@inproceedings{LeeSchubertHo, author = {Lee, Wai-Kong and Schubert, Martin J. W. and Ho, Stanley Jian-Qin}, title = {Multi-source energy harvesting and storage for floating wireless-sensor-network nodes}, series = {2016 IEEE Industrial Electronics and Applications Conference (IEACon 2016), 20.-22. Nov. 2016, Kota Kinabalu, Malaysia}, booktitle = {2016 IEEE Industrial Electronics and Applications Conference (IEACon 2016), 20.-22. Nov. 2016, Kota Kinabalu, Malaysia}, isbn = {9781509009268}, language = {en} } @article{LeeSchubertOoietal., author = {Lee, Wai-Kong and Schubert, Martin J. W. and Ooi, Boon Yaik and Ho, Stanley Jian-Qin}, title = {Multi-source energy harvesting and storage for floating wireless sensor network nodes with Long Range Communication Capability}, series = {IEEE Transactions on Industry Applications}, volume = {54}, journal = {IEEE Transactions on Industry Applications}, number = {3}, publisher = {IEEE}, doi = {10.1109/TIA.2018.2799}, pages = {2606 -- 2615}, abstract = {Wireless sensor networks are widely used for environmental monitoring in remote areas. They are mainly composed of wireless sensor nodes, usually powered by batteries with limited capacity, but are expected to communicate in long range and operate for extended time periods. To overcome these limitations, many energy harvesting techniques are proposed to power wireless nodes for prolonged operation, whereas multihop techniques are utilized to extend the communication range. In this paper, a novel floating device with multisource energy harvesting technology that can be used as a wireless sensor node is proposed. The long range communication between wireless sensor nodes and a gateway is established through LoRa technology. In addition to conventional solar panels, an energy harvesting technique based on thermoelectric generators exploiting thermal differences created between water surface and materials exposed to sunlight is proposed. Energy generated from photovoltaic and thermoelectric generators is combined to power the wireless sensor node. This floating device consumes 6.6216 Wh per day when used as a wireless sensor node for the collection and transmission of environmental data. The sensor node can operate on a water surface for at least 9.6 days when it is not exposed to sunlight. During a sunny day, the floating device can harvest 8.375 Wh from solar panels and 0.425 Wh from thermoelectric generation. In other words, the floating device harvests sufficient energy to be self-sustaining during sunny days.}, language = {en} } @inproceedings{OoiLeeSchubertetal., author = {Ooi, Boon Yaik and Lee, Wai-Kong and Schubert, Martin J. W. and Ooi, Yu-Wei and Chin, Chee-Yang and Woo, Wing-Hon}, title = {A Flexible and Reliable Internet-of-Things Solution for Real-Time Production Tracking}, series = {IEEE Industrial Electronics and Applications Conference (IEACon): 22.11.2021 - 23.11.2021, Penang, Malaysia}, booktitle = {IEEE Industrial Electronics and Applications Conference (IEACon): 22.11.2021 - 23.11.2021, Penang, Malaysia}, publisher = {IEEE}, isbn = {978-1-7281-9253-6}, doi = {10.1109/IEACon51066.2021.9654672}, pages = {270 -- 275}, abstract = {The concept of Industrial Revolution 4.0 (IR4.0) has sparked the urgency of many manufacturers to revisit their manufacturing processes and search for opportunities to further improved their production output. Unfortunately, it is difficult to improve a process with inadequate data. Many of the SMEs in developing countries are still using manufacturing machines from the yesteryears which do not have computational and connectivity capabilities. Therefore, we developed an end-to-end Internet-of-Things (IoT) solution, which reliably tracks the production performance of manufacturing machines. This paper elaborates on the designs and the rationale behind it. As of the writing of this paper, our IoT system has been deployed in real manufacturing environment and has been running for approximately 90 days on a 24/7 basis without data lost.}, language = {en} } @inproceedings{SchubertLeeOoi, author = {Schubert, Martin J. W. and Lee, Wai-Kong and Ooi, Boon Yaik}, title = {Quantization and Sampling Effects in Fast Digitally Controlled Switch-Mode DC/DC Buck Converters}, series = {2021 IEEE Industrial Electronics and Applications Conference (IEACon): 22.11.2021 - 23.11.2021, Penang, Malaysia}, booktitle = {2021 IEEE Industrial Electronics and Applications Conference (IEACon): 22.11.2021 - 23.11.2021, Penang, Malaysia}, publisher = {IEEE}, isbn = {978-1-7281-9253-6}, doi = {10.1109/IEACon51066.2021.9654272}, pages = {56 -- 61}, abstract = {Software-defined control of DC/DC switch mode power converters features unequaled flexibility compared to analog control. For fast switching converters as recently used for low power applications, digital control may cause steady-state oscillations known as limit cycles. This effect based on a quantized duty cycle is compared to other aberrations such as output ripple voltage, which is inherent to any pulse-width modulator. A distinction is made between DC and AC errors. The latter are divided into synchronous and asynchronous output voltage disturbances. Synchronous AC errors are composed of the switching frequency and its harmonics.}, language = {en} }