FI93201B - Method for controlling a crane - Google Patents

Description

93201

METHOD OF CONTROLLING THE CRANE

The invention relates to a method according to the preamble of claim 1 for controlling the movement of a crane. Here, the movement means both the movement 5 of the hoisting carriage or the movement of the carriage supporting the carriage or any other substantially horizontal movement for moving a member having a lifting rope suspension point or having a hoisting roller or the like on which the hoisting rope is wound.

The problem in controlling the movement of the load suspended from the hoisting rope 10 is to dampen the oscillation of the load as little as possible. Several solutions are known in the art that aim to stop the load without oscillation to the end point. For example, a patent method is known from patent application FI 920751, in which the control commands 15 given to the transmission motor of a crane are modified so that an acceleration period is formed when the control commands are given, which both execute the control commands and compensate for load fluctuations at the end of the transmission.

In the known solution, a differential equation describing the oscillation of a freely suspended load has been utilized. However, in order to facilitate the implementation of the practical 20, approximations have been made, as a result of which the control methods are not accurate if the length of the hoisting rope changes during the lifting movement. As a result, the known method is not fully able to compensate for the oscillation generated during the transfer movement.

The object of the invention is to provide a new crane control method with which the oscillation of the load can be compensated even when the length of the hoisting rope changes during the transfer movement. This is achieved by the measures defined in the characterizing part of claim 1.

In the manner according to the invention, changes in the length of the hoisting rope which affect the oscillation of the load are taken into account in the control. The control thus substantially monitors the actual oscillation of the load and changes the acceleration cycles of the motor accordingly. Fluctuations can also be compensated for when the • hoisting speed is high. With the method according to the invention, the load can be shifted without oscillation when the lifting height changes, even without speed feedback, by means of the acceleration periods defined in the control. The deceleration periods must be understood as corresponding to the 5 acceleration periods, only the direction of the change in speed in them is opposite.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of a crane, Figure 2 shows the crane acceleration cycles controlling the movement

15 According to Fig. 1, the crane hoisting carriage 1 is driven by its transfer motor on the support rails 2 in the direction x at the speed v determined by the steering. The load 4 depends on the hoisting rope 3 way. The length of the hoisting rope is calculated here as the distance from the suspension point in the trolley 1 to the load 4 center of gravity. As the load 4 oscillates, the hoisting rope 3 forms an angle 0 with the vertical direction y. Then the oscillation equation holds: 25 L * 0 "= - u - 2 * 0 '* L' - g * 0, (1) where L = hoisting rope length L / = hoisting rope length change rate, ie hoisting speed 0 = oscillation angle 0 '= oscillation angle 1. time derivative or swing velocity 0 '^ time derivative of oscillation angle 2. time derivative, i.e. oscillation angle oscillation u = wagon acceleration, i.e. wagon position 2. time derivative * 93201 g = fall acceleration = 9.81 m / s2.

Correspondingly, the equation T: 2 * ττ * ΐ / (L / g) holds for the time T of the oscillation period of the oscillation motion. (2) 5 if the hoisting rope length L remains constant during the transfer movement or control of ice from the equation (1), the second term on the right-side out because of the time derivative of cable length L 1 / is zero. In this case, the oscillation time T of the oscillation also remains constant. The oscillation equation (1) shrinks to the form: 10 L * 0 "= - u - g * 0, (3)

The solution of Equation (3) is a periodic function whose period length, i.e. the length of the oscillation period is T. If the motor of the forklift is controlled by equal acceleration cycles with a phase difference of T / 2, the oscillation caused by the change in acceleration must be compensated at the end of the acceleration cycles, for example in the solution according to patent application FI 920751. The situation according to Equation (3) is illustrated in Figure 2a), in which at time t = t0 an acceleration period 21 of magnitude ux begins at time t = t1. At time t = t2 = t0 + T / 2 20, a second acceleration period 22 begins, which is the length and duration of period 21 and ends at time t = t3 = t1 + T / 2. When decelerating, respectively, deceleration periods 23 and 24 are formed from times t4 and t6 to times t5 and t7, respectively. The dashed line shows the variation of the velocity v during the transfer 25.

