Low-power Actuators Research Articles

Improving Walking Energy Efficiency in Transtibial Amputees Through the Integration of a Low-Power Actuator in an ESAR Foot.

Reducing energy consumption during walking is a critical goal for transtibial amputees. The study presents the evaluation of a semi-active prosthesis with five transtibial amputees. The prosthesis has a low-power actuator integrated in parallel into an energy-storing-and-releasing foot. The actuator is controlled to compress the foot during the stance phase, supplementing the natural compression due to the user's dynamic interaction with the ground, particularly during the ankle dorsiflexion phase, and to release the energy stored in the foot during the push-off phase, to enhance propulsion. The control strategy is adaptive to the user's gait patterns and speed. The clinical protocol to evaluate the system included treadmill and overground walking tasks. The results showed that walking with the semi-active prosthesis reduced the Physiological Cost Index of transtibial amputees by up to 16% compared to walking using the subjects' proprietary prosthesis. No significant alterations were observed in the spatiotemporal gait parameters of the participants, indicating the module's compatibility with users' natural walking patterns. These findings highlight the potential of the mechatronic actuator in effectively reducing energy expenditure during walking for transtibial amputees. The proposed prosthesis may bring a positive impact on the quality of life, mobility, and functional performance of individuals with transtibial amputation.

Conceptual design of a new experimental setup to simulate aircraft tyre spin-up dynamics

PurposeThe first touchdown moment of aircraft tyres on a runway is the critical phase where maximum of the vertical and horizontal ground loads is produced. Some valuable drop tests have been performed at Langley research centre to simulate the touchdown and the spin-up dynamics. However, a long impact basin and a huge power source to accelerate and decelerate the landing gear mechanism have been used. Based on a centrifugal mechanism, the purpose of this paper is to propose the conceptual design of a new experimental setup to simulate the spin-up dynamics.Design/methodology/approachA schematic view of the proposed mechanism is presented, and its components are introduced. Operating condition of the system and the test procedure are discussed in detail. Finally, tyre spin-up dynamics of Boeing 747 is considered as a case study, and operating condition of the system and the related test parameters are extracted.FindingsIt is shown that the aircraft tyre spin-up dynamics can be simulated in a limited laboratory space with low energy consumption. The proposed setup enables the approach velocity, sink rate and vertical ground load to be adjusted by low power actuators. Hence, the proposed mechanism can be used to simulate the tyre spin-up dynamics of different types of aircraft.Research limitations/implicationsIt is important to note that more details of the setup, including the braking and actuating mechanisms together with their control procedures, should be clarified in practice. In addition, the curved path introduced as the runway will cause errors in the results. Hence, a compromise should be made between the tyre pressure, path curvature, the induced error and the cost of the experimental setup.Practical implicationsThe proposed experimental setup could be constructed in a limited space and at a relatively low cost. Low power actuators are used in the proposed system. Hence, in addition to the performance tests, fatigue tests of the landing gear mechanism will also be possible.Originality/valueBased on a centrifugal mechanism, the conceptual design of a new experimental setup is presented for simulating the tyre spin-up dynamics of aircraft. Considering that the drag load developed during tyre spin-up following initial touchdown is an important factor governing the design of the landing gear mechanism and aircraft structure, the authors hope this paper encourages engineers to continuously make efforts to increase the transparency of the touchdown process, enabling optimisation of landing gear design.

