Though there exist numerous researches concentrating on theoretical modelling of an electret-based vibration energy harvester (eVEH) connected with a pure load resistor, holistic modelling of eVEH with DC interface circuits is rarely studied. In this paper, a theoretical model of the eVEH connected to a DC interface circuit with a full bridge rectifier is proposed and validated by simulation and experiment. The power loss of eVEHs due to the reverse current leakage of diodes in the rectifier is investigated. The results show that the diodes with large reverse current are not recommended to construct the rectifier for eVEHs, due to the large impendence feature of the eVEH.
A piezoelectric metamaterial beam is proposed in this paper for both vibration suppression and energy harvesting. Additional springs are introduced to create internal coupling alternately between local resonators. Each resonator is associated with a piezoelectric element for producing electrical energy. First, the mathematical model of the piezoelectric metamaterial beam is developed. The analytical solutions of the transmittance of the system and the open-circuit voltage responses of the piezoelectric elements are derived. As compared to the conventional counterpart without internal coupling, it is found that the energy harvesting performance is significantly reinforced in the low frequency range and the vibration suppression performance is slightly enhanced due to the appearance of an additional band gap. Subsequently, an equivalent finite element model – model A for verifying analytical solutions is developed. The lumped local resonators in the analytical model are modelled by using cantilevers with tip masses in the finite element model. The tip masses are alternately coupled with one-dimensional two-node spring elements. The finite element analysis results show good agreement with the analytical results for both the transmittance of the system and the open-circuit voltage responses of the piezoelectric elements. Finally, a model B with a more practical realization of the internal coupling is established. The coupling spring is replaced by a beam connection. The finite element analysis results show that the behavior of model B is different from model A and is not equivalent to the proposed analytical model. No significant enhancement in terms of energy harvesting is observed but a remarkably enhanced vibration suppression performance appears in model B. The difference between the two models is then discussed.
In this paper, we present a simple printing method for a highly resilient stretch sensor. The stretch sensors, based on multi-walled carbon nanotubes (MWCNT)/silicon rubber (Ecoflex® 00-30) polymer nanocomposites, were printed on silicon rubber (SR) substrate. The sensors exhibit good hysteresis with high linearity and small drift. Due to the biocompatibility of SR and is very soft, strong and able to be stretched many times its original size without tearing and will rebound to its original form without distortion, the proposed stretch sensor is suitable for many biomedical and wearable sensors application.
A robotic surgical device, actuated by Ionic Polymer-metal Composite (IPMC), integrated with a strain gauge to achieve force control is proposed. Test results have proved the capabilities of this device to conduct surgical procedures. The recent growth of patient acceptance and demand for robotic aided surgery has stimulated the progress of research where in many applications the performance has been proven to surpass human surgeons. A new area which uses the inherently force compliant and back-drivable properties of polymers, IPMC in this case, has shown its potential to undertake precise surgical procedures in delicate environments of medical practice. This is because IPMCs have similar actuation characteristics to real biological systems ensuring the safety of the practice. Nevertheless, little has been done in developing IPMCs as a rotary joint actuators used as functional surgical devices. This research demonstrates the design of a single degree of freedom (1DOF) robotic surgical instrument with one joint mechanism actuated by IPMC with an embedded strain gauge as a feedback unit, and controlled by a scheduled gain PI controller. With the simplicity of the system it was proven to be able to cut to the desired controlled force and hence depth.
A novel flexible strain sensor was developed using a conducting polymer coated on rubber for large strain
measurements. A coating of the conducting polymer, polypyrrole, was deposited on a strip of natural rubber through the
process of vapour phase polymerisation while the rubber is in a stretched state. This process involves depositing a layer
of oxidant on the rubber surface, followed by exposure to pyrrole monomer vapours that polymerize on the oxidantcoated
rubber to produce polypyrrole.
The change in electrical resistance of the strain sensor was recorded while cyclic strain from 0% to 20% was exerted on
it. The gauge factor of the strain sensor was calculated to be 1.86. From repeated electrical resistance-strain
measurements, the repeatability of the strain sensor was studied. A hysteresis was observed in a single extensionretraction
strain cycle. Further study showed that the observed hysteresis is dependent on the strain rate where lower
strain rate resulted in higher hysteresis and vice versa for a higher strain rate. There is also an electrical resistance drift
between consecutive extension-retraction cycles.
