Long Span Gantry Crane

Electric Automatic Rectification System of Long Span Gantry Crane

First, the issue raised

Large span greater than 40 meters of the gantry cranes in actual use, due to many factors, such as the height of the rail track and parallel deviation caused by different running resistance, wheel diameter deviation, the motor speed deviation, Time will have a different phenomenon, usually when the deviation near the span of 3/1000, the crane should automatically slow down the correction, the driver can also manually correct deviation deviation indicator; when the deviation exceeds the span of 3/1000, The skew limiter automatically disconnects the running control circuit of the cart, so that the crane automatically stops.

Second, the commonly used electrical automatic correction method

Large-span door to automatic correction, first of all to analyze the causes and phenomena of deviation, and then take the corresponding corrective measures. Usually have the following kinds of electrical automatic correction method:

1, when the leg and the soft leg on both sides of the motor speed is not the same, such as rigid side of the motor side of the average motor speed faster than the soft side of the motor 1/1000, which can be calculated by the pulse encoder PLC pulse number To correct;

2, the main beam and the angle between the soft legs greater than or less than 90 degrees, which can be installed at the top of the soft legs of the angular displacement sensor method to correct;

3, by comparing the rigid leg side carts and soft legs side of the actual running wheel speed of the wheel, which can be used to drive the rubber friction wheel closed-loop control method to correct the deviation;

4, directly in the side of the leg and the soft side of the soft side of the train running next to the rail parallel to install a number of sensing points, the use of proximity switches to measure the side of the leg and the soft side of the action close to the switch and input PLC input method to correct ;

Third, the cart electrical control and automatic correction system

This program uses just, soft leg side of the motor were driven simultaneously with two inverters, using the above method 4 for automatic correction of control. Specific carts electrical control system design guidelines are as follows :,

1, the speed ratio of the cart mechanism is 1:10 or so; one to 5 speed set to 10%, 30%, 50%, 75%, 100% of the fastest speed (the specific speed range see mechanical General Chart);

2, the control mode for the left box linkage master master control; left horizontal body control cart about 5 speed;

3, the cart motor should be added pulse encoder 2, just, soft legs on each side 1;

4, will just, soft leg side of the cart motor PGA, PGB pulse signal feedback to the inverter for closed-loop control;

5, will be just, soft legs next to the actual record of the rail speed pulse +01-S0A / S0B, +02-S0A / S0B pulse signal sent to the PLC input X17, X20;

6, the electrical system uses a variety of protection functions, with motor overload protection, inverter overload protection, power grid over-voltage protection, phase protection, motor speed, stall protection, brake unit overheating protection, door limit switches, Car limit, and so on

Fourth, the electrical automatic correction principle

1, the basic program preparation and parameter setting method is calculated by the speed pulse (rigid) leg side of the side of the actual running distance – using high-performance proximity switch records on the rail anchor plate on the anchor nut on the nut (Of course, accurate calculation can be just in the crane just, soft legs next to the rails equidistant to place some electromagnetic induction point);

2, set the first pulse of the proximity switch side of the actual running speed, the pulse signal immediately into the PLC input X17 (or X20), immediately record speed and automatic correction control.

3, automatic correction method is fast on the way to slow down – such as cranes in the running process, the soft side of the legs faster, soft side of the first switch to the proximity switch to sense the induction nut on the bolt, soft legs close to the control side of the switch Open into the normally closed, the relay K510 pull, PLC input X20 generated input signal can be programmed: LD X20, ANI X17, OUT Y17, then the soft leg of the inverter control input S9B deceleration control signal, The soft side of the four motors immediately deceleration operation, when the rigid side of the proximity switch is also detected bolt nut, it automatically disconnect the S9B input signal, so that soft, rigid side of the motor and at the same time Of the speed of stable operation;

4, such as the crane in the course of running, just the side of the leg faster, rigid side of the proximity switch first sensor to the nut on the bolt, rigid legs close to the control side of the switch from normally open to normally closed, the relay K509 pull, PLC input Side X17 produces the input signal, the program can be programmed: LD X17, ANI X20, OUT Y16, then the control unit S9 of the rigid-legged inverter inputs the deceleration control signal, the four motors on the rigid leg side immediately decelerate, The soft leg side of the proximity switch is also detected on the bolt nut, it automatically disconnect the S9 input signal, so that just, soft leg side of the motor and the same speed and stable operation;

fifth, concluding remarks

Large-span gantry crane electrical automatic correction methods are also many, such as the use of global positioning system GPS, etc., but the installation and maintenance costs are relatively high. The advantages of this program is simple circuit, the deviation of the sampling part with the sensor nut 5-20mm away from the normal work can be close to the electromagnetic switch, the switch protection level is greater than IP67, no rotation, friction parts, long life, installation and commissioning Maintenance is very convenient.