Robot Arm Workpiece Selection for Shorter Pick-and-Place Cycles
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Solution Overview
Problem
Conventional robot arm control systems in production systems face challenges in efficiently performing pick and place tasks due to long moving distances, which can exceed assumed cycle times, potentially leading to missed workpieces.
Innovation Solution
A robot arm control device that selects a target workpiece based on its proximity to the robot arm's distal end position at the task-start timing, prioritizing workpieces upstream in the flow direction to minimize moving distance and prevent missed picks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot arm selects workpieces located downstream to ensure reliable picking, then the reliability of workpiece pickup is improved, but the moving distance of the robot arm increases causing the task time to exceed the assumed cycle time
Solution Approach 1:
The workpiece selection criterion is made dynamic by considering the robot arm's distal end position at the task-start timing. The system dynamically adjusts which workpieces are eligible for selection based on their relative position to the moving robot arm, allowing flexible adaptation to different operational states while maintaining both reliability and timing constraints.
Solution Approach 2:
The system performs preliminary selection of candidate workpieces based on their position upstream of the robot arm's distal end before the actual pickup action. By pre-identifying valid candidates that satisfy the positional constraint, the system ensures that the subsequent pickup operation can be executed reliably within the cycle time without requiring last-minute adjustments.
2Productivity
If the robot arm picks workpieces from upstream positions to reduce moving distance, then the productivity is improved, but the risk of missing workpieces increases
Solution Approach 1:
The selection criteria dynamically adapt to the robot arm's real-time position and motion state. By continuously updating the set of candidate workpieces based on the distal end position at task-start timing, the system optimizes the balance between minimizing travel distance and ensuring reliable pickup, allowing the robot to achieve high productivity without sacrificing reliability.
3Adaptability or versatility
If the robot arm travels longer distances to reach downstream workpieces, then the selection flexibility is improved, but the cycle time is exceeded leading to missed workpieces
Solution Approach 1:
The system applies different selection criteria to different spatial zones relative to the robot arm. Workpieces upstream of the distal end position are eligible for selection, while those downstream are excluded. This local differentiation in selection policy allows the system to maintain flexibility within the feasible region while automatically respecting the time constraint.
Solution Approach 2:
The system preliminarily filters the workpiece candidates based on their position relative to the robot arm's distal end before execution. By pre-establishing the set of valid candidates that can be reached within the cycle time, the system maintains selection flexibility among eligible workpieces while guaranteeing that the task will complete within the assumed cycle time.
Data Source
AI summary
A robot arm control device according to the present disclosure comprises a workpiece selecting section that selects a target workpiece, which is a workpiece to be picked up and placed, among a plurality of workpieces conveyed by a conveyor system in a predetermined flow direction; and a motion control section that controls a motion of the robot arm to pick up the target workpiece at a predetermined pick up position and place the target workpiece at the target placement position selected among a plurality of predetermined placement positions, wherein the workpiece selecting section selects, among the workpieces that are candidates for selection, the workpiece that has a shortest distance from the distal end position at a task-start timing to the workpiece position at the task-start timing as the target workpiece.