Decoupled Six-Axis Force–Moment Sensor with a Novel Strain Gauge Arrangement and Error Reduction Techniques
Abstract
:1. Introduction
2. Structural Design and Strain Gauge Arrangement
2.1. Structural Design
2.2. Strain Gauge Arrangement
2.3. Finite Element Analysis
2.4. Measurement Principle
3. Sensor Calibration
3.1. Decoupling Matrix
3.2. Calibration Setup
- The zero point of the output signal of six filtered channels is adjusted using the error reduction technique.
- Pure forces and moments are applied to the mounted six-axis F/M sensor on the calibration jig through hanging weights with a 2.5 kg increment from +10 kg to −10 kg.
- The output voltage signal response is measured and counted for each data point corresponding to the applied load of the six-channel force sensor, and each axis of the measured force and moment is generated.
- The load is applied for 100 s, and the output voltages in each component are collected by taking the calculated average value.
- After completing the applied load, the decoupling matrix [D] is obtained using the pseudoinverse method. The output signals of the sensor and decoupling matrix are used to calculate the measured forces and moments.
4. Error Reduction Techniques
4.1. Force Filtering
4.2. Moving Average Filter
4.2.1. Voltage Zero
4.2.2. Force Offset
4.3. Error Reduction Techniques Process
4.3.1. Calibration Process
- First step: the signals from the F/M sensors should be filtered using “force filtering” techniques.
- Second step: after installing F/M into the calibration jig, before loading, “voltage zero” technique should be used to set six readings to zeros.
4.3.2. Measurement Process
- First step: to get the filtered output signal from F/M sensors using “force filtering” techniques.
- Second step: after installing F/M into the end effector and installing the tool on it, before the start of robot applications, the “force offset” process should be conducted to set six undesirably existing readings to zero.
5. Experimental Results and Discussion
5.1. Software Configuration
5.2. Experimental Results
6. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
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Crosstalk Reading (%) | Axis of Reading | ||||||
---|---|---|---|---|---|---|---|
Fx | Fy | Fz | Mx | My | Mz | ||
Applied load | Fx | - | 0% | 0% | 1% | −10% | 0% |
Fy | −1% | - | 0% | 11% | 1% | 0% | |
Fz | 0% | 0% | - | −1% | 0% | -6% | |
Mx | 0% | 7% | 0% | - | 0% | 0% | |
My | −8% | 2% | 1% | 0% | - | 0% | |
Mz | 0% | 0% | −1% | −1% | 0% | - |
Input Signal Components | Impulse Signals Response Range (V) | Filtered Output Signal (V) | |
---|---|---|---|
Fx | upper | −0.0037 | −0.00445 |
lower | −0.0052 | ||
Fy | upper | 0.00125 | 0.00028 |
lower | −0.0007 | ||
Fz | upper | −0.0086 | −0.00935 |
lower | −0.0101 | ||
Mx | upper | 0.00075 | −0.00058 |
lower | −0.0019 | ||
My | upper | 0 | −0.00095 |
lower | −0.0019 | ||
Mz | upper | 0.0028 | 0.00175 |
lower | 0.0007 |
Sensor Components | LS Best Fit Value (V/V) | Experimental Value (V/V) | Error (%) |
---|---|---|---|
Fx = 98.1 N | 0.077 | 0.075 | 2.40 |
Fy = 98.1 N | 0.089 | 0.090 | 0.80 |
Fz = 98.1 N | 0.055 | 0.056 | 1.00 |
Mx = 13.322 Nm | 0.336 | 0.323 | 3.91 |
My = 13.322 Nm | 0.433 | 0.432 | 0.28 |
Mz = 9.81 Nm | 0.153 | 0.154 | 0.45 |
Sensor Components | LS Best Fit Value (V/V) | Experimental Value (V/V) | Error (%) |
---|---|---|---|
Fx = −98.1 N | −0.077 | −0.079 | −3.10 |
Fy = −98.1 N | −0.094 | −0.093 | −0.55 |
Fz = −98.1 N | −0.060 | −0.060 | −0.19 |
Mx = −13.322 Nm | −0.340 | −0.343 | −0.84 |
My = −13.322 Nm | −0.421 | −0.413 | −1.95 |
Mz = −9.81 Nm | −0.151 | −0.147 | −2.71 |
F/M Measurement Error and Crosstalk Reading (%) | Axis of Reading | ||||||
---|---|---|---|---|---|---|---|
Fx | Fy | Fz | Mx | My | Mz | ||
Applied load | Fx | 0.61 | 0.53 | 1.01 | 0.57 | 0.33 | 1.03 |
Fy | 0.77 | 0.37 | 0.81 | 0.45 | 0.32 | 1.44 | |
Fz | 1.77 | 1.78 | 0.58 | 3.36 | 0.40 | 3.31 | |
Mx | 1.71 | 0.98 | 1.86 | 1.78 | 0.31 | 4.78 | |
My | 1.17 | 1.47 | 1.39 | 0.79 | 1.74 | 3.48 | |
Mz | 1.23 | 1.24 | 1.28 | 0.68 | 0.12 | 1.45 |
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Kebede, G.A.; Ahmad, A.R.; Lee, S.-C.; Lin, C.-Y. Decoupled Six-Axis Force–Moment Sensor with a Novel Strain Gauge Arrangement and Error Reduction Techniques. Sensors 2019, 19, 3012. https://doi.org/10.3390/s19133012
Kebede GA, Ahmad AR, Lee S-C, Lin C-Y. Decoupled Six-Axis Force–Moment Sensor with a Novel Strain Gauge Arrangement and Error Reduction Techniques. Sensors. 2019; 19(13):3012. https://doi.org/10.3390/s19133012
Chicago/Turabian StyleKebede, Getnet Ayele, Anton Royanto Ahmad, Shao-Chun Lee, and Chyi-Yeu Lin. 2019. "Decoupled Six-Axis Force–Moment Sensor with a Novel Strain Gauge Arrangement and Error Reduction Techniques" Sensors 19, no. 13: 3012. https://doi.org/10.3390/s19133012