Robot Arm Free-Drive With 3D Boundary and Safe Force Activation
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Solution Overview
Problem
Existing robot arms in free-drive mode require manipulation of individual joints, which can be difficult, especially in confined spaces or when parts of the robot arm are obstructed. Additionally, there are challenges with accurately specifying payload weight, leading to potential hazardous situations.
Innovation Solution
A robot controller that allows switching to a free-drive mode where the robot arm can be maintained in a static posture under gravity and changed postures with an external force. The controller initiates a free-drive activation sequence by monitoring joint sensor parameters and comparing them to threshold values, ensuring safe activation and preventing unintended movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional free-drive mode is used where individual joints must be manipulated, then the robot arm can be repositioned, but the operation becomes difficult in confined spaces or when joints are obstructed
Solution Approach 1:
The patent introduces an intermediary tool (teaching tool with force sensor) that mediates between the operator and the robot arm joints. Instead of directly manipulating obstructed joints, the operator applies force to the teaching tool, which then translates this force into appropriate joint movements through the controller, solving the problem of difficult joint manipulation in confined spaces
Solution Approach 2:
The patent replaces direct mechanical joint manipulation with a force-sensitive teaching tool interface. The mechanical system of directly turning joints is substituted by applying forces to the teaching tool, with the controller translating these forces into joint movements, thereby simplifying the operation especially when joints are physically obstructed
2Reliability
If payload weight is manually entered into the kinematic model, then the controller can calculate required torques, but users often have difficulties setting correct payload information or ignore/forget to set it
Solution Approach 1:
The system performs self-service by automatically determining payload weight through force measurements during free-drive mode operation. The force sensor data collected while the operator manipulates the robot arm is processed by the controller to calculate the actual payload weight, eliminating the need for manual entry and ensuring accurate payload information is always available
3Ease of operation
If free-drive mode is activated without proper safety checks, then the robot arm can be freely repositioned, but hazardous situations may occur due to incorrect payload weight calculations
Solution Approach 1:
The system performs preliminary action by conducting safety checks and determining payload weight before allowing free-drive mode operation. The controller measures forces during an initial phase, calculates payload weight, and verifies safety parameters before enabling unrestricted robot arm movement, thereby preventing hazardous situations from incorrect payload calculations
Solution Approach 2:
The system implements feedback by continuously monitoring force sensor data during free-drive mode and using this information to verify payload weight calculations. The controller processes real-time force measurements to ensure accurate payload knowledge, providing feedback that prevents hazardous operations and allows safe, free robot arm repositioning
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
The solution enables safer and more user-friendly operation in free-drive mode by allowing external forces to change the robot arm's posture without complex joint manipulation, while also reducing the risk of hazardous situations due to incorrect payload weight calculations.
Implementation Method 1
The free-drive activation signal can be established by a user applying a force to a force sensor
Implementation Method 2
the robot controller is configured to control the motor torque provided by the motor of the robot joints based on joint encoders and a dynamic model of the robot
Implementation Method 3
the robot arm comprises a robot base which serves as a mounting base for the robot arm; and a robot tool flange where to various tools can be attached
Data Source
AI summary
The invention relates to a robot controller controlling a robot arm, the robot controller is configured to maintain the robot arm in a static posture when only gravity is acting on the robot arm and allow change in posture of the robot arm 5 when an external force different from gravity is applied to the robot arm. The free-drive mode of operation is activatable by a user establishing a free-drive activation signal to the robot controller, which in free-drive mode of operation is configured within at a free-drive safety period to allow a part of said robot arm to be moved within a virtual three-dimensional geometric shape 10 surrounding the part of the robot arm.