Construction Machine Work Implement Velocity Control
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Solution Overview
Problem
Existing control systems for construction machines, such as those described in Japanese Laid-open Patent Publication No. H4-136324, impose limits on all shafts of the work implement, leading to operator discomfort during excavation due to the strong feeling of intended operations, as they stop the bucket when it reaches the boundary line, causing discomfort and limiting the operator's control.
Innovation Solution
A control system for a construction machine with a work implement comprising a boom, arm, and bucket, featuring a design plane setting unit, target velocity determining unit, distance obtaining unit, limit velocity determining unit, and control unit that adjusts the boom and arm velocities based on the distance from the design plane and operator inputs, allowing only boom limitation when the bucket is outside the plane and both boom and arm limitations when closer, to prevent entry while minimizing operator discomfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If limits are applied to all shafts of the work implement to prevent bucket entry into design plane, then the bucket entry prevention is improved, but the operator comfort deteriorates due to strong sensation of operation limitation
Solution Approach 1:
The patent applies different control strategies to different parts of the work implement based on their functional characteristics. The boom, which has strong operational intent and causes significant operator discomfort when limited, is excluded from velocity limitation. The arm and bucket, which are closer to the boundary and require precise control, are subject to velocity limitation. This localized differentiation resolves the contradiction by applying limits only where necessary while preserving operator comfort on the boom.
Solution Approach 2:
The control system segments the work implement into three distinct parts (boom, arm, bucket) and applies independent velocity limitation logic to each segment. The boom velocity limitation is determined separately from arm and bucket velocity limitations, allowing the system to prevent bucket entry into the design plane while maintaining smooth boom operation and reducing operator discomfort.
2Reliability
If limits are applied to the arm to prevent bucket entry, then the bucket entry prevention is improved, but the operator comfort deteriorates due to strong sensation of operation limitation during excavation
Solution Approach 1:
The patent applies velocity limitation selectively to the arm and bucket while excluding the boom from limitation. This local differentiation is based on the functional characteristics of each component: the boom requires free operation to maintain operator comfort, while the arm and bucket need velocity control to prevent boundary violation. This resolves the contradiction by applying limits only to the arm and bucket where they are most effective.
3Reliability
If the bucket is stopped at the boundary line to prevent entry, then the design plane protection is improved, but the operation smoothness deteriorates causing operator discomfort
Solution Approach 1:
The patent implements dynamic velocity limitation where the velocity limit values are adjusted in real-time based on the distance from the design plane and the current operation state. Instead of a fixed stop at the boundary, the system dynamically reduces velocity as the bucket approaches the boundary, preventing entry while maintaining operation smoothness and reducing abrupt stops that cause operator discomfort.
Solution Approach 2:
The control system applies velocity limitation in advance before the bucket reaches the boundary line. By monitoring the distance from the design plane and applying progressive velocity reduction, the system prevents boundary violation while avoiding sudden stops. This preliminary action maintains operation smoothness and reduces operator discomfort compared to stopping exactly at the boundary.
Data Source
AI summary
A construction machine has a work implement and a work implement operating device. The work implement has a boom, arm, and bucket. A limit velocity determining unit determines a limit velocity of the boom from the limit velocity of the entire work implement, the arm target velocity, and the bucket target velocity. The distance when the blade tip of the bucket is positioned outside of the design plane is a positive value and the velocity in a direction from inside of the design plane toward outside of the design plane is a positive value. The first limit condition includes a condition that the limit velocity of the boom is greater than the boom target velocity. When the first limit condition is satisfied, a work implement control unit controls the boom to match the limit velocity of the boom and controls the arm to match the arm target velocity.