Six-axis force-torque sensor using capacitive spring elements
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Solution Overview
Problem
Existing force and torque sensors are limited in measuring forces normal to the sensor surface, unable to effectively measure in-plane shear forces and out-of-plane moments, which are crucial for evaluating and optimizing physical interactions between humans and robots or their environments.
Innovation Solution
A six-axis force-torque sensing device with spring elements allowing displacement in three orthogonal directions and rotation around three axes, utilizing electrode structures and comb-structures to measure forces and moments through capacitive read-out, enabling detection of forces in three orthogonal directions and moments around each axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-axis force sensor is used, then forces normal to the sensor surface can be measured, but in-plane shear forces and out-of-plane moments cannot be measured
Solution Approach 1:
The sensor is divided into multiple independent measurement regions: normal force measurement regions and shear force/moment measurement regions. Each region contains specific electrode pairs configured to detect particular force components, allowing simultaneous measurement of forces in three orthogonal directions and moments around each axis through segmented functional zones
Solution Approach 2:
The invention transitions from measuring only normal forces (one dimension) to measuring forces and moments in three-dimensional space. By configuring electrode pairs to detect displacements and rotations along x, y, and z axes, the sensor achieves six-axis measurement capability, adding measurement dimensions for shear forces and moments
2Adaptability or versatility
If spring elements allow displacement in three orthogonal directions and rotation around three axes, then six-axis force-torque measurement is enabled, but device complexity increases
Solution Approach 1:
The spring elements serve multiple functions simultaneously: they provide mechanical support for the top plate, enable displacement in three orthogonal directions, allow rotation around three axes, and act as the sensing mechanism itself through capacitive detection. This multi-functionality reduces the need for separate components for each function, managing complexity while achieving six-axis measurement
Solution Approach 2:
The invention combines the support structure and sensing mechanism into a single integrated system. The spring elements that mechanically support the top plate also serve as the primary sensing elements, merging structural and measurement functions. Additionally, multiple electrode pairs are combined in a single capacitive read-out system, further integrating the measurement of all six axes
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 sensing device provides accurate measurement of forces and torques in a wide range, with high sensitivity and adaptability, overcoming the limitations of prior sensors by enabling the detection of shear forces, normal forces, and moments, and scaling for various force/torque ranges and sensitivities.
Implementation Method 1
The support structure comprises spring elements for supporting the top plate on the bottom plate
Implementation Method 2
utilizing electrode structures and comb-structures to measure forces and moments through capacitive read-out
Data Source
Figure 1a~2a
Figure 2b~4
Figure 3a~3f
AI summary
A sensing device for measuring force and/or torque includes a top part with a top electrode structure, a bottom part with a bottom electrode structure, and a support structure. The support structure includes spring elements for supporting the top part on the bottom part with the top electrode structure parallel to and facing the bottom electrode structure. The spring elements provide a gap between the top and bottom electrode structures and allow displacement of the top part relative to the bottom part in three orthogonal directions two parallel and one perpendicular to the bottom plate, and for rotation of the top part relative to the bottom part around three orthogonal axes, corresponding with said two parallel and one perpendicular directions. The displacement and/or rotation induce a change in distance between and/or overlap area of the top and bottom electrodes and a corresponding change of capacitance.