CN104961051A - Grab bucket anti-oscillation method applicable to grab bucket crane - Google Patents

Abstract

The invention discloses a grab bucket anti-sway method applicable to grab bucket cranes. The anti-sway method is as follows: during the starting stage of the trolley, the acceleration of the trolley is actively controlled to accelerate, and the deviation S of the grab bucket increases gradually. When the grab bucket When the speed V ₂ of the trolley is the same as the speed V ₁ of the trolley, and the deviation angle θ of the grab does not exceed the deviation angle threshold θ′, the trolley turns into a uniform motion; during the uniform motion of the trolley, the deviation S of the grab bucket does not exceed the deviation Threshold S'; when the trolley stops, the acceleration of the trolley is actively controlled to decelerate, and the deviation S of the grab bucket gradually decreases. When the trolley stops, the deviation S of the grab bucket is less than the safety distance between the grab bucket and the pool wall. The advantage of the present invention is that the large mass and long swing period of the grab bucket are unfavorable factors in feedback anti-sway, but in active anti-sway, the large mass and long swing period reduce calculation, interference and other factors. The error, so that the anti-shake can be better realized and ensure the work efficiency.

Description

Anti-sway method for grabs applicable to grab cranes

technical field

The invention belongs to the technical field of cranes, and in particular relates to a grab bucket anti-sway method suitable for grab bucket cranes.

Background technique

Domestic waste grab crane (referred to as garbage crane) is one of the main operating equipment commonly used in domestic waste incineration power plants or processing sites. Its work is characterized by harsh environment, high temperature, high humidity, and corrosive gas in the workplace; fast production rhythm and high operating frequency. For this reason, the crane is required to run fast, to move forward or backward frequently, and to have short acceleration and deceleration time. However, since the grab is suspended on the trolley of the crane through a wire rope, the movement of the trolley is quite complicated, including the movement of the trolley itself and the movement of the trolley driven by the cart. The horizontal movement of the crane cart and trolley and the lifting and lowering of the lifting system will cause the grab to shake. If anti-sway measures are not considered, generally speaking, the faster the crane runs and the shorter the acceleration and deceleration time, the easier it is to sway. Longer wire ropes and heavy grab buckets result in longer shaking periods due to inertia, which reduces the influence of frictional force that hinders shaking, and thus is prone to large-scale shaking. The garbage crane works precisely when the running speed is fast, the acceleration and deceleration time is short, and the positioning requirements for grabbing and discharging materials are high. The steel wire rope connected to the grab bucket is long, and even if the grab bucket is empty, it has a large mass, so it is easy to produce Shaking and collision of facilities.

A large shake of the grab bucket may cause the grab bucket to collide with the wall of the garbage pool or other facilities, which may speed up the damage of the grab bucket and the pool wall, or cause a safety accident if it is serious. In order to prevent the impact, the running speed of the garbage crane has to be reduced, but the measures to reduce the speed will seriously affect the operating efficiency of the garbage crane.

The shaking of domestic garbage cranes is generally only guaranteed by the skills of the crane operators, so the operating efficiency of the garbage cranes has a lot to do with the skills of the operators. But even for skilled operators, it is generally impossible to maximize the ability of the garbage crane. Because the garbage crane is often operated in the operating room, there is sometimes a large distance between the operator and the garbage crane; in addition, the operator may be fatigued or distracted due to night shifts and other reasons; and this is extremely prone to collisions between the grab bucket and the pool wall Fault.

To realize the anti-sway of the garbage crane, it is generally considered to adopt a conventional closed-loop control system, that is, to stabilize the amount of sway, the closed-loop control is implemented on the amount of sway. The shaking of the grab is caused by the frequent start and stop of the cart and trolley, the sudden big and small acceleration and deceleration changes, and the high-speed lifting and lowering of the winch system. In order to stabilize the speed of the grab along the two directions of the cart and trolley tracks, it is necessary to implement closed-loop control on the speed of the grab.

