Electric Actuator Position Referencing Without Force Sensors

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Solution Overview

Problem

Existing methods for calibrating the drive position of production tongs, such as welding tongs, clinching tongs, or crimping tongs, rely on force sensors, which are not always available, especially in force sensorless systems, leading to difficulties in determining the closed position accurately due to drift and frictional forces.

Innovation Solution

A method that determines the drive position of one tong half in a closed position by electromotive actuation, multiple position measurements, and a compensation calculation using a time-following error function to find the zero crossing point, allowing for calibration without a force sensor, and compensating for frictional forces by closing the tongs at a constant speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If force sensors are used to determine closed position, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improveclosed position detection accuracyVSAvoidforce sensor requirement

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention extracts the force sensor from the system entirely, replacing it with a method that uses only position measurements and following error analysis from the existing electric drive control system. The closed position is determined by analyzing the time-following error function without any force sensing components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mechanical force sensing system is replaced with an electrical/control-based method. Instead of using force sensors to detect contact, the invention uses the electric drive's position control system and analyzes following errors in the position loop to indirectly detect the closed position through the time-following error function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If multiple position measurements and compensation calculation are performed, then manufacturing precision is improved, but loss of time increases

Engineering Contradiction:

Improvedrive position calibration accuracyVSAvoidcalibration time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The system performs preliminary position measurements and following error recordings during the closing motion before the actual closed position is reached. This preliminary data collection allows the compensation calculation to be performed efficiently once contact is detected, reducing the total calibration time while maintaining precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention uses feedback from the electric drive's position control system, continuously monitoring following errors during the closing motion. This real-time feedback enables the system to detect the closed position event and trigger the compensation calculation at the optimal moment, balancing precision and speed.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2485108B1Method for referencing an actuator position of at least one electric actuator

Publication Date: 2015.06.03 KUKA DEUT GMBH

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AI summary

The invention relates to a method for referencing a drive position of an electric drive (20) of at least one jaw half (14, 16) of a manufacturing pliers (10, 12) in a closed position of two jaw halves (14, 16) and a system of a manufacturing pliers (10, 12), in particular a welding pliers (12), clinching pliers or crimping pliers and a respective control device for actuating the manufacturing pliers (10, 12), which is configured to carry out a method of such.