Dielectric fluids for linear switched capacitive devices

A dielectric fluid includes a first liquid having first dielectric constant and conductivity values. The dielectric fluid also includes a second liquid having second dielectric constant and conductivity values. The first dielectric constant value is greater than the second dielectric constant value and the second electrical conductivity value is less than the first electrical conductivity value. The first and second liquids form an immiscible mixture that has third dielectric constant and conductivity values between the first and second dielectric constant values and the first and second electrical conductivity values, respectively. The first liquid forms a high conductivity phase representative of the first conductivity value, and the second liquid forms a low conductivity phase representative of the second conductivity value. The low conductivity phase is continuous the high conductivity phase is a plurality of droplets non-homogeneously dispersed within, and separated by, the continuous low conductivity phase.

BACKGROUND

The field of the disclosure relates generally to actuators and motors and, more particularly, to linear switched capacitance actuators and motors.

Many known motors/actuator devices use magnetic fields as a force transfer mechanism rather than electric fields due to the higher energy densities achieved with magnetic fields using conventional materials and configurations. Such known devises are used extensively for operation of larger devices such as valves and dampers. However, they have some disadvantages for smaller applications, such as operation of robot translatables and aviation devices.

At least some other known motors and actuators use electric fields rather than magnetic fields for electro-mechanical energy transfer. A switched capacitance actuator (SCA) is an electric field-based device that demonstrates an improved energy density over earlier electric field-based devices. The electro-mechanical energy conversion is at least partially a result of the change in the device capacitance with respect to rotor translation. Such SCAs are electrostatic motors that include a translatable portion, e.g., a rotor, and a stationary portion, e.g., a stator, and operate in a manner similar to the magnetic field equivalent of the SCA, a switched reluctance motor (SRM). Both the rotor and stator include multiple electrodes that correspond to magnetic poles in a SRM. When voltage is applied to a stator capacitor electrode pair, a rotor electrode will induce relative motion in the rotor to align with the stator capacitor electrode pair. When the voltage on this stator electrode pair is removed, the appropriate next stator electrode pair that is not aligned with the rotor electrode is energized with a voltage to continue the relative motion.

However, such known SCAs do not match electromagnetic machines with respect to the motion inducing shear stress, i.e., total force or torque output per unit rotor surface area. Therefore, to attempt to achieve parity with electromagnetic devices with respect to power-to-weight ratio, at least some known SCAs compensate for the relatively lower shear stress by increasing the active area of the air gap defined by the SCA rotor and stator. According to Gauss' Law, electric field lines are not required to define closed field loops, and in contrast, magnetic field lines form closed loops that originate and terminate on the magnet. Since the electric field lines do not need to be closed, the rotor surface area may be increased by adding active layers. Another strategy to increase the power-to-weight ratio is to increase the shear stress by improving the dielectric breakdown strength within the gap of the SCA. For example this may be achieved through evacuating the SCA casing. The dielectric breakdown strength of vacuum may be much higher than that of air, which allows the strength of the electric fields in the gap to be larger. However, the evacuation configuration increases the complication of the SCA since the device needs to be securely sealed with a vacuum pump. Another example is that increased dielectric breakdown strength within the gap may be achieved by incorporating inert gases such as sulfur hexafluoride (SF6) and increasing the gas pressure to achieve the desired dielectric properties. However, these configurations also increase the complication of the SCA since sealing is again required. Such configurations are difficult to implement in robotic and aviation applications, at least partially due to size and weight constraints.

Other known SCAs have the gaps filled with a high permittivity, low-viscosity, dielectric fluid. The gap fluid is configured for high frequency wave excitation and the resultant high frequency repetition rates facilitate use of liquids with high dielectric permittivity, i.e., relatively strong dielectric constants (K), e.g., deionized water (with a K of approximately 80). In addition to deionized water, such gap fluids may include, without limitation, vegetable oil (K greater than approximately 3.0), silicone oil (K greater than approximately 2.7), fluorinated oils (K of approximately 1.9), alcohol (K greater than approximately 20) and mineral oils (K of approximately 2.0). The power density of the SCAs is significantly increased if it's electrodes are separated by a high K fluid, which significantly increases the electric force between the electrodes, yet allows for free relative motion of the electrodes. Currently, the existing high K liquids also have high electrical conductivity (S), which renders them unsuitable for SCA applications because as the S increases, electrical losses increase, and machine efficiency decreases. Moreover, if the liquid conductivity is too high, the gap will act as a continuous conductive layer between the rotor and stator, thereby significantly altering the electric field distribution desired for an SCA and, as such, reduces the force and power density. For example, liquids with high K, such as water and alcohol, typically also have a high S, i.e., approximately 5.5*102micro-siemens per meter (μS/m) and approximately 6.0 μS/m, respectively. The highly insulating liquids with a relatively low S, such as oils as described above (with an electrical conductivity of approximately 12*10−6μS/m), have a relatively low K.

