Robot Direct Teaching Control With Axis Switching and Inverse Kinematics
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Solution Overview
Problem
Conventional direct teaching methods for robots face challenges in simplifying the adjustment of arm tip position and posture, often requiring difficult operations and leading to unstable movements like vibration, and incur increased manufacturing costs due to the use of sensors.
Innovation Solution
A robot control apparatus that employs an angle control section and axis setting section to perform inverse kinematics calculations, allowing users to change the arm tip position or posture by setting operation and control axes, thereby simplifying the adjustment process without the need for sensors like force or torque sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If force sensors or torque sensors are mounted to the robot to enable force control during direct teaching, then the user can apply force to change position or posture, but the manufacturing cost increases and the robot performance deteriorates due to increased weight
Solution Approach 1:
The patent extracts the force sensing function from physical sensors and implements it through computational methods. The control device calculates equivalent forces based on motor current values and applies virtual force feedback through the existing control system, eliminating the need for additional force or torque sensors while maintaining the ability to sense and respond to user-applied forces during direct teaching
Solution Approach 2:
The patent replaces the mechanical sensor-based force detection system with a computational model that uses electrical current measurements and inverse dynamics calculations to estimate applied forces. This substitution eliminates physical sensors while preserving the force control capability needed for intuitive direct teaching operation
2Ease of operation
If force control is implemented using force sensors, then position and posture can be adjusted by user force, but vibration occurs in robot motion depending on posture or force application method
Solution Approach 1:
The patent implements a feedback control mechanism where the control device continuously calculates equivalent forces from motor current values, compares them with desired force targets, and adjusts control commands to minimize deviations. This feedback loop suppresses vibrations by actively compensating for unstable motions that occur during direct teaching operations
Solution Approach 2:
The patent dynamically adjusts control parameters including equivalent force values, control gains, and damping coefficients based on robot posture and operational conditions. By changing these parameters adaptively, the system maintains stable motion across different postures and force application methods while preserving intuitive operability
3Ease of operation
If force sensors are added to enable intuitive direct teaching, then simplified teaching can be achieved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the force sensing capability from expensive physical sensors and implements it through computational algorithms using existing sensor data (motor currents). This approach eliminates the need for additional force or torque sensors, significantly reducing manufacturing costs while maintaining the simplified teaching functionality
Solution Approach 2:
The patent creates a virtual model of force interaction that replicates the behavior of physical force sensors. By calculating equivalent forces through inverse dynamics and current measurements, the system produces the same control effects as physical sensors would, without the associated manufacturing costs
Data Source
AI summary
There is provided a robot control apparatus that controls a vertical articulated robot and is suitable for direct teaching. In the apparatus, an axis setting section sets operation axes and control axes from among the axes subjected to angle control, when performing the direct teaching of changing a position of the arm tip, while retaining a posture thereof at a target posture. The operation axes can be dominant factors when determining the position of the arm tip and are allowed to freely move according to an external force, and the control axes can be dominant factors when determining the posture of the arm tip and are controlled by an angle control section. When performing the direct teaching, the angle control section receives an input of current angles of the operation axes and the target posture to calculate command angles of the respective control axes according to inverse kinematics calculation.