2 years ago



Compartment fine

Compartment fine positioning with camera-based positioning sensors LOGISTICS In the past 20 years, the design of pallet and container racks has changed considerably. The loading possibilities and range of applications became significantly larger. Racks are increasingly affected by thermal and dynamic influences and shock loads have increased. The resulting deformation of rack components under load, for example, from deflection or expansion, must therefore be considered in detail. The 200 class includes racks in which the high-bay storage devices are automatically controlled and which have a fine positioning system at the storage spaces of the loading units. For the fine positioning, influences that act on the tolerances of the steel structure in the warehouse are to be given special consideration. In addition to mechanical tolerances from material- and mounting-related variances, these also include wall and wind loads, elastic deformations as a function of the load state, static and dynamic loads of the highbay storage device from different load states (empty runs, removal from storage with load), forces from acceleration and deceleration as well as thermal deformations and material expansion. If one initially considers only the deformation from different load states, it quickly becomes clear that the horizontal position can change as a result of the deflection of the bar. Just as the horizontal position can change, so too can the vertical position, as the columns can likewise deform as a result of dynamic, thermal or shock loads. It thereby becomes apparent that adherence to the functional requirements for the precise positioning of a highbay storage device takes on special significance. For positioning in the X- and Y-direction, rough and fine positioning are generally used. Used for the rough positioning of the high-bay storage device are, for example, bar code positioning systems, optical distance sensors or incremental transmitters. Once the approximate position is reached, compartment fine positioning performs the targeted approach of the high-bay storage device to its final position. Mounted on the load receptacle of the high-bay storage device are at least two optical diffuse reflection sensors per positioning direction – for the X- and Y-direction – i.e., at least four sensors. Without object detection, the outputs of the sensors are OFF. If a sensor detects the edge of a column or of a bar, the output state changes and the sensor output indicates ON. With the help of the new signal state, it is possible, on the one hand, to detect the direction of movement of the high-bay storage device and, on the other, to calculate the desired target position with respect to the edge. Shown in the following is the schematic arrangement of the sensors with the corresponding binary evaluation. The arrows indicate the intended direction of movement of the high-bay storage device. Other states arise in a similar manner. The solution with binary sensors, which has proven itself over the years, has a number of disadvantages. For example, the space available on the load receptacle is extremely limited, since additional sensors are often mounted there. In addition, diffuse reflection sensors can relatively easily produce faulty switching as a re- 22 WORLD OF INDUSTRIES 8/2018

01 Unloaded pallet warehouse 02 Loaded pallet warehouse results in a deviation of the horizontal position due to the deflection of the cross member sult of glossy profile surfaces, undesired reflection signals from edges located in the background or due to the effects of ambient light. The biggest disadvantage, however, is the complex alignment of the binary sensors. Trained, qualified personnel are required for this purpose. In addition to this is the fact that a binary sensor provides no further state information, such as information concerning the function reserve or sensor state. Similarly, new possibilities and solution approaches that arise from digitalization within the scope of Industry 4.0 for diagnosis and predictive maintenance cannot be supported. What alternatives are available for a forward-looking compartment fine positioning solution? A camera-based positioning system with an evaluation algorithm tailored to the specific application offers one possible solution ap- Time-less E4.1L: Moving energy made even easier ... Fast harnessing and time-less design. Reduce assembly and harnessing time by 80 %* The E4.1L e-chainsystem ® can be harnessed faster than any other. New separators and strain relief elements enable lightning-fast assembly and strain relief of complex, multi-level cable fillings. plastics for longer life ® *measured in the igus ® harnessing factory Tel. +49 2203 9649-800 The terms "igus, e-chainsystem, plastics for longer life" are legally protected trademarks in the Federal Republic of Germany and, where applicable, in some foreign countries. Igus.indd 1 28.09.2018 09:51:07 WORLD OF INDUSTRIES 8/2018 23