JPS6388603A - Traveling control method for marine robot - Google Patents

Abstract

PURPOSE:To attain the holding of a stable position and the traveling even when a robot changes its posture in the work environment having a tide, etc., by outputting a vector sum of a thrust to achieve a target and a thrust to cancel a force to operate to the robot as the thrust of the robot. CONSTITUTION:The thrust due to a control gain to minimize a secondary performance evaluation function to vary a deviation to a target value and a control input and the thrust to cancel an external force received since the robot changes its posture are obtained by referring to the table prepared beforehand. By the adding arithmetic means 16, the vector sum of these two thrusts is obtained and the robot is promoted. For this reason, when the position holding and traveling operation are executed for the robot inside where the flow of a fluid of a tide, etc., exists, the robot can be operated by the thrust to compensate the collapse of the balance of the external force received from the fluid due to the posture change. Thus, the action of the moving, posture maintenance, etc., of the robot can be stably controlled and the smoothing of the work in the fluid by the robot can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the motion of a robot that maintains its position, posture, and moves three-dimensionally in the sea and underwater, and more specifically, The present invention relates to a control method that compensates for the effects on the robot due to such factors.

[Prior art]

In recent years, robots have begun to replace conventional dippers in the maintenance, inspection, and repair work of various offshore developments, underwater structures such as offshore oil production platforms, and underwater grounding equipment.
It is thought that this type of underwater robot that supports ocean development will become more and more popular in the future.

Some of these robots are those that move on orbits and those that move on the ocean floor, but in the future,
It is expected that there will be an increasing need for robots like Daiper that can swim freely in the sea, and various robots are being developed.

The environment in which a robot swimming underwater works is affected by currents such as currents, the Karman vortex caused by underwater structures, and various other water currents. In general, the shape of a robot is such that the force acting on it differs markedly depending on the direction in which it receives water resistance, such as a circular disc.If the robot changes its posture during position maintenance and travel control, the force it receives from the water flow as described above increases. The target (position or driving route) suddenly changes and loses balance.
There are problems such as the machine becoming uncoupled and being swept away, and in some cases becoming uncontrollable.

Therefore, conventional methods for controlling the movement, posture, etc. of this type of robot have been to prevent the robot's posture from changing in response to tidal currents, and the activities of the robot under the sea are extremely limited. However, a suitable control method for a robot that automatically maintains its position and posture and runs and works in tidal currents has not yet been obtained. Therefore, robots have not yet been able to completely replace work in ocean areas where there is a risk of the dialer being swept away by currents or caught in the Karman vortex.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems.In a working environment where there is a flow of water such as a tidal current, the robot can maintain its position even if it freely changes its posture while controlling its movement. The object of the present invention is to provide a control method that allows stable position maintenance and running without the risk of losing balance.

[Constitution of the invention] 3. The underwater robot of the present invention for achieving the above objects.
The configuration of the dimensional control method is that in controlling a robot to swim in a flowing fluid, (a) control input u (k) at time k and time,
Set a quadratic performance evaluation function J with the deviation e (k+1>) from the target value at The optimum control input U is calculated from the value X using the formula u=-
Calculate the thrust force Tc that achieves the target by finding it from G=X and feeding it back to the deviation e from the target, and (b)
When the E1 pot changes its attitude, the thrust force ■b that cancels the force acting on the robot for one column due to the velocity and direction of the current is determined in advance at the elevation angle α of the robot.
The coefficient C1j (α, β
) and the current velocity Vc of the tidal current, and (c) the vector sum of the two thrusts T=Tb+Tc is output as the thrust of the robot.

In the present invention, the calculation for obtaining the optimal feedback control U using G as the gain is performed using a dynamic programming method based on the optimality principle of Verma.

When carrying out the present invention, the above-mentioned secondary performance evaluation function when calculating the thrust force Te (hereinafter referred to as optimal control thrust) is, for example, the following formula (%)) (1) However, in formula (1), w (w≧0) represents a weighting coefficient.

The actual procedure for determining this optimal control thrust is shown below. Note that for convenience of explanation, a case will be described in which the position P and the orientation O are set as target values. Ground-fixed coordinate system (XE
YE ZE system), the thrust required to correct the deviation value between the target value Po and the estimated value P etc. achieved by observation]
゛Calculate the robot's state estimate X (indicates the estimated values of the robot's position, velocity, acceleration, attitude angle, angular velocity, and angular acceleration) using a C#-based state estimation value algorithm (observer), and further calculate this estimated value Optimal control u = X multiplied by control gain G that minimizes the quadratic performance evaluation function J
A thrust force Tc that compensates for deviations (drift, etc.) caused by influences such as tidal currents is calculated from the thrust force Tc' calculated from -G-X.

