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Design goals

• horizontal speed as constant as possible while touching the ground (support phase)⁶⁷
• while the foot is not touching the ground, it should move as fast as possible
• constant torque/force input (or at least no extreme spikes/changes)
• stride height (enough for clearance, not too much to conserve energy)
• the foot has to touch the ground for at least half of the cycle for a two/four leg mechanism⁸ or respectively, a third of the cycle for a three/six leg mechanism
• minimized moving mass
• vertical center of mass always inside the base of support⁹
• the speed of each leg or group of legs should be separately controllable for steering¹⁰
• the leg mechanism should allow forward and backward walking¹¹

Another design goal can be, that stride height and length etc. can be controlled by the operator.¹² This can relatively easily be achieved with a hydraulic leg mechanism, but is not practicable with a crank-based leg mechanism.¹³

The optimization has to be done for the whole vehicle – ideally the force/torque variation during a rotation should cancel each other out.¹⁴

History

Richard Lovell Edgeworth tried in 1770 to construct a machine he called a "Wooden Horse", but was not successful.¹⁵¹⁶

Patents

Patents for leg mechanism designs range from rotating cranks to four-bar and six-bar linkages.¹⁷ See for example the following patents:

• U.S. Patent No. 469,169 Figure Toy, F. O. Norton (1892).
• U.S. Patent No. 1,146,700, Animated Toy, A. Gund (1915). A leg mechanism formed by an inverted slider-crank.
• U.S. Patent No. 1,363,460, Walking Toy, J. A. Ekelund (1920). A leg mechanism formed by a rotating crank with extensions that contact the ground.
• U.S. Patent No. 1,576,956, Quadruped Walking Mechanism, E. Dunshee (1926). A four-bar leg mechanism that shows the coupler curve forms the foot trajectory.
• U.S. Patent No. 1,803,197, Walking Toy, P. C. Marie (1931). Another rotating crank leg mechanism.
• U.S. Patent No. 1,819,029, Mechanical Toy Horse, J. St. C. King (1931). A crank-rocker leg mechanism with a one-way friction mechanisms in the foot.
• U.S. Patent No. 2,591,469, Animated Mechanical Toy, H. Saito (1952). An inverted slider crank mechanism for the front foot and crank-rocker for the back foot.
• U.S. Patent No. 4095661, Walking Work Vehicle, J. R. Sturges (1978). A lambda mechanism combined with a parallelogram linkage to form a translating leg that follows the coupler curve.
• U.S. Patent No. 6,260,862, Walking Device, J. C. Klann (2001). The coupler curve of a four-bar linkage guides the lower link of an RR serial chain to form a leg mechanism, known as the Klann linkage.
• U.S. Patent No. 6,481,513, Single Actuator per Leg Robotic Hexapod, M. Buehler et al. (2002). A leg mechanism that consists of a single rotating crank.
• U.S. Patent No. 6,488,560, Walking Apparatus, Y. Nishikawa (2002). Another rotating crank leg mechanism.

Gallery

Stationary

Walking

Complex mechanism

Shown above are only planar mechanisms, but there are also more complex mechanisms:

See also

• Hexapod (robotics)
• Jansen's linkage
• Kinematics
• Kinematic pairs
• Klann linkage
• Chebyshev's Lambda Mechanism
• Linkage (mechanical)
• Machine
• Mecha
• Mobile robot

External links

• Media related to Leg mechanism at Wikimedia Commons

References

1. Ghassaei, Amanda (20 April 2011). The Design and Optimization of a Crank-Based Leg Mechanism (PDF) (Thesis). Pomona College. Archived (PDF) from the original on 29 October 2013. Retrieved 27 July 2016. http://www.amandaghassaei.com/files/thesis.pdf ↩

2. P. L. Tchebyshev. Plantigrade Machine Engraving. stored in the Musée des arts et métiers du Conservatoire national des arts et métiers Paris, France CNAM 10475-0000. https://en.tcheb.ru/1 ↩

3. S. M. Song and K. J. Waldron (November 1988). Machines that Walk: The Adaptive Suspension Vehicle. The MIT Press. ISBN 9780262192743. 9780262192743 ↩

4. W. B. Shieh (1996). Design and Optimization of Planar Leg Mechanisms Featuring Symmetrical Foot-Point Paths (Thesis). PhD Dissertation, The University of Maryland. https://drum.lib.umd.edu/handle/1903/5811 ↩

