Trading the stability of finite zeros for global stabilization of nonlinear cascade systems

This paper analyzes the stabilizability properties of nonlinear cascades in which a nonminimum phase linear system is interconnected through its output to a stable nonlinear system. It is shown that the instability of the zeros of the linear system can be traded with the stability of the nonlinear system up to a limit fixed by the growth properties of the cascade interconnection term. Below this limit, global stabilization is achieved by smooth static state feedback. Beyond this limit, various examples illustrate that controllability of the cascade may be lost, making it impossible to achieve large regions of attractions.

The meaning of environmental control systems (ECS) for people with spinal cord injury: An occupational therapist explores an intervention

Environmental Control Systems (ECS), enable people with high cervical Spinal Cord Injury (high SCI) to control and access everyday electronic devices. In Ireland, however, access for those who might benefit from ECS is limited. This study used a qualitative approach to explore the insider experience of an ECS starter-pack developed by the author, an occupational therapist. The primary research questions: what is it really like to live with ECS, and what does it mean to live with ECS, were explored using a phenomenological methodology conducted in three phases. In Phase 1 fifteen people with high SCI met twice in four focus groups to discuss experiences and expectations of ECS. Thematic analysis (Krueger & Casey, 2000), influenced by the psychological phenomenological approach (Creswell, 1998), yielded three categories of rich, practical, phenomenological findings: ECS Usage and utility; ECS Expectations and The meaning of living with ECS. Phase 1 findings informed Phase 2 which consisted of the development of a generic electronic assistive technology pack (GrEAT) that included commercially available constituents as well as short instructional videos and an information booklet. This second phase culminated in a one-person, three-week pilot trial. Phase 3 involved a six person, 8-week trial of the GrEAT, followed by individual in-depth interviews. Interpretative Phenomenological Analysis IPA (Smith, Larkin & Flowers, 2009), aided by computer software ATLAS.ti and iMindmap, guided data analysis and identification of themes. Getting used to ECS, experienced as both a hassle and engaging, resulted in participants being able to Take back a little of what you have lost, which involved both feeling enabled and reclaiming a little doing. The findings of this study provide substantial insights into what it is like to live with ECS and the meanings attributed to that experience. Several practical, real world implications are discussed.

Wireless networked control systems with QoS-based sampling

Closing feedback loops using an IEEE 802.11b ad hoc wireless communication network incurs many challenges sensitivity to varying channel conditions and lower physical transmission rates tend to limit the bandwidth of the communication channel. Given that the bandwidth usage and control performance are linked, a method of adapting the sampling interval based on an 'a priori', static sampling policy has been proposed and, more significantly, assuring stability in the mean square sense using discrete-time Markov jump linear system theory. Practical issues including current limitations of the 802.11 b protocol, the sampling policy and stability are highlighted. Simulation results on a cart-mounted inverted pendulum show that closed-loop stability can be improved using sample rate adaptation and that the control design criteria can be met in the presence of channel errors and severe channel contention.

Taking pluralism seriously:Embedded moralities in management accounting and control systems

Professor Norman Macintosh has long been a leading, and at times a dissonant, voice in critical accounting studies, exhibiting an intellectual dexterity seldom encountered in the accounting academy. His work ranges from the application of traditional organizational theories within work organizations to poststructural renderings of capital market exigencies. Here, we consider and extend Professor Macintosh's work contemplating the morality embedded within, and propagated by, management accounting and control systems (macs). We begin with Macintosh (1995) employing structuration theory in investigating the ethics of profit manipulation within large, decentralized corporations. The work highlights the fundamental dialectical contradictions within these work organizations, demonstrates the indeterminacy of traditional ethical reasoning, and shows the extent to which macs provide legitimating underpinnings for management action. We propose to extend the conversation using the tools provided in Macintosh's subsequent work: a Levinasian ethic (Macintosh et al., 2009), and heteroglossic accounting (Macintosh, 2002)—both emerging from his poststructuralist predilections. A Levinasian perspective provides an ontologically grounded ethic, and heteroglossic accounting calls for multiple accountings representing alternative moral voices. A critical dialogic framework is proposed as a theoretic for imagining heteroglossic accounting that takes pluralism seriously by recognizing the reality of irresolvable differences and asymmetric power relationships associated with assorted moral perspectives.