Schematic diagram of speed switching circuit hydraulic system

The following takes the speed switching circuit as an example to illustrate the writing of PI.C control program in the hydraulic system experiment. The principle diagram of the hidden pressure of the speed-changing Jianpu Road
is shown in the figure.
    The action cycle is as follows:
    1) When energized, 1ZT has power and the hydraulic cylinder realizes fast forwarding.
    2) When the travel switch 2XK is pressed, 3ZT is powered, and the oil returns to the speed control valve l to achieve one-work progress.
    3) When the travel switch 3XK is pressed, 4ZT is powered and the oil returns to the speed control valve 2 to realize the second work.
    4) When the travel switch 4XK is pressed. 1ZT is powered off, 2ZT is powered on, and the oil circuit is reversed to achieve fast rewind.
    5) When the travel switch Ixl< is pressed, 5ZT has power and the system realizes unloading.
    (2) The I/O allocation of the PLC is based on the hydraulic schematic diagram of the experimental circuit and the control requirements for the action process. The 1/0 points of the PLC are allocated and defined.