Robot Joint Control Switching for Precision and Compliance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing robot arms with encoders only at the output shaft of speed reducers lack mechanical compliance, leading to difficulties in assembly tasks due to high accuracy but low flexibility, and those with encoders at both input and output shafts have minimal mechanical compliance, making precise positioning challenging.
Innovation Solution
A robot apparatus with a control unit that switches between output-based control mode for high accuracy at the working start position and input-based control mode for mechanical compliance during operation, using both input and output angle detection values from encoders to manage joint angles effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an encoder is provided at the output shaft of the speed reducer to reduce position error, then manufacturing precision is improved, but mechanical compliance deteriorates
Solution Approach 1:
The control method dynamically switches between output-based control mode (for high precision positioning at working start position) and input-based control mode (for mechanical compliance during assembly tasks). This dynamic switching allows the system to adapt its control characteristics based on the operational phase, resolving the contradiction between precision and compliance
Solution Approach 2:
The invention changes the control parameter from fixed (either output-based or input-based) to variable by switching between two control modes. During positioning phase, output-based control provides high precision; during assembly phase, input-based control provides mechanical compliance. This parameter change enables the system to achieve both high precision and mechanical compliance at different times
2Manufacturing precision
If feedback control is performed based on output shaft encoder to enhance positioning accuracy, then manufacturing precision is improved, but ease of operation deteriorates
Solution Approach 1:
The control system dynamically adjusts its behavior by switching between output-based control mode for high-precision positioning and input-based control mode for ease of operation during assembly. This dynamic adaptation allows the robot to be highly accurate when needed and compliant/easy to operate when performing assembly tasks
Solution Approach 2:
The control parameter switches between output-based feedback (for precision) and input-based feedback (for ease of operation). During positioning, output-based control ensures accuracy; during assembly operations, input-based control provides mechanical compliance that makes operation easier and more forgiving
Data Source
AI summary
A joint driving unit driving a joint of a robot arm includes a motor, a speed reducer transmitting rotation of the motor in a variable speed, an input side encoder detecting a rotation angle of a rotation shaft of the motor, and an output side encoder detecting a rotation angle of an output shaft of the speed reducer. When positioning the end effector at a working start position at which predetermined work is started, operation of the robot is set to an output based control mode in which an angle of a joint is feedback controlled based on an angle detection value from the output side encoder. When the robot performs the predetermined work, the operation of the robot is changed to an input based control mode in which the angle of the joint is feedback controlled based on an angle detection value from the input side encoder.