Simulators Focus on Simplicity, Safety

This year the members of the Robotic Industries Association (RIA) will spend time looking back on the association’s first 30 years. Discussions will be nostalgic, as the industry remembers the UNIMATE, the first industrial robot installed in a New Jersey automobile plant; discussions will also be proud, as members realize how robots have transformed modern manufacturing.

The makers of simulation software can also take pride in their efforts. As this article will explore, the development of robot simulators has contributed directly to the modern success of robots in manufacturing, with simulator development mirroring the advance of ‘real’ robots. ‘‘Simulators have been around for a long time,’‘ recalls Greg Webb, Marketing Manager of PC Software at Motoman Inc. (West Carrollton, Ohio). ‘‘At first, they were too expensive. Then, as robot hardware use increased, simulators became more affordable, but there was still an entry barrier – and that was education.’‘ Today, Webb continued, application layers designed for specific manufacturing tasks and other advances are making robots safer and simulators more intuitive for users that know more about their product and process than they know about programming the robot that builds it.

Simulators Increase Safety
Simulators provide an intuitive, efficient 3D-modeling environment that directly translates to more efficient robot control and programming, but for every simulator, safety is big part of its raison d’etre. ‘‘Simulation plays a huge role in safety as far as the overall design concept,’‘ noted J.J. Shields Area Manager Americas-software Products at ABB Inc. (Auburn Hills, Michigan). ‘‘Programming a robot in a virtual environment is a lot safer than [having] a guy with a teach pendant [programming] in a factory environment [fraught] with noise and distractions galore. In the old days, when we used 2D simulators to program the robot, it was difficult to identify collisions, near misses, etc.’‘ With ABB’s simulator, Shield’s explained, ‘‘…you’re able to identify those potential hazards and address them in the design phase.’‘

The inclusion of soft robot controllers, or Realistic Robot Simulators (RRS), in simulators and complete 3D models of human operators is also increasing the safety and efficiency of programming. ‘‘Our simulation package presents a virtual environment that mirrors the teach pendant that you would use to program the robot on the floor,’‘ explained Gordie Geheb, a Director in Product Development at FANUC Robotics America, Inc. (Rochester Hills, Michigan). ‘‘The virtual robot controller uses the exact same code base as the robot controller on the plant floor, so you program it the same and you can expect it to operate the same.’‘

Another simulator-based safety improvement comes from the recent inclusion of very accurate ergo-models, including human operators, into the virtual environment. ‘‘The ergo-models have become much more accurate in the past year,’‘ explained Jean Pierre Rasaiah, Engineering Group Leader for Simulation at Applied Manufacturing Technologies, Inc. (Orion, Michigan). ‘‘If you have a robot-person interaction you should simulate them together in the same simulation model.  If you do not, the whole station cycle-time may be inaccurate.  You may have a problem where the robot is waiting on the operator, which you will not see until production, where changes are costly.  We did not simulate people in the past because the models were not accurate. The new ergo models play into that.’‘

Simulator suppliers have also included ‘‘virtual’‘ hard stops into the programs to aid compliance with RIA ‘‘robot gone wild’‘ safety standards that require 18-inches beyond the fullest reach of the robot, which can be limited by the inclusion of hard stops on the robot. Some simulators include the actual light curtain as well as the mechanical frame. ‘‘Sensors and light screen posts were there in the geometry [in past years], but not the light screen itself,’‘ noted Applied Manufacturing Technologies’ Rasaiah. ‘‘Most simulators did not know if you were breaking the light screen beam. In the past, most simulators would only add the light screen geometry.’‘

Some simulators are also adding cables to the available 3D models in the program so that robot dress, wear concerns and possible safety issues can be determined within the simulator environment. ‘‘If you have a welding gun, and cable that runs between the welding gun and a Y-feeder, we know where the cable will end up in any given robot location,’‘ said Rainer Uhlig, Vice President of Market Development for Welding and Cutting Applications at ABB Inc.

