Karl Gotlih

Base invariance of the manipulability index

The manipulability index suggested by Yoshikava is an important tool for the design of mechanisms and their control. It represents a quantitative measure of the functionality and the ability for realizing some tasks or groups of tasks. This index is some kind of performance measure and should be taken into consideration in the design phase of a mechanism and also in the design of control algorithms.In this paper two important properties of the manipulability index are investigated. The first part of the present work demonstrates that manipulability of a mechanism is independent of task space coordinates. In the second part, a proof of the independency of the manipulability index on the first DOF is given.This invariance is important for simplification of the mechanisms Jacobian matrix and gives excellent insight into the dependences of configuration space coordinates on this index. Moreover, it proves that the manipulability index is determined only by relative positions of the mechanism itself and by the mechanisms geometry.Finally, the properties of the manipulability index are illustrated by some examples for fundamental open kinematical chain structures.

Sewing needle penetration force study

Demonstrates the modelling of the kinetic process when the sewing needle enters the fabric. To get an adequate mechanical model of the given problem, the function ‐ the mathematical model ‐ of the penetration force with respect to the fabric, the needle and the mechanism in the sewing machine must be developed. The fabric was modelled as a combination of warp and weft threads. Each thread from the fabric is modelled as an ideal elastic Hook’s material. Outlines the restrictions which needed to be made to get the mathematical model of the problem.

Global optimal control of redundant robot

A global optimal control algorithm was developed with the aim of finding a control which satisfies some special requirements in the sense of obtaining singular position free movement of the redundant robot mechanism. The solution of the developed global optimal control algorithm is a boundary value problem. The additional constraints in the boundary value problem were constructed with the use of an optimization process. The usefulness of the developed global optimal control algorithm is demonstrated by the example of the 3 DOFs planar redundant robot mechanism of SCARA type.

Viscoelastic parameter determination for a yarn

Here parameter determination of a chosen rheological model of a yarn on the basis of the experimental results is shown. The Kelvin‐Voigt linear viscoelastic model of a solid material was chosen. The real yarn was used in the tear experiment. The knowledge of the stress‐strain curve is the measurement for the determination of the rheological parameter. The calculation of the Kelvin‐Voigt’s parameters, with respect to the known stress‐strain curve of the real yarn, is done with an optimisation method. In this numerical procedure the area between the response of the real yarn and the yarn model is minimised. The optimisation results show good coincidence of the real mechanical properties of the real yarn with the Kelvin‐Voigt rheological model. The model of the yarn enables simulation of real processes, which is easier because observation of the real systems are then not necessary, which is easier, more transparent and cheaper.

Effect of enzyme treatments on interlock knitted fabric

Purpose – Enzyme treatment technologies are frequently applied in textile processing for the modification of fabric handle appearance and other surface characteristics in regard to cotton and cotton blended fabrics. The purpose of this paper is to understand the impact of enzyme treatments on fabric preparation, dyeing, and finishing processes of woven fabrics. In particular, certain mechanical and surface properties of 100 percent cotton interlock knitted fabrics after treatment with a cellulase enzyme.Design/methodology/approach – Interlock knitted fabrics were used for this research. These cotton fabrics were treated with experimental Trichoderma reesei cellulases containing different cellulase profiles and treatment was carried out under laboratory conditions. The effects of cellulase treatment on weft knitted fabric regarding mechanical and surface properties were evaluated using the KES‐FB Kawabata evaluation system. The influence of enzyme treatments, friction, and geometrical roughness on the face...

Parameter Fitting for Soft Dielectric Elastomer Actuator

Big progress has been made recently in humanoid robotics with the development of human like robots. Humanoid robots are becoming more and more similar to humans, but what they still lack are proper mechanical actuators which are still based on rotary motors or pneumatic cylinders. With the development of soft actuators one is getting closer to mimic the natural behavior of muscles. Dielectric elastomer actuators can be used as soft actuators. They can be described with fractional derivative Kelvin-Voigt model. With the help of fractional derivatives and least-square method one can use this combination in algorithm for parameter fitting. Fractional Kelvin-Voigt model can describe wider working frequency range of dielectric elastomer actuator as can basic Kelvin-Voigt model do.

Influence of Injection Molding Process Parameters on Part Quality

A case study to determine the influence of injection molding process parameters on part quality is performed. Part quality is evaluated based on deflection rate, volumetric shrinkage, and sink mark depth results. Considered process parameters are mold temperature, melt temperature, injection time, pack time, pack pressure and cooling time. A thin walled butterfly valve flap and a thick walled butterfly valve shaft are analyzed separately. Polypropylene is used as molding material. A design of experiment based on the Taguchi method is generated for both parts and a computer simulation to solve the case matrixes is executed. Relative process parameter influence on each individual quality criteria is determined by analysis of variance. Importance of process temperatures as well as parameter impact dependence on characteristic part shape is reveled.

Use of mathematical programming for workplace design in sewing rooms

Shows an approach to workplace design, employing a well‐known prescribed technological operation. Using a non‐linear optimization method, searches for the minimal value of the objective function with respect to the constraints determined by the human locomotive sytem and by the prescribed technological operation of sewing cloth parts. Demonstrates the usefulness of this approach with a sewing example, where the reference task is the movement of the operator’s arms with the defined velocity profile.