MXPA97000415A - Linear motion actuator in miniat - Google Patents

Abstract

The present invention relates to a linear actuator, comprising: first and second wafer elements having primary and second wafer surfaces in slidable, abutting engagement, an electrically insulating thin film layer of natural oxide formed on one of said surfaces of first and second wafer between said first and second wafer surfaces and said first and second wafer elements, said insulating layer being between 50 Angstroms and 2 um in thickness; means for selectively electrostatically holding said first wafer surface relative to said wafer; said second wafer surface, and inertial generating means, operatively coupled to said second wafer element, for moving said second wafer element relative to said first wafer element;

Description

MINIATURE LINEAR MOTION ACTUATOR Field of the Invention This invention relates generally to an improved miniature linear scaling actuator. More particularly, the present invention defines a miniaturizable linear motor using an expandable member attached to a fixed member; the expandable member moving relative to the fixed member. Background v Compendium of the Invention Medical applications often use surgical instruments that must be adjusted in the hand of a physician. When operating, the instrument must have constant movement and little reaction of recule. A linear actuator does not produce rotary torsion when starting, and a very small device that provides substantial force to lock into multiple attitudes and positions and that allows precise control would be well received in the matter. A specific type of linear actuator uses the shape change of piezoelectric materials that occurs when voltage is applied therethrough to generate linear motion. A "double grip" type actuator operates by holding a first end of the piezoelectric material, expanding the overall length of the material, holding the other end of the piezoelectric material, and releasing the first end of the material, and then reducing the "" size of the piezoelectric material. Piezoelectric material. Each repetition of the process described above causes a cycle of movement. The piezoelectric linear actuator Inchworms (brand adopted by its manufacturer), manufactured by Burleigh Corp. of Fishers, New York, United States, is an example of a double-grip actuator. The Inchworms device includes three piezoelectric elements, two of which mechanically and orthogonally hold an arrow extending axially through the motor. However, even the smallest of these devices is too large in diameter (around 0.5 in) for many applications in micro-devices. A different linear actuator, which uses a single type of grip mode, is disclosed by Judy, Polla and Robbins in "A Linear Piezoelectric Stepper Motor with Sub-Micrometer Step Size and Centimeter Travel Range", IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 37, No. 5, September 1990 ("Judy et al."). The piezoelectric element described in this antecedent measures 25.4 x 12.7 x 1.6 mm, while the overall size of the scaler is greater than 150 x 60 x 100 mm. The principle of operation of the device is based on the expansion and contraction of a piezoelectric element mounted on a sliding structure. The design of Judy and collaborators was relatively large, difficult to assemble, and varied greatly in performance characteristics, depending on their physical orientation - the direction in which they were held.The Judy et al. Device used components made of ceramic, metal and non-conductive piezoelectric insulators in general terms, which made it difficult to reduce the overall size of the device Bronze sliding electrodes electrostatically clamped in a Teflon insulating layer between the plates The Teflon had a thickness of about 63.5 μm. Judy's system operated by holding the piezoelectric element during its expansion, so that it could not move relative to the base and thus push the load forward.While the contraction, the gripping force was removed, so that the piezoelectric element moved in relation to the base Two types of double grip linear motors they are disclosed in U.S. Patent No. 4,736,131 to Fujimoto and U.S. Patent No. 4,709,183 to Lang. In the '131 patent, two piezoelectric elements are fastened in side walls perpendicular to the axis of movement through movement amplifying levers. The '183 patent is also based on the piezoelectric material to achieve mechanical grip of the side wall to implement a linear double-grip movement. The lateral wall grip requires a high degree of precision in manufacturing (orthogonal machining) and cost. Linear motors based on vibratory phenomena employ different strategies, including the use of piezoelectric elements to transfer vibrations - "" "to moving members.These types of devices are inefficient, expending considerable energy in the generation of off-axis movement, or orthogonal, to the intended work line. linear, circular or elliptical is transmitted repetitively, in a frictional manner, to the moving members A variety of driving methods have been used, including axial, torsional and displacement wave vibration phenomena, for example, US Pat. 5,036,245 and 5,134,334 of Onishi describe a device in which piezoelectric elements vibrate the legs of a "C" shaped structure such that the structure moves along a rail perpendicular to the legs. Yamaguchi transfers elliptical movement, one member exciting a longitudinal vibration in the direction of the length while another member excites a flexural vibration in the thickness direction. All of these prior art devices are unsuitable for the type of miniaturization used in accordance with the present invention. Many of the aforementioned problems are solved by the miniature linear motion actuator according to the present invention. The linear motion actuator of the present provides linear, controllable, precise movement in a substantially miniaturized device.

A linear motion actuator is disclosed to perform bi-directional linear movement, in increments. The linear motion actuator has a voltage source, first and second wafer elements presenting their respective first and second wafer surfaces in sliding engagement, butt, a clamping system for selectively holding the first and second wafer surfaces in relative position , an expandable member operatively coupled to the first wafer element for effecting movement of the first wafer relative to the second wafer, and an electronic control system, electrically connected to the voltage source, the grip means and the expandable member to control various characteristics of the movement. The electronic control system controls the amplitude, frequency and waveform of a voltage output to the clamping system and the expandable member, whereby the expandable member effects a bi-directional, selective, controlled linear movement of the first wafer in relation to the second wafer. Preferably, the semiconductor technology is combined with materials that change shape such as piezoelectric materials to provide a miniature linear actuator. An electrostatic-grip semiconductor wafer and a base semiconductor wafer, both having polished surfaces, are placed in slidable, butt-locking engagement. Wire terminals selectively provide an electrostatic gripping force between the wafers. A selectively expandable piezoelectric element is fixedly held at a first end of the gripping wafer. The second end of the piezoelectric element is coupled to an inertial mass. An actuating voltage is selectively applied to the piezoelectric element while a nip voltage is applied across the wafers, keeping the nip wafer in a position relative to the base wafer. The drive voltage is then rapidly changed and the piezoelectric element rapidly changes in size in response to the voltage change. The inertial mass inertially resists the rapid movement of