Robot Laser Cladding Posture Control on Freeform Worn Surfaces
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Solution Overview
Problem
Existing methods for robotic laser cladding on freeform surfaces fail to accurately account for significant shape and topography changes in actual workpieces compared to design models, leading to posture jitter, mechanical shocks, and poor processing quality due to inadequate consideration of surface normal vectors and constant velocity interpolation.
Innovation Solution
A method involving reverse modeling, denoising, and sparsification to obtain normal vectors, followed by polynomial fitting and NURBS curve interpolation to generate smooth and synchronous motion trajectories, adaptive segmentation, and dynamic velocity control to ensure stable and high-precision laser cladding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the laser cladding nozzle is strictly maintained perpendicular to the surface to be machined, then the spot energy distribution is stable, but severe posture jitters occur due to micro-topography changes
Solution Approach 1:
The patent applies local quality by differentiating between macroscopic and microscopic surface characteristics. At the macro level, the nozzle maintains perpendicularity to achieve stable energy distribution. At the micro level, the system tolerates surface irregularities through filtering algorithms that distinguish between significant topography changes and minor roughness variations, preventing posture jitters while preserving spot energy stability.
Solution Approach 2:
The patent performs preliminary action by pre-calculating the ideal nozzle posture based on the macroscopic surface geometry before the actual cladding process. The system establishes a reference posture trajectory in advance, then uses filtering algorithms during execution to suppress deviations caused by micro-topography, rather than reacting to posture jitters in real-time.
2Device complexity
If a traditional constant-velocity interpolation control method is used, then the control is simple, but mechanical shocks occur in areas with excessive local curvature
Solution Approach 1:
The patent transforms the static constant-velocity control into a dynamic velocity control system. The velocity is adjusted in real-time based on the local curvature of the freeform surface, with higher velocities in low-curvature areas and reduced velocities in high-curvature areas. This dynamic adaptation prevents mechanical shocks while maintaining overall processing efficiency.
Solution Approach 2:
The patent changes the velocity parameter dynamically during the cladding process based on surface curvature characteristics. Instead of maintaining a fixed velocity, the system modulates the robot's movement speed according to the geometric properties of the workpiece, thereby avoiding mechanical shocks in high-curvature regions while keeping the control framework relatively simple.
3Ease of manufacture
If the standard design model is used as reference, then the trajectory planning is straightforward, but it cannot accurately guide the repair processing of the worn workpiece with significant shape changes
Solution Approach 1:
The patent segments the trajectory planning process into two distinct stages: macroscopic trajectory planning based on the standard design model, and microscopic posture adjustment based on actual surface measurement data. This segmentation allows the system to benefit from the simplicity of model-based planning while correcting for wear-induced deviations through measured surface data.
Solution Approach 2:
The patent introduces an intermediary element - the measured surface data of the worn workpiece - that bridges the gap between the standard design model and the actual workpiece geometry. This intermediary information is used to adjust and refine the trajectory, ensuring both ease of planning and accuracy in the repair process.
Data Source
AI summary
Provided is a robot posture optimization and follow-up control method and system for freeform surface repair. The system includes a worn surface reverse modeling module, a worn surface initial normal vector calculation module, an initial machining trajectory and normal vector extraction module, a normal vector rotation angle polynomial regression denoising module, a machining trajectory position and posture NURBS fitting module, a position and posture trajectory curvature adaptive segmentation module, a segmented trajectory position and posture synchronization acceleration and deceleration look-ahead module, and a robotic motion and laser process coordinated control module. The method and the system realize posture optimization and follow-up control in a cladding process of the robot, and ensures the processing quality of laser repair.