Crane control device

An object of this invention is to improve safety in a crane. A boom control signal .alpha.r and a winch control signal .beta.r are simultaneously outputted to, respectively, a boom drive portion and a winch drive portion of a driving portion 30 for obtaining, respectively, target values Xr, Yr, with current working radius X and lift Y that vary according to the flexure of boom 4 as feedback amounts, thereby a boom hoisting angle and a rope length being controlled simultaneously.

TECHNICAL FIELD 
The present invention relates to a device for controlling the boom hoisting 
angle and the length of a wind-up rope such that the working radius of the 
crane or its lift have desired fixed values. 
BACKGROUND ART 
When a crane is performing a so-called ground-departing operation, it is 
desirable that the crane is operated such that the working radius 
indicating the horizontal distance from the rotation center of the crane 
to the tip of the boom is a desired fixed value. 
However, when departing from the ground, the load acting on the boom 
increases as the hook on which the load is suspended is raised, causing 
the boom to flex and thereby increasing the working radius. Conversely, 
when performing an operation such as pouring fresh concrete, the suspended 
load decreases, thus decreasing the boom load and so decreasing the 
working radius. 
Accordingly, when performing operations in which the flexure of the boom 
fluctuates as described above, the exercise of control such as to maintain 
the working radius at a fixed value is desirable from the standpoint of 
increasing ease of working by improving the accuracy of tracking and also 
from the standpoint of improving safety by preventing accidents involving 
contact due to flow of the load. 
In some cases, cranes are used to perform horizontal movement operations in 
which the suspended load is shifted in the horizontal direction while 
maintaining the lift indicating the vertical distance from the ground to 
the hook at a fixed value. 
In such cases also, the amount of boom flexure fluctuates with the 
horizontal movement of the suspended load, so exercise of control such as 
to keep the lift fixed irrespective of such fluctuations in the flexure of 
the boom is desirable both to improve ease of working as mentioned above 
and to improve safety. 
Conventionally therefore arrangements have been made to compensate for 
fluctuation in the working radius produced by fluctuation in boom flexure 
by calculating the amount of flexure produced in the boom and by varying 
the boom hoisting angle in accordance with the results of this calculation 
(Japanese Patent Publication Sho.59-26599, Laid-Open Japanese Patent 
Application Hei. 1-256496, and Laid-Open Japanese Patent Application 
Hei.3-284598, etc). 
However, although the prior art, in which only the boom hoisting angle was 
changed in order to remove fluctuations of the working radius, did indeed 
succeed in removing fluctuations of the working radius itself it tended to 
produce concurrent fluctuations in lift, sometimes resulting in the 
dangerous condition that the suspended load might spring up abruptly in 
combination with raising of the boom. 
Also, similar problems regarding safety were produced when the prior art 
was applied to performing operations in which the lift must be kept at a 
fixed value. 
The present invention was made after considering the above circumstances, 
and its object is to perform in a safe manner an operation that advances 
by varying the lift while keeping the working radius constant or an 
operation that advances by varying the working radius while keeping the 
lift constant. 
DISCLOSURE OF THE INVENTION 
Accordingly, the present invention comprises boom drive means for changing 
a boom hoisting angle in response to an input drive instruction; winch 
drive means for changing a rope length of the wind-up rope from a tip of 
the boom to a hook in response to the input drive instruction; and control 
means for outputting drive instructions respectively to the boom drive 
means and winch drive means such as to effect a prescribed operation in 
which a lift, indicating the vertical distance from the ground to the 
hook, is varied, while maintaining the working radius, indicating the 
horizontal distance from the rotation center of the crane to the boom tip, 
at a fixed value. 
Also, the present invention comprises boom drive means for changing the 
boom hoisting angle in response to an input drive instruction; winch drive 
means for changing the rope length of the wind-up rope from the boom tip 
to the hook in response to an input drive instruction; and control means 
for outputting drive instructions respectively to the boom drive means and 
winch drive means such as to perform a prescribed operation by varying the 
working radius indicating the horizontal distance from the rotation center 
of the crane to the boom tip while maintaining the lift indicating the 
vertical distance from the ground to the hook at a fixed value. 
With such a construction, according to the present invention, as shown in 
FIG. 1, the hoisting angle .alpha. of boom 4 is varied in response to a 
drive instruction .alpha.r that is input to boom drive means 30. 
