Backpack energy harvester managed by a modified fly-back converter
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Backpack energy harvester managed by a modified fly-back converter W.-W. Yen1 • Paul C.-P. Chao1 Received: 31 October 2020 / Accepted: 10 November 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A backpack energy harvester (EH) managed by a modified fly-back converter is proposed. This modified fly-back converter is controlled by a constant-on time control (COT) algorithm, The COT is one of pulse frequency modulation schemes, which switches in boundary conduction mode. Due to the structure of the modified fly-back converter and the alternator, the energy delivery to battery is proportional to the voltage of coupled capacitor. As opposed to the conventional fly-back, the proposed modified fly-back has the metal–oxide–semiconductor field-effect transistor and the capacitor exchanged in roles to achieve input rectified voltage sensing. Moreover, the proposed modified fly-back converter utilizes the internal winding inductance of the alternator utilized as part of the fly-back converter, to save the size of the converter circuitry and lower the cost. With the COT control strategy, the output power is estimated by measuring the capacitor voltage, which is converted to digitals by a 10-bit analog-to-digital converter and a time-to-digital converter. The results show clearly the fair linearity between the rotational speed of alternator, capacitor voltage and output power. Finally, the control algorithm of boundary conduction mode (BCM) is utilized for tackling well the intermittent input power generated by the EH. The average output powers of 1.166 W for striding and 1.766 W for jogging are successfully achieved.
1 Introduction Portable devices nowadays become popular as the technology internet of things (IoT) emerges. Capacity of battery also increases significantly with the growth of the portable device. Thus, to extend capacity of battery, biomechanical energy harvester (EH) gets attention in past century (Harman et al. 2000; Donelan et al. 2008; Rome 2005; Rubinshtein et al. 2014; Xie et al. 2016). Among them, backpack EH, a kind of mass-spring-damping oscillating system, not only generates the power to supply portable devices but also reduces the risk of orthopaedic and muscular injury (Harman et al. 2000; Rome et al. 2006; Mi et al. 2018). The peak accelerative force is reduced and is converted into electrical energy by backpack EH while human motion. In these studies (Harman et al. 2000; Andrade et al. 2015), the effect of backpack load has been discussed in human motion. The effects of four backpack loads performed on 16 male volunteers were analyzed on walking gait (Harman et al. 2000). The angles of hip and
& W.-W. Yen [email protected] 1
Institute of Electrical and Control Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
knee were tested in backpack weighing 0%, 10%, 15% and 20% of volunteer’s body weight (Andrade et al. 2015). In these references (Rome et al. 2006, Mi et al. 2018; Yang et al. 2012; Park et al. 2
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