MX2008014050A

MX2008014050A - Vibration control of free piston machine through frequency adjustment.

Info

Publication number: MX2008014050A
Application number: MX2008014050A
Authority: MX
Inventors: Douglas E Keiter; Reuven Z-M Unger
Original assignee: Sunpower Inc
Priority date: 2006-05-05
Filing date: 2007-03-07
Publication date: 2009-01-26
Also published as: KR20090010103A; US20070256428A1; EP2016304A1; AU2007248879A1; JP2009536514A; CA2650092A1; WO2007130202A1; CN101438077A

Abstract

A method and apparatus for minimizing the amplitude of mechanical vibrations of a mechanical apparatus including a linear, freely reciprocating, prime mover coupled to and driving a reciprocating mass of a driven machine in reciprocation at a driving frequency. The coupled prime mover and driven machine have a spring applying a force upon the reciprocating mass to form a resonant main system having a main system resonant frequency of reciprocation. A driving frequency range over which the driven machine operates at an acceptable efficiency of operation is determined and stored. A parameter of the operation of the mechanical apparatus, such as the amplitude of vibrations or an operating temperature, is sensed and the prime mover is driven in response to the sensed parameter at a driving frequency that is offset from the main system resonant frequency of reciprocation, is within the driving frequency range of acceptable efficiency of operation and reduces or minimizes the amplitude of mechanical vibration of the mechanical apparatus under existing operating conditions.

Description

VIBRATION CONTROL OF FREE PISTON MACHINE THROUGH A FREQUENCY ADJUSTMENT FIELD OF THE INVENTION This invention is generally related to minimizing the mechanical vibrations of a mechanical apparatus that includes one or more masses activated in oscillation by a primary motor, of free oscillation, linear and with using the electronic controller that controls that primary motor .

BACKGROUND OF THE INVENTION Free, linear oscillating machines are frequently used as they provide improved durability, reduced wear, controllability and efficiency. Free swinging machines include linear compressors, Stirling free piston motors, Stirling coolers, cryocoolers and thermal pumps, linear motors and linear alternators. Linear oscillating machines oscillate with a controllable stroke and are not restricted by conventional cranks and crankshafts. However, free, linear oscillating machines cause substantial vibration since they have one or more masses that oscillate linearly within a common housing and / or are joined to a common support frame.

