Optimization of Pallet Stacking/Feeder Synchronous Lifting System: Multi-Hydraulic Cylinder Precision Coordination and Anti-Eccentric Load Control Strategy
Optimization of Synchronous Lifting System for Stacking Plate Feeder: Research on Precision Coordination and Anti-Off-center Load Control Strategy of Multi-Hydraulic Cylinders
Abstract As a key piece of equipment in automated block production lines, the precision and stability of the synchronous lifting system of the stacking plate feeder directly affect the stacking quality and equipment reliability. This paper addresses the synchronization error and off-center load issues in multi-hydraulic cylinder collaborative control, proposing an optimization scheme based on high-precision displacement sensing closed-loop feedback and adaptive PID control algorithm. By establishing a synchronous motion model of the hydraulic cylinders and designing a pressure-displacement dual-variable collaborative control strategy, the synchronous lifting error is achieved to ≤±0.3mm, and the stacking qualification rate is increased to 99.5%. This research provides a systematic technical path and engineering practice reference for high-precision and high-reliability lifting control in block production lines.
Keywords Stacking plate feeder; Synchronous lifting system; Multi-hydraulic cylinder coordination; Precision control; Anti-off-center load strategy; Adaptive PID; Displacement sensing; Stacking precision
1. Introduction
In automated block production lines, the stacking plate feeder undertakes the core functions of block stacking and conveying. The synchronization accuracy of the lifting system directly affects the neatness of the block stacking and the production line cycle time, while off-center loading can lead to equipment jamming, hydraulic system overload, and even structural deformation. Traditional control methods mostly rely on mechanical synchronization or open-loop hydraulic control, which are difficult to adapt to dynamic load changes. This paper explores an integrated control strategy for high-precision coordination and off-center loading suppression using multiple hydraulic cylinders through theoretical modeling and experimental verification, aiming to improve the operational stability and production efficiency of the stacking plate feeder.
2. Working Principle and Challenges of Multi-Hydraulic Cylinder Synchronous Lifting System
2.1 System Composition
A typical stacking plate feeder lifting system includes:
Hydraulic power unit: fixed displacement pump, proportional valve group, accumulator;
Actuator: 4-6 sets of hydraulic cylinders, distributed support lifting platform;
Sensing system: magnetostrictive displacement sensor, pressure transmitter, inclinometer;
Controller: PLC and motion control module.
2.2 Key Technical Challenges
Insufficient Synchronization Accuracy: Manufacturing errors in the hydraulic cylinder and uneven pressure drop in the oil circuit lead to asynchronous lifting;
Significant Off-center Load Effect: Uneven block distribution or conveying offset causes single-cylinder overload;
Lapse-lagging Dynamic Response: Traditional PID parameters are fixed and difficult to adapt to sudden load changes.
3. Multi-Hydraulic Cylinder Precision Cooperative Control Model
3.1 Synchronization Error Modeling
The displacement error of the i-th hydraulic cylinder,
Fiadjusted=Fidefault+α⋅(Pavg−Pi)
(t) is the real-time displacement,
n is the number of hydraulic cylinders. The synchronization control objective is to minimize
3.2 Adaptive PID Control Algorithm
Design a variable gain PID controller:
ui(t)
= Kp(t)
ei(t)
+ Ki(t)
∫ ei(t)
dt
+ Kd(t)
de(t)
dt
ui(t)=Kp(t)ei(t)+Ki(t)∫ei(t)dt+Kd(t)
dt
dei(t)
where Kp, Ki, KdKp, Ki, KdKp, Ki, KdKp Adjustments are made in real time based on the error change rate, and online optimization is achieved through an RBF neural network.
3.3 Collaborative Communication Architecture
High-speed data exchange between multiple cylinders is achieved using a CAN bus (1Mbps baud rate), with a control cycle ≤10ms.
4. Anti-Off-center Load Control Strategy Design
4.1 Off-center Load Detection Mechanism
Pressure distribution monitoring: Inlet and outlet pressure sensors for each cylinder calculate load deviation in real time;
Platform tilt angle detection: A dual-axis tilt meter monitors the platform's levelness (accuracy ±0.05°);
Image-assisted verification: A vision system identifies the block stacking status.
4.2 Dynamic Force Distribution Algorithm
Dynamically adjusts the output force of each cylinder based on pressure feedback:
Fiadjusted = Fidefault + α ⋅ (Pavg − Pi)
Fiadjusted
=Fidefault
+α⋅(Pavg − Pi)
Where
Pavg is the average pressure,
α is the compensation coefficient.
4.3 Safety Protection Logic
Triggers slow descent and alarm when single-cylinder pressure exceeds the threshold;
Automatically executes platform reset when off-center load continues to exceed limits;
Switches to "single-cylinder priority" emergency mode in fault condition.
5. System Implementation and Experimental Verification
5.1 Hardware Configuration
Hydraulic Cylinder: Stroke 800mm, maximum load 5t;
Sensors: Magnetostrictive displacement sensor (accuracy ±0.01mm), pressure transmitter (accuracy 0.5%FS);
Controller: Siemens S7-1500PLC+TM motion control module.
5.2 Synchronization Accuracy Test
Tested under full load (4.8t) and off-center load (±30% load deviation):
Working Condition | Traditional Control Synchronization Error | Optimized Synchronization Error | Improvement Amount
Full Load Balance | ±1.2mm | ±0.25mm | 79%
30% Left Off-center Load | ±2.5mm | ±0.28mm | 89%
Dynamic Lifting (1Hz) | ±1.8mm | ±0.30mm | 83%
5.3 Long-Term Operational Stability
Monitoring after 72 hours of continuous production showed:
Stacking qualification rate increased from 97.1% to 99.5%;
Hydraulic system failure rate decreased by 40%;
Platform reset time was shortened from 12s to 5s.
6. Engineering Application and Benefit Analysis
6.1 Production Line Adaptability
This solution has been successfully applied to three mainstream stacking and feeding machine models, with a modification cycle of ≤3 days. It supports the following extended functions:
Data interface with the production line MES system;
Remote diagnostics and parameter optimization;
Energy consumption statistics and early warning reports.
6.2 Quantification of Economic Benefits
Taking a production line with an annual output of 20 million blocks as an example:
Reducing block breakage losses by approximately RMB 120,000/year;
Reducing hydraulic system maintenance costs by RMB 80,000/year;
Increasing equipment utilization leads to a capacity gain of approximately 5%.
6.3 Industry Promotion Value
Provides technical reference for GB/T 35031-2018 "Automatic Block Production Line";
Can be extended to other multi-cylinder synchronous lifting scenarios (such as mold lifting and material transfer).
7. Conclusion and Outlook
This paper effectively solves the problems of synchronous accuracy and off-center load control of multi-hydraulic cylinders in stacking and feeding machines through the integrated application of high-precision sensing, adaptive control, and dynamic force distribution technology. Experiments show that the optimized system has a synchronization error of ≤±0.3mm and a stacking qualification rate of 99.5%, significantly improving the automation level and operational reliability of the block production line. Future research directions include:
Digital twin technology application: establishing a virtual commissioning platform to simulate off-center load response strategies;
AI predictive maintenance: predicting the lifespan of hydraulic components based on historical data;
Green hydraulic technology: further reducing energy consumption by combining with variable frequency pump stations.
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