Excavator Overload Warning via Contact Force Stability Formula
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Solution Overview
Problem
Existing overload warning systems for excavators, such as hydraulic excavators, face challenges in accurately determining static stability, particularly when the equipment position is unknown or changed, and fail to provide timely warnings when the device is inclined, leading to potential tilting or tipping issues.
Innovation Solution
A generic overload warning system that determines and orders contact forces at multiple contact points, using measured forces to calculate static stability through a specified formula, eliminating the need for angle measurements or pre-calculations, and allowing for accurate stability assessment regardless of configuration changes or inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hydraulic pressure in the lift cylinder is monitored alone without considering equipment position, then the monitoring system is simple, but the accuracy of overload determination is poor with up to 40% difference between calculated tilting load and actual load-carrying capacity
Solution Approach 1:
The patent combines multiple measurement parameters (hydraulic pressure, boom angle, equipment position) into a unified overload monitoring system. The control unit integrates these diverse inputs to calculate the safety margin, achieving higher accuracy (within 20% of actual load-carrying capacity) while avoiding the need for complex individual measurement systems for each parameter.
Solution Approach 2:
The control unit acts as an intermediary that processes raw measurement data from pressure sensors, angle detectors, and position sensors. It performs payload calculations and safety margin determinations, converting simple measurements into accurate overload assessments without requiring direct complex measurement of the actual load-carrying capacity.
2Measurement precision
If angle detectors are installed on each equipment part to accurately determine position, then the measurement accuracy improves, but the time and cost of installation and configuration increases significantly
Solution Approach 1:
The control unit serves multiple functions: it monitors hydraulic pressure, processes angle detector signals, determines equipment position, performs payload calculations, and generates warning signals. This multi-functionality reduces the need for separate dedicated systems for each measurement task, thereby reducing installation time while maintaining accuracy.
Solution Approach 2:
The system performs pre-calculations of the safety margin based on current equipment configuration and stored reference values. This preliminary assessment allows for rapid overload determination without requiring time-consuming real-time analysis of all equipment parameters during operation.
3Adaptability or versatility
If the device configuration is unknown or changed, then the system can adapt to different configurations, but the overload warning means no longer operates correctly due to wrong conclusions about static stability
Solution Approach 1:
The control unit continuously monitors actual equipment position and compares it with the configuration data stored in memory. This feedback mechanism ensures that the payload calculations are based on the current actual configuration rather than outdated or incorrect configuration data, maintaining reliability even when configurations change.
Solution Approach 2:
The system dynamically adjusts the safety margin calculation based on real-time equipment position and configuration data. Rather than using fixed reference values, the control unit continuously updates the safety margin determination to reflect current operational conditions, ensuring accurate overload warnings regardless of configuration changes.
4Productivity
If the device is assumed to be standing on flat ground, then the calculation is simplified, but the warning signal is emitted too late when the device is on inclined ground due to reduced static moment
Solution Approach 1:
The control unit performs preliminary determination of the safety margin using current equipment position and load data before the critical overload condition occurs. This advance calculation allows the system to issue warning signals with sufficient lead time, even when the device is on inclined ground where the static moment is reduced and stability changes rapidly.
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 immediate and correct overload condition detection, ensuring operator warnings are timely and accurate, without requiring complex angle measurements or configuration adjustments, and maintaining accuracy across various positions and conditions.
Implementation Method 1
the hydraulic pressure in the lift cylinder is measured
Implementation Method 2
the supporting forces can be measured directly via force measuring pins or force measuring cells at the luffing jibs of the supporting means
Implementation Method 3
strain gauges should be mounted at the axles on a suitable point, and the wheel loads can then be determined from a deflection of the axles
Implementation Method 4
the static stability is determined according to a specified formula... the four contact forces on the generally four supporting points of the excavator are measured... the supporting or wheel loads of the excavator can be determined directly
Data Source
AI summary
The present disclosure relates to an overload warning means for excavators, preferably hydraulic excavators or material handling devices, with three or more contact points, the contact forces being determined at the contact points such that they are brought into an order descending by the amount thereof, so that F1>F2>F3 > . . . >Fn, and that the static stability is determined according to the following formula:S=∑i=3nFi∑i=1nFi≥Smin.