However, there are two difficulties in the closed-loop control of the grab speed: According to the conventional method of closed-loop control, in order to stabilize the balance and position positioning of the two-direction speed of the grab, it is necessary to accurately detect the running speed of the two directions of the grab. The grab speed is compared with the given signal as a feedback quantity. However, the grab is suspended under the trolley through a wire rope, so it is difficult to detect its speed and position. Secondly, even if the speed of the trolley can be detected, since the grab is a long-period oscillation link, the response is slow and its position is constantly changing. It is also quite difficult to correct it. Figure 1 shows the transfer function of each link of the grab speed closed-loop control.

It is also possible to consider the deviation of the grab as the control target. The shaking of the grab bucket is the horizontal projection of the position deviating from the hoisting point of the trolley. Because the trolley is installed on the trolley, the movement of the trolley will drive the movement of the trolley and cause the deviation component S _X of the grab along the direction of the trolley track. And the trolley can move on the trolley, the movement of the trolley itself will cause the deviation component S _Y of the grab along the track direction of the trolley. S _X and S _Y are two vectors perpendicular to each other, and they synthesize the total deviation of the grab to the trolley. To control the deviation, it is necessary to detect the deviation S _X in the track direction of the cart and the deviation S _Y in the track direction of the trolley. However, it is quite difficult to directly and accurately detect these two data.

When the deviation of the grab bucket is not large, the bending of the suspension wire rope can be ignored, and the wire rope is regarded as always maintaining a straight line. In this way, S _X and S _Y can be calculated by detecting the angles θ _X and θ _Y of the wire rope and the vertical line in the two directions of the large and small car tracks.

However, although it is not difficult to detect θ _X and θ _Y , it is impossible to keep θ _X and θ _Y as the control target. Because in the feedback process, there is no way to directly control the grab itself that has deviated, the only way to control it is to control the trolley (including the movement of the trolley driven by the cart) to control the deviation angle. For example, when starting, the trolley moves, and the grab will inevitably deviate. If the feedback control system responds immediately to suppress the θ _X and θ _Y angles, then the movement speed of the trolley can only be reduced, which makes it impossible for the trolley to move effectively. .

The above control cannot be achieved by simple feedback control, and the existence of the deviation angle must be allowed, but a fixed deviation angle cannot be specified, because in the control system, the requirement of feedback control is to pursue the actual value of the control as close as possible to the target value , and the deviation value itself is not what the control wants to pursue, but should be eliminated eventually. This forms a paradox: anti-sway requires the elimination of the deviation angle, but the operation requires the existence of the deviation angle.

If it can be specified that a certain deviation angle is allowed, when the deviation angle amplitude is greater than the specified value, the control car tries to reduce the deviation angle amplitude, and at the end stage, the target deviation angle is specified as 0, then the control of the garbage crane can be achieved. Shake deviation angle is not too big. This realizes the anti-sway feedback control of the garbage crane. At present, some garbage cranes have adopted similar measures.

Therefore, different target control deviation angles must be set according to each stage of crane operation. But controlling the deviation angle can only be realized by controlling the speed and acceleration of the car. If feedback control is performed on these two quantities, the anti-shake effect on the grab is very small. The quantity that needs feedback can only be the deviation angle of the lifting rope, and the control link of the grab bucket deviation angle has an oscillation link, so it is extremely difficult to realize. Such anti-sway control is difficult to achieve the desired effect. Because if there is a limit to the deviation angle of the grab, then when the deviation angle is less than the value, the feedback control system should not intervene; and when the deviation angle reaches the limit value, the feedback control system should control the car so that the angle does not increase. big. From the perspective of the movement law of the simple pendulum, if the deviation angle to reach the target value does not change, the trolley can only move at exactly the same speed as the grab at that moment, and the deviation angle of the grab can also provide the grab with the right angle. This speed will do. And that's basically impossible. Because the above-mentioned feedback control does not take the grab speed as the feedback amount.

