Compliant Motion Control for Robot Arm Assembly
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Solution Overview
Problem
Existing robot control systems face difficulties in performing compliant motion control effectively due to their inability to adjust stiffness based on variations in contact states between objects, requiring complex user instructions and limiting assembly work precision.
Innovation Solution
A robot system that adjusts parameter values of compliant motion control based on the relative position and orientation of objects, allowing for dynamic changes in stiffness to facilitate smoother assembly operations by calculating an index of movement difficulty and applying impedance control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If position control and force control are switched based on force sensor output magnitude, then control switching can be implemented, but the control system becomes complicated and cannot adapt stiffness to contact state variations
Solution Approach 1:
The patent implements dynamic switching between position control and force control based on real-time detection of contact state variations through force sensor output. The control mode is not fixed but dynamically adjusted according to the magnitude of force sensor signals, allowing the system to adapt stiffness to contact state variations while managing complexity through automated detection thresholds
Solution Approach 2:
The system continuously monitors force sensor output and uses this feedback to determine whether to switch between position control and force control modes. This closed-loop feedback mechanism enables automatic adaptation of control parameters based on actual contact conditions, resolving the contradiction between adaptability and complexity by using simple threshold-based decision logic
2Ease of operation
If control variable is determined before robot operation based on jog operation, then user instruction operation is simplified, but stiffness cannot be changed based on contact state variations during work
Solution Approach 1:
The system performs preliminary setup by determining control variables based on jog operation before actual work begins, which simplifies user instruction operation. This preliminary configuration establishes the initial control parameters and thresholds, allowing the system to operate automatically during work without requiring continuous user input
Solution Approach 2:
During work, the system continuously monitors force sensor output and automatically switches between control modes based on detected contact state variations. This real-time feedback mechanism enables stiffness adaptation during operation without requiring complex user instructions, as the system autonomously adjusts control parameters based on sensor feedback
3Manufacturing precision
If force control is used with predetermined switching values, then control implementation is straightforward, but assembly precision deteriorates due to inability to adapt to contact state variations
Solution Approach 1:
The patent implements dynamic adjustment of control parameters during assembly operations based on real-time detection of contact state variations. The system transitions from static, predetermined control parameters to dynamic parameters that adapt to changing contact conditions, thereby improving assembly precision without requiring overly complex manual adjustment mechanisms
Solution Approach 2:
The system uses force sensor feedback to automatically detect contact state variations and adjust control parameters accordingly. This automated feedback-based parameter adjustment improves assembly precision by adapting to actual contact conditions, while keeping the control system relatively simple through threshold-based decision logic rather than complex manual tuning
Data Source
AI summary
A robot includes an arm and a control unit configured to control a motion of the arm using compliant motion control. The control unit changes a parameter value of the compliant motion control depending on a relative position and orientation of a first object moving along with the arm and a second object.