Design and validation of a low-cost, low-power, clockwork insulin pump

A novel, low-cost (≤ NZ$500), and low-power (12 month estimated battery life) insulin pump prototype is presented. The device aims to increase insulin pump uptake by offering a 9-17 times reduction in pump cost, by limiting the inconvenience and economic constraints of pump treatment. Low-cost is achieved by offloading computation from the pump to a smart device via Bluetooth. An innovative pumping mechanism enables long battery life, with all power required to deliver insulin provided by a spring. A clockwork escapement mechanism is integrated with a low-power actuator to provide dosage control. The accuracy of the novel design was assessed using in-vitro testing to IEC Standard 60601-2-24 (2012) and was benchmarked against two commercial insulin pumps. The clockwork pump achieves similar accuracy to the commercial devices for boluses of 0.005 ml, 0.01 ml, and 0.05 ml, with mean errors < 5%. Consistent over-delivery reduces the accuracy of the clockwork pump at the minimum bolus volume of 0.001 ml (8.1% mean error). For all basal rates tested (0.001 ml h−1, 0.005 ml h−1, and 0.01 ml h−1), the clockwork pump demonstrates similar accuracy and improved consistency compared to commercial devices. Redesigning with higher precision hardware will improve pump accuracy, enabling comparable performance to commercial pumps across all boluses and basal rates. The standards-based testing validates the novel pump concept and justifies further development.

Design and analysis of optical nano electro-mechanical-system-based logic circuits relied on movable waveguides

An approach based on optical nano electro-mechanical-system (NEMS) switches is proposed in this paper to develop low-power logic circuits and processors. Based on the specific logic tasks expressed by sum-of-products (SOP) expressions, an array of switches can be appropriately arranged to implement various logic circuits. The logical output can be detected by translating the presence or absence of the light in the optical guided mode, which is controlled by the displacement of NEMS actuators under electrostatic forces. Therefore, to show the universality of the proposed method and its capability to extend processor circuits, the operation of a MUX (2:1) is analyzed. Furthermore, the presented switch’s functional characteristics and the logic circuits’ optical performance are obtained using the Finite Element Method (FEM) and Finite Difference Time Domain (FDTD) approaches. According to simulation results, the properties of the proposed switch, such as the operating voltage and the switching time, are 12 V and 2.6 μs, respectively. Consequently, the proposed fast and low-power actuator can be a promising choice for realizing low-power digital circuits, especially in the design of NEMS processors for low-power applications because of the significant reduction in its power consumption and immunity against electromagnetic radiation.

Design and Analysis of Ultra-Precise Large Range Linear Motion Platforms Using Compliant Mechanism

Double parallelogram compliant mechanism (DPCM) is extensively used to obtain precise straight-line motion. Symmetric DPCMs, used previously, traverse a straight-line path without parasitic error when gravity vector is perpendicular to the plane of bending of beams. However, when gravity vector is either in line with beams (orientation B) or in the plane of bending of beams (orientation C), asymmetry in the loading causes undesired deviation from a straight-line path. This undesired deviation called parasitic error increases, especially in beams with relatively low flexural rigidity required to obtain larger displacements with low power actuators. This paper first characterizes parasitic error, in such cases, using large deformation analysis and further proposes novel ways to minimize it. A recently developed, chained beam constraint method is used to model, characterize, and optimize DPCMs. Optimized parameters are further validated by FEA and experiments. In orientation B, after implementing the proposed method, numerical analysis and experimental results show that the undesired parasitic error of 123 &#x03BC;m is drastically reduced to 2 &#x03BC;m and 6 &#x03BC;m, respectively. Moreover, systematic design procedure with corresponding graphs is presented to avoid modeling and optimization steps for a user-specific case. The proposed methods pave pathways to reducing the parasitic error during large-range motion using multiple orientations of DPCMs and thus make DPCMs more employable in several precision motion applications such as 3D optical scanners, 3D micro-printers, CMM probes, and microscopy stages.

A cerebellar-based solution to the nondeterministic time delay problem in robotic control

The presence of computation and transmission-variable time delays within a robotic control loop is a major cause of instability, hindering safe human-robot interaction (HRI) under these circumstances. Classical control theory has been adapted to counteract the presence of such variable delays; however, the solutions provided to date cannot cope with HRI robotics inherent features. The highly nonlinear dynamics of HRI cobots (robots intended for human interaction in collaborative tasks), together with the growing use of flexible joints and elastic materials providing passive compliance, prevent traditional control solutions from being applied. Conversely, human motor control natively deals with low power actuators, nonlinear dynamics, and variable transmission time delays. The cerebellum, pivotal to human motor control, is able to predict motor commands by correlating current and past sensorimotor signals, and to ultimately compensate for the existing sensorimotor human delay (tens of milliseconds). This work aims at bridging those inherent features of cerebellar motor control and current robotic challenges—namely, compliant control in the presence of variable sensorimotor delays. We implement a cerebellar-like spiking neural network (SNN) controller that is adaptive, compliant, and robust to variable sensorimotor delays by replicating the cerebellar mechanisms that embrace the presence of biological delays and allow motor learning and adaptation.

