Device and method for controlling rotation of container

Abstract

 A device for controlling the rotation of a container used for a crane which includes a jib (2) for hanging a container (19) via a lifting attachment (15) and a rope (3), the device rotating the container by rotating the rope using a rotation motor (16). The device includes a container rotation angle obtaining unit (22,23); a lifting attachment rotation angle obtaining unit; a control computing unit (50) which computes a motor control command value based on an equation relating to a deviation between a target rotation angle and the rotation angle of the container, an angle of the lifting attachment member, and the motor control command value; a rotation motor control unit which drives the rotation motor; and a feedback control unit which performs feedback control on the rotation angle of the container and the angle of the lifting attachment member so that the rotation angle of the container matches the target rotation angle of the container.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a device for controlling the rotation of a container, and a method for controlling the rotation of a container. More specifically, the present invention relates to a device and a method for controlling the rotation of a cargo container by which a hoisted cargo container may be rapidly transferred while reducing rotation and swinging thereof.

[0002] This application is based on Japanese Patent Application No. 2002-32887, the content of which is incorporated herein by reference.

2. Description of Related Art

[0003] In a mobile harbor crane in which a lifting attachment member from which a cargo container (hereinafter also referred to as a cargo) may be hung via a cable (hereinafter also referred to as a rope, or a wire), is hung from a jib point of the crane, and the cargo container may be rotated by actuating a rotation motor provided with the lifting attachment member that rotates an end of the rope supported by the lifting attachment, for example, if it is required that a container, which is placed on a deck of a ship in a vertical direction with respect to a dock, be landed on the yard of the harbor so as to be parallel with respect to the dock, the operation for controlling the rotation of the cargo container is carried out by an operator of the crane who manually controls the rotation motor.

[0004] However, when the rotation motor is rotated, the lifting attachment member rotates and swings due to the reaction force generated by rotating the hoisted cargo container. Accordingly, the swing of the lifting attachment member affects the hoisted cargo container, and the container is also rotated and swung.

[0005] Accordingly, it is very difficult and laborious even for a skilled operator to control the rotation of a cargo container in the situation where both the lifting attachment member and the container are swung.

SUMMARY OF THE INVENTION

[0006] The present invention takes into consideration the above-mentioned circumstances, and has as an object to provide a device and a method for controlling the rotation of a container by which labor of an operator for carrying out the crane operation may be reduced by automating the control of the rotation of a hoisted cargo container.

[0007] In order to achieve the above object, the first aspect of the present invention provides a device for controlling the rotation of a container used for a crane which includes a jib having a jib point from which a container is hung via a lifting attachment member and a rope member (also referred to as a cable member, or a wire member), the device for controlling the rotation of a container rotating the container by rotating an end of the rope member supported at the lifting attachment member side using a rotation motor disposed at the lifting attachment member, the device including a hoisted container rotation angle obtaining unit which obtains a rotation angle (ζ) of the container; a lifting attachment rotation angle obtaining unit which obtains a rotation angle (β) of the lifting attachment member; a control computing unit which computes a motor control command value (µ) based on a predetermined equation relating to a deviation (ζ_ref - ζ) between a predetermined target rotation angle (ζ_ref) of the container and the rotation angle (ζ) of the container obtained by the hoisted container rotation angle obtaining unit, an angle of the lifting attachment member(β), and the motor control command value (µ) for operating the rotation motor; a rotation motor control unit which drives the rotation motor based on the motor control command value computed by the control computing unit; and a feedback control unit which performs feedback control on the rotation angle (ζ) of the container and the angle (β) of the lifting attachment member so that the rotation angle (ζ) of the container matches the target rotation angle (ζ_ref) of the container.

[0008] According to the above device for controlling the rotation of a container, the motor control command value µ for the rotation motor is computed using the predetermined equation, the rotation motor is driven using the motor control command value µ, and the rotation angle of the container is automatically matched to the target rotation angle of the container by performing a feedback control on the rotation angle ζ of the container and the relative rotation angle θ which express the change in position of the lifting attachment member and the container. Accordingly, it becomes possible to significantly reduce the labor of an operator of the crane relating to an operation for controlling the rotation of the container.

[0009] In accordance with the second aspect of the present invention, the device for controlling the rotation of a container according to the first aspect of the invention further includes a relative rotation angle detection unit which detects a relative rotation angle (θ) which is a relative angle of the container with respect to the lifting attachment member, and the lifting attachment rotation angle obtaining unit computes the angle (β) of the lifting attachment member by subtracting the relative rotation angle (θ) from the rotation angle (ζ) of the container.

[0010] The above relative rotation angle detection unit is an encoder attached to the rotation motor, and the lifting attachment rotation angle obtaining unit captures a marker using a camera device, which is disposed at the jib, to obtain the rotation angle ζ of the container by detecting the change in position of the marker from the captured image thereof.

