Minimum-Information LQG Control - Part I: Memoryless Controllers

With the increased demand for power efficiency in feedback-control systems, communication is becoming a limiting factor, raising the need to trade off the external cost that they incur with the capacity of the controller's communication channels. With a proper design of the channels, this translates into a sequential rate-distortion problem, where we minimize the rate of information required for the controller's operation under a constraint on its external cost. Memoryless controllers are of particular interest both for the simplicity and frugality of their implementation and as a basis for studying more complex controllers. In this paper we present the optimality principle for memoryless linear controllers that utilize minimal information rates to achieve a guaranteed external-cost level. We also study the interesting and useful phenomenology of the optimal controller, such as the principled reduction of its order

Measuring health outcomes of a multidisciplinary care approach in individuals with chronic environmental conditions using an abbreviated symptoms questionnaire

The Nova Scotia Environmental Health Centre is a treatment facility for individuals with chronic environmental conditions such as multiple chemical sensitivity, chronic fatigue syndrome, fibromyalgia, chronic respiratory conditions and in some cases chronic pain. The premise of care is to provide a patient-centred multidisciplinary care approach leading to self-management strategies. In order to measure the outcome of the treatment in these complex problems, with overlapping diagnoses, symptoms in many body systems and suspected environmental triggers, a detailed symptoms questionnaire was developed specifically for this patient population and validated. Results from a pilot study in which an abbreviated symptoms questionnaire based on the top reported symptoms captured in previous research was used to measure the efficacy of a multidisciplinary care approach in individuals with multiple chemical sensitivity are presented in this paper. The purpose of this study was to examine the extent, type and patterns of changes over time in the top reported symptoms with treatment measured using the abbreviated symptoms questionnaire. A total of 183 active and 109 discharged patients participated in the study where the health status was measured at different time periods of follow up since the commencement of treatment at the Centre. The findings from this study were successful in generating an initial picture of the nature and type of changes in these symptoms. For instance, symptoms such as difficulty concentrating, sinus conditions and tiredness showed early improvement, within the first 6 months of being in treatment, while others, such as fatigue, hoarseness or loss of voice, took longer while others showed inconsistent changes warranting further enquiry. A controlled longitudinal study is planned to confirm the findings of the pilot study