Research Papers

On the Technological Instantiation of a Biomimetic Leg Concept for Agile Quadrupedal Locomotion

[+] Author and Article Information
Elena Garcia

Senior Researcher
Centre for Automation and Robotics,
Madrid 28500, Spain
e-mail: elena.garcia@csic.es

Juan C. Arevalo

Centre for Automation and Robotics,
Madrid 28500, Spain
e-mail: juan.arevalo@csic.es

Manuel Cestari

Centre for Automation and Robotics,
Madrid 28500, Spain
e-mail: m.cestari@csic.es

Daniel Sanz-Merodio

Research Engineer
Marsi Bionics,
Madrid 28500, Spain
e-mail: daniel.sanz@marsibionics.com

1Corresponding author.

Manuscript received July 3, 2013; final manuscript received August 6, 2014; published online December 4, 2014. Assoc. Editor: Xilun Ding.

J. Mechanisms Robotics 7(3), 031005 (Aug 01, 2015) (12 pages) Paper No: JMR-13-1124; doi: 10.1115/1.4028306 History: Received July 03, 2013; Revised August 06, 2014; Online December 04, 2014

The legged locomotion system of biological quadrupeds has proven to be the most efficient in natural, complex terrain. Particularly, horses' legs have been evolved to provide speed, endurance, and strength superior to any other animal of equal size. Quadruped robots, emulating their biological counterparts, could become the best choice for field missions in complex or natural environments; however, they should be provided with optimum performance against mobility, payload, and endurance. The design of the leg mechanism is of paramount importance to achieve the targeted performance, and in order to design a leg mechanism able to provide the robot with such agile capabilities nature is the best source for inspiration. In this work, key principles underlying horse legs' power capabilities have been extracted and translated to a biomimetic leg concept. Afterwards, a real prototype has been designed following the biomimetic concept proposed. A key element in the biomimetic concept is the multifunctionality of the natural musculotendinous system, which has been mimicked by combining series elastic actuation and passive elements. This work provides an assessment of the benefits that bio-inspired solutions can provide versus the purely engineering approaches. The experimental evaluation of the bio-inspired prototype shows an improvement on the performance compared to a leg design based on purely engineering principles.

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Fig. 1

Iterative optimization of leg mass distribution by minimizing the power required at the joints. Convergence is shown in black thicker line for a mass distribution of 50%, 38%, and 12% at thigh, crus, and hoof, respectively, which for a 5-kg leg yields 2.5 kg, 1.9 kg, and 0.6 kg at thigh, crus, and hoof, respectively: (a) hip power for varying link masses and (b) knee power for varying link masses.

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Fig. 2

Hill's muscle model. F: force; CE: contractile element; SE: series element; and PE: parallel element.

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Fig. 3

Simplified block diagram of neuromuscular control system based on proprioceptive organs

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Fig. 4

Block diagram of a force controlled SEA, adapted from Ref. [27]. Xd: reference output position; Xa: actual output position; Fd: reference force on the load; Fa: actual force on the load; and KS: spring stiffness.

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Fig. 5

Curves of SDF stiffness versus maximum SDF deflection for achieving elastic energy ranging between 10 J (slow trot) and 26 J (fast trot)

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Fig. 6

Biomimetic model of a leg for agile locomotion. SEA: series elastic actuator, and SDF: superficial digital flexor.

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Fig. 7

(a) HADE2 leg prototype for agile locomotion and (b) HADE2 leg kinematics

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Fig. 8

Hip joint kinematics

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Fig. 9

(a) Knee joint kinematics and (b) fetlock joint kinematics

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Fig. 10

Control states of the locomotion cycle

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Fig. 11

SEA23-23 motor torque–speed diagram overlapped with joint requirements for average nondimensional leg speed of 0.54 considering a biomimetic leg

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Fig. 12

SEA compliance control scheme block diagram

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Fig. 13

Bode diagram of the actuator impedance (thin line) overlapped with the ideal spring–damper system (thick line)

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Fig. 14

Measurements on the HADE2 leg during seven locomotion cycles: (a) potential energy stored in the SDF during the support phase; (b) linear force exerted by the SDF; and (c) Deflection of the SDF. The duration of the support phase is shown in black thick lines.

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Fig. 15

(a) Experimental testbed and (b) close up view of hip, linear rail, carriage, and carriage stop

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Fig. 16

Sequence of the locomotion cycle of the HADE2 leg

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Fig. 17

Linear speed of the tread mill: (a) HADE2 leg with passive ankle and SDF and (b) previous HADE leg prototype with actuated ankle

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Fig. 18

Fetlock joint curves for an actuated fetlock: (a) torque; (b) angle; and (c) power. The duration of the support phase is shown in black thick line.

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Fig. 19

Fetlock joint curves for the passive fetlock with SDF: (a) torque; (b) angle; and (c) power. The duration of the support phase is shown in black thick line.




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