Introducing Omni-Pi-tent

The Omni-Pi-tent modular robot project, led by Robert H. Peck at the University of York's Robotics Lab and assisted by Jon Timmis and Andy M. Tyrrell, aims to develop a self-reconfigurable modular robot for 2 and 3 dimensional experiments into docking, morphology, self-repair, fault tolerance and other modular robotics techniques. While this design will be in no way ruggedised for operation in hostile conditions it is hoped that this design may provide a reasonable approximation of the key actuator, sensor, communications and computation capabilities that self-reconfigurable modular robots could be expected to have once they start appearing in real world use. Omni-Pi-tent aims to provide a laboratory test platform illustrating the main things we believe a modular robot for use in infrastructure monitoring and repair, disaster search-and-rescue or planetary surface exploration will be capable of. We therefore hope it can allow laboratory tests for the robot controllers and group behaviours a near future self-reconfigurable modular robotic system would use. The key features of our design are outlined below:

• Omni-directional drive: four omniwheels allow the robot to move in any direction across the ground and rotate on the spot, as well as combine these two forms of motion.

  

  Rollers around the edge enable the wheel to slide sideways while providing a forwards/backwards driving force

•  Genderless mechanical docking: a hook based genderless docking method allows single sided disconnect in case of the failure of an Omni-P-tent module. The geometry of the hooks is closely based on those used in the RoGenSid connector  [S.G.M. Hossain, C.A.Nelson, P.Dasgupta, RoGenSid- a rotary plate genderless single-sided docking mechanism... ASME IDETC/CIE 2013], with slight modifications to account for the use of 3d printed parts and an alternative alignment mechanism.

  

  The docking hooks for Omni-Pi-tent, a design adapted from Hossain, Nelson and Dasgupta's RoGenSid.

• Pitch and roll degrees of freedom between docked units: the forward docking port has pitch and roll degrees of freedom allowing the formation of complex and mobile 3D structures, this pitch and roll system uses mechanisms inspired by the SMORES modular robot [J.Davet, N.Kwok, M.Yim, Emulating Self-reconfigurable robots... 2012 IEEE/RSJ IROS] but scaled up and fitted with worm gears to prevent backdriving.

  

  Degrees of freedom for the forward docking port on an Omni-Pi-tent module

• Raspberry Pi based:  the main computer within the robotic units will be a Raspberry Pi with a full Linux operating system, allowing easy customisation and integration of a wide variety of existing libraries and software tools within controller programs. Amongst modular robotics platforms the presence of computational hardware this powerful is rare, making the Pi an especially attractive feature.

The project also aims to provide simulation models and tools for testing Omni-Pi-tent behaviours in the V-REP robotics simulator, as well as a well documented API for operating physical Omni-Pi-tent units. Later in the project, documentation, user guides and assembly manuals will be made available. Links will be provided to publications describing and featuring the platform. The mechanical elements of the design will be almost entirely 3D printable via a standard fused deposition modelling (FDM) printer, electronic components will be easily available off-the-shelf. We expect that any reasonably equipped small laboratory or workshop should be able to construct and program Omni-Pi-tent units.

An early V-REP model of the Omni-Pi-tent modular robot platform

A 3D printed omniwheel and driving cog

We hope this design can meet our expectations and prove a useful tool for the modular robotics field.