Stiffness based trajectory planning and feedforward based vibration suppression control of parallel robot machines

The dissertation proposes two control strategies, which include the trajectory planning and vibration suppression, for a kinematic redundant serial-parallel robot machine, with the aim of attaining the satisfactory machining performance. For a given prescribed trajectory of the robot's end-effector in the Cartesian space, a set of trajectories in the robot's joint space are generated based on the best stiffness performance of the robot along the prescribed trajectory. To construct the required system-wide analytical stiffness model for the serial-parallel robot machine, a variant of the virtual joint method (VJM) is proposed in the dissertation. The modified method is an evolution of Gosselin's lumped model that can account for the deformations of a flexible link in more directions. The effectiveness of this VJM variant is validated by comparing the computed stiffness results of a flexible link with the those of a matrix structural analysis (MSA) method. The comparison shows that the numerical results from both methods on an individual flexible beam are almost identical, which, in some sense, provides mutual validation. The most prominent advantage of the presented VJM variant compared with the MSA method is that it can be applied in a flexible structure system with complicated kinematics formed in terms of flexible serial links and joints. Moreover, by combining the VJM variant and the virtual work principle, a systemwide analytical stiffness model can be easily obtained for mechanisms with both serial kinematics and parallel kinematics. In the dissertation, a system-wide stiffness model of a kinematic redundant serial-parallel robot machine is constructed based on integration of the VJM variant and the virtual work principle. Numerical results of its stiffness performance are reported. For a kinematic redundant robot, to generate a set of feasible joints' trajectories for a prescribed trajectory of its end-effector, its system-wide stiffness performance is taken as the constraint in the joints trajectory planning in the dissertation. For a prescribed location of the end-effector, the robot permits an infinite number of inverse solutions, which consequently yields infinite kinds of stiffness performance. Therefore, a differential evolution (DE) algorithm in which the positions of redundant joints in the kinematics are taken as input variables was employed to search for the best stiffness performance of the robot. Numerical results of the generated joint trajectories are given for a kinematic redundant serial-parallel robot machine, IWR (Intersector Welding/Cutting Robot), when a particular trajectory of its end-effector has been prescribed. The numerical results show that the joint trajectories generated based on the stiffness optimization are feasible for realization in the control system since they are acceptably smooth. The results imply that the stiffness performance of the robot machine deviates smoothly with respect to the kinematic configuration in the adjacent domain of its best stiffness performance. To suppress the vibration of the robot machine due to varying cutting force during the machining process, this dissertation proposed a feedforward control strategy, which is constructed based on the derived inverse dynamics model of target system. The effectiveness of applying such a feedforward control in the vibration suppression has been validated in a parallel manipulator in the software environment. The experimental study of such a feedforward control has also been included in the dissertation. The difficulties of modelling the actual system due to the unknown components in its dynamics is noticed. As a solution, a back propagation (BP) neural network is proposed for identification of the unknown components of the dynamics model of the target system. To train such a BP neural network, a modified Levenberg-Marquardt algorithm that can utilize an experimental input-output data set of the entire dynamic system is introduced in the dissertation. Validation of the BP neural network and the modified Levenberg- Marquardt algorithm is done, respectively, by a sinusoidal output approximation, a second order system parameters estimation, and a friction model estimation of a parallel manipulator, which represent three different application aspects of this method.

It all comes back to you

Soitinnus: big band.

Recovery of carboxylic acids from aqueous streams by extraction and back extraction

Separation of carboxylic acids from aqueous streams is an important part of their manufacturing process. The aqueous solutions are usually dilute containing less than 10 % acids. Separation by distillation is difficult as the boiling points of acids are only marginally higher than that of water. Because of this distillation is not only difficult but also expensive due to the evaporation of large amounts of water. Carboxylic acids have traditionally been precipitated as calcium salts. The yields of these processes are usually relatively low and the chemical costs high. Especially the decomposition of calcium salts with sulfuric acid produces large amounts of calcium sulfate sludge. Solvent extraction has been studied as an alternative method for recovery of carboxylic acids. Solvent extraction is based on mixing of two immiscible liquids and the transfer of the wanted components form one liquid to another due to equilibrium difference. In the case of carboxylic acids, the acids are transferred from aqueous phase to organic solvent due to physical and chemical interactions. The acids and the extractant form complexes which are soluble in the organic phase. The extraction efficiency is affected by many factors, for instance initial acid concentration, type and concentration of the extractant, pH, temperature and extraction time. In this paper, the effects of initial acid concentration, type of extractant and temperature on extraction efficiency were studied. As carboxylic acids are usually the products of the processes, they are wanted to be recovered. Hence the acids have to be removed from the organic phase after the extraction. The removal of acids from the organic phase also regenerates the extractant which can be then recycled in the process. The regeneration of the extractant was studied by back-extracting i.e. stripping the acids form the organic solution into diluent sodium hydroxide solution. In the solvent regeneration, the regenerability of different extractants and the effect of initial acid concentration and temperature were studied.

