Excavator Grade Assist Synchronizing Stick and Boom
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Solution Overview
Problem
Construction machines, such as excavators, often dig below a desired grade due to unsynchronized movement of their parts, particularly because of delays in the hydraulic system, leading to unintended excavation below the specified grade.
Innovation Solution
A method and apparatus that sense user commands to delay and synchronize the movement of the stick and boom of an excavator, using a processor and algorithms to maintain the bucket above the desired grade by predicting the movement of the stick and boom based on sensors and user input, and actuating them hydraulically to prevent digging below the grade.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the stick is actuated immediately in response to user input, then the response time is fast, but the bucket digs below the desired grade due to hydraulic delay
Solution Approach 1:
The system performs preliminary action by predicting the future position of the bucket based on current stick movement commands and hydraulic delay characteristics. Before the actual digging occurs, the control system calculates the predicted bucket position and compares it with the desired grade, then preemptively adjusts the boom position to prevent grade violation. This anticipatory control resolves the contradiction by acting in advance rather than reactively.
Solution Approach 2:
Instead of controlling the stick directly in response to user input, the system inverts the control approach by using the predicted stick position to determine the required boom position. The boom is controlled based on the inverted relationship: boom position = f(predicted stick position, desired grade). This inversion allows the system to compensate for hydraulic delays by working backwards from the expected future state.
2Ease of operation
If the boom and stick move independently based on user input, then the operation is simple, but the movement is unsynchronized causing digging below grade
Solution Approach 1:
The system implements feedback by continuously monitoring the actual positions of the boom and stick, comparing them with the desired synchronized trajectory, and adjusting control signals accordingly. The feedback loop includes sensing hydraulic cylinder positions, calculating predicted future positions based on current movement rates, and generating corrective commands to maintain synchronization. This closed-loop feedback ensures precise coordination while maintaining simple operator input through automatic coordination algorithms.
3Manufacturing precision
If hydraulic delay is compensated by delaying stick actuation, then grade accuracy is maintained, but the response time increases
Solution Approach 1:
Rather than passively delaying stick actuation, the system performs preliminary calculation of the required delay duration based on hydraulic system characteristics and current operating conditions. The control system predicts how long the hydraulic delay will be and preemptively triggers the stick actuation at the optimal moment so that the bucket reaches the desired grade position exactly when needed. This active preliminary timing compensation maintains both grade accuracy and responsive operation.
Data Source
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AI summary
A method for machine grade assist includes determining whether user input will cause an implement of a machine to dig below a desired grade. User input to move a stick (104) of an excavator (100) can be blocked and/or delayed using hydraulic pressure so that movement of both the stick and the boom (102) of the excavator can be synchronized to prevent a bucket (106) of the excavator from digging below a desired grade (404) when the stick is moved.