Tensegrity structures are a class of mechanical structures that are typically composed of several rigid member components that are connected to each other by pre-stressed cables. An example of a tensegrity structure is shown in Fig. 1 (a). The primary criterion for a mechanical structure to be classified as a tensegrity structure is that: each member of a tensegrity structure must be either in pure tension or pure compression. This criterion implies that the members of any tensegrity structure do not experience shear stress or bending moments. Hence, a big advantage of tensegrity structures is that they can be designed to be both soft and structurally robust to be able to withstand high-velocity impacts. The video in [4] provides a nice explanation on the structural stability of tensegrity structures. Therefore the properties of tensegrity structures has motivated the development of several modular robots or rovers with tensegrity structures. A noteworthy example is NASA's Super Ball Bot, which is a tensegrity robot currently under development for extra-terrestrial explorations [1]. The tensegrity structure in the Super Ball Bot consists of 6 rigid rods that are suspended by pre-stressed cables, passing through its ends [See Fig. 1(b)]. Motors attached to the ends of the rods can manipulate the cable lengths and thereby induce motion to the whole system.
The goal of this project is to develop a multibody dynamic model for a tensegrity robot structure and characterize/control the motion of the rover either by developing an inverse dynamic relationship or by using a central pattern generator.
The thesis will include:
- Literature Review
- Deriving the equations of motion of a tensegrity robot with a payload.
- Modeling the unilateral contacts between the tensegrity robot and the environment.
- Develop an event-based (hybrid) dynamic simulation for the tensegrity robot based on the above work in MATLAB.
- Characterize or Control the motion of the tensegrity robot in simulation.
References
[1] Bruce J., Caluwaerts K., Iscen A., Sabelhaus A.P., and SunSpiral V., 2014 Design and evolution of a modular tensegrity robot platform 2014 IEEE International Conference on Robotics and Automation (ICRA) 34833489.
[2] https://www.nasa.gov/content/super-ball-bot
[3] https://en.wikipedia.org/wiki/Tensegrity
[4] https://www.youtube.com/watch?v=0onncd0_0-o