Manufacturing

Tech Trends

1 Feb, 2004 By: Arnie Williams

Mars: Fourth Planet from the Sun




Figure 1. Artist rendering shows Rover's robotic arm about to abrade a rock on the surface with its rock abrasion tool (© 2002 Cornell University All rights reserved.*).

On January 16, 2004, on a clear bright day in space, engineers at ASI (Alliance Spacesystems) in Pasadena, California, held their collective breaths as a project they had poured their best efforts into faced its ultimate test. Given that this proof-is-in-the-pudding event lasted only a handful of seconds and took place 100 million miles away from their Southern California offices, there wasn't much they could do if their pet project proved faulty. But much to their joy and satisfaction, the robotic arm of the Spirit Rover deployed successfully, moving a microscope down for an up-close and personal encounter with the surface of Mars to examine the planet's dust in the closest proximity ever achieved.

This historical event-several years in the making, considering that the project began in November 2000-owed much of its success to the quality and capability of these engineers' design software-SolidWorks and the appropriately named COSMOSWorks analysis software (www.solidworks.com), according to project leader and engineering director Brett Lindenfeld. The engineering team relied on SolidWorks and COSMOSWorks, says Lindenfeld, because of their ease of use, reliability, and quality. "We came on contract with JPL (Jet Propulsion Laboratories) in November of 2000," he says, "with a requirement to deliver a design for three robotic arms by June-just six months away. The robotic arm (the arm's technical name is Instrument Deployment Device, or IDD) would also have a hand-like structure at the end to manipulate four scientific devices, adding to the complexity of the design. Two of the arms would make the trip to Mars, and the third was for testing on Earth prior to launch. We would have our first design review the following February and design finalization in just six months. The first of the actual manufactured IDDs would be delivered a year after design finalization, the second a month later, and the third a month after that."

Figure 2. The robotic arm was tested in ASI's Class 10,000 cleanroom with instrument mass models attached at the end-effector.
Figure 2. The robotic arm was tested in ASI's Class 10,000 cleanroom with instrument mass models attached at the end-effector.

The Arm

The IDD has five rotating joints and an extended length of more than one meter. The arm is mounted on the forward structure of the Spirit and Opportunity rovers and is secured during launch, landing, and rover mobility by ASI-designed restraint mechanisms at the arm elbow and the outboard end of the instrument turret. Mechanisms developed by ASI for the arm include five unique actuators that articulate the arm and position scientific instruments, the two restraint mechanisms that unlatched after the landing on the surface of Mars and provide passive restraint during rover maneuvers, contact sensors to detect proximity to targets of interest, and a complex flexprint interconnection system that traverses the rotating joints to service the electromechanical devices and instruments.

Cut Time Yet Ensure Quality

Several years would pass, yet the early-phase, six-month design timeline was crucial. The test IDD would be put through all of the experiments at special JPL test labs, but there was no way to completely recreate the Martian environment on Earth. The real test would come with the 100 million miles between the engineers and the robotic arm that would allow science to move forward or experience an expensive, heart-stopping flop. With those high stakes, Lindenfeld and his team could ill afford to work inefficiently. As much testing of full-working IDDs as possible had to be carried out.

Lindenfeld knew that they could save much time by doing fabrication in-house. ASI did 50% of its own fabrication and then contracted out the other half. To shave time and ensure quality, Lindenfeld's team took a paperless approach to design and manufacture. Through the visualization power of SolidWorks and eDrawings, engineers manipulated the five-degrees-of-freedom robotic arm in 3D and performed real-time analysis with COSMOSWorks. Key drawings were saved to Bluebeam Pushbutton PDF for use on the shop floor (www.bluebeam.com). Bluebeam PDFs had all the advantages of paper 2D drawings that fabricators work from, with the added advantage of embedded model information.



"This was no small undertaking," says Lindenfeld. "More than 300 individual piece parts had to be fabricated and more than 300 drawings needed to be made. Traditional blueprints weren't going to be efficient."

Through the paperless approach to the project, Lindenfeld figures the team cut its development time by at least 50%, and the quality checks they could make through the use of SolidWorks and COSMOSWorks ensured that the speed-up in time didn't translate into any loss of quality.

Lessons Learned

Lindenfeld notes that the tight timeframe of this project drove home like few projects before how important it is to use technology to streamline engineering processes. With the Internet and eDrawings, engineers could work from home as well as at the office. The many reviews across multiple organizations and with contractors were accelerated through use of eDrawings and Bluebeam Pushbutton PDF. Digital signatures sped up approvals, and e-mail proved its worth as an efficiency generator. There was no room for compromise of quality control, and taking the paperless approach helped project engineers ensure that the robotic arms would perform as designed and not need a trip back to the drawing board. Considering the time it takes to travel the 100 million miles back to Earth, that's a return trip no engineer wants to be responsible for.
From University to the Universe
From University to the Universe

*Animation by Daniel Maas, Maas Digital LLC ( www.maasdigital.com) © 2002 Cornell University. All rights reserved. This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the United States Government under Prime Contract # NAS7-1407 between the California Institute of Technology and NASA. Copyright and other rights in the design drawings of the Mars Exploration Rover are held by the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL). Use of the MER design has been provided to Cornell courtesy of NASA, JPL, and Caltech.

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