This paper reports on the design and experimental validation of transducers for energy harvesting from largescale
civil structures, for which the power levels can be above 100W, and disturbance frequencies below 1Hz.
The transducer consists of a back-driven ballscrew, coupled to a permanent-magnet synchronous machine, and
power harvesting is regulated via control of a four-quadrant power electronic drive. Design tradeoffs between
the various subsystems (including the controller, electronics, machine, mechanical conversion, and structural
system) are illustrated, and an approach to device optimization is presented. Additionally, it is shown that
nonlinear dissipative behavior of the electromechanical system must be properly characterized in order to assess
the viability of the technology, and also to correctly design the matched impedance to maximize harvested
power. An analytical expression for the average power generated across a resistive load is presented, which takes
the nonlinear dissipative behavior of the device into account. From this expression the optimal resistance is
determined to maximize power for an example in which the transducer is coupled to base excited tuned mass
damper (TMD). Finally, the results from the analytical model are compared to an experimental system that uses
hybrid testing to simulated the dynamics of the TMD.
Wave motions represent a source of substantial untapped energy. Given the current interest in renewable power, research
continues into the development of wave energy harvesting devices.
An evaluation of existing wave energy harvester designs has shown that there are a number of different methods
typically used to carry out the mechanical-to-electrical energy conversion process. A common observation is that
existing designs only use a subset of possible wave motions to generate electrical energy; while heaving motions are
commonly used, other forms of translational and rotational motion such as swaying, pitching and rolling remain
This paper evaluates the feasibility of a multidimensional wave energy harvester that is able to harvest electrical energy
using six degrees-of-freedom. A design for an inertial energy harvesting system is presented, with a suspended proof
mass and electromagnetic transducers allowing energy to be harvested from multiple translational and rotational wave motions. A computer-based model of the system is created, allowing the performance of the device to be simulated for a given set of wave motions. Using real-world wave data captured by a data logging buoy, a peak electrical power output in excess of 600mW is obtained.
Personal electronic devices such as cell phones, GPS and MP3 players have traditionally depended on battery energy
storage technologies for operation. By harvesting energy from a person's motion, these devices may achieve greater run
times without increasing the mass or volume of the electronic device. Through the use of a flexible piezoelectric
transducer such as poly-vinylidene fluoride (PVDF), and integrating it into a person's clothing, it becomes a 'wearable
transducer'. As the PVDF transducer is strained during the person's routine activities, it produces an electrical charge
which can then be harvested to power personal electronic devices.
Existing wearable transducers have shown great promise for personal motion energy harvesting applications. However,
they are presently physically bulky and not ergonomic for the wearer. In addition, there is limited information on the
energy harvesting performance for wearable transducers, especially under realistic conditions and for extended cyclic
force operations - as would be experienced when worn. In this paper, we present experimental results for a wearable
PVDF transducer using a person's measured walking force profile, which is then cycled for a prolonged period of time
using an experimental apparatus. Experimental results indicate that after an initial drop in performance, the transducer energy harvesting performance does not substantially deteriorate over time, as less than 10% degradation was observed. Longevity testing is still continuing at CSIRO.
Seventy percent of the Earth's surface is covered by water and all living things are dependent upon this resource. As
such there are many applications for monitoring environmental data in and around aquatic environments. Wireless sensor
networks are poised to revolutionise this process as the reduction in size and power consumption of electronics are
opening up many new possibilities for these networks. Aquatic sensor nodes are usually battery powered, so as sensor
networks increase in number and size, replacement of depleted batteries becomes time consuming, wasteful and in some
cases unfeasible. Additionally, a battery that is large enough to last the life of a sensor node would dominate the overall
size of the node, and thus would not be very attractive or practical. As a result, there is a clear need to explore novel
alternatives to power sensor nodes/networks, as existing battery technology hinders the widespread deployment of these
networks. By harvesting energy from their local environment, sensor networks can achieve much greater run-times, years
not months, with potentially lower cost and weight. A potential renewable energy source in aquatic environments exists
via the temperature gradient present between the water layer and ambient air. A body of water will be either a few
degrees warmer or colder than the air directly above it dependant on its latitude, time of year and time of day. By
incorporating a thermal energy harvesting device into the sensor node deployment which promotes the flow of heat
energy across the thermal gradient, a portion of the energy flow can be converted into useable power for the sensor node.
To further increase this temperature difference during the day the top section can be heated to temperatures above the
ambient air temperature by absorbing the incoming sunlight. As an initial exploration into the potential of this novel
power source we have developed a model of the process. By inputting environmental data, the model calculates the
power which can be extracted by a thermal energy harvesting device. Initial outputs show a possibility of up to 10W/m2
of power available from measured sites assuming a thermal energy harvester operating with Carnot efficiency.
Personal electronic devices such as mobile/cell phones, radios and wireless sensors traditionally depend on energy
storage technologies, such as batteries, for operation. By harvesting energy from the local environment, these devices can
achieve greater run-times without the need for battery recharging or replacement. Harvesting energy could also achieve a
reduction in the weight and volume of the personal devices - as batteries often make up more than half the
weight/volume of these devices. Motion energy harvesting is one such approach where energy from mechanical motion
can be converted into electrical energy. This can be achieved through the use of flexible piezoelectric transducer
materials such as polyvinylidene fluoride (PVDF). A problem with these transducer materials it that their behaviour is
non-linear due to operating and environmental conditions. Hence, for this reason researchers have found it has been
difficult to measure the harvesting performance i.e. mechanical-to-electrical conversion efficiency. At CSIRO we are
currently evaluating the performance of flexible transducers for use as motion energy harvesters. Preliminary results
suggest an overall energy harvesting conversion efficiency of 0.65% for a flexible transducer material.
