Kim Stelson

University of Minnesota - Twin Cities, Mechanical Engineering, Faculty Member

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Kim A. Stelson is College of Engineering Distinguished Professor of mechanical engineering at the University of Minnesota. He is the Founding Director of the NSF Engineering Research Center for Compact and Efficient Fluid Power (CCEFP).

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Papers by Kim Stelson

Heat transfer—a review of 1991 literature

International Journal of Heat and Mass Transfer, Dec 1, 1992

INTRODUCTION THIS REVIEW surveys and characterizes papers comprising various fields of heat trans... more INTRODUCTION THIS REVIEW surveys and characterizes papers comprising various fields of heat transfer that were published in the literature during 1991. It is intended to encompass the English language literature, including English translations of foreign language papers, and also includes many foreign language papers for which English abstracts are available. The literature search was inclusive, however, the great number of publications made selections in some of the review sections necessary. Several conferences during 1991 were devoted to heat transfer or included heat transfer topics in their sessions. They will be briefly discussed in chronological order in this section. The 1991 International Seminar on Heat and Mass Transfer in Porous Media was sponsored by the International Center for Heat and Mass Transfer on 20-24 May at Dubrovnik, Yugoslavia. The majority of the papers are available at the Center in a bound volume. The ASME Turbo Expo-Land, Sea, and Air sponsored by the International Gas Turbine Institute and held on 3-6 June at Orlando, Florida included in its program session on ceramic technology, fii cooling, coatings and composites. Printed papers are available through the ASMB order department. The ACHEMA 91, International Meeting on Chemical Engineering and Biotechnology, connecting with a large exhibition, was held at Fra&mt/Main, Germany on !+-15 June. The Second World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics was organized by its assembly on 23-28 June at Dubrovnik, Yugoslavia in 10 keynote lectures, 7 panel discussions, 25 invited lectures, 209 contributed papers and open forum sessions. Papers are available at Else&r Science Publishing Co. Raymond Viscanta was awarded the first Nusselt-Reynolds Prim. The 26th Thermophysics Conference was organized by the American Institute of Aeronautics and Astronautics on 24-27 June in Honolulu, Hawaii with sessions on spacecraft coatings, solidification and convection, thermal analysis, heat pipes, and hypersonic non equilibrium flow. Conference pmceedings are available and selected papers are published in AIAA journals. 7'7~ 7th International Conference on Numerical Me&oak in Luminar and Turbulent Flow was sponsored by Lockheed Missile and Space Co.

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Point-to-point motion commands that eliminate residual vibration

Several point-to-point motion commands are presented that eliminate residual vibration for a sing... more Several point-to-point motion commands are presented that eliminate residual vibration for a single degree-of-freedom mechanical system. It is shown how any vibrationless motion command of fixed duration can be converted into one of arbitrary duration. Comparisons are made based on force, energy and power

Creep in injection molded starch/synthetic polymer blends

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Dec 1, 2002

Creep in uniaxial extension was measured in starch/synthetic polymer blends. In the first experim... more Creep in uniaxial extension was measured in starch/synthetic polymer blends. In the first experiment, the starch content was kept constant at 70% and the applied stress and temperatures were varied. In a second experiment, the starch content was varied from 0 to 70% at a constant applied stress and varying temperature. The synthetic polymers in the blend were either polybutylene succinate (PBS) or polycaprolactone (PCL), both semi-crystalline biodegradable polyesters. Maleic anhydride-functionalized polyesters (5% by weight) were used to reactively compatibilize starch and the synthetic polymer. The compliance of these blends was found to increase with increasing applied stress and temperature and decrease with increasing starch content. Addition of small amounts of starch was found to significantly inhibit creep. Time Á/temperature superposition was attempted for blends containing 30, 50 and 70% starch. The compliance master curve was successfully obtained for the blends containing 70 and 50% starch, but empirically estimated shift factors did not obey the WLF equation. WLF constants could be calculated based on the empirical shift factors and were in the range obtained for other polymers. The compliance data could be fitted to several empirical models. Excellent fits were obtained for compliance at different stress levels and temperatures.

