Modular 2 axis laser Gimbal Technical Description
This system was designed for the third revision of “Iris” a kinetic light sculpture by Marshmallow Laser Feast. It was required to direct a laser with 2 degrees of rotational freedom, as well as dimming control of the beam. The system was also designed to support a large number of such units daisy-chained to one another, operating at a refresh rate of 60 fps. Initially I investigated the potential of using a galvo mirror system for the laser direction, but after some testing I found that the maximum angle achievable with such a system was far too narrow. Based on a previous design iteration I decided to use Dynamixel MX 28AR smart servo motors, for their cost/precision specification. The Dynamixel range also offer a number of framing options for mounting and connecting motors, which proved to reduce the final fabrication cost significantly.
For dimming control and power distribution I designed a PCB. This distributed serial data to the motors and a microcontroller that handled the dimming of the laser beam. The PCB was designed in such a way that up to 10 modular laser gimbal units could be daisy chained in series. This limitation arose from the voltage drop caused by the considerable current draw of the motors when operating at high speed.
Both the PCB, and the two axis motor assembly were encased in a laser cut aluminium box. This protected the control electronics as well as providing mounting points for the unit. I used Fusion 360 to model the box around reference geometries of both the motors and the PCB, which I designed using Eagle.
For the sculptural piece, I needed to complete a total of 40 of these units with additional spares. The PCB fabrication and assembly was outsourced, but the mechanical assembly was not so easy… As you can imagine with both the motors and the case being assembled and fixed together with machine screws, this amounted to a significant time investment! Thankfully I was not alone in this endeavour and had the help from some students from the Interactive Architecture Lab.
Once the units were completed they were mounted onto a section of extruded aluminium U-beam. This was fixed to an 8*8m cross, made with lighting truss structure. Each arm of the cross had 10 units fixed to it and the power supply and control computer were mounted on the centre of the cross. This whole structure was suspended from the ceiling of the Lowry theatre in Manchester with a winching system. In its show ready position, the cross was suspended at around 15 metres above the theatre seating.