In contrast, rope length .beta. of the wind-up rope 8 from the boom tip 4a 
to hook 9 is varied in response to drive instruction .beta.r that is input 
to winch drive means 30. 
Control means 20 outputs drive instructions .alpha.r, .beta.r to the boom 
drive means 30 and winch drive means 30 such as to perform a prescribed 
operation while maintaining the working radius X indicating the horizontal 
distance from the rotation center of the crane to the boom tip 4a at a 
fixed value, and varying the lift Y indicating the vertical distance from 
the ground to hook 9. 
Alternatively, control means 20 outputs drive instructions .alpha.r, 
.beta.r to the boom drive means 30 and winch drive means 30 such as to 
perform a prescribed operation while maintaining lift Y at a fixed value 
and changing the working radius X.

BEST MODE FOR CARRYING OUT THE INVENTION 
An embodiment of a crane control device according to the present invention 
is described below with reference to the drawings. 
FIG. 1 is a block diagram illustrating the overall layout of the 
embodiment; in broad terms it consists of a sensor unit 15 arranged on the 
crane and comprising sensors 10 etc that detect the amounts of conditions 
necessary for control, a control unit 20 that inputs the detected values 
of sensor unit 15 and that generates control signals .alpha.r, .beta.r for 
drive control of the boom 4 and winch, and a drive unit 30 that inputs 
control signals .alpha.r, .beta.r that are output from control unit 20 and 
that drives by hydraulic pressure the boom and winch of the crane, 
performing for example processing such as conversion from the required 
electrical signals to hydraulic signals. 
FIG. 3 is a side view showing the external appearance of crane 1 employed 
in the embodiment; as shown in this Figure, it illustrates a condition in 
which the bottom mechanism is arranged on the ground by means of an 
outrigger 3. At the top of the bottom mechanism, there is freely rotatably 
arranged an upper rotary element 2 constituting a revolver frame; a boom 4 
is freely rotatably journalled by means of a rotary pin on this rotary 
element 2 such that boom 4 can move vertically. 
The hoisting angle .alpha. of boom 4 is detected by means of a prescribed 
boom hoisting angle sensor 10 such as a variable resistor or rotary 
encoder mounted on the rotary pin. Boom 4 is driven by an actuator 
constituted by a hydraulic cylinder 5; a detailed description of the 
construction of the boom drive unit that drives boom 4 will be given 
later. 
A wind-up rope 8 provided with a hook 9 at its tip is arranged on boom 4 so 
as to be free to wind up or lower hook 9, by means of a plurality of guide 
sheaves including a guide sheave 7 that is arranged at the top of boom 4. 
A prescribed suspended load 6 is engaged by hook 9. 
The distance between the position 4a of the tip of boom 4 and the center 
position 9a of hook 9 below it is defined as rope length .beta.. Rope 
length .beta. is detected by a prescribed rope length sensor 11 such as a 
rotary encoder that outputs rope length .beta. by detecting rotation of 
sheave 7. Winding up and lowering of winding-up rope 8 is effected by an 
actuator constituted by hydraulic motor 40 (see FIG. 1); the details of 
the construction of the winch drive unit will be described later. In this 
embodiment, working radius X, which is the horizontal distance between 
rotation center 1a of crane 1 and the center position 9a of the hook, is 
taken as a control variable, and lift Y, which is the vertical distance 
between the ground and the center position 9a of the hook is taken as a 
control variable. If the height yt of the boom tip position 4a is known, 
lift Y can easily be obtained by adding rope length .beta. to this yt. 
Also, in this embodiment, a crane is assumed whereof the length L of boom 4 
can be varied; this boom length L is detected by a boom length sensor 12 
(see FIG. 1). It may be noted that the present invention could of course 
be applied to a crane with a fixed boom length L; in this case, the boom 
length L is known, so there is no need to provide a boom length sensor 12. 
Also, as shown in FIG. 1, on hydraulic cylinder 5 there are arranged 
pressure sensors 13, 14 to detect the load F applied to boom 4 and to 
detect the pressure of the pressurized oil of the oil chamber of hydraulic 
cylinder 5. Pressure sensor 13 is a sensor that detects the head pressure 
PH of retraction chamber 5a of cylinder 5; pressure sensor 14 is a sensor 
that detects the bottom pressure PB of expansion chamber 5b of cylinder 5. 
