US3850308A - Apparatus for accommodating the pendulum action of a load carried by a rope from a traveller - Google Patents

Abstract

A method for suppressing the pendular movement of a load carried by a rope and movable with a traveller equipped with a speed regulated drive has the steps of: adapting the period of pendulum movement for an average rope length or a whole multiple of this period to the distance to be covered by the traveller by selecting the rated speed of the latter; accelerating the drive of the traveller at maximum rate up to said speed in the first quarter period of the pendulum movement; and then decelerating the traveller in the last quarter of the period or of a subsequent period at a rate corresponding to the maximum acceleration until the traveller is brought to standstill. An apparatus for performing the foregoing method has a control system for the drive. The system has a speed regulator with a circuit for selecting the rated speed of the drive to adapt the period of pendulum movement for an average rope length or a whole multiple of this period to the distance to be covered by the traveller. The system further has an acceleration controller for accelerating the drive of the traveller at maximum rate up to the rated speed in the first quarter of the period of the pendulum movement and then decelerating the traveller in the last quarter of said period at a rate corresponding to the maximum acceleration.

Description

United tates Patent 11 1 Meyer et al.

[ Nov. 26, 1974 APPARATUS FOR ACCOMMQDATING THE [57] ABSTRACT PENDULUM ACTION OF A LOAD CARRIED A method for suppressing the pendular movement of a BY A ROPE FROM A TRAVELLER load carried by a rope and movable with a traveller [75] Inventors; Siegfried Meyer, Erla R lf equipped with a speed regulated drive has the steps of: Klingi, Reutl s, b th f Germany adapting the period of pendulum movement for an average rope length or a whole multiple of this period to [73] Asslgnee g fi lgleggesenschafi Berhn the distance to be covered by the traveller by selecting an umc ermany the rated speed of the latter; accelerating the drive of [22] Filed: Mar. 1, 1973 the traveller at maximum rate up to said speed in the first quarter period of the pendulum movement; and [2]] Appl' 336351 then decelerating the traveller in the last quarter of Related U.S. Application Data the period or of a subsequent period at a rate corre- [63] continuation of Sen 140 445 May 5 1971 sponding to the maximum acceleration until the travabandoned, eller is brought to standstill.

An apparatus for performing the foregoing method [30] Foreign Application Priority Data has a control system for the drive. The system has a May 9, 1970 Germany 2022745 p d r gulator with a cir uit for selecting the rated speed of the drive to adapt the period of pendulum [52] US. Cl. 212/132 m v m nt for an average rope length or a whole [51] Int. Cl. new 19/00 multiple of this period to th ist n to be er d [58] Field of Search 212/97, 98, 119, 122, 86, y the a l r- The system further has an 212/1, 39 R, 130, 131 acceleration controller for accelerating the drive of the traveller at maximum rate up to the rated speed in [56] References ited the first quarter of the period of the pendulum UNITED STATES PATENTS movement and then decelerating the traveller in the last quarter of said period at a rate corresponding to 2,806,610 9/1957 Goertz 212/131 3,351,213 11/1967 Newman et al 212/39 R the maxlmum acceleranoni 3,517,830 6/1970 Virkkala 4. 212/132 Primary Examiner-Robert B. Reeves 6 Claims, 3 Drawing Figures Assistant Examiner-Hadd Lane Attorney, Agent, or Firm-Herbert L. Lerner DATUM 11EYB0A1111-- anti-UP CONTROL H D A I i D S J r TRAVEL SPEED PUWER 6 REGULATOR REGULATOR AMPLIFIER J]- D-A CONVERTER As 2 :2 7J o 1- 1 uan VALUE l 1 TRANSMITTER APPARATUS FOR ACCQIVWODATING THE PENDULUM ACTION OF A LOAD CARRIED BY A ROPE FROM A TRAVELLER This is a continuation of application Ser. No. 140,445, filed May 5, 1971, now abandoned.

Our invention relates to a method and apparatus for suppressing the pendulum action of a load carried by a cable from an overhead traveller (crab or jenny) having a speed regulated drive.

Illustrated in FIG. 3, is a load handling machine with such a traveller T on which is suspended the load L from a rope R; the pendulum action of the load is caused by the acceleration and deceleration of the traveller T. An experienced crane operator can control the pendulum action of the load by means of skilled maneuvers. However, with high speeds, the concentration capability of the crane operator reduces considerably so that the apparatus or equipment cannot be used to the fullest extent of its operational capability.