[0011] Here, both the detection of the relative rotation angle using the encoder and the detection of the rotation angle of the container using the camera device are conventionally well known techniques, and are detection devices often provided with a crane. Accordingly, the angle of the lifting attachment member may be very easily obtained by calculating the angle of the lifting attachment member based on values detected by various detection devices which are already provided with the crane. Therefore, it is unnecessary to install new sensors, etc., for detecting the angle of the lifting attachment member according to an embodiment of the present invention.

[0012] In accordance with the third aspect of the present invention, the device for controlling the rotation of a container according to the first or second aspect of the invention further includes a hoisted container rotational angular velocity computing unit which computes a rotational angular velocity (ζ) of the container by differentiating the rotation angle of the container, and a lifting attachment angular velocity computing unit which computes an angular velocity (β) of the lifting attachment member by differentiating the rotation angle of the lifting attachment member, wherein the predetermined equation is an equation in which the deviation between the target rotation angle of the container and the rotation angle of the container, the angle of the lifting attachment member, and the angular velocity of the lifting attachment member are used as parameters (variables).

[0013] By using the rotational angular velocity ζ of the container and the angular velocity β of the lifting attachment member also as parameters, it becomes possible to carry out a control in which the change in position of the lifting attachment member and the hoisted container is more precisely reflected. As a result, it also becomes possible to quickly make the rotation angle of the container equal to the target rotation angle while maintaining the generation of swing to a minimum level.

[0014] Note that in this specification the symbol indicates a first order differential, and the symbol indicates a second order differential. For example, the first order differential of the symbol β is expressed as β, and the second order differential of the symbol β is expressed as β. The same rule applies for the symbols contained in the following equations and diagrams.

[0015] In accordance with the fourth aspect of the present invention, in the device for controlling the rotation of a container according to the third aspect of the invention, the predetermined equation is an equation in which the four parameters (variables) are multiplied by a respective characteristic proportional gain, and a result of each multiplication is added to be given as the motor control command value.

[0016] By multiplying the variables of state by the appropriate proportional gain when the variables of state of the lifting attachment member and the container are feedback controlled, it becomes possible to quickly rotate the hoisted container to the target rotation angle thereof while preventing the generation of swing due to the rotation.

[0017] In accordance with the fifth aspect of the present invention, in the device for controlling the rotation of a container according to the fourth aspect of the invention, the proportional gain is determined based on an optimum control theory provided that both the deviation between the target rotation angle of the container and the rotation angle of the container, and the angle of the lifting attachment member are converged to be zero.

[0018] By determining the optimum value for the proportional gain in the predetermined equation, it becomes possible to rotate the hoisted container to the target rotation angle thereof in an extremely efficient manner while preventing the generation of swing of the lifting attachment member and the container due to the rotation.

[0019] The sixth aspect of the present invention also provides a method for controlling the rotation of a container used for a crane which includes a jib having a jib point from which a container is hung via a lifting attachment member and a rope member, the container being rotated by rotating an end of the rope member supported at the lifting attachment member side using a rotation motor disposed at the lifting attachment member, the method comprising the steps of: computing a motor control command value based on a predetermined equation relating to variables of state (ζ, θ) which express rotational movement of the lifting attachment member and the container, a target rotation angle (ζ_ref) of the container, and the motor control command value (µ) for operating the rotation motor; driving the rotation motor based on the motor control command value, and performing a feedback control on the variables of state so that the rotation angle of the container matches the target rotation angle of the container.

[0020] The seventh aspect of the present invention also provides a method for controlling the rotation of a container used for a crane which includes a jib having a jib point from which a container is hung via a lifting attachment member and a rope member, the container being rotated by rotating an end of the rope member supported at the lifting attachment member side using a rotation motor disposed at the lifting attachment member, the method comprising the steps of: obtaining a rotation angle of the container; obtaining a rotation angle of the lifting attachment member; computing a motor control command value based on a predetermined equation relating to a deviation between a predetermined target rotation angle of the container and the rotation angle of the container, an angle of the lifting attachment member, and the motor control command value for operating the rotation motor; driving the rotation motor based on the motor control command value, and performing a feedback control on the rotation angle of the container and the angle of the lifting attachment member so that the rotation angle of the container matches the target rotation angle of the container.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Some of the features and advantages of the invention having been described, others will become apparent from the detailed description which follows, and from the accompanying drawings, in which:

FIG 1 is a schematic diagram showing a general mobile harbor crane;

FIG 2 is a diagram showing from a jib point to a container viewed from the direction indicated by the arrow S shown in FIG 1;

FIG 3 is a schematic diagram showing a control system of a rotation motor;

FIG 4 is a diagram showing the concept of the control system of the device for controlling the rotation of a hoisted container shown in FIG 3;

FIG. 5 is a diagram showing the control logic of a control device;

FIG. 6 is a diagram showing the relationship between a container and a lifting attachment member for defining each parameter; and

FIGS. 7A through 7D are diagrams showing results of a simulation carried out to verify the device for controlling the rotation of a container according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The invention summarized above and defined by the enumerated claims may be better understood by referring to the following detailed description, which should be read with reference to the accompanying diagrams. This detailed description of particular preferred embodiments, set out below to enable one to build and use one particular implementation of the invention, is not intended to limit the enumerated claims, but to serve as specific examples thereof.

