Robotic Jellyfish Installation

This is an electromechanical installation which uses a linear delta kinematic system to control the motion of a jellyfish shaped floating object in 3 dimensions within the exhibition space.

The jellyfish shaped balloon floats in a room with three strings connected to the bottom centre spread
out in different directions towards the walls. The walls in the corner of the room have large touch sensitive
letters attached to them including 3 X letters on the left wall spread horizontally, 3 Y letters on the right
wall spread horizontally, and 3 Z letters on the right wall spread vertically along the edge between the two
walls.

The original goal of this project was to develop an immersive installation for which multiple visitors could interact simultaneously. Touch sensitive capacitive letters attached to the wall were intended to control the motion of the jellyfish and generated sound effects. However due to development time limitations, the exhibited version included the jellyfish following a randomised path along with a separate work-in-progress version of the touch sensitive letters and sound system.

System design

The jellyfish floating object is made from a 1 metre diameter helium filled balloon with additional foil pieces attached. Three nylon strings are attached to the base of the balloon which hold it in position.

The nylon strings are routed through 3 wall mounted attachment points arranged in a triangle from which they are redirected to a single base station. The base station contains three stepper motors with spools around which the nylon strings are wound. The control PCB accurately controls the rotation of each of the motors.

Operation principal

The length of the 3 tethers is changed by the winding or unwinding of the spools. Each position in the operational volume has a corresponding set of three lengths. To move the jellyfish from one position to another specified in terms of cartesian coordinates, intermediate points along the trajectory are first calculated. For each of these, the corresponding tether lengths can be calculated and spool rotation to achieve this length. Executing the movement is then a case of iterating though each set of spool rotation angles, rotating each spool from its current position to the next in fixed timesteps.

The three tether routing points
arranged in a triangle each have a length of string required to reach each point along the trajectory. When moving from one point to another some
of the tethers may need to be made gradually longer through the movement, others may need to be made shorter, or some may need to have a combination of lengthening and shortening
in order for the resultant motion to be approximately linear in 3D space.

Specifications

Manufacturing methods	3D printing, laser cutting, electronics soldering
Development tools	Solidworks (CAD), iCircuit (schematic design), Arduino IDE
Main materials	System: 3 x NEMA 17 stepper motor, HC05 Bluetooth Module, foil balloon, Helium, Nylon thread, PLA, 5mm Neodymium magnets. Motor controller PCB: Strip board, solid core wire, ICs including A4988 stepper motor drivers; Arduino nano; 8v regulator; passives. Touch sensitive letters: Mountboard, Bareconductive paint, Audio FX board, Adafruit capacitive breakout board.
Exhibited	Dyson School of Design Engineering Open House 2019.03