Axle Load Measurement Using Dual Position Sensors and Kinematic Stiffness
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Solution Overview
Problem
Current methods for determining axle loads on linear and rotary axes are costly, limited by the need for sensitive and expensive measurement technology, and dependent on manufacturer-specific internal sensors, which restrict their applicability and accuracy.
Innovation Solution
A method using external position measuring systems to calculate axle loads by converting measured variables from indirect and direct position measuring systems into the same physical unit, applying a conversion factor, and multiplying the resulting difference by the position-dependent stiffness of the drive kinematics to determine the current force acting on the axis, while correcting for geometric and thermal influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If machine-internal sensors and bus systems are used to determine axle loads, then measurement can be performed, but the solution is dependent on control system manufacturer and involves high costs
Solution Approach 1:
The patent uses position measuring systems (direct and indirect) as intermediary measurement devices to determine axle loads, replacing manufacturer-specific internal sensors. These position measuring systems provide universal, manufacturer-independent data that can be processed to calculate axial forces without relying on proprietary bus systems or control system internals
Solution Approach 2:
The patent replaces electrical/electronic measurement systems (internal sensors, bus systems) with a mechanical/physical measurement approach using position measuring systems. By measuring position differences and applying stiffness values, the system calculates forces without needing manufacturer-specific electronic interfaces or proprietary measurement devices
2Measurement precision
If motor current is used to indirectly determine axle loads, then measurement is possible, but detailed information about control system and drive motor is required which is not always available
Solution Approach 1:
The patent extracts the measurement function from the drive system internals (motor current, control system data) and relocates it to independent position measuring systems. This extraction eliminates the need for detailed information about control systems and drive motors, as the position measuring systems operate independently and provide all necessary data for force calculation
Solution Approach 2:
The position measuring systems are self-sufficient and do not require information from external control systems or drive motors. They independently provide position data that can be processed to determine axle loads, making the measurement system autonomous and independent of other system components
3Measurement precision
If drive motor with control system is used for indirect determination, then axle loads can be measured, but the drive motor acts as a low-pass filter so low and high-frequency axle loads cannot be determined accurately
Solution Approach 1:
The patent introduces position measuring systems as intermediary devices that directly measure position without the filtering effects of drive motors. These position measuring systems capture high-frequency position changes accurately, and the resulting position differences are used to calculate instantaneous forces, preserving high-frequency content that would be filtered by motor inertia and control systems
Solution Approach 2:
The patent replaces the drive motor-based measurement approach (which has inherent low-pass filtering characteristics) with a direct position measurement approach. By measuring position differences and applying stiffness values, the system directly calculates forces without passing through the drive motor's mechanical and electrical filtering, thus preserving high-frequency force information
4Measurement precision
If sensitive and expensive measuring technology is used to measure process forces close to the machining point, then accurate measurement is achieved, but the solution is only suitable for limited industrial applications
Solution Approach 1:
The patent creates a virtual measurement system that calculates forces from position data rather than using physical force sensors near the machining point. This copying approach replaces expensive, fragile force measurement devices with readily available position measuring systems, making accurate force measurement applicable to a broad range of industrial machines without requiring specialized hardware installations
Solution Approach 2:
The patent replaces direct mechanical force measurement (using force sensors, load cells, or force measuring platforms) with a calculated measurement approach based on position data and stiffness values. This substitution eliminates the need for expensive, installation-intensive force measurement hardware while maintaining measurement accuracy and enabling widespread industrial application
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
This approach allows for accurate and cost-effective determination of axle loads independently of the manufacturer, enabling precise monitoring of process forces during machining without requiring complex software solutions or machine-internal data, thus improving the accuracy of force measurement.
Implementation Method 1
The measured values of both position measuring systems (MG direct MS and MG indirect MS) are first converted to the same physical unit. The conversion is performed using the conversion factor UF.
Implementation Method 2
If this difference is multiplied by the position-dependent stiffness k (x Pos ) of the drive kinematics between the two measuring points, under ideal conditions the current force F axle load, which acts on the axle in the axial direction, is obtained
Data Source
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AI summary
The invention relates to a method for determining an axle load having effect on a linear or round axle having two position measurement systems (9, 11). According to the invention, the linear or round axle can be driven via drive kinematics (4, 10, 12) having a drive motor. The measured values of the two position measurement systems (9, 11) are first converted to the same physical unit. From the two values thus obtained, a difference is formed, which is linked to a characteristic value. Said characteristic value characterizes a position-dependent stiffness of the drive kinematics (4, 10, 12) between the two measurement points.