[0023] FIG. 1 is a diagram showing a schematic structure of a mobile harbor crane being an example of a crane to which a device for controlling the rotation of a hoisted container according to an embodiment of the present invention is applied.

(1) Schematic structure of the mobile harbor crane:

[0024] In FIG 1, which shows the schematic structure of the entire mobile harbor crane, the numeral 1 indicates a mobile harbor crane (hereinafter also simply referred to as a "body") which may be suitably used in a harbor facility as harbor equipment. The body 1 of the mobile harbor crane mainly includes a carrier frame 11 provided with a plurality of outriggers 12, a revolving frame 13 and a main frame 14, each of which is mounted on the carrier frame 11, and a jib 2 attached to the main frame 14.

[0025] The carrier frame 11 secures the stability of the body 1 by means of the plurality of the outriggers 12, each of which protrude from both sides of the carrier frame 11 in a vertical direction with respect to the longitudinal direction thereof.

[0026] When the outriggers 12 are accommodated in the carrier frame 11, the crane can move around the yard of the harbor by means of wheels (not shown in the figure).

[0027] Swing bearings of circular shape (not shown in the figure) are provided at substantially the center portion of the carrier frame 11, and the revolving frame 13 is mounted on the carrier frame 11 via the swing bearings. Gear racks are formed around the swing bearings and pinions (not shown in the figures), which are attached to a revolving driving unit (not shown in the figures), are engaged with the pinions. The revolving driving unit is attached to the revolving frame 13 side.

[0028] Accordingly, the revolving frame 13 is rotatable 360° around the center of the swinging bearings due to the rotation of the pinions. Note that the center of the swinging bearings means the rotation center O, and indicates the center of the operating radius of the crane carrying out the handling operation of a cargo.

[0029] Also, a revolution angle detection device 5a, which detects the revolution direction of the revolving frame 13 with respect to the carrier frame 11 is disposed in the vicinity of the revolving center O of the revolving frame 13. The revolution angle detection device 5a is connected to the control unit 10, which will be described later, by a cable indicated by dotted lines.

[0030] On the revolving frame 13, the main frame 14, winches 4 and 4' (not shown in the figure), a cylinder 6, and an operation room (not shown in the figure) are mainly provided. The main frame 14 rotatably supports a base end portion of the jib 2. The winches 4 and 4' wind up ropes 3 and 3' (in this specification, the term "rope" means any flexible cords, such as cables and wires) connected to a lifting attachment member 15. The cylinder 6 hoists the jib 2, and an operator occupies the operation room to perform crane operations.

[0031] Note that the rope 3' and the winch 4' are provided parallel to the rope 3 and the winch 4, respectively, toward the back of the figure. Also, the winches 4 and 4' are provided with encoders 4a and 4a', respectively, each of which detects a state of the length of the rope 3 and 3'.

[0032] The main frame 14 has a truss structure in which a plurality of rod type members are combined. The base end portion of the jib 2 (the left hand side in the figure) is attached to substantially the middle position of the main frame 14 via jib foot pins (not shown in the figures).

[0033] The jib 2 has a long shape with a truss structure, and the base end portion of the jib 2 is rotatably supported by the main frame 14 as explained above. Also, an end portion of the cylinder 6 at the rod side is rotatably attached to an underside position of the base end portion of the jib 2 slightly shifted towards the jib point side via pins (not shown in the figure). In this manner, the jib 2 is supported. Another end portion of the cylinder 6 at the bottom side is rotatably attached to a front portion of the revolving frame 13 via pins (not shown in the figures).

[0034] The jib 2 is hoisted with respect to the jib foot pin, which functions as the center, by extension and retraction operations of the cylinder 6, and the jib operating radius based on the jib point H is determined.

[0035] Next, the configuration from the jib point H to a hoisted cargo G including the lifting attachment member 15 will be described with reference to FIGS. 2 and 3. FIG 2 is a diagram showing from the jib point H to the container 19 viewed from the direction indicated by the arrow S shown in FIG 1. FIG 3 is a schematic diagram showing a control system of a rotation motor 16.

