Microwave power for smart material actuators

A large, ultra lightweight space structure, such as solar sails and Gossamer spacecrafts, requires a distributed power source to alleviate wire networks, unlike the localized on-board power infrastructures typically found in most small spacecrafts. The concept of microwave-driven multifunctional capability for membrane structures is envisioned as the best option to alleviate the complexity associated with hard-wired control circuitry and on-board power infrastructures. A rectenna array based on a patch configuration for high voltage output was developed to drive membrane actuators, sensors, probes, or other devices. Networked patch rectenna array receives and converts microwave power into a DC power for an array of smart actuators. To use microwave power effectively, the concept of a power allocation and distribution (PAD) circuit is adopted for networking a rectenna/actuator patch array. The use of patch rectennas adds a significant amount of rigidity to membrane flexibility and they are relatively heavy. A dipole rectenna array (DRA) appears to be ideal for thin-film membrane structures, since DRA is flexible and light. Preliminary design and fabrication of PAD circuitry that consists of a few nodal elements were made for laboratory testing. The networked actuators were tested to correlate the network coupling effect, power allocation and distribution, and response time.

The concept of microwave-driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard-wired control circuitry. Networked rectenna patch array receives and converts microwave power into a DC power for an array of smart actuators. To use microwave power effectively, the concept of a power allocation and distribution (PAD) circuit is adopted for networking a rectenna/actuator patch array. The PAD circuit is embedded into a single embodiment of rectenna and actuator array. The thin-film microcircuit embodiment of PAD circuit adds insignificant amount of rigidity to membrane flexibility. Preliminary design and fabrication of PAD circuitry that consists of a few nodal elements were made for laboratory testing. The networked actuators were tested to correlate the network coupling effect, power allocation and distribution, and response time. The features of preliminary design are 16- channel computer control of actuators by a PCI board and the compensator for a power failure or leakage of one or more rectennas.

The concept of microwave driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard wired control circuitry for applications such as membrane actuators, insect-like flying objects, or micro-aero-vehicles. Accordingly, rectenna technology was adopted to convert power from microwave to DC and run actuator devices. Previous experimental results showed that 230 VDC output was obtained from a 6 x 6 rectenna array at a far-field exposure (1.8 meters away) with an x-band input power of 20 watts. This result showed the feasibility of using microwaves to power feed and control smart actuators. We have tested a 6 x 6 JPL array patch rectenna which was designed to generate theoretical voltages up to 540 volts. The test result indicated that the performance degradation of Shottky barrier diodes on the rectenna array caused the output voltage to drop. Thus, an estimation of output voltage was made to show the performance beyond the previous measurement by extrapolating and correlating the measured data with a 200 W TWT amplifier in a reverse process. The estimated peak output voltage was 515 volts. In this experiment, due to the degradation of the rectenna performance, we had to measure the output performance based on comparison of the previous result of the rectenna output of a 20W amplifier with the output from the 200 W amplifier. For the real applications, the degradation of Schottky diodes will be a critical issue to be resolved in the fabrication process.

In order to realize a high accuracy space structure system, shape and vibration controls using smart structures are studied. Two prototypes of smart reflectors were developed and investigated. One was a long smart beam system equipped with Macro Fiber Composites (MFCs) and the other was a smart reconfigurable reflector equipped with smart actuators. The smart actuator was designed for the smart reconfigurable reflector and it consisted of a piezoelectric stack actuator and a displacement magnification mechanism. Experiments of the shape and vibration controls of the long smart beam were carried out and their performance were investigated. The performance of the smart actuator was also investigated through numerical simulations and experiments. The results are reported in this paper.

Shortage of labor and increased work of young people are causing problems in terms of care and welfare of a growing proportion of elderly people. This is a looming social problem because people of advanced ages are increasing. Necessary in the fields of care and welfare, pneumatic artificial muscles in actuators of robots are being examined. Pneumatic artificial muscles have a high output per unit of weight, and they are soft, similarly to human muscles. However, in previous research of robots using pneumatic artificial muscles, rigid sensors were often installed at joints and other locations due to the robots’ structures. Therefore, we developed a smart actuator that integrates a bending sensor that functions as a human muscle spindle; it can be externally attached to the pneumatic artificial muscle. This paper reports a smart artificial muscle actuator that can sense contraction, which can be applied to developed self-monitoring and robot posture control.

A comparative review of actuation technologies is presented. Innovative mechanisms ideas that combine high force and deflection are described. Flexible smart actuators are obtained utilizing real time adaptive biomorphic controls. Such flexible smart actuators constitute an enabling technology for a variety of biomorphic systems ranging from small, agile biomorphic explorers that emulate biological mobility to much larger humanoid or anthropomorphic system. Due to their potential ability to explore difficult, hard- to-find terrain, biomorphic explorers are promising for a variety for application in law enforcement, hazardous environment inspection, toxic waster avoidance/elimination, law enforcement, hazardous environment inspection, toxic waste avoidance/elimination, law enforcement, and search/rescue in disaster areas such as earthquake sites. The control mechanisms used for the actuators are based on biological principles. For example, a neurally inspired controller provides a mapping between the current state of the robot and a target internal configuration. Innovative fordable advanced mobility mechanisms in combination with multipod techniques inspired by peristalsis in an earthworm robot are described. Flexible actuators offer the versatility of both shape control as well as mobility attribute control.