the piezoelectric element, overcoming the gripping force and moving the gripping wafer relative to the base wafer. In an alternate technique, the polarity of the clamping voltage can be switched quickly at the moment the voltage is rapidly changed to the piezoelectric element. This helps to avoid the accumulation of load, and avoids the compression of the insulating layer. The cycle is repeated to perform linear movement in increments, precise. The movement of the linear actuator can also be easily reversed. The voltage in the electrostatic fastener and expandable member is controlled to provide appropriate frequency, amplitude and waveforms. The frequencies are adjustable, and preferably the frequency of the voltage waveform applied to the electrostatic fastener is some factor less than the "" voltage frequency applied to the expandable member. The voltage amplitude is adjustable to provide control of the output force of the actuator. The waveform of the voltage applied to the fastener and the voltage applied to the expandable member is controllable to control the output force of the actuator. An additional control of the phase angle difference provides control over the difference of the phase angle between the waveform of the clamping voltage and the voltage waveform of the expandable member. An embodiment of the double-grip actuator using semiconductor technology is provided to provide the double-grip linear actuator having usable force levels and repeatable increments regardless of the spatial orientation of the actuator. BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will now be described in detail with reference to the accompanying drawings, wherein: FIG. 1 is a fragmentary, fragmentary, sectional view of a miniature linear motion actuator according to FIG. present invention, sketched within a support housing; Figure IA is a sectional view of the layers forming the moving parts of the first embodiment; Figure 2 is a fragmentary view of a sliding electrical contact wire; Figure 3 is a sectional view taken along line 3-3 of Figure 1; Figure 4 is a fragmentary view, in detail, which outlines a second embodiment of the invention using double grip; Figure 5 is a simplified diagram that outlines the control console and the electrical connection to the elements of the miniature linear motion actuator according to the present invention; Figure 6 is a block diagram of the control system of the linear actuator; Figure 7 is an electronic circuit diagram of an exemplary control circuit used in accordance with the present invention; Figure 8 is a graph that outlines the force of r 'output of an exemplary actuator as a function of the clamping voltage and the voltage of the expandable member; Figure 9 is a graph that outlines the speed of the linear actuator as a function of the grip voltage and the output speed; Fig. 10 is a timing diagram for the first embodiment; Figure 11 is a timing diagram for the second embodiment; Figure 12 is a graph that outlines the speed of the single clamping actuator embodiment as a function of the clamping voltage for a variety of load sizes; Figure 13 is a graph that outlines the force generated by the embodiment of the single clamping actuator as a function of the clamping voltage for a variety of clamping frequencies; Figure 14 is a graph that outlines the force generated by the single clamping actuator embodiment as a function of the expandable member voltage for a variety of clamping voltages, with the phase between clamping voltage and limb voltage expandable as outlined in figure 8; Figure 15 is a graph that outlines the speed of the simple clamping actuator embodiment as a function of the external load for a variety of clamping voltages; Figure 16 is a graph that outlines an estimated creep speed of the simple clamping actuator embodiment as a function of the loading force for a variety of sliding weights; Figure 17 is a graph that outlines the force generated by the embodiment of the simple clamping actuator as a function of the sliding mass; and Figure 18 is a graph that outlines the force generated by the embodiment of the single clamping actuator as a function of the phase control variation of the waveforms of the expandable and clamping member. DESCRIPTION OF THE PREFERRED EMBODIMENTS A presently preferred embodiment will now be described in detail with reference to the accompanying drawings. Figure 1 shows a miniature linear actuator according to a first embodiment of the present invention. The structure of the first embodiment has a base and a slider that are continuously clamped together, and where the movement is effected by selectively overcoming the gripping force. The actuator is formed of a base 22, attached to the housing C, and a slider 24, which moves relative to the base, to provide force to a mass load 26. The energy for the operation is supplied by a plurality of wires 40, 76, 78 and 80, supplied as a control wire trunk 28. These wires are configured in a shape that retains the separation of the wires as the slider moves, to prevent electrical short circuits between the wires. Lots of these wires can be isolated to prevent any accidental short circuits.

A more preferable technique is to use rigid wires, as described herein. The housing for the device is generally shown in Figure 1, with the reference designation C, and refers to a part of the device that remains fixed and immobile. The housing is preferably cylindrical, and includes a plug 32 held in the cylinder. The base 22 includes the support member 30 and the wafer base 34, which is attached to the support member 30 by epoxy or the like. A detailed drawing of the layers forming the actuator is shown in Figure IA. The support element 30 is connected to the plug at a first end 31, and arranged in cantilever from there at its other end. This connection of the support element 30 to the plug 32 prevents movement of the base in a direction parallel to the axial direction of the cylindrical housing. An upper surface of the support member 30 is polished to have a roughness of the surface height of less than 1 μm / 5 mm linear length, and has an insulating layer 36 to insulate between the support element 30 and the base of wafer 34 that covers it. The insulation layer 36 is most preferably a native oxide. The wafer base 34 is formed of silicon, with an upper surface 38 polished. The surface 38 is covered by an insulating layer 39, which is preferably an oxide layer native to SiO2. Another layer of silicon nitride, Si3N4, layer 41, is preferably, but not necessarily, cultured on the native oxide layer 39. The Si3N4 layer helps to stabilize the native oxide layer 39 and also physically strengthens the layer. The resulting insulation layers 39, 41 are smooth, as they have been formed on the highly polished surface 38. Any technique known in the semiconductor industry can be used to form the Si02 / Si3N4 layers on the basis of wafer 34. The technique more preferred is to heat the surface of the silicon element in the presence of oxygen to form the native oxide layer thereon. This has the additional advantage that the resistance of the connection between the silicon and the insulation is extremely high. Less preferred techniques include splash and chemical vapor deposition of the oxide. The wafer base 34 receives a potential through a wire 40, which is electrically connected to it. The slider 24 includes the clamping wafer 46 and the expandable member 48. The clamping wafer 46 is also preferably formed of silicon with a lower surface 44 polished. An alternative embodiment of this invention forms the insulating layers 39, 41 on the polished surface 44 of the clamping wafer 46, instead of on the wafer base 38. An insulating layer 52 is formed on the opposite surface of the wafer of clamping 46, opposite the polished layer 44.

