ROBOTIC SIMULATION W H I T E P A P E R KUKA ROBOTICS CORPORATION KEY DRIVE CLINTON TOWNSHIP, MI USE.KUKA

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1 KUKA ROBOTICS CORPORATION ROBOTIC SIMULATION Revision KEY DRIVE CLINTON TOWNSHIP, MI USE.KUKA W H I T E P A P E R

2 ROBOTIC SIMULATION Contributed by Pat Duda KUKA Robotics Corporation Robotics simulation is a powerful tool that can be used to validate many automation processes. This white paper will discuss the value that robotic simulation packages offer. What is Simulation? There are two main kinds of simulation exist, discrete event simulation and continuous system simulation. Discrete event simulation breaks a system down into individual events that have a specific start time and duration. It tracks the sequencing and interaction of these events to determine the overall behavior of a complex system of real world objects. This technique usually focuses on modeling the control logic for routing of material and interaction of equipment. It also typically applies statistics to the system to simulate things like equipment breakdown or mixtures of different product models. Discrete event simulation is an excellent tool to determine the total system throughput for a whole factory. Continuous system simulation applies numerical techniques to calculate and predict the detailed behavior of a physical system. These simulations typically apply numerical integration, differential equation solvers, or other mathematical approaches. Often, electrical circuits, control systems, or similar mechanical system are simulated this way. Specific applications like thermal dynamics, aerodynamics, aircraft control systems, or automobile crashes are commonly simulated with continuous system simulation. Robotic simulation is a specialized form of simulation that is optimized for solving the problem of designing & programming robotic systems. The simulation of predicted robot motion and timing uses the continuous system techniques but the 3D visualization and simulation of other system equipment use discrete event simulation methods. Robotic simulation is actually a hybrid technique that combines discrete event and continuous system simulation. Why use Robotic Simulation? Robotic simulation tools are ideal for the design of robotic automation systems and provide key advantages over mechanical design CAD systems. The use of robotic simulation facilitates higher quality designs in an automation system. Mechanical designs and control strategies are also validated during the simulation process. Visualization capabilities integral to this technology help communicate concepts and designs to all the stakeholders so simultaneous team engineering becomes a reality. The efficiency of the tool enables engineers to check more alternatives and create a more optimal design. Without robotic simulation, a design team rarely does a system level review to see how all the pieces of an automation system work together. Faster design development and programming can be attained with this simulation technology. Allowing an operator to work in a virtual environment promotes faster work methods that would be considered high risk in the real world. Specific software tools designed to accelerate the 2

3 development process are also utilized. Actual robot programs can be generated from the simulation study very quickly and accurately. Build and installation of the robotic system usually happens faster with lower costs. Historically this is the time when most design errors are discovered after significant cost had been expended on design and manufacture. The typical response to these errors was a quick, high pressure design change without adequate consideration. Offline generated programs further reduce the build time effort by avoiding manual robot jogging for path teaching. Programs are simply loaded, verified, and if necessary touched-up with small adjustments. The History of Robotic Simulation Twenty years ago, the first commercial robotic simulation software emerged to help solve the growing complexity of designing and programming robotic systems. Deneb Robotics (now Dassault/Delmia) and Tecnomatix Technologies (now UGS/Tecnomatix) introduced products to visualize and test proposed automation designs utilizing robots. These two companies are still the leading suppliers of robot simulation technology. Since maturation of robotic simulation in the mid 1990 s, market leaders have developed this technology into an expensive comprehensive enterprise solution. The capabilities of simulation were extended into Product Lifecycle Management (PLM). Now the tools have the capabilities to manage product designs, and the associated complicated manufacturing processes, from concept thru production. With this added capability comes a complexity that is only useful for the largest OEM companies. The cost of these products is also targeted to the budget of larger companies, beyond the reach of many small and medium size businesses. Essential Capabilities of Robotic Simulation During the maturation of robot simulation nine essential capabilities of simulation packages emerged. Visualization. The 3-D solid representation of the robot cell layout, tooling, and robot reach has become an indispensable tool for communicating design issues among the design team and customers. Simultaneous engineering of product, tooling, and robot process is more practical because of this ability for team members see the conditions affecting design. Collision detection. The ability of the simulation software to calculate where collisions will occur in the simulated process is essential for making the process suitable for use in the real world. It also enables the engineer to detect design problems early and test more alternative solutions. Reachability checks. Checking reach in a virtual environment is far quicker than working with a real robot. Early design reach checks can be performed without regard to the path the robot uses to get to key locations like pick or drop points. The operator simply jumps the robot to the location to be checked. The virtual environment where there is no risk of damaging equipment also enables the operator to check reach conditions with small clearances to collisions. Some higher end analysis tools will evaluate reach automatically for an entire process path. Path creation. Robot paths can be created more quickly in the simulation environment since the operator has no worry about safety issues like damaging equipment or moving the robot fast enough to hurt someone. Simulation software often contains tools to generate portions of paths automatically. For example, a sealant application path could be generated based on CAD data for the part the sealant is applied to. 3