Typically, a main system or machine consists of multiple connected free oscillation machines. An oscillating machine is a free linear, primary oscillating motor such as a linear, electric motor or a free-piston Stirling motor which may also be referred to as a linear Stirling motor. The second oscillating machine is a free, linear oscillating load activated via a mechanical link by the main motor and may be, for example, a free piston compressor, a Stirling thermal pump or a chiller or an electric alternator. The oscillating masses composed of the primary motor and the activating load contribute to the vibration. This vibration is ordinarily undesirable and a variety of systems have been developed to minimize the amplitude of these vibrations. Typically, the free piston and other free, linear oscillating machines are constructed with one or more springs by applying a spring force to the oscillating masses. Both the primary motor and the machine that activates it can include springs. The springs may include one or a combination of mechanical springs as well as gas springs and magnetic springs. Magnetic and gas springs can be devices designed to provide a spring force or, more commonly, are the result of gas acting on a machine component and / or forces magnetic from electromagnetic devices or a permanent magnet system used in machines, such as alternators and electric linear motors. Together, the masses and springs of the free-oscillating, linear primary motor and the free, linear, activated oscillating machine form a main machine that is a resonant system. Commonly, the main machines are designed to operate at or near a resonant frequency as it maximizes their efficiency. The natural frequency of such a system is described according to the equation: where / = resonant frequency in cycles per second or Hertz, K is the spring constant composed in Newton / meter and m is the compound mass in Kg. The word "compound" is used to designate the sum of the respective masses and springs of The main machine and the terms "mass" and "spring" are used to include the compound mass or the spring when its effects are added together. The problem of vibration can also be complicated if a mechanical device consists of a main system or machine, it comprises a primary motor that activates an activated machine, which is also coupled to other equipment that includes one or more secondary vibration systems. Secondary systems can be attached to the main machine by mounting the secondary vibration system so that it is mechanically connected to the main system, for example, since both systems are mounted on the same support frame. Secondary vibration systems can be devices that are designed with masses and springs to oscillate during their operation or they can be devices that are not designed to oscillate as part of their normal function but that still have a mass connected to a structure that acts as a pier. A secondary vibration system that is coupled to the main system is a parasitic resonant system and is not designed to vibrate during normal operation. If the resonant frequency of the parasite resonant system is close enough to the activation frequency of the main machine, the parasitic resonant system can vibrate to an excessive amplitude. If the parasitic resonant system vibrates at the activation frequency and at less than 90 ° outside the phase with the main system, it can increase the total vibration of the mechanical device. The prior art has developed a variety of devices to reduce the vibration of a main machine. These are known with a variety of names including "vibration absorbers", although they are more correctly called vibration compensators because they do not "absorb" vibration. A vibration compensator is a secondary vibration system that is mechanically coupled to the main system usually by direct connection to it. Although the purpose of vibration compensators is to decrease the vibration that results from the oscillations of the main machine, they are desirably observed as a form of a secondary vibration system because they are not a part of the main system or machine. A common vibration balance system seeks to activate a balance, oscillation mass so that it applies forces to the main vibration machine that are equal but opposite to the forces generated by the vibration masses of the main machine. The activated mass of the vibration compensator can be activated by its own primary motor or, alternatively, it can be activated by the vibrations of the main vibration machine and tuned to resonate at the same activation frequency but designed to oscillate 180 ° outside the phase with the vibrations of the main page of vibration. An example of a system of the above nature is shown in U.S. Patent 5,620,068. Another system for reducing vibration is illustrated in U.S. Patent 6,040,672. A waveform induced in an activated electric motor signal is detected, moved within a control waveform and added with the motor activated current to reduce vibration. Although these systems perform satisfactorily under relatively stable operating conditions, under extreme variations in operating conditions, they may encounter difficulties. For example, a Stirling cycle cooler may experience variations in extreme ambient temperature. It can operate anywhere in the range of -40 ° C to + 60 ° C. If a Stirling cooler has a vibration compensator attached to it, these variations in temperature change the stiffness of its springs, thus varying its spring constant, and therefore cause the natural frequency of the vibration compensator to change. The effective spring stiffness of spring forces in the cooler may also vary in some way, although these variations generally have less effect since Stirling coolers typically have a relatively low Q while vibration compensators typically have a high Q (ie, acute resonant peak). Therefore, a relatively small variation in the natural frequency of the vibration compensator results in a large variation in its amplitude Effective oscillation if the activation frequency remains the same. Consequently, the ability of the vibration compensator to cancel the vibrations of the main vibration machine decreases substantially. Similarly, changes in temperature can also result in changes in electrical parameters which, in turn, can change the effective spring constant of the effects of the magnetic spring. The temperature can also change the dynamic behavior of a Stirling engine resulting in a change in its operating frequency. The non-linear behavior of the mechanical springs or structural components in response to the variation of the races can also change the natural frequency. As a result, a mechanical device with a vibration compensator can be well compensated and exhibit an acceptable amplitude of vibration under some operating conditions, but if the operating conditions are far enough from the pre-established operating conditions, the vibration compensator will become less effective since the change in operating conditions changes the natural or resonant frequency of the vibration compensator or changes its phase relationship to the main system or both. If the vibration compensator becomes less effective, the amplitude of the vibrations increases.

Similarly, the resonant frequency of secondary parasitic vibration systems coupled in the main system can also change as a result of changes in operating conditions. As a result, a secondary system that does not aggravate the vibration of the mechanical device under some operating conditions can become a problem when the operating conditions change sufficiently. A component of a mechanical device that was not a vibration problem can become a problem when the operating conditions change sufficiently. A parasitic vibration system can also be discovered after a machine is built. Although it is possible to build a vibration compensator that can vary its spring constant or otherwise vary its natural frequency of oscillation, the vibration compensator would be even more expensive than conventional vibration compensators. Vibration compensators are not only costly, they use space and add weight to a product. It is a feature and object of the invention to provide a vibration compensator by electrically compensating variations in the capacity of the vibration compensator to cancel the vibrations as a result of vibrations in operating conditions. Another object and feature of the invention is to provide a control system for a main, free-oscillating, linear machine that can compensate parasitic, secondary vibration systems. Another object and feature of the invention is to reduce vibration electronically by altering the controlled operating characteristics of a primary, free-oscillating, linear motor to compensate for any variety of causes or changes in the resonant frequency associated with a main free-oscillating machine , linear and any vibration compensator connected to it where the unbalanced changes resulting from changes in operating conditions would otherwise result in an increase in vibration. Yet another object of the invention is to compensate for changes in the resonant frequency of a main, free-oscillating, linear machine independently of, and in response to, changes in the operating conditions of the machine.

