These device's functions have close relationships with the entire system's control requirements. On the above of the graph, the protection equipment are emergency switch, installed beside the touching panel, emergency only, trigger it, the system stops; Front and back photoelectrical sensors, which are used to detect people or unidentified objects breaking into the system, if this happens, the system would stop then response with photoelectrical failure, the goal is to protect the people and the vehicles. The phase sequence protection has been illustrated before; Over current protection normally activated under the motor stuck; All the margin switches series connected, cult the main power when any carrying board exceed the limiting position. Limit switches including up ones and down ones or left and right limit switches. In order to achieve the controlling requirements, the level limit switches are installed on the both side of the each slot frame, while the vertical limit switches are installed on the chain which attached to the motor. It is necessary to point out that the first layer only installed down and left right limit switches, the top layer only installed up switches these switches could sense the position of the carrying boards, helping to finish the lifting and traversing control; Hook position sensors is to fix the vehicles and sense the slot empty or not. The output points"00 04 05 06 07" are to select different phase for each layer, so control the motors' rotation ways. A. TAKING PROCEDURE As far as the first layer concerned, it is only designed to traverse, so as to make space to upper layer's carrying boards to move downward. So do the other layers, which are designed to traverse. When traversing meet the requirements, lifting mechanism will run to put the carrying board down, finishing the saving and taking procedure. During the procedure the photoelectrical sensors are open and will behave as fore part has explained. In figure 2A, is the taking condition, at this time "Loading" will flash until the taking procedure finishes. When we enter "51", the system will distinguish whether the operation is a taking or a saving according to the hook of the 51 slot. Then prints the message responded to the state of the hook on the screen, the operator could confirm the operation or cancel it. On confirming, the 51 carrying board will wait for its downward boards to finish the traversing move then moving down. In addition, a timer is added to this control module in order to preclude level limit switches malfunction, resulting into the traversing move time up. If the time for traversing move exceeds the set time, the system will warn the operator "traversing move time up" which displays on the screen, the operator could check out the failure. The up limit switches are used to sense whether the carrying boards are stopped at their routine slots, which the level switches can't finish. Maybe one carrying board stuck between two layers. Only do all the upper layers' carrying boards stop at their routine slots, the selected carrying board's lifting move is activated. A timer is also set into the lifting control, with the same function as traversing timer. The elevator carries the vehicle down to the ground, release the hook, now the photoelectrical signal shut down, and waiting for the owners to take their vehicle. On driving away the vehicle and operator's confirming, the photoelectrical signal resumes, the carrying board back to its slot from the down way. IV. SOFTWARE PROGRAMMING AND PROGRAMMING ENVIRONMENT A. SOFTWARE PROGRAMMING ENVIRONMENT AND ITS LANGUAGE In this system, we choose Omron CX-ONE 3.0 to program the PLC. The language for programming is classic ladder diagram. On considering the stereo garages are installed in different condition and requirement of different users, the scale of the stereo garages should be flexible, for example different layers or slots. In order to meet the different scales requirements, the program is modularized, only need to change the I/O ports, the logical relations in the ladder diagram are fixed. In this way, it is not only with highly compatibility but also shortens the period to develop relevant designs and make it easier to debugging and repair. B. MODULARIZED PROGRAM Conditional jumps are widely used in the programming; the entire program consists of different modules, on certain conditions, the program jumps. As illustrated before, there are only two movements for a carrying board, lifting or traversing, beside the boards of first and top layers. The condition for the fifth could traverse is all the upper layers slots' up limiting switches closed. PLC6层立体车库设计英文文献和中文翻译(2):http://www.751com.cn/fanyi/lunwen_34846.html