The expandable member 48 is attached to the insulating layer 52. A portion 49 of expandable member 48 is disposed cantilevered with respect to the underlying support elements. The expandable member 48 is formed of a material that changes in size in response to the application of a stimulus thereto. More preferably, the expandable member 48 expands and / or contracts in size based on an electric field applied thereto. The material that is currently preferred is a piezoelectric material, such as PZT. Another preferred material is the PZT material known as LTZ-2M, available from Transducer Products, of Connecticut, United States. Other materials may also be used, including a shape memory material such as nitinol, an electro-restrictive material such as PLZT, or a magneto-restrictive element that changes its dimension in response to an appropriate magnetic field. Any material can be used, so long as it allows the expandable member 48 to increase and reduce its size relatively rapidly in response to the application of a stimulus field. The expandable member 48 is glued to the insulating layer 52 that covers the fastening wafer 46 by an epoxy adhesive. The electrical terminal wires 54 and 56 provide an electrical potential through the expandable member 48 to control its expansion and contraction. The mass load 26 schematically represents the device receiving the output force produced by the movement of the slider relative to the wafer base. The mass load 26 includes a work interface rod 64 which is connected to the device that is intended to receive the load. The expandable member 48 is preferably attached to the bulk charge 26 by means of an insulating bonding adhesive 60, such as epoxy. The movement of the sliding assembly 24 is thereby translated into a linear movement of the mass load 26. The mass load 26 is preferably in such a way that it makes contact with the inner surfaces of the cylindrical housing C and thereby maintain a seal within it. of the cylinder. The work base seal 66 seals between the mass load 26 and the housing C in order to. prevent leakage of liquid to the engine. The seal 66 may be a truncated annular cone, or a "0" ring seal. In order to allow more sensitive control of the present invention, a sensor 300 may be placed in contact with the mass load. The sensor 300 can be a force sensor, accelerometer or the like. The sensor can be wireless or wired, and is used to provide feedback, as described herein. The force levels found at the distant tip are transmitted directly back to the expandable member 48 and the interface between the sliding wafer 46 and the base wafer 34. The controller 120 can directly detect any load changes on the working interface. 64 from a work piece by monitoring changes in voltage, current and phase angle. The controller 120 can be programmed to automatically respond to these changes by means of feedback mechanisms to adjust one or more readings to adjust the control of the slider waveform, the voltage amplitude, the frequency control 132, the shape control wave of expandable member 134, voltage control of expandable member 136, frequency control of expandable member 138, and phase control 126, as described. In this way, a specific displacement force ratio can be maintained within the energy and mechanical limits of the system. It is also anticipated that other sensors may be added to the system to assist the feedback control of the present invention. In operation, the device operates to produce movement as follows. It should be understood that although the explanation given herein is an explanation of the forward movement of the engine, the operation in the opposite direction produces a reverse movement of the motor. A first step of the operation provides a clamping force by applying an electric force between the clamping wafer 46 and the wafer base 34. This clamping force is carefully controlled, as explained herein, such as to hold the clamping member in position relative to the wafer base under most circumstances, including a slow expansion of the expandable member 48. The force is not so strong as to prevent separation between the grip wafer 46 and the wafer base when applies sufficient inertial force from the maximum velocity contraction of the expandable member 48. The gripping force is important as the gripping force must be sufficient to maintain the connection between the wafers while pushing towards the mass charge. The clamping force is one of the important parts of this engine. It is well known in physics that an electrostatic clamping force is expressed as follows: Fclamp = E AV2 / x2 (1) where E is the dielectric constant of the insulating material, A is the surface area of the wafers, V is the applied voltage between the two wafers, and x is the separation between the two wafers. The separation between the wafers, of course, is the thickness of the insulating layer 39, 41. Equation (1), therefore, demonstrates that the clamping force is inversely proportional to the square of the thicknesses of the insulating layer that separates the base of the slider. As this thickness increases, the area of the grip layers must increase proportionally to the square of this thickness. Therefore, it can be seen that a thicker insulation layer between the wafer base and the slider needs the wafer base and the slider to be larger in area to provide comparable strength. The design of Judy and collaborators wore a shirt Teflon between the layers. This Teflon jacket was around 63.5 μm thick. In order to obtain sufficient clamping force between the base and the slider, therefore, the surface areas of these two elements need to be relatively large compared to the present invention. In contrast, the present invention teaches the use of semiconductor materials, which allow to use extremely thin insulating layers, for example from 50 Angstroms to 2 μm in thickness. They can very accurately process silicon and other materials using conventional semiconductor miniaturization techniques. This processing allows extremely thin insulating layers with a high degree of polishing. Although the insulating layers can be as thin as 50 Angstroms, the preferred thickness for the insulating layer 42, according to the present invention, is 1 μm. This value is almost two orders of magnitude thinner than the insulating layer of Judy and collaborators, and therefore allows the resulting structure to be four orders of magnitude smaller (since the area is not a squared term, it is distance) for a similar holding force. The reduced size for the same clamping force allows an increased miniaturization. Returning then to the operation, once the slider is grasped to the base with an appropriate amount of gripping or clamping force, the expandable member 48 is slowly increased in length, for example gradually over the course of 1 ms. This increase in length pushes the load of mass "26" in the direction of increase in length.This slow increase does not exceed the clamping force between the slider and the base.The overall result is that the mass load is pushed forward at a magnitude proportional to the magnitude of the possible expansion of the expandable member At this point, the voltage across the expandable member is reduced rapidly, for example at 200-500 ns, to cause the expandable member to be reduced in size at the minimum time possible The inertial force of the fast shrinkage produces enough force between the slider and the wafer base to overcome the clamping force, and causes the slider to rise from the wafer base. and moves the slider forward on the wafer base.The magnitude of the gripping force is explained in more detail herein, but it should be noted that the gripping force must be r set sufficiently high so that when the expandable member is slowly increased in length, the gripping force is sufficient to resist this force and maintain the position of the slider relative to the wafer. However, the gripping force is not high enough to withstand the inertia caused when the size of the expandable member is reduced to its maximum rate. This high inertia overcomes the inertial force and causes the slider 24 to move relative to the wafer base 34 against the force caused by the grip. This completes the operation cycle, and the next cycle is then started to move the mass load 26 further forward. As it can therefore be seen from the foregoing, the present invention, using materials and wafer semiconductor technology, allows the clamping wafers to be more closely spaced than was possible in the prior art. This increases the output force and speed for a device of similar size, and allows the device to be much smaller. In fact, the device of the present invention can be 632 = 3969 times smaller than the device of