Hoisting Assembly Resonance Control via Movable Block Positioning
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Solution Overview
Problem
Heavy lifting systems in marine environments face vertical resonance issues due to changing natural frequencies with load depth, leading to dangerous movements and potential equipment failure from peak loads exceeding breaking limits.
Innovation Solution
A hoisting assembly with an upper and lower movable block system, where rope lengths are controlled to vary the equivalent spring coefficient, allowing for optimization of the system's response to excitations and reduction of resonance by positioning the upper movable block between the fixed and lower movable blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the hoisting assembly uses a fixed cable length, then the structure is simple, but the natural frequency cannot be adjusted to avoid resonance
Solution Approach 1:
The hoisting assembly is divided into multiple segments: an upper movable block, a lower movable block, and a multi-rope system. The upper movable block can be positioned at different distances from both the upper fixed block and the lower movable block, creating adjustable cable segments that allow natural frequency tuning without requiring a complete redesign of the hoisting system.
Solution Approach 2:
The system transitions from a static cable length to a dynamic configuration where the upper movable block can be repositioned along the cable. This dynamic adjustment capability allows the natural frequency to be changed in response to varying operational conditions, depth requirements, and resonance risks, while maintaining a relatively simple overall structure.
2Length of moving object
If the cable length is increased to lower the load deeper, then the lowering depth is improved, but the natural frequency decreases and may cause resonance
Solution Approach 1:
The system allows dynamic adjustment of the upper movable block's position to change the effective cable length and natural frequency. When lowering depth increases and natural frequency decreases, the upper movable block can be repositioned to adjust the cable segments, thereby tuning the natural frequency away from resonance zones and maintaining system reliability throughout the entire lowering depth range.
Solution Approach 2:
The invention changes the physical parameters of the hoisting system by adjusting the distances between blocks, which alters the cable segment lengths and cross-sectional area distribution. This parameter adjustment allows the natural frequency to be optimized for different operating conditions, preventing resonance even when lowering depth varies significantly.
3Reliability
If the natural frequency is tuned to avoid resonance, then the system response to excitations is reduced, but the device complexity increases
Solution Approach 1:
By segmenting the hoisting assembly into multiple movable blocks with adjustable positions, the system creates independent adjustment zones. The upper movable block can be positioned to create specific cable segment lengths and areas, enabling natural frequency tuning without requiring complex control systems or additional components beyond the basic block and tackle mechanism.
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 effectively limits vertical resonance and allows for controlled operation of the hoisting system across varying depths, reducing the risk of equipment damage and personnel safety hazards by optimizing the system's response to external excitations.
Implementation Method 1
the hoisting assembly, in combination with the heavy object which is hoisted, may form a mass-spring system in which the hoisting assembly functions as a spring
Implementation Method 2
vertical (or axial) resonance may occur in the system... Under certain conditions, the natural frequency of the system which is outlined above may become the same as the frequency of excitations. In this case, resonance may occur and the heavy object may start to undergo substantial movements.
Data Source
AI summary
A hoisting assembly for lifting or lowering a heavy object includes an upper fixed block, an upper movable block being suspended from the upper fixed block by at least one first rope which is reeved into one or more first rope lengths between the upper fixed block and the upper movable block, a lower movable block being connected to the upper movable block by at least one second rope which is reeved into one or more second rope lengths between the upper fixed block and the upper movable block. The first and second ropes are reeved in such a way that in use the upper movable block can be positioned at a distance greater than zero from the upper fixed block and at a distance greater than zero from the lower movable block by controlling the lengths of the first and second ropes.