Therefore, such feedback control is only possible to limit the deviation angle within a range. According to the law of motion of a simple pendulum, the deviation angle will oscillate within this range, that is, it will keep shaking. Not only that. If the speed of the grab is too high when the deviation angle reaches the control limit value, it may also be unable to respond to the requirements of feedback control and exceed the target deviation angle due to the limitation of the acceleration performance of the trolley and the speed of the trolley. That is, there is still the possibility of getting out of control.

Also, if the deviation angle continues to increase, the feedback control system may control the trolley to decelerate significantly or even drive in the reverse direction, which will seriously affect the operating efficiency. Even if the deviation angle is limited within a certain range, the trolley may have to run at a small speed and with a small acceleration and deceleration force, that is to say, the crane does not play a good role in efficiency. Figure 2 shows the transfer function of each link in the closed-loop control of the grab deviation angle.

Of course, a correction link can also be added in the feedback loop. However, since what needs to be corrected is the large inertial oscillation link, it is extremely difficult to obtain good results.

Contents of the invention

The object of the present invention is to provide a grab bucket anti-sway method suitable for grab cranes based on the shortcomings of the above-mentioned prior art. The movement parameters of the trolley make the deviation angle of the grab bucket increase first, then keep the same, and then decrease during the whole process of starting, moving and stopping the trolley, thereby eliminating the periodic back and forth swing of the grab bucket.

The object of the present invention is realized by the following technical solutions:

An anti-sway method for grabs suitable for grab cranes, involving a trolley and a grab hoisted below the trolley via a wire rope, characterized in that the anti-sway method is: during the start-up phase of the trolley, actively control The acceleration of the trolley accelerates, and the deviation S of the grab increases gradually. When the speed V ₂ of the grab is the same as the speed V ₁ of the trolley, and the deviation angle θ of the grab does not exceed the deviation angle threshold θ ’, the trolley turns into a uniform motion; during the uniform motion of the trolley, the deviation S of the grab bucket does not exceed the deviation threshold S’; when the trolley stops, the trolley is actively controlled The acceleration decelerates, and the deviation S of the grab bucket gradually decreases. When the trolley stops, the deviation S of the grab bucket is smaller than the safety distance between the grab bucket and the pool wall.

The method of actively controlling the acceleration of the trolley is: according to the shaking period T of the grab bucket and the given speed V ₁ and acceleration a ₁ of the trolley, calculate when the trolley accelerates to a given speed V ₁ , Whether it is possible to make the grab and the trolley move synchronously and at _a constant speed, and at the same time, the deviation angle θ of the grab bucket does not exceed the deviation angle threshold θ′; Speed V ₁ , so that the grab and the trolley keep moving at a constant speed synchronously, and the deviation angle θ does not exceed the deviation angle threshold θ′; if not, modify the acceleration a ₁ of the trolley until the trolley accelerates When the given speed V1 is reached, the grab and the trolley can be moved synchronously and at _a uniform speed.

The formula for calculating the shaking period T of the grab bucket is:

T=2π(L/g) ^1/2

Wherein, L is the length of the wire rope suspended between the grab bucket and the trolley.

The method of actively controlling the acceleration of the trolley to decelerate is: according to the shaking period T of the grab bucket and the given speed V ₁ and acceleration a ₁ of the trolley, calculate whether the trolley can be decelerated to 0 Both the deviation angle θ and the speed of the grab bucket are reduced to 0; if possible, control the trolley to decelerate to stop under the acceleration a ₁ , so that the deviation angle θ and speed of the grab bucket are both reduced to 0; if If not, modify the acceleration a ₁ of the trolley until when the trolley decelerates to 0, both the deviation angle θ and the speed of the grab can be reduced to 0.

The deviation threshold S' is S'<Sp, where Sp is the safe distance that the grab is allowed to shake.

