Robot End Effector Force Control Within Assembly Operation Ranges
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Solution Overview
Problem
Existing robot assembly systems face inefficiencies and increased faulty assemblies due to external perturbations causing inappropriate recognition of reaction forces, leading to incorrect determination of assembly completion and release of held parts.
Innovation Solution
A robot apparatus with a robot arm and end effector, equipped with a position detection unit and a control unit that includes a force control unit, operates within a predetermined operation range to differentiate between intended assembly forces and external perturbations, ensuring accurate assembly completion by switching between position and force control modes as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If force control is used to detect assembly completion, then assembly automation is improved, but external perturbations cause inappropriate reaction force recognition leading to faulty assembly
Solution Approach 1:
The system dynamically switches between position control mode and force control mode based on the robot arm's location. Position control is used when approaching the operation range to avoid premature contact, while force control is activated within the operation range for precise assembly detection. This dynamic mode switching resolves the contradiction by applying the appropriate control strategy at each stage of the assembly process.
Solution Approach 2:
The control unit changes the control parameter from position-based control to force-based control when the robot arm enters the predetermined operation range. This parameter change allows the system to maintain stability during approach while enabling sensitive detection of assembly completion forces within the operational zone, thereby improving both automation and reliability.
2Adaptability or versatility
If the robot arm operates freely without position constraints, then operation flexibility is improved, but contact with unintended objects increases causing defective assembly
Solution Approach 1:
The operational space is segmented into two distinct zones: an approach zone governed by position control and an operation zone governed by force control. The position detection unit monitors the robot arm's location and determines when to switch between control modes. This spatial segmentation allows flexible approach paths while constraining the robot within safe boundaries during the assembly operation.
Solution Approach 2:
The position detection unit acts as an intermediary that monitors the robot arm's position and triggers the control mode switch. This intermediary mechanism ensures that force control is only activated when the robot is at the appropriate position, preventing contact with unintended objects while maintaining operational flexibility through proper sequencing.
3Stability of the object's composition
If position control is used during approach, then stability is improved, but assembly completion detection accuracy deteriorates
Solution Approach 1:
The control system dynamically transitions from position control to force control when the robot arm enters the predetermined operation range. This dynamic switching allows the system to maintain stability during the approach phase while enabling precise detection of assembly completion forces during the operational phase, resolving the contradiction between stability and detection accuracy.
Solution Approach 2:
Position control is used in advance during the approach phase to stabilize the robot arm before assembly contact. Once the robot reaches the predetermined operation range, the system switches to force control for precise assembly completion detection. This preliminary positioning action ensures stability is established before the precision measurement phase begins.
Data Source
AI summary
A robot apparatus includes a robot arm having an end effector. The robot apparatus includes a position detection unit configured to detect a position of the end effector, and a control unit configured to control the robot apparatus, wherein the control unit includes a force control unit configured to control the end effector by force control, and information about a plurality of operation ranges in which the end effector operates by the force control, the plurality of operation ranges being set for the plurality of contact works, wherein the control unit controls the end effector using the position detection unit and the force control unit such that one of the plurality of contact works is performed within one of the plurality of operation ranges corresponding to the one of the plurality of contact works.