SUMMARY OF THE INVENTION The invention is a method and apparatus for minimizing the amplitude of mechanical vibrations of a mechanical apparatus that includes a linear motor coupled to This and to activate an oscillation mass of a machine activated in oscillation at an activation frequency. The coupled motor and the activated machine have one or more springs that apply a force on the compound oscillation mass to form a resonant main system having a resonant frequency of the main oscillation system. An activation frequency range over which the activated machine operates at an acceptable operating efficiency is determined and stored. A parameter of the operation of the mechanical device is detected and the linear motor is activated in response to the detected parameter in an activation frequency that moves from the resonant frequency of the main oscillation system, is within the efficiency activation frequency range acceptable operation and reduces or minimizes the amplitude of the mechanical vibration of the mechanical device under existing operating conditions.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a block diagram illustrating an example of one embodiment of the invention. Figure 2 is a block diagram illustrating a second example of an embodiment of the invention. Figure 3 is a graphical scheme in the frequency domain of resonant peak points and illustrates the operation of the invention. Figure 4 is a block diagram showing an example of a control circuit representing the invention and using a temperature sensor. The Figure 5 is a block diagram showing an example of a control circuit representing the invention and using a vibration amplitude sensor. Figure 6 is a block diagram showing an example of a control circuit representing the invention and using a variable frequency generator. Figure 7 is a block diagram showing an example of a control circuit representing the invention and having a temperature sensor. In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be used for clarity purposes. However, it is not intended that the invention be limited to specific terms selected and it is understood that each specific term includes all technical equivalents that operate in a similar manner to fulfill a similar purpose.

DETAILED DESCRIPTION OF THE INVENTION The invention makes use of the observation that, for a mechanical apparatus that includes a main oscillation or vibration machine coupled to a secondary vibration system, which may include a vibration compensator, there are three frequencies that are important. There are the resonant (or natural) frequencies of the main vibration machine, the resonant (or natural) frequency of the secondary vibration system and the frequency of operation of the main machine. The frequency of operation of the main machine is also the frequency of operation of the vibration compensator and of any other secondary vibration system coupled to the main machine. If a frequency versus vibration amplitude plot is made for any resonant system, the traced amplitudes form a resonant peak centered on a resonant frequency. These maximum points can rise and fall in a margin extending gradually, broadly abruptly, abruptly. The more abrupt the maximum point, the higher the quality factor "Q" of the resonant system, as known to a person skilled in the art. The invention also makes use of the observation that those main machines having a primary, free-oscillating, linear motor that drive an activated, free-swing, linear and operating machine Efficiently at or near its composite resonant frequency, they still ordinarily have a band of activated frequencies on which they can operate at an acceptable efficiency. They do not just operate at their resonant frequency. In part this is due to a typical main machine, such as a linear motor that activates a Stirling cooler, ordinarily exhibits a maximum point of low Q resonance. Although this is useful, the activation frequency range over which the activated machine operates at acceptable operating efficiency is determined not only by the Q of the mechanically resonant oscillation components of the main machine, but also depends on other characteristics of operation and design of the main machine. However, a designer of any particular machine can determine an acceptable range of activation frequency by applying engineering principles common to the design of a particular main machine and its application. Figure 1 diagrammatically illustrates a mechanical apparatus 10 having a main machine 12, consisting of an electromagnetic linear motor 14 which activates an oscillating Stirling cooler 16, an engine control circuit 18 having a data storage 20 and controls the operation of a linear motor 14. The main machine 10 may also include secondary vibration systems 24, such as a vibration compensator 26 and parasitic resonant systems 28. All illustrated components are mechanically coupled to form the mechanical apparatus 10. For example, they can be physically connected together in the same housing or in the same frame or they can be joined by intermediate physical structures that can transmit vibrations. The control system further has a temperature sensor 22 which senses the temperature of the vibration systems 24, which can be detected in the crankcase, and inputs the temperature data to the motor control 18. The temperature sensor can detect the temperature of the spring of the vibration compensator since it is the main component for which the temperature changes affect more directly the resonant frequency of the vibration compensator. Alternatively, the temperature of an environment or a component in the thermal connection with the spring can be detected to approximate the temperature of the spring. The motor control 18 may be of a conventional type which is typically a microprocessor based on a computer system or a microcontroller or a digital signal processor and may also include additional sensors. Although the preferred control circuit is a microprocessor controller, there are many alternative means to provide the circuit functions of control. As is known to those skilled in the art, there is a variety of non-commercially available microprocessor-based controllers that can also provide controller functions and are therefore equivalent and can be replaced by the microprocessor controller. The detection functions can be carried out by a separate circuit set or can be provided by integrating a controller. Suitable controllers may include equivalent analog and digital circuits available in the market. Examples of controllers that can be used for the control circuit of the invention include microprocessors, microcontrollers, programmable gate arrays, digital signal processors, programmable analog field matrices and logic gate arrays. The circuits can be elementary digital logic circuits and can be constructed of discrete components such as diodes and transistors. Therefore, the term "controller" is used to generically refer to any of the combinations of analog signal and digital logic processing circuits that are available or known and that can be constructed, programmed or otherwise configured to perform the functions logic of the control circuit as described above.

