48 september/october 2011 www.fluidpowerjournal.com | www.ifps.org

AssociAtionnews CCEFP | ThE CEnTEr For ComPaCT and EFFiCiEnT Fluid PowEr

We humans make mistakes, and human error is inevitable. In fact, up to 90% of all accidents in the workplace have human errors as a cause. However, solutions to those problems are often technologically focused. It is important to understand that any system where human operators interact with the machines will have some human factors issues. Simply put, human factors, also known as ergonomics, studies how people interact with their environment and the goal of human factors is to provide efficient, safe, and comfortable equipment and work environments. Unfortunately, many system designers don’t think the role of human factors in fluid power systems is a very important one. Consequently, much emphasis has been placed on improving machine performance and very little has been given to human operators. The truth is no matter how wonderful the system may be, if human opera-tors are uncomfortable, or having trouble using it, you will not achieve the optimal system performance. More importantly, systems that rely on perfect human per-formance are fatally flawed.

Human operators have limited physical and cog-nitive capabilities, and these limitations will have an impact on the effectiveness of a fluid power system. The technologically focused system design solution often fails to fully consider user capabilities and thus cannot achieve the full potential that the systems are designed for. To overcome this problem, human factors needs to be considered. In CCEFP, Project 3A3 (human performance modeling and user center designed) is focused on human factors research.

One of the common problems of system design is that usability of the system is only considered when the system is developed, and thus many system issues are not functionality problems but rather usability concerns. The problem with this approach is that fixing usability issues at this stage is often costly and not very effective. The more effective approach is the User Centered Design (UCD) philosophy. The idea

is to place user needs and interests as early as possible into the design process. UCD is an iterative process, which includes collecting user needs, creating user profile, developing usability goals, performing task analysis, prototyping, usability testing, and imple-mentation. Our research adopts a novel approach that integrates personal design and information sent to UCD. The effective use of the UCD approach can ultimately save companies money because there will be less maintenance and training-related expenses.

Another important human factors issue is human performance. Modeling human operator performance is important because it helps predict how operators

will perform given a new or revised system and can be cost effective before expensive prototypes or mockups are developed. Dr. Khaliah Hughes, who graduated in May, developed an integrated framework that combines the physical and cognitive aspect of human performance modeling and applied it to the excavator test bed using simulation tools such as Micro Saint and Jack. Her dissertation titled “Integration of Cognitive and Physical Factors to Model Human Performance in Fluid Power Systems” received the 2011 North Carolina A&T State University best dissertation award.

With rapid development of fluid power technol-ogy, there is a great opportunity for the fluid power industry to implement human factors and ergonom-ics initiatives that will provide them a positive return on investment (ROI).

* Reprinted with permission from the Center for Com-pact and Efficient Fluid Power (CCEFP) newsletter, Issue 15, Spring 2011

CCEFP REsEaRChBy Prof. steven Jiang, Project 3A.3, north carolina A&t state University

Human Factors in Fluid Power systems:

Is It Necessary?

Is it necessary to study human factors in fluid power systems? This is the question I am asked most often since the inception of CCEFP. My short answer is: Yes, because to err is human.

www.ifps.org | www.fluidpowerjournal.com september/october 2011 49

ThE CEnTEr For ComPaCT and EFFiCiEnT Fluid | CCEFP AssociAtionnews

suPPorting model-Based systems engineering

with SysMLThe behavior diagrams include the use-case

diagram, activity diagram, sequence diagram, and state machine diagram. A use-case diagram provides a high-level description of functionality that is achieved through interaction among systems or system parts. The activity diagram represents the flow of data and control between activities. A sequence diagram represents the interaction between collaborating parts of a system. The state machine diagram describes the state transitions and actions that a system or its parts perform in response to events.

SysML includes modeling constructs to represent text-based requirements and relate them to other model elements. The requirements diagram captures requirements hierarchies and requirements derivation. The satisfy and verify relationships allow a modeler to relate a requirement to a model element that satisfies or verifies the requirements. The requirement diagram provides a bridge between the typical requirements management tools and the system models.

The parametric diagram represents constraints on system property values such as performance, reli-ability, and mass properties, and serves as a means to integrate the specification and design models with engineering analysis models.

SysML also includes an allocation relationship to represent various types of allocation, including alloca-tion of functions to components, logical to physical components, and software to hardware.

SysML models are being used in several research projects and test-beds within the CCEFP. For instance, in the rescue robot test-bed, the require-ments are broken down into detailed requirements and corresponding test cases as is illustrated in Fig. 1. The use of SysML for requirements capture, system descriptive models, analysis models, and the relation-ships between these different system views is applied extensively in Project 2E on Model-Based Systems Engineering for Efficient Fluid Power.

To learn more about the Systems Modeling Lan-guage, visit www.omgsysml.org where you can find several introductory tutorials and papers. The SysML movement is quickly gaining momentum with several major software vendors supporting the standard (for a list of vendors consult the site above).

Article compiled by Chris Paredis with contributions from Thomas Johnson, Roger Burkhart, Sandy Friedenthal, and the OMG SysML Standardization Committee.