If two liquids, e.g. a high K/high S fluid and a low k/low S fluid, are mixed and they are miscible, the mixture is uniform at the molecular level and a continuous conductive path across the liquid body is formed due to the universal presence of the high S fluid molecules. As a result, while the K increases moderately, the S, and the associated conduction current, increases rapidly. One effort to produce a high K/low S gap fluid includes using nanoparticle suspension instead of an all-liquid mixture. However, in general it is very difficult to achieve a high loading of nanoparticles, e.g., greater than 10 weight percent, which is needed to achieve a substantially increased dielectric constant without causing mixture stability issues and the associated high S.

BRIEF DESCRIPTION

In one aspect, a dielectric fluid is provided. The dielectric fluid includes a first liquid having a first dielectric constant value and a first electrical conductivity value. The dielectric fluid also includes a second liquid having a second dielectric constant value and a second electrical conductivity value. The first dielectric constant value is greater than the second dielectric constant value and the second electrical conductivity value is less than the first electrical conductivity value. The first liquid and the second liquid at least partially form an immiscible mixture thereof. The immiscible mixture has a third dielectric constant value with a value in between the first dielectric constant value and the second dielectric constant value. The immiscible mixture also has a third electrical conductivity value with a value in between the first electrical conductivity value and the second electrical conductivity value. The first liquid forms a high conductivity phase substantially representative of the first electrical conductivity value, and the second liquid forms a low conductivity phase substantially representative of the second electrical conductivity value. The low conductivity phase is substantially continuous within the immiscible mixture and the high conductivity phase is a plurality of droplets non-homogeneously dispersed within the immiscible mixture dispersed and separated by the substantially continuous low conductivity phase. The immiscible mixture is configured to substantially interrupt at least one continuous electrical conduction path within the immiscible mixture.

In a further aspect, a switched capacitive device is provided. The switched capacitive device includes a stationary portion including a plurality of first electrodes and a translatable portion including a plurality of second electrodes positioned in opposition to the plurality of first electrodes. The stationary portion and the translatable portion define a gap therebetween. The gap is at least partially filled with a dielectric fluid that includes a first liquid having a first dielectric constant value and a first electrical conductivity value and a second liquid having a second dielectric constant value and a second electrical conductivity value. The first dielectric constant value is greater than the second dielectric constant value and the second electrical conductivity value is less than the first electrical conductivity value. The first liquid and the second liquid at least partially form an immiscible mixture thereof. The immiscible mixture has a third dielectric constant value with a value in between the first dielectric constant value and the second dielectric constant value. The immiscible mixture also has a third electrical conductivity value with a value in between the first electrical conductivity value and the second electrical conductivity value. The first liquid forms a high conductivity phase substantially representative of the first electrical conductivity value, and the second liquid forms a low conductivity phase substantially representative of the second electrical conductivity value. The low conductivity phase is substantially continuous within the immiscible mixture and the high conductivity phase is a plurality of droplets non-homogeneously dispersed within the immiscible mixture dispersed and separated by the substantially continuous low conductivity phase. The immiscible mixture is configured to substantially interrupt at least one continuous electrical conduction path within the immiscible mixture.

In another aspect, a machine is provided. The machine includes a body, at least one electric power source coupled to the body, and at least one mechanism translatably coupled to the body. The at least one mechanism includes at least one switched capacitive device configured to induce movement of the at least one translatable mechanism. The at least one switched capacitive device includes a stationary portion including a plurality of first electrodes and a translatable portion including a plurality of second electrodes positioned in opposition to the plurality of first electrodes. The stationary portion and said translatable portion define a gap therebetween. The gap is at least partially filled with a dielectric fluid that includes a first liquid having a first dielectric constant value and a first electrical conductivity value and a second liquid having a second dielectric constant value and a second electrical conductivity value. The first dielectric constant value is greater than the second dielectric constant value and the second electrical conductivity value is less than the first electrical conductivity value. The first liquid and the second liquid at least partially form an immiscible mixture thereof. The immiscible mixture has a third dielectric constant value with a value in between the first dielectric constant value and the second dielectric constant value. The immiscible mixture also has a third electrical conductivity value with a value in between the first electrical conductivity value and the second electrical conductivity value. The first liquid forms a high conductivity phase substantially representative of the first electrical conductivity value, and the second liquid forms a low conductivity phase substantially representative of the second electrical conductivity value. The low conductivity phase is substantially continuous within the immiscible mixture and the high conductivity phase is a plurality of droplets non-homogeneously dispersed within the immiscible mixture dispersed and separated by the substantially continuous low conductivity phase. The immiscible mixture is configured to substantially interrupt at least one continuous electrical conduction path within the immiscible mixture.

