Method for controlling a crane
View Patent ↗The invention relates to a method for controlling a crane, the method comprising defining, at each time, the distance (s) the crane moves before stopping and without swinging of the load fastened to it by summing up a stopping distance (s 1 ), which is calculated on the basis of the internal target velocity, i.e. the velocity which the control of the algorithm implementing this has after the stored velocity changes are entirely implemented, by using the selected deceleration ramp; and a distance (s 2 ), which is calculated on the basis of stored velocity change requests stated before the stopping decision and on the basis of remaining performance times.
1. A method for calculating a distance in which a crane is stopped, the method comprising:
giving velocity requests as control sequences from a crane control system to crane drives and reading and storing the velocity requests (Vref) in a control system,
each velocity request (Vref) is compared with the previous velocity request and, if the velocity request is changed, an acceleration sequence for the corresponding velocity change is formed and stored, after which,
summing the velocity changes defined by stored acceleration sequences after a given time interval and adding the obtained sum (dV) to the previous velocity request to achieve a new velocity request (Vref 2 ), which is set as a new control and velocity request for the crane drives, and
performing some of the velocity changes defined by the summed acceleration sequences at a definition time of each acceleration sequence and performing the rest of them as delayed,
defining, at any given time, a distance (s) the crane moves before stopping and without swinging of the load fastened to it by summing up the following calculations:
a) stopping distance (s 1 ), which is calculated on the basis of, a velocity at which the control of an algorithm implementing this ends, when the stored velocity changes are entirely implemented, by using a selected deceleration ramp, and
b) a second distance (s 2 ), which is calculated on the basis of stored velocity change requests stated before a stopping decision, and on the basis of remaining performance times.
2. A method as claimed in claim 1 , wherein when decelerating a target velocity of point a), a third distance (s 3 ) caused by preventing the load from swinging, calculated on the basis of the part of the velocity control that differs from the deceleration ramp and being travelled by the crane when the swinging of the load caused by the actual deceleration ramp is damped with this differing velocity control is added to the calculation result.
3. A method as claimed in claim 1 , further comprising placing the stored velocity changes in a two-element table, whereby the velocity change which is to be carried out after a certain oscillation time is stored in the first element and the time, after which the velocity change or changes of the first element are carried out, is stored in the second element.