[0036] In FIG 2, one end of the ropes 3 and 3', respectively, is fixed to the lifting attachment member 15, and the other end of the ropes 3 and 3' are wound up by the winches 4 and 4' disposed on the revolving frame 13. Accordingly, the lifting attachment member 15 is moved up when the ropes 3 and 3' are wound up by the winches 4 and 4', and the lifting attachment member 15 is moved down when the winches 4 and 4' are rotated in the reverse direction. Also, a spreader 18 and the container 19 (hereinafter these are referred to as "hoisted cargo container G"), which is hung from the lifting attachment member 15 via the rope 30, are moved up and down in accordance with moving up and down of the lifting attachment member 15.

[0037] The rotation motor 16 is disposed below the lifting attachment member 15, and a hook 17 is disposed below the rotation motor 16. Also, the spreader 18 is hung using the hook 17 via the rope 30.

[0038] An encoder (not shown in the figure) is attached to the rotation motor 16. The encoder detects a relative rotation angle θ, which is a relative angle of the hoisted cargo container with respect to the lifting attachment member 15. The encoder then transmits the detected relative rotation angle θ to a control device 50. Note that the control device 50 is disposed at a part of the control unit 10 explained above (refer to FIG 1).

[0039] Also, markers 20 and 21 are attached to the upper surface of the spreader 18, and the position of the marker is captured using cameras 22 and 23, which are disposed at the right hand side end and the left hand side end, respectively, of the jib point H so that the images of the markers 20 and 21 may be transmitted to an image processing unit (not shown in the figure). The image processing unit detects the position of the right marker and that of the left marker, and computes a hoisted cargo container rotation angle ζ, which is a relative angle of the hoisted cargo container with respect to the jib point H, by dividing the difference in change of the position of the markers by the distance between the right marker and the left marker. After this, the detected hoisted cargo container rotation angle ζ is transmitted to the control unit 10.

[0040] The control device 50 receives, as input signals, the hoisted cargo container rotation angle ζ detected by the image processing unit of the cameras 22 and 23, the relative rotation angle θ detected by the encoder attached to the rotation motor 16, and a target hoisted cargo container rotation angle ζ_ref, which is computed by a superior computer or input by an operator of the crane. Then, the control device 50 computes a motor control command value µ for the rotation motor 16, which makes the actual hoisted cargo container rotation angle ζ equal to the target hoisted cargo container rotation angle ζ_ref, and outputs the motor control command value µ to a drive control unit (not shown in the figure) of the rotation motor 16.

[0041] In this manner, the drive control unit of the rotation motor drives the rotation motor 16 based on the motor control command value µ. In practice, the drive control unit controls the amount of current which flows through inverters, and so forth. By rotating the rotation motor based on the motor control command value µ as mentioned above, the end of the rope 30 at the lifting attachment member supported by the hook 17, which is connected to the rotation motor 16, is rotated so that the hoisted cargo container G may be rotated.

[0042] Note that, as shown in FIG 3, the hoisted cargo container rotation control device according to the embodiment of the present invention includes, as its main structural elements, the markers 20 and 21, the cameras 22 and 23, and the image processing unit (not shown in the figure) as a means for obtaining the hoisted cargo container rotation angle, which detects the hoisted cargo container rotation angle ζ, encoders (not shown in the figure) as a means for detecting the relative rotation angle, the control device 50, and the drive control unit (not shown in the figure).

(2) Definition of each parameter:

[0043] Hereinafter, the definition of the above-mentioned hoisted cargo container rotation angle ζ, the relative rotation angle θ, and a lifting attachment angle β, etc., will be explained with reference to FIG 6. Note that in FIG 6, the rope 30 is omitted for simplifying the diagram.

[0044] In FIG 6, each end of the ropes 3 and 3 at the jib point H side is defined as E1 and E2, respectively, and each end of the ropes 3 and 3 at the lifting attachment member 15 side is defined as E3 and E4, respectively. Also, the angle between an upper side of the jib point H (this is regarded as a reference line q) and a line connecting the E1 and E2 is defined to be a fulcrum angle φ. Similarly, the angle between the line connecting E1 and E2 and a line connecting the E3 and E4 is defined to be the lifting attachment angle β. Also, the angle between the line connecting E3 and E4 and a side of the hoisted cargo container G in the longitudinal direction is defined to be the relative rotation angle θ. That is, the relative rotation angle θ is a relative angle between the lifting attachment member 15 and the hoisted cargo container G.

[0045] Also, the length of the rope from the jib point H to the lifting attachment member 15 is defined to be the rope length 1. That is, the rope length 1 is equal to the distance between E1 and E3, which in turn equals to the distance between E2 and E4. Also, the mass of the lifting attachment member 15 is defined to be the lifting attachment mass m, and the mass of the hoisted cargo container is defined to be the hoisted cargo container mass M. Here, the hoisted cargo container mass M means the total of the mass of the spreader 18 and the container 19. Also, the distance between the two ropes at the jib point H, i.e., the distance between E1 and E2, is defined to be the distance 2d.

