No abstract

Drill strings are used in the oil and gas industry to search for oil, gas, and geothermal resources and form extremely slender structures which makes them very sensitive to torsional and other vibrations. In order to immensely reduce torsional vibrations along the whole string, a wave based control method was developed at our institute. Numerical simulations and tests at an experimental setup showed very good results, but the implementation in a real drilling rig has not yet been taken place. One apparent difference in a real drill string will be the assembly of many rather short drill pipes, which is unregarded in conventional models and our small test rig. This might lead to improper behavior of our wave based control mechanism and shall be investigated is this paper. We present a model that accounts for a discontinuously built drill string and show the consequences for our advanced control method via numerical simulations.

We present an adaptive fuzzy sliding mode control strategy in combination with a sliding mode observer for a dive cell. Numerical results demonstrate the outperformance of the presented controller compared to a conventional sliding mode approach.

Complex optimisation of the control of interconnected power systems at the interstate level is related to solution and correction of multi-level hierarchical problems of dynamic programming in general, its separate subproblems differing in the time-space and situation aspects. Starting from the complex control of instantaneous steady-states (ESS), general principles of mathematical methods and tools, applied for solution of the multi-stage hierarchical dynamic programming problem, are considered.

The concept of impedance matching is well known in electrical engineering and can be applied in mechanical engineering as well. Slender systems, which have a relatively low stiffness and should not be treated as a rigid body are typical candidates for the application of impedance matching.Impedance matching imposes a special boundary condition. In general, at the boundary of a slender mechanical system, waves are partially reflected. The goal of impedance matching is to minimize those wave reflections and to transmit the wave motion to the vicinity. In this paper, it is shown that the impedance matching approach has a great potential of damping vibrations and that a simple PID controller can be used to implement an active version.