By scavenging energy from their local environment, portable electronic devices such as mobile phones, radios
and wireless sensors can achieve greater run-times with potentially lower weight. Vibration energy harvesting is
one such approach where energy from parasitic vibrations can be converted into electrical energy, through the
use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as
wind, seismic forces and traffic.
Existing approaches to vibration energy harvesting typically utilise a rectifier circuit, which is tuned to the
resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a
novel approach to vibration energy harvesting, including adaption to non-periodic vibrations so as to extract
the maximum amount of vibration energy available. Experimental results of an experimental apparatus using
off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies
of 27 - 34%. However, simulations of a more electro-mechanical efficient and lightly damped transducer show
conversion efficiencies in excess of 80%.
Reliable power sources are needed for portable micro-electromechanical systems (MEMS) devices such as wireless
automobile tire pressure sensors. Vibration is an ubiquitous energy source that maybe 'harvested' as electrical
energy at the site of the MEMS device. Existing vibration energy harvesting systems use either a piezoelectric
or an electromagnetic transducer to convert vibrations into electrical energy. This electrical energy is then
conditioned using a passive rectifier dc-dc converter circuit. Such vibration harvesting techniques have focused on
optimising circuit efficiency and, hence, have ignored the system efficiency i.e. mechanical-to-electrical efficiency.
Results obtained in the laboratory can be extrapolated to predict potential system efficiencies for MEMS
vibration energy harvesting systems. Results to date, using a standard speaker as the electromagnetic transducer,
have demonstrated system efficiencies of greater than 14%. Initial estimates suggest a MEMS system efficiency
of more than 80% could be achieved with a high performance transducer. Research is continuing to demonstrate
these higher system efficiencies with the experimental apparatus.
By attaching an electromagnetic transducer to a mechanical isolation system and shunting the terminals of the transducer with electrical impedance, we can provide improved isolation performance while eliminating the need for an additional sensor. Simulated and experimental results on a simple electro-mechanical isolation system show that the proposed controller is capable of peak damping and high frequency attenuation.
Passive shunt damping involves the connection of an electrical shunt network to a structurally attached piezoelectric transducer. In recent years, a large body of research has focused on the design and implementation of shunt circuits capable of significantly reducing structural vibration. This paper introduces an efficient, light weight, and small-in-size technique for implementing piezoelectric shunt damping circuits. A MOSFET half bridge is used together with a signal processor to synthesize the terminal impedance of a piezoelectric shunt damping circuit. Along with experimental results demonstrating the effectiveness of switched-mode shunt implementation, we discuss the design of a device aimed at bridging the gap between research in this area and practical application.
This paper introduces electromagnetic shunt damping (EMSD) which is similar to piezoelectric shunt damping. EMSD has four major advantages over piezoelectric shunt damping; simple transducer manufacturing, smaller shunt voltages, long stroke and larger control forces. A novel single mode shunt control strategy is validated through experimentation on a simple electromagnetic mass spring damper system. Theoretical results are also presented.
This paper introduces a new multiple mode passive piezoelectric shunt damping technique. The robust passive piezoelectric shunt controller is capable of damping multiple structural modes and maybe less susceptible to variations in environmental conditions that can severely effect the performance of other controllers. The proposed control scheme is validated experimentally on a piezoelectric laminated plate structure.
This paper introduces a passive piezoelectric shunt controller, for damping multiple modes of a flexible structure using one piezoelectric transducer. The series-parallel impedance structure has a number of advantages over to previous techniques; it is simpler to implement, requires less passive elements and contains smaller inductors values. The vibration control strategy is validated through experimental work on a piezoelectric laminated cantilever structure.
This paper introduces a new type of passive piezoelectric shunt controller which is capable of damping multiple modes of a flexible structure using one piezoelectric transducer. The current flowing shunt technique has a number of advantages over comparable techniques; it is simpler to implement and requires less discrete circuit elements. The passive control strategy is validated through experimental work on a piezoelectric laminated simply supported beam.
A new multi-mode semi-active shunt technique for controlling vibration in piezoelectric laminated structures is proposed in this paper. The effect of the ``negative capacitor'' controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply-supported beam. The negative capacitor controller is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen multiple modes. While achieving comparable performance to that of the purely piezoelectric passive shunt schemes, the negative capacitor controller has a number of advantages. It is simpler to implement, less sensitive to environmental variations, and can act as a multiple mode and broadband vibration controller. Experimental resonant amplitudes for the piezoelectric laminated simply-supported beam 1st, 2nd, 3rd, 4th and 5th modes were successfully reduced by 6.1, 16.3, 15.2, 11.7 and 10.2dB.
Piezoelectric transducer (PZT) patches can be attached to a structure in order to reduce vibration. The PZT patches essentially convert vibrational mechanical energy into electrical energy. The electrical energy can be dissipated via an electrical impedance. Currently, impedance designs require experimental tuning of resistance values by minimizing the H2 norm of the damped system. After the design process, shunt circuits are normally implemented using discrete reasonable performance has been an ongoing and unaddressed problem in shunt damping. A new approach to implementing piezoelectric shunt circuits is presented. A synthetic impedance, consisting of a voltage controlled circuit source and DSP system, is used to synthesize the terminal impedance of a shunt network. A two mode shunt circuit is designed and implemented for an experimental simply supported beam. The second and third structural modes of the beam are reduced in magnitude by 22 and 18 dB.