The advantage of the present invention is that the large mass and long swing period of the grab bucket are unfavorable factors in feedback anti-sway, but in active anti-sway, the large mass and long swing period reduce calculation, interference and other factors. The error, so that the anti-shake can be better realized and ensure the work efficiency.

Description of drawings

Fig. 1 is the transfer function schematic diagram of conventional speed feedback control in the prior art;

Fig. 2 is a schematic diagram of the transfer function of the grab deviation angle feedback control in the prior art;

Fig. 3 is a schematic diagram of the control flow of the active anti-sway control startup stage in the present invention;

Fig. 4 is a schematic flow chart of the stop phase of the active anti-sway control in the present invention.

Detailed ways

The features of the present invention and other relevant features are described in further detail below in conjunction with the accompanying drawings through the embodiments, so as to facilitate the understanding of those skilled in the art:

Embodiment: This embodiment specifically relates to a grab bucket anti-sway method suitable for grab cranes. A grab bucket is suspended below the trolley via a wire rope. For the grab bucket anti-sway, the anti-sway does not need to be completely Suppresses the amount of deviation of the grab. The anti-sway requirement is: in order to improve labor productivity, when the trolley is started, it is generally required to accelerate to full speed, and the grab is allowed to deviate at this time; then the trolley moves at full speed, and the grab is still allowed to deviate, but it is hoped The value does not exceed a small value, do not increase it, and do not have obvious front and rear alternate shaking; when the trolley decelerates and stops, the trolley must stop quickly and in time, seek the minimum sliding distance, and the grab must stop quickly when stopping Shaking, no forward deviation (that is, deviation in the negative direction) or small forward deviation. When approaching the pool wall, the forward deviation must not be greater than the safe distance between the grab bucket and the pool wall. The ideal state is that when the trolley quickly decelerates to 0, the deviation of the grab is also reduced to 0.

The shaking of the grab bucket has its own rules. In a large range, the motion of the grab bucket can be approximated by the motion of a single pendulum, so the motion of the grab bucket is actually predictable. If the active anti-sway of the grab is considered, better results can be achieved. From the given control parameters, the motion parameters (speed, acceleration) of the trolley can be known; according to the simple pendulum motion formula of the grab, the Future motion parameters (deviation value, speed, acceleration); as a simple pendulum, the grab has a long motion cycle and a large mass, so it is less disturbed by the environment. According to the manufacturing parameters of the garbage crane, according to the grab Calculating the law of motion and actively changing the speed and acceleration of the trolley can theoretically fully meet the working requirements of the garbage crane mentioned above.

For this reason, it can be calculated according to the motion formula of a simple pendulum. In the stage of starting acceleration, the acceleration is controlled with as much force as possible; in this stage, the deviation value is allowed to increase. In the stage of uniform motion, the goal is to control with the maximum speed movement; in this stage, the deviation value is required to keep a small value and not increase. In the stage of deceleration and stop, decelerate with as much force as possible. In this stage, the deviation value is required to decrease in coordination with the speed of the trolley. When the speed of the trolley is 0, the deviation value is also 0, which is an ideal state.

The above control methods are based on the single pendulum motion law of the grab in advance, through calculation, and actively control the motion parameters of the trolley to achieve the purpose of anti-shaking. During the whole process of starting, moving and stopping the trolley, the grab deviation angle first increases, then remains unchanged, and then decreases. Such a motion state eliminates the periodic back and forth swing of the grab bucket, and thus realizes the anti-shaking goal of the technology.

Therefore, as long as the trolley is actively controlled according to the single pendulum motion law of the grab bucket, the crane can work with ideal motion parameters. Of course, due to the influence of the environment and other factors, it is impossible for the grab to completely realize the shaking when it stops under the ideal speed and acceleration only by active anti-sway, but this kind of shaking can be slight, which is harmful to the safety of the crane and the crane. Efficient movement of is acceptable, or may be considered ideal.