DETAILED DESCRIPTION

The switched capacitive devices described herein provide a cost-effective method for increasing the energy efficiency of the associated devices and systems. Specifically, in order to achieve higher total energy efficiency for the actuation systems embedded within those systems, a high power switched capacitance actuator (SCA) is used. More specifically, operation of the disclosed SCAs is based on a spatial change of electric fields rather than based on magnetic fields which are used in some conventional EMAs. To increase the effectiveness of force generation through the electric fields, an immiscible mixture of a first liquid having a first dielectric constant value and a first electrical conductivity value and a second liquid having a second dielectric constant value and a second electrical conductivity value is formed. The first dielectric constant value is greater than the second dielectric constant value and the second electrical conductivity value is less than the first electrical conductivity value. Therefore, the immiscible mixture has a third dielectric constant value with a value in between the first and second dielectric constant values and a third electrical conductivity value in between the first and second electrical conductivity values. Also, specifically, the immiscible mixture is at least partially formed with the first liquid non-homogeneously dispersed within the mixture as a plurality of droplets within a predetermined size range through the use of a surfactant mixed therein. Further, specifically, the first liquid forms a high conductivity phase and the second liquid forms a low conductivity phase. The low conductivity phase is substantially continuous within the immiscible mixture and the droplets of the high conductivity phase are dispersed and separated from each other by the substantially continuous low conductivity phase. As such, the potential for forming continuous electrical conduction path within the immiscible mixture is substantially decreased.

The SCAs described herein offer advantages over electromagnetic machines that include, without limitation, sufficient torque generation without using continuous current, removing the requirement of using an iron core as a magnetic conductor, eliminating the need for a yoke, and significantly decreasing the amount of copper in the actuators, thereby decreasing the size, weight, and costs of the actuators. Also, specifically, the SCAs described herein are linear, direct drive SCAs without a transmission gear. Therefore, the embodiments described herein further facilitate decreasing the weight of actuation systems used in mobile and/or translatable machines.

In addition, the SCAs described herein provide for an improved efficiency over that of electromagnetic machines because the losses of the system which include electrical, mechanical, and electromagnetic losses are lower. Specifically, the copper losses in the SCA are smaller than in conventional machines and the dielectric losses can be held small compared to iron losses. Due to the lighter weight and decreased losses, the SCAs described herein demonstrate a high gravimetric power density, i.e., a high power-to-weight ratio. As such, the SCAs described herein provide a light weight, high efficiency linear actuator for applications where the gravimetric power density of the actuator is critical, for example, and without limitation, robotics, aviation, automotive, and wind power applications.

FIG. 1is a schematic view of an exemplary machine, and more specifically, a robotic device, i.e., a legged robot100that includes exemplary translatable mechanisms, i.e., robotic translatables110in the form of translatable legs coupled to a robot body115. In the exemplary embodiment, four translatables110are shown. Alternatively, robotic device100includes any number of translatables110that enables operation of robotic device100as described herein. Each of robotic translatables110includes at least one switched capacitive device, i.e., at least one switched capacitance actuator (SCA)120. Legged robot100also includes an independent electric power supply system130coupled to robot body115. In the exemplary embodiment, system130is a plurality of direct current (DC) batteries132. Batteries132are coupled to SCA120through a converter (not shown) that includes, e.g., and without limitation, a direct current-to-alternating current (DC/AC) inverter coupled to a high frequency DC/DC step up converter through a high voltage DC link. Such converters have ratings that include, without limitation, a range of power outputs between 0.1 kilowatt (kW) and 100.0 kW, a range of voltage outputs between 500 volts (rms) and 3000 volts (rms), a range of DC link voltages between 0.8 kilovolts (kV) and 5.0 kV, and an output frequency in a range between 0 Hertz (Hz) and 1000 Hz.

Alternative embodiments of robotic devices include, without limitation, assembly line robots. Such assembly line robots typically include a single robotic arm that includes a device, such as SCA120receiving AC power from an alternating current (AC) source through a power converter system that includes an AC/DC boost rectifier coupled to the AC power source, a DC/AC inverter coupled to SCA120, and a high voltage DC link coupled to the rectifier and the inverter. Such converters have ratings that include, without limitation, a range of power outputs between 0.1 kW and 100.0 kW, a range of voltage outputs between 500 volts (rms) and 3000 volts (rms), a range of DC link voltages between 0.8 kV and 5.0 kV, and an output frequency in a range between 0 Hz and 1000 Hz.

FIG. 2is a schematic perspective view of an exemplary linear SCA200that may be used with robotic device100as an exemplary embodiment of SCA120(both shown inFIG. 1). A coordinate system201includes an x-axis (height direction), a y-axis (longitudinal dimension), and a z-axis (width, or transverse direction) for reference. In the exemplary embodiment, linear SCA200includes a translatable assembly206that includes a translatable center piece208and twenty (20) translatable circuit boards202. Translatable center piece208includes four shafts210(only three shown). Translatable circuit boards202are manufactured with a precise predetermined thickness and dovetailed into center piece208with precise slots (not shown) defined therein. Linear SCA200also includes a stationary assembly212that includes two side plates214, twenty-two (22) stator circuit boards204, and four bearings216(only three shown). Stationary circuit boards204are manufactured with a precise predetermined thickness and dovetailed into side plates214with precise slots (not shown) defined therein. Stationary circuit boards204and translatable circuit boards202are substantially parallel to each other. Translatable assembly206is linearly translatable with respect to stationary assembly212with movement of translatable assembly206induced in opposing directions parallel to the longitudinal y-axis as indicated by direction of translation arrow218.

