The Stacker Cranes -- a Good Solution For Parking in Large Urban Areas

March, 2004

In recent years, a parking problem has become an ever more frequent topic of discussion. The steady increase in both number of automobiles in the European cities and the percent of cars used every day has caused a lot of inconvenience for drivers and pedestrians.
The town plan of the Bulgarian capital Sofia, which has recently been discussed, provides for the building of underground and aboveground parking garages close to subway stations. Parking places will be set up near the permanent ways of Trans European Corridors 4,8,10, which go past Sofia. According to this plan, a new system called "park and travel" will also be initiated. Aboveground parking garages in proximity to bus and railway stations and the airport are also provided for.
Special projects for solving the parking problem are included in the specialized program for parking in the downtown area and are pointed out as a matter of urgency. Unfortunately, the municipal and government offices do not provide for the new garages to be many story with automated parking and return of automobiles. The usage of automated garages would resolve the parking problem more effectively.
The shortage of parking places on a world scale can be solved by more effective use of the parking garages available. A very good decision would be to set up paid parking temporarily in the downtown area. This results in shortening the duration of parking and increasing the number of automobiles that can park in this area.
An additional solution would be the building of new garages and the optimum use of the terrain available (free or used as open parking lots). A very good decision would be to build automated parking garages served by stacker cranes (see fig.1), which are the basic element of automated warehouse systems.
An interesting field of application of stacker cranes is for moving loads of large dimensions such as long materials. Our intention is to show the application of stacker cranes as an element of the automated parking garages.
The stacker cranes used in such garages are usually two-column, but four-column also are possible. They can be moved in parallel or perpendicular toward garage cages (it depends on the construction of the latter) on one or two carrying railways, with or without upper leading railways. The most used gears that carry the load are telescopic forks and satellite vehicles.
The main advantages of the automated parking garages served by stacker cranes in comparison with other systems for parking include optimum use of the available space; minimum room for a parking automobile; no need for platforms and staircases; the module principle of building, which shortens the time needed to build a garage; and less time for parking and forwarding because of the high traveling speed of the stacker cranes and simultaneously vertical and horizontal movement.
The four-column stacker crane can also be used in automated garages. Its metal construction consists of two two-column platforms connected with specially shaped metals.
The stacker crane serves a zone equipped with racks of tunnel cages. A satellite vehicle on the loading platform takes and returns the automobiles to and from the parking zone. Automobiles with different dimensions can be parked in one cage. After taking or returning the car, the satellite vehicle goes back to the platform of the stacker crane. There it is conveyed to the entrance/exit of the garage where the automobile is left or a new one is loaded up for transport to the parking zone.
In another solution, the satellite vehicle hoists only the front axle of the automobile. The entering automobile is disposed on a rotating platform equipped with a device that allows precise orientation of the automobile toward the sector of the leading way of the satellite vehicle on the platform. After positioning the automobile, the platform turns and orients the car in the direction of the entrance/exit of the parking zone. The satellite vehicle has its own hoist and horizontal moving mechanism. After leaving the stacker crane, the satellite vehicle moves to the automobile, hoists its front axle and pulls it on the stacker crane platform. The latter transports the car to one of the cages. The satellite vehicle together with the automobile leaves the crane, enters the cage, puts the car there and returns. The time needed to put the car in the cage or to return it to the exit is between 60 and 90 seconds.
Another option is building automated parking garages served by stacker crane equipped with telescopic forks. Usually, only one stacker crane is used. If many parking places are required, additional stacker cranes must be installed. Thus, the admission capacity of the garage increases.
This kind of automated parking garage is not widespread. A high-racked automated garage is built in Spain where stacker cranes on rails are used. Systems of automated parking exist in the Balkan countries too -- for example, in Athens and Istanbul.
The automated garage in Istanbul was opened in May 2002, and its capacity is 612 automobiles. There are six automated parking devices (each serves 102 parking places) and 12 entrances/exits. Twenty percent of the parking places are used as official subscription for long-duration parking; the others are for short-duration parking.
The automated parking lot garage in Athens has a capacity of 231 automobiles. It is a combined type of 10 aboveground levels and one underground level. It has two street-level entrances/exits, two elevators and two satellite vehicles that run on special guide rails. Entrances/exits are equipped with turn-mechanisms and admit automobiles to and from the elevators on which the two platforms are located.
Automated parking garages far exceed all other systems for parking in regards to utilization of area or terrain available and costs.
For that reason, their application is a good choice in cities where the need for parking places steadily increases.

Krasimir Krastanov and Delian Tonev are Master Engineers and Ph.D. students. They are working on their dissertations with Professor Vikenti Spassov, Ph.D., at the Higher School of Transport, Department of Material Handling and Logistics, in Sofia, Bulgaria. Spassov can be reached at vspassov@vtu.bg; Krastanov krasi_krastanov@yahoo.com; and Tonev at tonevdh@yahoo.fr.