Although the means for calculating the thrust force TC is arbitrary, in a CPU-based control device, for example, the optimal control thrust force Tc is calculated by Tc'-T.
c', and further calculates this Tc as an estimated value of the current position and orientation based on actual measurements, and outputs this result to the robot. By repeating the robot control operation using this optimal control thrust Tc, the deviation value from the target value is successively corrected to zero.

To calculate the lower dynamic balance thrust,
First, the fluid resistance and moment coefficient C1j (α, β)
needs to be determined from a three-dimensional fluid resistance and moment coefficient table. In this method, the tidal current directions α, β, and tidal current velocity Vc are determined from the robot's water velocity (1) and the robot's absolute velocity V' estimated by the robot state estimation algorithm. Based on the current directions α and β, C1
Search for j(α,β).

The table can be determined, for example, by actually measuring the force that the robot receives when it is placed in a water tank and held in various postures against water flowing from a certain direction. The fluid resistance and moment coefficient determined in this way are stored in advance in the control device. The Guinamisoku balance thrust is composed of component forces with respect to the three-dimensional x, y, and z axes in the aircraft fixed coordinate system (XIRYRZR system) and moments around each axis (X in φ, θ, and ψ, respectively).

(representing the y- and z-axis planes) are each Tbx.

Then, ・ρ・■C2・Vb(21 ・ρ・V e 2− V b (3) However, in the formula, Vc
is the flow velocity, vb is the dimensionless reference volume, and vb is the dimensionless reference area.

Note that by expressing the coefficient C1j (α, β) using an elevation angle α and a sideslip angle β, which are angles relative to the robot's tidal flow, Tb can be obtained without considering the absolute posture.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The robot control method of the present invention will be explained below by way of an embodiment with reference to the drawings.

FIG. 1 is a block diagram showing the contents of the control calculation processing of the control device mounted on the robot targeted for this embodiment, and the dotted line in the figure shows the control block for Tb and Tc calculations made of a computer. FIG. 2 is a block diagram showing the overall configuration of control software. ``The robot used in this embodiment is configured to be operated according to three control modes.

That is, as shown in FIG. 1, each operation of the control means 1 in the position and attitude control mode, the control means 2 in the constant velocity route tracking control mode, and the control means 3 in the wall follow control mode can be selected. Then, the operator appropriately selects each of these control modes using the switching operation means 4 according to the work procedure. This switching operation means 4 can be switched at any time during work by remote control. Therefore, by this selection operation, the program for the work procedure is executed from the program input in advance to the control device provided in the robot.

Note that the position and attitude control mode is based on the ground-fixed coordinate system (
XE YE Zrs system), the current position of the robot,
This is a control mode to move the robot to a new underwater position and attitude set by the operator depending on the attitude state, and the position P (3-dimensional position: x) that the robot should reach is
, y, z) and the orientation of the robot, that is, the posture O (angles with respect to each axis of the three-dimensional coordinates fixed in the sea: φ, θ.

ψ). To specify whether to control in this mode in this embodiment, specify the final control values for position ip and attitude O, and specify the movement 1 speed U by specifying j
There was no 2.

Constant speed route/1 speed control mode
First, the robot 1 ~ is guided to the target structure position along the route I4 set in the underwater space by the operator by remote control, and second, the robot 1 ~ is guided to the target position of the structure along the route I4 set remotely in the vicinity of the target object. In order to observe the target object from 1, it is a control mode in which the vehicle travels at a constant speed above the target Lou River, and the coordinate system is fixed on the field surface (XFYEZE system). The position Po and attitude O in ,
o and the moving speed tJ in the route direction are sequentially specified by the program.

iii The wall flow control mode faces a curved structure, maintains a constant distance from the structure, and moves around it at a constant speed of +3! ,,,,This is a control mode for observing the object from scratch, with the attitude toward the wall O and the route 515.
Outside the moving speed U in the direction? :, Distance to be maintained from the wall ■,
is specified.