As shown in FIG. 1, the detected values .alpha., .beta., L and PH, PB of 
boom hoisting angle sensor 10, rope length sensor 11, boom length sensor 
12 and pressure sensors 13 and 14 are input to control unit 20. 
FIG. 2 is a control block diagram of the control block constituted by 
sensor unit 15 and control unit 20 shown in FIG. 1; as shown in this 
Figure, first of all, the load F acting on boom 4 is calculated and 
detected by load detection unit 20 using the outputs PH, PB of pressure 
sensors 13, 14. 
Incidentally, when the flexure of boom 4 changes, working radius X changes 
in response to this change. Likewise, boom tip height yt also changes in 
response to the boom flexure. 
It is known that the boom flexure changes with the boom hoisting angle a, 
boom load F and boom length L as parameters. There is therefore a 
prescribed correspondence relationship indicated by function f shown below 
between working radius X and these parameters .alpha., F and L. 
EQU X=f(.alpha.,F,L) (1) 
Likewise, there is a prescribed correspondence relationship indicated by 
function g between the boom tip height yt and the above parameters 
.alpha., F and L. 
EQU yt=g(.alpha.,F,L) (2) 
The correspondence relationship between these parameters .alpha., etc. and 
working radius X and the correspondence relationship between these 
parameters .alpha., etc and boom tip height yt can be determined 
beforehand by experiment or simulation, etc and is stored in prescribed 
memory in the form of a calculation formula or in the form of a table. 
In this way, the current working radius X taking into account the flexure 
of boom 4 can be calculated from the correspondence relationship indicated 
by formula (1) above, and the current boom tip height yt taking into 
account the flexure of boom 4 can be calculated from the correspondence 
relationship indicated by formula (2) above. 
Now boom 4 and the winch are driven by operation of operating levers etc by 
the operator of crane 1 and a target value Xr of working radius X 
corresponding to such lever operation etc is input to control unit 20 and 
a target value Yr of lift Y is input to the same control unit Yr. 
Coordinate conversion section 25 calculates the current working radius X, 
which is the value of the function corresponding to function f by 
substituting the detected values .alpha. and L of sensors 10 and 12 that 
are currently input, and the calculated value F of load detection section 
21 into formula (1). In the same way, the current boom tip height yt, 
which is the function value corresponding to function g, is calculated by 
substituting the input detected values .alpha. and L of sensors 10 and 12, 
and the calculated value F of load detection section 21, into formula (2). 
In addition, the current lift Y is calculated by adding the detected value 
.beta. of the rope length sensor 11 that is currently input to boom tip 
height yt that is thus calculated. 
When this is done, the deviation .DELTA.X between the working radius target 
value Xr that is currently input as operating output of an operating lever 
or the like and the current working radius X (feedback value) that is 
calculated by coordinate conversion section 25, and this working radius 
deviation .DELTA.X is input to deviation coordinate conversion section 22. 
In the same way, the deviation .DELTA.Y between the lift target value Xr 
that is currently input as operating output of an operating lever or the 
like and the current lift Y (feedback amount) calculated by coordinate 
conversion section 25 is found and this lift deviation .DELTA.Y is input 
to deviation coordinate conversion section 22. 
Deviation coordinate conversion section 22 uses the input working radius 
deviation .DELTA.X, the lift deviation .DELTA.Y, the detected value a of 
boom hoisting angle sensor 10, and the detected value L of boom length 
sensor 12 to calculate the deviation .DELTA..alpha. of the boom hoisting 
angle corresponding to working radius deviation .DELTA.X, and to calculate 
the deviation .DELTA..beta. of the rope length corresponding to the 
working radius deviation .DELTA.X and lift deviation .DELTA.Y. 
Boom 4 of crane 1, having a prescribed length L, is rotated with prescribed 
angular velocity d.alpha./dt, so the velocities dX/dt and dY/dt of the tip 
co-ordinate position of boom 4 can in general be found by the angular 
velocity d.alpha./dt of the axis of rotation of boom 4, boom length L and 
the Jacobian matrix. Consequently, the deviation .DELTA..alpha. of the 
boom hoisting angle can be found as follows, using the tip co-ordinate 
position deviation .DELTA.X, boom length L and the inverse Jacobian matrix 
. 