A smart structure involves distributed actuators and sensors, and one or more microprocessors that analyze the responses from the sensors and use distributed-parameter control theory to command the actuators to apply localized strains to minimize system response. A smart structure has the capability to respond to a changing external environment (such as loads or shape change) as well as to a changing internal environment (such as damage or failure). It incorporates smart actuators that allow the alteration of system characteristics (such as stiffness or damping) as well as of system response (such as strain or shape) in a controlled manner. Many types of actuators and sensors are being considered, such as piezoelectric materials, shape memory alloys, electrostrictive materials, magnetostrictive materials, electro- rheological fluids and fiber optics. These can be integrated with main load-carrying structures by surface bonding or embedding without causing any significant changes in the mass or structural stiffness of the system. Numerous applications of smart structures technology to various physical systems are evolving to actively control vibration, noise, aeroelastic stability, damping, shape and stress distribution. Applications range from space systems, fixed-wing and rotary-wing aircraft, automotive, civil structures and machine tools. Much of the early development of smart structures methodology was driven by space applications such as vibration and shape control of large flexible space structures, but now wider applications are envisaged for aeronautical and other systems. Embedded or surface-bonded smart actuators on an airplane wing or helicopter blade will induce alteration of twist/camber of airfoil (shape change), that in turn will cause variation of lift distribution and may help to control static and dynamic aeroelastic problems. Applications of smart structures technology to aerospace and other systems are expanding rapidly. Major barriers are: actuator stroke, reliable data base of smart material characteristics, non-availability of robust distributed parameter control strategies, and non-existent mathematical modeling of smart systems. The objective of this paper is to review the state-of-the-art of smart actuators and sensors and integrated systems and point out the needs for future research.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Many rectennas have been developed over the years in order to meet power supply applications. In this paper, new broadband circular dipole rectenna arrays are investigated with the aid of an electromagnetic simulation package and measurement. The proposed device consists of circular dipole antennas and Shottky diodes as rectifying elements. The measurement of the rectenna array is shown that the design has produced the desired DC power with a reasonable efficiency. The more elements in the array, the higher output voltage although the bandwidth is not as wide as expected due to practical limitations.

This paper reports a customized silver ink and its inkjet printing process on a cellulose electroactive paper (EAPap). To synthesize a silver ink, silver nanoparticle is synthesized from silver nitrate, polyvinylpyrrolidone and ethylene glycol, followed by adding a viscosifier, hydroxyethylcellulose solution, and a surfactant, diethylene glycol. The silver ink is used in an inkjet printer (Fujifilm Dimatix DMP-2800 series) to print silver electrodes on cellulose EAPap. After printing, the electrodes are heat treated at 200oC. The sintered electrodes show that the thickness of the electrodes linearly increases as the number of printing layers increases. The electrical resistivity of the printed electrodes is 23.5 µΩ-cm. This customized ink can be used in inkjet printer to print complex electrode patterns on cellulose EAPap to fabricate flexible smart actuators, flexible electronics and sensors.

Numerous industrial applications that currently utilize expensive solenoids or slow wax motors are good candidates for smart material actuation. Many of these applications require millimeter-scale displacement and low cost; thereby, eliminating piezoelectric technologies. Fortunately, there is a subset of these applications that can tolerate the slower response of shape memory alloys. This paper details a proof-of-concept study of a novel SMA cage actuator intended for proportional braking in commercial appliances. The chosen actuator architecture consists of a SMA wire cage enclosing a return spring. To develop an understanding of the influences of key design parameters on the actuator response time and displacement amplitude, a half-factorial 2<SUP>5</SUP> Design of Experiment (DOE) study was conducted utilizing eight differently configured prototypes. The DOE results guided the selection of the design parameters for the final proof-of-concept actuator. This actuator was built and experimentally characterized for stroke, proportional control and response time.

This paper aims to present an alternative design method for remote wireless shape control of laminated composite structures using topology optimization. The photostrictive material is introduced to implement the active control of the structure by making use of its photostriction mechanism, which is actually the superposition of photovoltaic effect and converse piezoelectric effect when exposed to the illumination of near ultraviolet light. The finite element formulation including multiphysics effects of photovoltaic, pyroelectric and thermal expansion is developed to model composite structures of ferroelectric materials, based on the Mindlin plate theory of first-order shear deformation. The topology optimization method is used to seek the optimal topologies for material layouts of both the smart actuation and elastic host layers. A typical numerical example is used to demonstrate the feasibility of this method in shape control of composite structures.

Research on nano-film composite lubricated triboelectric speed sensor for bearing skidding monitoring

This paper discusses the aperture efficiency of array antennas to achieve high output DC power rectenna arrays. Generally, mutual couplings between antenna elements with narrow spacing degrade each element's gain. However, higher total output DC power is expected by increasing the number of antenna elements in the same physical area. The aperture efficiencies of 2- and 9-element array antennas are examined by simulation and experiment. It was found that the densely arranged array antenna improves the output DC power performance of the rectenna arrays.

This paper presents analytical and experimental dynamic deformation results of a flexible cantilever that is a main structural element of a space antenna. Piezoceramic actuators and piezoelectric polymer sensors are bonded on the almost whole upper and lower sides of the cantilever for shape and vibration control. The beams correct the surface error of the antenna reflector and suppress vibrations caused by disturbance. Two control systems are studied : (1) a velocity feedback control system to create damping force on the beam, and (2) a positioning control system for shape control. The calculated results, which are in good agreement with the experimental results, show that the beam changes shape as desired without transient vibrations and that these control systems are sufficiently robust against disturbance.

Smart sensors and actuators integrate more and more computing power and data storage capabilities. The use of microprocessors and microcontrollers allows not only the implementation of functions which were in the past realized using analog processing, but also the implementation of quite new ones. The paper proposes a generic architecture of smart sensors, describes their main functions, and explains how they can be applied to improve anesthesia supervision. The main interest is that, each measured value is validated according to other signal values, which allows one to distinguish equipment's dysfunction and real patient's condition variations. Some examples of validation methods are given. >