SUMMARYThe control algorithm based on the uncertainty and disturbance estimator (UDE) is a robust control strategy and has received wide attention in recent years. In this paper, the two-degree-of-freedom nature of UDE-based controllers is revealed. The set-point tracking response is determined by the reference model, whereas the disturbance response and robustness are determined by the error feedback gain and the filter introduced to estimate the uncertainty and disturbances. It is also revealed that the error dynamics of the system is determined by two filters, of which one is determined by the error feedback gain and the other is determined by the filter introduced to estimate the uncertainty and disturbances. The design of these two filters are decoupled in the frequency domain. Moreover, after introducing the UDE-based control, the Laplace transform can be applied to some time-varying systems for analysis and design because all the time-varying parts are lumped into a signal. It has been shown that, in addition to the known advantages over the time-delay control, the UDE-based control also brings better performance than the time-delay control under the same conditions. Design examples and simulation results are given to demonstrate the findings.

No abstract

No abstract

Thermal management, in particular, heat recovery and utilisation in internal combustion engines result in improved fuel economy, reduced emissions, fast warm up and optimized cylinder head temperatures. Turbocompounding is a heat recovery technique that has been successfully used in medium and large scale engines. Heat recovery to a secondary fluid and expansion is used in large scale engines, such as in power plants in the form of heat recovery steam generators(HRSG) [1]. The present paper presents a thermodynamic analysis of turbocompounding and heat recovery and utilisation through a fluid power cycle, a technique that is also applicable to medium and small scale engines. In a fluid power cycle, the working fluid is stored in a reservoir and expanded subsequently. The reservoir acts as an energy buffer that improves the overall efficiency, significantly. This paper highlights the relative advantage of exhaust heat secondary power cycles over turbocompounding with the aid of MATLAB based QSS Toolbox [2] simulation results. Steam has been selected as the working fluid in this work for its superior heat capacity over organic fluids and gases.

In this paper, a robust control strategy based on the uncertainty and disturbance estimator (UDE) is proposed for uncertain Linear Time Invariant-Single Input Single Output (LTI-SISO) systemswith state delays. The knowledge of the bounds of uncertainties and disturbances is not needed during the design process although it is required for the stability analysis. Both the cases with known and unknown delays are considered. In the case of unknown delays, the terms involving the delays are treated as additional disturbances to the system. The robust stability of the closed-loop system is analyzed in detail, and a stability condition is proposed. Simulations are given to demonstrate the excellent tracking and disturbance rejection capabilities of the UDE-based control strategy.

The combination of model predictive control based on linear models (MPC) with feedback linearization (FL) has attracted interest for a number of years, giving rise to MPC+FL control schemes. An important advantage of such schemes is that feedback linearizable plants can be controlled with a linear predictive controller with a fixed model. Handling input constraints within such schemes is difficult since simple bound contraints on the input become state dependent because of the nonlinear transformation introduced by feedback linearization. This paper introduces a technique for handling input constraints within a real time MPC/FL scheme, where the plant model employed is a class of dynamic neural networks. The technique is based on a simple affine transformation of the feasible area. A simulated case study is presented to illustrate the use and benefits of the technique.

No abstract

No abstract