It is known for hoists to dampen pendulus movement of a load carried by a rope by measuring the magnitude and direction of the pendulum angle by means of detecting members and to supply correction values proportional to the magnitude and direction of the pendulum action to a speed regulator of the lifting drive. In this connection, reference may be had to Austrian Pat, No. 232,667.

Another apparatus for dampening a load suspended from a traveller is known wherein the traveller is accelerated to its final speed in two stages or correspondingly decelerated to standstill. For this arrangement, the traveller is accelerated in the first stage to half the value of the final speed and in the second step is brought to the final speed by renewed acceleration as soon as the load reaches the same pendulum angle and the same, although oppositely directed, angular velocity as was present at the end of the first stage. A similar sequence occurs during deceleration.

For a definite travel length in dependence upon the pendulum length or a multiple of this travel, the traveller can be accelerated with maximum acceleration to the rated speed so that the load remains behind by a pendulum angle a at the end of the acceleration; then the traveller is driven at rated speed until the load reaches the same, although oppositely directed, pendulum angle of the same magnitude with the same speed as at the end of the acceleration period. And, at this instant, is brought to standstill with maximum deceleration corresponding to the acceleration. In both cases the pendulum angle and the angular velocity must be observed or detected by measuring. The acceleration and/or the deceleration of the traveller in two steps has in addition the disadvantage, that by todays high speeds, the operational capability of the traveller drive is not fully utilized.

The second method has the disadvantage that the load cannot be brought to standstill at a predetermined location, since one must first wait until the pendulum angle for bringing the traveller to a stop or standstill has the same magnitude as at the end of the acceleration length. In this connection reference may be had to German printed Pat. application No. 1,172,413.

According to a further known configuration, the swing angle is determined indirectly from measured values from a movement equation for a given system by means of a calculating circuit in order to avoid using an apparatus for measuring the swing angle of the load carrying rope. In this connection reference may be had to German printed Pat. application No. 1,287,079.

It is an object of our invention to provide a method and apparatus for bringing a load carried on a long rope from a traveller to any desired location with maximum handling power without having to reckon with the pendulum angle and the angular velocity. Subsidiary to this object it is an object of our invention to bring the rope suspended load to such a location free of pendulum action.

According to a feature of the invention the period of the pendulum swing referred to an average rope length,

or a whole multiple of this period, is adapted to the travel length to be covered by the traveller by means of the selection of the speed of the traveller, so that the traveller propulsion drive in the first quarter of the first period is accelerated with maximum acceleration to the selected speed. In the last quarter of the first or of a subsequent period, the traveller drive is braked to standstill with a deceleration corresponding to the maximum acceleration.

To render the carrying out of this operation or process automatic with a traveller whose drive includes a speed regulator device having superimposed thereon a travel control device with a start-up control, there is provided an electronic circuit to whose inputs are supplied the instantaneous travel datum value signal and a signal value proportional to the rope length and whose output provides a signal corresponding to a value proportional to the number of periods which result from the input magnitudes in combination with the adjusted maximum acceleration and the rated speed and which limits the start-up control such that the null point for the speed of the traveller coincides with the null point of a whole period of the pendulum swing at the target locality or the location to which it is desired to bring the traveller with its load.

Preferably, the electronic circuit comprises an operational amplifier in whose feedback channel there is included a multiplier and a limit value transmitter. The operational amplifier calculates the value supplied to the start-up control according to the formula:

wherein the limit value transmitter computes the time (t,) corresponding to a whole period value from the travel datum value and the rope length.

According to a further feature of the invention, the drive of the traveller is linearly accelerated up to a speed adapted to the distance to be covered by the traveller and which speed is maintained if required during a half period of the dynamic pendulum swing, the half period being referred to an average rope length and corresponding to twice the period of the statistical pendulum movement. The drive is then linearly decelerated to standstill during another dynamic period referred to the average value of the then applicable paidout rope length.