Judy et al. For similar strength characteristics. Another advantage of the present invention is obtained from the different mode of operation used in accordance with the present invention. Judy et al. Reported that, during each cycle, the electrostatic grip was turned off during the time the slider moved relative to the wafer base. Nevertheless, during the time the grip is turned off, the effects of gravity can affect the position of the slider relative to the base. This means that the device would operate differently, depending on the position in which it was being maintained. In contrast, the techniques of the present invention retain the gripping force at all times. The present invention does not extinguish the grip, but rather fixes the clamping or gripping force appropriately to an appropriate value that can be kept constant. In a first mode of this first embodiment of the invention, the grip voltage is maintained at a constant value. In a second mode of this embodiment, described in more detail herein, the grip voltage varies cyclically. This cyclic variation eliminates the load accumulated in the substrate. Any semiconductor material, as well as many metals, can be used for clamping wafers. Crystalline silicon is the preferred material, however, because it is readily available, strong, easily capable of forming a native Si02 insulating layer thereon and also easily processed using conventional semiconductor techniques. Amorphous or polycrystalline silicon can also be used. Germanium arsenide and gallium arsenide are also good materials, but are more brittle. They are capable of being used, but less preferred. Also capable of being used, but still less preferred, are silicon carbide, gallium nitride, and gallium phosphide. Metals, for example aluminum, can also be used, but their native oxide is not reliable. A thin stainless steel film can be used, but the thin oxide layer would need to be sprinkled on it. This forms a more granular surface. Copper, bronze and gold can also be used. The preferred process for making the device, therefore, involves obtaining a silicon wafer, polishing the surface to obtain a flat surface, cultivating the oxide by heating the surface in the presence of oxygen, and then forming Si3N4 on Si02 by a conventional technique. of chemical vapor deposition. Figure 2 shows a detailed connection diagram of each of the wires 76, 78, 80 and their accompanying cylinders 70, 72, 74. Each of the wires 76, 78 and 80 is formed from a rigid rod, connected at one end through the control wire trunk 28, and having a fixed length. Each wire, for example 76, is of such length that it will remain inside its associated cylinder 70 in all possible positions of the slider. Each of the cylinders is connected by a wire terminal, for example 50, to its connected location. Each of the wires 76, 78, 80 of the control wire trunk 28 is slightly smaller in external diameter than the internal diameter of the cylinder, but includes a loop 120 at the point where it contacts the inside of the cylinder. Thus, the wires 76, 78, 80 contact the inside of their associated cylinder 70, 72, 74, and form a sliding connection as the expandable members move relative to each other. The wires slide relative to the cylinder during this time. However, the cylinder itself does not move, and the connection 50 does not move. Figure 3 shows a cross-sectional view along the line 3-3 in Figure 1, showing the positions of the cylinders 70, 12 and 14 and their connections to the layers. Figure 4 shows a second embodiment of the present invention, which is a linear actuator using a more conventional double grip technique. The embodiment of Figure 4 shows only a portion of the overall device, that portion being the part that differs from the portion of Figure 1. Figure 4 includes a similar support member 30 and the wafer base 34 with the layer isolate 44 on it. The slider 84 of the embodiment of Figure 4 is totally different from the slider of the first embodiment. The slider 84 includes two separate pieces, including a proximal slider 86 and a distant slider 88. Each of the slider pieces includes a respective terminal wire 90, 96, attached thereto. Each of the sliders also includes an extreme bottom polished surface. The proximal slider 86 includes the polished surface 92 and the distant slider includes the polished surface 98. Each of these polished surfaces abuts against the insulating layer 39 in the wafer base, it being understood that the insulator may be similar to the insulator of Figure 1 , IA and alternatively can be formed on the lower surface of the slider. The operation of the system of Figure 4 is somewhat different than the operation of the single gripper motor of Figure 1. Figure 4 uses a double grip technique, whereby different slider portions are clamped repetitively, followed by expansion. or contraction of expandable element 48 to move them forward. The device can be moved in the direction to the right of Figure 4 in the following manner. First, the proximal slider 86 is clamped with the expandable member 48 in its maximum contracted position. The distant slider 84 is not grasped at this time. The expandable member 60 is then expanded to its maximum expansion state, thereby pushing the mass load 26 to the right of FIG. 4. At this time, the remote slider 84 is held, and the proximal slider 86 is released. The expandable member 60 is then returned to its contracted length to pull the proximal slider to the right in Figure 4. At this time, the proximal slider 86 is again gripped, and the cycle begins again. The embodiment of Figure 4 is highly miniaturizable due to the semiconductor materials that are used. The movement of both embodiments of the invention is controlled by various parameters, including the voltage for clamping, the voltage across the expandable piezoelectric elements, the repetitive voltage frequency, and the voltage waveform, i.e. the change of voltage with respect to time. Figure 5 shows the power control console 120, which controls the operation of these input parameters. The power control console 120 controls all the voltages, frequencies and phases of the various elements. The magnitude of the grip or clamping voltage is adjusted to control the operation of the actuator according to desired characteristics. As explained above, the force between the base and the slider is proportional to the magnitude of voltage used for clamping. Therefore, the clamping voltage sets the base level of the force that holds the slider and the base together. When the expandable member expands, and pushes against the mass charge, the mass charge will only move forward if the force produced by pushing against the load does not exceed the clamping voltage between the slider and the base. Therefore, a clamping voltage must be set keeping the load in mind; a very small clamping voltage will not produce enough force to drive a specific load. On the other hand, the clamping voltage must be overcome by the inertia of the expanding, rapidly contracting member. A clamping voltage that is too high prevents the expandable member from returning sufficiently, and therefore shortens the length of the passage. As described above, the expandable member is expanded and contracted repetitively. The frequency of this expansion and contraction is based on the physical characteristics of the system. The expandable member, for example, takes some time to expand and contract. In the embodiment described above, the expansion is made relatively slowly, for example 1 ms. The contraction occurs at the maximum possible material velocity, but this also takes a finite time, for example 250 ns. The frequency of repetitive operation can not be faster than the time that is physically necessary for these materials to expand and contract. It has also been determined by the inventors that the phase between the voltage waveform of the expandable member and the voltage waveform of the clamping member affects the magnitude of the force that can be supplied by the device. An experimental graph of this information is shown in Figure 18. It should be seen that usually the phase should be around zero, but some small adjustments can improve certain characteristics. Figure 5 shows the control console including a slider control unit 122, a control unit of the expandable member 124, and a relative phase control unit 126. The slider base control unit 122 includes knobs suitable for turning of potentiometer, shown schematically as the waveform control 128, the amplitude control 130, and the frequency control 132. These potentiometers correspond to those of Figure 7 described herein, and it should be understood that the control circuit 120 You can have more knobs than shown.