The anti-shake is controlled separately according to the movement of the trolley along the direction of the cart track and along the direction of the trolley track. When the cart moves, the shaking along the direction of the cart track is controlled. Although the final object of control is the trolley, the actual control is the transmission system of the cart. When the trolley moves, the shaking along the track of the trolley is controlled, and the actual control is the transmission system of the trolley. The content and variables described below all refer to one of the systems. If two directions are required to control the two systems at the same time.

As shown in Figures 3 and 4, the grab anti-sway method applicable to the grab crane in this embodiment specifically includes the following steps:

(1) First measure the length L of the steel wire rope between the trolley and the grab, and then calculate ω=(g/L) ^1/2 according to the motion formula of the simple pendulum and the length L, and the shaking period of the grab is T= 2π/ω=2π(L/g) ^1/2 ;

When the trolley is started, the grab will inevitably produce a deviation S. If the trolley is accelerating uniformly, the calculation formula for the deviation S is: S=a ₁ L (1-cosωt) /g;

According to the shaking period T of the grab, and the given speed V ₁ and acceleration a ₁ of the trolley, the future motion parameters of the grab (deviation s, speed V ₂ , acceleration a ₂ ) can be calculated.

(2) As shown in Figure 3, during the start-up stage of the trolley, actively control the acceleration a ₁ of the trolley to accelerate the movement, and calculate whether the deviation S of the grab bucket can be kept within the deviation when the trolley accelerates to a given speed V ₁ The threshold S', or whether the deviation angle θ can be kept within the deviation angle threshold θ', so that the grab and the trolley perform synchronous and uniform motion, where the deviation angle threshold θ' is:

θ'=arcsin(S'/L)

If it is possible, control the trolley to accelerate to a given speed V ₁ under the acceleration a ₁ , so that the grab and the trolley keep moving synchronously and at a constant speed, and the deviation angle θ does not exceed the deviation angle threshold θ′;

If not, modify the acceleration a ₁ of the trolley until when the trolley accelerates to a given speed V ₁ , the deviation angle θ of the grab does not exceed the deviation angle threshold θ′, and the grab and the trolley perform synchronous and uniform motion;

It should be noted that the deviation threshold S' and the deviation angle threshold θ' are artificially specified values, which are determined by the grab crane designer or user's tolerance for the shaking of the grab bucket; the limit of S' is the design value of the grab crane. The rocking control safety distance Sp stipulated at the time or specified by the user of the grab crane. For the garbage grab crane, Sp is the distance between the grab near the pool wall and the pool wall when the trolley is at the limit position closest to the garbage pool wall. Therefore, there must be :

S′<Sp

Correspondingly, θ' is related to the height of the grab bucket, which can be calculated by θ=arcsin(S/L):

θ'=arcsin(S'/L)

When S′>Sp, it cannot be guaranteed that the garbage grab will not collide with the pool wall;

In fact, S′<Sp is the minimum requirement for grab anti-sway. Although it can ensure the safety of operation, there is still a big gap for the efficient operation of grab cranes. Generally, S′ cannot be stipulated according to this;

Theoretically speaking, according to the parameters such as V ₁ and a ₁ of the operation of the grab, the single pendulum motion formula is used to calculate the future motion of the grab; the value of S′ expresses the accuracy of the control target, so the value of S′ It can also be artificially specified, and its selected value range is between 0 and Sp; but due to measurement errors and calculation errors, from an industrial application, if the value of S' is controlled too low, it will increase the equipment cost, and it may also reduce the cost of the crane. Operating efficiency; according to the requirements of use, S' can generally be selected between 0.1Sp and 0.5Sp;

For cranes that do not have a specified safety distance Sp, in the grab anti-sway, Sp can generally be calculated as the distance that the cart or trolley moves in 0.2 to 5 seconds at the highest operating speed. If L is large, the value can be made larger; if L is small, the value can be made smaller; for cranes whose L value changes greatly, Sp can also be a variable, which will not hinder the calculation of active anti-sway;