EQU .DELTA..alpha.=-(.DELTA.X/(L.multidot.sin .alpha.)) (3) 
In the same way, the rope length deviation .DELTA..beta. can be found by 
the following formula (4). 
EQU Db=(.DELTA.X/tan .alpha.)+.DELTA.Y (4) 
Deviation coordinate conversion section 22 calculates boom hoisting angle 
deviation .DELTA..alpha. by substituting the currently input deviation 
.DELTA.X and detected value a etc into formula (3) above and calculates 
rope length deviation .DELTA..beta. by substituting deviation .DELTA.X and 
detected value a etc that are currently input into formula (4) above. 
In this way, when the boom hoisting angle deviation .DELTA..alpha. has been 
calculated, this deviation .DELTA..alpha. is input to deviation angle 
control section 23 and this deviation angle control section 23 calculates 
and generates a control signal .alpha.r such as to make this deviation 
.DELTA..beta. zero, and this is then output to the boom control section of 
drive unit 30. This calculated rope length deviation .DELTA..beta. is also 
input to rope length control section 24 and this rope length control 
section 24 calculates and generates a control signal .beta.r such as to 
make this deviation .DELTA..beta. zero, and this is output to the winch 
drive section of drive unit 30. 
Control signal .alpha.r is processed by a boom drive section that is built 
around a boom hoisting flow rate control valve 34. 
First of all, control signal .alpha.r is supplied to solenoid 31a of 
electromagnetic proportional pressure control valve 31 for decreasing the 
boom hoisting angle or is supplied to solenoid 32a of electromagnetic 
proportional pressure control valve 32 for increasing the boom hoisting 
angle. Control valve 31 or 32 is thereby actuated, causing a hydraulic 
signal of pressure corresponding to the input electrical signal ar to be 
applied to pilot port 34a or 34b of flow rate control valve 34. 
Pressurized oil discharged from a charging pump 37 is supplied to control 
valves 31 and 32. 
If now we assume that control signal .alpha.r indicates "boom lowering", 
control valve 31 for lowering is actuated, and flow rate control valve 34 
is shifted to valve position 34c corresponding to the magnitude of control 
signal .alpha.r; this causes pressurized oil discharged from hydraulic 
pump 33 for raising or lowering to be supplied to retraction chamber 5a of 
hydraulic cylinder 5 with a flow rate corresponding to valve position 34c. 
As a result, boom 4 is lowered in accordance with control signal .alpha.r, 
and deviation .DELTA..alpha. is made zero. 
Also, if control signal .alpha.r is indicating "boom raising", in the same 
way, the corresponding control valve 32 is actuated, causing flow rate 
control valve 34 to move to valve position 34d corresponding to the 
magnitude of control signal .alpha.r, with the result that pressurized oil 
discharged from hydraulic pump 33 for raising and lowering is supplied to 
extension chamber 5b of hydraulic cylinder 5 with a flow rate 
corresponding to this valve position 34d. As a result, boom 34 is raised 
corresponding to control signal .alpha.r, and deviation .DELTA..alpha. is 
made zero. 
In contrast, control signal .beta.r is processed by the winch drive 
section, which is built around winch winding-up or lowering flow rate 
control valve 39. Control signal .beta.r is supplied to solenoid 35a of 
electromagnetic proportional pressure control valve 35 for winding up or 
solenoid 36a of like pressure control valve 36 for lowering. By this 
means, control valve 35 or 36 is actuated, causing a hydraulic signal of 
pressure corresponding to the input electrical signal br to be supplied to 
pilot port 39a or 39b of flow rate control valve 39. 
Pressurized oil discharged from charging pump 37 is supplied to control 
valves 35, 36. 
If now control signal .beta.r is indicating "winch winding up", control 
valve 34 for winding up is actuated, causing flow rate control valve 39 to 
be moved to valve position 39c corresponding to the magnitude of control 
signal .beta.r, with the result that pressurized oil discharged from 
hydraulic pump 38 for the winch is supplied to the winding-up rotating 
side of hydraulic motor 40, with a flow rate corresponding to valve 
position 39c. 
As a result, wind-up rope 8 is wound up corresponding to control signal 
.beta.r, and deviation .DELTA..beta. is made zero. 