As broadly shown in the prior art, the linear motor has a set of oscillation of magnets that are located to oscillate within a fixed armature winding. The magnets are driven in oscillation by an alternating magnetic field generated by an alternating current applied to the armature winding. A support for the magnets is connected to the piston of the Stirling cooler 16 and activates it in oscillation. This oscillation causes the Stirling cooler to pump thermal energy from one area of the cooler to another where it is rejected. As is also known in the art, Stirling devices are also more generally known as thermal pumps due to their thermal pumping capacity described above. Stirling heat pumps can be used to heat objects from rejected heat or to cool objects by accepting heat in their cooled area and rejecting it within an environment. Therefore, the latter are often defined as chillers and include chillers that cool to cryogenic temperatures. The details of the linear motor and the activated machine, such as a thermal Stirling pump, the compressor or the fluid pump, are not illustrated because they are not the invention and are illustrated in numerous examples in the prior art. The principles of this circuit can also be applied to other primary engines of free oscillation, linear and activated loads such as linear compressors and free piston Stirling motors that use vibration compensators. Figure 2 illustrates an example of an alternative embodiment of the invention. The mechanical apparatus 30 has a main machine 32 comprising a linear motor 34 which activates an oscillating Stirling cooler 36, and a motor control 38 for controlling the linear motor 34, including controlling its activation frequency. The motor control has a vibration amplitude sensor 40, such as an accelerometer, for detecting and entering the motor control 38 a signal representing the amplitude of the vibrations of the mechanical apparatus 30. All of these devices are physically coupled as described in relation to Figure 1. The embodiment of Figure 2 can also be coupled to one or more secondary vibration systems, such as a vibration compensator 46 and parasitic vibration systems 48. Figure 3 illustrates the principles in which the invention operates. It refers to frequency values and curves that are representative and typical but the invention is not limited to those values and curves. For example, it is common for a main oscillating machine to be designed as a resonant and operating at 60 Hz. However, many other operating frequencies are practical, such as 50 Hz, 120 Hz or 400 Hz. The main machines of the type described are typically designed as resonant at a natural frequency of vibration or resonant frequency f0 corresponding to f in equation 1 above. The resonant peak point M illustrates a typical resonant peak for the mechanical vibrations of a main machine having a resonant frequency of 60 Hz. Its resonant peak is relatively large relative to its resonant frequency, thus exhibiting a relatively low Q characteristic. The resonant SI and S2 peak points illustrate a typical resonant peak for a secondary vibration system. These are relatively abrupt and abrupt, thus exhibiting a relatively high Q characteristic. Although the average energy points (70.7% amplitude) are a well-known measure of the width of a resonant peak, this measure applies only to mechanically resonant aspects of the system. Other operating characteristics of the main machine, such as its cooling efficiency or coefficient of performance, determine the operating efficiency of the activated machine. Therefore, the range of the activation frequency in which the activated machine operates with acceptable efficiency can, and is usually, different from the width of the resonant maximum point of the oscillating system mechanically. However, this acceptable activation frequency range may be, and is commonly determined by the designer. In Figure 3, an example of a margin R of acceptable activation frequency between 58 Hz and 62 Hz is illustrated, although it will be different for the different main machines. The resonant SI and S2 peak points can be used, in explaining the operation of the invention, to represent a secondary vibration system which is a vibration compensator or a secondary vibration system which is a parasitic vibration system. Each one is directed in sequence. If the secondary vibration system is a vibration compensator and the main