A Time-Frequency Local Polynomial Approach to FRM Estimation from Incomplete Data

Frequency Response Matrix (FRM) estimation from measured data is an important step towards the control of complex systems, including motion and thermal systems. Missing samples in the measured data records, e.g., due to sensor failure or faulty data transmission, often occur. In this paper, a method is presented for the nonparametric FRM identification of multiple-inputs multiple-outputs (MIMO) systems from incomplete and noisy data records. The method exploits time- and frequency-domain localizing wavelets to accurately estimate the FRM and its covariance from the time-frequency plane. Good performance is demonstrated in a simulation study

A Fast Smoothing-Based Algorithm to Generate l∞-Norm Constrained Signals for Multivariable Experiment Design

Handling peak amplitude constraints, or equivalently l_infty-norm constraints, is an important application demand in experiment design for system identification. The aim of this paper is to present a method for the design of excitation signals with prescribed power spectrum under l_infty-norm constraints for systems with many inputs and outputs. The method exploits an exponential smoothing function in an iterative algorithm. Fast convergence is achieved by a computationally efficient construction of the gradient and the Hessian matrix. Experimental results show excellent convergence behavior that overcomes local minima, while significantly reducing computation time compared to existing techniques

Inferential control of a wafer stage using disturbance observers

In high-precision motion systems it is often not possible to directly measure at the location where performance is required. Therefore, performance variables need to be inferred from non-collocated sensor measurements. If flexible behavior is negligible, a static sensor transformation is used to find a rigid-body (RB) approximation of the performance variable. However, for next-generation motion systems positioning accuracy is ever-increasing, leading to a situation where flexible dynamics are not negligible. As a result, traditional single degree-of-freedom (DOF) controllers are inadequate [1]. The aim of this research is to control the unmeasured performance variable while taking flexible behavior into account, through 2-DOF controller structures and disturbance observers

Animating experience

The imperative for participation in social work education has led to consideration of the ways in which service users’ and carers’ voices can best be heard by students. At Glyndŵr University, this debate has resulted in the development of a service user and carer-led module which will introduce students to a variety of creative approaches as a way of telling narratives of experience. In preparation for the module, a pilot project was run to assess the particular benefits of using animation for this purpose. This reflective case study describes the experiences of a social work student who worked with a carer to make a short animated film. It articulates the ways in which theoretical teaching was brought to life by working intensively. It demonstrates that creative approaches can offer a constructive means of addressing the need to cater for diverse learning styles. In addition, it adds weight to the argument that service users’ and carers’ experiential knowledge should be taken as seriously as other forms of knowledge