Wearable posture measurement units are capable of enabling real-time performance evaluation and providing feedback to end users. This paper presents a wearable feedback prototype designed for freestyle swimming with focus on trunk rotation measurement. The system consists of a nine-degree-of-freedom inertial sensor, which is built in a central data collection and processing unit, and two vibration motors for delivering real-time feedback. Theses devices form a fundamental body area network (BAN). In the experiment setup, four recreational swimmers were asked to do two sets of 4 x 25m freestyle swimming without and with feedback provided respectively. Results showed that real-time biofeedback mechanism improves swimmers kinematic performance by an average of 4.5% reduction in session time. Swimmers can gradually adapt to feedback signals, and the biofeedback control system can be employed in swimmers daily training for fitness maintenance.

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Wireless body area networks (WBANs) have attained increasing popularity as the next generation framework of wearable technologies for human monitoring. Invasive or noninvasive wearable sensors designed in a WBAN are worn to gather vital information. Biofeedback is a recent concept where collected data are used to generate actuation signals in WBANs. Applications can be seen in various areas such as sports (e.g., locomotor velocity) or medicine (e.g., blood pressure measurement). However, since the body is closely regulated, the next generation WBAN technology must be smart enough to react to monitored data. The main aim of this paper is to review the current state of biofeedback and actuation technology on WBANs in terms of its structure, applications, benefits, and control approaches. The emphasis on the specific requirements when applying biofeedback to humans will be highlighted and discussed. Challenges and open research issues will be concluded at the end.

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This paper investigates performance of various controllers on the stabilization of active magnetic bearing system (AMBs). Firstly, since AMBs are inherently open-loop unstable, closed-loop system identification is adopted in order to obtain the model of the system under study. Next, based on the obtained model, Linear Quadratic Gaussian (LQG), PD-like Fuzzy Controller (PD-FLC), PID-like Fuzzy Controller (PID-FLC) andController are designed. These controllers are then coded in C and implemented in real time on both x and y channels at one side of the AMBs via a Digital Signal Processor (DSP). The performance of the designed controllers is compared while the system is stationary and subject to step disturbances and while the system is rotating at high speed. As minimizing energy consumption is one of the obvious desirable objectives to achieve, these different stabilizing controllers are also compared in terms of the resulting control energy. The ultimate aim of this paper is to develop an intuition on how to design high performance stabilizing controllers of open-loop unstable systems like AMBs.