Browsing by Author "Blajer, Wojciech"

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Open Access
Closing conditions and reaction forces of multibody systems
(1992) Schiehlen, Werner; Blajer, Wojciech
Over the years a considerable effort has been focused on the development of methods and computational algorithms for mathematical modelling and simulation of multibody systems. The methods are mainly concerned with effective formulation and numerical treatment of the dynamical equations of a general multibody system.
Open Access
A concept for motion control of biped impactless walk
(1992) Blajer, Wojciech; Schiehlen, Werner
An approach for modelling a biped impactless walk and for determining the control ensuring the realization of the reference motion is proposed. In order to avoid impacts, botb the motion of the biped and some ground reactions on it are specified appropriately, yielding a combined motion and force control ploblem. A concept is given for synthesizing a nominal (feedforward) control and and for designing a feedback controller. Finally, a short discussion on effective formulation of motion specifications and on an on-line control concept is provided. The impactless planar walking of a seven-link biped serves as an illustration.
Open Access
Dynamic analysis of constrained multibody systems using inverse kinematics
(1993) Blajer, Wojciech; Schiehlen, Werner; Schirm, Walter
This paper draws attention to the advantages that may arise in the dynamic analysis or constrained multibody systems by applying special algorithms of inverse kinematics developed in the field or robotics. The algorithms result in explicit (recursive) relations for the arbitrary chosen dependent coordinates as functions or the remaining (independent) ones. Then analogous velocity and acceleration relations are available. Using these explicit closing condition forms, minimal-dimension governing equations of a constrained system can be formulated conveniently. The avoidance or singularities in the analysis is discussed. An illustrative example is included.
Open Access
An orthogonal complement matrix formulation for constrained multibody systems
(1994) Blajer, Wojciech; Bestle, Dieter; Schiehlen, Werner
A method is proposed for the automatic generation of an orthogonal complement matrix to the constraint matrix for the dynamic analysis of constrained multibody systems. The clue for this method lies in the determination of local constraint matrices and their orthogonal complements relative to the local reference frames of particular constrained points. These matrices are then transformed into the system's configuration space in order to form the final constraint matrix and its orthogonal complement. The avoidance of singularities in the formulation is discussed. The method is specially suited for the dynamic analysis of multibody systems with many constraints and/or closed-loops.
Open Access
A projective criterion to the coordinate partitioning method for multibody dynamics
(1994) Blajer, Wojciech; Schiehlen, Werner; Schirm, Walter
The paper discusses some developments in the coordinate partitioning method for the dynamic analysis of constrained/closed-loop multibody systems. First, the method is reformulated to a more compact form. Then, a simple and reliable projective criterion for choosing the best coordinates from the redundant ones is proposed, and some advantages are pointed out that may arise in the method by applying inverse kinematics algorithms. Finally, the problem of determination ofphysical reactions of constraints and closing conditions is discussed. A four-bar linkage mechanism serves for an illustration of some aspects of the paper.
Open Access
Walking without impacts as a motion/force control problem
(1992) Blajer, Wojciech; Schiehlen, Werner
The paper deals with the synthesis of control for impactless bipedal walking. In order of avoid impulses, both the specified motion of the biped and its ground reactions are controlled, yielding a combined motion and force control problem. A method for modeling and solving such problems is proposed. and then illustrated by the example of an impactless planar walk of a seven-link bipedal robot. Some numerical results of the motion simulation are reported.
Open Access
Zur Behandlung von Mehrkörpersystemen mit kinematischen Schleifen in Minimalform
(1993) Schirm, Walter; Blajer, Wojciech; Schiehlen, Werner
Zusammengefaßt kann gesagt werden, daß das hier beschriebene Verfahren zur Simulation von Mehrkörpersystemen mit geschlossenen kinematischen Schleifen auf der Kenntnis der expliziten Schließbedingungen aufbaut. Es wurde gezeigt, daß diese unter Verwendung existierender Verfahren rechnergestützt bestimmt werden können. Die zur Simulation günstigsten Bewegungsgleichungen in Minimalform können mit Hilfe eines Auswahlkriteriums einfach formuliert werden, wobei ein Wechsel der Koordinaten im Verlauf der Simulation ohne Verlust der Integrationsschrittweite und -ordnung möglich ist. Darüber hinaus lassen sich unabhängig von der Dynamik-Simulation die Schleifenschließkräfte bestimmen. Das hier beschriebene Verfahren beruht auf einer nichtrekursiven Berechnung der Bewegungsgleichungen.