A supervisory observer is a multiple-model architecture, which estimates the parameters and the states of nonlinear systems. It consists of a bank of state observers, where each observer is designed for some nominal parameter values sampled in a known parameter set. A selection criterion is used to select a single observer at each time instant, which provides its state estimate and parameter value. The sampling of the parameter set plays a crucial role in this approach. Existing works require a sufficiently large number of parameter samples, but no explicit lower bound on this number is provided. The aim of this work is to overcome this limitation by sampling the parameter set automatically using an iterative global optimisation method, called DIviding RECTangles (DIRECT). Using this sampling policy, we start with 1 + 2np parameter samples where np is the dimension of the parameter set. Then, the algorithm iteratively adds samples to improve its estimation accuracy. Convergence guarantees are provided under the same assumptions as in previous works, which include a persistency of excitation condition. The efficacy of the supervisory observer with the DIRECT sampling policy is illustrated on a model of neural populations.

An LCL filter utilized in an active front end (AFE) converter can generate significant resonance, which can affect quality and stability of the system. Thus, a proper active or passive damping technique and/or a suitable controller is required to be designed for the converter. The duty cycle constraint—though inevitable in practical inverter systems—is often ignored in most of the existing literature. The effects of measurement noise on filter control system performance must be considered and evaluated under different conditions. Finally, almost all inverter control systems are implemented digitally using microcontrollers. Consequently, the effects of sampling on control system stability and performance should be evaluated as well. Thus, this paper presents stability analysis of an AFE converter-based filter design with a complete practical system configuration, including saturation and sampling blocks and measurement noises. Mathematical analysis and simulations have been carried out to validate the proposed method.

In literature regarding the dynamics of the CardanHooke joint, the inertial characteristics of shafts and a cross and their influence on the joint torque transmission are often ignored (see e.g. [1]). In [2], the cross inertia and its effect on shafts bearing reactions at the constant angular velocity of the input shaft was considered. On the other hand, the problem of the torque transmission at a variable angular velocity of the input shaft and in the presence of both structural and error misalignments between the shafts is considered in [3]. Moreover, the inertial characteristic of the cross is not taken into account. In [4], only the inertia of shafts was taken into account. The aim of this paper is to form a relation between the applied and resisting torques, which will be taken into account inertial characteristics of both the cross and the shafts. In general case, the variable angular velocity of the input shaft is assumed where elasticity effects and friction are ignored.