Translatable center piece208and side plates214are fabricated from electrically insulated structural materials to hold circuit boards204and202, respectively, such that a gap (not shown inFIG. 2) of predetermined dimensions is defined. Such electrically insulated structural materials include any combination of, without limitation, thermosets and thermoplastics. Thermosets include epoxies either unfilled or filled with fillers and fiberglass to improve mechanical and electrical properties. Thermoplastics include selections from a plurality of engineering plastics, e.g., without limitation, polypropylene, polyetherimide, and polycarbonates that may be either filled or unfilled with fillers and fiberglass to improve mechanical and electrical properties.

Linear SCA200is configured to induce a shear force in the longitudinal direction in a range between approximately 260 Newtons (N) and approximately 1200 N with a continuous power draw at a translation rate of translatable assembly206of approximately 1.25 meters per second (m/s) in a range between approximately 375 Watts (W) and approximately 2500 W. The weight of linear SCA200is in a range between approximately 800 grams (g) and approximately 1220 g to provide a gravimetric power density in a range between approximately 375 Watts per kilogram (W/kg) and approximately 2500 W/kg and a gravimetric force density in a range between approximately 300 Newtons per kilogram (N/kg) and approximately 2000 N/kg.

FIG. 3is a schematic view of a portion of SCA200between a translatable circuit board202and a stationary circuit board204. Coordinate system201, including the x-axis (height direction), the y-axis (longitudinal dimension), and the z-axis (transverse direction), is provided for reference. In the exemplary embodiment, stationary circuit board204includes a stationary substrate220having a stationary substrate surface222and a plurality of stationary electrodes224positioned thereon. Similarly, translatable circuit board202includes a translatable substrate226having a translatable substrate surface228and a plurality of translatable electrodes230positioned thereon.

Stationary electrodes224and translatable electrodes230are coupled to stationary substrate surface222and translatable substrate surface228, respectively, through any method that enables operation of linear SCA200as described herein, including, without limitation, adhesives, soldering, and brazing, where the adhesive, soldering, and brazing materials (not shown) are structurally, chemically, and electrically compatible with stationary electrodes224and stationary substrate220and translatable electrodes230and translatable substrate226, respectively. In the exemplary embodiment, stationary substrate220and translatable substrate226are manufactured from any material that enables operation of linear SCA200as described herein, including, without limitation, an epoxy composite with a predetermined permittivity, such as, without limitation, FR-4 and alumina ceramics to facilitate structural support of stationary electrodes224and translatable electrodes230. Further, stationary electrodes224and translatable electrodes230are formed from any materials that enable operation of linear SCA200as described herein.

Also, in the exemplary embodiment, at least one layer of dielectric coatings232is formed on each of stationary substrate surface222and translatable substrate surface228. Alternatively, in some embodiments, SCA200includes at least one layer of dielectric coatings232on only one of stationary substrate surface222and translatable substrate surface228. Dielectric coatings232are formed from high permittivity materials, including, without limitation, semicrystalline terpolymer P(VDF-TrFE-CFE), where VDF is vinylidene fluoride, TrFe is trifluoroethylene, and CFE is 1,1-chlorofluoroethylene, and barium titanate (BaTiO3) doped polymers. Dielectric coating232formed on stationary substrate surface222, in some embodiments, is a different material from coating232formed on translatable substrate surface228. Moreover, in some embodiments, dielectric coatings232are formed from a plurality of layers, where one or more layers are the same material or one of more layers are a different material. Further, stationary electrodes224and translatable electrodes230are fully embedded within dielectric coatings318. Alternatively, stationary electrodes224and translatable electrodes230are partially embedded within dielectric coatings232such that a portion of stationary electrodes224and translatable electrodes230are exposed. Dielectric coatings232facilitate improving performance of SCA200by increasing corona and surface flashover voltage, increasing the electrical polarization and hence the power density, and reducing a potential for any ferroelectric hysteresis loss through the proper choice of dielectric material.

Moreover, in the exemplary embodiment, a stationary dielectric coating surface234and a translatable dielectric coating surface236define a gap238filled with a dielectric fluid240(discussed further below).

In operation, stationary electrodes224and translatable electrodes230correspond to the magnetic poles of an SRM. When an adjacent pair of stationary electrodes224is energized with a voltage, an electric field (not shown) is induced within gap238. The electric field includes a plurality of low density distribution regions (not shown) proximate those regions in gap238between adjacent stationary electrodes224and adjacent translatable electrodes230substantially parallel to direction of translation218. The electric field also includes a plurality of intermediate density distribution regions (not shown) proximate those regions in gap238having nonaligned stationary electrodes224and translatable electrodes230. The electric field further includes a plurality of high density distribution regions (not shown) proximate those regions in gap238having aligned stationary electrodes224and translatable electrodes230. The strength of the electrical coupling, i.e., the density of the field distribution is proportional to the distance between stationary electrodes224and translatable electrodes230. Therefore, the high density distribution regions and intermediate density distribution regions are proportional to distance D1and distance D2, respectively. The high density distribution regions induce electric field distribution values within a range between approximately 10 kilovolts (kV) per millimeter (mm) and approximately 30 kV/mm.