machine is operating under its design or nominal conditions, it will be operating with the maximum point M representing the main machine and the maximum point SI representing the vibration compensator. Under that condition, the activated machine can be activated at a nominal resonant frequency of the main machine, 60 Hz in the example, since that frequency coincides with the resonant frequency of the vibration compensator. However, if the operating conditions, such as temperature, change sufficiently so that the physical parameters of the main machine or the secondary vibration system cause a change in the resonant frequency of one or both, that change will appear in the graph of Figure 3 as one or both of the maximum points that move horizontally with respect to the other. For example, the maximum point SI can be moved to the position of the maximum point S2, although it could move in any direction and different distances. The shift from the maximum point SI to the position of the maximum point S2 causes the vibration compensator to become much less effective if the main machine continues to activate on the resonant frequency of the main machine. However, if the frequency of activation of the main machine changed to be closer to the center of the maximum point S2, the vibration compensator would become more effective at that frequency, 62 Hz in the example, as long as the changed operating conditions remain . If the maximum point of the vibration compensator changes to a center at 61 Hz or 62 Hz, the activation frequency would move to 61 Hz or 62 Hz respectively. Thus, in the invention, the motor control system 18 or 38 activates the linear motor at an activating frequency that is shifted from the resonant frequency of the main system or machine that is closer to or on the displaced resonant frequency of the motor. vibration compensator but that is within the Activation frequency range of acceptable operating efficiency of the main system. Therefore, an aspect of the invention is that, in response to changes in operating conditions that cause the divergence of the center frequency of the resonant peak points of the main machine and a vibration compensator, the frequency of activation of the Linear motor moves closer to the altered center frequency of the vibration compensator. Although the activation frequency can be changed to approximate the changed S2 resonant peak frequency, it can not be moved beyond the limits of the acceptable activation frequency range R since this would cause unacceptable deterioration of the main machine operation . If the secondary vibration system is a parasitic vibration system, it is to be expected that its resonant peak remains far enough away from the central frequency f0 of the main machine that it never becomes a factor in the vibration. However, other equipment mounted on the mechanical apparatus 10 or 30 may introduce one or more parasitic vibration systems having a maximum resonant point unexpectedly close to the central frequency f0 or moving close to it as a result of changes in conditions of operation. The maximum points YES and S2 may represent the maximum resonant points of parasitic, secondary vibration systems. If the maximum point SI is the maximum point of the parasitic vibration system, Figure 3 illustrates that the parasitic, secondary vibration system can be substantially reduced by changing the activation frequency on one side of the center frequency of the SI maximum point but retaining it inside. of the R. margin. Consequently, the activation frequency would be optimally done at 58 Hz or 62 Hz. If the maximum point S2 is the maximum point of a parasitic vibration system, the parasitic vibration system would be minimized by moving the activation frequency to 58 Hz in the example, which is even possible from the center frequency of the maximum point S2 , but not beyond the R margin. There are multiple ways to design and build a control system to vary the frequency of primary motor activation, free oscillation, linear according to the above principles and six examples will be described. All include detecting a parameter of the operation of a mechanical device, such as the amplitude of vibration of the mechanical device or a temperature of a component part of the mechanical device. The detected parameter can be detected by a sensor provided to practice the invention or it can be a sensor that is part of another control system.