If control signal .beta.r is indicating "winch lowering", in the same way, 
the corresponding control valve 36 is actuated, causing flow rate control 
valve 39 to be shifted to valve position 39d corresponding to the 
magnitude of control signal .beta.r, with the result that pressurized oil 
discharged from hydraulic pump 38 for the winch is supplied to the 
lowering rotational side of hydraulic motor 40 with a flow rate 
corresponding to valve position 39d. 
As a result, wind-up rope 8 is lowered corresponding to control signal 
.beta.r, and deviation .DELTA..beta. is made zero. 
Operation will now be described for the case where a so-called "ground 
breaking" operation is performed, in which for example a suspended load 6 
at the ground is gradually raised, when the operation is performed varying 
lift Y while maintaining the working radius X of crane 1 fixed. 
First of all, at the commencement of the ground breaking operation, it is 
desirable that the hook 9 should be set such that the weight of suspended 
load 6 comes directly under the point pin. 
The operator then performs processing, for example by operating a 
start-control switch, to input working radius X0 at the start of control 
to control unit 20 as target value Xr. In contrast, in the case of lift Y, 
the operator would input to control unit 20 a target value Yr that 
gradually changes with progress of the ground-breaking operation. 
Thereupon, the suspended load gets bigger while load 6 is getting closer to 
being raised in response to rope 8 being wound up by driving the winch 
corresponding to the Y direction instruction Yr. As a result, boom 4 
gradually flexes, causing working radius X to increase and the lift Y in 
the calculation to alter. 
Working radius X and lift Y that are changing with flexing of boom 4 in 
this way are calculated as described above by the coordinate conversion 
section 25. 
Boom control signal .alpha.r and winch control signal .beta.r for target 
values X0, Yr are thereupon generated by control unit 20, using as 
feedback values the current values X, Y which are changing with this 
flexure; these control signals .alpha., .beta.r are simultaneously output 
to the boom drive section and winch drive section of drive unit 30, 
thereby simultaneously controlling the boom hoisting angle and the rope 
length. 
As a result, a ground breaking operation in which suspended load 6 is 
raised can be carried out in a safe manner while keeping working radius X 
at a fixed value X0, without abrupt change of lift Y or causing flow of 
suspended load 6. 
Also, operation can likewise be carried out in a safe way when performing 
an operation in which the load of suspended load 6 is made smaller while 
load 6 is still suspended, for example as in the case of a raw concrete 
pouring operation. 
The action will now be described wherein conversely, operation is performed 
while varying the working radius X and keeping the lift Y of crane 1 
fixed, for example a horizontal movement operation, in which suspended 
load 6 is displaced in the horizontal direction. 
In this case, the operator performs processing, by for example operating a 
start-control switch, wherein the lift Y0 on start of control is input to 
control unit 20 as target value Yr. On the other hand, in the case of 
working radius X, processing is performed wherein target value Xr that 
progressively changes with progress of the horizontal movement operation 
is input to control unit 20. 
When this is done, boom 4 is driven in accordance with the X direction 
instruction Xr, and the load applied to boom 4 fluctuates corresponding to 
the change in the boom hoisting angle .alpha.. This causes the flexure of 
boom 4 to gradually change, also changing working radius X and lift Y. 
Working radius X and lift Y that change in this way depending on the 
flexure of boom 4 are calculated as described above by the coordinate 
conversion section 25. 
Thereupon, boom control signal .alpha.r and winch control signal .beta.r 
for achieving target values Xr and Y0 are generated by control unit 20, 
using as feedback quantities the current values X, Y, which are changing 
with the flexure amount, and these are simultaneously output to the boom 
drive section and winch drive section of drive unit 30, so that the boom 
hoisting angle and rope length are simultaneously controlled. 
As a result, an operation of horizontal displacement in which suspended 
load 6 is displaced horizontally while maintaining lift Y at a fixed value 
Y0 can be performed safely. 
INDUSTRIAL APPLICABILITY 
As described above, with the present invention, the boom hoisting angle and 
the rope length can be controlled concurrently, using as feedback 
quantities the working radius and lift taking into account the current 
flexure of the boom, so an operation which advances by changing the lift 
while keeping the working radius at a fixed value or an operation which 
advances by changing the working radius while keeping the lift at a fixed 
value can be performed in a safe manner.