Moreover, when an adjacent pair of stationary electrodes224is energized with a voltage, a proximate translatable electrode230linearly translates to align with stationary electrodes224. Once the adjacent pair of stationary electrodes224and proximate translatable electrodes230are aligned, the voltage on this pair of stationary electrodes224is removed and the appropriate next pair of stationary electrodes224that is not aligned with proximate translatable electrodes230is energized with the DC voltage to continue the linear motion as shown by arrow218. In the exemplary embodiment, stationary electrodes224are energized to a value of approximately +3000 volts and translatable electrodes230, which are grounded, have a voltage of approximately zero volts. Alternatively, any voltages are used that enable operation of SCA200as described herein.

To increase and more evenly distribute the force exerted on translatable circuit board202, multiple stationary electrodes224may be energized substantially simultaneously, e.g., without limitation, every other stationary electrode224. To facilitate such simultaneous energization, an external switching circuit (not shown) may be used to switch the excitation of stationary electrodes224. Also, SCA200may also be energized through a synchronous three-phase power alternating current (AC) system.

FIG. 4is a schematic view of an exemplary immiscible mixture300that may be used with SCA200(shown inFIG. 2). In the exemplary embodiment, immiscible mixture300is a dielectric fluid that includes a first liquid302, mixed with a second liquid304. Also, immiscible mixture300includes a surfactant306.

First liquid302has a first dielectric constant (K) value and a first electrical conductivity (S) value. In the exemplary embodiment, first liquid302is deionized water with a first K value, at an approximately 1000 Hz excitation frequency of SCA200, within a range between approximately 80 and approximately 5000. Such range is relatively broad due to the dielectric constant and conductivity may vary with the remnant ion density in the water, the temperature, which electrode is used, and the thickness of the water layer. Also, at the excitation frequency of approximately 1000 Hz, deionized water as first liquid302has a first S value within a range between approximately 5*10−6siemens per meter (S/m) and approximately 1*10−3S/m. Such range is relatively broad due to the dielectric constant and conductivity may vary with the remnant ion density in the water, the temperature, which electrode is used, and the thickness of the water layer. Alternatively, first liquid302is any liquid with a relatively large K value and a relatively high S value that enables operation of immiscible mixture300and SCA200as described herein, including, without limitation, alcohol with a nominal K value above 20 and a nominal S value of approximately 6*10−4S/m. First liquid302is a dispersed medium in the form of water droplets with equivalent diameters within a range between approximately 0.1 micrometers (μm) and approximately 0.2 μm. Alternatively, the water droplets of first liquid302have any size range that enables operation of immiscible mixture300and SCA200as described herein, including, without limitation, equivalent diameters within a range between approximately 0.05 μm and approximately 1 μm, and within a range between approximately 0.005 μm and approximately 20 μm.

Second liquid304has a second K value and a second (S) value. In the exemplary embodiment, second liquid304is an electrically insulating hydrocarbon oil, including, without limitation, mineral oil with a second K value, at the approximately 1000 Hz excitation frequency of SCA200, within a range between approximately 1 and approximately 5. Also, at the excitation frequency of approximately 1000 Hz, mineral oil as second liquid304has a first S value within a range between approximately 1*10−13S/m and approximately 1*10−8S/m. Such range is relatively broad due to conductivity may vary with the remnant ion density in the water, the temperature, which electrode is used, and the thickness of the water layer. Alternatively, second liquid304is any liquid with a relatively low S that enables operation of immiscible mixture300and SCA200as described herein, including, without limitation, fluorinated oils. Second liquid304is a dispersion medium in which first liquid302is dispersed as described above.

In the exemplary embedment, first liquid302has a first K value within a range between approximately 80 and approximately 5000 and second liquid304has a second K value within a range between approximately 1 and approximately 5. As such, the first K value is approximately two to three orders of magnitude greater than the second K value. Also, first liquid302has a first S value within a range between approximately 5*10−6S/m and approximately 1*10−3S/m and second liquid304has a second S value within a range between approximately 1*10−13S/m and approximately 1*10−8S/m. Therefore, the second S value is approximately three to ten orders of magnitude less than the first S value. As described further below, immiscible mixture300has a third K value with a value in between the first K value and the second K value, and a third S value between the first S value and the second S value.

First liquid302and second liquid304form immiscible mixture300that includes two phases. First liquid302forms the first phase that is a high dielectric constant/high conductivity phase (hereon referred to as the high conductivity phase) and second liquid304forms the second phase that is a low dielectric constant/low conductivity phase (hereon referred to as the low conductivity phase). The high conductivity phases defined by the isolated water droplets of first liquid302are effectively separated by the continuous low conductivity phase defined by the continuous mineral oil of second liquid304to facilitate interrupting otherwise continuous conduction paths308. If these two liquids302and304form a miscible mixture rather than immiscible mixture300, the miscible mixture appears as uniform at the molecular level, where the high conductivity phase easily forms a continuous conductive path (not shown) across the miscible mixture. As a result, as the concentration of the high conductivity phase increases, and while the dielectric constant increases moderately, the conduction current increases rapidly. As such, a miscible mixture provides for a relatively high dielectric strength constant, however, it also provides for a relatively high electrical conductivity. Therefore, while the two phases still contribute to a sufficiently high dielectric constant of immiscible mixture300in a similar manner as for a miscible mixture, the conductivity of immiscible mixture300is much lower than the miscible mixture because the high conductivity phases of droplets302are effectively separated by the continuous low-conductivity phase of oil304, and hence continuous conduction paths308are interrupted.

