The striking music played by eight cellists fills the space. Suddenly the space is illuminated by light effects, while eight arms rise up slowly behind the musicians and close up around them like a cocoon. This special design – called COCON – was created by artist Nick Verstand and realised in collaboration with fellow artists Daniël de Bruin (mechanics) and Wes Broersen (software). Festo implemented the electric drive and motion technology that was required to sync the movements every 4 ms in real time with the music and the surroundings.
The most beautiful designs are often the creation of an imaginative and artistic brain. However, translating these into practice is not always a straightforward process. For the solution and all its different facets to be successfully realised, the right questions need to be asked and every issue needs to be identified.
COCON is an excellent example of a project that has well and truly achieved this. Every team member had their own specialism yet also an affinity with those of other team members. This is crucial when people need to understand one another and want to achieve the goal that has been set.
The challenge
Project COCON started when a group of eight cellists asked artist Nick Verstand to add some energy and excitement to their stage performance. Their wish was to combine their performance, in which sound and possibly 2D images take centre stage, with 3D movements. It was as if this request had been made for him; it fitted in perfectly with his portfolio of special and engaging spatial audiovisual compositions. Nick: “My designs are mostly autonomous installations through which I like to explore the boundaries between the material and immaterial worlds during live performances. Interacting with the environment based on the “here and now” is a challenge that I like to meet head-on.”
For this ensemble of eight cellists, who usually sit in a semi-circle on the stage, he developed a structure in which a 3.5-metre-long arm – a “sentinel” – moves along with the music. The arms bend over the cellists like tentacles, creating a kind of cocoon that hides as well as protects the musicians. In addition, the arms can turn around on their axis, and are equipped with a rotating head that offers options for creating light and smoke effects.
Nick: “This design presented us with two challenges. Firstly, the mechanical and drive technology that would be needed to enable the arms to make all the required movements. And secondly, how to control the complete system. I wasn’t looking for a preprogrammed movement of the arms, but for the movements to be determined by the music and the environment, in real time. This meant that the movements literally had to be able to change every second, but always in a natural, fluid way, not jerkily like a badly adjusted machine that reacts slowly. To achieve that, we were searching for an extremely precise control system with a high resolution.”
Mechanics and actuation
Nick often works together with Daniël de Bruin on his projects. This hybrid artist and designer is already credited with many special mechanical constructions that are viewed by tens of thousands of people on social media. Driven by his own ideas and reflections, he creates personal designs and takes on assignments for the entertainment and theatre world. “Daniël is someone who understands my artistic approach like no other but is also able to translate it into effective technology,” explains Nick.
COCON required a solid plan. Daniël: “When working on previous projects, we would often find that the motors had their limits. Their power, speed, torque, precision, dynamic response, flexibility, etc. were often just not sufficient. For COCON, that had to be different. The arms would need to be working together seamlessly, be absolutely precise as well as reliable – especially because there would be eight people playing the cello underneath the structure. And the absolute accuracy was needed to synchronise the movements of the eight elements and to create the required light effects, too. These are produced by lasers that are positioned a few metres away from the stage. The beams they transmit are received and reflected by small mirrors in the head of the arm. A small deviation in the position of the mirror caused by an imprecise rotation of the head would, at a larger distance, lead to the laser beams completely missing the mirrors and the desired light effect would fail.”
Contact Festo
Since the team had no previous experience with industrial components, they contacted Festo. Daniël: “During our first meetings, I was struck by how open the company was to unusual requests. But then I don’t work for the industry but for the entertainment world where demands are all about dynamics, aesthetics, surprise effects and the like. It is fabulous when a supplier of technical components and know-how can look beyond all that and has the right approach for this type of transformational project.”
The instant connection between the two parties was also the basis for their success. Festo set to work, diving into every technical challenge that the design presented. What motors are powerful enough to provide enough torque, enabling the long arms to bend? What motors are quick and accurate enough to rotate the head at the end of the arms? And most importantly, what controller is fast and dynamic enough to be able to react quickly to the environment and the music?
Controller
This last part of the design was completed thanks to the collaboration between Festo and Wes Broersen. Much like Nick and Daniël, Wes runs his own company as a creative technologist, specialising in Sonic Interaction Design. This means that he focuses on the design of a space using light and sound by using technology. It would turn out to be a perfect fit with Nick’s designs. “I used Touch Designer for these designs. This software package is specially geared towards the entertainment world where aesthetics and special effects play a central role. The design for COCON was aimed at a dynamic control. As mentioned earlier, we weren’t after preprogrammed movement or a movement from A to B, but movements that are triggered by specific cues in the music or simply in real time and manually via a joystick.
Based on the animation that Wes made using Touch Designer, Festo selected a suitable controller that met the requirements for dynamic response and (repeat) accuracy.
End result
The final design is a structure with eight arms, each 3.5 metres long, which are positioned behind the eight cellists. Every arm has three articulated joints so they can bend forwards. In addition, they can rotate max. 80° around their own axis. At the top, they are – as requested – equipped with a two-axis rotary head in which the mirrors and the outlet of the smoke machine are installed. Nick: “We used a total of 32 motors for the eight arms, which can be controlled with an accuracy of 0.01 mm. In combination with the controller from Festo, this allowed us to move the arms flexibly and naturally. When combined with the control system from Festo, it became possible to move the arms flexibly and naturally, and based on what was happening in real time; this was unique for us and an impressive result." Wes adds: "It was quite special that Festo was able to translate the animations from my software to an input that can be processed by an industrial controller and used to operate the actuators. That seemed a real challenge to me, but we succeeded, both in terms of the accuracy and the resolution that was needed." Daniel concludes that, "As far as we are concerned, it is a really satisfying end result for one of the larger commissions that we have ever realised together. And the cooperation with Festo has really give us a taste for more".
COCON is certainly not an "end point" for the young artists, but a source of inspiration for new ideas. Especially now that they know what the available technology from Festo can do. "It gives us the confidence to build more complex structures."
The technology behind COCON
The simultaneous actuation of the eight arms and enabling them to move synchronously in 3D was a challenge, even for the engineers from Festo.
The solution for getting the arms to bend was a system consisting of an electric ball screw with a 48 V servo motor. The motors were powerful enough to provide the required torque, while the servo principle with feedback supplied the (repeat) accuracy that was needed. On the side of the head are two ball screw actuators that implement the necessary rotation.
The intelligence which enables the arms to follow the music or the joystick is integrated in the overall motion control system CPX-E. It receives the signals from the animation software and translates these into a motion path; the points are recalculated every 4 ms. The computing power is used to continuously interpolate and even out peaks and troughs in order to move as fluidly as possible to the next point, whether or not the arm actually reaches that point or changes course half-way through. The PLC and soft motion controller can be programmed completely as desired, allowing the arms to operate independently. This can be useful, for example, when performances are often staged in a similar way.