(3) Afterwards, the trolley turns into a uniform motion at a speed of V ₁ (in general, it should be the full speed of the trolley). During this uniform motion, the deviation S does not exceed the deviation threshold S′;

(4) As shown in Figure 4, similarly, at the stop stage of the trolley, actively control the acceleration a ₁ of the trolley to decelerate, and calculate whether the deviation angle θ and speed of the grab can be reduced when the deceleration of the trolley is 0 is 0;

If possible, control the trolley to decelerate to stop under the acceleration a ₁ , so that the deviation angle θ and speed of the grab bucket are both reduced to 0;

If not, modify the trolley acceleration a ₁ until when the trolley decelerates to 0, both the deviation angle θ and the speed of the grab can be reduced to 0.

Claims (5)

1. one kind is applicable to the grab bucket anti-shake method on grab crane, relate to dolly and be lifted on the grab bucket below described dolly through steel rope, it is characterized in that described anti-shake method is: when described dolly start-up period, described in ACTIVE CONTROL, dolly acceleration/accel accelerates, described grab bucket bias S increases, gradually as the speed V of described grab bucket ₂with described little vehicle speed V ₁identical, and when described grab bucket distortion angle θ is no more than distortion angle threshold value θ ', make described dolly proceed to uniform movement; Described dolly is in uniform movement process, and described grab bucket bias S is kept for no more bias threshold value S '; When described dolly shutdown phase, described in ACTIVE CONTROL, dolly acceleration/accel slows down, and described grab bucket bias S reduces gradually, and when described dolly stops, described grab bucket bias S is less than the safety distance between described grab bucket and pool wall.

2. a kind of grab bucket anti-shake method be applicable on grab crane according to claim 1, is characterized in that the method that dolly acceleration/accel described in ACTIVE CONTROL carries out accelerating is: according to the slosh cycle T of described grab bucket and the given speed V of described dolly ₁with acceleration/accel a ₁, calculate when described dolly accelerates to given speed V ₁time, whether described grab bucket and described dolly can be made to carry out synchronous uniform velocity motion, the distortion angle θ of described grab bucket is simultaneously no more than distortion angle threshold value θ '; If of course, then control described dolly at acceleration/accel a ₁under accelerate to given speed V ₁, make described grab bucket and described dolly keep synchronous uniform velocity to move, and distortion angle θ is kept for no more distortion angle threshold value θ '; If cannot, then revise described dolly acceleration/accel a ₁, until when described dolly accelerates to given speed V ₁time, described grab bucket and described dolly can be made to carry out synchronous uniform velocity motion.

3. a kind of grab bucket anti-shake method be applicable on grab crane according to claim 1, is characterized in that the computing formula of the slosh cycle T of described grab bucket is: T=2 π (L/ g) ^1/2

Wherein, L is the rope capacity hung between described grab bucket and described dolly.

4. a kind of grab bucket anti-shake method be applicable on grab crane according to claim 1, is characterized in that the method that dolly acceleration/accel described in ACTIVE CONTROL carries out slowing down is: according to the slosh cycle T of described grab bucket and the given speed V of described dolly ₁with acceleration/accel a ₁, calculate when described dolly decelerates to 0, the distortion angle θ of described grab bucket and speed whether can be made all to be reduced to 0; If of course, then control described dolly at acceleration/accel a ₁under be decelerated to stopping, making the distortion angle θ of described grab bucket and speed all be reduced to 0; If cannot, then revise described dolly acceleration/accel a ₁, until when described dolly decelerates to 0, the distortion angle θ of described grab bucket and speed all can be reduced to 0.

5. a kind of grab bucket anti-shake method be applicable on grab crane according to claim 1, is characterized in that described bias threshold value S ' is S ' <Sp, and in formula, Sp is the safety distance that grab bucket allows to rock.