Robot Arm Control via Force Detection for Direct Teaching
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Solution Overview
Problem
Existing robot teaching methods face difficulties in moving the arm's joints while maintaining the hand tip's position and attitude, making it challenging to teach desired actions effectively.
Innovation Solution
A robot system with a force detector that changes the arm's position based on output values from the detector, allowing the arm to move from a first to a second position while the end effector remains in a specific position, and stores these positions in memory for direct teaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct teaching method is used to move the arm's joint, then the hand tip position and attitude can be maintained fixed, but it is difficult to teach desired actions effectively
Solution Approach 1:
The patent implements dynamic control mode switching that allows the system to transition between position control mode (for precision) and force control mode (for ease of operation). In position control mode, the hand tip position and attitude are maintained fixed with high precision. In force control mode, the operator can easily apply forces to teach desired actions without worrying about position drift. This dynamic switching resolves the contradiction by allowing both precision and ease of operation at different stages of the teaching process.
Solution Approach 2:
The patent changes the control parameter from position to force by switching control modes. When in force control mode, the system accepts force inputs from the operator and translates them into arm movements while maintaining hand tip position through compensation calculations. This parameter change allows the operator to intuitively teach actions by applying forces rather than precisely positioning the hand, thereby improving ease of operation while maintaining position precision through the control system.
2Ease of operation
If indirect teaching method is used, then the arm joint can be moved freely, but the hand tip position and attitude cannot be kept fixed
Solution Approach 1:
The patent introduces a control system as an intermediary that mediates between the operator's force inputs and the arm's movements. The control system calculates the relationship between arm joint movements and hand tip position, and actively compensates to maintain hand tip stability. This intermediary control layer allows the operator to move the arm joint freely through force application while the system ensures the hand tip remains at the desired position, thus resolving the contradiction between movement freedom and position stability.
3Measurement precision
If force detector is used to change arm position, then direct teaching accuracy improves, but system complexity increases
Solution Approach 1:
The patent makes the force detector serve multiple functions: it detects forces for direct teaching, provides feedback for control mode switching, and enables both position and force control modes. This multi-functionality reduces the need for separate components for each function, thereby limiting the increase in system complexity while achieving improved action memorization accuracy through force-based direct teaching.
Data Source
AI summary
A robot system includes an arm with a plurality of joints, the arm being configured to assume a first position and a second position, an end effector attached to the arm, the end effector having a specific position, and a force detector configured to detect a force or a torque applied to or generated by the arm or the end effector, and a robot control apparatus configured to receive an output value from the force detector to change the arm from the first position to the second position while the end effector remains in the specific position, and store the second position of the arm in a memory so as to relate the second position of the arm with the specific position of the end effector.