Luffing Jib Crane Automated Speed Control
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Solution Overview
Problem
Conventional luffing jib cranes lack automated control to prevent unwanted jib movements and cable slack during lifting or lowering, leading to potential damage from dynamic jolts or abrupt breaks, which requires continuous manual intervention by the driver.
Innovation Solution
An automated method that acquires and compares the desired and actual angular speeds of the jib using a control/command system, including a lifting speed command manipulator, converter, angle sensor, and kinematic model, to automatically stop the lifting motor when a predefined deviation occurs, ensuring the jib remains immobile and preventing unwanted displacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If manual intervention by the crane driver is used to stop jib movement and prevent cable slack, then the crane can be operated with simple equipment, but continuous driver attention is required and unwanted movements cannot be prevented automatically
Solution Approach 1:
The control system continuously monitors the actual angular speed of the jib and compares it with the theoretical angular speed derived from the motor command. When a deviation exceeds a threshold, the system automatically stops the lifting motor, creating a closed-loop feedback control mechanism that prevents unwanted movements without requiring continuous manual intervention.
Solution Approach 2:
The patent replaces the mechanical/manual control system with an automated electronic control system that uses sensors, converters, and microprocessors to monitor and control jib movement. This substitution eliminates the need for continuous driver attention while providing more precise and reliable control.
2Reliability
If the lifting motor operates without automated speed monitoring, then the device structure remains simple, but cable slack and sudden cable adjustments can occur causing potential damage
Solution Approach 1:
The control system performs preliminary calculations of the theoretical angular speed based on the motor command before the actual movement occurs. This allows the system to predict the expected jib behavior and compare it with actual measurements in real-time, enabling preventive action before cable slack or sudden adjustments can occur.
Solution Approach 2:
The system continuously compares actual angular speed measurements with theoretical values and automatically stops the motor when deviations indicate potential problems, creating a real-time feedback mechanism that prevents cable damage before it occurs.
3Productivity
If continuous driver attention is required to prevent unwanted jib movements, then no additional control systems are needed, but productivity is reduced due to constant manual monitoring
Solution Approach 1:
The control system performs self-monitoring and self-correction by automatically detecting speed deviations and stopping the motor without external intervention. This allows the crane to monitor and correct its own operation, freeing the driver from continuous attention requirements while maintaining high productivity.
Data Source
AI summary
A method for securing a luffing jib crane includes: acquiring a lifting/lowering setpoint; piloting a lifting motor by a converter that applies a motor command speed as a function of the setpoint; driving, in lifting or in lowering, the jib by a lifting cable under the action of the lifting motor; calculating, by a control/command system, a lifting/lowering theoretical angular speed from the motor command speed or from the setpoint; calculating, by the control/command system, a lifting/lowering actual angular speed from a jib angle measured by an angle sensor; comparing the actual angular speed and the theoretical angular speed; and commanding the stopping of the lifting motor according to the result of the comparison.