The slider waveform control 128 generally controls the waveform of the slider. The voltage amplitude control 130 controls the magnitude of the voltage between the wafer 46 and the wafer base 34 to change the magnitude of the electrostatic attraction. Due to the characteristics of the materials, a linear change in the amplitude of the voltage can cause non-linear effects. The voltage amplitude control knob can be weighted, for example logarithmically, to compensate for such effects. The frequency control 132 controls the repetitive rate at which the waveforms are produced. For the preferred mode, this frequency is maintained between about 10 and 1,000 Hz. The expandable member control unit 124 similarly comprises an expandable member waveform control 134 which controls the characteristics of the waveform applied to the expandable member. For the first embodiment, this waveform must be of slow elevation, but rapid fall. For the second embodiment, the waveform can have any desired characteristics. The adjustable amplitude control 136 controls the amplitude of the voltages used for clamping. The adjustable frequency control 138 changes the frequency of this voltage. The phase control unit 126 controls the timing between the clamping voltage and the expansion voltage. Preferred timing characteristics are described herein. A block diagram of the circuit inside the control console of Figure 5 is shown in Figure 6. The frequency generator 204 produces the frequencies that will be used to drive the linear actuator. These frequencies are adjustable in a certain range. The output of the frequency generator 204 is received by the phase control unit 206, which produces two outputs, separated in phase for a selectable time. One of the outputs excites the piezo waveform generator 218, and the other output is split to excite the clamp waveform generator 216. It should be noted that although the preferred embodiment of the invention provides a waveform of grip, it is also contemplated, although less preferred, to excite the motor using a constant clamping voltage. The address control 212 controls the direction in which the motor is running, and is connected to the piezo wave generator 218, and to the clamp voltage actuator 214, which drives the clamp waveform generator 216. The device Clamping voltage 210 produces the clamping voltage that will be used to grip the slider to the base. According to a preferred embodiment of the invention, the output of the force sensor 300 is used to direct the magnitude of this voltage in order to produce a desired amount of force. As explained above, the expandable member 48 expands or contracts according to the control of the control console 120. These three separately controllable parameters, the waveform control of the expandable member 134, the voltage control 136 and the frequency control 138, affect the expansion and contraction of the expandable member 48. The voltage control 136 generally controls the magnitude of the change in length of the expandable member 48. The frequency control 138 controls the periodic movement of the expandable member 48. The control The waveform of the expandable member generally controls the inertial properties of the expandable member 48 and is attached to the ground load 26. A specific form of an electrical control circuit to provide control over the parameters discussed above for the first embodiment is sketched in figure 7 as control circuit 200. The circuit sketched in figure 7 can be fabricated total or partially on one of the silicon wafer (s) carried within the linear actuator of the present invention, preferably at base 30 in area 500, using conventional semiconductor techniques. The DC power source 202 includes the high voltage source, direct current 220 for energizing and expanding the piezoelectric element and a lower voltage source 222 for driving the logic, for example at 12V. The voltage source 220 can be variable by the operator and / or by feedback of the sensor 300 to achieve optimum power of the linear actuator. The output value of the voltage source 220 can vary between 15 and 1,000 volts, the preferred voltage being around 500V. The frequency generator 204 of Figure 7 produces a frequency that is used to produce wafer excitation waveforms. The frequency generating circuit 204 includes an internal frequency oscillator 224, and an external input gate 226. The internal oscillator 224 uses an operational amplifier oscillator to produce a frequency based on the magnitude of the feedback resistance in the amplifier. 236. The frequency selector switch 230 controllably switches the feedback resistors 232 and the capacitor 23. The system oscillates at a frequency that depends on the RC time constant, and therefore produces a frequency based on the position of the switch 230. The bias resistors 238, 240 and 242 provide a bias voltage to the inverting input of the amplifier. operations. The frequency generating circuit 224 may alternatively be a variable divider attached to the output of a crystal, or it may be a programmable frequency divider integrated circuit. In this embodiment, an external frequency can also be added through the terminal 226. The operation amplifier 244 compares the input frequency with a DC bias of the adjustable resistor 246 to adjust its amplitude to match the characteristics of the system. The frequencies of the external input 226 and the internal frequency oscillator 224 are given as input to two contacts of the switch 228. The output of the switch 228 is passed to the phase change control unit 206. The change control unit of phase 206 provides two output frequencies, selected such that the phase delay between those output frequencies has a desired characteristic between 0 and about 0.1 μs. The phase control circuit 250 and the phase control circuit 252 each have separately adjustable delay characteristics. The circuit 250 includes the fixed resistor 254 and the variable resistor 256, as well as a capacitor 258. The combination of these resistors and capacitances forms an RC circuit, which delays the elevation of the waveform. The RC time constant is varied by varying the value of the resistor 256. This delays the passage of the waveform and thus changes its phase angle. Similarly, the adjustment of the resistor 266 delays the passage of the output form to the output. A switch 276 controls whether or not the phase change will be used. In a first position, the switch 276 directly connects the inputs of the phase change unit to the outputs, thereby preventing any phase change. In the second position, the phase changes are controllable. The signal output of the circuit 250, either switched phase or directly connected, is coupled to the frequency divider 208. The divider 208 is simply a type D flip-flop with its non-Q output connected to its input D to thereby divide the frequency of entry between two. The output is coupled through a variable resistor. The output voltage is supplied to the grip waveform generator 216. Of course, this may be a programmable division by the counter N or any other divisor known in the art. The voltage for electrostatic clamping of the base to the slider is produced by the clamping voltage generator 284. The element 284 includes a voltage divider 290, 292, 294 connected to the inverting input of an operation amplifier 288. The output of the operation amplifier 288 drives the gate of an energy MOSFET 286 which has a grounded drain, and a source connected to the output with a resistor of polarization 285. The source is also directed through a feedback loop with the sensor 300 and the resistor 302 to the non-inverting input of the operation amplifier. It will be appreciated that the operation amplifier 288 is connected as a comparator, and its output determines the voltage drop across the MOSFET (metal oxide substrate field effect transistor) 286. The source of the MOSFET 286 is connected to a filter capacitor 298, whose output produces the voltage at input terminal 296. This output voltage 296 becomes the clamping voltage. Element 212 is an engine steering control. By closing one of the two switches, the motor can be inverted selectively. The switches selectively operate the clamp voltage actuator 214, which includes the comparator amplifiers 308 and 310. Each comparator 308, 310 has its negative input connected to a variable voltage of the voltage divider 312. Depending on the positions of the switches 304 and 306, the output voltages of the amplifiers 308, 310 are connected to the inverting inputs of the operation amplifiers 316, 318 within the clamp waveform generator 216. The positive inputs of these operation amplifiers receive the voltage of output of the division circuit 208 between two. Each of the amplifier circuits in the voltage waveform generator has a similar construction. The operation amplifier 316 has an output that excites the base of the MOSFET 320, which is configured as a follower. The source of this transistor 320 is connected through a variable resistor to the gate of another MOSFET 322, also configured as a follower. The source of the MOSFET 322 configured as a follower has an output terminal 346. Similarly, the circuit including the operation amplifier 318 produces an output voltage at the terminal 348. The output terminals 346 and 348 are respectively connected to the slider. 46 and the wafer base 34. It should be appreciated that by changing the positions of the switches 306, 308, the voltage between those values is also changed to thereby change the operating direction of the motor. The other output of the phase control unit, of the variable resistor 278, is coupled to the input of the piezoelectric element waveform generator 218. This second phase control element is connected to the inverting inputs of the operation amplifiers. 352, 354. The non-inverting inputs of both operation amplifiers receive respective signals from the switches 304, 306. The operation amplifiers, configured as comparators, electrically control the gates of the MOSFETs 364, 366. These MOSFETs are connected as followers, the source of each MOSFET connected through a variable resistor 372, 374 and a ground resistor 380, 382, to a power MOSFET 376 also connected as a follower. The sources of the MOSFETs 376 and 378 produce voltages that are coupled to the output terminals 388, 392. These terminals are connected to the electrical terminals 54, 56 and thereby control the expansion and contraction of the expandable member 48.

