Force Measurement Device with Capacitive Sensors
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Solution Overview
Problem
Existing force measurement devices are inadequate for high precision measurements, particularly in tribology, as they struggle with accuracy in low-force applications, alignment of measurement axes, and distinguishing between tangential and normal forces, leading to errors and limited measurement range.
Innovation Solution
A force measurement device with a support structure comprising a fixed body and an intermediate mobile body connected via elastically deformable connections, utilizing contactless capacitive displacement sensors to measure displacements and extrapolate forces along different axes, allowing for precise calibration and differentiation of forces and moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force measurement devices are used, then the device structure is simple, but the measurement precision is insufficient to discriminate between tangential and normal forces
Solution Approach 1:
The device segments the measurement function by using separate elastically deformable connections for different measurement axes (normal force and tangential force), allowing independent measurement of each component with dedicated sensors, thus achieving high precision discrimination between force directions
Solution Approach 2:
The patent introduces elastically deformable connections as intermediary elements between the force application point and the sensors. These connections convert applied forces into measurable displacements while isolating the measurement system from direct mechanical loading, thereby improving measurement precision without requiring overly complex sensor arrangements
2Reliability
If devices with rigid pillars are used to transmit forces, then the structure is stable, but the linearity of force measurement is insufficient and the measurement range is limited
Solution Approach 1:
The patent replaces rigid pillars with elastically deformable connections that dynamically adapt to applied forces within their elastic range. This allows the structure to maintain stability through elastic recovery while accommodating a broader measurement range through controlled deformation, enabling linear measurement across varying force magnitudes
3Adaptability or versatility
If multi-axis sensors are used to measure forces in multiple directions, then the measurement capability is enhanced, but the alignment accuracy of measurement axes deteriorates
Solution Approach 1:
Instead of using complex multi-axis sensors that require precise alignment, the patent segments the measurement into separate single-axis measurements using individually aligned elastically deformable connections and sensors for each force component, thereby maintaining high alignment accuracy for each measurement axis
Solution Approach 2:
The patent replaces complex mechanically-aligned multi-axis sensors with a system using elastically deformable connections coupled with contactless capacitive displacement sensors. This substitution eliminates mechanical alignment issues between sensor axes while maintaining the ability to measure forces in multiple directions through separate measurement chains
4Device complexity
If contact sensors are used to measure displacements, then the measurement mechanism is simple, but measurement errors increase due to contact interference
Solution Approach 1:
The patent replaces contact-based displacement sensors with contactless capacitive displacement sensors. This substitution eliminates measurement errors caused by contact interference while maintaining relatively simple measurement mechanisms through electrical field-based detection of displacement
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 device achieves high precision with resolution down to 10µN and 0.1N.mm for forces and moments, with coefficient measurement uncertainty of 10^-4 or less and cross-axis reaction values below 1%, and maintains linearity error below 1% across a range of 0.01N to 10N.
Implementation Method 1
displacement sensors of the capacitive type connected to the processing device. The contactless sensors make it possible to measure with high precision the displacement of the mobile body with respect to the fixed body
Implementation Method 2
an intermediate mobile body (42) connected to the fixed body (41) via at least one elastically deformable first connection (61, 62)
Data Source
Figure 1~2
Figure 3~6
Figure 7
AI summary
The invention relates to a device for measuring forces, comprising: a first body (41) intended to be immobilised; a second body guided in at least one first translational direction with respect to the first body by a first link; a third body (43) intended to be stressed and guided with a least three degrees of freedom with respect to the second body via a second link that is elastically deformable in at least one second direction perpendicular to the first; at least first to fourth contactless sensors (51) of the movement of the third body with respect to the first body, said first to fourth sensors measuring said movement in four respective non-collinear directions; and a processing circuit for calculating the forces applied to said third body depending on the movements measured by said first to fourth sensors.