Robot Arm Teaching Control With Position-Force Phase Switching
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Solution Overview
Problem
Current methods for teaching robot arm operations, such as direct teaching, do not ensure precise operation during precision tasks like assembly, as they generate force teaching data related to contact force, leading to inaccuracies in robot arm performance.
Innovation Solution
A controller system with sensors to acquire and analyze first and second force data, along with position and orientation data, to generate teaching data for both position and force control periods, enabling precise control of the robot arm during teaching and regeneration of operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If force teaching data related to contact force is generated during direct teaching, then the robot arm can be operated intuitively by manually guiding, but the operation precision deteriorates during precision tasks like assembly
Solution Approach 1:
The teaching data is segmented into multiple periods: a first period containing position and orientation data for general movement, and a second period containing force data for contact operations. This segmentation allows the system to switch between position control (for precision) and force control (for intuitive contact operations) based on the task phase, thereby resolving the contradiction between intuitive operation and operation precision
2Ease of operation
If compliance control or impedance control is used during direct teaching, then the teacher can manually manipulate the robot arm easily, but the robot arm does not necessarily operate as instructed at parts requiring precision works
Solution Approach 1:
The control mode is made dynamic by switching between position control and force control based on the operational phase. During the first period (approach and positioning), position control ensures high accuracy. During the second period (contact and assembly), force control enables intuitive manual manipulation. This dynamic switching resolves the contradiction between ease of manual manipulation and operation accuracy
3Manufacturing precision
If position and orientation data is used for control, then the robot arm can be positioned accurately, but force-related operations during assembly cannot be precisely controlled
Solution Approach 1:
The teaching data structure is designed to be multi-functional by incorporating both position/orientation data (first data) and force data (second data) within the same teaching data set. This allows the robot arm to utilize position control for accurate positioning while simultaneously enabling force control for assembly operations, thereby achieving both positioning accuracy and force control capability through a unified teaching approach
Data Source
AI summary
A robot includes a handling portion handled in teaching an operation of a robot arm, a first sensor acquiring data of a first force acting on a tip of the robot arm, a second sensor acquiring data of a second force acting on the handling portion and a third sensor acquiring data of position and orientation of the tip of the robot arm. A controller of the robot is configured to generate teaching data having a first period and a second period based on analytical results of the first and second force data at a time of teaching the robot arm. The robot arm is controlled by position and orientation control based on the position and orientation data of the third sensor in the first period. The robot arm is controlled by force control based on the first and second force data in the second period.