I. Application Background

In a modern large-scale logistics and warehousing center, efficient and accurate cargo storage and handling are of utmost importance. The warehousing center has adopted an automated stereoscopic warehouse system, which uses vertical lifting equipment to quickly transport goods to the designated shelf levels. These vertical lifting devices need to frequently and accurately start, stop, and position within a space as high as 20 meters, posing stringent requirements on the accuracy, stability, and reliability of the displacement measurement technology. Previously, the warehousing center used a traditional wire rope type displacement measurement device. Its principle was to determine the position of the lifting platform by measuring the retraction and extension length of the wire rope. However, in actual operation, this method had numerous problems. The wire rope was easily affected by gravity, wear, and tensile deformation, leading to a continuous decline in measurement accuracy. After long-term use, the measurement error could reach ±50mm. Moreover, its maintenance work was cumbersome, requiring regular inspection and replacement of the wire rope, consuming a large amount of manpower and material resources. More crucially, due to inaccurate measurement, the lifting platform often had positioning deviations, and goods were prone to collisions during handling, causing damage to the goods and equipment failures, which severely affected the normal operation efficiency of the warehousing center.

II. Working Principle of the RH External Slider Type Magnetostrictive Displacement Sensor

The RH external slider type magnetostrictive displacement sensor is mainly composed of a measuring rod, an electronic chamber, and an external slider magnetic ring. The measuring rod is made of high-strength, non-magnetic stainless steel, and a magnetostrictive waveguide wire is encapsulated inside. The electronic chamber integrates precise electronic circuits, which are responsible for generating and processing various signals. During operation, the electronic chamber generates an electrical current pulse. This pulse propagates along the magnetostrictive waveguide wire at a speed close to the speed of light and generates a circular magnetic field around the waveguide wire. The external slider magnetic ring is installed on the moving part of the vertical lifting equipment and moves synchronously in the vertical direction with it. The permanent magnet inside the magnetic ring generates a stable magnetic field. When the circular magnetic field generated by the electrical current pulse meets the magnetic field of the slider magnetic ring, based on the magnetostrictive effect, the waveguide wire will undergo a slight twist, generating a stress wave pulse, that is, a "return pulse". The electronic circuit of the sensor can accurately measure the time difference between the moment when the electrical current pulse is emitted and the moment when the "return pulse" is received. Since the propagation speed of the stress wave in the waveguide wire is constant, by multiplying the time difference by the propagation speed, the displacement of the slider magnetic ring relative to the measurement reference point can be accurately calculated, thereby obtaining the position information of the vertical lifting equipment in real time and accurately. This measurement method is based on a non-contact principle, avoiding mechanical wear and having extremely high measurement accuracy and stability.

III. Installation Process

(I) Installation Position Determination The technical team conducted an in-depth analysis of the structure and operation track of the vertical lifting equipment. Considering the vibration and airflow influence during the operation of the equipment and facilitating later maintenance, it was finally determined to install the measuring rod of the sensor on one side of the vertical lifting guide rail. This position can not only ensure that the external slider magnetic ring can slide smoothly on the measuring rod without being interfered by other components of the equipment during the vertical movement but also enable the sensor to stay away from harsh environment areas such as high temperature and high humidity, ensuring its stable operation. At the same time, in order to avoid the influence of the installation position on the measurement accuracy, a high-precision laser measuring instrument was used to repeatedly calibrate the installation position to ensure that the measuring rod is strictly parallel to the vertical lifting guide rail, with the deviation controlled within a very small range. (II) Installation Steps 1. **Measuring Rod Installation**: First, use a customized aluminum alloy installation bracket to fix the measuring rod at the selected position. The installation bracket has been specially designed with good seismic and anti-deformation performance. Fix the bracket firmly to the wall structure of the warehouse with expansion bolts to ensure that the measuring rod will not be displaced or shaken during the operation of the equipment. When fixing the measuring rod, use a high-precision level gauge for real-time monitoring to ensure that the perpendicularity error of the measuring rod is controlled within ±0.5mm, laying a foundation for subsequent accurate measurement. 2. **Slider Magnetic Ring Installation**: Install the external slider magnetic ring on the lifting platform of the vertical lifting equipment. During the installation process, ensure that the gap between the magnetic ring and the measuring rod is uniform, with the error of the gap around controlled within ±0.2mm to prevent the magnetic ring from rubbing or colliding with the measuring rod during the movement, affecting the measurement accuracy. At the same time, use a positioning tooling to ensure that the installation position of the magnetic ring is strictly aligned with the axis of the measuring rod, so that the magnetic ring can accurately follow the vertical movement of the lifting platform and precisely reflect the position change of the platform. 3. **Electronic Chamber Connection**: Install the electronic chamber near the control cabinet of the vertical lifting equipment for convenient wiring and subsequent maintenance. Use a special shielded cable to connect the electronic chamber with the measuring rod to ensure the stability of signal transmission and effectively avoid the influence of external electromagnetic interference on the measurement signal. After the connection is completed, fix and protect the cable to prevent it from being pulled or damaged during the operation of the equipment. At the same time, conduct an electrical performance test on the electronic chamber to ensure that all its parameters are normal and it can accurately receive and process the signals from the measuring rod.

