Model-Based Evaluator for Industrial Robot Motion Limits
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Solution Overview
Problem
Industrial robots equipped with mechanical position switches are costly, require maintenance, and need periodic replacement, while electronic supervision solutions can trigger unnecessary stops due to servo control errors from dynamic effects.
Innovation Solution
A method and device using a model-based evaluator to limit robot motion by comparing modeled and measured positions, eliminating the need for hardware position switches and mechanical stops, allowing for software-controlled motion limits and improved safety evaluations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical position switches and cams are used to limit robot motion, then motion limiting function is achieved, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent replaces mechanical position switches and cams with an electronic supervision system that uses sensors to detect robot position and compares it against predefined limits. This substitution eliminates mechanical wear and moving parts while achieving the same motion limiting function through software-controlled electronic monitoring.
Solution Approach 2:
The patent extracts the motion limiting function from the mechanical structure and implements it separately through electronic supervision. The mechanical structure remains simple while the electronic system handles the complexity of position monitoring and limit enforcement, separating the limiting function from the execution mechanism.
2Device complexity
If electronic supervision with threshold monitoring is used, then device complexity is reduced, but false stops occur due to servo control errors
Solution Approach 1:
The patent applies preliminary action by using a predictive model that anticipates the robot's position based on current velocity and acceleration. This model predicts where the robot will be in the near future, allowing the system to compensate for servo lag and transient effects before they cause false limit violations, thereby preventing unnecessary stops.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual robot position through sensors and comparing it against the predicted position from the model. This closed-loop feedback allows the system to adjust the supervision threshold dynamically based on the robot's operational state, reducing false positives while maintaining safety.
3Reliability
If mechanical limit switches are installed on robot axes, then motion limits are enforced, but manufacturing cost and material usage increase
Solution Approach 1:
The patent replaces expensive mechanical limit switches with a cost-effective electronic supervision system using standard position sensors. This substitution eliminates the need for specialized mechanical components while achieving equivalent or superior motion limit enforcement through software-based control.
Solution Approach 2:
The patent makes the control system universal by using a single electronic supervision unit that can enforce motion limits on multiple axes without requiring separate mechanical limit switches for each axis. This multi-functional approach reduces overall manufacturing cost while maintaining comprehensive motion control capability.
Data Source
AI summary
A method for controlling a multi-axis industrial robot or manipulator arranged with a robot control unit. The robot or the control unit includes at least one first computer running a servo controller. A motion limit is configured for at least one axis of the robot arm. A reference signal for a robot position is sent to a robot controller together with a measurement of a position of the robot arm. The reference position is processed and the measured position and the processed reference position are then compared in an evaluator for the purpose of limiting the motion of an arm of the robot.