Figure 2 is the first of six examples. The vibration amplitude sensor 40 detects the amplitude of the vibration of the mechanical device. In general, it can be placed on any part of the component of the mechanical device that is mechanically coupled together, since vibrations from any part are commonly transmitted to the other parts of the component. The motor control 38 activates the linear motor 34 at each of the various representative frequencies distributed within the activation frequency range of acceptable operating efficiency. Each frequency is stored together with the amplitude of the resulting, detected vibrations. This is carried out initially, periodically after the start, in response to a vibration amplitude detected on a selected level and / or in response to other conditions or algorithms. The software or logic circuitry of the motor control 38 then selects the lower vibration amplitude and activates the linear motor at a frequency associated with the lower vibration amplitude. Therefore, the vibrations are reduced or minimized for the operating conditions existing at the time when the procedure is carried out. The repetitions of the procedure allow the control system to respond to the changed operating conditions.

More specifically, the motor control circuit 38 finds the lower vibration frequency when the linear motor is activated in a plurality of frequencies within an acceptable range R by any of the various techniques referred to herein as the distortion or sweep of the motor. the frequency through the frequency range R. The most common way to sweep the frequency is to progressively vary the frequency from one side of the R margin to the other, either continuously or in incremented steps. However, this sweep may alternatively be executed randomly or non-sequentially and may be carried out at selected spaced intervals. Figure 1 illustrates a second example of the invention. The temperature sensor 22 detects the temperature of the vibration compensator 26, or its surroundings, and inputs the temperature data to the motor control 18. As with all embodiments of the invention, the activation frequency range of the acceptable operating efficiency is determined and stored in response to the test of at least one mechanical device. The test is commonly carried out in a laboratory installation but can be based on engineering design specifications. This experimentally determined operating frequency range of efficiency acceptable operation is then stored in production replicas of the mechanical apparatus. At least one mechanical thermal pumping apparatus is also tested, commonly in a laboratory environment, by operating at a plurality of different operating temperatures and, for each of the operating temperatures, the activation frequency is swept within a acceptable activation frequency range. The resulting activation frequency in the smallest vibration amplitude of the mechanical device is stored together with each operating temperature. As a result, for each operating temperature that is detected, there is a stored activation frequency that provides the minimum vibration. These operating temperatures and their associated activated frequencies are stored as a look-up table in a memory device 20 connected in the frequency control system of production replicas of the tested mechanical apparatus. Alternatively, the search table may store a spring constant for the vibration compensator spring together with the measured temperature and an algorithm used to convert the spring constant to an operating frequency. As another alternative, an equation can be carried out instead of a search table using well-known mathematical techniques, such as As a series of polynomials, to approximate a scheme of the search table and thus relates the constant of the spring of the vibration absorber or the operating frequency with the temperature detected with the computerized result by the motor control microprocessor. During the operation of the production replicas, the corresponding operating temperature of the replicas is detected and the associated activation frequency or the spring constant is extracted from the data storage 20 or, alternatively, computerized by the equation. The linear motor is then activated at a computed or stored activation frequency associated with the detected temperature. This process is repeated during the operation of the production machines so that the mechanical apparatus is always driven at the activation frequency that provides the smallest vibration amplitude for the most recently detected temperature. For the mechanical apparatus having the secondary systems of parasitic vibration and the vibration compensator, there will be maximum resonant points that are represented in a graph similar to Figure 3. However, the method and the methods of the invention remain the same. Figure 4 illustrates a third example of a embodiment of the invention. It shows a mechanical apparatus of the prior art and a control system to which the components have been added to carry out the invention. The prior art system illustrated has a main machine consisting of an electric linear motor 50 mechanically linked to the masses 52 of internal driving movement thereof and a load activated and mechanically connected to the secondary vibration systems 54. A sensor 56 detects a parameter of the operation operation of the main machine, such as the top dead center (TDC) or piston position of one of the movement masses 52 and also the motor voltage and current are detected. These signals are applied to a signal conditioner 58 and applied as a feedback signal to the summing junction 60 of a feedback control system, which are applied in the software of a microcontroller or a digital signal processor 62. A reference value is also applied to the summing joint 60 to provide an error signal that is applied to a transfer function and to develop a control signal according to the principles of the well-known feedback control system. To control the linear motor 50, the control signal is applied to a generator circuit 64 of the load cycle inverted variable frequency that generates a square wave for which the load cycle and the frequency of the square wave can vary in a controllable way. The charging cycle is controlled in the form of the prior art by the control signal. The output of the generator circuit 64 is applied to an inverted output stage 66 that converts the square wave into pulses of opposite direction to activate the linear motor 50, the pulses having a pulse width that correspond to the load cycle of the square wave . A variety of such circuits are known in the prior art and the invention is not limited to any drive circuit having these general characteristics. To apply the present invention, a temperature sensor 68 is mounted near the vibration compensator 