IV. Actual Application Effects

(I) High-precision Measurement Since the installation of the RH external slider type magnetostrictive displacement sensor, the displacement measurement accuracy of the vertical lifting equipment has been improved qualitatively. Through actual testing, its measurement accuracy is stably up to ±0.1mm, which is hundreds of times higher than that of the traditional wire rope type displacement measurement device. During the daily cargo handling process, it can accurately transport the goods to the designated shelf level with minimal error, effectively avoiding the collisions and damages of goods caused by inaccurate positioning. For example, when handling a batch of high-value electronic products, with the high-precision measurement of this sensor, the goods can be safely and accurately placed at the target shelf position, greatly improving the safety and accuracy of cargo handling. (II) Enhanced Stability and Reliability This sensor adopts a non-contact measurement technology and has no mechanical moving parts, completely eliminating the hidden danger of measurement failures caused by mechanical wear. During the long-term operation process, it has withstood the tests of frequent starting and stopping of the equipment, high-speed operation, and the complex environment in the warehouse, and has always maintained a stable and reliable working state. According to statistics, in the past year of operation, the sensor did not have any measurement abnormalities caused by its own failures. In contrast, the previously used wire rope type displacement measurement device had an average of 3 to 4 failures per month due to problems such as wear and stretching. The high stability and reliability of the sensor have greatly improved the operation stability of the vertical lifting equipment, reduced the equipment shutdown and maintenance time, and ensured the efficient operation of the warehousing center. (III) Convenient Integration with the Automation System The standard 4-20mA current signal or digital signal output by the sensor can be easily integrated with the existing automation control system of the warehousing center. Through integration, the automation system can obtain the precise position information of the vertical lifting equipment in real time. Based on these accurate data, the system can intelligently plan the operation path and speed of the lifting equipment according to the storage requirements of the goods, realizing automated cargo storage and handling. At the same time, when the position of the equipment is abnormal, the system can immediately send out an alarm signal and take corresponding emergency braking measures to ensure the safety of the equipment and goods. For example, when the lifting platform is rising and the sensor detects that its position exceeds the preset range, the automation system will quickly cut off the power supply of the equipment to prevent the platform from continuing to rise and causing an accident, greatly improving the safety and intelligence level of the entire warehousing system.

V. Economic and Social Benefits

(I) Economic Benefits 1. **Reduction of Equipment Maintenance Costs**: The high reliability and stability of the RH external slider type magnetostrictive displacement sensor have significantly reduced the number of repairs of the vertical lifting equipment caused by displacement measurement failures. It is estimated that compared with the use of traditional measurement devices, the annual cost of equipment maintenance has been reduced by approximately 300,000 yuan. This includes the labor costs of maintenance personnel, the cost of replacing damaged components, and the production losses caused by equipment shutdown for maintenance. 2. **Improvement of Warehousing Operation Efficiency**: Due to the high-precision displacement measurement realized by the sensor, the positioning of the vertical lifting equipment is more accurate, and the cargo handling efficiency has been significantly improved. The cargo throughput of the warehousing center has increased by about 20% compared with the past, bringing more business revenue to the enterprise. At the same time, the reduction of goods damage and loss situations has reduced the operation losses of the enterprise, further improving the economic benefits. 3. **Extension of Equipment Service Life**: The precise displacement measurement enables the vertical lifting equipment to be more evenly stressed during operation, reducing the wear and fatigue of equipment components, thus extending the overall service life of the equipment. The original plan of carrying out large-scale equipment renewal every 5 years can now be extended to 8 to 10 years, saving a large amount of equipment renewal funds for the enterprise. (II) Social Benefits 1. **Upgrading of the Technical Level of the Logistics Industry**: The successful application of this sensor in the logistics and warehousing center provides an advanced displacement measurement solution for the entire logistics industry. Other logistics enterprises can draw on this case and introduce advanced sensor technology to improve their own automation level and operation efficiency, promoting the entire logistics industry to develop in a more intelligent and efficient direction. 2. **Ensuring the Safety of Goods and Personnel**: The high-precision displacement measurement effectively avoids the collisions and damages of goods during the handling process, ensuring the safety of goods. At the same time, the integration of the sensor with the automation system can promptly take safety measures when the equipment is abnormal, reducing the risk of injury to operators caused by equipment failures and creating a safer working environment for enterprise employees. 3. **Promoting Energy Conservation and Emission Reduction**: By improving the operation efficiency of the equipment and reducing the equipment failure rate, it reduces energy waste and unnecessary energy consumption. At the same time, extending the service life of the equipment means reducing the energy consumption and environmental pollution during the production and renewal of the equipment, which has a positive significance for promoting the energy conservation, emission reduction, and sustainable development of society.