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Research Papers

Design and Implementation of a Distributed Variable Impedance Actuator Using Parallel Linear Springs

[+] Author and Article Information
Mohammad Hasan H. Kani

Advanced Control Systems Laboratory and
Cognitive Robotics Laboratory,
Control and Intelligent Processing
Center of Excellence,
School of Electrical and Computer Engineering,
College of Engineering,
University of Tehran,
Office No. 110,
North Kargar Street,
Tehran 1439957131, Iran
e-mail: h.kani@ut.ac.ir

Hamed Ali Yaghini Bonabi

Cognitive Robotics Laboratory,
Control and Intelligent Processing
Center of Excellence,
School of Electrical and Computer Engineering,
College of Engineering,
University of Tehran,
Office No. 514,
North Kargar Street,
Tehran 1439957131, Iran
e-mail: h.yaghini@ut.ac.ir

Hamed Jalaly Bidgoly

Cognitive Robotics Laboratory,
Control and Intelligent Processing
Center of Excellence,
School of Electrical and Computer Engineering,
College of Engineering,
University of Tehran,
Office No. 402,
North Kargar Street,
Tehran 1439957131, Iran
e-mail: jalaly.hamed@ut.ac.ir

Mohammad Javad Yazdanpanah

Advanced Control Systems Laboratory and
Cognitive Robotics Laboratory,
Control and Intelligent Processing
Center of Excellence,
School of Electrical and Computer Engineering,
College of Engineering,
University of Tehran,
Office No. 730,
North Kargar Street,
Tehran 1439957131, Iran
e-mail: yazdan@ut.ac.ir

Majid Nili Ahmadabadi

Cognitive Robotics Laboratory,
Control and Intelligent Processing
Center of Excellence,
School of Electrical and Computer Engineering,
College of Engineering,
University of Tehran,
Office No. 734,
North Kargar Street,
Tehran 1439957131, Iran
e-mail: mnili@ut.ac.ir

1Corresponding author.

Manuscript received April 27, 2015; final manuscript received November 25, 2015; published online January 6, 2016. Assoc. Editor: Robert J. Wood.

J. Mechanisms Robotics 8(2), 021024 (Jan 06, 2016) (12 pages) Paper No: JMR-15-1100; doi: 10.1115/1.4032202 History: Received April 27, 2015; Revised November 25, 2015

This paper introduces a distributed variable impedance actuator that provides independent control of the actuator's angular position and its impedance. The idea for the actuator was inspired by the morphological structure of muscles and tendons. The system to be presented can be used as both a variable impedance actuator as well as a passive piecewise linear spring. Moreover, the actuator has an adequate number of degrees-of-freedom to approximate any nonlinear spring characteristics because of its distributed nature. Using distributed torque production subsystems with small and low power motors makes it possible to use this actuator in many applications such as prosthesis, artificial limbs, and wearable robots. The stability of the system discussed and the conditions that ensure the system stability are presented. Finally, a proof-of-concept actuator design is presented, as well as experimental results which confirm that the proposed distributed variable impedance actuator can be implemented in practical applications.

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References

Figures

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Fig. 1

A scheme of the distributed variable impedance actuator

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Fig. 4

Set-point tracking of the actuator: (a) the joint angular position and (b) the joint impedance value

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Fig. 5

Time variations of the left and right side springs' deflections: (a) joint's left side springs' deflections and (b) deflections of the right side

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Fig. 6

Power consumption of our proposed variable impedance actuator in five different frequencies versus all of the possible joint impedance values

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Fig. 7

Power consumption of the joint versus the joint's impedance values. For each impedance, the power consumption for all of the possible cases of choosing (Ktotl,Ktotr)/r2 is plotted with circles. The curve connects the minimum power consumption points and the value of (Ktotl,Ktotr)/r2 is also written for these minimum points.

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Fig. 8

Joint's angular position and its impedance diagrams while a constant torque of 0.5 N·m for 0.3 s is exerted to the joint as an external disturbance at the time instance t = 2

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Fig. 3

(a) Control block diagram of the distributed variable impedance actuator and (b) closed-loop control system of DC motors

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Fig. 2

Torque–displacement characteristic of the passive piecewise linear spring

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Fig. 10

Set-point tracking performance of the designed actuator: (a) the joint angular position and (b) the joint impedance value

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Fig. 11

Magnification of the joint angular position around the time intervals of [4.75, 8.75] (s) and [24.5, 28.5] (s)

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Fig. 12

Disturbance rejection behavior of the actuator

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Fig. 13

Power consumption of the joint in four different frequencies and three different joint impedance values

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Fig. 9

Mechanical structure of the designed distributed variable impedance actuator

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