ORIGAMI- BASED TRANSFORMABLE WHEEL ROBOT: STAGE II
Wheel Design and Development
After analyzing the design principles and behaviors of the origami-based transformable wheel robot (Stage I), we carried out further research on the origami-based wheel structure. We developed a modified origami pattern for transformable wheels, which can generate four modes for different scenarios, including radial and axial expansion, saw shape and twisting.
OUR TEAM
YANG HUA
Structure Design
YIDE CAI
Modeling & Analysis
SHIYUE GAO
Manufacturing &
Finance
ZICHEN WANG
Pattern Design & Manufacturing
YUHAO CHEN
Electronic Control
PROBLEM
In this second stage, we were required by our customer to develop a transformable wheel robot which can be remotely controlled to transform its wheels to achieve
High acceleration, easy braking, high energy efficiency
Easy parking by omnidirectional movement
Free movement in sand, snow or other off-road terrain
High loading capacity
Good durability
PATTERN ANALYSIS
Literature Search & Benchmarking
Through the literature review, we found several different origami structures for transformable wheel robots. Then we compared the pros and cons according to our design requirements.
Modified Origami Structure
From benchmarking, we decided to make modifications based on the "Waterbomb" structure to realize all four functions, especially to enlarge the twist angle.
MODE TEST
As tested, our modified "Waterbomb" structure can realize all four modes. (In the transformation of three modes, a saw-shape surface is maintained all the time)
Kinematic Model
A kinematic model for the origami wheel has been developed to calculate the theoretical deformation ratio both in longitudinal direction and radial direction. As predicted, the deformation ratio in both directions is about 3.
ROBOT DESIGN
Concept Selection
In generating the concepts, we have applied the method of morphological analysis based on the concentration of functional synthesis. We have generated the following sub-functions to make the transformable-wheel robot.
Sub-functions:
Remotely Controllable
Wheel expansion and shrink (driving mechanism)
Twistability
Transmission Structure
Transformability of the wheel: Feasible to control
Final Design
Selection and scoring matrices were used to choose the most appropriate concepts for the final design.
Inner Structure
To realize the transformation, specific mechanisms are designed, including the inner linkage, the slider and gearbox.
Improved Design
To reduce friction and enable smooth driving performance, we improved the final design with an omnidirectional wheel on the prototype instead of the skate.
MANUFACTURING
The major obstacle in manufacturing was in the wheel fabrication — how to realize folding performance with durable materials other than paper.
Solutions for wheel fabrication
1. Main partsÂ
Technique: 3D printing — high precision and smooth surface
Materials: Resin — high stiffness and yield strength
2. ConnectionÂ
Technique: Special sewing — free rotation along the edge
Materials: Nylon string — greater tolerance against torque
Procedures
Cut the connection in each 3D printed unit.
Use string to sew the pieces together (b).
Sew 60 units together into the origami pattern (d).
Add triangular pieces on the top and bottom of the whole.
Connect the left and right sides of the whole piece.
Sew the cap piece (c) to the wheel.
FINAL PROTOTYPE
A remotely controlled robot with two transformable wheels
 The robot in expanded mode |  The robot in shrink mode |  The twist mode |
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PROTOTYPE TEST
MOVE FORWARD
TRADE OFF
To realize different functional modes, a sophisticated transformation mechanism has been developed to control the improved wheel structure with more degrees of freedom than the original “Waterbomb” structure. However, this comes at the cost of quick transformation and compact design. Future studies may help generate a better control mechanism.
MASS PRODUCTION
We developed a frame-like wheel structure, which enables mass production. However, the current sewing method requires intensive labor work. One possible solution is to replace it with a rotational link on the edge of each piece, and modules can be used to reduce costs. More experiments and tests are needed to find the best method and materials.
APPLICATION
With four functional modes, the origami-based transformable wheel has many potential applications, such as future vehicles, UVAs, ball robots, high-tech wheelchairs, segway, and etc. With some modification, it can be used in different terrains. For example, for snow or sand, a protection cover could be added to the wheel frames.