Active Vibration Damping for Container Cranes Using Linear Motors

Solution Overview

Problem

Container crane vibrations cause inefficiencies in loading and unloading operations due to excessive oscillation, leading to increased waiting times and costs, as traditional methods like increasing rigidity or using passive vibration absorbers require significant structural changes or heavy oscillating masses.

Innovation Solution

An active vibration damping system incorporating a vibration sensor, a linear motor, and a control device with a cascaded control system, allowing for parameterization of oscillation frequency and damping, which can be integrated into existing crane systems without major structural changes, using a significantly lighter moving mass to effectively dampen crane frame vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the crane gantry is built more rigidly to reduce vibration, then vibration amplitude is reduced, but structural changes including track width, cross-sectional areas and headroom are required which are extremely problematic

Engineering Contradiction:

Improvecrane vibration amplitudeVSAvoidstructural changes required

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces the passive mechanical vibration absorption system with an active control system using linear motors. Instead of relying on heavy oscillating masses and mechanical dampers, the system uses controlled electromagnetic forces from linear motors to generate counteracting vibrations that cancel out crane frame vibrations, thereby avoiding the need for heavy mechanical components and structural modifications.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system changes the approach from static structural modification to dynamic parameter control. By controlling the motion parameters (position, speed, acceleration) of counterweights via linear motors, the system dynamically adjusts the counteracting forces to match the varying vibration characteristics of the crane, eliminating the need for fixed structural changes.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If passive vibration absorbers with heavy oscillating masses are used to dampen crane vibrations, then vibration damping effectiveness is improved, but the weight and complexity of the system increases significantly

Engineering Contradiction:

Improvevibration damping effectivenessVSAvoidoscillating mass

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent replaces the passive mechanical vibration absorption system with an active control system using linear motors. Instead of relying on heavy oscillating masses and mechanical dampers, the system uses controlled electromagnetic forces from linear motors to generate counteracting vibrations that cancel out crane frame vibrations, thereby avoiding the need for heavy mechanical components and structural modifications.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system transitions from a static passive absorption system to a dynamic active control system. The linear motors enable real-time adjustment of counterweight motion parameters (position, speed, acceleration) to dynamically counteract varying vibration conditions, replacing the fixed heavy masses of passive systems with lightweight actively controlled components.

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If passive vibration absorbers are used to reduce crane vibrations, then vibration amplitude is reduced, but significant waiting time is required for vibrations to subside to tolerable minimum levels

Engineering Contradiction:

Improvevibration amplitudeVSAvoidwaiting time for vibration to subside

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The system applies preliminary counteracting action by continuously generating control forces that oppose and cancel out vibrations in real-time. Rather than waiting for vibrations to naturally subside, the linear motors produce counter-vibrations that actively neutralize the harmful oscillations, allowing container handling operations to proceed without interruption.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system employs feedback control by continuously monitoring crane frame vibrations and adjusting the linear motor control forces accordingly. The control device processes vibration data and dynamically adjusts the counteracting forces to maintain vibration suppression, enabling real-time response rather than passive waiting for vibration decay.

Inventive Principle:

Principle #23Feedback

4Object-affected harmful factors

If conventional vibration absorbers are used, then some vibration damping is achieved, but the system cannot adapt to changing vibration frequencies and conditions

Engineering Contradiction:

Improvevibration dampingVSAvoidadaptation to changing vibration conditions

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The system transitions from a static passive absorption system to a dynamic active control system. The linear motors enable real-time adjustment of counterweight motion parameters (position, speed, acceleration) to dynamically counteract varying vibration conditions, replacing the fixed heavy masses of passive systems with lightly-weighted actively controlled components.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the approach from static structural modification to dynamic parameter control. By controlling the motion parameters (position, speed, acceleration) of counterweights via linear motors, the system dynamically adjusts the counteracting forces to match the varying vibration characteristics of the crane, eliminating the need for fixed structural changes.

Inventive Principle:

Principle #35Parameter changes

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

The system reduces crane vibrations efficiently, minimizing waiting times and costs by actively controlling the linear motor to generate counterforces, achieving effective damping with much lower moving masses compared to passive absorbers, and allowing for easy adaptation to changing conditions, with reduced maintenance needs.

Implementation Method 1

a linear motor (14) which can be mounted on a crane frame (21)

Methodology Applied

Scientific EffectLinear motor: Linear Motor

Implementation Method 2

a vibration sensor (11) which can be mounted on a crane frame (21)

Methodology Applied

Scientific EffectVibration detection: Vibration

Implementation Method 3

a mass (15) which can be moved by the linear motor (14) and is mechanically coupled to the crane frame (21)

Methodology Applied

Scientific EffectInertia: Inertia

Data Source

PatentEP2327651B1System for attenuating the oscillation of a container crane

Publication Date: 2012.08.01 SIEMENS AG

AI summary

The system is provided with a frame vibration sensor (11) mounted on a crane. A frame (21) is mounted on the crane linear motor (14). A mass is coupled to the crane frame mechanically. A regulatory body is associated to the vibration sensor. A control variable output is connected to the linear motor.