Excavator Load Weight Calculation Using Multi-Pin Equilibrium
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Solution Overview
Problem
Existing methods for calculating the weight of a load conveyed by a work implement, such as a bucket in a hydraulic excavator, are inaccurate due to the variable position of the load's center of gravity, which complicates precise weight determination.
Innovation Solution
A computing device and method that utilize multiple equilibrium equations and sensor data from hydraulic cylinders and position sensors to calculate load weight by establishing relational expressions based on the motion and positions of the boom, arm, and attachment components of the work implement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the position of the center of gravity of the load in the bucket is determined experimentally, then the calculation method is simple, but the accuracy of the load weight calculation deteriorates because the position is not necessarily constant
Solution Approach 1:
The invention transitions from a static experimental center of gravity position to a dynamic calculation approach. The center of gravity position is no longer fixed but is calculated in real-time based on the actual load distribution in the bucket, which varies with the load shape and density. This dynamic approach resolves the contradiction by maintaining calculation simplicity while improving accuracy through real-time adaptation to varying load conditions.
Solution Approach 2:
The invention changes the parameter approach by introducing multiple variables into the calculation: the position of the center of gravity of the load in the bucket is no longer a single fixed value but is expressed as a function of multiple parameters including the position of the center of gravity of the bucket itself, the weight of the load, and the geometric dimensions of the bucket. This parameter transformation allows the system to account for varying load conditions while maintaining a systematic calculation framework.
2Measurement precision
If multiple equilibrium equations are used to calculate load weight, then accuracy is improved, but the complexity of the calculation system increases
Solution Approach 1:
The invention segments the complex equilibrium calculation into distinct components: the moment equilibrium equation around the boom support shaft is separated into manageable terms, including the weight of the boom, the weight of the attachment, the weight of the load, and their respective center of gravity positions. This segmentation allows the complex system to be solved through systematic substitution and calculation of individual components rather than attempting to solve one large complex equation.
Solution Approach 2:
The invention introduces intermediate calculation steps and auxiliary variables as mediators. The center of gravity position of the load in the bucket is calculated as an intermediate value using the moment equilibrium equation, which then serves as an input for the final load weight calculation. This intermediary approach breaks down the complex problem into sequential manageable steps, reducing overall system complexity.
Data Source
AI summary
A hydraulic excavator includes a vehicular body, a boom bottom pin supported by the vehicular body, a boom rotatably coupled to the vehicular body by the boom bottom pin, a boom top pin attached to a tip end of the boom, an arm rotatably coupled to the boom by the boom top pin, an arm top pin attached to a tip end of the arm, and a bucket rotatably coupled to the arm by the arm top pin. The computing device calculates a weight of a load conveyed by a work implement based on any two equilibrium equations of an equation of moment equilibrium around the boom bottom pin, an equation of moment equilibrium around the boom top pin, and an equation of moment equilibrium around the arm top pin.