STIHL wanted an automated solution for grinding wear protectors on the bars of chain saws. Arla Foods needed a faster way to pick up and stack pallets full of drink cartons.
BMW was looking for an expert “craftsman” to sew leather covers on the seat backs of its 7 Series vehicles.
In each of these cases, the answer was a KUKA robot. Headquartered in Augsburg, Germany, KUKA has installed more than 60,000 robots since 1977, most of them controlled by the company’s own PC-based systems. The robots are working in virtually every manufacturing setting and handle payloads from 3 kg to 570 kg.Increasingly, too, companies are buying multiple robots, which are programmed to work together in manufacturing cells, linked by Ethernet-based communications.
To learn more about robotics and its role as perhaps the optimum proving ground for new mechatronics concepts, Design News interviewed Bill Kneifel, an engineering manager at KUKA’s North American headquarters in Clinton Township, MI. Kneifel heads the application engineering team that supports KUKA installations throughout the U.S. and Canada. In addition to his management duties, Kneifel teaches a graduate-level course in mechatronics at Lawrence Technological University in Southfield, MI.
Why is robotics such a prime example of a mechatronics application?
Bill Kneifel: Mechatronics involves taking a systems-based approach to the design of interdisciplinary systems, which include computer software and electrical and mechanical subsystems that all work together. Robots are a prime example of machines requiring a cross-functional interdisciplinary design approach. The software in a robot controller implements the motion control system, which is based on kinematics and dynamics models of the electro-mechanical system being controlled. Hence, mechanics are used in the design of the algorithms in the controller software itself. And, sometimes the mechanical design is constructed in a way that is favorable to the software algorithms. An example is the use of a “spherical wrist” in which all the wrist axes of motion intersect at a common point. This simplifies the solution of the inverse transformation equations used for relating the tool center point path through space to the joint angles needed to achieve this path.
DN: Why is it important to incorporate a mechatronics design approach in developing robots?
BK: I’ve been involved in robot design for more than 25 years, and teams I have been part of have used a mechatronics approach almost from the start, although people didn’t call it mechatronics back then. A robot is a collection of many subsystems that need to work together in a tightly coordinated fashion. Therefore, it is important to design these coordinating subsystems concurrently to ensure compatibility at the interfaces, as well as to satisfy overall system level design requirements and constraints. The design process is typically iterative in nature and normally involves a cross-functional design team. It would be very difficult to first design the mechanical system with no regard to either the electrical system, such as motors and drives, or the software system, and then have to design the electrical system and lastly design the control algorithms and software system. The resulting system performance would likely be compromised, and the overall development time would be longer.
DN: What engineering specialties are represented on your development teams?
BK: A robot design involves quite a number of specialties, including, mechanical configuration analysis, mechanical design of the structure, mechanical design of the gearing, motion algorithms and corresponding software development, servo system design, motor and drive design, controller electrical and sensor interfaces engineering, user interface design, operating system and controller infrastructure software design, and I/O system software and hardware design. Designs often employ components such as motors or drives that are procured from suppliers who specialize in their design and manufacture.These component vendors often interact on a technical basis with the design team.
We also employ project management practices to encourage effective team interactions.Some examples include: project kickoff meetings, careful team review of system requirements and identification of corresponding impacts and/or constraints, architecture design and discussion meetings, and group definition of subsystem interfaces.The development process is iterative, and efficient cross team communications are beneficial to completing the project in a timely fashion.
DN:Can you cite some examples of design, simulation and test tools that are important to your development teams?
BK: Project management tools are used for scope, schedule and resource management. CAD tools are important for the mechanical design. Graphically-based visualization and simulation tools like KUKA Sim Pro are used to plan, program and assess robot applications. Software development also requires a whole suite of tools spanning modeling, code generation, configuration management, and code implementation for specific operating environments, such as VxWorks and Windows. Electrical engineering tools include circuit design, analysis, schematic capture and board layout. Many engineers are familiar with the use of MATLAB and Simulink, which we also use for the analysis and design of motion control and servo systems. All of these tools are especially important when you are designing entirely new systems.
From a mechatronics standpoint, how does KUKA like to work with its customers to integrate your robots into an overall automation design?
BK: KUKA robots are applied in quite a variety of applications ranging from automobile manufacturing to the handling of products for general industry to medical treatment of patients in hospitals to entertainment systems. Because of this wide ranging variety of application processes, KUKA often teams with system partners who specialize in a certain application process area and who integrate the robot into a complete process automation cell or system.This involves bringing together a variety of automation and process control equipment with the robot and developing computer software and hardware to control the overall system. Often, the application software is implemented using the robot controller’s KRL programming language and I/O system, since the robot comes with a lot of embedded capability for controlling peripheral equipment and communicating directly with cell computers. Example interfaces include: use of a field bus such as DeviceNet for controlling I/O for end of arm tooling, and Ethernet for communicating with other computers.
DN:Shifting to your teaching responsibilities, what essential mechatronics design skills are needed most in new engineers?
BK: Historically, it is my experience that mechatronics engineers often start with a servo control background. Still, it is very important for controls engineers to augment their servo design skills with both analytical and experimental dynamics and system modeling skills. Until you have developed an accurate system model, it is hard to design a high performance controller.
I believe that education programs today include more team-based work and interdisciplinary views than in the past. However, there are a variety of interdisciplinary areas that mechatronics design work demands engineers to be familiar with. Mechatronics and robotics programs typically introduce students to the variety of interdisciplinary topics that are involved in a robot design. The engineer may be required to pursue any or all of these topics in more depth to accomplish any given design.
To what extent are engineering schools making progress in teaching students the importance of a mechatronics approach to design?
BK: There are a number of specialty courses, research labs and recently even some degree programs being created to specifically cover the mechatronics approach to the concurrent design of interdisciplinary systems involving software, motion, and electro-mechanical systems. For example, I am presently developing and teaching a course on the design of mechatronic systems/robots in the new Master of Science in Mechatronic Systems Engineering program at Lawrence Technological University in Southfield, MI. The program is hosted by the mechanical engineering department.