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New Method to Measure Normal Pressure and Frictional Stresses in the Roll Gap During Cold Rolling

Lapping control for hard disk drive heads

General Design Rules for High-speed, Flexible Mechanisms

General equations for the design of high-speed mechanisms are derived. The equivalent mass and st... more General equations for the design of high-speed mechanisms are derived. The equivalent mass and stiffness of a \u27structure\u27 for each instantaneous position of a mechanism yields input for application of those general design rules. In order to verify these rules, several examples analyzed by FEMAP are used to demonstrate the results

An Efficient Algorithm for Shortest Path in Three Dimensions With Polyhedral Obstacles

Journal of Dynamic Systems Measurement and Control-transactions of The Asme, Sep 1, 1989

An algorithm to find the shortest path between two specified points in three-dimensional space in... more An algorithm to find the shortest path between two specified points in three-dimensional space in the presence of polyhedral obstacles is described. The proposed method iterates for the precise location of the minimum length path on a given sequence of edges on the obstacles. The iteration procedure requires solving a tri-diagonal matrix at each step. Both the computer storage and the number of computations are proportional to n, the number of edges in the sequence. The algorithm is stable and converges for the general case of any set of lines, intersecting, parallel or skew.

Real Time Identification of Workpiece Material Characteristics From Measurements During Brakeforming

Journal of engineering for industry, Feb 1, 1983

A novel method is described to estimate the material characteristics of a sheet being bent in a p... more A novel method is described to estimate the material characteristics of a sheet being bent in a pressbrake from punch force-displacement data. The method is simple enough to be used for real time identification of uncertain sheet characteristics. This procedure can be combined with a model of pressbrake bending to provide real time control of the pressbrake. The setup procedure can be eliminated, and the final angle of the bends can be made insensitive to material property variations. A machine controlled in this manner can be integrated into an unmanned flexible sheet metal manufacturing cell.

Computer Controlled Laser Guided Vehicle for Material Handling

3D CFD numerical analysis of vane dynamic effects on the pressure ripple in a variable displacement vane pump

E3S web of conferences, 2020

A numerical three-dimensional CFD analysis of a variable displacement vane pump has been conducte... more A numerical three-dimensional CFD analysis of a variable displacement vane pump has been conducted, investigating the effects on the pressure ripple caused by the vane detaching from the pressure ring. The volume of the fluid over the vane tip has been re-meshed at every time step as a function of the forces acting on the bottom and the top of each vane. The numerical model has been developed using the commercial tool, Simerics MP+, including turbulence and cavitation models. The validation of the model has been done comparing numerical and experimental data. It has been observed that the detachment of the vane occurs during the transition zones when unwanted pressure spikes are generated by a nonoptimized valve plate design. The prediction of vane detachment is crucial for designing a quieter and more durable pump. Vane collision on the stator ring can be a source of noise producing premature wear of both components. Vane detachment from the stator ring has a large effect on pressure ripple even if the volumetric efficiency is only slightly influenced.

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Academic fluid power research in the USA

International journal of hydromechatronics, 2018

With the formation of the Center for Compact and Efficient Fluid Power (CCEFP) in 2006, there has... more With the formation of the Center for Compact and Efficient Fluid Power (CCEFP) in 2006, there has been a resurgence of academic fluid power research in the USA. The centre's vision is to make fluid power the technology of choice for power generation, transmission, storage, and motion control. To address fluid power's key technical barriers, the CCEFP research strategy supports and coordinates pre-competitive research in three thrust areas: efficiency, compactness and effectiveness, where effectiveness means making fluid power safer, easier to use, leak free and quiet. This paper reviews some of the most important results from the first decade of CCEFP research.

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Finite Element Method for the Analysis and Calibration of a Closed Loop Control Algorithm for Pressbrake Bending

Finite Element Analysis is shown to be a useful tool for the off-line calibration of a method for... more Finite Element Analysis is shown to be a useful tool for the off-line calibration of a method for the real time control of a metal forming process. The identification of the material characteristics of a sheet being bent in a pressbrake is chosen as an example. Finite element analysis is used as a numerical experiment so that the accuracy of the simplified model needed for real time control can be assessed. The results can also suggest ways to improve the algorithm. In this example, the finite element analysis showed that the stress estimates are accurate, but the strain estimates need improvement either by the use of an empirical calibration factor or by the development of a more exact theory.