Tavanomaisen irtaimen esineen sale and lease back -järjestely. Tarkastelussa erityisesti vuokralleottajan sivullissuoja.

Tutkielman aiheena on tavanomaisen irtaimen esineen sale and lease back -järjestely. Järjestelyyn kuuluu nimensä mukaisesti luovutus ja takaisinvuokraus. Kokonaisjärjestelyn avulla rahoittaja ja luotonsaaja pyrkivät luomaan luotonmaksun vakuudeksi omistusoikeuteen perustuvan esinevakuuden. Järjestelyn tavoitteena on, että luotonsaajan asemassa oleva myyjä pystyisi käyttämään samaa esinettä samanaikaisesti sekä va-kuusobjektina että elinkeinotoimintansa tuotantovälineenä. Juuri siitä syystä, että luo-tonsaaja tarvitsee esinettä koko ajan elinkeinotoiminnassaan, ei panttausta voida käyttää. Tutkielma on oikeusdogmaattinen ja sen pyrkimyksenä on antaa selkeä kokonaiskäsitys irtaimen esineen sale and lease back -järjestelystä ja sen käytettävyydestä vakuusjärjestelynä. Oikeusdogmaattiselle tutkimukselle tyypillisesti tutkielmassa tarkastellaan olemassa olevaa tietomateriaalia. Keskeisimmät tutkielmassa käytetyt kirjallisuuslähteet ovat Jarno Teporan useat sale and lease back -järjestelyyn keskittyvät artikkelit, Jarmo Tuomiston omistusvakuuksia koskeva kirjallisuus sekä Erkki Havansin esineoikeudellinen perusteos Esinevakuudet. Virallislähteistä selvästi merkittävimmät ovat vuonna 1997 voimaantullut maakaari ja sen esityöt. Tutkimuksessa keskitytään erityisesti vuokralleottajan sivullissuojaan. Näin ollen tärkeimmäksi tutkimuskysymykseksi jäsentyy se, voiko sale and lease back -järjestelyssä ostajan roolissa oleva sijoittaja tai rahoittaja saavuttaa järjestelyn avulla kollisiotilanteiden varalta turvaavan vakuusaseman. Tutkimuksen kannalta keskeinen omistusvakuus-järjestely on vakuusluovutus, jollaiseksi vakuustarkoituksessa tehty sale and lease back -järjestely melko vakiintuneesti tulkitaan. Tutkimuksessa tarkastellaan mahdollisuutta hyväksyä sale and lease back -järjestely rahoittajalle dynaamista kollisiosuojaa tarjoavaksi vakuusjärjestelyksi ilman julkivarmistusta. Toisaalta selvitetään julkivarmistuksen toteuttamisen mahdollisuutta ilman hallinnansiirtoa muun muassa maakaaren 14:4.1:n 1 kohdan mukaisen kirjaamisen avulla. Nykylainsäädännön puitteissa järjestelyn hyväksyminen itsenäiseksi omistusvakuudeksi näyttää olevan epätodennäköistä ja ilman julkivarmistusta dynaaminen sivullissuoja jää saavuttamatta, vaikka järjestely on sitova inter partes. Tutkimuksen loppupäätelmissä pohditaan, voisiko sale and lease back -järjestelyyn liittyviä ongelmia ratkaista muuttamalla voimassa olevaa lainsäädäntöä tai antamalla täysin uutta lainsäädäntöä. Asiaa pohditaan myös oikeusvertailun keinoin selvittäen muiden Pohjoismaiden sekä Saksan oikeusjärjestelmien kantaa järjestelyyn.