Uniform convergence of monotone measure differential inclusions: with application to the control of mechanical systems with unilateral constraints

In this paper, we present theorems which give sufficient conditions for the uniform convergence of measure differential inclusions with certain maximal monotonicity properties. The framework of measure differential inclusions allows us to describe systems with state discontinuities. Moreover, we illustrate how these convergence results for measure differential inclusions can be exploited to solve tracking problems for certain classes of nonsmooth mechanical systems with friction and one-way clutches. Illustrative examples of convergent mechanical systems are discussed in detail

Stability and stabilization of networked control systems

The presence of a communication network in a control loop induces many imperfections such as varying transmission delays, varying sampling/transmissionintervals, packet loss, communication constraints and quantization effects, which can degrade the control performance significantly and even lead to instability. Various techniques have been proposed in the literature for stability analysis and controllerdesign for these so-called networked control systems. The aim of this chapter is to survey the main research lines in a comprehensive manner

Convergent systems:nonlinear simplicity

\u3cp\u3eConvergent systems are systems that have a uniquely defined globally asymptotically stable steady-state solution. Asymptotically stable linear systems excited by a bounded time varying signal are convergent. Together with the superposition principle, the convergence property forms a foundation for a large number of analysis and (control) design tools for linear systems. Nonlinear convergent systems are in many ways similar to linear systems and are, therefore, in a certain sense simple, although the superposition principle does not hold. This simplicity allows one to solve a number of analysis and design problems for nonlinear systems and makes the convergence property highly instrumental for practical applications. In this chapter, we review the notion of convergent systems and its applications to various analyses and design problems within the field of systems and control.\u3c/p\u3

Extremum-seeking control for steady-state performance optimization of nonlinear plants with time-varying steady-state outputs

Extremum-seeking control is a useful tool for the steady-state performance optimization of plants for which the dynamics and disturbance situation can be unknown. The case when steady-state plant outputs are constant received a lot of attention, however, in many applications time-varying outputs characterize plant performance. As a result, no static parameter-to-steady-state performance map can be obtained. Recently, we proposed an extremum-seeking control method that uses a so-called dynamic cost function to cope with these time-varying outputs. We showed that, under appropriate conditions, the solutions of the extremum-seeking control scheme are uniformly ultimately bounded in view of bounded and time-varying external disturbances, and the region of convergence towards the optimal tunable plant parameters can be made arbitrarily small. In this technical report, a proof of the local stability result is presented

Nonlinear modeling for analysis of directional drilling processes

Directional drilling allows for the drilling of boreholes with complex shapes, which are needed to reach unconventional reservoirs of oil, gas and mineral resources. Figure 1 shows a sketch of a directional drilling system. The drillstring is a hollow slender pipe with most of it is in tension under its own weight, except for the bottom hole assembly (BHA),\u3cbr/\u3ewhich is in compression. The BHA contains several stabilizers ensuring centering of the BHA inside the borehole, a bit penetrating the rock formation and a rotary steerable system (RSS), being a robotic actuator, steering the BHA. In practice, directional drilling often results in spiraled boreholes, see Figure 2 for an illustration. These are unwanted selfexcited oscillations in the borehole geometry which negatively influence the drilling process and the borehole qualit

Power scheduling in islanded-mode microgrids using fuel cell vehicles

\u3cp\u3eWe consider power scheduling in a microgrid operated in the islanded mode. It is assumed that at any time all the renewable energy sources are generating the maximum achievable electrical power based on the weather conditions and the power balance of the microgrid is exclusively done by a fleet of fuel cell cars. As a result, the uncertainty in the prediction of the load will also make the future power generation of the fuel cell cars uncertain and, hence, a robust control method should be used to operate the fuel cell cars. We develop a min-max model predictive control approach to schedule the power generation profile of the fuel cell cars. Furthermore, we develop an alternative approach, a min-max disturbance feedback approach, in order to reduce the conservatism of the min-max approach. Finally, an illustrative case study shows the performance of the proposed approaches.\u3c/p\u3

Nonlinear dynamic modeling and analysis of borehole propagation for directional drilling

Boreholes with complex trajectories are drilled with the help of downhole rotary steerable systems. These robotic actuators, which are embedded in the drillstring, are used to steer the bit in the desired direction. This paper presents a dynamic non-smooth borehole propagation model for planar directional drilling. Essential nonlinearities, induced by the saturation of the bit tilt and by non-ideal (undergauged) stabilizers, are modeled using complementarity conditions, leading to a closed-form analytical description of the model in terms of a so-called delay complementarity system. The analytical form of the model allows for a comprehensive dynamic and parametric analysis. Firstly, (quasi-)stationary solutions generated by constant actuator forces are analyzed parametrically as a function of the actuation force. Secondly, an analysis of the local stability of these solutions shows the coexistence of multiple (stable and unstable) solutions and their dependency on key system parameters, such as the weight-on-bit and bit characteristics. Thirdly, a numerical simulation study shows the existence of steady-state oscillations, which are a consequence of the non-smooth characteristics of the bit tilt saturation and the stabilizers. Such limit cycles represent borehole rippling, which is the planar equivalent of the highly detrimental borehole spiraling observed in practice. The constructed model and the pursued analysis provide essential insights in the effects causing undesired borehole rippling. Herewith, the presented results can be used to support improved directional drilling system design and to form the basis for further work on automation techniques for the downhole robotic actuator to mitigate spiraled boreholes