Aerial Boom Oscillation Damping via Coupled Mode Control
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Solution Overview
Problem
Existing methods for actively damping oscillations in large articulated ladders, such as those exceeding 32 meters in height, fail to effectively consider the spatial distribution of material and coupling of bending and torsion, leading to inadequate damping of higher harmonics and increased oscillation excitation.
Innovation Solution
A control method that utilizes strain gauge sensors and gyroscopes to calculate reference signals, reconstructs oscillation modes, and generates a compensation angular velocity to dampen oscillations, accounting for the coupling of bending and torsion, and includes a dynamic model that separates fundamental oscillations from overtones, allowing for precise control of the telescopic boom and articulated arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If lumped-parameter models based on lumped-mass approximations are used for oscillation damping, then device complexity is reduced, but manufacturing precision and measurement precision deteriorate because they cannot adequately describe the elastic oscillations of large articulated ladders
Solution Approach 1:
The patent transitions from lumped-mass parameters to distributed-parameter models that account for the spatial distribution of mass and stiffness along the boom. This involves changing the mathematical representation from discrete mass-spring systems to continuous beam theory models that capture elastic oscillations and coupling effects throughout the structure.
Solution Approach 2:
The patent adds spatial dimensionality to the oscillation model by considering the distributed nature of the boom structure. Instead of treating the boom as a single rigid body with lumped masses, the model incorporates continuous spatial variations in mass and stiffness distributions, enabling accurate representation of elastic deformation modes.
2Device complexity
If only fundamental oscillation modes are damped, then device complexity is reduced, but manufacturing precision deteriorates because higher harmonics are not actively controlled
Solution Approach 1:
The patent implements damping control for multiple oscillation modes beyond just the fundamental mode. By actively controlling second and higher harmonics in addition to the fundamental oscillation, the system achieves superior trajectory accuracy and oscillation suppression, accepting the increased complexity as necessary for precise operation of large articulated ladders.
3Device complexity
If bending and torsion are treated as independent oscillations, then device complexity is reduced, but manufacturing precision deteriorates because coupled bending-torsional oscillations are not accurately modeled
Solution Approach 1:
The patent merges the separate bending and torsion models into a coupled bending-torsional oscillation model. This integration recognizes that in large articulated ladders, bending and torsional deformations are coupled through the articulated arm mechanism and material properties, requiring a unified mathematical framework that captures their interacting dynamics.
4Device complexity
If strain gauge sensors are positioned at the lower end of the boom, then device complexity is reduced, but measurement precision deteriorates because the signal-to-noise ratio is insufficient for detecting second harmonic oscillations
Solution Approach 1:
The patent utilizes the vertical dimension by positioning strain gauge sensors at the upper end of the boom rather than the lower end. This spatial repositioning exploits the different vibration mode shapes at different locations along the boom, where the upper position provides better sensitivity to second harmonic oscillations and improves the signal-to-noise ratio for detecting higher frequency components.
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 method provides effective oscillation damping across both elevation and rotation axes, reducing excitation and maintaining precise control of the ladder's position, even at extended lengths, by accurately accounting for the spatial distribution of material and coupled oscillation modes.
Implementation Method 1
strain gauge (SG) sensors for detecting a bending state of the telescopic boom
Implementation Method 2
an additional two- or three-axis gyroscope attached within the upper part of the telescopic boom for measuring the angular velocity
Implementation Method 3
A controller is provided for controlling the movement of the aerial apparatus on the basis of signal values that are gained from the SG sensors and the gyroscope. During operation, and especially when an input command for moving the aerial apparatus is passed to the controller, the present oscillation status is taken into account by means of processing the signal values, so that the movement of the ladder can be corrected such that the tip of the ladder reaches and maintains a target position despite the elastic flexibility of the boom.
Data Source
Figure 1a~1b
Figure 2~3
Figure 4
AI summary
Method for controlling an aerial apparatus with a telescopic boom (12), strain gauge (SG) sensors (18) for detecting the bending state of the telescopic boom (12) in a horizontal and a vertical direction, a gyroscope (16) attached to the top of the telescopic boom (12) and control means for controlling a movement of the aerial apparatus on the basis of signal values gained from the SG sensors and the gyroscope, said method comprising the following steps: - obtaining raw signals SGRaw, GYRaw from the SG sensors (18) and the gyroscope (16), - calculating reference signals from the raw signals SGRaw , GYRaw, including an SG reference signal SGRef, representing a strain value, and a gyroscope reference signal GYRef, representing an angular velocity value, and an angular acceleration reference signal AARef derived from angular position or angular velocity measurement values, - reconstructing a first oscillation mode f1 and at least one second oscillation mode f2 of higher order than the first oscillation mode f1 from the reference signals and additional model parameters PAR related to the construction of the aerial apparatus, - calculating a compensation angular velocity value AVComp from the reconstructed first oscillation mode f1 and at least one second oscillation mode f2 , - adding the calculated compensation angular velocity value AVComp to a feedforward angular velocity value to result in a drive control signal.