The foregoing process can be carried out automatically for a traveller whose drive is arranged with respect to a control system which includes a speed regulator for the drive. A travel regulator having a start-up control is superimposed upon the speed regulator. Also included is an electronic circuit which has a divider component having respective inputs for receiving the travel datum voltage signal and for receiving a voltage signal proportional to the paid-out rope length. The travel regulator has a feedback channel and a multiplier is connected into the channel. The divider component has an output connected to the multiplier and to the start-up control. An operational amplifier is provided that has an input for receiving the voltage signal proportional to the paid-out rope length and an output connected to the start-up control for displacing the start-up time of the latter. The magnitude of the output of the divider component and the magnitude of the output of the operational amplifier are each proportional to the value 217 V l/g.

The invention will now be described with reference to the drawings wherein:

FIG. 1 is a schematic block diagram of an apparatus according to the invention for carrying out the process of the invention;

FIG. 2 illustrates an especially advantageous embodiment for dampening pendulum swing; and

FIG. 3 illustrates a traveller moving along a track and carrying a load at the end of a cable.

FIG. 1 shows the drive motor I of a traveller. Connected to thedrive motor 1 is a power amplifier 2 for example a thyristor apparatus. The power amplifier 2 is controlled by a speed regulator 3 to which is superimposed a travel regulator 4 with start-up control 5. On the drive motor 1 there is couplied for example a tachometer 6 for delivering the actual value of the speed n of the drive. Also coupled with the drive motor 1 is an impulse generator 7 connected to a digital-analog converter 8 for generating the actual travel value s. The lever I-I serves to preset the speed datum value n*. During automatic operation, the speed regulator 3 receives the output signal of the start-up control as the speed datum value n With this arrangement, for continuous operation for example as required for unloading ships, the crane operator supplies to the travel regulator 4, as datum value, the travel s* to be covered by the traveller. For presetting the travel datum s*, a control lever or a datum keyboard for example can be provided whose individual keys are provided for respective predetermined travel paths. The start-up control 5 is preferably so dimensioned that the speed regulator 3 bring the drive motor 1 with maximum acceleration to the rated speed.

With the movement of the traveller, the load suspended by a rope is placed into pendulum swing whose period T equals 2 1r l/g (statistical pendulum swing). Since the length l of the rope is under the root, it is sufficient to calculate the swing period by substituting for I an average value. So that the initial step defined by the travel regulator can achieve the optimal damping of the pendulum swing at the end location to which the traveller is to move, the following conditions must be fulfilled: first, the time for the path to be covered by the traveller must coincide with the time of a period of the pendulum swing of a whole multiple thereof: second, the force dampening the swinging action must correspond to the force initiating the swinging action; third, the acceleration of the traveller must end in the first quarter of the first period (starting time corresponding to 90 electrical degrees or less); and fourth, the deceleration to standstill must be ended in the last quarter of the first period or of a subsequent period (deceleration occurs between 0 and 90 electrical degrees).

If during the remaining time, the traveller moves for one or more periods with constant speed, the load swings free and is damped however, at the end of the path, to null. For utilizing the full power available, the drive is preferably driven with maximum acceleration. The average rope length required for adapting the travel to be covered by the traveller to the period and the actual travel datum value are known. As a consequence, the crane operator must only be given the speed to be reached in dependence upon the travel path to be covered.

For automating the process and according to FIG. I, a signal is applied to the start-up control 5 which limits the starting time of the start-up control 5 in dependence upon the actual rope length and the difference between the datum value and the actual value of the travel. An electronic circuit is provided to generate this signal and has an operational amplifier 9, a multiplier 10 and a limit value transmitter 11. The multiplier 10 and the limit transmitter 11 are connected into the feedback channel of the operational amplifier 9. The operational amplifier 9 and the limit value stage 11 are supplied with the difference between the datum value and the actual value of the travel voltage signal s* and, in addition, the limit value stage is provided also with the voltage signal b corresponding to the paid-out rope length. The limit value transmitter 11 forms, with respect to the adjusted acceleration, the time t corresponding to an integral period value from the difference between the datum value and the actual value of the travel and the rope length signal l.

The multiplier 10 provides a signal which is proportional to the speed v of the traveller and is compared at the input of the operational amplifier with the travel datum value; this signal has the magnitude v'(vb-t The operational amplifier functions in accordance with the formula:

mental circuitry corresponds to that illustrated in FIG.

