Putting Physics into Human Modeling

DN Staff

May 25, 2011

8 Min Read
Putting Physics into Human Modeling

There areavatars and then there is Santos.

Thanks to the broad availabilityof digital human modeling software, avatars are playing a more prominent rolein evaluating the manufacturing feasibility and safety issues surrounding bothproduct designs and assembly line ergonomics, mitigating the need for costlyphysical prototypes. Yet while mostcurrently available avatars are digital representations of the static humanform, the University of Iowa'sCollege of Engineering's Center for Computer-Aided Design is takingthe concept of human modeling a step further with Santos, an avatar that is ahigh fidelity, biomechanically accurate model of a person, including thephysics of bone and muscle.

The combination of thebiomechanical musculoskeletal model along with predicative dynamics technologymeans Santos just doesn't just mimic biomechanical motions - the avatar isbeing designed to predict motion and to react to movements on its own. Santosdoesn't just sit in the cockpit of a tank or move a piece of equipment fromPoint A to Point B on the factory floor so engineers can evaluate reach andother ergonomic factors. Instead, thedigital avatar's physics-based approach can deliver feedback on how a certaintype of task or combination of movements will impact a human's level offatigue, speed, strength and torque over a period of time.

"We're really trying to understandhow a human behaves from a biomechanical point of view - why they take thisparticular motion or posture, and can a person really complete this task,"explains Karim Abdel-Malek Ph.D., professor at the University of Iowa's Dept.of Biomedical Engineering, director of the Center for Computer-Aided Design anddirector of the U.S. Army's Virtual Solider Research (VSR) program, thebirthplace of Santos, which is funded in part by the U.S. military. "Any timeyou're carrying a box from the ground up or swinging an engine - anything to dowith motion and dynamics - there are moments of inertia involved that are notaccounted for if you're just doing static analysis (of human modeling). The newthing is physics, which adds a real-world element of reality to it."

Santos Lightens Soldiers' Loads

TheSantos project got its start in 2004 at the University of Iowa and through theyears has received a variety of funding from partners, including several of themajor automotive manufacturers, among them, Ford and General Motors,in addition to other Fortune companies like Caterpillar to its mostprominent proponent - the U.S. military. This April, in fact, the VSR team wasawarded a five-year contract valued at up to $8.6 million from the U.S. Navyfor Santos' work related to a project aimed at helping military personnel carrylighter loads into combat. The project, formally known as "EnhancedTechnologies for Optimization of Warfighter Load" (ETOWL), is being conductedfor use in both the Navy and Marines, using Santos to simulate the effect ofequipment loads on military personnel from the standpoint of mobility andphysical stress without having to place real human fighters in the field. Amongthe project's deliverables: A set of computational modeling tools along witheasy-to-use planning tools that leverage the models to enable small-unitleaders to evaluate the trade-offs of different equipment profiles across asquad for better decision making.

Given the fact that the military, just likemainstream business, is dealing with budget shortfalls, virtual prototyping andavatars like Santos are key to designing optimal gear without adding millionsof dollars in costs or years of prototyping time to the development cycle. "Thevery top generals have identified modeling and simulation as the key componentthat will save their design cycles cost and time," says Abdel-Malek.

Depending on the project, thedifferent military branches will be able to outfit Santos with different gear,a war-time backpack, for example, and test such factors as how carrying thepack reduces a soldier's mobility or what kind of physical stress is created bycarrying the load for an extended period of time. Traditionally, the militaryhas done this kind of testing with physical prototypes of proposed equipment onreal-world soldiers, oftentimes, in the field.

"It takes a whole team of peopleto make decisions on this stuff and before they make any kind of decision, theytest the gear on different types of bodies," Abdel-Malek says. "It takesforever to do that and it's difficult to make design changes and then go backand retest. With virtual prototyping, we give them a tool that saves them anincredible amount of time. And by predicting motion, they don't have to bringhumans in."

Santos at Work

Inanticipation of similar needs in the corporate market, the VSR university teamin 2008 spun off Santos HumanInc., a company charged with bringinga commercial version of the digital human modeling software to the commercialmarket. Honda, one of Santos Human's corporate partners and a beta tester ofthe technology, currently employs digital human modeling software as part ofits V6 implementation of Dassault Systemes'CATIA 3D CAD and DELMIA digital manufacturing software. Despite the utility ofthese programs, the physics-based Santos will up the ante in terms ofevaluating fatigue factors or determining if a bend or reach is too much over aperiod of time during an employee shift, according to Bryan Beeney, engineeringcoordinator at Honda of America's East Liberty plant.

"The physics-based approach willshow a reaction as a human body does," he says. So, for example, if you putweight on the body, Santos can display what the human body will do toaccommodate the additional weight - perhaps spread out the feet to find balanceor lock in the hips to hold up the weight. "With a lot of these programs, youcan load 80 pounds on an avatar and nothing changes," he explains. "The data inthe background changes, but visually, the avatar is static."

Ford, another Santos partner, has had greatsuccess with reducing factory floor injuries by employing traditional humanmodeling programs, including Jackfrom Siemens PLM Software. Today, digital Jack or Jill avatars assemblevehicles in the virtual world while a team evaluates manufacturing feasibilityand assembly sequence, all well before any physical parts are produced or toolingor workstations configured. While this approach has allowed Ford to reduceergonomic issues related to its assembly operations far earlier in the R&Dprocess when it is far less costly to reconfigure designs, there is evengreater opportunity with Santos, according to Allison Stephens, Ford's globaltechnical leader in Assembly Ergonomics. Specifically, Santos will allow Fordto evaluate the long-term effects on tissue breakdown as it relates torepetitive tasks on the factory floor over the long term, which as Stephenssays, takes things to a whole new level.

"The model is smart enough,because it's physics-based, to calculate how much muscular force is needed toclimb into a car, hold up an instrument panel or reach over to the center of avehicle with a power tool to make something secure," she explains. "This is notabout comfort, but rather more about can I expect someone to do that once aminute without going to the point of tissue damage or muscular fatigue."

In the days prior to any kind ofsimulation, Stephens' team would average around 300 design changes per vehicledue to ergonomic issues related to factory floor operations, costing as much as$45,000 per change because they were caught and made far into the design cycle.Static simulations through the use of Siemens' Jack have helped Ford reducethat number by 90 percent, but Santos can help push it even further. "Eventhough we're down to only 30 issues (per vehicle), we're still getting injurieson the plant floor because that requires more complex motion evaluation,"Stephens explains. Long term, she hopes to keep Siemens' Jack on hand forstatic hand clearance and reach evaluations while leveraging Santos to do morecomplex and full simulations to understand the cumulative impact on autoworkers.

While Stephens is hopeful aboutSantos' promise, she admits there are still nagging technical hiccups thatprevent the software from being exploited to its full potential. Abdel-Malek,acknowledging the shortcomings, says we're likely to see significant progresswithin the year that will ready Santos for a prime-time appearance.

"Theenvironment is so well-prepared now (for this kind of technology) with all ofthe understanding of avatars, gaming and Hollywood," he says. "There's been anincredible boost in terms of understanding what it is and how it can help."

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