RU85890U1 - DEVICE FOR AUTOMATIC REDUCTION OF PENDULUM OSCILLATIONS OF A LOAD MOVED BY A CART OF A BRIDGE CRANE - Google Patents

Abstract

A device for automatically damping pendulum oscillations of a load suspended from a traveling mechanism of an overhead crane truck, containing a flexible suspension, an electric drive for the truck's moving mechanism, a load weight sensor, an intensity adjuster for a slave control system with an output signal (mechanism acceleration), integrator, division unit, adder, unit setting a constant (mt is the mass of the trolley), characterized in that, in order to increase the efficiency of damping oscillations due to the accuracy of determining the angle of deviation of the load and the use of devices to damp arising vibrations in the plane of movement of the trolley, the integrator is covered by negative feedback with the coefficient Ksv connected to the first adder, in addition, a second integrator is added with a single negative feedback supplied to the input of the first multiplier, to the other input of which a signal is determined using the signal from the weight sensor (proportional to the mass of the load mg), fed to the input of the divider, divided by a constant - mt is the mass of the trolley, the result is sent to the adder, where t addition with a constant equal to 1, the output of the adder is connected to the input of the multiplier, the signal from the output of the divider, which divides the constant equal to 9.81 (gravity acceleration), by the length of the suspension received from the length sensor, is received at the second input of the multiplier the output of the multiplier goes to the input of the first multiplier, the output of which is fed to the input of the first adder, which also receives the signal from the output of the intensity adjuster - supplied through a proportional amplifier with a gain of CT, the output of the second integrat

Description

The invention relates to the field of mechanical engineering and can be used to reduce the sway of a load suspended on a rope moved by overhead, gantry or portal cranes. The device is designed to work with AC and DC electric drives. The slave drive control system is implemented using a high-speed microprocessor controller.

The load attached with the suspension to the movement mechanism is a mathematical pendulum with a movable suspension point. When starting and braking the movement mechanism, the load suspension point moves with acceleration determined by the dynamic moment developed by the drive electric motor. In this case, the load under the action of inertia forces deviates from the equilibrium position in the direction opposite to the movement of the mechanism. After the drive reaches the set speed of the movement mechanism, the acceleration of the suspension point becomes equal to zero, and the load oscillations damp due to the action of resistance forces. The presence of fluctuations makes it difficult to accurately position the load.

There is a known method of damping oscillations and a device for its implementation (copyright certificate SU No. 640960, M. Cl. B66C 13/06 of 06/19/74), based on the creation of a force equal in magnitude and opposite directional force of movement resistance, which causes a deviation load from the vertical axis during movement. The created force is applied to the mechanism that causes the load to deviate and is proportional to its speed.

The operation of the device implementing the described control method is as follows: when the load approaches its stopping point, the damping circuit starts to work, with the help of which the moment of the drive device is created, changing according to the trapezoidal law. In the event of a deviation of the load, the movement device will move from one place to the side of the deviation of the cargo. When in the process of oscillation of the load, its deviation becomes sufficiently small, the correction circuit will be disabled.

The disadvantage of this method of calming the pendulum oscillations of the load is the need for additional time to damp the oscillations and use the maneuvers of the moving device.

Closest to the proposed invention is a device for limiting the swing of a load suspended on a trolley (copyright certificate SU 1364598 A1, M.C. B66C 13/06 of 01/07/08). The principle of operation of the device is to generate a feedback signal proportional to the rate of change of the angle of deviation of the cargo from the vertical. Feedback is fed to the output of the speed controller.

The disadvantage of this device is that it does not take into account the length of the suspension when calculating the angle of deviation of the load. Which leads to an inaccurate determination of the deflection angle of the load.

The technical task of the invention is to reduce the time to calm the oscillations of the suspended load to the mechanism of movement of the trolley and to increase the degree of damping of the oscillations of the cargo compared to the prototype, due to the formation of a more accurate value of the angle of deviation of the load, which contributes to the process of accurate positioning of the load.

The use of the proposed device for automatically damping the pendulum oscillations of a load moved by a bridge crane truck makes it possible to obtain a signal proportional to the angle of deviation of the load from the vertical axis in the plane of movement of the truck. The received signal is fed to the input of a proportional amplifier. The signal from the amplifier output is subtracted from the speed reference signal. The difference is input to the speed controller and is a reference for speed.

A device for automatically damping pendulum oscillations of a load transported by an overhead crane truck is shown in the drawings, where:

figure 1 - presents the design diagram of the forces in the plane of movement of the trolley;

figure 2 - presents a functional diagram for determining the angle of deviation of the cargo in the plane of movement of the trolley;

figure 3 - presents a structural diagram of a control system;

figure 4 is a graph of the speed of the trolley and the angle of deviation of the load in the plane of movement of the trolley, illustrating the operation of the proposed correction device.

The operation of the proposed device consists in introducing into the control system a correction signal proportional to the deviation of the load from the equilibrium position. The correction signal is obtained using the model of the "suspension point - load" system.