[0046] Note that since the ropes 3 and 3' are substantially fixed to the jib point H in this embodiment, it is possible to assume that the fulcrum angle φ is equal to zero. Therefore, it is possible to assume that the lifting attachment angle β is equal to the angle of the lifting attachment member with respect to the reference line q. Also, the angle of the hoisted cargo container with respect to the reference line q, i.e., the hoisted cargo container rotation angle ζ, may be expressed as the sum of the lifting attachment angle β and the relative rotation angle θ (i.e., ζ = β + θ).

(3) Control system of the hoisted container rotation control device according to the embodiment of the present invention:

[0047] FIG 4 is a diagram showing the concept of the control system of the hoisted container rotation control device shown in FIG 3. As shown in the figure, the hoisted cargo container rotation angle ζ, and the relative rotation angle θ as well as the target hoisted cargo container rotation angle ζ_ref are input into the control device 50 as detected signals.

[0048] The control device 50 computes the motor control command value µ based on these input information and outputs the results. Also, the control device 50 carries out a feedback control for the hoisted cargo container rotation angle ζ and the relative rotation angle θ as detected values so that the hoisted cargo container rotation angle ζ matches the target hoisted cargo container rotation angle ζ_ref.

[0049] In this manner, it becomes possible to efficiently match the rotation angle of the hoisted cargo container G with the target hoisted cargo container rotation angle ζ_ref by performing the feedback control on the hoisted cargo container rotation angle ζ and the relative rotation angle θ which are varied by driving the motor based on the above-mentioned motor control command value µ.

(4) Control logic of the control device 50:

[0050] FIG 5 is a diagram showing the control logic of the control device 50. The control device 50 includes a control computing unit 65 and a feedback control unit 66. The control computing unit 65 computes the motor control command value µ based on a predetermined equation relating to the deviation (ξ_ref-ξ) between the target hoisted cargo container rotation angle ζ_ref and the hoisted cargo container rotation angle ζ, the lifting attachment angle β, and the motor control command value µ for driving the rotation motor 16. The feedback control unit 66 performs feedback on the detection values of the hoisted cargo container rotation angle ζ and the relative rotation angle θ, and computes each parameter (variable) to be assigned to predetermined equations based on the feedback values of the hoisted cargo container rotation angle ζ and the relative rotation angle θ.

[0051] The feedback control unit 66 includes a subtractor 61, a differentiation unit 62, another subtractor 63, and another differential unit 64, and outputs calculation results to the control computing unit 65. The subtractor 61 computes deviation by subtracting the feedback value of the hoisted cargo container rotation angle ζ from the target hoisted cargo container rotation angle ζ_ref. The differentiation unit 62 computes the hoisted cargo container rotational angular velocity ζ by differentiating the hoisted cargo container rotation angle ζ. The subtractor 63 computes the lifting attachment rotation angle β by subtracting the relative rotation angle θ from the hoisted cargo container rotation angle ζ. The differential unit 64 computes the lifting attachment rotational angular velocity β by differentiating the lifting attachment angle β obtained by the subtractor 63.

[0052] The control computing unit 65 assigns each calculated value, which is input from the feedback control unit 66, to the predetermined equation (1) shown below to obtain the motor control command value µ.

[0053] Note that in the above equation (1), each of k₁, k₂, k₃, and k₄ is a proportional gain, which is determined based on the optimum control theory under the condition that both the deviation between the hoisted cargo container rotation angle ζ and the target hoisted cargo container rotation angle ζ_ref, and the lifting attachment angle β become zero. The procedure relating to the determination of the proportional gains will be explained later.

[0054] According to the device for controlling the rotation of a container of the embodiment of the present invention, as explained above, the motor control command value µ for driving the rotation motor is calculated using the predetermined equation relating to the lifting attachment angle β and the hoisted cargo container rotation angle ζ, which are parameters expressing the motion of the hoisted cargo container and the lifting attachment member, the target hoisted cargo container rotation angle ζ_ref, and the motor control command value µ for the rotation motor. The rotation motor is driven based on the motor control command value µ, and the feedback control is performed on the hoisted cargo container rotation angle ζ and the relative rotation angle θ, which express the change in position of the lifting attachment member and the hoisted cargo container.

[0055] In this manner, it becomes possible to automatically control the hoisted cargo container rotation angle to match the target hoisted cargo rotation angle, and hence, the labor for an operator relating to the control of rotation of the hoisted cargo container may be significantly reduced.

[0056] Also, by determining the proportional gains in the predetermined equation to be optimum values, it becomes possible to rotate the hoisted cargo container to the target rotation angle in an extremely efficient manner while preventing the generation of rotation and swing of the lifting attachment member and the hoisted cargo container.

