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Design Innovation Paper

The Wide-Open Three-Legged Parallel Robot for Long-Bone Fracture Reduction

[+] Author and Article Information
Mohammad H. Abedinnasab

Department of Biomedical Engineering,
Rowan University,
Glassboro, NJ 08028
e-mail: abedin@rowan.edu

Farzam Farahmand

School of Mechanical Engineering,
Sharif University of Technology,
Tehran 11365-9567, Iran;
RCBTR,
Tehran University of Medical Sciences,
Tehran, Iran

Jaime Gallardo-Alvarado

Department of Mechanical Engineering,
Instituto Tecnológico de Celaya,
TNM,
Celaya 38010, GTO, México

Manuscript received May 17, 2016; final manuscript received December 10, 2016; published online January 12, 2017. Assoc. Editor: Byung-Ju Yi.

J. Mechanisms Robotics 9(1), 015001 (Jan 12, 2017) (10 pages) Paper No: JMR-16-1145; doi: 10.1115/1.4035495 History: Received May 17, 2016; Revised December 10, 2016

Robotic reduction of long bones is associated with the need for considerable force and high precision. To balance the accuracy, payload, and workspace, we have designed a new six degrees-of-freedom three-legged wide-open robotic system for long-bone fracture reduction. Thanks to the low number of legs and their nonsymmetrical configuration, the mechanism enjoys a unique architecture with a frontally open half-plane. This facilitates positioning the leg inside the mechanism and provides a large workspace for surgical maneuvers, as shown and compared to the well-known Gough–Stewart platform. The experimental tests on a phantom reveal that the mechanism is well capable of applying the desired reduction steps against the large muscular payloads with high accuracy.

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Figures

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Fig. 1

(a) Schematics of the 6DOF three-legged wide-open mechanism. The legs of the mechanism are configured nonsymmetrically on semicircles on the base and moving platform, providing a frontally wide-open architecture. Each leg has two active joints (one rotary and one linear). (b) Kinematic variables of the ith leg are shown. θi is the active rotation, followed by the passive ψi rotation.

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Fig. 2

Time history of the prescribed harmonic movements, i.e., displacements and rotations, of the center of the moving platform, as well as prescribed harmonic forces and torques applied on the platform

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Fig. 3

Time history of the actuators forces and torques. The dynamic simulation is based on the inputs from Fig. 2.

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Fig. 4

Static input–output force transmission evaluation. Applied forces and torques on the moving platform are, respectively, set to 250 N and 3.2 N m. Based on Fig. 2, range of translational displacement of the center of the moving platform in x and y directions is ±5 cm; it is ±15 deg for three Euler rotations; and 0.15–0.35 m for z displacements. Darker circles correspond to larger translational and orientational displacements of the moving platform.

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Fig. 5

Architectures of the wide-open and Gough–Stewart mechanisms

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Fig. 6

Rotational workspaces of the wide-open and Gough–Stewart platforms. Cylindrical coordinates {r, θc, z} are used to represent the Euler angles {α1, α2, α3}, respectively.

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Fig. 7

Dexterous workspaces of the wide-open and Gough–Stewart platforms. At each point within the workspace, each of the Euler angles α1, α2, and α3 can be simultaneously rotated from −10 deg to +10 deg.

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Fig. 8

(a) Schematics of the detailed design of the robot. (b) The fully functional prototype of the wide-open robot. The experimental setup, including the optical stereoscopic vision system, is also shown in the figure. (c) Illustration of the robot for long-bone fracture reduction application. The robot has six degrees-of-freedom. It has a full-frontal open surface which provides a large operational field for the surgeon.

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Fig. 9

Control panel of the robot. The user can adjust the motion parameters from point 1 to point 2, including the time interval, translational and rotational step sizes, and so on. The robot is manipulated by pushing the plus or minus button for any of the six translational or rotational movements.

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Fig. 10

Experimental data in comparison with the predefined motions. Top: A circular trajectory in horizontal x–y plane. Bottom: A vertical trajectory in z direction.

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Fig. 11

Simulation of the fracture reduction on an experimental phantom. The reduction procedure was performed using the control panel shown in Fig. 9, starting from an unknown position.

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Fig. 12

High stiffness rubber bands which simulate the effects of muscular tissues are added to the system. The desired movements were accomplished with high precision, resulting in a complete fracture reduction.

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