1 with the exception that here the electronic circuit functions together with the travel regulator and the start-up control 5. Of the basic or fundamental ci rcuitry only the travel regulator 4 and the start-up control 5 are illustrated. I-Iere also it is assumed that with various rope lengths different lengths of travel should be covered. Travel datum value and rope lengths are available as in the embodiment according to FIG. 1.

The systems illustrated in FIGS. 1 and 2 are assembled from commercially available components such as from among the SIMATIC components described in the publication: Siemens Zeitschrift, October 1959, Vol. 10. pages 593 to 629.

As explained in combination with FIG. 1, the pendulum angle and the angular velocity are at null when the force developed for damping pendulum action in the last quarter of a period is of the same magnitude as the force initiating the pendulum action in the first quarter of the period. If the acceleration of the traveller drive end of the period is likewise at null. If from this point in time, a traveller is moved further at constant speed, the pendulum remains at its rest position except for the action of air resistance. c

The swinging action newly initiated through the braking process of the traveller is compensated in that the braking deceleration is likewise made effective over the duration of a period of statistical swing. Then the pendulum again reaches the end location in the rest position. If the travel 8,, to be covered by the traveller corresponds to exactly two periods of statistical swing, there arises a dynamic swinging in whose first hal-f period the traveller is accelerated and in whose second half period the traveller is decelerated. The value 8,, arises from the product of the minimum cycle time t, mm and the maximum velocity v corresponds to the formula:

D e max. X z min.

wherein t, =21r If the travel to be covered by the traveller is shorter than the duration of a period of dynamic swing with maximum acceleration and maximum deceleration, then the traveler must be accelerated to a velocity v lying below the rated velocity and must be brought to standstill with a corresponding lower deceleration. This velocity v is computed from the travel s to be covered and the minimum cycle time t, mm from: v 2 s/t mm According to the block diagram illustrated in FIG. 2

an electronic circuit is arranged with respect to the travel regulator 4 and the start-up control 5. The electronic circuit includes a multiplier '12 connected into the return channel of the travel regulator 4. The electronic circuit also has a divider component 13 and an operational amplifier 14. The difference between the datum value and the actual value of the travel and a signel having a magnitude proportional to the rope length are supplied to the divider component 13. And to the operational amplifier 14, only the signal b corresponding to the rope length is supplied. The output of the divider component 13 is connected with an input of the multiplier 12 and with an input of the start-up control 5. The output signal of the operational amplifier 14 supplied to the start-up control 5 shifts the start-up time of the start-up control 5. The output signal of the divider component and the output signal of the operational amplifier 14 are proportional to the value given by: 211- Vvgwherein 1 is the length of the paid-out rope.

To those skilled in the art it will be obvious from a study of the disclosure that our invention permits of various modifications that may be given embodiments other than particularly described and illustrated herein, without departing from the essential features of the invention and within the scope of the claims annexed hereto.

We claim:

1. Apparatus for accommodating the pendular movements of a load suspended by a rope on the traveller of a crane having a drive for said traveller including a speed regulating device, comprising an automatic regulating means for accelerating the traveller during the first portion of its travelled distance and for decelerating the traveller during the last portion of the distance so that the traveller and the load come to a standstill almost at the same time, said apparatus comprising, start-up means for said drive connected in series with said speed regulating device; a datum means to receive operator supplied distance of traveller movement and the pendular length of the load; an electronic calculator interconnecting said datum means and said drive means to calculate a traveller speed so that said distance is traversed in one or more whole periods of pen dular movement, said calculator supplying a signal to said speed regulating device so that-there is an interval of acceleration for the traveller, an interval of whole periods of pendular movements during which said traveller travels at said calculated speed and a final interval of deceleration when the traveller and the pendular movement come to a substantial stop at said distance.

2. Apparatus as claimed in claim 1, wherein the electronic calculator forms an output signal controlled by said datum means and the output signal of the electronic calculator so limits the start-up means that the zero point of the speed of the traveller coincides at said distance with the zero passage at the end of a period of the pendular movement.

3. Apparatus as claimed in claim 2, wherein the electronic calculator comprises an operational amplifier having a feedback channel, a multiplier and a limit value transmitter connected into the feedback channel, the operational amplifier having a transfer function for providing a voltage signal from the output to the startup control, the transfer function corresponding to the wherein v is the speed of the traveller, b is the acceleration and s is the travel distance, the limit value transmitter having respective inputs for receiving the travel datum voltage signal and the voltage signal proportional to the paid-out rope length for determining the time t corresponding to the integral period of the pendulum movement.

