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Research Papers

Analysis, Design, and Control of an Omnidirectional Mobile Robot in Rough Terrain

[+] Author and Article Information
Martin Udengaard

Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139mru@alum.mit.edu

Karl Iagnemma

Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139kdi@mit.edu

J. Mech. Des 131(12), 121002 (Nov 03, 2009) (11 pages) doi:10.1115/1.4000214 History: Received November 23, 2008; Revised August 24, 2009; Published November 03, 2009; Online November 03, 2009

An omnidirectional mobile robot is able, kinematically, to move in any direction regardless of current pose. To date, nearly all designs and analyses of omnidirectional mobile robots have considered the case of motion on flat, smooth terrain. In this paper, an investigation of the design and control of an omnidirectional mobile robot for use in rough terrain is presented. Kinematic and geometric properties of the active split offset caster drive mechanism are investigated along with system and subsystem design guidelines. An optimization method is implemented to explore the design space. The use of this method results in a robot that has higher mobility than a robot designed using engineering judgment. A simple kinematic controller that considers the effects of terrain unevenness via an estimate of the wheel-terrain contact angles is also presented. It is shown in simulation that under the proposed control method, near-omnidirectional tracking performance is possible even in rough, uneven terrain.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

An example of a sliding wheel(from Ref. 8)

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Figure 2

An example of a robot using four Mecanum wheels (from Ref. 9)

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Figure 3

A schematic showing the omnidirectional capabilities of a Mecanum wheel driven omnidirectional robot (from Ref. 9). The solid arrows indicate the driven direction of each wheel, and the dashed arrows indicate translation and rotation of the robot.

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Figure 4

A schematic showing a spherical wheel (left), and its use on an omnidirectional wheelchair (right) (from Ref. 12

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Figure 5

A schematic showing a steerable wheel (left), and its use on an outdoor mobile robot (right) (from Ref. 17)

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Figure 6

Active split offset caster wheel assembly front view (left) and side view (right)

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Figure 7

Mean isotropy for a four ASOC omnidirectional robot

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Figure 8

Average isotropy for an omnidirectional mobile robot driven by three ASOC modules as a function of Lsplit/Loffset

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Figure 9

Top view of representative vehicle for ASOC location analysis

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Figure 10

Isotropy as a function of ASOC module relative location

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Figure 11

ASOC module on flat and rough terrain. Rough terrain can cause the module to pivot about the β axis, decreasing the effective Lsplit.

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Figure 12

Mean isotropy as a function of Lsplit/Loffset and terrain angle

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Figure 13

Illustration of an ASOC-driven omnidirectional mobile robot. This robot has four ASOC modules spaced at 90 deg intervals.

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Figure 14

The circles represent the boundaries of the ASOC module workspace. To avoid ASOC interference, they should not intersect.

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Figure 15

Rear view of ASOC with wheel-shaft interference

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Figure 16

Depiction of rwheeleffective

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Figure 17

A four view drawing of a point vehicle design

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Figure 18

Coordinate frame assignments for an ASOC-driven omnidirectional mobile robot. Some wheel and axle frames are hidden for clarity.

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Figure 19

Wheel-terrain contact angle γn,m. The gray vector is parallel to the velocity of the wheel.

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Figure 20

Control scheme of an omnidirectional mobile robot

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Figure 21

Example of terrain used in simulation, with σ=4.5

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Figure 22

Top view of robot path tracking a square on rough terrain

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Figure 23

Velocity magnitude during path tracking

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Figure 24

Top view of the body trace during square tracking on rough terrain for varying levels of controller knowledge

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