A load of mass m _g by means of a suspension of length L _p is connected with a suspension point moving under the action of the force F _dt created by the drive motor of the trolley (Fig. 1). The length of the suspension changes due to the action of the force F _dp created by the lifting engine. The load deviates from the equilibrium position by a certain angle a due to the action of forces due to the weight of the load and the force of resistance to movement F _sv . Under the action of the load weight m _g g, forces F _1x = m _g g · sinα _x and F _2x = m _g g · cosα _x arise. The force F _1x causes the load to move to its equilibrium position, and F _2x determines the suspension tension.

If we assume that the angle of deviation of the load is small and that sinα _x ≈α _x , then the differential equation for the movement of cargo in the plane of movement of the truck (figure 1) is written in the form:

Where - force of resistance to movement; x ₀ - deviation of the load from the equilibrium position; m _g , m _t are the mass of the cargo and the trolley, respectively; L _p - suspension length; K _St , K _t - proportionality coefficients; a _t - acceleration of the truck engine.

The period of oscillation of the cargo is determined by the ratio of the masses of the cargo, trolley and suspension length:

.

The amplitude of the oscillations is a function of the magnitude of the dynamic moment applied from the drive side of the trolley and the period of oscillation:

Cart acceleration:

where T _zi _ _t is the time to reach a given speed (parameter of the intensity adjuster of the control system of the trolley movement mechanism).

Substituting (3) in (2) we get:

From (4) it follows that the deviation amplitude depends on the value of the setpoint of the intensity adjuster and the length of the suspension. The quantity T _ _{T communication} is selected when tuning actuators (large value will significantly reduce the vibrations, but will cause a tightening of transients). Based on equations (1) and (4), we construct a diagram of the device for limiting oscillations.

Functional diagram for determining the angle of deviation in the plane of movement of the trolley is presented in figure 2. Input parameters are: acceleration of the cart the output of the intensity adjuster unit and the suspension length L _n and the load mass m _g, measured with the aid of sensors. Output - the value of the angle of deviation xo in the plane of movement of the trolley.

A device for limiting the swinging of the load in the plane of movement of the trolley contains an intensity adjuster - 1; proportional amplifiers 4, 9 and 18 with amplification factors k _t , K _s and K _cor, respectively; adders - 5, 16, 19; integrators - 6, 7; dividers - 8, 13 and 15; multiplication blocks - 11, 14; blocks forming constant values: 10 (mass of the trolley - passport data), 12 (acceleration of gravity - 9.81 m / s ² ), 17 (number 1).

The obtained value of the angle of deviation of the cargo from the vertical axis in the plane of movement of the trolley is fed to the input of the proportional amplifier 18 with a scaling factor K _cor . The signal from the output of the amplifier is subtracted from the speed reference signal. The difference enters the input of the speed controller and is a task for speed (figure 3). In Fig.3: ZI - intensity regulator, PC - speed controller, RT - current controller, M - electric drive.

At the initial start-up point, the load suspension point is accelerated with constant acceleration, determined by the value of the setpoint intensity adjuster. In this case, the load under the action of inertia forces deviates from the vertical position, as a result of which there is a deviation in the plane of movement of the cart x ₀ . At some point in time, the difference between the output of the intensity adjuster and the correction signal becomes sufficient so that the speed controller leaves the limiting mode, and this happens until the drive reaches the set speed. Therefore, at the end of the transition process, the acceleration of the drive decreases, which leads to a decrease in the dynamic moment on the motor shaft and the load catches up with the suspension point. As a result, after the completion of the transition process (after reaching a predetermined speed), there are no cargo deviations (Fig. 4). In Fig. 4 V _t is the speed of the trolley, α is the angle of deviation of the load in the plane of movement of the trolley.

Claims (1)

A device for automatically damping pendulum oscillations of a load suspended from a traveling mechanism of an overhead crane truck, containing a flexible suspension, an electric drive for the movement of the truck, a load weight sensor, an intensity adjuster for a slave control system with an output signal -

(acceleration of the mechanism), integrator, division block, adder, constant setting unit (m _t is the mass of the trolley), characterized in that, in order to increase the damping efficiency due to the accuracy of determining the deflection angle of the load and the use of the device to damp the resulting vibrations in the plane movement of the trolley, the integrator is covered by negative feedback with a coefficient of K _s connected to the first adder, in addition, a second integrator with a single negative feedback received at the input of the first multiplier is added, to the other input of which a signal is detected, determined by the signal from the weight sensor (proportional to the mass of the cargo m _g ), fed to the input of the divider, divided by a constant - m _{t the} mass of the trolley, the result goes to the adder, where addition occurs with a constant equal to 1, the output of the adder is connected to the input of the multiplier, the signal from the output of the divider is received at the second input of the multiplier, in which the constant equal to 9.81 (acceleration of gravity) is divided by the length of the suspension received from the length sensor, the output of the multiplier goes to the course of the first multiplier, the output of which is fed to the input of the first adder, which also receives the signal from the output of the intensity adjuster -

supplied through a proportional amplifier with a gain of K _t , the output of the second integrator goes to the input of the divider, where it is divided by a constant m _t , at the output of the divider we get a value proportional to the angle of deviation in the plane of movement of the mechanism, fed to the input of a proportional amplifier with a scale factor K _cor , the obtained value is subtracted from the speed reference signal input to the speed controller.