Exploring the Just Noticeable Interaction Stiffness Differences of an Impedance-Controlled Series Elastic Actuator
Abstract
:1. Introduction
2. Materials and Methods
2.1. Variable Torsional Stiffness Actuator
2.2. Impedance Control
- Setting A:, ,
- Setting B:, .
2.3. User Study
3. Results
4. Discussion
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Abbreviations
MDPI | Multidisciplinary Digital Publishing Institute |
JND | Just Noticeable Difference |
DC | Direct Current |
VTS | Variable Torsional Stiffness |
IV | Independent Variable |
FFT | Fast Fourier Transform |
DFG | Deutsche Forschungsgemeinschaft |
Virtual Stiffness (of the impedance control) | |
Real Stiffness (of the elastic element) | |
Interaction Stiffness (Combination of virtual and real stiffness) | |
Initial Value of Stiffness during an experiment | |
Increase in the Value of Stiffness in between movements of a trial |
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Description | Symbol | Value | Unit |
---|---|---|---|
Mass of the lever | 1.3 | ||
Distance to center of mass of the lever | 0.4 | ||
Moment of inertia of the lever | 0.29 | ||
Moment of inertia of Actuation Unit 1 | 2 | ||
Viscous friction coefficient of Actuator unit 1 | 4 | ||
Coulomb friction coefficient of Actuator unit 1 | 5.5 | ||
Shaping factor for friction model | S | 5 | 1 |
Rod length range | 0.0275–0.19 | ||
Rod stiffness (real) range | 43–220 | ||
Control stiffness (virtual) range | 43–220 | ||
Control damping (virtual) | 0 | ||
Control inertia (shaped) | 0.2 |
Cond. No. | Varied Stiffness | Initial Stiffness in N m rad−1 | of the First Trial in N m rad−1 | Stiffness Increase in N m rad−1 | Stiffness Decrease in N m rad−1 |
---|---|---|---|---|---|
1 | 100 | 100 | 20 | 10 | |
2 | 50 | 50 | 10 | 5 | |
3 | 100 | 100 | 20 | 10 | |
4 | 50 | 50 | 10 | 5 |
Cond. No. | Varied Stiffness | Initial Stiffness in N m rad | Mean No. of trials | Absolute JND in N m rad | Normalized JND in % of |
---|---|---|---|---|---|
1 | 100 | ||||
2 | 50 | ||||
3 | 100 | ||||
4 | 50 |
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Velasco-Guillen, R.J.; Schofer, F.; Bliek, A.; Beckerle, P. Exploring the Just Noticeable Interaction Stiffness Differences of an Impedance-Controlled Series Elastic Actuator. Actuators 2023, 12, 378. https://doi.org/10.3390/act12100378
Velasco-Guillen RJ, Schofer F, Bliek A, Beckerle P. Exploring the Just Noticeable Interaction Stiffness Differences of an Impedance-Controlled Series Elastic Actuator. Actuators. 2023; 12(10):378. https://doi.org/10.3390/act12100378
Chicago/Turabian StyleVelasco-Guillen, Rodrigo J., Felix Schofer, Adna Bliek, and Philipp Beckerle. 2023. "Exploring the Just Noticeable Interaction Stiffness Differences of an Impedance-Controlled Series Elastic Actuator" Actuators 12, no. 10: 378. https://doi.org/10.3390/act12100378