Digital Twin Alignment for Force-Controlled Robotic Sanding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current automated finishing systems face challenges in achieving high dimensional accuracy and correcting defects in virtual models of workpieces, particularly due to low-resolution optical data and varying compliance characteristics, which can lead to inconsistent material removal and surface finish.
Innovation Solution
The system autonomously captures sparse scan data, generates a virtual model, and adjusts the sanding head's toolpath based on real-time force and position feedback to maintain target forces and correct the model's accuracy, using a robotic arm with integrated sensors and actuators to navigate and process the workpiece while transforming the virtual model to align with actual surface measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sparse optical scan data is used to generate a virtual model, then the scanning speed and productivity are improved, but the measurement precision and manufacturing precision deteriorate due to low resolution
Solution Approach 1:
The patent merges sparse optical scan data with dense tactile sensor data from the sanding head to create a hybrid digital twin. The optical scanner captures overall geometry quickly while the tactile sensor fills in high-frequency surface details, combining the speed advantages of optical scanning with the precision of tactile measurement.
Solution Approach 2:
The tactile sensor acts as an intermediary that bridges the resolution gap between sparse optical data and the actual workpiece surface. It provides real-time contact measurements that correct and enhance the low-resolution optical model during the sanding process.
2Device complexity
If the sanding head follows a fixed toolpath, then the device complexity is reduced, but the manufacturing precision deteriorates due to workpiece compliance variations
Solution Approach 1:
The patent implements dynamic toolpath adjustment where the sanding head deviates from the nominal toolpath in real-time based on tactile force feedback. The control system continuously adapts the toolpath to compensate for workpiece compliance variations, maintaining consistent contact force and material removal rate.
Solution Approach 2:
The tactile sensor provides real-time force feedback during sanding, which is fed back to the control system to dynamically adjust the sanding head position and maintain target contact forces despite variations in workpiece stiffness and geometry.
3Manufacturing precision
If real-time force feedback and toolpath deviation are implemented, then the manufacturing precision is improved, but the device complexity and computational load increase
Solution Approach 1:
The sanding head is designed with multi-functionality, integrating both sanding operations and tactile sensing capabilities in a single tool. This eliminates the need for separate measurement and processing equipment, reducing overall system complexity while enabling real-time feedback control.
Solution Approach 2:
The system uses the sanding head itself as the measurement probe, where the same tool that removes material also senses contact forces and surface geometry. This self-service approach eliminates dedicated measurement equipment and simplifies the system architecture.
4Measurement precision
If the virtual model is updated continuously with processing data, then the measurement precision is improved, but the loss of time due to data processing increases
Solution Approach 1:
The patent performs preliminary registration and alignment of the digital twin with the physical workpiece before the sanding process begins. This pre-alignment establishes a coordinate framework that enables efficient real-time updates during sanding without requiring extensive computational transformation at each step.
Solution Approach 2:
The digital twin is updated continuously during the sanding process rather than in discrete batches. The tactile sensor data streams continuously to update the model, maintaining current accuracy without interrupting the sanding operation for data processing cycles.
Data Source
AI summary
A method includes: compiling images, captured by an end effector traversing a scan path over a workpiece, into a virtual model of the workpiece; generating a toolpath based on a geometry of the workpiece represented in the virtual model; and assigning a target force to the workpiece. The method also includes, during a processing cycle: navigating a sanding head, arranged on the end effector, across the workpiece according to the toolpath; based on force values output by a force sensor coupled to the sanding head, deviating the sanding head from the toolpath to maintain forces of the sanding head on the workpiece proximal the target force; and tracking a sequence of positions of a reference point on the sanding head, traversing the workpiece, in contact with the workpiece. The method also includes transforming the virtual model into alignment with the sequence of positions of the reference point.