Robot Arm Free-Drive via Tool Flange Force-Torque Sensing
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Solution Overview
Problem
Existing robot arm systems in free-drive mode require users to manipulate individual joints to change posture, which can be difficult, especially when parts of the arm are obstructed, and existing teaching methods are complex and limited in flexibility.
Innovation Solution
The robot arm system controls motor torques based on a static motor torque to maintain posture and an additional motor torque derived from a force-torque sensor integrated into the tool flange, allowing users to change posture by pushing, pulling, or rotating the tool flange without manual manipulation of each joint, and enabling flexibility in posture adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If users manipulate individual robot joints to change posture in free-drive mode, then the robot arm can be positioned, but the operation becomes difficult when parts of the arm are obstructed
Solution Approach 1:
The force-torque sensor integrated into the tool flange enables the robot to respond to forces applied at the end effector, allowing posture changes through tool flange manipulation rather than requiring direct joint manipulation. This multi-functional approach lets the same sensor support both precision control and intuitive manual positioning.
Solution Approach 2:
The force-torque sensor acts as an intermediary between the user's manual forces applied to the tool flange and the robot's joint motors. The sensor detects these forces and translates them into appropriate motor torque commands, mediating the interaction between human operator and robot mechanism.
2Ease of operation
If a force-torque sensor is integrated into the tool flange to detect forces, then posture can be changed by pushing or pulling the tool flange, but the device complexity increases
Solution Approach 1:
The force-torque sensor is merged with the existing tool flange structure, combining the sensing function with the mechanical interface. This integration approach eliminates the need for separate sensor mounting hardware and reduces the overall system complexity compared to adding a standalone sensor system.
Solution Approach 2:
The integrated force-torque sensor serves multiple functions: detecting forces for posture control, providing feedback for collision detection, and enabling both free-drive and precision control modes. This multi-functionality justifies the added complexity by eliminating the need for separate systems.
3Productivity
If existing teaching methods are used to program robot movements, then the robot can be instructed to perform tasks, but the teaching process becomes complex and time-consuming
Solution Approach 1:
The robot system performs self-teaching by detecting forces applied during free-drive operation and automatically recording the relationship between tool flange positions and required motor torques. This eliminates the need for complex external teaching apparatus and reduces programming time significantly.
Solution Approach 2:
The force-torque sensor provides real-time feedback during free-drive operation, allowing the system to automatically learn and store the force-torque characteristics for different postures. This feedback mechanism enables intuitive teaching without complex programming procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances user flexibility in changing the robot arm's posture in free-drive mode by allowing movement of the tool flange without joint manipulation and simplifies the process by eliminating the need for complex teaching apparatus configurations.
Implementation Method 1
The robot tool flange comprises a force-torque sensor integrated into the robot tool flange, where the force-torque sensor provides a signal indicating a force-torque provided to the tool flange
Implementation Method 2
each of said robot joints comprises an output flange rotatable in relation to said robot joint and a joint motor configured to rotate said output flange
Implementation Method 3
obtaining a static motor torque based on an actual posture of the robot arm and based on a dynamic model of the robot arm, where the static motor torque indicates a motor torque that the joint motors need to provide in order to keep the robot arm in a static posture
Data Source
AI summary
Method and robot arm, where the motor torques of the joint motors of a robot arm are controlled based on a static motor torque indicating the motor torque needed to maintain the robot arm in a static posture, where the static motor torque is adjusted in response to a change in posture of the robot arm caused by an external force different from gravity applied to the robot arm. Further the motor torque of the joint motors is controlled based on an additional motor torque obtained based on a force-torque provided to the robot tool flange, where the force-torque is obtained by a force-torque sensor integrated in the tool flange of the robot arm.