Method for controlling spreader in crane
View Patent ↗The invention relates to a method for controlling swaying and swinging of a spreader in a crane and the load attached thereto, the crane comprising: a trolley, hoist gears, hoisting ropes, on which the spreader is suspended from the trolley, auxiliary gears provided with motors and motor control equipment and auxiliary ropes, and in which method the forces of the auxiliary ropes exerted on the spreader are controlled by moving the auxiliary ropes using the auxiliary gears by means of torque instructions (T control ) obtained on the basis of the rope forces (F rope ) of the auxiliary ropes and the rotating speed data of the auxiliary gears, and whereby the rotating speed data of each auxiliary gear is formed gear-specifically as the difference between the measured rotating speed (n act ) of the auxiliary gear and the calculated rotating speed (n calc ) of the auxiliary gear.
1. A method for controlling swaying and swinging of a spreader in a crane and the load attached thereto, the crane comprising:
a trolley,
hoist gears provided with hoist drums placed in the trolley,
hoisting ropes arranged on the hoist drums, on which the spreader is suspended from the trolley and which are directed back to the trolley through sheaves arranged on the spreader,
the swaying and swinging being controlled by control equipment comprising:
four auxiliary gears provided with rope drums and including motors and motor control equipment placed in the trolley,
auxiliary ropes arranged on the rope drums of the auxiliary gears,
sheaves for the auxiliary ropes placed in the spreader, through which sheaves the auxiliary ropes passing obliquely from the rope drums of the auxiliary gears are directed to spaces arranged in the hoist drums for the auxiliary ropes,
said method comprising:
controlling forces exerted on the spreader by each auxiliary rope driven by a corresponding auxiliary gear based on torque instructions;
determining said torque instructions by means of control logic which receives force data of the corresponding auxiliary rope and rotating speed data of the corresponding auxiliary gear,
said control logic providing and maintaining the desired rope forces, controlling the rotation and the resistance of the swinging of the spreader using said motor in the corresponding auxiliary gear;
supplying the control logic with rotating speed data of the corresponding auxiliary gear equal to a difference between a measured rotating speed of the corresponding auxiliary gear and a calculated rotating speed of the corresponding auxiliary gear;
determining the calculated rotating speed based on at least the calculated rotating speed n g of the auxiliary gear caused by the diagonal geometry of the auxiliary ropes, where the hoisting ropes are vertically positioned and the auxiliary ropes are placed symmetrically, and where
n
g
=
a
3
*
(
a
1
-
H
(
a
1
-
H
)
2
+
a
2
2
-
1
)
*
dH
,
where
a 1 =a vertical geometry parameter of the auxiliary rope, and a 1 −H is the vertical projection of the diagonal part of the auxiliary rope,
a 2 =a horizontal geometry parameter of the auxiliary rope, the horizontal projection of the diagonal part of the auxiliary rope,
a 3 =a scale factor
H=hoisting height of the spreader, and
dH=hoisting speed of the spreader.
2. A method as claimed in claim 1 , wherein a calculated rotating speed n 1 of the auxiliary gear caused by the layer change of the auxiliary rope occurring on the hoist drum is added to the calculated rotating speed, whereby
n 1 =k×dH, where
k=a constant conversion factor, the value of which changes stepwise as a function of the hoisting height always when the auxiliary rope moves from one layer to another on the hoist drum, and
dH =hoisting speed of the spreader.
3. A method as claimed in claim 1 wherein a calculated rotating speed of the auxiliary gear caused by the listing or sway of the spreader occurring about an axis that is parallel with the axes of the hoist drums is added to the calculated rotating speed.
4. A method as claimed in claim 1 wherein a calculated rotating speed of the auxiliary gear deviating the spreader from the horizontal line that is parallel with the hoist drums caused by the different hoisting speed of the hoist gears is added to the calculated rotating speed.