5. Theo Jansen. Strangdbeest. https://www.strandbeest.com ↩

6. Ghassaei, Amanda (20 April 2011). The Design and Optimization of a Crank-Based Leg Mechanism (PDF) (Thesis). Pomona College. Archived (PDF) from the original on 29 October 2013. Retrieved 27 July 2016. http://www.amandaghassaei.com/files/thesis.pdf ↩

7. Shigley, Joseph E. (September 1960). The Mechanics of Walking Vehicles: A Feasibility Study (PDF) (Report). University of Michigan Department of Mechanical Engineering. Archived from the original (PDF) on 4 March 2016. Retrieved 27 July 2016. Alt URL https://web.archive.org/web/20160304045205/http://www.dtic.mil/dtic/tr/fulltext/u2/419858.pdf ↩

8. Ghassaei, Amanda (20 April 2011). The Design and Optimization of a Crank-Based Leg Mechanism (PDF) (Thesis). Pomona College. Archived (PDF) from the original on 29 October 2013. Retrieved 27 July 2016. http://www.amandaghassaei.com/files/thesis.pdf ↩

9. Ghassaei, Amanda (20 April 2011). The Design and Optimization of a Crank-Based Leg Mechanism (PDF) (Thesis). Pomona College. Archived (PDF) from the original on 29 October 2013. Retrieved 27 July 2016. http://www.amandaghassaei.com/files/thesis.pdf ↩

10. Shigley, Joseph E. (September 1960). The Mechanics of Walking Vehicles: A Feasibility Study (PDF) (Report). University of Michigan Department of Mechanical Engineering. Archived from the original (PDF) on 4 March 2016. Retrieved 27 July 2016. Alt URL https://web.archive.org/web/20160304045205/http://www.dtic.mil/dtic/tr/fulltext/u2/419858.pdf ↩

11. Shigley, Joseph E. (September 1960). The Mechanics of Walking Vehicles: A Feasibility Study (PDF) (Report). University of Michigan Department of Mechanical Engineering. Archived from the original (PDF) on 4 March 2016. Retrieved 27 July 2016. Alt URL https://web.archive.org/web/20160304045205/http://www.dtic.mil/dtic/tr/fulltext/u2/419858.pdf ↩

12. Shigley, Joseph E. (September 1960). The Mechanics of Walking Vehicles: A Feasibility Study (PDF) (Report). University of Michigan Department of Mechanical Engineering. Archived from the original (PDF) on 4 March 2016. Retrieved 27 July 2016. Alt URL https://web.archive.org/web/20160304045205/http://www.dtic.mil/dtic/tr/fulltext/u2/419858.pdf ↩

13. Shigley, Joseph E. (September 1960). The Mechanics of Walking Vehicles: A Feasibility Study (PDF) (Report). University of Michigan Department of Mechanical Engineering. Archived from the original (PDF) on 4 March 2016. Retrieved 27 July 2016. Alt URL https://web.archive.org/web/20160304045205/http://www.dtic.mil/dtic/tr/fulltext/u2/419858.pdf ↩

14. Ghassaei, Amanda (20 April 2011). The Design and Optimization of a Crank-Based Leg Mechanism (PDF) (Thesis). Pomona College. Archived (PDF) from the original on 29 October 2013. Retrieved 27 July 2016. http://www.amandaghassaei.com/files/thesis.pdf ↩

15. Giesbrecht, Daniel (8 April 2010). Design and optimization of a one-degree-of-freedom eight-bar leg mechanism for a walking machine (Thesis). University of Manitoba. hdl:1993/3922. /wiki/Hdl_(identifier) ↩

16. Uglow, Jenny (2002). The Lunar Men: Five Friends Whose Curiosity Changed the World. New York, New York: Farrar, Straus and Giroux. ISBN 0-374-19440-8. Retrieved 27 July 2016. 0-374-19440-8 ↩

17. J. Michael McCarthy (March 2019). Kinematic Synthesis of Mechanisms: a project based approach. MDA Press. https://mechanicaldesign101.com/2019/03/25/kinematic-synthesis-of-mechanisms-a-project-based-approach/ ↩

18. "TrotBot". https://www.diywalkers.com/trotbot.html ↩

19. Vagle, Wade. "Strider Linkage Plans". DIYwalkers. https://www.diywalkers.com/strider-linkage-plans.html ↩