Note that although FIG. 2 illustrates the case where position and attitude control mode 1 is selected among the three control modes, the other configurations are exactly the same when other modes are selected. That is clear. L2, the calculation means according to the present invention is the target deviation value calculation means 5 surrounded by the dotted line in FIG.
1 and thrust calculation means 52, and the others are constructed by conventional means used for controlling this type of robot.

The data given to the calculation means 51 and 52 according to the present invention is the position Po that the robot should take based on the program.
(three-dimensional) target value, the direction in which the robot should face, that is, the posture Oo, and the estimated value v' of the absolute speed of the robot in X obtained as a result of robot state estimation. and 5 will be explained first.

First, the control device of this embodiment is equipped with obstacle avoidance route calculation means 6 to prevent the control in each of the modes from becoming impossible to work due to obstacles on the work route. The control calculation results can be modified as appropriate. The obstacle avoidance path calculation means 6 receives a de-
The data includes a model 6 for obstacles that can be input in advance, and detection data and currents detected by the obstacle detection means 63 using various sensors equipped while the robot is moving.

That is, based on the above data, the obstacle avoidance route calculation means 6 performs a calculation for correction as shown in FIG. 1 (this part is omitted in FIG. 2), and calculates the selected The target correcting means 7, route correcting means 8, and follow route correcting means 9 are provided for making corrections based on the calculation results of the respective control means 1.2 and 3 and the calculation results of the calculation means 6, depending on the control mode. In the calculations by the route correction means 8 and the follow route correction means 9, the speed U along the route is converted to the absolute speed Vo of the robot.
' also includes an operation for converting the relative distance i between the object and the robot into the robot's absolute position Po'.

7. Correction values for each of the above-mentioned instruction values, po/.

Oo', Vo' (both vector values) are
As mentioned above, the target deviation value calculation means 5. given to.

Explain. The robot body is equipped with an inertial navigation device (inertia p) or an acoustic measurement device (acoustic p) as a means of detecting the current position, and a gyro compass (gyro) to detect the direction the robot is facing and the attitude of the tapping robot. 0
) and ship speed ■ (relative speed with respect to water). It is equipped with a three-axis water speed meter, etc. to detect the robot's position, attitude, and speed at all times. As is well known, these detected values include detector drift and measurement noise, and if they are input as data to the control device, malfunctions will occur.
Regarding measurement noise, noise filter processing is performed using a Kalman filter as conventionally performed, and regarding drift, a measurement noise filter and drift compensation means 11 are used to periodically compensate for drift by pattern masoching using visual positioning. is the calculation means 5. and 52.

Also, the speed of the robot is determined by X obtained by the state estimating means 13.
The estimated value V' of the speed of the robot I is calculated by the calculation means 5.
1 and 5. given to. Note that the visual positioning shown in Figure 2 is performed for drift compensation, and is performed by a processor installed on the mother ship. The filter and drift compensation means 11 are processed by a processor provided in the mother ship, and the estimated values p, o, v of these results are sent to the robot and input to the control device.

Now, next, the dynamic balance thrust T in this embodiment
The calculation for determining b and the optimum control thrust Te will be explained based on FIG.

When the robot calculates the force Tc (vector) required to reach the instruction value (part or all of Po', Oo', and Vo') given based on each selected mode, this implementation is performed. In the example, the target deviation value calculation means 5
1, thrust conversion calculation means 12, state estimation means 13. , multivariable control gain and thrust conversion calculation 1. By executing each operation of stage 14 and addition operation means 15] 1 stage,
available. That is, the target deviation value calculating means 5° calculates the deviation value ΔP between the command value PO' (hereinafter, the command value will be explained as being based on "position") and the actual estimated arrival value P, and then 11↑force conversion is performed. 1, in which the calculation means 12 calculates the thrust force Tc# necessary to make this ΔP zero;
By the way, Fig. 2 L; - the above 111 [force calculation-1' shown
- Stage 52 is an abbreviation for each of the means 12 to 19 shown in FIG.

In parallel with the above calculation, the estimated values P, O and the TcO value obtained by the addition/subtraction calculation means 15 are provided to the state estimation means 13, and X indicating the motion state of the robot 1- is estimated. Regarding the positional movement, the configuration of X is: position P', velocity v
', acceleration A', and rotational motion are attitude angle 0', angular velocity OV', and angular acceleration '6A'. Then, based on this value, the multivariable control gain and thrust conversion calculation means 14 calculates a corrected thrust Tc for correcting the deviations ΔP and Δ0 (including Δ■ depending on the control mode) to the optimum value, and the addition calculation means 15 calculates the corrected thrust Tc. ''+Tc is calculated, and the resulting Tc is given again to the state estimating means 13 along with the estimated values p and o of the current position and orientation based on actual measurements, and the above calculation is repeated to correct the deviation to the optimum number.

