robust and smooth force sensor-less power assist control
DESCRIPTION
Robust and Smooth Force Sensor-less Power Assist ControlTRANSCRIPT
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Robust and Smooth Force Sensor-less
Power Assist Control
V. Salvucci S. Oh H. Fujimoto Y. Hori
The University of Tokyo
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Outline
1 Power Assist Robots without Force Sensor?
2 Proposed Force Sensor-Less Power Assist Control
3 ResultsHuman Input Based EvaluationRigorous Experimental Verification
4 Conclusions
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Outline
1 Power Assist Robots without Force Sensor?
2 Proposed Force Sensor-Less Power Assist Control
3 ResultsHuman Input Based EvaluationRigorous Experimental Verification
4 Conclusions
![Page 4: Robust and Smooth Force Sensor-less Power Assist Control](https://reader034.vdocument.in/reader034/viewer/2022042614/559664c61a28abe7338b479b/html5/thumbnails/4.jpg)
Power Assist Robots without Force Sensor?
Can we control these robots by estimating the user force with cheap sensors?
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Why without Force Sensors?
Control key point
Knowledge of user’s applied force
1 Force Sensor
2 Force Sensor-less Control(encoder based)
Why without force sensors?
Advantages
Low cost
Low weight
Compactness
Faster Response: No delay in forcemeasurement
Safety: the robot is a sensor
Difficulties
Robustness (ex: friction non-linearities)
Difficult to provide smooth assistance
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Outline
1 Power Assist Robots without Force Sensor?
2 Proposed Force Sensor-Less Power Assist Control
3 ResultsHuman Input Based EvaluationRigorous Experimental Verification
4 Conclusions
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Force Sensor-Less Power Assist Control (FSPAC)
Constant gain [Oh 2008]
Based on disturbance observer for:
Disturbance rejection
Force-to-assist estimation
Variable Gain [Salvucci 2010]
VD-TG = Velocity DependentTriangular Gain (i.e. variableimpedance)
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VD-TG = Velocity Dependent Triangular Gain
|va| VD-TG why
|va| < |v1| 0 no assistance stability in unknown environment
|va| ≈ |v2| high high assistance at low speed to overcome inertia
|va| → |v3| decrease low assistance at high and dangerous speed
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Outline
1 Power Assist Robots without Force Sensor?
2 Proposed Force Sensor-Less Power Assist Control
3 ResultsHuman Input Based EvaluationRigorous Experimental Verification
4 Conclusions
![Page 10: Robust and Smooth Force Sensor-less Power Assist Control](https://reader034.vdocument.in/reader034/viewer/2022042614/559664c61a28abe7338b479b/html5/thumbnails/10.jpg)
Human Input for a “Feeling” Evaluation
No assistance
Low backdrivability
Conventional FSPAC
Not smooth(oscillatorymovements)
Unstable
Not Robust
Proposed FSPAC
Smooth
Stable
Robust
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Experimental Apparatus
High Back-drivable System
Actuators: 1 linear motor
Sensors: 1 linear encoder
Motion is transmitted to the doorthrough the linear motor→ low friction, and highback-drivable
Low Back-drivable System
Actuators: 1 AC motor
Sensors: 1 rotary encoder
Motion is transmitted to the doorthrough the ball screw system→ high friction, and lowback-drivable
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Experiment Input
Constant-force (in absolute value) input
Applied on the doors’ end from position 1 (left) to 2 (right)
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Outline
1 Power Assist Robots without Force Sensor?
2 Proposed Force Sensor-Less Power Assist Control
3 ResultsHuman Input Based EvaluationRigorous Experimental Verification
4 Conclusions
![Page 16: Robust and Smooth Force Sensor-less Power Assist Control](https://reader034.vdocument.in/reader034/viewer/2022042614/559664c61a28abe7338b479b/html5/thumbnails/16.jpg)
FSPAC with Variable Impedance Works
Proposal
A simple-to-implement Variable Impedance Controller for Power AssistRobots with low cost Position Sensors
Advantages
1 Higher robustness:Experimentally stable for different humidity and room temperatureconditions (i.e. friction modeling error)
2 Smoother assistance:Higher assistance to the user at low velocities (=assistance when needed!)Better input tracking
3 Higher safety:No oscillatory torque references and velocities that can cause instability
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Thank you for your kind attention
Hori-Fujimoto Lab— Eco and Human-friendly Motion Control—
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References
S. Oh and Y. Hori. Generalized discussion on design of force-sensor-less power assistcontrol. In Advanced Motion Control, 2008. AMC ’08. 10th IEEE InternationalWorkshop on, pages 492–497, 2008.
V. Salvucci, S. Oh, and Y. Hori. New approach to force Sensor-Less power assistcontrol for high friction and high inertia systems. In Industrial Electronics (ISIE),IEEE International Symposium on, pages 3559–3564, 2010.