Motion technology meets art: the Last Train art installation

Last Train was inspired from a mesmerising encounter on a railway platform in Naples where, just missing his last train, Arad witnessed a man in a slowly disappearing carriage etching the most amazing drawings onto a glass window using a ring on his fist. Currently on exhibition at the 55th Vienna Biennale in Italy until 24th November 2013, the complete installation includes the actual production equipment and original glass etched works by the artist; with many other artists including Ai Weiwei, Anthony Gormley and Francesco Clemente also contributing their own work. For Ron Arad, the installation is about the strength of the raw carbon-based material rather than as a symbol of value and adornment, and conveys how diamond on glass has been used over centuries to convey messages of love, hate, rebellion and pain.

Heason Technology was called into the project to design and build a creative solution for the motion system after an initial prototype had confirmed but not refined the performance or dynamic aspects of the artwork as envisaged by the artist. The basic concept called for the iPad app to output coordinate touchscreen information from the artist's work via an ad hoc Wi-Fi network to a PC programme which then interpreted the information into a 2-axis mechanical positioning system, with a third axis used to position the fist and its diamond ring on and off the glass plate. It was also a prerequisite for the complete system to be housed inside a very specifically fixed size presentation cabinet - except for the iPad of course.

The original motion system, based on stepper motors, was erratic in operation and did not transfer the etched information to the glass as fast or as smoothly and accurately as required. Stepper motors were also noisy, which did not suit the tranquillity expected of the work. A solenoid used to position the diamond on the glass proved difficult to control and caused a worrying shock to the glass as it was "fired' into the etching position. Furthermore, the H-frame gantry positioning system that was fitted inside the cabinet, and restricted by its dimensions, did not allow the diamond to cover the total area of glass, limiting the visual impact of the artworks. Finally, all of the drive and control electronics could not be housed inside the cabinet, necessitating a separate control cabinet - which would be problematical to conceal for art exhibition use.

Challenging timescale

So, the challenge faced by Heason Technology to build a complete system inside of the restricted presentation cabinet in itself was pretty huge. This was compounded by the timescales required, as work on the prototype had stalled with the previous supplier. Heason was given only around 12 weeks to complete and deliver the system in time for the Vienna Biennale early in June 2013. A comfortable timescale to include a full design and necessary reviews, lead-times for components and building/testing would have been nearer double.

Using its full resources as a designer and builder of bespoke motion systems and with the full support of its distribution partners, for this project namely ABB and Danaher Motion's Thomson Division - and with many late nights - Heason was able to supply a complete system in time for the Biennale.

Using an extruded aluminium profile base frame, the clever use of M55 series Movopart belt driven linear positioning slides from Thomson in an "I' frame (or rotated "H' frame) arrangement with two synchronised parallel horizontal axes supporting a single vertical traversing axis allowed the fist and diamond to reach all parts of the glass - but only just. The "I' frame also reduced the power required when compared with an "H' frame with the two parallel axes acting horizontally. Modifications to the Thomson linear motion products involved actually machining material away from covers and using specially inverted parallel belt drive adapter plates to make the extruded aluminium profiled beams fit snugly into place. The Thomson M55 slides were specified complete with a stainless steel cover band option to protect the ball-guided bearings against the ingress of glass dust from the etching process. Many other components needed "shaving', and even cable chain required some remedial work to allow it to extend without fouling other equipment in the cabinet.

With the main mechanical system design in place, the drives, EMC filters, motion controller, computer, Wi-fi components and interfacing panel could be placed around the cabinet. It was inevitably decided that to achieve the speeds and dynamic performance required a servo motor-based system would be best employed. ABB's NextMove e100 multi-axis motion controller using its integrated Ethernet POWERLINK network for motion synchronisation was chosen for its programming and installation simplicity. This distributed drive technology system reduced wiring volume to a bare minimum over traditional servo systems with MicroFlex e100 drives connected via POWERLINK with minimal length cabling required for feedback. A MINT program on the multitasking NextMove e100 motion controller receives real-time linear position coordinates and etching axis on/off information from a C++ program on the PC that interprets the separately commissioned iPad app. This multiple move information is stored in the MINT program's move buffer and may be advanced and started on demand - streaming these positions through the program to create the smooth coordinated and contoured motion that recreates the artist's work.

Softening the impact

The parallel axis synchronisation was easily taken care of using MINT with a feature added during the start-up procedure that self-aligns the axes using a modified datum command - ensuring complete orthogonally with the vertical axis from the outset. The third axis motion for etch on/off is taken care of through a separate brushless DC motor and drive using the NextMove e100's torque limiting feature - neatly enhancing the simple on/off input command to soften the impact when placing the diamond on the glass. A combination of hard and soft limits, and torque control ensures all axes are restricted within a safe zone of the internal cabinet area.

This extraordinary motion system provides a real showcase for the capabilities of Heason Technology and the artist is extremely pleased with the result. Arad says: "It was a pleasure to work with a company that was more of a perfectionist than we ever imaged; when things were good enough for us they weren't good enough for them, and in the end we appreciated and benefited from Heason's professional attitude in a time-frame that has challenged everyone involved in the project." Arad hopes to work with Heason in the future: "Working on the Last Train project with Heason has given us the appetite for other projects that we wish to follow up on."

For further details about custom mechatronics positioning systems from Heason Technology, please visit www.heason.com.