As interactive exhibit specialists Aivaf Limited will attest, electro-mechanical systems for use in the public domain need to fulfil specific performance criteria. Cost efficiency, reliability and safety are, of course, high priorities. So too is the system’s ability to withstand harsh treatment and even abuse. Therefore, in selecting a linear motion system for a recent sonar exhibit Aivaf sought one that was first and foremost highly robust. Also, to meet design criteria the chosen system needed to provide minimal over-run and be easily adapted to give sufficient mounting opportunity. The product that proved equal to the task was the HepcoMotion PDU2 Profile Driven Unit.
Aivaf has vast experience in designing, building and installing mechanical and electro mechanical interactives that can be low-tech or highly engineered dependant on the client’s needs. It serves visitor and science centres, museums and indeed any themed attraction that requires an interactive. The sonar exhibit for which the PDU2 was specified is designed to demonstrate how sonar is applied in the Navy to find ships and submarines that aren’t visible to the naked eye. It also illustrates what sonar is and how it works.
Having pressed the start button, the visitor moves the destroyer to where they believe the submarine to be, using sonar to assist in establishing the optimum location. When they are satisfied with the position they press the reveal button. If the destroyer is squarely sited above the submarine they are rewarded with the sound of dropping bombs. If not, they are squirted with water!
Two HepcoMotion PDU2 units carry the destroyer and submarine the length of the exhibit. The submarine is motor driven and takes up a random position dictated by an electro-mechanical control. The destroyer is moved manually along its linear path. Both units are fitted with single turn absolute shaft encoders to provide positional feedback. This indicates to the control system the position of the ship in relation to the submarine enabling it to activate sonar sounds that become more frequent as the vessels draw closer.
“To contain costs and shorten lead times we incorporate as many proprietary products as possible,” commented Julie France, Aivaf’s Business Development Manager. “But given the need for the system to be almost over-engineered to ensure its resistance to excessive use we must have full confidence in these bought-in elements.”
As well as the mechanical design careful consideration needs to be given to the ergonomics of the system. The design is usually based around children of between 5 and 12 years however it must be suitable for all age groups. Factors such as operation height, reach and line of sight are all important. The PDU2’s compact and uniform section and low height were helpful in this regard, “And its double shaft meant we could drive one side and encode the other,” Julie France continued.
The HepcoMotion PDU2 belt driven linear transmission has proven to be a popular, high performance and cost-effective package for a variety of applications. Its Herculane wheel technology provides a combination of load capacity, speed and low friction that exceeds that of other similar sized units.
“The PDU2 units have worked without failure since installation,” Julie France concludes. “And this performance is exactly what we would expect from this product.”