In order to achieve a stable emulsion of immiscible mixture300rather than a miscible mixture with macroscopic separation, a proper surfactant306is used to significantly reduce the surface energy for the interface between the oil/low conductivity and water/high conductivity phases, and hence promote the formation of small and stable droplets302. The selection of surfactants at least partially depends on the materials of SCA200. As such, surfactant306facilitates forming first liquid302into droplets that are non-homogeneously dispersed within immiscible mixture300. In the exemplary embodiment, surfactant306is a nonionic polyethylene glycol oleyl ether with chemical formula C18H35(OCH2CH2)nOH, where n=2. Alternatively, surfactant306is any surfactant that enables operation of immiscible mixture300and SCA200as described herein, including, without limitation, for hydrocarbon oils, CxH2x+1(OCH2CH2)nOH, CxH2x−1(OCH2CH2)nOH, and H(CH2CH2)m(OCH2CH2)nOH, where x varies from 1 to 20, n varies from 1 to 100, and m varies from 1 to 100. Also, alternatively, for fluorinated oils, fluorosurfactant including, without limitation, RfCH2CH2O(CH2CH2O)xH, where the group Rf is F(CF2CF2)yand x varies from 1 through 20 and y varies from 3 through 8. Further, alternatively, for fluorinated oils, surfactants F—(CF2CF2)x—CH2CH2O—(CH2CH2O)y—H, and H—(CF2CF2)x—CH2-OH, where x varies from 1 to 10 and y varies from 0 to 25, are used. Moreover, in the exemplary embodiment, surfactant306is approximately 2.0 weight percent of immiscible mixture300. Alternatively, surfactant306is added to any weight percent value that enables operation of immiscible mixture300and SCA200as described herein, including, without limitation, within a range between approximately 0.5 weight percent to approximately 5.0 weight percent.

The moderately strong dielectric strength constant values of immiscible mixture300between the K values of first liquid302and second liquid304with the much lower electrical conductivity values then the high conductivity values of first liquid302facilitates increasing the voltage applied to stationary electrodes224(shown inFIG. 3), thereby increasing the electrostatic force between stationary electrodes224and translatable electrodes230across gap238and dielectric fluid240(all shown inFIG. 3), i.e., immiscible moisture300, generates increased force and motion output for SCA200, thereby improving the associated gravimetric power density values. This is due to the force and power density of SCA200are at least partially related to the electrical polarization in dielectric medium240surrounding electrodes224and230, which in turn is proportional to the dielectric constant of the filling materials, i.e., immiscible mixture300. In addition, the relatively low conductivity values of dielectric medium240surrounding electrodes224and230facilitates reducing electrical losses in dielectric medium240, and hence facilitating higher efficiencies and lower heat generation in SCA200. Furthermore, immiscible mixture300includes sufficient density and lubricating properties to facilitate free movement of translatable electrodes230.

FIG. 5is a graphical view of the dielectric constants and equivalent electrical conductivities of a plurality of exemplary constituent liquids as a function of operating frequency of SCA200(shown inFIG. 2).FIG. 5includes a dielectric constant graph400that includes a y-axis402defining a logarithmic representation of dielectric constant (K) from 1 (100) through 100,000 (105), where the K values are unitless. Graph400also includes an x-axis404defining a logarithmic representation of excitation frequency of stationary circuit cards204(shown inFIGS. 2 and 3) from 100 through 10,000,000 (107) in units of Hertz (Hz).

Also, graph400includes a plurality of dielectric constant versus frequency curves for a plurality of fluids. The uppermost curve is a substantially 100% deionized (DI) water curve406and the lowermost curve is a substantially 100% mineral oil curve408. The graphs between 100% DI water curve406and 100% mineral oil curve408represent varying weight percents (%) of mineral oil and DI water. Specifically, curve410represents a 10% water-in-oil mixture, curve412represents a 15% water-in-oil mixture, curve414represents a 20% water-in-oil mixture, curve416represents a 30% water-in-oil mixture, and curve418represents a 40% water-in-oil mixture. A desired direction arrow indicates that higher dielectric constants are preferred over lower dielectric constants.

FIG. 5also includes a conductivity graph420that includes a y-axis422defining a logarithmic representation of equivalent electrical conductivity (S) from 1*10−11through 1*10−2, where the S values are in siemens per meter (S/m). Graph420also includes an x-axis424defining a logarithmic representation of excitation frequency of stationary circuit cards204from 100 through 10,000,000 (107) in units of Hz.

