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Phase Shifted Pulse Height Modulated Motor Control for Multiply Actuated Joints to Optimize Operating Characteristics

Siedel T., Bethge S., Hild M.

Journal of Automation Mobile Robotics and Intelligent Systems

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2016

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Vol. 10, No. 2

15--24

EN

In this article, we propose two model free control schemes that are based on pulse height modulation using low frequencies with the goal to compensate normal friction effects in drive trains that negatively influence the performance of e.g. a standard PID controller. The first control scheme uses pulse height modulation to especially compensate stick slip effects but increases vibration and noise in the drive train. To reduce such side effects a modified phase shifed pulse height control scheme based on multiple actuated joints is introduced. Both control schemes are compared with a standard linear controller as reference and evaluated by using six quality criteria.

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Pcl/Chitosan Blended Nanofibrous Tubes Made by Dual Syringe Electrospinning

Hild M., Al Rez M. F., Aibibu D., Toskas G., Cheng T., Laourine E., Cherif C.

Autex Research Journal

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2015

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Vol. 15, no. 1

54--59

EN

3D tubular scaffolds made from Poly-(Ɛ-caprolactone) (PCL)/chitosan (CS) nanofibres are very promising candidate as vascular grafts in the field of tissue engineering. In this work, the fabrication of PCL/CS-blended nanofibrous tubes with small diameters by electrospinning from separate PCL and CS solutions is studied. The influence of different CS solutions (CS/polyethylene glycol (PEO)/glacial acetic acid (AcOH), CS/trifluoroacetic acid (TFA), CS/ AcOH) on fibre formation and producibility of nanofibrous tubes is investigated. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is used to verify the presence of CS in the blended samples. Tensile testing and pore size measurements are done to underline the good prerequisites of the fabricated blended PCL/ CS nanofibrous tubes as potential scaffolds for vascular grafts. Tubes fabricated from the combination of PCL and CS dissolved in AcOH possesses properties, which are favourable for future cell culture studies.

3

Pure chitosan microfibres for biomedical applications

Toskas G., Brünler R., Hund H, Hund R D, Hild M., Aibibu D., Cherif C.

Autex Research Journal

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2013

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Vol. 13, no. 4

134--140

EN

Due to its excellent biocompatibility, Chitosan is a very promising material for degradable products in biomedical applications. The development of pure chitosan microfibre yarn with defined size and directional alignment has always remained a critical research objective. Only fibres of consistent quality can be manufactured into textile structures, such as nonwovens and knitted or woven fabrics. In an adapted, industrial scale wet spinning process, chitosan fibres can now be manufactured at the Institute of Textile Machinery and High Performance Material Technology at TU Dresden (ITM). The dissolving system, coagulation bath, washing bath and heating/drying were optimised in order to obtain pure chitosan fibres that possess an adequate tenacity. A high polymer concentration of 8.0–8.5% wt. is realised by regulating the dope-container temperature. The mechanical tests show that the fibres present very high average tensile force up to 34.3 N, tenacity up to 24.9 cN/tex and Young’s modulus up to 20.6 GPa, values much stronger than that of the most reported chitosan fibres. The fibres were processed into 3D nonwoven structures and stable knitted and woven textile fabrics. The mechanical properties of the fibres and fabrics enable its usage as textile scaffolds in regenerative medicine. Due to the osteoconductive properties of chitosan, promising fields of application include cartilage and bone tissue engineering.