Towards self-powered sensing using nanogenerators for automotive systems

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.nanoen.2018.09.032 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Harvesting energy from the working environment of vehicles is important for wirelessly monitoring their operation conditions and safety. This review aims at reporting different sensory and energy harvesting technologies developed for automotive and active safety systems. A few dominant sensing and power harvesting mechanisms in automotive systems are illustrated, then, triboelectric, piezoelectric and pyroelectric nanogenerators, and their potential for utilization in automotive systems are discussed considering their high power density, flexibility, different operating modes, and cost in comparison with other mechanisms. Various ground vehicles’ sensing mechanisms including position, thermal, pressure, chemical and gas composition, and pressure sensors are presented. A few novel types self-powered sensing mechanisms are presented for each of the abovementioned sensor categories using nanogenerators. The last section includes the automotive systems and subsystems, which have the potential to be used for energy harvesting, such as suspension and tires. The potential of nanogenerators for developing new self-powered sensors for automotive applications, which in the near future, will be an indispensable part of the active safety systems in production cars, is also discussed in this review article

A comprehensive review of the techniques on regenerative shock absorber systems

In this paper, the current technologies of the regenerative shock absorber systems have been categorized and evaluated. Three drive modes of the regenerative shock absorber systems, namely the direct drive mode, the indirect drive mode and hybrid drive mode are reviewed for their readiness to be implemented. The damping performances of the three different modes are listed and compared. Electrical circuit and control algorithms have also been evaluated to maximize the power output and to deliver the premium ride comfort and handling performance. Different types of parameterized road excitations have been applied to vehicle suspension systems to investigate the performance of the regenerative shock absorbers. The potential of incorporating nonlinearity into the regenerative shock absorber design analysis is discussed. The research gaps for the comparison of the different drive modes and the nonlinearity analysis of the regenerative shock absorbers are identified and, the corresponding research questions have been proposed for future work

Hybrid Electromagnetic Vibration Isolation Systems

Traditionally, dynamic systems are equipped with passive technologies like viscous shock absorbers and rubber vibration isolators to attenuate disturbances. Passive elements are cost effective, simple to manufacture, and have a long life span. However, the dynamic characteristics of passive devices are fixed and tuned for a set of inputs or system conditions. Thus in many applications when variation of input or system conditions is present, sub-optimal performance is realized. The other fundamental flaw associated with passive devices is that they expel the undesired kinetic energy as heat. Recently, the introduction of electromagnetic technologies to the vibration isolation systems has provided researchers with new opportunities for realizing active/semi-active vibration isolation systems with the additional benefit of energy regeneration (in semi-active mode). Electromagnetic vibration isolators are often suffer from a couple of shortcomings that precludes their implementations in many applications. Examples of these short comings include bulky designs, low force density, high energy consumption (in active mode), and fail-safe operation problem. This PhD research aims at developing optimal hybrid-electromagnetic vibration isolation systems to provide active/semi-active and regenerative vibration isolation for various applications. The idea is to overcome the aforementioned shortcomings by integrating electromagnetic actuators, conventional damping technologies, and stiffness elements into single hybrid packages. In this research, for both semi-active and active cases, hybrid electromagnetic solutions are proposed. In the first step of this study, the concept of semi-active hybrid damper is proposed and experimentally tested that is composed of a passive hydraulic and a semi-active electromagnetic components. The hydraulic medium provides a bias and fail-safe damping force while the electromagnetic component adds adaptability and energy regeneration to the hybrid design. Based on the modeling and optimization studies, presented in this work, an extended analysis of the electromagnetic damping component of the hybrid damper is presented which can serve as potent tool for the designers who seek maximizing the adaptability (and regeneration capacity) of the hybrid damper. The experimental results (from the optimized design) show that the damper is able to produce damping coefficients of 1300 and 0-238 Ns/m through the viscous and electromagnetic components, respectively. In particular, the concept of hybrid damping for the application of vehicle suspension system is studied. It is shown that the whole suspension system can be adjusted such that the implementation of the hybrid damper, not only would not add any adverse effects to the main functionally of the suspension, but it would also provide a better dynamics, and enhance the vehicle fuel consumption (by regenerating a portion of wasted vibration energy). In the second step, the hybrid damper concept is extended to an active hybrid electromagnetic vibration isolation systems. To achieve this target, a passive pneumatic spring is fused together with an active electromagnetic actuator in a single hybrid package. The active electromagnetic component maintains a base line stiffness and support for the system, and also provides active vibration for a wide frequency range. The passive pneumatic spring makes the system fail-safe, increases the stiffness and support of the system for larger masses and dead loads, and further guarantees a very low transmissibility at high frequencies. The FEM and experimental results confirmed the high force density of the proposed electromagnetic component, comparing to a voice coil of similar size. In the proposed design, with a diameter of ~125 mm and a height of ~60 mm, a force variation of ~318 N is obtained for the currents of I=±2 A. Furthermore, it is demonstrated that the proposed actuator has a small time constant (ratio of inductance to resistance for the coils) of less than 5.2 ms, with negligible eddy current effect, making the vibration isolator suitable for wide bandwidth applications. According to the results, the active controllers are able to enhance the performance of the passive elements by up to 80% and 95% in terms of acceleration and force transmissibilities, respectively

A study of vehicle electromagnetic regenerative shock absorber

The technology of energy harvesting from shock absorber has become more promising over the years with a potential for implementation. The aim of the research is to improve the energy harvesting ability of the regenerative shock absorber and evaluate its feasibility operating in the real road condition on the vehicle. This thesis consists of 7 chapters to address the research questions raised from the existing research gaps based on the literature reviews: 1. How can the performance of the electromagnetic energy harvester in 2DOF system be improved? 2. For the direct drive and indirect drive regenerative shock absorbers, which one has better performance? 3. How can the half vehicle model with regenerative shock absorbers be modelled for the premium energy harvesting performance? In order to answer the research questions, firstly a 2 degrees of freedom oscillating system resembling the quarter vehicle suspension system is constructed with the electromagnetic harvester and validated by the simulation model. It is found that the peak power output occurs at natural frequency. Base excitation amplitude and external resistance can also affect the system power output. As for the energy harvester, better energy harvesting performance can be achieved through two factors: coil speed with respect to the magnets and the electro-mechanical coupling constant. The double speed mechanism can increase the coil speed with respect to the magnets and is applied on a design of novel regenerative shock absorber. It is found that increasing the coil speed with respect to the magnets for 2 times can result in increasing the power output by 4 times. A novel indirect drive regenerative shock absorber with the arm-teeth system is also designed and fabricated to answer the second research question. The results show 2 that the power output can be substantially increased compared with the traditional direct drive regenerative shock absorber. It is also found that the arm-teeth system makes the regenerative shock absorber more sensible to parameter optimization and has the potentials to increase the energy harvesting bandwidth. As the response to research question three, a half vehicle suspension system model is established with two indirect drive regenerative shock absorbers. The Taguchi method is unitized for the parameter optimization. With the application of the random road excitation displacement amplitude, the optimized model can harvest more energy than the non-optimized model when the vehicle is driving on the Class A, Class C and Class E road. Lastly a full vehicle suspension system model is developed as an extension to the half vehicle suspension system model. It is found that at high frequency range, the peak power output ratio of full vehicle suspension system is same as that of the half and quarter vehicle suspension system. The advantages of the full vehicle suspension system are more obvious at low frequency range or when the vehicle is driving on the off-road condition