JPS6131034B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a steady rest control method for a rope-suspended crane. Automatic operating systems for overhead cranes are gradually being put into practical use to improve the work environment and save labor. Various methods have been proposed to design this system, but using a fixed pattern control method,
The current mainstream method seems to be to use a steady rest.
In this fixed pattern control method, the pattern is generally determined on the assumption that the rope length is constant during movement. However, even with a small lift such as an overhead crane, the hoisting time results in a loss of cycle time. Therefore, in order to eliminate this lost time, it is necessary to start hoisting the hoisted load and traveling at the same time, and in fact, this method of operation is normally used in overhead cranes operated by the operator. The present invention proposes a control method that can prevent steady movement in the automatic operation system of a rope suspension crane that starts hoisting and traveling at the same time as described above. First, a basic steady rest method from the past will be explained. As shown in Figure 1, a simple pendulum model is considered as a model of an overhead crane. 1 is a trolley, 2 is a suspended load, and ν is the running or traversing speed of the trolley 1. If the acceleration of the trolley 1 is α, the equation for the swing angle θ of the suspended load is as follows. θ¨+2〓θ〓+gθ=−α……(1) By the way, in the conventional constant pattern control method, the acceleration α is set to a constant value (a ₀ ), and the rope length is set to a constant value (
₀ ), the second term in equation (1) is omitted, and the motion of the pendulum is expressed as θ+gθ=−a ₀ ……(2).
This is a step response of a degree-of-freedom system. When this result is expressed in a phase plane, it becomes orbit 3 shown in FIG. In other words, the trajectory is circular with the point (-α/g, 0) as the center and radius α/g, and if acceleration is stopped just after completing one revolution, the vehicle can be rested while traveling at a constant speed. On the other hand, when the acceleration α is kept constant (α ₀ ), the trolley is accelerated and at the same time it is hoisted at a constant speed (=-
Starting from c), equation (1) becomes an equation for a negatively damped one-degree-of-freedom system, and its trajectory becomes the four spiral trajectory shown in FIG. If this state continues, the system will diverge, so the time when the orbit enters the fourth quadrant from the first quadrant.
At t ₁ (point Pθ _P , 0)), hoisting is stopped and the deceleration is switched to constant deceleration. In this case, the length of the rope will be constant and the orbit will be a circular orbit, so after half a period, the origin will be reached at t ₂ and steady rest will be possible. Note that this deceleration d ₀ (constant) is determined by d ₀ =θ _P ·g/2 (3). At this time, the amount of hoisting is ct ₁ , the rope length during steady running is = ₀ - ct ₁ , and the time t ₂ is t ₂ = t ₁ + 1/2T (T
=2π√). When decelerating to stop the trolley, the above procedure may be reversed. The overall trolley speed pattern is shown in FIG. By the way, the above speed pattern is easy to control, but since the running/traversing speed is accelerated and then decelerated, the constant running speed becomes low, and hoisting is stopped midway, so it is difficult to shorten the overall cycle time. There is a problem considering the purpose. As will be described in detail below, the present invention proposes a steady rest control method using a speed pattern that eliminates wasteful deceleration, although the speed pattern is a little complicated. The equation of motion of the suspended load of a crane in which the trolley is accelerated while hoisting the suspended load is expressed by equation (1) above. Therefore, the method of accelerating the trolley at the same time as hoisting of the suspended load is started at a constant speed is the same as the method described above, but in the present invention, the trolley acceleration α is set as a linear function of time, and this is expressed as follows. Expressed in α=a ₀ +a ₁ t...(4) Here, a ₁ is the amount of jerk. The jerk amount is an acceleration component that changes in proportion to time. At this time, if the winding speed=-c (constant), then equation (1) becomes θ¨-2cθ=+gθ=-(a ₀ +a ₁ t)...(5). However, rope length = ₀ - ct. The solution to equation (5) is expressed as the sum of the step response and ramp response for a linear one-degree-of-freedom system with a negatively damped variable coefficient,
The phase plane trajectory of a crane's hoisted load, which is accelerated with hoisting and jerking, is generally as shown in Figure 4. Figure 4 A is ₀ = 10m, c = 0.3m/S,
This is the trajectory when a ₁ = 0.003 m/S ³ is given when a ₀ = 0.2 m/S ² , and Figure 4B shows the trajectory when a ₁ = 0.007 m/S 3.
This is the case for ^S3 . Therefore, if ₀ , c, a ₀ are determined in advance and a ₁ is given appropriately, (θ,
θ〓) can return to the origin in the n-th cycle. At this time, the method for determining the value of a ₁ mentioned above and the time t _s at which acceleration and winding are stopped and steady running begins is as follows. The solution of equation (5) is a series solution. It is expressed as θ(0)=θ〓(0)=0 as the initial condition.
Using

[Table] 〓…… (7)
cg

Claims (1)

[Claims] 1. In the automatic operation of a rope-suspended crane that hoists and simultaneously accelerates a hoisted load, the hoisting speed is kept constant and the acceleration is a linear function of time α=
Assuming A ₀ + a ₁ , using the constants a ₀ and _{a 1} at which the rope stops swinging, which were calculated in advance, and time t, the suspended load is hoisted at a constant speed until time t, and accelerated at an acceleration α, A rope-suspended crane rest control system characterized in that hoisting is stopped at time t and the hoisting is started at a constant speed, thereby swinging up the hoisted load. However, α is acceleration, a ₀ is constant acceleration, a ₁ is jerk amount, and t is time.