Crane Cable Length Control for Pendulum Damping
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Solution Overview
Problem
Existing crane control methods cannot effectively dampen pendulum movements orthogonal to the trolley's direction of travel, such as side sway, which reduces handling capacity and requires manual intervention or waiting for the movement to subside.
Innovation Solution
A method where a control device adjusts the cable length of a crane system by determining a resulting desired length from a basic and additional length, with the additional length changing at twice the pendulum frequency, minimizing at reversal points and maximizing at zero crossings, to dampen pendulum movements regardless of their orientation relative to the trolley's direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the trolley movement is used to dampen pendulum movements, then pendulum movements parallel to the trolley's direction of travel can be damped, but pendulum movements orthogonal to the trolley's direction of travel (side sway) cannot be damped
Solution Approach 1:
The patent applies dynamics by making the cable length adjustable and variable during operation. The control device dynamically changes the cable length in response to detected pendulum movements, allowing the system to adapt to different oscillation conditions. This dynamic adjustment enables the cable length to act as an active damping element that can counteract pendulum movements in any direction, not just those parallel to the trolley's travel path.
Solution Approach 2:
The patent utilizes parameter changes by modifying the cable length parameter in response to detected pendulum oscillations. The control device detects the pendulum frequency and phase, then adjusts the cable length parameter accordingly to provide damping. This parameter adjustment can effectively dampen oscillations in any direction, overcoming the limitation of fixed-geometry damping systems that only work for specific orientations.
2Productivity
If manual intervention or waiting is used to handle pendulum movements, then handling capacity is reduced, but automated control systems are required
Solution Approach 1:
The patent implements self-service by enabling the crane system to automatically detect and dampen its own pendulum movements without external intervention. The control device continuously monitors the load's oscillation and autonomously adjusts the cable length to counteract the movements. This self-regulating capability eliminates the need for manual intervention or waiting, thereby maintaining full handling capacity while using a relatively simple control architecture.
Solution Approach 2:
The patent employs feedback by using the control device to detect pendulum movement characteristics (frequency, phase) and using this information to drive cable length adjustments. The system continuously monitors the load's oscillation state and adjusts the damping action accordingly, creating a closed-loop control system that automatically maintains stability without requiring complex external intervention protocols.
3Stability of the object's composition
If the cable length is adjusted to dampen pendulum movements, then oscillation damping is achieved, but the trolley's movement capability must not be affected
Solution Approach 1:
The patent applies segmentation by separating the damping function from the transport function. The cable length adjustment mechanism operates independently to provide damping, while the trolley maintains its normal transport operations. This functional segmentation allows the damping system to act on the load without interfering with the trolley's movement capability, as the two functions are implemented through separate control pathways.
Solution Approach 2:
The patent uses dynamics by implementing time-varying cable length adjustment that is synchronized with the pendulum oscillation frequency. The damping action is applied dynamically in response to the oscillation state, allowing the system to provide stabilization only when needed while leaving the trolley's transport function unaffected. This dynamic approach ensures that damping adjustments do not impose speed limitations on normal operations.
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
Enables automated and reliable damping of pendulum movements in both parallel and orthogonal directions to the trolley's travel, improving handling capacity and operation efficiency without affecting the trolley's movement.
Implementation Method 1
a pendulum movement of a load (6), which is suspended from a load suspension point (2) of the crane (1) via a cable system (5), takes place around the load suspension point (2), is related to a vertical plane (11) containing the load suspension point (2) and has a pendulum frequency (f1)
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A load (6) is suspended from a load suspension point (2) of a crane (1) via a cable system (5). To control a pendulum motion of the load (6) about the load suspension point (2), which is referenced to a vertical plane (11) containing the load suspension point (2) and has a pendulum frequency (f1), a control device (7) of the crane (1) receives data (D) during the pendulum motion that are characteristic of a deflection angle (ϕ) of the pendulum motion and/or a time derivative (ϕ') of the deflection angle (ϕ) of the pendulum motion. The control device (7) sets an effective cable length (L) of the cable system (5) during the pendulum motion according to a resulting setpoint length (L*). The control unit (7) determines the resulting length setpoint (L*) based on the sum of a basic length setpoint (L1*) and an additional length setpoint (L2*).The control device (7) determines the additional length setpoint (L2*) such that the additional length setpoint (L2*) changes with a modulation frequency (f2) that is equal to twice the pendulum frequency (f1), and that the additional length setpoint (L2*) is minimal at the reversal points of the pendulum motion and maximal at the zero crossing of the pendulum motion.