Zippermast Extension For UGVs and More
Zippermast: Tape Measure Meets Zip
The Bavarian company progenoX supplies vehicles for unmanned exploration. The highlight of their UGVs: the extremely compact "Zippermast" which consists of three interlocked steel tapes which function similar to a zipper. A small DC motor from FAULHABER provides the unique design with reliable retraction and extension.
"Whoever sees the Zippermast for the first time is amazed by how high it can be extended", says Frank Woodcock, General Manager of progenoX. Because the housing where the mast is hidden is very small: the smallest model, the ZM4, is just under 6 inches (15 cm) high and the standard model, the ZM8, is 9.84 inches (25 cm). How far the mast can be extended can be seen from the model number - it corresponds to the height in feet. In the case of ZM8, which is easy to carry with its weight of 15.4 lbs (7kg) the mast extends to around 8.2 feet (about 2.5m). The mast of the ZM40 reaches a height of more than ~40 feet (over 12m).
Inspiration From The Tape Measure
The trigger for the development of the innovative telescope technology was a request from the American armed forces. They were searching for a particularly compact and robust system which can be used on unmanned vehicles. For the design of the Zippermast, its developer, George Woodruff, was inspired by a metal tape measure, which can be extended without kinking due to the tension caused by its curvature. Woodruff used three steel tapes and interlinked them when extending according to the zipper principle. In this way, the flexible tapes become a stable mast.
The three tapes made out of spring-tempered stainless steel are wrapped around coils and arranged in relation to each other at angles of 120 degrees. A guiding spindle, which is in the middle of this triangle, grips the tapes in the beveled slots provided. The tapes are rolled upwards by the rotation of the guiding spindle. Their jagged outer edges interlock with each other. The Zippermast can be extended to any position in between. No additional locking mechanism is required to hold this position: the weight of the tapes and the load rest on the guiding spindle's thread which can only be moved by rotation, like the nut on a screw.
"When I saw the Zippermast for the first time, I was immediately excited by the design principle", recollects Frank Woodcock. He acquired the technology in the US back in 2012 and brought it to Germany. He reworked the telescopic mast with his team from progenoX and got it ready for series production. Customers are primarily organizations such as the fire departments, emergency services, disaster control, civil defense and police stations. They mostly deploy the masts for monitoring and surveillance purposes – hence in the area for which it was originally designed. But the Zippermast has also proven itself to be useful at other tasks, such as inspecting pipes and shafts. Thus, it is used in nuclear power plants in order to search the ventilation systems for cracks and foreign objects.
Saves Space While Providing Stability
Thanks to the coiled tapes, the Zippermast finds space in very small housing. Another advantage of this design: the diameter of the Zippermasts remains constant in any position along the entire length of the mast – unlike telescopic masts which consists of components nested into each other. Thus, enough space in the interior of the masts remains to lead the cable through the guiding spindle to the head and be protected from outside influences.
Furthermore, its design principle makes the Zippermast extremely stable. This sturdiness is increased further by heat treatment of the steel tapes. The coiled tapes are heated while on the coils and subsequently cooled again. The crystal structure of the steel adapts itself to this position and seeks to adopt it. Tension is therefore generated by rolling up the tapes which further stabilizes the mast. Thanks to its stability, the Zippermast can also extend horizontally and be loaded.
Suitable for Challenging Applications
ProgenoX has done a lot to make the Zippermast fit for everyday use. The steel tapes are coated with a special surface coating in order to minimize wear. The guiding spindle is hardened in a heating process, the electronics molded. Furthermore, the originally used spindle motor has been replaced. "When selecting the optimal drive, we received outstanding technical support from MICROMO and FAULHABER", emphasizes Frank Woodcock.
As the Zippermast is often used under the most severe conditions, it must have a particularly robust and long-lasting motor. Furthermore, it was important to achieve very high performance at low volumes. "The motor which drives the guiding spindle, had to find space between two of the three coiled steel tapes and could only have at most a diameter of 32 millimeters", recollects Andreas Eiler, who supervised the project. Nevertheless, the micro DC motor had to deliver high output torque in order to extend the mast quickly, even when loaded. They therefore jointly decided to use a FAULHABER small DC motor. This provides a rated torque of 120 mNm with its powerful rare-earth magnets. The Zippermast also requires a very powerful drive. Here, the choice fell on a FAULHABER planetary gearhead, because, as Andreas Eiler emphasized, "They are made solely from steel components".
With this, the motor can also work reliably under the most adverse conditions and it has an extremely robust housing made from highly-resistant plastic. The micro DC motor thereby fulfils the requirements for protection class IP68: keeping both dust and water away, as well as offering resistance to chemicals, UV and infrared radiation. The micro DC motor also drives the saltwater resistant variants of the Zippermast which can be integrated, for example, in a buoy in the ocean or inlets. Woodcock even believes applications in space are conceivable; he has already applied to participate on two projects. "The Zippermast can be used as a boom for small and medium-sized satellites antennas or optical devices, for example. In addition, we are working together with the company ODGARGO who supply robot vehicles to the space agencies, NASA and CSA. We have just installed the Zippermast on one of the ARGO robots which may be used for a planned Mars mission. I figure we have a good chance to be involved in one of these space projects."
For more applications similar to this one, visit the Robotics and Industrial Automation applications page. To learn more about innovative designs and motion solutions from MICROMO and FAULHABER, contact a member of our team, today.