Shape Memory Alloy (SMA) Actuator With Embedded Liquid Metal Curvature Sensor for Closed-Loop Control.

We introduce a soft robot actuator composed of a pre-stressed elastomer film embedded with shape memory alloy (SMA) and a liquid metal (LM) curvature sensor. SMA-based actuators are commonly used as electrically-powered limbs to enable walking, crawling, and swimming of soft robots. However, they are susceptible to overheating and long-term degradation if they are electrically stimulated before they have time to mechanically recover from their previous activation cycle. Here, we address this by embedding the soft actuator with a capacitive LM sensor capable of measuring bending curvature. The soft sensor is thin and elastic and can track curvature changes without significantly altering the natural mechanical properties of the soft actuator. We show that the sensor can be incorporated into a closed-loop “bang-bang” controller to ensure that the actuator fully relaxes to its natural curvature before the next activation cycle. In this way, the activation frequency of the actuator can be dynamically adapted for continuous, cyclic actuation. Moreover, in the special case of slower, low power actuation, we can use the embedded curvature sensor as feedback for achieving partial actuation and limiting the amount of curvature change.

Modeling and control of a 4-ADOF upper-body exoskeleton with mechanically decoupled 3-D compliant arm-supports for improved-pHRI

Safe physical human-robotic interaction is a crucial concern for worn exoskeletons where lower weight requirement limits the number and size of actuators to be used. A novel control strategy is suggested in this paper for the low degree of freedom exoskeletons, by combining proposed mechanically decoupled passive-compliant arm-supports with active compliance, to achieve an improved and safer physical-human-robotic-interaction performance, while considering the practical limitations of low-power actuators. The approach is further improved with a novel vectoral-form of disturbance observer-based dynamic load-torque compensator, proposed to linearize and decouple the nonlinear human-machine dynamics effectively. The design of a four-degree of freedom exoskeleton test-rig that can assure the implementation of the proposed strategy is also shortly presented. It is shown through simulation and experimentation, that the use of proposed strategy results in an improved and safer physical human-robotic interaction, for the exoskeletons using limited-power actuators. It is also shown both through simulation and experimentation, that the proposed vectoral-form of disturbance based dynamic load-toque compensator, effectively outperforms the other traditional compensators in compensating the load-torques at the joints of the exoskeleton.

Effects of Nb and Mg doping on the dielectric and electromechanical properties of PbZrO[formula omitted] thin films

Antiferroelectric PbZrO3-based thin films are extensively studied for energy storage applications. Indeed, extensive work has been performed on chemical doping to increase dielectric breakdown or (antipolar to polar) AP→P phase transition field, in order to achieve higher energy storage density. However, reduction of the AP→P phase transition field is worth investigating for alternative applications, e.g., high tunability filters or low power actuators. This paper discusses the effects of Nb and Mg co-doping on the functional properties of PbZrO3 thin films (∼200 nm in thickness) processed by chemical solution deposition on platinized Si substrates. Overall, Nb and Mg co-doping stabilizes the ferroelectric phase, significantly reduces the AP→P phase transition field from 461 to 173 kV/cm and increases the low-field dielectric permittivity. At an optimal 2.5% Nb, 1.25% Mg doping concentration, the PbZrO3 films show the highest dielectric tunability of 88.8%, while maintaining a very high strain of 0.74%, and low AP→P phase transition field of 232 kV/cm.

