Crane Cable Length Control for Pendulum Damping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cranes face inefficiencies in handling loads due to pendulum movements, which can cause delays as loads often swing at the destination, requiring time to settle or manual intervention to dampen oscillations, thereby affecting throughput.
Innovation Solution
A method where a control device adjusts the cable length of a crane's cable system to ensure a defined pendulum state at the destination by determining a time course for the movement of the load suspension point, allowing the load to reach its destination with a specified deflection angle and its derivative, regardless of whether the pendulum is excited or not.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the load is moved quickly to the destination, then productivity is improved, but the load swings at the destination requiring wait time or manual intervention
Solution Approach 1:
The control device calculates and applies a specific cable length profile during the approach phase that proactively prepares the load for arrival. By adjusting the cable length in advance according to the calculated profile, the system ensures the load arrives at the destination with minimal swing, eliminating the need for post-arrival damping or waiting
Solution Approach 2:
The system dynamically changes the cable length parameter during movement based on a calculated profile. This parameter change is coordinated with the trolley position and velocity to achieve optimal load behavior at the destination, transforming the static cable length into a dynamic control variable that actively manages pendulum motion
2Stability of the object's composition
If sway control is applied to dampen pendulum movements, then load stability is improved, but the handling time increases
Solution Approach 1:
Instead of reacting to swings after they occur, the system performs preliminary action by calculating and applying the optimal cable length profile before the load reaches the destination. This proactive approach prevents excessive swinging rather than dampening it, maintaining stability without the time penalty of active damping control
Solution Approach 2:
The system converts the natural pendulum motion, which is typically harmful, into a beneficial effect by using the cable length adjustments to guide the load's swing characteristics. The pendulum motion itself becomes part of the control mechanism rather than an obstacle to be suppressed
3Stability of the object's composition
If manual intervention is used to dampen oscillations, then load stability is improved, but operation complexity increases
Solution Approach 1:
The control device autonomously calculates and implements the cable length profile without operator intervention. The system serves itself by using sensor data (trolley position, velocity, cable length) to automatically determine and apply the optimal control profile, eliminating the need for manual damping operations
Solution Approach 2:
The system continuously monitors trolley position, velocity, and cable length, using this feedback to adjust the cable length profile in real-time. This closed-loop control ensures the load arrives at the destination with minimal swing while maintaining full automation
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 enables time-optimal load handling by ensuring the load reaches its destination with a controlled pendulum state, eliminating the need for damping and reducing wait times, thus improving crane efficiency and throughput.
Implementation Method 1
a load (6) is suspended from a load suspension point (2) via a cable system (5)
Implementation Method 2
an initial deflection angle φ0 of a pendulum movement (11), which the load (6) executes during the movement of the load suspension point (2)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A load (6) is suspended from a load suspension point (2) of a crane (1) via a cable system (5). A control unit (7) moves the load suspension point (2) to a destination (x2) by actuating a drive (3', 5'). During the movement of the load suspension point (2), the control unit (7) sets a cable length (L) of the cable system (5) by actuating a hoist (5'). The control unit (7) is given an initial cable length (L0), a target cable length (L1) to be reached at the destination (x2), and an initial deflection angle (ϕ0) of a pendulum motion that the load (6) performs during the movement of the load suspension point (2) to the destination (x2), and/or an initial derivative (φ̇) of the deflection angle (ϕ). The control device (7) determines a time course of the cable length (L) for a given time course of the movement of the load suspension point (2) and sets the cable length (L) according to the determined time course.Alternatively, the control unit (7) also determines the temporal progression of the movement of the load suspension point (2) and controls the drive (3', 1') accordingly. In both cases, the determination is carried out such that at the target location (x2) the deflection angle (ϕ) and/or the time derivative (φ̇) of the deflection angle (ϕ) assume a defined final value (ϕ1, φ̇1).