The Area-Coarea Method for the Estimation of Power-Law Constitutive Parameters

Journal of engineering for industry, Aug 1, 1989

A new method for estimating the power-law constitutive parameters from experimental data is prese... more A new method for estimating the power-law constitutive parameters from experimental data is presented. The algorithm is well suited to real time computation because the integrals employed can be continuously updated with new data. The method requires less computation than least squares fitting and avoids the problem of excessive weight being put on low amplitude data that is present in logarithmic least squares fitting. Because the method employs integrals, it smooths noise in the data. The method can also be extended to linear plus power-law fitting.

Measuring the Losses of Hydrostatic Pumps and Motors: A Critical Review of ISO4409:2007

ISO 4409 is the most important international standard for measuring the efficiency of hydraulic p... more ISO 4409 is the most important international standard for measuring the efficiency of hydraulic pumps and motors, the latest edition being 4409:2007. The standard describes methods for determining the steady-state performance in terms of overall efficiency. It also defines equations for calculating the volumetric efficiency of pumps and motors. The hydro-mechanical efficiency is only defined for motors, not for pumps. This paper analyses the efficiency and losses of pumps and motors in an alternative way. The preference is on loss analysis instead of efficiencies. Especially the effects of the bulk modulus are considered in a different and more inclusive manner. The new methodology results in a higher total loss for motor and a lower total loss for pumps than the current ISO 4409 standard. Furthermore, it results in significant changes of the hydro-mechanical and volumetric losses. The differences between the new methodology and ISO 4409 become larger for high load pressures. The new methodology demands knowledge about the minimum volume of the displacement chamber. The ratio between this volume and the full displacement of a single displacement chamber strongly influences the hydro-mechanical and volumetric losses of the pump or motor. The new methodology is valid for all positive displacement hydrostatic pumps and motors. The volumetric efficiency, as defined in ISO 4409, can still be used as a flow rate factor, but should not be regarded as an energy conversion efficiency. The importance of adopting the proposed methodology is further demonstrated by analyzing and comparing the measurement data about a fixed displacement pump and motor, showing the differences in the loss analysis by means of ISO 4409 and the new equations. The methodology, observations and validation results presented in this paper are significant and can pave the road for improving the current ISO 4409:2007 standard, which would ultimately benefit the industry.

Computer-Aided Process Planning for Turned Parts Using Fundamental and Heuristic Principles

Journal of engineering for industry, Feb 1, 1992

Research on generative computer-aided process planning (CAPP) for turned parts using combined fun... more Research on generative computer-aided process planning (CAPP) for turned parts using combined fundamental and heuristic principles is presented. The rationale for the process planning approach is that many preconditions of machining processes can be expressed as a small number of domain principles. The domain is defined by processes and the part description as features for simple turned parts. The motivation is to detect faulty designs early on in the design process. Preliminary designs defined by features are first evaluated using manufacturability rules in a rule-based expert system, developed in LISP. Manufacturability rules are based on feature properties such as accessibility, stability, and critical material thickness. The rules were acquired from design and manufacturing personnel from industry through interviews. Parts that satisfy the manufacturability checks are used to generate all feasible process plans. A search algorithm selects the “best” process plan from the feasible set. Process plans are generated and subsequently optimized using two distinct sets of feasibility and optimality criteria which may be either fundamental or heuristic in nature. The presently incorporated criteria successfully restrict the set of plans to a small number without missing any apparently feasible process plans. Manufacturability evaluation, feasible process plans, and optimal process plans for actual industrial parts have been obtained and compared.