In operation, the circuit of Figure 7 produces voltage waveforms for electrostatic clamping and the expandable element. When the switch 304 is closed, the respective amplifiers 352 and 308 are turned on, thereby applying a specific voltage to the amplifiers 316 and 318. These voltages are applied to operation amplifiers 316, 318 in the clamp waveform generator 216 The other inputs of the operation amplifiers are excited by the divider output between two 208. This results in a voltage that is continuously reversed through the output terminals 346, 348 at half the excitation frequency of the member. expandable The actual shape of the voltage curve depends on the RC time constant controlled using variable resistors 328, 330. The closure of switch 306 turns on the voltage drivers of the opposite direction. Switches 304 and 306 also control the operation of the waveform generator of piezo element 218. When both switches 304 and 306 are open, the waveform generator 218 is running under vacuum. Closing the switches 304 also provides a low level voltage to the positive input of the operation amplifier 352, thereby turning it on and allowing the output voltage received from the phase control 206 to pass. Alternatively, the switch 306 turns on the amplifier 354, with This allows you to operate using the same voltage. It can be seen that the overall effect of the closing switches 304, 306 is the control of the direction of movement of the linear actuator. By just closing the switch 304, the waveform generator circuit energizing the MOSFET 376 is started. By closing switch 306, the waveform is inverted through terminals 388 and 392. As described above, the speed of the actuator is controlled by changing the frequency output signal of frequency generator 204. However, for any power Given input, the speed output must be compensated against the workload. The voltage of the expandable member controls in the most direct way the energy. The clamping voltage controls the compensation between speed and force. A low clamping voltage allows a higher speed but less force. As the clamping voltage is lower, the clamping force between the slider and the base can be maintained only for a smaller amount of force. However, since the clamping force is relatively smaller, the inertial springing operation allows the slider to move forward a little more. The relationship between speed and force is more complicated and less linear. The features are more easily modeled, which has been done by the inventors and will be explained with reference to the following preferred embodiment. The linear actuator of the present invention uses a piezoelectric element that is preferably 38.1 mm in length. The preferred width of the piezoelement is 6.35 mm.

This provides a preferred clamping surface area of 234 mm2. The preferred thickness is 0.8 mm. However, more generally, the actuator can be between 1 and 250 mm in length, between 0.1 and 50 mm in width, and 0.01 to 5 mm in thickness. The preferred piezolement has a mass of 1.4 g, although it can vary between 0.01 and 450 g. The preferred mass of the slider is 30 g, although it is conceivable to make the mass of the slider between 1 g and 10 kg. The insulating layer 39 is preferably formed of Si02 and Si3N4, as shown in Figure IA. Preferably, the Si02 layer has a thickness of about 0.75 μm and the Si3N4 layer of about 0.15 μm. Both layers can be as thick as 3 μm or as thin as 50 Angstroms. The silicon clamping wafer preferably has a thickness of 0.036 mm, but more generally between 0.01 and 1 mm. The system operates in accordance with the following preferred parameters: It should be evident from the above that the performance characteristics of the actuator depend on the physical properties of the system. Figures 8 and 9 show envelopes of general performance for a linear actuator, it being understood that the absolute values of the curves can depend on the loads and real inertial masses selected in the surface areas of subject. The point of Figures 8 and 9 is that of each mass range and clamping area, a different set of curves define the performance envelopes, and the values in these curves can be chosen to optimize different characteristics. By specifying different values for any given application, the largest inertial mass and the largest surface area of clamping will usually be selected. Figure 8 shows the output force reaching its optimum value at point 146. An increase in the clamping voltage initially produces a higher output force because it causes the slide wafer to be held in place more tightly as the clamp is expanded. expandable member. However, too much clamping voltage reduces the output force, because it prevents the expandable member from moving forward when the voltage of the expandable member is released. The surface area of clamping and the voltage are related to each other, and as the clamping surface increases, the voltage necessary to produce the same magnitude of clamping force is reduced. Figure 9 shows a similar relationship between the force and the clamping voltage. A peak speed can be selected by adjusting the clamping voltage. However, when the clamping voltage becomes too high, the speed begins to fall due to the increased difficulty in overcoming the clamping force to move forward. The output force also increases with the increased voltage. The step length is a function of the elastic limit of the expandable material and the voltage applied to the expandable material. As can be seen from the drawings of Figure 8, the optimum force and velocity can be set separately, and it may be necessary to set the values at different values to achieve different results. Figure 10 shows a typical set of waveforms generated by the control console 120 for control of the actuator of the preferred mode of the first embodiment of the present invention. For the purposes of this time chart, assume that the expandable member 48 is oriented such that when the voltage at the electrical terminal 54 is positive, the member 48 is expanded in length. The voltage 148 represents the voltage applied to the wafer base, and the voltage 150 represents the voltage in the slider. The voltage difference between the voltages 148 and 150 represents the clamping voltage. According to a mode of the present invention, the clamping voltage is simply maintained at a constant value all the time. This produces satisfactory results, but is less preferred than the technique described herein. The inventors of the present have found that when a constant clamping voltage is maintained all the time, it causes accumulation of charge through the elements and also causes increased attraction between the wafers, causing the separation distance between the slider to be reduced. 24 and the base 22. According to the preferred mode of the present invention, the voltage across the slider and the base is maintained for a relatively short time, for example 1-4 ms. At the end of that time of 1-4 ms, the voltage across the slider / base is reversed in polarity. This causes a momentary time during which the voltage across the base of the slider approaches zero. At this time, the slider and the base separate slightly, followed by an increased attraction. However, this increased attraction has load-coat characteristics of the opposite direction so as to prevent the accumulation of charge. Turning to the time graph, before point 170, the time graph shows that the voltage between the slider and the base is negative; that is, the voltage in the slider is less than the voltage in the base. At time point 170, the voltage across the electrical terminals is inverted. This momentarily loosens the electrostatic clamping force between the clamping wafer 46 and the wafer base 34, but essentially re-tightens the clamping force immediately. At this point, the voltage 154, which is the voltage that controls the expansion of the electrostatic element, is made r * -. Fall to zero as quickly as possible. This causes a rapid contraction of the expandable member within a time of hundreds of nanoseconds. As described above, the rapid contraction causes the slider to overcome the clamping force and move slightly forward. At the time point 172, the voltage 154 slowly begins to increase. This causes a slow increase in the length of the expandable member 48. This slow increase pushes forward the mass load rather than overcome the clamping force. When the expandable member 48 is fully expanded, at time 174, the voltage across the member 48 falls back to zero, thereby repeating the previous step, causing further forward movement. By repeating these steps, the system has an intermittent forward motion continuously. The backward movement is carried out opposite to the forward movement, as shown in the negative sense line 155, in the time 176, etc. The waveforms for the second embodiment are slightly different and are shown in Figure 11. A cycle can be considered to begin at time 180, when the voltage potential on curve 166, which represents the potential at the terminal electric 90 that excites the next slider 86, is made to fall to zero. At the same time, the voltage on line 168, connected to the distant slider 84, rises. This allows the proximal slider 86 to slide freely relative to the wafer base, but grabs the distant slider 84 relative to the wafer base. At this time, the voltage 154 is reduced, which excites the expandable member 48, so that the expandable member contracts in size. As the distant slider has been clamped, the proximal slider 86 is moved to the right in Figure 4. After total contraction, at time 182, the voltages are inverted, the distant slider being released, and the next slider being clamped. The voltage across the expandable member 48 is then increased, causing the distant slider to move to the right in Figure 4. Of course, the movement in the opposite direction is carried out using precisely the opposite steps. Figures 12-18 show the interrelationships between clamping voltage, expandable member voltage, voltage amplitude, waveform, frequency, phase angle difference and clamping force. Figures 12-18 show the actual values for specific prototypes used in accordance with the present invention. Figure 12 shows the speed of an element plotted as a function of the electrostatic clamping voltage for various extl loads. For each design, there is an optimum range in which too little or too much clamping voltage produces inferior results. If the clamping voltage is too low, for example less than 50 volts, as shown in FIG. 13, then it is not possible at all to move. Figure 13 shows the output force plotted as a function of the electrostatic clamping voltage for various frequencies of the clamping cycle. The increase in clamping voltage produces an output force that increases until it reaches its platform level. The lower frequencies have less overall effect than the highest frequency tested.

