Abstract: In order to solve the problem of deviation during large crane carriage operation, this paper selects laser displacement sensor as a correction tool according to the working principle of displacement sensors. Information collection and control schemes are designed for deviation correction. The application results show that the displacement sensor correction controls mechanical equipment meets national standards for building cranes, can timely adjust the speed difference between soft legs and hard legs, making them reach synchronous state.

Introduction

In an era of rapid economic development, shipbuilding has entered a new chapter, and large cranes have gradually developed towards intelligent direction. Traditional manual correction consumes huge human resources, with high operational errors and high risk levels, which is limited in practical applications [1]. The concept of automatic correction breaks through traditional manual correction mode, achieving automation and precision, improving safety factors, and having great research significance. This article will focus on it.

Analysis of Large Crane Carriage Operation Distance Deviations

During large crane carriage operations, there may be deviations in operating distance, mainly manifested in the following six aspects:

(1) There are complex structures in both sides of the carriages, due to different parameters being not synchronized, resulting in control errors, including rotation speeds, braking, starting three parameters, causing significant deviations when data do not synchronize during operation.

(2) During operation, if emergency braking occurs because of special situations or whole machine acceleration, requirements for controlling changes in status of carriages become higher. It takes some time from current status to another one within short period, so it's difficult to complete by existing performance of carriages, thus easy to slip.

(3) Due to differences in resistance generated by two sides of carriages, significant position deviations occur.

(4) Because transmission control system is still imperfect, therefore itself exists certain deviations, unable to control running parameters such as rotation speeds accurately.

(5) Operating track environment affects its work status significantly, including linearities, parallelism, heights etc.

(6) When performing overall operations, center of gravity shifts, leading to position deviations.

The above analysis shows all position deviations caused by carriages. Most units use manual correction methods to correct positions, adjusting carriage positions. These methods exist many problems, need improvement. The proposed displacement sensor provides a new path for correcting ways.

Principle of Displacement Sensor Correction

Correction control systems utilize displacement sensors to collect information about position deviations produced by large crane carriages, obtaining part of data at smart control terminal, using these values as S main position, analyzing position data via encoders and other control devices, regulating size of deviations based on idealized status of carriages, i.e., automatic correction, thereby improving accuracy of large crane carriage operation control. Principle of displacement sensor correction is shown below:

Using displacement sensors to collect position information produced by carriages, recording it as S main position under PLC control, adjusting rotational speeds according to given rotation speeds, realizing position correction. By setting frequency converters to regulate torque, after motor drives, adjusting sizes of current positions based on real-time information of carriages, correcting position deviations. Utilizing encoders, constructing nf function, forming closed-loop control model of correction control system.

Practice Applications of Displacement Sensors in Large Crane Carriage Automatic Correction

This article utilizes displacement sensors to collect position information of large crane carriages, designing practice application scheme according to principles of displacement sensor correction, aiming to improve manual correction control schemes.

Installation Site Selection

Displacement sensor installation is key factor determining whether information collection functions well. Researches on large crane carriage automatic correction system require collecting position information, considering small deviations, installing displacement sensors on soft leg side. After carriages start moving, collected information automatically transmits to control terminals, judging actual operation conditions according to preset control plans, issuing commands accordingly, completing corrections.

Displacement sensor site selection includes installation on soft leg side of large crane carriage. When carriages begin moving, hereafter, position information will automatically transmit to control terminals, judging actual operation conditions according to preset control plans, issuing commands accordingly, completing corrections.

Information Collection Based on Displacement Sensors

Currently, various types of sensors are used to collect position information, including eddy-current type, strain gauge type, Hall effect type, variable reluctance transformer type, capacitive gap type, incremental encoder type, magnetic scale type, analog displacement sensor type etc. Used for measuring displacements in different cases. This study focuses on relatively smaller deviations and requires high precision. Considering multiple sensor performances comprehensively, this article chooses analog displacement sensor as primary device for position information collection, utilizing this device to collect position deviations of large crane carriages.

In practice applications, install this device on both soft leg side and hard leg side of carriages. When carriages begin moving, magnetic field changes, semiconductor thin film magnetization strength changes, accumulating electrons on two directions, generating electric fields, signals transmitted in form of currents. Generating position signal converted into position information, comparing with idealized status of running position, calculating deviation value, this value serves as major basis for command issuance.

To enhance numerical accuracy, this study uses analog displacement sensors to collect position information while testing their performance first, then applying them to both sides of carriages, collecting running data, and finally conducting correction.

Control Scheme

Research plan proposes laser displacement sensor as correction tool, according to aforementioned information collection scheme, collects position change information of carriages on both sides, converting it into electrical signals via potentiometer elements, automatically transforming mechanical movement distances into parameter values, establishing relationship with functions, converting into current values, analyzed via PLC simulation, obtained analytical signals, controlled by A/D module, transformed into digital signals, enabling effective control over running speeds of mechanical devices, reaching purpose of synchronizing movements of each component of carriages, thus deviations corrected. Amongst this scheme, master frequency converter is core module for command issuance, primarily regulates force torques of mechanical devices, regulated by PLC under control, limiting running speeds, adjusting force torque sizes, respectively regulating running speeds of soft leg side and hard leg side, recorded as speed (from) and speed (main). In actual operation, according to actual position information of carriages, respectively regulating speed (from) and speed (main), ensuring synchronization of all parameters of carriages, thus reducing position deviations, meeting requirement of national standard for construction of cranes.

According to national standard for construction of cranes, maximum allowable deviation between soft leg side and hard leg side of large crane carriages should not exceed 0.5‰, exceeding this value needs immediate corrective measures. Therefore, among correction works, need to keep deviation less than 0.5‰ before taking corrective actions, otherwise large crane carriage running could cause serious accidents.

After implementing this scheme in practice applications, compare startup numerical values of displacement sensor automatic correction apparatus with those of manually operated ones, thus evaluating reliability of our research plan. Comparison test results are as follows:

Experiment 1: Startup numerical value of displacement sensor automatic correction apparatus was 0.3‰, whereas that of manually operated apparatus was 0.7‰;

Experiment 2: Startup numerical value of displacement sensor automatic correction apparatus was 0.3‰, whereas that of manually operated apparatus was 0.9‰;

Experiment 3: Startup numerical value of displacement sensor automatic correction apparatus was 0.3‰, whereas that of manually operated apparatus was 0.9‰;

Through comparison of above three sets of experiment results regarding startup numerical values of displacement sensor automatic correction apparatus, we find that displacement sensor automatic correction apparatus begins correction once deviation reaches 0.3‰, effectively correcting position deviations; however, manually operated apparatus starts correction only when deviation exceeds 0.7‰, far beyond limitation set forth by national standard for construction of cranes, when deviation between soft leg side and hard leg side surpasses specified limit, beginning corrective action, leading to low safety coefficient of large crane carriage running. Thus, compared with manually operated apparatus, displacement sensor automatic correction apparatus achieves lower position error, providing greater help to large crane carriage running correction.

Conclusion

This article addresses issue of deviation during large crane carriage operation, analyzes causes of deviation, attributing it to non-synchronization between soft leg side and hard leg side, selecting laser displacement sensor as principal correction tool, designing information collection and correction control schemes. Practice application comparison results indicate that displacement sensor automatic correction control performs better than manual correction, meeting national standard for construction of cranes, able to promptly correct deviations, meet requirement of national standard for construction of cranes.