Description: Macintosh HD:Users:hdl0:Documents:Humanoids:Final Project:photo202.JPGFinal Project Reflection


Hannah Lyness


16-264: Humanoids

8 May 2015


Solid Mechanisms for a Personal Care Robot


Senior communities, childcare centers and health care providers could all benefit from the addition of reliable and safe assistive and companion devices. With almost one fifth of all seniors in America in regulated long-term care, million children in dozens of hours of weekly daycare and mounting emergency room wait times; there is a great need for an extremely consistent device that can provide care[1,2,3,4]. One such solution is a soft robot that can interact, analyze or provide care but lacks the potential dangers and stagnant characteristics of traditional robots.


While mobile robots like Asimo and Riba present great potential for the future of humanoid robots, they are heavy and stiff, which make them potentially dangerous and unapproachable. On the other end of the spectrum, hyper-realistic robots like the Geminoid Robots and Hanson Robotic’s Jules lack mobility, which presents definite barriers for entry into existing areas of need.








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One remedy to this predicament is to encase existing mechanisms in a bubble of soft material, though this still poses a potential falling hazard. Another is to encase light rigid bodies in soft materials. Finally, soft robotics present the potential for entirely flexible actuators and sensors to come together in a cohesive robot. In this project, I explored the possibility of using extremely light support structures and actuators to provide a proof of concept for a semi-gravitationally powered bipedal robot.








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In researching this project, I gained inspiration and information from existing passive dynamic walker research from Allen Tucker, et al., Tad McGeer, Steve Collins and Cornell University[5,6,7,8,9]. Their information helped to build my analysis of the system and the dynamics behind a passive dynamic walker. After completing this project, I looked into MATLAB as a source for simulation of these systems. I found a tremendous resource through Cornell University that can be found on this link: < >.


Following the research phase, I designed each portion of the robot on SolidWorks. To manufacture the walker, I used a 0.25 in wooden dowel for the hip and 3d printed PLA for the legs and feet. The feet were attached using 4-40 screws for easy removal and substitution. I started with a rocking robot with a wide base and large radius that was larger than the floor-to-hip length, which produces a very stable walker with a very small stride. Following this, I printed think single-dimensional feet to experiment with a walker more similar to McGeer’s. After this, I added hinges for knees, printed feet with smaller radii, experimented with weight and added arm mechanisms to one of the models to add stability. I tried to make each attachment removable to allow for the experimentation with many different variables.



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The primary parameters that I adjusted were radius of the foot, width of the stance and weight distribution. I experimented with four types of walkers: a rocking, non-jointed walker, a single-plane, swinging walker, a jointed, swinging walker and a partially actuated rocking walker. The table below presents a summary of my research. The best combinations in each experiment are represented, i.e. any success with the two characteristics triangulated on the chart will be represented with green squares. Yellow represents a walker that was “too stable” or did not carry on with constant motion. Blue represents a walker that was not stable and fell. Gray represents combinations that were not tried. Variations of each color indicate slight intermediate phases between colors.


Robot Type

Foot Radius – Above Hip

Foot Radius – Below Hip

Majority Weight Distribution – On Foot

Majority Weight Distribution – At Hip Joint

Majority Weight Distribution – Spread from Hip Joint

Foot Spread - Minimal

Foot Spread - Maximum

Simple Rocker








Simple Rocker with Arms








Semi-Actuated Rocker








Single Plane Walker








Single Plane, Jointed Walker









The video links below provide clips of the robots operating on a slight slope. A rubber substance was place on the feet of the robot in later videos, while the rubber was applied to the surface in preliminary videos. The video below is the basic rocking walker with alternatingly attached arms.


First Successful Rocking Walker

No-Knee First Attempt

No-Knee Progression

Knee Attempt

Arm and Leg Rocker




















Additionally, three padding methods were tested for limbs: application on a limb, application around a limb and application around a limb and joint. From these results, it seems that applications around a limb present the best possible combination of movement and safety. Inflated bodies around an entire joint present enticing potential for safety, but were shown to be difficult to establish and test, especially on a reduced-size scale.



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Further research includes more tweaking of parameters listed and others including more variety in foot radius and integration of a clutch mechanism in the knee robot. Additionally, new research in soft actuators and soft sensors present great possibilities for maintaining lightness and safety in a robot that is dedicated to helping humans.



[1] Harris-Kojetin L, Sengupta M, Park-Lee E, Valverde R. Long-term care services in the United States: 2013 overview. National health care statistics reports; no 1. Hyattsville, MD: National Center for Health Statistics. 2013. Web. 27 Apr 2015.

[2] Child Care in America: 2014 State Fact Sheet. Child Care Aware. 2014. Web 27 Apr 2015.

[3] Groeger, Lena, et al. ER Wait Watcher: Which Emergency Room Will See You the Fastest? ProPublic. 14 Jan 2015. Web. 27 Apr 2015.

[4] 13.3 percent in U.S. are seniors. United Press International. 7 Mar 2013. Web. 28 Apr 2015.

[5] V. A. Tucker (1975). "The energetic cost of moving about". American Scientist 63 (4): 413–419.

[6] Tad McGeer (April 1990). "Passive dynamic walking". International Journal of Robotics Research.

[7] Steve H Collins; Martijn Wisse; Andy Ruina (2001). "A 3-D Passive Dynamic Walking Robot with Two Legs and Knees". International Journal of Robotics Research 20 (7): 607–615.

[8] Steve H Collins; Martijn Wisse; Andy Ruina; Russ Tedrake (2005). "Efficient bipedal robots based on passive-dynamic Walkers". Science 307 (5712): 1082–1085.

[9] Cornell Ranger. Cornell College of Engineering. 2011. Web. 27 Apr 2015.