[0057] Moreover, it becomes possible to carry out a control in which the change in position of the lifting attachment member and the hoisted cargo container is more precisely reflected by using differentiated values of the detected values (i.e., values of the hoisted cargo container rotational angular velocity ζ and the lifting attachment rotational angular velocity β).

(5) Determination of proportional gains k₁, k₂, k₃, and k₄, and simulation performed in order to verify the device for controlling the rotation of a container according to the present invention:

(5-1) Derivation of the equation of state for the entire controlled system:

[0058] In order to carry out the simulation for determining the proportional gains k₁, k₂, k₃, and k₄ in the equation (1), an equation of state for the entire controlled system, which expresses the relationship among the lifting attachment member 15, the hoisted cargo container G, and the rotation motor is necessary.

[0059] Accordingly, the derivation of the equation of state for the entire controlled system, which is essential for the simulation, will be explained.

[0060] First, the derivation of the equation of motion for the rotational movement of the lifting attachment member 15 and the hoisted cargo container G in the relationship thereof shown in FIG. 6 will be explained.

[0061] Assuming that the lifting attachment member 15 and the hoisted cargo container G are located at their lowest positions when the lifting attachment angle β is equal to zero, then, the moving distance z of the lifting attachment member 15 and the hoisted cargo container G with respect to the respective lowest position may be expressed by the following equation (2).

[0062] Here, the kinetic energy T may be expressed by the following equation (3).

[0063] Also, the potential energy V at that particular moment may be expressed by the following equation (4).

[0064] Next, the above equations (2)-(4) are applied to the following Lagrange's equation (5) to derive the equation of motion for the lifting attachment angle β and the relative rotation angle θ assuming that the rope length 1 will be changed from time to time.

[0065] Then, linearization is performed on the above equation of motion in order to design the control system.

[0066] First, regarding the rope length 1, it is assumed

+

= 0.

[0067] Also, when β << 1, then, sin β≒ β, and cos β = 1.

[0068] These are assigned to the equation of motion of the above formula (5), and the following two equations (6) and (7) may be derived by ignoring secondary or greater terms relating to the lifting attachment angle β.

[0069] The above equations (6) and (7) may be further modified as the following equations (8) and (9).

[0070] In the above equations (8) and (9), A₁ may be expressed as the following equation (10).

[0071] From the above equation (10), the following equation of state (11) may be derived assuming that the state vector x = [β β̇ θ θ̇].

[0072] Then, the equation of state for the entire controlled system may be derived by adding a numerical model of the rotation motor 16, which is an actuator, to the equation of state relating to the rotational movement which is derived as explained above. Here, the numerical model of the rotation motor 16 may be expressed by the following equation (12).

In the equation (12), f is the driving torque generated by the rotation motor 16, µ is the motor control command value (for instance, velocity command value) for controlling the drive of the rotation motor 16, K_p and T_I are proportional gain and integral gain, respectively, of the motor control system, and I_m is the moment of inertia converted to the gear side shaft of the motor + gear system.

[0073] Here, if the integral amount µ_I of µ is added as a state function, and the state vector x is defined to be x = [β β̇ θ θ̇µ_I], then the numerical model of the rotation motor 16 may be expressed as the following formula (13).

[0074] If the above formula (13) is combined with the equation (11), which is the equation of state for the rotation movement, to derive the equation of state for the entire controlled system, the following equations (14) may be obtained.

(5-2) Performance of simulation:

[0075] Next, the simulation which was carried out in order to determine the proportional gains k₁, k₂, k₃, and k₄, and to verify the device for controlling the rotation of a container according to the embodiment of the present invention will be described.

[0076] Here, the block diagram for the simulation is the same as the block diagram shown in FIG 4. However, note that the equations (14), which are the equations of state for the entire controlled system as explained above, was used as the objects 52 to be controlled. Also, the control device 50 used was the one shown in FIG. 5. Moreover, each parameter for the objects to be controlled was as shown in Table 1 below. As the set value for each of the parameters, practical values are used which may be determined from diagrams of an actual device and so forth.

Table 1

Parameters	Symbols	Units	Values
Rope length	1	M	40
Mass of lifting attachment	m	kg	3,000
Mass of cargo container	M	kg	30,000
Inertia moment of lifting attachment	I	kg · m2	3,760
Inertia moment of cargo container	J	kg · m2	290,514
Half of distance between two ropes	d	M	1.65
Proportional gain (rotation motor)	kp	Nm/(rad/s)	65,546
Integral time (rotation motor)	TI	S	1.0
Inertia moment of motor + gear	Im	kg · m2	3,736

[0077] Next, the procedures for determining the proportional gains k₁, k₂, k₃, and k₄ will be explained.

[0078] First, the equation of state for the entire controlled system may be given as the following equation (15) as indicated in the equations (14).

[0079] Also, the evaluation function J was set as shown in the following equation (16).