Application of Sensor Networks for Measuring Insulin Levels

All WBANs are low-speed networks consisting of intelligent sensors and low-power actuators that can be placed on the body or implanted in humans. With the help of these networks, timely on-line data on unusual conditions of the human body can be provided, which leads to significant improvements in the quality of life. The implementation of these networks will save lives, reduce healthcare costs, and eliminate the need for costly monitoring of patients in the hospital. The paper analyzes the possibilities of the Internet of Things technology, communication standards, cloud technologies, and hardware components for developing a system for monitoring insulin levels in diabetic patients. A model and algorithm for design, construction, and management of a sensor network for monitoring insulin levels with simulation software based on the Internet of Things technology proposed. A system for monitoring insulin levels through a cloud structure has designed, which sends a message to a specialized health centre or the attending physician about the condition of diabetic patients. Simulation studies performed, and the operability of the system examined. The results give reason to believe that the considered model and the simulation project of a system for monitoring insulin levels in patients with diabetes is successful, gives realistic and reliable results for early diagnosis and prevention of various complications and can be implemented in practice.

Testing of High-Lift Common Research Model with Integrated Active Flow Control

A 10%-scale high-lift version of the Common Research Model and an active flow control (AFC) version of the model equipped with a simple-hinged flap were successfully tested. The main objective of the test was to develop an AFC system that can provide the necessary lift recovery on a simple-hinged flap high-lift system while minimizing its pneumatic power requirement. The tests were performed in the 14- by 22-Foot Subsonic Tunnel at the NASA Langley Research Center. Three types of AFC devices were examined: the double-row sweeping jets (DRSWJ), the alternating pulsed jets (APJ), and the high-efficiency low-power (HELP) actuators. The DRSWJ and the APJ actuators used two rows of unsteady jets, whereas the HELP actuators used a combination of unsteady and steady jets, to overcome strong adverse pressure gradients while minimizing the mass flow usage. Nozzle pressure ratio, mass flow consumption, and the power coefficient were used for judging the performance efficiency of the AFC devices. The current data are presented with the Transonic Wall Interference Correction System method applied. The HELP actuation concept was effective in controlling flow separation in the linear region of the curves comparing lift coefficient to mass flow rate. The HELP actuation achieved a targeted lift coefficient increment of 0.5, thus meeting the lift performance goal of the NASA Advanced Air Transport Technology project.

Self-Sensing and Control of Soft Electrothermal Actuator

Soft electrothermal actuators have been of particular interest to researchers in soft mechatronic/robotic systems due to their large deformation, lightweight, and low power actuation. Closed-loop control of soft actuators is critical for high-precision applications, due to the nonlinear relationship between actuation voltage and output bending motion. In this article, a resistive self-sensing approach was developed for the soft electrothermal actuator, which enables the closed-loop control of the actuator without external sensors. The self-sensing of the actuator's deformation is achieved by measuring the resistance change of the embedded microfilament heater of the soft electrothermal actuator. When the bimorph electrothermal actuator deflects under the temperature change, its deflection can be detected by the temperature-incurred resistance change of the embedded heater. A closed-loop controller was designed using the self-sensed deflection signal. To handle the different responses of the actuator in the heating and cooling stages, a switching proportional-integral-derivative control algorithm was designed. Specifically, two sets of control parameters were tuned and used for the heating and cooling stages, respectively. The performance of the designed control algorithm was evaluated for step response, tracking of complex wave signals, and disturbance rejection. Compared with the open-loop operation, the closed-loop controlled actuator demonstrated a much more rapid and accurate response (the rising time and settling time were reduced over 80%) and excellent tracking and disturbance rejection capabilities.