54A and applies its output signal to the microcontroller 62 to store the temperature data for use in a search table 70 or a corresponding equation for the use when determining the frequency of operation as described in conjunction with Figure 1. If the search table or equation provides values that correspond to the spring constant of the vibration compensator for each detected temperature, that output is converted by an algorithm 72 of Frequency adjustment to determine the frequency of operation. If the search table or the Equation directly provides frequency, algorithm 72 can be omitted. Figure 5 illustrates a fourth example of an embodiment of the invention. It shows the same mechanical apparatus of the prior art and the control circuit as illustrated in Figure 4 to which the components have been added to carry out the invention. To carry out the invention, a vibration sensor 80 is connected to provide an amplitude of vibration input to the microcontroller 82. The microcontroller 82, under the control of the software module 84, scans, oscillates or otherwise varies the activation frequency of operation within the limits of the acceptable range of operating frequencies as described above and performs the storage of the smallest amplitude of vibration within that range. The microcontroller 82 then selects and operates the linear motor 86 at a stored operating frequency that is associated with the smallest amplitude of vibration. It also repeats this process at selected intervals or under selected conditions, such as those described above, so that the operating conditions can change, the electric linear motor 86 is always activated at a lower amplitude frequency of vibration. Figures 6 and 7 are diagrams illustrating the fifth and sixth examples of the embodiments of the invention. Both include the identical device of the prior art to which the set of circuits carrying out the invention is added. Therefore, the portion of the prior art, common to the figures, will be described first. Figures 6 and 7 show a main machine which is a 100 piston-free Stirling engine which activates an electric linear alternator 102 to generate electric power from a thermal source input. They may be of a design known in the prior art and are typically mounted in the same housing. The Stirling motor oscillation motor piston is mechanically linked to the oscillating component of the alternator, usually a series of permanent magnets supported on a carrier that oscillates within an armature winding or coil mounted within the common housing. The mass 104 composed of these oscillation structures is mechanically linked to a vibration compensator 106 and to any parasitic vibration system 108 through the reaction of the cylinders and the crankcase of the Stirling and alternator engine. These reaction forces are transmitted to the cylinder and the crankcase through the usual mechanical springs, by operating the gas inside the Stirling motor and the electromagnetic coupling from the magnets to the armature coil. The output of the alternator 102 is connected through of a conventional tuning capacitor 109, used for correction of the energy factor, to supply power to a useful load 110. The frequency of the Stirling 100 engine is controlled using a principle known in the prior art to connect a driven alternator of the Stirling engine to a grid power to supply power to the grid. Stirling motor oscillations will synchronize with the AC power oscillations of the grid power if the Stirling engine driven alternator is designed to resonate near the frequency of the grid power. The principle applied is that the oscillations of a driven alternator of the Stirling engine, when connected to an external AC power source, will be synchronized with the voltage oscillations of the AC power source if the AC power source has a lower internal impedance than the alternator and if there are only small variations in frequency. The frequency variations applicable to the invention and described above are those small variations. A variable frequency, a power source 111 of varying amplitude is used as a motor output frequency controller and its AC output terminals are connected to the alternator 102. The power sources they are commercially available and therefore not described. The output of the variable frequency generator 118 of the microcontroller 114 is connected to the control input terminal 112 of the variable AC power source 111 which is the input that controls the frequency of the variable AC power source 111. The output of the variable frequency generator 118 controls the power source 111 of AC. Accordingly, within the small frequency variations used in the present invention, the operating frequency of the driven linear alternator 102 of the Stirling engine tracks the frequency of the variable AC power source 111 and is therefore controlled by the microcontroller 114. The implementation of the invention illustrated in Figure 6 operates in a manner similar to the embodiment illustrated in Figure 5. The controller 114 is programmed to perform the arithmetic and logic operations to computerize the operating frequency of the main machine that minimizes the amplitude of vibration. A vibration sensor 116, such as an accelerometer, has an output connected to an input of the controller 114 to provide a signal representing the amplitude of the detected vibration of the prior art, the main machine illustrated in Figure 6. However , instead of entering a nominal operating frequency such as a command input to a motor frequency controller, a variable frequency generator 118 is interposed between the input of the nominal operation frequency command and the input to the variable AC source 111. This allows the controller 114 to shift the command operating frequency from the nominal operating frequency to minimize vibration. The controller 114, under the control of the software, scans, scans, or otherwise varies the frequency of activation of operation within the limits of the acceptable range of operating frequencies and implements the storage of the smallest amplitude of vibration within that range. . The controller 114 then selects and operates the Stirling engine 100 at the stored operating frequency that is associated with the smallest amplitude of vibration. It also repeats that process at selected intervals or under selected conditions, such as those described above, so that, while the operating conditions may change, the free piston 100 Stirling engine always activates at a lower amplitude frequency of vibration within the limits of the acceptable range of operating frequencies. The implementation of the invention illustrated in Figure 7 operates in a manner similar to the embodiment illustrated in Figure 2 and applies the same operating principles to control the frequency of operation of the engine 100.