[0080] In the above equation (16), Q and r are adjusting parameters of so called 5×5 weighting matrix and 1×1 weighting matrix, respectively. Also, in the equation (15), A' and B' are constant matrix which may be obtained by assigning a value of A, B, H₁, H₂, and H₃, which may be derived from the above equations (10), (11), and (13), to each of the equations (14).

[0081] Then, using the commercially available control system design tool MATLAB, the proportional gains k₁, k₂, k₃, and k₄ in the following equation (17), which minimize the evaluation function J, i.e., quickly makes the value of x zero using a small µ, were obtained.

Here, Q and r are adjusting parameters. The above simulation was performed repeatedly, and adjustments were made under the following evaluation conditions.

(condition 1): that the hoisted cargo container rotation angle ζ be quickly matched to the target hoisted cargo container rotation angle ζ_ref.

(condition 2): that the generated lifting attachment angle β, i.e., the swing of the lifting attachment member, be quickly reduced.

[0082] As a result, the above adjusting parameters Q and r were determined to be values shown in the following formula (18).

[0083] Also, the proportional gains k₁, k₂, k₃, and k₄ at that moment, i.e., the proportional gains suitable for carrying out the control of the rotation of a hoisted cargo container, were obtained, and the value of each is shown in the following Table 2.

Table 2

Proportional control gains	Units	Values
k1	rad/s/(rad)	-3.1
k2	rad/s/(rad/s)	-9.3
k3	rad/s/(rad)	1.1
k4	rad/s/(rad/s)	-0.051

[0084] Then, the device for controlling the rotation of a hoisted cargo container according to the embodiment of the present invention was verified using the same simulator. Note that the values of the proportional gains k₁, k₂, k₃, and k₄ used for the verification were the same as the values shown in Table 2. The results of the simulation were shown in FIGS. 7A through 7D.

[0085] As the conditions for obtaining the results of the simulation shown in FIGS. 7A though 7D, the value of each parameter was set as shown in Table 1, and the target hoisted cargo container rotation angle ζ_ref, the lifting attachment angle β, and the relative rotation angle θ, were initialized to be zero, zero , and 0.1 rad, respectively. That is, in this case, since the hoisted cargo container rotation angle ζ is:

the control device 50 obtains the motor control command value µ of the rotation motor so that the hoisted cargo container rotation angle ζ becomes zero rad, which is target hoisted cargo container rotation angle, while carrying out feedback control on the state function [β β̇ θ θ̇] of the lifting attachment member and the hoisted cargo container.

[0086] As a result, the motor control command value µ of the rotation motor 16 was obtained as a pattern shown in FIG 7A, and the hoisted cargo container rotation angle ζ, the lifting attachment angle β, and the relative rotation angle θ, were changed as shown in FIGS. 7B through 7D, by controlling the motor based on the motor control command value µ. After about 20 seconds, the hoisted cargo container rotation angle ζ became zero, which was the target hoisted cargo container rotation angle ζ_ref, and the lifting attachment angle β also became zero.

[0087] Accordingly, the effectiveness of the device for controlling the rotation of the hoisted cargo container according to the embodiment of the present invention was verified.

[0088] Although the device for controlling the rotation of the hoisted cargo container according to one embodiment of the present invention has been explained above, it is possible to record a program for performing each function of the control device 50 shown in FIG. 5 on a computer readable recording medium, and to make a computer system read the program recorded on the recording medium to perform each process.

[0089] Note that the term "computer system" used in this specification includes an operation system and hardware, such as peripherals.

[0090] Also, the term "computer readable recording medium" includes, for instance, an optical disc, such as CD-ROM, an magneto-optical disc, such as MO and MD, a magnetic recording medium, such as HDD and FD, a transportable recording medium, such as flash memory and semiconductor memory, and a recording device such as a hard disc which is incorporated in a computer system.

[0091] Moreover, the term "computer readable recording medium" further includes one which is capable of maintaining a program for a certain period of time. Examples of the "computer readable recording medium" includes a network such as the Internet, a server to which a program is transmitted via a communication line, such as a telephone circuit, and a volatile memory (RAM) inside a computer system which becomes a client.

[0092] Also, the above-mentioned program may be transmitted to another computer system from a computer system in which the program is stored in a recording device, etc., via a transmission medium or transmission wave contained in a transmission medium. Here, the term "transmission medium" transmitting a program means a medium having function of transmitting information, examples of which including a network (a communication network) such as the Internet, and a communication circuit (a communication line), such as a telephone circuit.

[0093] Also, the above program may be one which realizes a part of the above-mentioned function. Moreover, the above program may be a so called difference file (a difference program) which realizes the above-mentioned function when combining with a program which is already recorded in a computer system.

[0094] Having thus described several exemplary embodiments of the invention, it will be apparent that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements, though not expressly described above, are nonetheless intended and implied to be within the spirit and scope of the invention. Accordingly, the invention is limited and defined only by the following claims and equivalents thereto.