The control frequencies of the voltage inputs to the expandable member and the clamp wafer generally control the repetitive rate of the steps or steps of the actuator. Figure 14 shows a graph between the voltage applied to the expandable member and the force produced for various clamping voltages. It should be noted that for different clamping voltages, different expansion voltages are possible for the piezoelectric element. Figure 15 shows a relationship between the speed and mass of the external load for different clamping voltages. Figure 16 shows a three-dimensional plot between speed, load and load force. Figure 17 shows the force as a function of the mass data of the slider, showing that the output force increases linearly, at least for a specific range, with the mass of the slider. Figure 18 shows a graph of the force versus the phase of the PZT fasteners. Figures 8, 9 and 12-18 show the wide range of operating characteristics that are controllable through mathematical and experimental modeling that produces a design procedure specific to the application. The actual use of a linear actuator constructed in accordance with the present invention yields a required total displacement, a minimum step size, a maximum speed, a volumetric size restriction, and a maximum force. The design procedures include predicting whether such a set of constraints can be satisfied and then guiding the design of a complete linear actuator, in accordance with the present invention for that task. Another advantage of the present invention is the ability to control movement by either displacement, force or a combination of both. Traditional linear motors can only be excited by specifying displacements because there is a high mechanical impedance between the motor and the workpiece, ie the load created by the workpiece at the far end of the linear motor. For example, in the case of a rotary motor that drives through a rotary to linear coupling, such as a worm and a worm gear, even medium levels of force at the far end are not transmitted back to the motor due to the mechanical advantage of the high gear ratio. This "Condition makes force control impossible without additional sensors added to the far end to the workpiece interface. The present invention preferably uses the sensor 300, which senses force or displacement, and feeds back a signal indicative thereof. However, alternatively, the controller 120 can directly detect any load changes in the work interface 64 from a work piece by monitoring changes in voltage, current and phase angle. The controller 120 may be programmed to automatically respond to these changes by means of feedback mechanisms to adjust one or more readings to the following: slider waveform control 128, voltage amplitude control 130, adjustable frequency control 132, control of expandable member frequency 138, and phase control 126. In this manner, a specific force / displacement ratio can be maintained within the energy and mechanical limits of the system. The device of the present invention is capable of small steps or steps of precision in the range of 10-30 nanometers throughout the range of displacement of the device, which can be between 3.3 and 12 cm. The actual theoretical displacement is limited only by the length of the wafer base. However, according to another preferred modification of the present invention, the slider 24 is connected to the housing C by a spring which limits the length of movement of the slider relative to the base. This spring may preferably polarize the slider at a specific position; whereby, when the clamping force is released between the slider and the base, the spring biases the combination back to a zero position. The preferred device fits within a 3/8 tube, but still produces 1.2 foot-pounds of force in its range. Although only a few embodiments have been described in detail, those skilled in the art will certainly appreciate that many modifications are possible in the preferred embodiment without departing from its teachings. For example, mechanical equivalents can be used for electrostatic fasteners. Mechanical polarization methods to increase the friction at the interface of the slider wafer to the base wafer would have the advantage of providing performance achieved with continuous electrostatic clamping. In addition, the substitution of mechanical polarization methods can eliminate the additional electronic control required by the electrostatic fasteners. All these modifications are intended to be encompassed within the following claims.

Claims (37)

1. CLAIMS 1. A linear actuator, comprising: first and second wafer elements having first and second wafer surfaces in slidable engagement, butt; an electrically insulating thin film layer of natural oxide formed on one of said first and second wafer surfaces between said first and second wafer surfaces and said first and second wafer elements; means for electrostatically clamping • * - selectively said first wafer surface relative to said second wafer surface; and inertia generating means operatively coupled to said second wafer element, to move said second wafer element relative to said first wafer element.
2. 2. A device as in claim 1, wherein said insulating layer is between 50 Angstroms and 2 μm thick.
3. 3. A device as in claim 1, said insulating layer comprising a thin film bonded to said first wafer surface.
4. 4. A device as in claim 1, wherein said insulating layer comprises a thin film bonded to said second wafer surface.
5. A device as in claim 2, wherein said first wafer element is formed of silicon, and said insulating layer comprises a thin film of native Si02.
6. A device as in claim 1, wherein said first wafer element comprises a material selected from the group of materials consisting of: crystalline silicon, amorphous silicon, polycrystalline silicon, germanium, gallium arsenide, silicon carbide, gallium nitride , gallium phosphide, aluminum, stainless steel, copper, bronze, and gold.
7. A device as in claim 1, said second wafer element comprising a material selected from the group of materials consisting of: crystalline silicon, amorphous silicon, polycrystalline silicon, germanium, gallium arsenide, silicon carbide, gallium nitride, Gallium phosphide, aluminum, stainless steel, copper, bronze, and gold.
8. 8. A device as in claim 1, wherein said inertial generating means comprises means that change so that they have a longitudinal axis configured to substantially change shape along an axis of movement of the device.
9. A device as in claim 8, wherein said shape-changing means comprise a material selected from the group of materials consisting of a piezoelectric material, a shape memory material, an electro-restrictive material, and a magneto material. restrictive.
10. A device as in claim 1, wherein said first and second wafer surfaces have a roughness of surface height of less than about 1 meter in surface height per 5 mm in linear length.
11. 11. A linear actuator device, comprising: a housing; a base member, rigidly coupled to said housing; an insulation layer, covering at least a first surface of said base element; a sliding element, located having a first surface thereof abut against said insulation layer, said sliding element including a portion formed of a material that can be selectively changed in size by means of the application of a stimulus thereto and having an area of load interface that connects to a load; a first power source connected to hold said slider to said base with a first force; and a second source of connected power to provide said stimulus to said portion to expand said portion, said first and second energy sources producing energy of a magnitude such that a first magnitude of said stimulus does not exceed the first force between said slider and said base, but a second magnitude of said stimulus, different from said first magnitude of said stimulus, exceeds said first force between said slider and said base.
