Robot Grinding Trajectory Control with Elasticity Feedback
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Solution Overview
Problem
Existing robot systems face challenges in processing objects into desired shapes without applying excessive force, as they typically rely on force control that can lead to unwanted action on tools and workpieces, limiting the ability to shape objects unrelated to their surface.
Innovation Solution
A robot system with a controller that generates a target trajectory for the tool and executes position control, along with elasticity control to deviate from the trajectory based on reactive forces, ensuring the tool moves according to the pressing force and distance from the target trajectory, preventing excessive force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If force control is executed to press the tool against the workpiece with predetermined force, then action of excessive force is prevented, but the tool traces a trajectory substantially in accordance with the surface of the workpiece making it difficult to process the workpiece into a shape unrelated to the surface
Solution Approach 1:
The patent applies dynamics by making the control system adaptable during operation. The controller dynamically switches between position control and force control based on real-time conditions: position control is used when the tool is far from the workpiece surface to maintain trajectory accuracy, while force control is activated when the tool approaches the surface to prevent excessive force. This dynamic switching resolves the contradiction between preventing excessive force and maintaining shape accuracy.
Solution Approach 2:
The patent changes control parameters based on the tool's position relative to the workpiece. The control mode parameter is changed from position control to force control when the tool approaches the surface, and the pressing force parameter is adjusted based on the distance from the target trajectory. This parameter change allows the system to maintain trajectory accuracy during approach while preventing excessive force during contact.
2Manufacturing precision
If the tool traces a trajectory substantially in accordance with the surface of the workpiece, then the tool follows the surface contours, but it is difficult to process the workpiece into a shape unrelated to the surface
Solution Approach 1:
The system dynamically adjusts the control mode based on the processing stage. During the approach phase, position control maintains high trajectory accuracy. During the processing phase, force control allows the tool to deviate from the target trajectory to create shapes unrelated to the original surface, thereby achieving both trajectory accuracy when needed and shape versatility when required.
Solution Approach 2:
The control system periodically switches between position control and force control modes based on the tool's proximity to the workpiece surface. This periodic switching enables the system to maintain trajectory accuracy during approach movements while allowing shape variation during processing, thus resolving the contradiction between trajectory fidelity and shape adaptability.
3Manufacturing precision
If position control is executed to move the robot along a target trajectory, then the tool follows the desired path, but the pressing force on the object may become excessive when deviating from the trajectory
Solution Approach 1:
The system uses feedback from the force sensor to monitor the pressing force between the tool and workpiece. When the tool deviates from the target trajectory during processing, the feedback mechanism detects the increased force and triggers a switch to force control mode, which limits the pressing force to predetermined levels. This feedback-based control switching resolves the contradiction between maintaining trajectory and preventing excessive force.
Solution Approach 2:
The controller acts as an intermediary that mediates between position control commands and force control constraints. When the tool approaches the workpiece surface and force increases, the controller intervenes to switch control modes, preventing excessive force while allowing trajectory following during approach. This intermediary control resolves the contradiction by coordinating both position and force requirements.
Data Source
AI summary
A robot system 100 includes a robot 1 that removes a processing portion B of an object W by a griding device 11a and a controller 3 that controls the robot 1. The controller 3 has a trajectory generator 610 that generates a target trajectory of the griding device 11a tracing the processing portion B and a movement commander 60 that executes position control for moving the robot 1 such that the griding device 11a moves along the target trajectory while executing elasticity control for moving the robot 1 such that the griding device 11a moves so as to deviate from the target trajectory according to reactive force from the object W and the pressing force of the griding device 11a on the object W increases according to the distance from the target trajectory.