Publications

We consider mechanical systems, which are not known precisely. In detail we assume that the system parameters are unknown (lack of precise knowledge), moreover, we allow for uncertainties with respect to input and output, and to perturbations from the environment (ground excitations) as well. The consideration of such systems leads to the use of adaptive control. The aim is to design universal adaptive controllers, which achieve a pre-specified control objective. Almost all controllers existing in the literature offer the same drawback: (possibly unboundedly) monotonically increasing gain parameter. With respect to limited resources in applications it is necessary to design improved adaptation laws. We present simulations of several gain parameter models primarily in application to bio-inspired sensors.

In the present paper non-classical ways of locomotion of the mechanical systems are considered. In the first part the locomotion of a chain of interconnected mass points in a straight line is analyzed. On each mass point acts a small non-symmetric Coulomb's dry friction. The magnitude of this force depends on the direction of motion. The distance between the neighboring mass points changes according to the harmonical law. With the help of the procedure of averaging the expression for the stationary velocity of the mass center of the chain "on average" is found. The dependences of the stationary velocity on the value of the asymmetry and on the number of mass points are obtained. In the second part the mechanical background of the two mobile robots based on smart materials is considered. One of the systems consists of a single symmetric ferroelastomer body and, additionally, six micro-coils. The locomotion of the system is caused by a periodic deformation (generated by integrated micro-coils) of a compliant magneto-sensitive body. The qualitative description of the mechanical system's performance was realized by a transient dynamical analyses using the software package ANSYS. Another system consists of three components: information system, power supply (accumulator) and vibration system. The vibration system is formed by a piezoelectric actuator bonded on a triangular plate. At the corners of the plate three "legs" are fixed. A Finite-Element-Model of the legs, the plate and the actuators was created in order to formulate statements about the influence of the excitation frequency on the trajectories of the endpoints of the legs. The results obtained by the numerical simulation are compared with the experimental data.

The article demonstrates some examples of locomotion systems with bifluidic flow control using ferrofluid. By controlling the change of shape, position, and pressure of the ferrofluid in a secondary low viscous fluid by magnetic fields locomotion of objects or the ferrofluid itself can be realized. The locomotion of an object is caused, in the first example, ba a ferrofluid generated flow of the secondary fluid and in the second and third case by the direct alteration of the ferrofluid position.

Some theoretical investigations of the motion of a straight chain of mass points interconnected with kinematical constraints are considered. The ground contact can be described by dry (discontinuous) friction. The controls are assumed in the form of periodic functions with zero average, shifted on a phase on concerning each other. Thus, there is a spreading wave along the chain of point masses. In the case of small friction we derive a condition for the locomotion of the center of the mass with the help of an average method. It is shown that, using spedified control motion is possible not only in the case of isotropic friction, but also in the direction of the greater friction in the case of non-isotropic friction. The received theoretical results can be used for the development of mobile robots applying the principles of the motion outlined above.