12. 12. A device as in claim 11, where said stimulus is electrical.
13. 13. A device as in claim 11, wherein said first stimulus is a slow change in size of said portion, and said second stimulus is a rapid change in size of said portion.
14. A device as in claim 13, wherein said first energy source comprises a first voltage source for producing a clamping voltage between said slider and said base, and wherein said second power source comprises a second voltage source connected to said power source. selectively expand and contract the size of said portion, said second voltage source producing a waveform with a slower rise time and a faster fall time.
15. 15. A device as in claim 13, wherein said base is formed of silicon, and said insulator is a native oxide of SiO2 on said silicon.
16. 16. A device as in claim 15, further comprising a layer of Si3N4 on said layer of SiO2.
17. 17. A device as in claim 15, wherein said layer of Si02 is less than 2 μm thick.
18. 18. A device for producing linear movement of a member relative to another member, comprising: a base member, formed of a semiconductor material and including an insulating layer of natural oxide film thereon of a thickness less than 2 μm; a slider, having a surface in contact with said insulating layer, said slider including a portion formed of a material that changes in size when the voltage is applied thereto; and a control console, which produces a first voltage that electrostatically secures said slider to said base member, and which produces a second voltage that expands said material and contracts said material so as to move said slider relative to said base against a force produced by electrostatic fastening.
19. 19. A device as in claim 18, wherein said second voltage includes a slow change in size of said portion, followed by a rapid change in size of said portion.
20. A device as in claim 18, wherein said slider includes a clamping wafer member and an expandable member, and wherein said clamping wafer member is a one-piece member that is clamped to said base during expansion and the contraction of said material.
21. 21. A device for producing linear movement of a member relative to another member, comprising: a base member, formed of a semiconductor material and including an insulating layer of natural oxide film thereon of a smaller thickness of 2 μm; a slider, having a surface in contact with said insulating layer, said slider including a portion formed of a material that resizes when voltage is applied thereto, said slider includes a wafer member and an expandable member, and where said fastening wafer member is a two-part member that includes a distal portion and a proximal portion; and a control console, which produces a first voltage that electrostatically secures said slider to said base member, and which produces a second voltage that expands said material and contracts said material so as to move said slider relative to said base, against a force produced by electrostatic fastening, and wherein said control console produces voltages that hold said distal portion while moving said proximal portion and holding said proximal portion while said distal portion is moved.
22. 22. A device as in claim 18, further comprising a plurality of terminal wires connected to said slider portion, each said terminal wire including a portion of rigid wire, a hollow member within which said portion is slidably received. of rigid wire, and a connecting portion connecting said hollow member with said slider portion.
23. 23. A device as in claim 22, wherein said rigid wires and said hollow member are cylindrical.
24. 24. A method for developing a linear motion actuator, incremental stepping, using electrostatic grip and an expandable member, the method comprising the steps of: determining an output workload value to be achieved by said linear actuator; determining a surface area value of electrostatic grip; determine an inertial mass value; using said workload value, said grip surface area value, and said inertial mass value to calculate a range of electrostatic clamping control voltage values; using said workload value, said grip surface area value, and said inertial mass value to calculate a range of expandable member control voltage values; selecting a range of sizes for said expandable member in accordance with said range of expandable member control voltage values; applying said value range of electrostatic grip control voltage values to said electrostatic grip; and applying said range of expandable member control voltage values to said expandable member; whereby said clamping control voltage and said expandable member control voltage effect a bi-directional linear movement, selectable, to said linear actuator.
25. 25. A method as in claim 24, wherein said workload value is force, velocity or both.
26. 26. A method of making a linear actuator, comprising the steps of: forming a base of silicon material; polishing a first surface of said base; heating said first surface in an oxygen environment to form a natural oxide film thereon; forming a slider element with a first polished surface, and bumping said first polished surface of said slider member against said oxide film of said base; and joining power supply lines to said slider and said base, so that said slider element can be electrically energized to be fastened to said base, and such that said slider element can be expanded by applying voltage to it.
27. 27. A method as in claim 26, comprising the additional step of forming a sliding connection with said electric supply lines, which allows the movement of said sliding element relative to said electrical supply lines.
28. 28. A method of operating a linear electronic motor, comprising the steps of: forming a base, an insulation layer, and a slider, with said insulation layer between said base and said slider; electrostatically clamping said slider to said base using a first force magnitude; applying a voltage to a portion of said slider that is formed of a material that resizes when voltage is applied thereto, to change a size of said portion to a first rate; releasing said voltage at a second rate different than said first rate; and fixing said first force to a quantity that is not exceeded by said portion that changes size at said first rate, but that is exceeded by said portion that changes in size at said second rate.
29. 29. A method as in claim 28, wherein said electrostatic clamping step comprises the step of periodically reversing the polarity of a voltage that is therethrough.
30. 30. A method of moving a mass load, comprising the steps of: rigidly coupling a base member to a housing; covering at least one first surface of said base element with an insulating layer; placing a first surface of a slide element abut against said insulation layer, said slide element including a portion formed of a material that can be selectively resized by application of a stimulus thereto; attaching a load to said slider; fastening said slider to said base with a first force; and providing said stimulus to change the size of said portion, using energy of a magnitude such that a first magnitude of said stimulus does not exceed the force between said slider and said base, but a second magnitude of said stimulus, different from said first quantity of said stimulus, overcome said first force between said slider and said base.
31. 31. A device as in claim 1, wherein said electrostatic fastening means is a voltage source.
32. 32. A device as in claim 31, wherein said voltage source produces an alternating voltage that alternates between producing a positive potential and a negative potential between said layers.
33. 33. A device as in claim 11, wherein said first energy source produces an alternating voltage that provides a first voltage between said slider and said base and then provides a negative voltage between said slider and said base.
34. 34. A method as in claim 28, wherein said electrostatic clamping step includes the steps of first applying a positive voltage between said slider and said base, and periodically changing said positive voltage to a negative voltage between said slider and said base.
35. 35. A device as in claim 11, further comprising a sensor that detects an output workload magnitude of said device, and retroactivates said quantity to control at least one of said energy sources.
36. 36. A device as in claim 18, further comprising a sensor that detects an output workload magnitude of said device and feeds back said quantity to control the characteristics of said control console.
37. 37. A linear actuator device, comprising: first and second wafer elements having respective first and second wafer surfaces in slidable, butt linkage; a voltage source, which produces a first output voltage that periodically varies between a positive and a negative direction, connected to electrostatically clamp said first and second wafer surfaces together; an expandable member operatively coupled to said second wafer member; and control means, electrically connected to said voltage source, said clamping means and said expandable member, for continuously synchronously controlling a first output voltage to said clamping means and a second voltage output to said expandable member, with which said expandable member effects inertially a linear movement of said first wafer in relation to said second wafer.