Owing to the flexibility of the rubber, the strain sensor can be used in complex configurations. The strain sensor can also
be mounted or attached directly on surfaces to provide low-profile installation where space constraint is an issue. These
characteristics offer advantages over traditional strain sensors to be used in applications that were not previously
The demand for single cell manipulation to allow scientist to carry out medical researcher is fast increasing. To facilitate
this advanced manipulation systems are required to permit both precise and safe handling of the biological cells. Current
devices can achieve a high level of precision at the micro/nano scale but as a consequence are highly rigid and this
stiffness puts the target cells at risk as there is no compliance or back-drivability. Ionic polymer-metal composites
(IPMCs) are naturally compliant, giving them a 'soft touch', and now with recent advances in their fabrication and
control IPMCs are showing major promise as safe and accurate cell manipulators. This paper presents the development
of an optimally tuned force controller for a 2 degree-of-freedom (2DOF) IPMC actuated micro-manipulator. The control
system has been implemented to demonstrate the ability to control the manipulator's applied force as a step towards
implementing a truly safe system with active compliance control. The controller is adaptively tuned using a model-free
iterative feedback tuning (IFT) approach which is ideal for operation in unknown cellular environments as well as for
controlling the complex time-varying behavior of the IPMC actuators themselves. The IFT algorithm tunes the force
controller by minimizing the design criteria, a least squares error, by 25% in the horizontal direction and 46% in the
vertical direction. Experiments then show that the manipulator can accurately track a reference trajectory up to 4gf or
~40mN in both DOF.
This paper presents the design, fabrication and experimental characterization of a valveless micropump actuated by an
ionic-polymer-metal-composite (IPMC) soft actuator. The performance of the IPMC varies over time, therefore on-line
iterative feedback tuning (IFT) is used to adaptively tune the PID controller to control the bending deflection of the
IPMC to ensure a constant pumping rate. The pump rate is higher at lower frequencies for a given applied voltage to the
IPMC. A maximum flow rate of 130 μl/min is achieved at 0.1 Hz.
A novel flexible large strain sensor was developed to be use with an air muscle. A piece of butyl rubber was coated with
the conducting polymer, polypyrrole through bulk solution and chemical vapour deposition method. The strain sensor
was able to response to sudden movements represented by the multiple step functions of the applied strain. Consistency
of the sensor's output was studied and the average error in the change of resistance was calculated to be 0.32% and
0.72% for elongation and contraction respectively for the sample made using chemical vapour deposition. However, a
hysteresis was observed for this sample for a single cycle of elongation and contraction with the highest error calculated
to be 3.2% at a 0% applied strain. SEM images showed the propagation of surface micro-cracks as the cause of the
variation in surface resistance with applied strain. In addition, slower relaxation rate of the rubber prevented the surface
micro-cracks to open and close at the same rate. The idea of utilizing conducting polymer coating can be applied to the
inner rubber tube of the air muscle. As such, a complete integration between actuator and sensor can be realized.
Ionic Polymer Metallic Composite (IPMC) is a smart material that can be used to make sensors for various applications.
This paper investigates the use of IPMC for sensing the motion of a rotary joint. In this research, the relationship
between the motion of a rotary joint and the IPMC sensor's voltage output was investigated and modeled. The
relationships defining the sensor's response were developed into a routine which was used to calculate the bending angle
and bending speed of a joint, based on the voltage response of an IPMC sensor. Experimental verification of the model
produced results for measuring bending angles with an accuracy of within 3% across most of the range of angles. The
accuracy of the measured bending speed was found to be related to the joint motion; with errors ranging from 0.4% at a
slow bending speeds ( ≤150°s-1) up to an error of ~8% at fast bending speeds ( ≥ 200°s-1). Additional variables such as
bending direction and starting position were also investigated to determine their effects on the sensor's response. It is
concluded that the methods developed in this study provide a more complete description of the relationship between
IPMC sensor voltage and joint motion than has previously been documented.
Ionic Polymer Metal Composite (IPMC) materials are bending actuators that can achieve large tip displacements at
voltages less than 10V, but with low force output. Their advantages over traditional actuators include very low mass and
size; flexibility; direct conversion of electricity to mechanical energy; biocompatibility; and the potential to build
integrated sensing/actuation devices, using their inherent sensing properties. It therefore makes sense to pursue them as a
replacement to traditional actuators where the lack of force is less significant, such as micro-robotics; bio-mimetics;
medical robotics; and non-contact applications such as positioning of sensors. However, little research has been carried
out on using them to drive mechanisms such as the rotary joints. This research explores the potential for applying IPMC
to driving a single degree-of-freedom rotary mechanism, for a small-force robotic manipulator or positioning system.
Practical issues such as adequate force output and friction are identified and tackled in the development of the
mechanical apparatus, to study the feasibility of the actuator once attached to the mechanism. Rigid extensions are then
applied to the tip of the IPMC, as well as doubling- and tripling the actuators in a stack to increase force output. Finally,
feasibility of the entire concept is considered by comparing the maximum achievable forces and combining the actuator
with the mechanism. It is concluded that while the actuator is capable of moving the mechanism, it is non-repeatable and
does not achieve a level that allows feedback control to be applied.