Crane Load Swing Control via Dynamic Safety Zones
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Solution Overview
Problem
Existing crane control systems fail to effectively prevent collisions when loads can swing around the upper load suspension point, particularly during emergency stops, as prior solutions assume rigid load connections and do not account for pendulum motion.
Innovation Solution
A dynamic control method that determines inner and outer safety zones based on crane state variables, including position, travel speed, pendulum length, and wind effects, to adjust movement or alert operators, thereby reducing the risk of collisions by managing travel speed and stopping the load safely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If emergency stop is triggered to prevent collision, then the upper load suspension point stops immediately, but the load continues to swing and may collide with obstacles
Solution Approach 1:
The control device determines the safety zone in advance based on state variables (position, speed, pendulum length) before triggering emergency stop. This preliminary calculation allows the system to predict the load's swing trajectory and set appropriate safety boundaries, enabling reliable collision prevention while maintaining operator control awareness.
Solution Approach 2:
The system continuously monitors state variables (position, travel speed, pendulum length) and uses this feedback to dynamically adjust the safety zone. This closed-loop feedback mechanism ensures that the safety zone remains accurate even as the load swings, resolving the contradiction between immediate stopping and collision prevention.
2Reliability
If the control device determines safety zone dynamically based on state variables, then collision protection is improved, but the device complexity increases
Solution Approach 1:
The control device uses parameter changes in state variables (position, speed, pendulum length) to dynamically adjust the safety zone. By monitoring how these parameters change and relating them to safety zone boundaries, the system achieves adaptive collision protection without requiring complex additional hardware or algorithms.
Solution Approach 2:
The safety zone is made dynamic rather than static, adjusting automatically based on real-time state variables. This dynamic approach allows the safety zone to expand or contract according to the load's motion state, providing reliable collision protection while keeping the control logic manageable through physics-based relationships.
3Adaptability or versatility
If the load is suspended on a cable allowing swing, then flexibility of operation is improved, but collision risk increases during emergency stop
Solution Approach 1:
The control device calculates the safety zone in advance based on the pendulum length and state variables before emergency stop occurs. This preliminary determination accounts for the flexible cable-suspended load's potential swing path, enabling the system to maintain operation flexibility while pre-establishing collision-free boundaries.
Solution Approach 2:
The safety zone determination incorporates the vertical dimension through pendulum length, transforming a two-dimensional position-based safety approach into a three-dimensional solution. This accounts for the load's ability to swing in space, maintaining operational flexibility while preventing collisions through spatial awareness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures reliable collision prevention by dynamically adjusting the crane's movement to account for swinging loads, effectively mitigating the risk of collisions during both manual and automated operations, even with large pendulum lengths.
Implementation Method 1
an upper load suspension point from which a load is suspended via a cable system, so that the load can swing around the upper load suspension point
Implementation Method 2
a load is suspended via a cable system, so that the load can swing around the upper load suspension point
Implementation Method 3
the control device dynamically repeatedly determines an inner safety zone around the load depending on state variables of the crane, that the state variables at least a position of the upper load suspension point, a travel speed of the upper load suspension point and an effective pendulum length of the load around the upper load suspension point include
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A crane has an upper load suspension point (1), from which a load (3) is suspended via a cable system (2) such that the load (3) can swing about the upper load suspension point (1). A control unit (9) of the crane controls drives (4a, 4b) of the crane so that the upper load suspension point (1) and, together therewith, the load (3) are moved by the control unit (9) according to its actuation. As the upper load suspension point (1) is moved, the control unit (9) repeatedly determines dynamically an inner safety zone (13) around the load (3) according to state variables (x, v, 1, φ1, ω, vW) of the crane. The state variables (x, v, 1, φ1, ω, vW) comprise at least a position (x) of the upper load suspension point (1), a speed of movement (v) of the upper load suspension point (1) and an effective pendulum length (1) of the load (3) about the upper load suspension point (1). The control unit (9) checks, on the basis of further information known by the control unit (9), whether an object (14) different from the load (3) has entered the inner safety zone (13). As soon as an object (14) enters the inner safety zone (13), the control unit (9) stops the movement of the upper load suspension point (1) or outputs a message (M) to stop the movement of the upper load suspension point (1) to an operator (12) of the crane. Otherwise, the control unit (9) maintains the movement of the upper load suspension point (1) or does not output a message (M) to stop the movement of the upper load suspension point (1) to the operator (12) of the crane.