Patent GB-1355515-A (GB)
Title: Method of and arrangement for suppressing pendulum  oscillations of a load hanging on a rope and conveyed by a crane  trolley
IPC: B66C13/06
Filed: 1971-05-10
Abstract: 1355515 Inhibiting crane trolley loads swing- ing SIEMENS AG 10 May 1971 [9 May 1970] 14033/71 Heading B8B [Also in Division G3] In a method of inhibiting pendulum oscillations of a load hanging on a rope and adapted to move by means of a crane trolley with a speedcontrolled drive, the travel time for a predetermined distance to be travelled by the crane trolley is adapted, by choice of the speed to which the trolley is to be accelerated from rest with a predetermined acceleration and is to be decelerated to rest with a corresponding deceleration, to be equal to the period of the cycle, relative to a mean rope length, of the pendulum oscillation or a whole-number multiple of this period, and the acceleration is within the first cycle of oscillation of the load, while the deceleration is within the last cycle of oscillation of the load. In general, application of the method results in free swinging of the load during the whole period of travel, the swinging induced by the acceleration being annulled by the deceleration. In the special case of linear acceleration and deceleration respectively throughout the first and last cycles the load does not swing throughout any remaining period of constant velocity. Fig. 1 is a block circuit diagram showing control apparatus for carrying out the method. A crane trolley motor 1 is controlled by a thyristor 2 controlled by a rotational speed controller 3 to which is fed a signal from a travel control arrangement including a travel controller 4 and a ramp generator 5 capable of providing a rising speed signal. A tacho-generator 6 coupled to the motor 1 supplies the actual rotational speed n while a signal source 7 with a sequentially-connected digital-analog converter 8 produces an actual travel distance value S. The desired travel distance value S* is set by the operator on a keyboard 15 whose individual keys are each associated with a predetermined travel distance. The system is automated by feeding the ramp generator 5 with a signal which limits the time of the rising speed signal in dependence on the particular mean rope length l and the particular desired travel distance value S*. This signal is provided by the circuit arrangement, shown in the dotdash line, which comprises an operational amplifier 9, a multiplier 10 and a critical value signalling arrangement 11 which forms from the values I and s* the time t z  corresponding to a whole-number multiple of the time of one oscillation cycle. The operational amplifier 9 operates in accordance with the formula v being the speed of travel and b the acceleration. The above circuit arrangement is suitable for travel distances s* which are to be travelled in a time t z  corresponding to at least one cycle of oscillation. Fig. 2 (not shown) illustrates a modification suitable for times greater than two cycles of oscillation when it is possible to run at a constant speed without pendulum oscillations. In addition allowance may be made for change in the mean rope length during travel altering the period of oscillation and thus the required deceleration time.