Measurement of the Interfacial Stresses in Rolling Using the Elastic Deformation of the Roll

Journal of engineering for industry, Nov 1, 1987

A new method to measure the frictional stresses and normal pressure in the roll gap during cold r... more A new method to measure the frictional stresses and normal pressure in the roll gap during cold rolling, and experimental verification of this new method, are presented. The method overcomes many of the shortcomings of pin-type sensors. The elastic deformation of the roll itself is measured with strain gages, and is used to calculate the stresses between the sheet and the roll. Since no modification of the roll is necessary, the deformation process is undisturbed by the measurement. Mechanical isolation of the sensor is unnecessary. The mathematical procedure used to calculate the normal pressure and frictional stresses from the measured strains explicitly acknowledges that these strains are the result of the entire distribution of pressures and shears in the roll gap. An experimental rolling mill was constructed to verify the proposed method. Lead was rolled, and the resulting pressure and frictional stress distributions in the roll gap were measured. Several features of these distributions are in agreement with measurements made by various investigators using other techniques, thereby confirming the usefulness of the new method. Future work is proposed to increase the accuracy with which the roll gap stresses may be measured.

An energy management strategy for a hydraulic hybrid vehicle

ABSTRACT In this study we present a procedure for the design and implementation of a control stra... more ABSTRACT In this study we present a procedure for the design and implementation of a control strategy to optimize energy use within a light weight hydraulic hybrid passenger vehicle. The hydraulic hybrid utilizes a high pressure accumulator for energy storage which has superior power density than conventional battery technology. This makes fluid power attractive for urban driving applications in which there are frequent starts and stops and large startup power demands. The proposed design method improves the powertrain&#39;s operational efficiency by finding the best balance between optimizing individual component efficiencies. The optimization problem was implemented using the model predictive control framework because it requires no future information about the drive cycle in its design. Hardware-in-the-loop experiments using an electro-hydraulic powertrain testbed were then used to validate the dynamic model and control performance.

Enery management in Mobile Hydraulics

Mechanical Engineering, Jun 1, 2013

This paper explores research into hydraulic hybrids that span a wide range of applications from h... more This paper explores research into hydraulic hybrids that span a wide range of applications from heavy-duty vehicles, such as city buses, to small passenger vehicles. This case study also highlights the importance of having a well-designed energy management strategy if one is to maximize benefit of the hybrid powertrain. There is potential for hydraulic hybrid vehicles to offer a cost-effective solution to the need for increased efficiency in transportation systems. The high-power density of fluid power makes it a natural choice for energy storage in urban driving environments where there are frequent starts/stops and large acceleration/braking power demands. Because the opportunities and challenges of fluid power are different than those of electrical power, unique control strategies are needed and a summary of common energy management strategies (EMS) design methods for hydraulic hybrids has been presented.

Optimal Energy Use in a Light Weight Hydraulic Hybrid Passenger Vehicle

Journal of Dynamic Systems Measurement and Control-transactions of The Asme, Apr 27, 2012

In this study we present a procedure for the design and implementation of a control strategy to o... more In this study we present a procedure for the design and implementation of a control strategy to optimize energy use within a light weight hydraulic hybrid passenger vehicle. The hydraulic hybrid utilizes a high pressure accumulator for energy storage which has superior power density than conventional battery technology. This makes fluid power attractive for urban driving applications in which there are frequent starts and stops and large startup power demands. A dynamic model of a series hydraulic hybrid powertrain is presented along with the design of a model predictive control based energy management strategy. Model predictive control was chosen for this study because it uses no future information about the drive cycle in its design. This increases the flexibility of the controller allowing it to be directly applied to a variety of drive cycles. Using the model predictive framework, a holistic view of the powertrain was taken in the design of the control strategy, and the impact of each actuator’s efficiency on overall efficiency was evaluated. A hardware-in-the-loop experiment using an electro-hydraulic powertrain testbed was then used to validate the dynamic model and control performance. Through a simulation study in which each actuator’s efficiency was given varying levels of priority in the objective function, it was found that overall system efficiency could be improved by allowing for small sacrifices in individual component performance. In fact, the conventional wisdom of using the additional degrees of freedom within a hybrid powertrain to optimize engine efficiency was found to yield the lowest overall powertrain efficiency. In this work we present a rigorous framework for the design of an energy management strategy. The design method improves the powertrain’s operational efficiency by finding the best balance between optimizing individual component efficiencies. Furthermore, since the design of the control strategy is built upon an analysis of individual components, it can be readily extended to other architectures employing different actuators.