4. Apparatus as claimed in claim 1, wherein the electronic calculator so determines the traveller speed that the distance travelled by the traveller corresponds to at least two periods of the pendular movement and the drive of the traveller during the first period, which relates to the predetermined length of the rope, is linearly accelerated, and during the second period, which relates to the then predetermined rope length, is linearly decelerated to standstill whereas the speed reached at the end of the first period is kept constant during an additional arbitrary travel distance.

5. Apparatus as claimed in claim 4, wherein the electronic calculator means comprises a travel regulating device superimposed upon the speed regulating device and having start-up control means, a divider component having respective inputs for receiving the travel datum voltage signal and for receiving a voltage signal proportional to the paid-out rope length, said travel regulating device having a feedback channel, a multiplier connected into the channel, the divider component having an output connected to the multiplier and to the start-up control means, and an operational amplifier having an input for receiving the voltage signal proportional to the paid-out rope length, the amplifier having output connected to the start-up control means for shifting the start-up time thereof.

6. Apparatus as claimed in claim 5, wherein the output of the divider component and the output of the operational amplifier are each proportional to the value given by wherein l is the paid-out rope length.

Claims (6)

1. Apparatus for accommodating the pendular movements of a load suspended by a rope on the traveller of a crane having a drive for said traveller including a speed regulating device, comprising an automatic regulating means for accelerating the traveller during the first portion of its travelled distance and for decelerating the traveller during the last portion of the distance so that the traveller and the load come to a standstill almost at the same time, said apparatus comprising, start-up means for said drive connected in series with said speed regulating device; a datum means to receive operator supplied distance of traveller movement and the pendular length of the load; an electronic calculator interconnecting said datum means and said drive means to calculate a traveller speed so that said distance is traversed in one or more whole periods of pendular movement, said calculator supplying a signal to said speed regulating device so that there is an interval of acceleration for the traveller, an interval of whole periods of pendular movements during which said traveller travels at said calculated speed and a final interval of deceleration when the traveller and the pendular movement come to a sUbstantial stop at said distance.

2. Apparatus as claimed in claim 1, wherein the electronic calculator forms an output signal controlled by said datum means and the output signal of the electronic calculator so limits the start-up means that the zero point of the speed of the traveller coincides at said distance with the zero passage at the end of a period of the pendular movement.

3. Apparatus as claimed in claim 2, wherein the electronic calculator comprises an operational amplifier having a feedback channel, a multiplier and a limit value transmitter connected into the feedback channel, the operational amplifier having a transfer function for providing a voltage signal from the output to the start-up control, the transfer function corresponding to the equation: v2 - bmax. X tz X v + bmax. X s 0 wherein v is the speed of the traveller, b is the acceleration and s is the travel distance, the limit value transmitter having respective inputs for receiving the travel datum voltage signal and the voltage signal proportional to the paid-out rope length for determining the time tz corresponding to the integral period of the pendulum movement.

4. Apparatus as claimed in claim 1, wherein the electronic calculator so determines the traveller speed that the distance travelled by the traveller corresponds to at least two periods of the pendular movement and the drive of the traveller during the first period, which relates to the predetermined length of the rope, is linearly accelerated, and during the second period, which relates to the then predetermined rope length, is linearly decelerated to standstill whereas the speed reached at the end of the first period is kept constant during an additional arbitrary travel distance.

5. Apparatus as claimed in claim 4, wherein the electronic calculator means comprises a travel regulating device superimposed upon the speed regulating device and having start-up control means, a divider component having respective inputs for receiving the travel datum voltage signal and for receiving a voltage signal proportional to the paid-out rope length, said travel regulating device having a feedback channel, a multiplier connected into the channel, the divider component having an output connected to the multiplier and to the start-up control means, and an operational amplifier having an input for receiving the voltage signal proportional to the paid-out rope length, the amplifier having output connected to the start-up control means for shifting the start-up time thereof.

6. Apparatus as claimed in claim 5, wherein the output of the divider component and the output of the operational amplifier are each proportional to the value given by 2 pi Square Root l/g wherein l is the paid-out rope length.

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