* Reprinted with permission from the Center for Compact and Efficient Fluid Power (CCEFP) newsletter, Issue 15, Spring 2011

By Prof. chris Paredis, Project 2E, Georgia institute of technology

contemporary systems engineering proj-ects encompass many different domains of knowledge, exist at increasingly large scales, and consist of multiple subsys-

tems and components. With the adoption of electro-hydraulics, the complexity of fluid power systems has also increased significantly, requiring careful integra-tion between fluid power, electrical, mechanical and controls, hardware and software. Studies generally show that problems associated with the development of such systems have often more to do with the orga-nization and management of complexity than with the direct technological concerns that affect individ-ual subsystems and specific physical science areas. If system designers do not fully understand the com-plexity and emergent behavior of the system under development, they might overlook important design details and relationships. Such mistakes can compro-mise stakeholder objectives and lead to costly design iterations or system failures.

To overcome such problems in the context of fluid power systems, the CCEFP is adopting a Model-Based Systems Engineering (MBSE) approach. Specifically, a project on “Model-Based Systems Engineering for Efficient Fluid Power” started in June, and Prof. Rob Cloutier from Stevens Institute of Technology will join the Scientific Advisory Board to provide feedback on systems engineering research within the Center. In addition, through the activities of the Systems Engineering Task Force, concepts of MSBE will be infused in the test-beds and research projects within the Center.

The MBSE approach pursued within the Center builds on the Systems Modeling Language (OMG SysML™) developed by the Object Management Group. SysML is a general-purpose information modeling language that allows system designers to create and manage models of physical systems using well-defined, visual constructs. The knowledge cap-tured in a SysML model is intended to support the specification, analysis, design, verification, and vali-dation of a complex system.

The specification of the SysML language reuses a sub-set of UML 2.0 and extends it where necessary. Adopted in November 1997, the Unified Modeling Language is a visual language for specifying, constructing, and docu-menting the artifacts of software, business models, and other applicable systems. It is a general-purpose model-ing language that can be used with all major object and component methods. The language is commonly used during the development of large-scale, complex software for various domains and implementation platforms.

The SysML profile was developed to extend UML for increased support of systems engineering projects. The <<block>> is the basic unit of structure in Sys-ML and can be used to represent hardware, software, facilities, personnel, or any other system element. The system structure is represented by block defini-tion diagrams and internal block diagrams. A block definition diagram describes the system hierarchy and system/component classifications. The internal block diagram describes the internal structure of a system in terms of its parts, ports, and connectors. The package diagram is used to organize the model.

50 september/october 2011 www.fluidpowerjournal.com | www.ifps.org

AssociAtionnews

The CCEFP’s Education and Outreach Program extended a warm welcome to the participants of the 2011 Fluid Power Scholars Program and the 2011 Research Experiences for Undergraduates Program.

The Fluid Power Scholars (FPS) Program is a collaborative effort between the CCEFP and corporate members of the Center. This program identifies and con-nects outstanding undergraduate engineering students with the fluid power indus-try for the purpose of training the next generation of fluid power leaders by offering a three-day fluid power boot-camp followed by a summer-long internship within the company. 2011 is the program’s second year, and just like the first year, eight scholars have been named.

The Center thanks the internship host companies for their support: Case New Holland, Parker Hannifin Corporation, Sun Hydraulics, HUSCO International, Caterpillar, John Deere, and Deltrol Fluid Products.

The Research Experiences for Undergraduates (REU) Program’s goal is to pro-vide undergraduate science and engineering students with a summer experience in a university research lab. An objective of the program is to increase the number of top students applying to graduate school in science and engineering areas. The Cen-

ter welcomes 18 REU stu-dents to the 2011 program. For the very first time, the program hosted 11 REU students at the University of Minnesota for a Fluid Power Boot-Camp, lead by CCEFP graduate students, to fully prepare REUs in fluid power technology for their summer research experience.

CCEFP | ThE CEnTEr For ComPaCT and EFFiCiEnT Fluid PowEr

Fluid PowER sCholaRs and REu PRogRam undERway FoR 2011By Alyssa Burger, Outreach Director, University of Minnesota

The CCEFP Industrial Advisory Board (IAB) held a meeting at the Georgia Institute of Technology on May 4 and 5. Eighteen IAB members met with a total of eight principal investigators (PIs) from Georgia Tech, Vanderbilt, and North Caro-lina A&T State to get updates on their research and discuss future research poten-tial. In addition, the IAB toured the Center-related lab facilities at Georgia Tech.

The IAB decided in late 2010 to hold three or four of its meetings each year at CCEFP member universities. The plan is to visit all seven universities on a rotating basis. The meetings are done on a regional basis, so PIs from member universities within driving distance of the host university are also invited to attend and meet with the IAB. The meeting at Georgia Tech was the second on-site IAB meeting. The first on-site meeting was held at the University of Minnesota in November 2010. The next on-site meeting is planned for Purdue University in September.

The entire first day of the meeting was focused on the IAB meeting with PIs and touring the lab facilities. The goal was to have a dialogue between the IAB and PIs—as opposed to a lecture—and this was largely accomplished. That eve-ning, CCEFP hosted a dinner for the IAB, PIs, students, and staff that provided an opportunity for networking and individual discussions. The majority of the second day was focused on IAB-related topics and included a presentation by CCEFP Director Kim Stelson on the sustainability of the Center. The new industrial liaison, Dewey Tinderholm, was introduced to the group.

iaB holds sECond “on CamPus” mEEting; gt hostsBy Brad Bohlmann, CCEFP Sustainability Director, University of Minnesota