Claims

1. A device for controlling the rotation of a container used for a crane which includes a jib having a jib point from which a container is hung via a lifting attachment member and a rope member, said device for controlling the rotation of a container rotating said container by rotating an end of said rope member supported at said lifting attachment member side using a rotation motor disposed at said lifting attachment member, said device comprising:

a hoisted container rotation angle obtaining unit which obtains a rotation angle of said container;

a lifting attachment rotation angle obtaining unit which obtains a rotation angle of said lifting attachment member;

a control computing unit which computes a motor control command value based on a predetermined equation relating to a deviation between a predetermined target rotation angle of said container and the rotation angle of said container obtained by said hoisted container rotation angle obtaining unit, an angle of said lifting attachment member, and the motor control command value for operating said rotation motor;

a rotation motor control unit which drives said rotation motor based on the motor control command value computed by said control computing unit; and

a feedback control unit which performs feedback control on the rotation angle of said container and the angle of said lifting attachment member so that the rotation angle of said container matches the target rotation angle of said container.

2. A device for controlling the rotation of a container according to claim 1, further comprising:

a relative rotation angle detection unit which detects a relative rotation angle which is a relative angle of said container with respect to said lifting attachment member, wherein

said lifting attachment rotation angle obtaining unit computes the angle of said lifting attachment member by subtracting the relative rotation angle from the rotation angle of said container.

3. A device for controlling the rotation of a container according to claim 1, further comprising:

a hoisted container rotational angular velocity computing unit which computes a rotational angular velocity of said container by differentiating the rotation angle of said container, and

a lifting attachment angular velocity computing unit which computes an angular velocity of said lifting attachment member by differentiating the rotation angle of said lifting attachment member, wherein

said predetermined equation is an equation in which the deviation between the target rotation angle of said container and the rotation angle of said container, the angle of said lifting attachment member, and the angular velocity of said lifting attachment member are used as parameters.

4. A device for controlling the rotation of a container according to claim 2, further comprising:

a hoisted container rotational angular velocity computing unit which computes a rotational angular velocity of said container by differentiating the rotation angle of said container, and

a lifting attachment angular velocity computing unit which computes an angular velocity of said lifting attachment member by differentiating the rotation angle of said lifting attachment member, wherein

said predetermined equation is an equation in which the deviation between the target rotation angle of said container and the rotation angle of said container, the angle of said lifting attachment member, and the angular velocity of said lifting attachment member are used as parameters.

5. A device for controlling the rotation of a container according to claim 3, wherein
   said predetermined equation is an equation in which said four parameters are multiplied by a respective characteristic proportional gain, and a result of each multiplication is added to be given as the motor control command value.

6. A device for controlling the rotation of a container according to claim 4, wherein
   said predetermined equation is an equation in which said four parameters are multiplied by a respective characteristic proportional gain, and a result of each multiplication is added to be given as the motor control command value.

7. A device for controlling the rotation of a container according to claim 5, wherein
   said proportional gain is determined based on an optimum control theory provided that both the deviation between the target rotation angle of said container and the rotation angle of said container, and the angle of said lifting attachment member are converged to be zero.

8. A device for controlling the rotation of a container according to claim 6, wherein
   said proportional gain is determined based on an optimum control theory provided that both the deviation between the target rotation angle of said container and the rotation angle of said container, and the angle of said lifting attachment member are converged to be zero.

9. A method for controlling the rotation of a container used for a crane which includes a jib having a jib point from which a container is hung via a lifting attachment member and a rope member, said container being rotated by rotating an end of said rope member supported at said lifting attachment member side using a rotation motor disposed at said lifting attachment member, said method comprising the steps of:

computing a motor control command value based on a predetermined equation relating to variables of state which express rotational movement of said lifting attachment member and said container, a target rotation angle of said container, and the motor control command value for operating said rotation motor;

driving said rotation motor based on the motor control command value, and

performing a feedback control on the variables of state so that the rotation angle of said container matches the target rotation angle of said container.

10. A method for controlling the rotation of a container used for a crane which includes a jib having a jib point from which a container is hung via a lifting attachment member and a rope member, said container being rotated by rotating an end of said rope member supported at said lifting attachment member side using a rotation motor disposed at said lifting attachment member, said method comprising the steps of:

obtaining a rotation angle of said container;

obtaining a rotation angle of said lifting attachment member;

computing a motor control command value based on a predetermined equation relating to a deviation between a predetermined target rotation angle of said container and the rotation angle of said container, an angle of said lifting attachment member, and the motor control command value for operating said rotation motor;

driving said rotation motor based on the motor control command value, and

performing a feedback control on the rotation angle of said container and the angle of said lifting attachment member so that the rotation angle of said container matches the target rotation angle of said container.

Drawing