Asymmetric Impedance Control for Robot Insertion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing impedance control methods in robots lack the ability to perform asymmetric displacement changes with respect to the external force direction, which is necessary for mimicking human-like operations such as inserting objects into devices with pull-in mechanisms.
Innovation Solution
A robot controller system that performs impedance control by switching between different sets of control parameters based on the detected external force direction, allowing for asymmetric displacement changes by using a force control unit that determines the external force direction and selects appropriate control parameters to output correction values for feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If symmetric impedance control is used, then the control system is simple and stable, but the robot cannot perform asymmetric displacement changes with respect to external force direction
Solution Approach 1:
The patent applies dynamics by making the impedance parameters dynamic rather than static. The control system switches between different impedance parameter sets based on the direction of external force, allowing the robot to exhibit different mechanical characteristics (stiffness, damping, mass) depending on whether the force is applied in the positive or negative direction. This dynamic adaptation enables asymmetric displacement behavior while maintaining system stability through controlled parameter transitions.
Solution Approach 2:
The patent directly implements parameter changes by modifying impedance parameters (mass, damping, stiffness) based on external force direction. When force is detected in a specific direction, the system selects corresponding parameter sets that produce the desired asymmetric response. This approach allows the robot to mimic human-like operations where displacement varies asymmetrically with respect to force direction, resolving the contradiction between adaptability and complexity.
2Adaptability or versatility
If asymmetric impedance control is implemented, then the robot can mimic human operations, but the control system becomes more complex
Solution Approach 1:
The patent directly applies asymmetry by implementing different impedance characteristics for opposite force directions. The control system maintains symmetric structure in the base impedance model but introduces asymmetric behavior through direction-dependent parameter selection. This allows the robot to perform human-like operations (such as inserting objects into devices with pull-in mechanisms) where the displacement response to force is intentionally asymmetric, while keeping the underlying control framework relatively simple.
3Adaptability or versatility
If direction-dependent force control is used, then asymmetric displacement is achieved, but the computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the force control space into distinct directional segments. Instead of using a single complex continuous function to determine impedance parameters, the system segments the control space based on force direction and assigns appropriate parameter sets to each segment. This segmentation approach simplifies computation by avoiding complex real-time calculations while still achieving accurate asymmetric displacement control through discrete parameter selection based on detected force direction.
Data Source
AI summary
A robot controller includes a force control unit that outputs a correction value of a target track of a robot based on a detected sensor value acquired from a force sensor, a target value output unit that obtains a target value by performing correction processing on the target track based on the correction value and outputs the obtained target value, and a robot control unit that performs feedback control of the robot based on the target value. Further, the force control unit performs first force control when an external force direction indicated by the detected sensor value is a first direction, and performs second force control different from the first force control when the external force direction is a second direction opposite to the first direction.