Multi-axis Force Sensor with Sectorized Strain Gauge Bridges
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Solution Overview
Problem
Current multi-axis force measuring devices face challenges in achieving high sensitivity and stiffness while maintaining low crosstalk, zero stability, and cost-effectiveness, particularly in detecting forces and moments in dynamic manufacturing processes, with existing piezoelectric and strain gauge-based sensors having limitations in sensitivity, rigidity, and thermal susceptibility.
Innovation Solution
A multi-axis force measuring device with a tubular deformation zone divided into at least 8 sectors, where deformation transducers form common Wheatstone bridges across opposite sectors, reducing sensitivity differences between axial and radial forces, and utilizing strain gauges for improved sensitivity and heat dissipation, allowing for simpler calibration and wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric sensors are used for multi-axis detection, then high rigidity and very high sensitivity are achieved, but zero point stability deteriorates and thermal susceptibility increases
Solution Approach 1:
The patent replaces expensive piezoelectric crystals with inexpensive strain gauges that can be easily manufactured and replaced. The strain gauges are bonded to the measuring body in a Wheatstone bridge configuration, providing a cost-effective alternative that maintains measurement capability while eliminating the thermal and stability issues of piezoelectric materials.
Solution Approach 2:
The patent changes the measurement principle from piezoelectric effect to strain gauge resistance change. By using Wheatstone bridge circuits with strain gauges bonded to the measuring body, the system detects mechanical deformation through resistance changes rather than piezoelectric voltage generation, fundamentally altering the physical parameter being measured to achieve better stability.
2Measurement precision
If piezoelectric sensors are used for multi-axis detection, then high rigidity and very high sensitivity are achieved, but crosstalk behavior worsens
Solution Approach 1:
The patent segments the measurement function into six independent Wheatstone bridge circuits, each dedicated to measuring a specific force component (Fx, Fy, Fz, Mx, My, Mz). This segmentation is achieved by strategically bonding strain gauges in specific orientations and locations on the measuring body, allowing independent measurement of each axis without interference from other axes.
Solution Approach 2:
The patent applies strain gauges with specific orientations at specific locations on the measuring body to detect specific force components. Each strain gauge is bonded in a particular direction and position optimized for detecting its designated force component, creating local measurement zones with minimal crosstalk to adjacent measurement channels.
3Reliability
If strain gauge-based sensors are used instead of piezoelectric sensors, then zero point stability improves and thermal resistance improves, but stiffness and sensitivity deteriorate
Solution Approach 1:
The patent combines multiple strain gauges into Wheatstone bridge circuits to amplify the measurement signal. By bonding four strain gauges in a Wheatstone bridge configuration for each force component, the system achieves signal amplification and noise rejection, compensating for the inherently lower sensitivity of strain gauges compared to piezoelectric crystals.
Solution Approach 2:
The patent designs the measuring body and strain gauge arrangement to simultaneously measure all six force components (three forces and three moments) using a single integrated sensor unit. The universal measuring body structure with strategically placed strain gauges provides multi-functional capability, eliminating the need for multiple separate sensors and achieving high stiffness while maintaining sensitivity through the bridge circuit configuration.
4Reliability
If multi-axis force measuring devices are designed for high overload tolerance, then collision protection improves, but sensitivity deteriorates due to safety reserve requirements
Solution Approach 1:
The patent changes the dimensional scaling approach by designing the measuring body and strain gauge arrangement to measure both small and large forces within the same measurement range. The Wheatstone bridge circuit configuration and strain gauge selection allow the system to maintain high sensitivity for small forces while withstanding large overloads without requiring excessive safety reserves, as the strain gauges and bridge circuit can handle a wide dynamic range.
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 configuration enhances sensitivity and resolution, reduces manufacturing complexity, and minimizes direction-dependent measurement errors, achieving a higher signal-to-noise ratio and increased rigidity, while allowing for higher supply voltages and improved heat dissipation.
Implementation Method 1
deformations which are caused by forces acting on the first flange-like part (1)
Implementation Method 2
deformation transducers (4) which are interconnected to form common Wheatstone bridges (X1, Y1, X2, Y2) in opposite sectors (S1 to S8)
Data Source
Figure 1~5
Figure 6~7
Figure 8~9
AI summary
The invention relates to a force measuring device for the at least three-axis measurement of forces Fx, Fy and Fz and/or moments Mx, My, and Mz, comprising a first flange-like part (1), via which the forces/moments to be measured are introduced, a second flange-like part (2), via which the introduced forces/moments are picked up and dissipated, and a tube-like deformation zone (3) connecting said two parts, via which all the tensile, compressive, torsional, and shear forces acting on the first flange-like part (1) are passed on to the second flange-like part (2). At least the innner or outer surface of the tube-like deformation zone (3) serves as an application surface (5) for deformation transducers (4), and the tube-like deformation zone (3) is subdivided circumferentially into at least eight sectors S1 to S8. The force measuring device also comprises an evaluation unit for forming measured values of at least one force component. The force measuring device is distinguished by the fact that at least one deformation transducer is arranged on each individual sector S1 to S8, all the deformation transducers of a sector are each wired to one another in a common Wheatstone bridge, and each sector on the tube-like deformation zone (3) is located opposite a second sector offset by 180° about the mid-axis (7) of the deformation zone (3) and having a similar arrangement of deformation transducers.