Kinetostatic Design Considerations for an Articulated Leg-Wheel Locomotion Subsystem

[+] Author and Article Information
Seung Kook Jun, Glenn D. White

Mechanical & Aerospace Engineering, State University of New York at Buffalo, Buffalo, NY 14260

Venkat N. Krovi1

Mechanical & Aerospace Engineering, State University of New York at Buffalo, Buffalo, NY 14260


Corresponding author.

J. Dyn. Sys., Meas., Control 128(1), 112-121 (Nov 22, 2005) (10 pages) doi:10.1115/1.2168481 History: Received March 10, 2005; Revised November 22, 2005

Our long-term goal is one of designing land-based vehicles to provide enhanced uneven-terrain locomotion capabilities. In this paper, we examine and evaluate candidate articulated leg-wheel subsystem designs for use in such vehicle systems. The leg-wheel subsystem designs under consideration consist of disk wheels attached to the chassis through an articulated linkage containing multiple lower-pair joints. Our emphasis is on creating a design that permits the greatest motion flexibility between the chassis and wheel while maintaining the smallest degree-of-freedom (DOF) within the articulated chain. We focus our attention on achieving two goals: (i) obtaining adequate ground clearance by designing the desired/feasible motions of the wheel axle, relative to the chassis, using methods from kinematic synthesis; and (ii) reducing overall actuation requirements by a judicious mix of structural equilibration design and spring assist. This process is examined in detail in the context of two candidate single-degree-of-freedom designs for the articulated-leg-wheel subsystems—a coupled-serial-chain configuration and a four-bar configuration. We considered the design synthesis of planar variants of the two candidate designs surmounting a representative obstacle profile while supporting a set of end-effector loads and highlight the key benefits in the presented results.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Artist’s conceptions of articulated leg-wheel based locomotion systems

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Figure 2

(a), (b) Start and end of simulation with first four-bar design. Climbing of the step was unsuccessful. (c), (d) Start and end of simulation with second four-bar design. Climbing of the step was successful.

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Figure 3

(a) The chassis and wheel frames with two relative DOF and corresponding articulations with (b) zero DOF; (c) one DOF; and (d) two DOF

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Figure 10

Candidate SDCSC articulated leg-wheel subsystem surmounting the ideal step profile

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Figure 11

Actuator torque profiles of the three-link SDCSC configuration with two static precision torques

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Figure 12

Actuator torque optimization for a three-link SDCSC configuration

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Figure 13

Nomenclature of the four-bar linkage at three precision positions

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Figure 14

Kinematic configuration of four bar for desired step trajectory

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Figure 15

Actuator torque profiles of the four-bar configuration with four static precision torques

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Figure 16

Actuator torque optimization for the four-bar configuration

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Figure 4

Constrained single degree-of-freedom motions can be achieved using: (a) a single lower-pair articulation, or multiple articulations but with suitable hardware constraints in (b) a single degree-of-freedom coupled serial chain (SDCSC) or (c) a four-bar configuration

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Figure 5

Coupled kinetostatic synthesis to match desired motion and force specifications

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Figure 6

Decoupled kinetostatic synthesis with a kinematic stage and a static stage

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Figure 7

Candidate kinematic profile and precision points for the wheel axle selected so as to surmount the step

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Figure 8

Static force profile of the wheel axle traveling along the kinematic trajectory of Fig. 7 including: (a) candidate end-effector load applied at the wheel axle and (b) candidate desired torque profile intended to generate the motion

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Figure 9

(a) Three-link SDCSC-based leg-wheel design, and (b) the corresponding kinematic diagram




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