Also, graph420includes a plurality of equivalent electrical conductivity versus frequency curves for a plurality of fluids. The uppermost curve is a substantially 100% deionized (DI) water curve426and the lowermost curve is a substantially 100% mineral oil curve428. The graphs between 100% DI water curve426and 100% mineral oil curve428represent varying weight percents (%) of mineral oil and DI water. Specifically, curve430represents a 10% water-in-oil mixture, curve432represents a 15% water-in-oil mixture, curve434represents a 20% water-in-oil mixture, curve436represents a 30% water-in-oil mixture, and curve438represents a 40% water-in-oil mixture. A desired direction arrow indicates that lower equivalent electrical conductivities are preferred over higher equivalent electrical conductivities.

In the exemplary embodiment, dielectric fluid240(shown inFIGS. 3 and 4) is formed through mixing a first liquid, i.e., DI water having a first, i.e. DI water dielectric constant value and a first, i.e., DI water electrical conductivity value with a second liquid, i.e., mineral oil, having a second, i.e., mineral oil dielectric constant value and a second, i.e., mineral oil electrical conductivity value. The DI water dielectric constant value is greater than the mineral oil dielectric constant value and the mineral oil electrical conductivity value is less than the DI water electrical conductivity value. The DI water and the mineral oil at least partially form immiscible mixture300(shown inFIG. 4), i.e., dielectric fluid240(shown inFIG. 3) having a third dielectric constant value with a value in between the DI water dielectric constant value and the mineral oil dielectric constant value. In addition, immiscible mixture300has a third electrical conductivity value with a value in between the DI water electrical conductivity value and the mineral oil electrical conductivity value.

Also, in the exemplary embodiment, at approximately 1000 Hz excitation frequency, substantially 100% DI water curve406identifies a range of DI water dielectric constant values between approximately 80 and approximately 5000 and 100% DI water curve426identifies a range of equivalent electrical conductivity values between approximately 5*10−6siemens per meter (S/m) and approximately 1*10−3S/m. Similarly, at approximately 100,000 Hz, substantially 100% DI water curve406identifies a range of DI water dielectric constant between approximately 80 and approximately 100 and 100% DI water curve426identifies a range of DI water electrical conductivity values between approximately 5*10−6S/m and approximately 1*10−3S/m. Such ranges are relatively broad due to the dielectric constants and conductivities may vary with the remnant ion density in the water, the temperature, which electrode is used, and the thickness of the water layer.

Further, in the exemplary embodiment, at approximately 1000 Hz excitation frequency, substantially 100% mineral oil curve408identifies a range of dielectric constant values between approximately 1 and approximately 5 and 100% mineral oil curve428identifies a range of equivalent electrical conductivity values between approximately 1*10−13S/m and approximately 1*10−8S/m. Similarly, at approximately 100,000 Hz, substantially 100% mineral oil curve408identifies a range of mineral oil dielectric constant values between approximately 1 and approximately 5 and 100% mineral oil curve428identifies a range of mineral oil electrical conductivity values between approximately 1*10−13S/m and approximately 1*10−8S/m. 100% mineral oil curve428varies greatly with peaks and valleys in the frequency spectrum under consideration due to the electrical conductivity values being so low, and, as such, curve428includes a great amount of noise. Such ranges are relatively broad due to the dielectric constants and conductivities may vary with the remnant ion density in the water, the temperature, which electrode is used, and the thickness of the water layer. Also, conductivity values less than 1*10−11are not shown due to the range of y-axis422.

Further, in the exemplary embodiment, at approximately 1000 Hz, dielectric fluid240is represented by 15% water-in-oil mixture curve412and 15% water-in-oil mixture curve432, i.e., the exemplary immiscible mixture is a 15% water-in-oil mixture, Alternatively, any mixture of DI water and mineral oil that enables operation of SCA200as described herein is used, including, without limitation, within a range between approximately 10% water-in-oil mixture and approximately 20% water-in-oil mixture. Further, alternatively, the relative mixture of DI water and mineral oil is within a range between approximately 5% water-in-oil mixture and 40% water-in-oil mixture.

At approximately 1000 Hz, 15% water-in-oil mixture curve412identifies a range of dielectric constant values for dielectric fluid240(immiscible mixture300) between approximately 150 and approximately 300. Also, 15% water-in-oil mixture curve432identifies a range of electrical conductivity values for dielectric fluid240between approximately 2*10−5S/m and approximately 3*10−5S/m. Similarly, at approximately 100,000 Hz, 15% water-in-oil mixture curve412identifies a range of dielectric constant values for dielectric fluid240between approximately 11 and approximately 20. Further, 15% water-in-oil mixture curve432identifies a range of electrical conductivity values for dielectric fluid240between approximately 3*10−5S/m and approximately 1*10−4S/m.

Therefore, in the exemplary embodiment, for 1000 Hz, the dielectric constant value of immiscible mixture300(dielectric fluid240) is between approximately 150 and approximately 300. Also, the dielectric constant value of 100% mineral oil is between approximately 1 and approximately 5. Therefore, there is a difference of approximately two to three orders of magnitude due to the dielectric constant value of deionized water in the range between approximately 80 and approximately 5000. The electrical conductivity for immiscible mixture300is between approximately 2*10−5S/m and approximately 3*10−5S/m. Also, the electrical conductivity for 100% DI water is between approximately 5*10−6S/m and approximately 1*10−3S/m. Therefore, there is a difference of approximately one to two orders of magnitude due to the extremely low conductivity values of the 100% mineral oil.

