Communications: directive radio wave systems and devices (e.g. – Plural radar
Reexamination Certificate
1999-11-17
2001-05-08
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Plural radar
C342S005000, C342S118000, C342S123000, C342S195000, C342S450000, C342S458000, C342S403000, C324S642000
Reexamination Certificate
active
06229473
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention is directed to the determination of the position of loads suspended from a carrying cable in hoists that are one-dimensionally or multi-dimensionally moved by corresponding actuating drives.
The stopping of a crane or of the load suspended from the crane over a set-down point normally causes an overshooting or swinging of the load. The time delay for the set-down event resulting therefrom leads to a considerable lengthening of the overall transport time of the load. Rocking or, respectively, swinging of the load, however, can be entirely or partially stabilized by movements of the crab or, respectively, of the crane or of the actuating drives executed correspondingly anti-phase. The constant position measurement of the load suspension means is necessary therefor, whereby a defined point, the load suspension point, is expediently considered. In the general case, the lateral position in the x-direction and y-direction of the coordinate system must be identified with a precision of below +/−1 cm proceeding from the crab plane. The measuring time connected therewith should not exceed a few milliseconds. Such measurements are usually implemented in non-contact fashion and leads to a position determination in space. These measurements, however, are disrupted by certain environmental conditions such as temperature, rain, snow, darkness or bright sunlight and the like.
Currently known methods for an average position action of the above type are implemented either by an opto-electronic acquisition of the load suspension point or via a swing angle measurement with mechanical or magnetic measuring means in the proximity of the cable suspension during operation of the crab. Given the latter method, however, cable undulations can considerably falsify the measured result. In the first-cited, opto-electronic method, the acquisition of the load suspension point is negatively influenced by the environmental conditions. Thus, the dependability of these methods is not always assured. Over and above this a two-dimensional position determination within a few milliseconds presents difficulties. Although optical reflectors or infrared light sources have been applied in the meantime for better recognition of the load suspension means for the opto-electronic method, these devices cannot eliminate the disadvantages of said method.
SUMMARY OF THE INVENTION
The invention is based on the object of making an arrangement available for the determination of the position of a load carried by cable of a hoist. The position determination should function constantly and disruption-free and be the basis for a damping of swing.
In an embodiment, microwave range-finding is utilized and various instances of problem-solving are described on the basis of said object.
The invention is based on the perception that significant advantages can be achieved with the utilization of microwave range-finding technology for a position determination of the load in hoists. The particular advantage is thereby comprised in the propagation of the microwaves that is undisturbed by the environmental conditions. Over and above this, a high precision can be achieved in the range-finding, and the measuring times are extremely short. Microwave range-finding is based on measurements of the transit time of the signals that are sent out and in turn received. The frequency range lies between 1 and 100 GHz. A microwave transmitter transmits a spherical wave that is received by a corresponding receiver. When a microwave signal is deflected via what is referred to as a retro-reflector, then this in turn reflects a spherical wave.
Proceeding from a lateral carrying cable suspension, i.e. a carrying cable suspension movable in x-direction and y-direction, a swing will always occur upon arrest when moving a load suspended at the carrying cable. The inventive arrangement provides that microwave measuring units are attached with which the distance measurements between carrying cable suspension and load suspension point can be implemented, whereby the approximate measuring directions describe a finite angle with the carrying cable. These microwave measuring units are arranged, on the one hand, with a known position relative to the carrying cable suspension and, on the other hand, with a known position relative to the load suspension point. For a position measurement of the load suspension point, it is important to optimally design the angle between the carrying cable and the measuring directions corresponding to the microwave measuring units. Dependent on the respective application, the microwave measuring units are arranged at approximately equal intervals around the carrying cable.
According to the invention, the microwave measuring technology is advantageously utilized at hoists, whereby the position determination ensues one-dimensionally, two-dimensionally or three-dimensionally dependent on the respective application or use. Correspondingly, the equipment of the inventive arrangement exhibits a different plurality of microwave measuring units.
The position of the load suspension point can be three-dimensionally determined by employing at least three microwave measuring units. In this system, respectively three ranges are determined on the basis of transit time measurements. The position of the load suspension point is then calculated from the intersection of the three spherical surfaces with the radii that correspond to the distance between transmitter and receiver or, respectively, transmitter/receiver combination and retro-reflector, and the centers that are respectively represented by the positions of the transmitters or, respectively, transmission and reception combinations. Since a damping of the swing of the load suspension point for essentially lateral movements comes into consideration for standard hoists, there is the possibility of obtaining the acquisition of the z-direction, i.e. of the height coordinate, by a measurement of the length of the carrying cable as a substitute for one microwave measuring unit. In this case, two microwave measuring units would be employed in addition to the measurement of the cable length. The height of the load suspension point, however, is more reliably determined by employing three microwave measuring units than it is by measuring the cable length.
When the load suspension point can only move one-dimensionally back and forth, the position measurement of the load suspension point initially requires two microwave measuring units. To this end, it is necessary that the connecting line between the two transmission or, respectively, transmission and reception units lies in the swinging direction of the load suspension point. The connecting line should at least be parallel to the swinging direction. A load suspension point two-dimensionally movable in a vertically residing plane can be measured with this embodiment.
A likewise two-dimensional position measurement for the load suspension point derives when the position of the load suspension point is determined with a microwave measuring unit lying in the plane of motion of the load suspension point and the measurement of the cable length. Since the height value is of no direct significance again for practical swing damping, the determination thereof can be accomplished by measuring the length of the carrying cable. Since the excursion of a carrying cable can be set at a maximum of 6°, the swing damping is implemented quasi-linearly. Knowledge of the height value (z-coordinate), however, can be employed for the exact set-down of the load.
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Doemens Guenter
Wichner Wolfgang
Gregory Bernarr E.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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