Fig. 2b) illustrates the temporal variation of the oscillation angle uksesta under the effect of the acceleration periods of Fig. 2a). The dashed lines depict the oscillations caused by individual acceleration changes and the solid line depicts the 30 oscillation angles of the total load oscillation.

When, during the control according to Fig. 2a), the length of the hoisting rope changes when the load is lifted by the hoisting machine, the oscillation compensating effect of the control 4 93201 is not fully realized due to the fact that the lifting speed term of Equation (1) is not taken into account. .

In the method according to the present invention, the acceleration period of the motor is changed by adding a correction term which takes into account the effect of the lifting speed. For this purpose, the change in the length of the hoisting rope and the lifting speed of the load are determined. When the acceleration period 21 shown in Fig. 2 is corrected by the quantity uk 10 = -2 * 0 '* L', the control period U = Uj - 2 * 0 '* L' is obtained. When the value of U is placed in place of the acceleration variable u in Equation (1), Equation (1) returns to the form of Equation (3), where u has the value Uj. Since the correction term uk is a function of time depending on the time derivative of the oscillation angle and the length of the hoisting rope, the value of uk changes as a function of time.

Figures 3 illustrate the formation of an engine control cycle according to the invention. Figure 3a) shows the additional control 31 according to the correction term at the beginning of the transfer movement and the additional control 31 'at the end of the transfer movement, respectively. In the illustrated example, the lifting speed 20 is assumed to be constant during the control period, and to clarify the representation, the corrections made during both acceleration and deceleration are described as equal and starting at the moment when the oscillation angle and oscillation speed are zero.

25 Auxiliary control 31 affects the speed of the transfer carriage, increasing it beyond the desired (control command). Therefore, the additional control must be changed so that the target speed is reached. Since the complete after a period of half an opposite direction to the control section causes a corresponding amount oscillations can be 30, this thanks to sharing of Figure 3b) as described by the additional control into two parts 32 and 33, which is half lisäoh-justment 31 and the latter starts at the time when the previous part of the additional steering is in the opposite stage. The latter additional control is also in the opposite direction, i. if 35 the first additional control has to accelerate at a certain time, then the latter must decelerate correspondingly after time T / 2, II: 5 93201 when T is the prevailing oscillation period length. In this way, the additional controls 32 and 33 compensate for the change in speed caused by each other and at the same time compensate for the oscillation caused by the change in lifting height. The effect of the change in lifting height on the oscillation period 5 is taken into account by scaling as determined by Equation (2). Figure 3 c) illustrates the overall control periods 34 and 35 with solid lines and dashed lines acceleration periods 21-24 formed on the basis of the control.

Figure 4 shows a schematic control diagram for implementing the method according to the invention 10. Based on the control of the crane user, control cycles are formed in the unit 41, the output of which is fed to the correction unit 42, where the control is changed by the correction term uk. The input quantities of the unit 41 are the rope length L, the oscillation angle Θ. In addition to the correction term uk, the input quantities 15 of the unit 42 are the output quantity Uj of the unit 41 and the oscillation period length T. The correction term uk is formed in the unit 43 into which the angular velocity θ 'of the oscillation and the rope length change rate L' are introduced. The output quantity of the motor control period U is obtained from the unit 42 as a function of time.

The invention has been described above by means of an embodiment thereof. However, the disclosure is not to be construed as limiting, but embodiments of the invention are free to vary within the limits defined by the following claims.

Claims (3)

A method for controlling a hoist crane movement when the length (L) of the hoisting crane (3) is simultaneously changed, in which method the crane hoist movement is controlled by the acceleration interval (21-24) of the engine, which is determined on the basis of control commands and in which method length (L) of the lifting line is determined, characterized in that when the length of the lifting line (L) is changed, for the motor at least an additional acceleration interval (31-33,31'-33 ') is proportional to the lifting speed (at least) of the load 10 (4). L ') and the angular velocity (θ') at which the load (4) commutes. Method according to claim 1, characterized in that the extra acceleration intervals (31-33) are proportional to the product of the lifting speed (L ') of the load (4) and the angular velocity (θ') with which the load commutes. Method according to claim 1 or 2, characterized in that the extra acceleration interval is divided into two parts (32, 33) which are performed at intervals of half a commuting period (T / 2).