Jib Crane Control System Feedforward Distance Regulation
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Solution Overview
Problem
Existing control systems for cranes with articulated jibs and hoists face challenges in accurately and efficiently managing the distance between the load and the crane tip, as the motion of the jib undesirably affects the hoist, requiring continuous measurement and correction.
Innovation Solution
A method and control system that utilize a feedforward approach to generate a correcting signal and activate the hoist actuators before the undesired motion occurs, thereby minimizing errors and improving precision by proactively adjusting the hoist movement in sync with jib motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback-based regulation loop is used to correct the distance change, then the system can maintain accurate distance control, but the correction speed is limited and continuous measurement is required
Solution Approach 1:
The patent applies preliminary action by calculating the expected distance change based on jib motion parameters before the actual change occurs. The control system uses the relationship between jib angle/length changes and cable length changes to proactively determine the correcting signal, rather than waiting for feedback measurement. This eliminates the delay inherent in feedback-based systems.
Solution Approach 2:
The patent introduces an intermediary calculation model that relates jib motion parameters (angle, length) to cable length changes. This mathematical model acts as a mediator that translates jib actuator commands into predicted hoist corrections, enabling faster response without direct continuous measurement of the actual distance change.
2Measurement precision
If continuous measurement and correction is implemented, then distance control accuracy is maintained, but the system complexity and computational load increase
Solution Approach 1:
The patent extracts only the essential parameters needed for correction (jib angle and length changes) from the complex state of the entire crane system. By focusing only on these critical parameters and their mathematical relationship to cable length, the system achieves accurate control without the complexity of measuring and processing all possible state variables.
Solution Approach 2:
The patent transforms the control approach by changing from direct measurement of physical distance to calculation based on jib motion parameters. This parameter transformation simplifies the control system by using easily measurable jib parameters (angle, length) that directly relate to cable length through known geometric relationships, reducing the need for complex sensing and computation.
3Reliability
If correction is made after undesired motion occurs, then the system can respond to actual changes, but the correction is delayed and less precise
Solution Approach 1:
The system performs preliminary calculation of the correcting signal based on the commanded jib motion parameters before the motion is executed. By using the known relationship between jib parameters and cable length, the system determines the required hoist correction in advance, eliminating the time delay associated with measuring and reacting to actual distance changes after they occur.
Data Source
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AI summary
A method for controlling a crane (2) comprising a jib (4) having a crane tip (16) and a hoist (6) comprising a load connection structure (28), wherein the crane (2) configured to carry a load (14) and comprises: - one or more of jib actuators (8) arranged to activate the jib (4); - one or more hoist actuators (10) arranged to activate the hoist (6); - a control unit (12) configured control the one or more jib actuators (8) and the one or more hoist actuators (10) configured to change the distance (D) between the load connection structure (28) and the crane tip (16). The method comprises the step of providing a command (CA, CB) to the control unit (12) to activate the one or more jib actuators (8). The method comprises the following steps: - determining the change (ΔDjib) of the distance (D) between the load connection structure (28) and the crane tip (16) caused by motion of the jib (4) when executing the command (CA, CB); - determining a correcting signal (CS) suitable for at least partly counteracting the change (ΔDjib) of the distance (D) between the load connection structure (28) and the crane tip (16); - activating the one or more hoist actuators (10) by using the determined correcting signal (CS).