Actuators for physical human-robot interaction (pHRI) such as rehabilitation or assistive systems should generate the desired torque precisely. However, the resistive and inertia loads inherent in the actuators (e.g., friction, damping, and inertia) set challenges in the control of actuators in a force/torque mode. The resistive factors include nonlinear effects and should be considered in the controller design to generate the desired force accurately. Moreover, the uncertainties in the plant dynamics make the precise torque control difficult. In this paper, nonlinear control algorithms are exploited for a rotary series elastic actuator to generate the desired torque precisely in the presence of nonlinear resistive factors and modeling uncertainty. The sliding mode control smoothed by a boundary layer is applied to enhance the robustness for the modeling uncertainty without chattering phenomenon. In this paper, the rotary series elastic actuator (RSEA) is installed on the knee joint of an orthosis, and the thickness of the boundary layer is changed by gait phases in order to minimize the torque error without the chattering phenomenon. The performance of the proposed controller is verified by experiments with actual walking motions.

References

References
1.
Paluska
,
D.
, and
Herr
,
H.
, 2006, “
Series Elasticity and Actuator Power Output
,” in
IEEE International Conference on Robotics and Automation (ICRA)
, pp.
1830
1833
.
2.
Pratt
,
J.
Krupp
,
B.
and
Morse
,
C.
, 2002, “
Series Elastic Actuators for High Fidelity Force Control
,”
Industrial Robot: An International Journal
,
29
, pp.
234
241
.
3.
Pratt
,
G.
, and
Williamson
,
M.
, 1995, “
Series Elastic Actuators
,” in
IEEE International Conference on Intelligent Robots and Systems
, pp.
399
406
.
4.
Robinson
,
D.
,
Pratt
,
J.
,
Paluska
,
D. J.
, and
Pratt
,
G. A.
, 1999, “
Series Elastic Actuator Development for a Biomimetic Walking Robot
,” in
IEEE/ASME International Conference on Advanced Intelligent Mechatronics
, pp.
561
568
.
5.
Kong
,
K.
,
Bae
,
J.
, and
Tomizuka
,
M.
, (2009), “
Control of Rotary Series Elastic Actuator for Ideal Force-Mode Actuation in Human-Robot Interaction Applications
,”
IEEE/ASME Trans. Mechatron.
,
14
, pp.
105
118
.
6.
Kong
,
K.
, 2009, “
Mechatronic Considerations for Human Assistive and Rehabilitation Systems
,” PhD Thesis, University of California at Berkeley, Berkeley, CA.
7.
Slotin
,
J.
, and
Li
,
W.
, 1991,
Applied Nonlinear Control
,
Prentice-Hall
,
Englewood Cliffs, NJ
.
8.
Young
,
K. D.
,
Utkin
,
V. I.
, and
Ozguner
,
U.
, 1999, “
A Control Engineer’s Guide to Sliding Mode Control
,”
IEEE Trans. Control Syst. Technol.
,
7
, pp.
328
342
.
9.
Kong
,
K.
, and
Tomizuka
,
M.
, 2009, “
Sensor-Embedded Shoes Based Gait Monitoring System for Rrehabilitation
,”
IEEE/ASME Trans. Mechatron.
,
14
, pp.
358
370
.
10.
Bae
,
J.
, and
Tomizuka
,
M.
, 2010, “
Gait Phase Analysis Based on a Hidden Markov Model
,” in
IFAC Symposium on Mechatronics Systems
, pp.
746
751
.
11.
Bae
,
J.
,
Kong
,
K.
,
Byl
,
N.
, and
Tomizuka
,
M.
, 2009, “
A Mobile Gait Monitoring System for Gait Analysis
,” in
IEEE Proceeding on Rehabilitation Robotics (ICORR)
, pp.
73
79
.
12.
Bae
,
J.
,
Kong
,
K.
,
Byl
,
N.
, and
Tomizuka
,
M.
, 2011, “
A Mobile Gait Monitoring System for Abnormal Gait Diagnosis and Rehabilitation: A Pilot Study for Parkinsons Disease Patients
,”
ASME J. Biomech. Eng.
,
133
, p.
041005
.
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