Development and Investigation of a New Rotary Valve for Power Steam Turbines

Control valves are actuating elements of a steam turbine control system; the quality of their performance directly affects the reliability of the overall steam turbine unit. Accordingly, these valves must meet very stringent requirements. Among the factors and characteristics responsible for the quality of control valves, an important place is occupied by the design simplicity, manufacturability, serviceability, ease of installation, high operating reliability, low hydraulic resistance, low dynamic loads acting on the valve stem, and moderate noise level. At the same time, it should be noted that there is quite a large fleet of old, obsolete steam turbine power units at present in Russia with valves featuring both high hydraulic resistance and poor reliability. In new, linear control valves developed in the last decade, almost all design possibilities for their improvement have been exhausted. Hence, rotary control valves may be of great interest for practice. It is this type of valve that is considered below. This information includes a description of valve design, results from the investigation of flow parameters in the valve flow path, and the flow characteristic obtained by a mathematical simulation technique. This valve meets the above-mentioned requirements to the maximum extent, is fully balanced of axial thrust, has almost zero steam leakage along the drive stem, and is operated with low-power actuators with any bores and any initial steam pressures.

Sunlight-Driven Continuous Flapping-Wing Motion.

Light-driven actuators that directly convert light into mechanical work have attracted significant attention due to their wireless advantage and ability to be easily controlled. However, a fundamental impediment to their application is that the continuous motion of light-driven flexible actuators usually requires a periodically switching light source or the coordination of other additional hardware. Here, for the first time, continuous flapping-wing motion under sunlight is realized through the utilization of a simple nanocrystalline metal polymer bilayer structure without the coordination of additional hardware. The light-driven performance can be controlled by adjusting the grain size of the upper nanocrystalline metallic layer or selecting metals with different thermodynamic parameters. The achieved highest frequency of flapping-wing motion is 4.49 Hz, which exceeds the frequency of real butterfly wings, thus informing the further development of sunlight-driven bionic flying animal robotics without external energy consumption. The flapping-wing motion has been used to realize a light-driven whirligig, a light-driven sailboat, and photoelectric energy harvesting. Furthermore, the flexible bilayer actuator features the ability to be driven by light and electricity, low-power actuation, a large deflection, fast actuation speed, long-time stability, strong design ability, and large-area facile fabrication. The bilayer film considered herein represents a simple, general, and effective strategy for preparing photoelectric-driven flexible actuators with target performances and informs the standardization and industrial application of flexible actuators in the future.

A Biomimetic Interface with High Adhesion, Tailorable Modulus for On-Skin Sensors, and Low-Power Actuators

Recently, stimuli-responsive sensors and actuators have drawn significant attention as they are promising in a wide scope of applications, including wearable devices and soft robotics. However, the...

Leaf-inspired multiresponsive MXene-based actuator for programmable smart devices.

Natural leaves, with elaborate architectures and functional components, harvest and convert solar energy into chemical fuels that can be converted into energy based on photosynthesis. The energy produced leads to work done that inspired many autonomous systems such as light-triggered motion. On the basis of this nature-inspired phenomenon, we report an unprecedented bilayer-structured actuator based on MXene (Ti3C2T x )-cellulose composites (MXCC) and polycarbonate membrane, which mimic not only the sophisticated leaf structure but also the energy-harvesting and conversion capabilities. The bilayer actuator features multiresponsiveness, low-power actuation, fast actuation speed, large-shape deformation, programmable adaptability, robust stability, and low-cost facile fabrication, which are highly desirable for modern soft actuator systems. We believe that these adaptive soft systems are attractive in a wide range of revolutionary technologies such as soft robots, smart switch, information encryption, infrared dynamic display, camouflage, and temperature regulation, as well as human-machine interface such as haptics.