Next, the means for calculating the dynamic balance thrust Tb will be explained. This calculation is achieved by performing calculations by the tidal flow inflow angle and flow velocity calculation means 17, the dynamic balance thrust calculation means 18, and the three-dimensional fluid resistance and moment coefficient table reference means 19.

The estimated velocity value V' is given to the tidal flow inflow angle and velocity calculation means 17, where the angle representing the relative attitude of the D robot (・) with respect to the tidal current, the angle formed by the robot's front upright direction, and the (The angle formed by the m angle α and the frontal direction, that is, the sideslip angle β and the absolute flow velocity Vc of the current are calculated, and these α and β
The fluid resistance coefficient C1j (α, β) corresponding to the value is determined by the three-dimensional fluid resistance and moment coefficient table reference means 19, and the Vc and C1j (α, β) are given to the dynamic balance thrust calculation means 18 to calculate the Tb is calculated from equations (2) and (3), and the calculation is carried out in the addition calculation means 16, that is, the above 1'b and the addition operation 'F
)115x, the sum (T
='rb+"l"C) becomes the thrust 1゛ actually exerted on the robot.

The value 'r obtained in this way is determined based on the change in the external force received from the tidal current and the thrust force output when the robot performs the posture, transfer, rib, etc. actions instructed based on the program of I pressure points 1, 1. ■What is the deviation from the gauge mark? 1Ii compensation, it is possible to perform control without losing balance due to tidal currents or moving away from the 1'' gage.

This thrust force T is subjected to JA calculation processing by the iI force distribution means 20 to distribute the 1111 force to drive each of the plurality of thrusters attached to the robot, and is output to the robot. In addition, the symbol '■゛'F/B in Fig. 2 is the thrust force T.
c shows the output of the feed pad used to check whether the thruster is being driven accurately by 4 degrees.

〔Effect of the invention〕

As explained above, the configuration of the three-dimensional control method for an underwater robot according to the present invention is such that the robot is able to control the thrust by the control gain that minimizes the quadratic performance evaluation function with the deviation from the target value and the control input as variables. The thrust force that cancels out the external force caused by changing the posture is determined by referring to a table created in advance, and the robot is propelled by the hector sum of the two thrust forces. When the robot is held in position and moved, the robot can be operated using thrust that compensates for the imbalance of external forces received from the fluid due to changes in posture. Therefore, it is possible to achieve the effect that the robot can perform operations in the fluid more smoothly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the contents of control calculation processing of a control device according to an embodiment, and FIG. 2 is a block diagram showing the overall configuration of rough 1-ware of the control block shown in FIG. 1. 51... Target deviation value computing means, 12... Thrust conversion computing means, 13... State estimation computing means, 14... Multivariable control gain and (11 Force change computing means, 15°16.
... Addition calculation means, 17... Tidal flow inflow angle and flow velocity calculation means, 18... Dynamic balance thrust calculation means,
19... Three-dimensional fluid resistance and moment coefficient table reference means, R... Robot body.

Claims (1)

[Claims] In the control of a robot for swimming in a flowing fluid such as a tidal current in the ocean, (a) a control input u(k) at time k and a deviation e(k+1) from a target value at time k+1; A quadratic performance evaluation function J with variables is set, and this performance evaluation function J
Determine the control gain G at which is the minimum, and calculate the optimal control input u using the equation Calculate the thrust force Tc that achieves the target by calculating it from u=-G・■ and feeding it back to the deviation e from the target, and (b) when the robot changes its posture, based on the flow velocity and direction of the tidal current relative to the robot. The thrust force ■b that cancels the tidal force acting on the robot is determined by the coefficient ■ij (α, β) obtained from a three-dimensional fluid resistance and moment coefficient table prepared in advance as a function of the tidal current elevation angle α and sideslip angle β of the robot. A traveling control method for an underwater robot, comprising: calculating from a current velocity Vc of a tidal current, and (c) outputting a vector sum of the two thrust forces T=Tb+Tc as the thrust force of the robot.