4 Process helpers & guidance. The software can contain features that simplify the programming of complex processes. Specialized software tools automate or simplify the most complex tasks for creating designs or paths for an application. For example, a painting process helper may set paint flow parameters or adjust path-to-path spacing by asking the operator simple questions about the desired result. Accurate motion & cycle time estimation. Early simulation systems attempted to create general robot control algorithms within the simulation software but actual robot control designs often had specialized technology that the general algorithms could not handle. The simulation algorithms could never predict cycle time & motion very accurately. In response, the simulation software vendors and robot manufacturers combined efforts to create the Realistic Robot Simulation (RRS) specification (see This communication specification enabled each robot vendor to create a black box piece of software that contained the motion algorithms to accurately simulate their robot. This black box passes the motion and timing information to the simulation software. More recently, a next generation specification was created, called RRS2, which is much more comprehensive. RRS2 adds to the motion predictions to include input/output and full language support for the robot. RRS & RRS2 typically create motion time and path predictions that are 97% accurate or better. Representation of other equipment. Robots never work alone. They must utilize and interface with other pieces of equipment. Even simple applications require an end-effector of some sort. Other tools or machines that are part of the automation process must also be simulated. Representing the motion of these other machines can be important for collision detection and cycle time prediction. Simulating the communication interface to these other pieces of equipment is also necessary for creating a properly working process. Offline Programming. This is the process of transferring the simulated paths to real world robot programs. Proving a process in simulation has huge value alone, but the ability to take a robot program from simulation to the real world increases the value of simulation even more. Customization. Robots are very flexible tools. Operators often need to solve complex or repetitive problems. The ability to integrate custom software into the simulation environment to address these problems is a commonly provided feature. Robotic Simulation Review: KUKA Sim KUKA Sim is a powerful software that fills the need for a traditional simulation tool. It contains the essential capabilities of a robotic simulation system as discussed above. Since it has been designed as a second generation tool, it has many advantages over the existing simulation software offered by Delmia and UGS. 4

5 Figure 1 KUKA Sim User Interface An advanced user interface makes the software extremely easy to use. Components are loaded and manipulated by drag-n-drop handles. Sketches can be created quickly by dragging components to the layout and sliding them around. Exact values can still be assigned with numeric input as well. Objects can be moved freely in a plane or axis arrows can be grabbed to move along a single direction. Orientation can be set with a rotation sphere that also operates with the same drag-n-drop methods. Robot programs are created with simple drag-n-drop operations. Program points can be adjusted by quickly sliding them around. Reachability of the robot can be verified with a click of the mouse on each point. 5

6 Quick and easy to use and learn Easy to use: Layout Plug and Play interfaces Intuitive drag and drop handling Snap functionality Easy to learn: Jog the robot by dragging and turning either the tool frame or one of the axis directly Easy jogging in different coordinate systems (joint jog, tool frame) Windows look and feel 6

7 Figure 2 KUKA Sim Drag-n-Drop, Plug-n-Play Components in the simulation can be snapped together with the plug-n-play capability. For example, mounting an end-effector on a robot is a single step operation. When the end-effector is dragged close to the mounting face for a robot, it automatically snaps into place with the correct orientation, attaches to the end of the robot, and can connect input/output signals for control. Older simulation systems required 3 to 4 steps to perform the same function as a simple plug-nplay drag in KUKA Sim. A key feature of KUKA Sim is the component. Each piece of simulated equipment can be modeled as a fully functional object, equivalent to its real world counterpart. Existing simulation systems allow the geometry and movement to be modeled. KUKA Sim components can also contain mechanical interfaces, control logic, control interfaces, and even product documentation. Parametric modeling can also be done, so a whole class of equipment sizes or options can be modeled only once. The software uses a model and reuse strategy so it is only necessary to create a component once and then it is reused from the library. The default component library includes KUKA robot models, conveyors, end effectors, fencing, and much other common industrial equipment. Pre-built component libraries can be stored with the software, on a server, or can even be accessed over the internet. Accessing the data over the internet is a viable option since the data format is designed to be very lightweight. The small data size is ideal for collaboration via sharing data over the internet or . This compact data format is used for the component storage and also the layout data. A sensor is a very valuable feature. KUKA Sim has the built-in ability to check for the presence of a part, basically like a proximity switch. A sensor can be connected to input/output to other components or it can cause some behavior within a component. This software also has a full discrete event simulation engine integrated inside. Material flow is easy to manage since quantities of any part are automatically generated with a simple creator component. Conveyor and transfer components are included in the standard component library. It is simple to simulate a robotic process as well as the throughput of a cell or entire factory. Cost is a factor that every company is concerned with. KUKA Sim helps to lower cost by rightsizing the capability to the customer needs. It is offered in 4 levels of functionality: Pro, Tech, Layout, and Viewer. The Pro version contains all options including the ability to create new components, write custom application extensions, perform RRS2 time estimates, and generate offline programs. Layout is an excellent tool for sales or management use. It offers the same simple, intuitive user interface to enable the user to create 3D concept layouts. If a picture is worth 1000 words, a 3D sketch is worth 10,000. Tech adds the functionality of custom technical modules like CamRob to the Layout capability. The Viewer version is available free of charge and is excellent to facilitate communication with customers or other stakeholders during concept or design reviews. 7

8 KUKA Sim Feature Comparison Summary Figure 3 KUKA Sim Features 8