In truth, simulator systems have reached a level where nearly any 3D model from a CAD program (step format, Initial Graphics Exchange Specification [IGES] or other format) can be imported and movement rules assigned to it for simulation within the virtual work cell. ‘‘There’s a lot more 3D-CAD data available today, which makes it easier to simulate a cell that’s full-featured,’‘ said Webb. ‘‘Not only do you pull in the part, but also fixture data, clamps, etc.’‘

Making the Efficient More so
The expanding body of 3D models available to simulators is improving efficiency as well as safety. Although achieving a 100-percent perfect virtual program that acts exactly as it will on a shop floor is difficult, Geheb added, completing 80 percent of the programming in a simulator saves companies considerable time and money. ‘‘In a body shop, for instance, the press outputs change based on the aging of the dies. So those guys are always touching [robot programs] up, but if you can pull the initial teach [programming the robot] in a simulator, you can save a lot of effort and cycle time.’‘

‘‘Using calibration software in conjunction with simulation software, we can achieve 98-99% accuracy in creating off-line programs that require little or no touch-up,’‘ says Webb.  ‘‘This capability can save millions of dollars a year of programming time that would otherwise cause lost production time for some high-volume customers.’‘

In their competition for the best simulator, many robot companies are including more application layers and calibration efforts designed to simplify the simulation/programming process and speed integration and checking of the robot program on the plant floor. ‘‘We’ve developed a line of simulation products that are structured around our robot products,’‘ said FANUC Robotics America’s Geheb. ‘‘We have a tool for the general handling market, paint, arc welding, so on and so forth...’‘ These premodeled cells for specific robot tasks, also referred to as application layers running above the simulator program, help designers that do not have extensive robot programming experience.

After simulation, easy to use calibration tools are also helping to close the gap between the perfect world of the simulator and the less-than-perfect world of the manufacturing floor. ‘‘Calibration is something that has been missing the past with simulators,’‘ noted Uhlig. ‘‘You try to build to your blueprint, but you still have to calibrate the individual components within the cell to the virtual environment. We’ve developed automated routines that key on tooling balls [part fixturing calibration points] within the cell and automatically adjust the robot program to match the locations in the real world.’‘

Calibration routines and application layers are just a few of the ways that robot and simulator vendors are making programs easier to use by hiding the math behind intuitive interfaces. Another important design consideration in light of discussions about next-generation software distribution models includes the use of XML interfaces. ‘‘XML is an open standard that has evolved very quickly,’‘ explained Motoman’s Webb. ‘‘It’s a mark-up language similar to HTML, but they took out the display mechanisms. XML is purely for data and it’s 100 percent definable.’‘

According to Webb, simulators that move to XML can be assured of a long-term development platform that eases communication pressure points between software programs running PLCs, robots, simulators, part libraries and more. ‘‘We have a product under development where we use XML to transform G codes, PLC’s native language into equivalent robot commands. Inside the XML exchange file, I can map a G02 circular CNC motion into a Motoman robot circular motion command with the correct velocity. The CNC market has been open for a long time and that openness has fostered the growth of a plethora of third-party CAD/CAM-programming tools. Robots, on the other hand, have remained proprietary and largely closed to that market.   By converting standard G codes to XML, we can immediately get information into our robot language from a variety of sources.

And that’s only the tip of the iceberg,’‘ Webb continued. ‘‘XML is the core of the Simple Object Access Protocol (SOAP), which is the glue that ties together different software applications. In the future, if I write a software application, I can use a [program] object on a server in Italy, and another in Seattle. I can rent that capability and tie them together with XML. And these objects don’t care whether it’s a UNIX or PC box, so it’s really taken a lot of the hardware-specific stuff out of the way.’‘

As barriers break down between software elements, simulators will continue to add to the safety and efficiency offered by robotic manufacturing. Program upgrades will include more premodeled work cells for specific application types as well as improvements to RIA and ANSI safety standards, as they evolve. Almost as important as safety are the advantages in efficiency offered by robot simulators. ‘‘The integration of simulators with the CAD programs has really simplified the set up process, especially for companies that would normally have to teach hundreds of parts. With a simulator, you can create all your programs offline and quickly upload them to the robot controller,’‘ concludes Geheb.