Similarly, in the exemplary embodiment, for 100,000 Hz, the dielectric constant value of immiscible mixture300(dielectric fluid240) is between approximately 11 and approximately 20. Also, the dielectric constant value of 100% mineral oil is between approximately 1 and approximately 5. Therefore, there is a difference of approximately one to three orders of magnitude due to the dielectric constant value of deionized water in the range between approximately 80 and approximately 5000. The electrical conductivity for immiscible mixture300is between approximately 3*10-5 S/m and approximately 1*10−4S/m. Further, the electrical conductivity for 100% DI water is between approximately 5*10−6S/m and approximately 1*10−3S/m. Therefore, there is a difference of approximately one order of magnitude due to the extremely low conductivity values of the 100% mineral oil.

FIG. 6is a schematic view of an exemplary miscible mixture500that shows macroscopic separation of the constituent liquids, i.e., water302and oil304, due to lack of proper surfactant.FIG. 7is a schematic view of immiscible mixture300that may be used with SCA200(shown inFIG. 2). Immiscible mixture300includes a properly chosen surfactant. The uniform white color indicates that the two liquids are immiscible at the microscopic level because, otherwise, immiscible mixture300would appear transparent. Also, immiscible mixture300is uniform on a macroscopic level as indicated by the consistently opaque color.

The use of immiscible liquid mixture300in emulsion has three major technical advantages. Firstly, the two phases in the mixture have very similar specific gravities, and hence the precipitation due to gravity is significantly reduced, which promotes the stability of the emulsion. Secondly, the use of an all-liquid system makes it easier to re-disperse the mixture even if phase segregation is caused under certain conditions, which is different from the case of nanoparticle-liquid suspension, where the nanoparticles may precipitate and form a coating on exposed surfaces. Thirdly, the emulsion contains two phases that are separated on the microscopic scale, yet uniform on a macroscopic scale, and hence conduction can be blocked without causing issues due to phase separation on a macroscopic scale.

FIG. 8is a schematic view of another exemplary machine, and more specifically, an aircraft component, i.e., aircraft wing600that may use SCA200. Aircraft wing600includes an airfoil portion602and a flap portion604hingedly coupled to airfoil portion602through SCA200. SCA200is energized as described above to hingedly position flap portion604through liner translation of SCA200.

The above-described switched capacitive devices provide a cost-effective method for increasing the energy efficiency of the associated devices and systems. Specifically, in order to achieve higher total energy efficiency for the actuation systems embedded within those systems, a high power switched capacitance actuator (SCA) is used. More specifically, operation of the disclosed SCAs is based on a spatial change of electric fields rather than based on conventional magnetic fields. The SCAs described herein offer advantages over electromagnetic machines that include, without limitation, sufficient torque generation without using continuous current, removing the requirement of using an iron core as a magnetic conductor, eliminating the need for a yoke, and significantly decreasing the amount of copper in the actuators, thereby decreasing the size, weight, and costs of the actuators. Also, specifically, the SCAs described herein are linear, direct drive SCAs without a transmission gear. Therefore, the embodiments described herein further facilitate decreasing the weight of actuation systems used in mobile and/or translatable machines.

In addition, the SCAs described herein provide for an improved efficiency over that of electromagnetic machines because the losses of the system which include electrical, mechanical, and electromagnetic losses are lower. Specifically, the copper losses in the SCA are smaller than in conventional machines and the dielectric losses can be held small compared to iron losses. Due to the lighter weight and decreased losses, the SCAs described herein demonstrate a high gravimetric power density, i.e., a high power-to-weight ratio. As such, the SCAs described herein provide a light weight, high efficiency linear actuator for applications where the gravimetric power density of the actuator is critical, for example, and without limitation, robotics, aviation, automotive, and wind power applications.

An exemplary technical effect of the methods, systems, and apparatus described herein includes at least one of: (a) increasing the energy efficiency of switched capacitance actuators (SCAs); (b) increasing the energy efficiency of systems through high power SCAs; (c) replacing conventional magnetic field-based actuator devices with SCAs based on a spatial change of electric fields; (d) decreasing the weight of the SCAs by eliminating iron cores as magnetic conductors, yokes, and transmission gearing, and significantly decreasing the amount of copper in the SCAs; and (e) increasing the force strength of the SCAs by filing a gap between a stationary circuit board and a translatable circuit board with an immiscible mixture having a relatively high dielectric constant and a relatively low electrical conductivity, thereby facilitating use of stronger electric fields to generate greater motive forces while reducing the potential for excessive electrical arcing within the SCAs.

Exemplary embodiments of switched capacitive devices are described above in detail. The high power SCAs, and methods of operating such systems and devices are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the methods may also be used in combination with other systems requiring highly efficient movement of translatable devices, and are not limited to practice with only the systems and methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other machinery applications that are currently configured to receive and accept SCAs, e.g., and without limitation, translatable robotic systems in automated assembly facilities.