Highly piezoelectric BaTiO3 nanorod bundle arrays using epitaxially grown TiO2 nanomaterials

Low-dimensional piezoelectric nanostructures such as nanoparticles, nanotubes, nanowires, nanoribbons and nanosheets have been developed for potential applications as energy harvesters, tunable sensors, functional transducers and low-power actuators. In this study, lead-free BaTiO3 nanorod bundle arrays (NBA) with highly piezoelectric properties were successfully synthesized on fluorine-doped tin oxide (FTO) substrate via a two-step process consisting of TiO2 epitaxial growth and BaTiO3 conversion. Through the TiO2 epitaxial growth on FTO substrate, (001) oriented TiO2 nanostructures formed vertically-aligned NBA with a bundle diameter of 80 nm and an aspect ratio of six. In particular, chemical etching of the TiO2 NBA was conducted to enlarge the surface area for effective Ba2+ ion diffusion during the perovskite conversion process from TiO2 to BaTiO3. The final structure of perovskite BaTiO3 NBA was found to exhibit a feasible piezoelectric response of 3.56 nm with a clear phase change of 180° from the single BaTiO3 bundle, by point piezoelectric forced microscopy (PFM) analysis. Consequently, highly piezoelectric NBA could be a promising nanostructure for various nanoscale electronic devices.

Http://ejournal.patria-artha.ac.id/index.php/patj/article/view/131

This research aims to design and implement a cheap, low power and reliable wireless sensor and actuator system which can be used in the PLC based SCADA system to overcome the limitations of wire media. The wireless sensor and actuator system can also be used as an alternative to reduce the amount of the used PLC within SCADA system. Usually, in a PLC based SCADA system, sensor and actuator are connected to PLC with wire. It has many limitations especially in terms of flexibility and resistance to interference noise, In the PLC based SCADA system with wire media also causes the number of the installed PLC will increase at each location that will be monitored or controlled. This is not efficient if the location has only a few sensors or actuators that are connected to PLC because it will have an impact on the greater costs due to expensive price of the PLC. In this research already designed a wireless sensor and actuator system based on WPAN technology (IEEE 802.15.4) is cheap, low power and reliable. The results reveal that the wireless sensor and actuator system is able to send data with good accuracy and also able to operate well when implemented to PLC based SCADA system with open loop control and closed loop control to control the water level in the tub filtration. From the results, it can be concluded that the wireless sensor and actuator system can be used in the PLC based SCADA system to overcome the limitations of wire media and can also be used as an alternative to reduce the amount of the used PLC within SCADA system.

Design of a smart bidirectional actuator for space operation

A common need for space borne instruments, satellites and planetary exploration payloads is the usage of compact, light and low power actuators. In the recent years, this need has been partially solved by the development of customized solutions with an increasing usage of smart materials. A linear bidirectional actuator based on shape memory alloy technology is presented in this work. The device has been conceived to lock the double-pendulum scanning mechanism of a miniaturized Fourier transform spectrometer for planetary observation. The mechanism class is that of pin pullers, with the pin locking the movable components of the spectrometer during launch and landing phases. The proposed mechanism, differently from available off-the-shelf devices, allows multiple actuations without the need of manual resetting. Moreover, the device requires to be powered only to change its status. An appealing feature of the adopted concept is that the actuation is intrinsically shock-less, a key requirement for deployment of devices sensitive to mechanical vibration and shocks. All these characteristics, in addition to the design flexibility of the proposed concept in terms of achievable forces and strokes, make the designed actuator promising for many different applications, from space to ground. The designed bidirectional actuator provides 0.6 mm stroke and a 50 N preload but it represents just an example of implementation for the proposed concept. Structural design of the functional elastic components and SMA alloy characterization have guided the actuator development. A mockup of the actuator has been manufactured and the predicted performances preliminary validated.

Small Size Single-axis PV Trackers: Control Strategies and System Layout for Energy Optimization

Solar tracking allows the increment of the electric production of photovoltaic modules; single-tracker systems can increase the collected solar radiation by 30% more than traditional fixed devices. Usually, mechanical movement systems are energy intensive and require periodic maintenance, with correspondent higher investment costs compared to traditional fixed plants. In this paper, particular single-tracking PV modules with reduced width and weight moved by low power actuators, are considered. Two different control strategies concerning the rotation angle of modules around a horizontal tilted axis, have been investigated. With reference to typical climatic data of south Italy, the problem of the modules self-shading has been analysed by evaluating the optimal layout of the whole system in order to optimize energy production.