each thruster; Fit the center of gravity coefficient of ROV forward and backward and the center of gravity coefficient of side shift to obtain the common center of gravity coefficient; Re-substitute the shared center of gravity coefficient into the preliminary thrust distribution formula to obtain the thrust of each thruster, and control the thrust output of each thruster; The preliminary thrust distribution formula is: F1=C _x F _x +C _y F _y +M _z F2=F _x -C _y F _y -M _z F3=C _x F _x -F _y +M _z F4 ₌ Fx+ _Fy - _Mz

where: C _x and C _y are the centroid coefficients,

l1 to l4 are the lever arms of the four propellers arranged in the horizontal vector when the ROV rotates, and F1 to F7 are the horizontal left front, horizontal right front, horizontal left rear, horizontal right rear, vertical left front, vertical right front, and vertical rear positions respectively. The thrust generated by the thruster, F _x , F _y , and F _z are the thrust motion operation excitation signals of the ROV in the x direction, y direction, and z direction, respectively, M _x , My _y , and M _z are about the ROV x axis, y The torque motion operation excitation signal of the axis and z-axis, l is the ratio of the thruster in the vertical rear position to the vertical left front or vertical right front thruster in the pitch direction. 2. the ROV thrust distribution method based on the center of gravity according to claim 1 is characterized in that after obtaining the thrust of each propeller, judge the center of gravity coefficient: C _x >1, C _y >1; the center of gravity is biased to the left front; C _x <1, C _y >1; the center of gravity is shifted to the right front; C _x >1, C _y <1; the center of gravity is shifted to the left rear; C _x <1, C _y <1; the center of gravity is shifted to the right rear. 3. The ROV thrust distribution method based on the center of gravity according to claim 1 is characterized in that the fitting is realized by the following formula:

Among them, C _x and C _y are the center of gravity coefficients; C _x1 , C _y1 are the center-of-gravity coefficients when the forward and backward motion moves in a straight line, C _x2 , C _y2 are the center-of-gravity coefficients when the side-shift motion moves along a straight line; F _x , F _y are ROVs respectively Thrust motion in the x-direction, y-direction operates the excitation signal.

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