Free piston stirling as described in conjunction with the embodiment of Figure 6. The output of a temperature sensor 120 is connected to an input of a controller 122 to provide a signal representing the temperature of the vibration compensator 106. The controller 122 then operates the Stirling engine 100 over the frequency range of the acceptable operation and stores each temperature along with an operating frequency to provide a search table 124 for the same process as described above along with Figures 2 and 4. Although certain preferred embodiments of the present invention have been described in detail, it is to be understood that various modifications may be made without departing from the spirit of the invention or the scope of the following claims.

Claims

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. CLAIMS 1. A method for minimizing the amplitude of mechanical vibrations of a mechanical apparatus including a primary, free-oscillating, linear motor coupled to it and to activate an oscillation mass of a machine activated in an oscillation at an activation frequency, The coupled primary motor and the activated machine have a spring that applies a force on the oscillation mass to form a resonant main system having a resonant frequency of the main oscillation system, the method characterized in that it comprises: (a) determining and storing a activation frequency range over which the activated machine operates at an acceptable operating efficiency; (b) detecting an operation parameter of the mechanical device; and (c) activating the primary motor in response to the detected parameter at an activation frequency which (i) is shifted from the resonant frequency of the main oscillation system; (ii) is within the activation frequency range of acceptable operating efficiency; and (iii) reduces or minimizes the amplitude of the mechanical vibration of the mechanical device under existing operating conditions.
2. The method of compliance with the claim 1, characterized in that the detection step comprises detecting the vibration amplitude of the mechanical apparatus and wherein the method further comprises: (a) sweeping the activation frequency over a frequency range that includes the resonant frequency of the main oscillation system; (b) storing the detected amplitude of vibration together with a plurality of activated sweep frequencies; and wherein the primary motor is activated at an activation frequency which is a stored activation frequency associated with the smallest amplitude, stored, detected.
3. The method of compliance with the claim 2, characterized in that the method is repeated periodically.
4. The method according to claim 1, for controlling a mechanical device in which the activated machine is a thermal pumping apparatus, Stirling, of free piston, characterized in that: (a) the activation frequency range is determined and stored in response to the test of at least one component of the mechanical apparatus; (b) at least one thermal pump apparatus of the mechanical apparatus is operated during a test at a plurality of operating temperatures, for each operating temperature the activation frequency varies within an acceptable activation frequency range and the frequency of activation that results in the smallest amplitude of vibration of the mechanical device is stored along with the operating temperature; (c) the operating temperatures and the associated activated frequencies are stored as a look-up table in a memory device connected in a frequency control system of replicas of the tested mechanical apparatus; (d) the detection step comprises detecting the operating temperature of the replicas of the tested mechanical apparatus, and (e) the primary motor is activated at a stored activation frequency associated with the sensed temperature.
5. A computer or logic circuit control system to minimize the amplitude of vibrations mechanics of a mechanical apparatus include a main machine having a free, linear oscillating motor that activates an oscillating activated machine, the main machine includes a mass and springs which apply a force on the mass to provide a resonant mechanical oscillator having a resonant frequency near which the main machine is designed to be operatively activated, the control system characterized in that it comprises: (a) a sensor for detecting a parameter of operation of the machine; (b) a data storage for storing an activation frequency range over which the activated machine operates at an acceptable operating efficiency; and (c) a microcontroller connected to receive inputs from the sensor and data storage to control the primary and programmed motor to activate the primary motor in response to the detected parameter at an activation frequency that is shifted from the resonant frequency of the machine oscillation main, is within the range of stored activation frequency of acceptable operating efficiency and minimizes the amplitude of the mechanical vibration of the mechanical device under the existing operating conditions.
6. The control system in accordance with the claim 5, characterized in that the sensor detects the amplitude of vibrations of the mechanical device.
The control system according to claim 6, characterized in that the sensor is an accelerometer.
8. The control system according to claim 5, characterized in that the sensor is a temperature sensor. The control system according to claim 8, characterized in that the sensor is connected to detect the temperature of a spring of a vibration compensator. The control system according to claim 5, characterized in that the primary motor is an electric, linear motor. The control system according to claim 5, characterized in that the primary motor is a free piston Stirling motor. The control system according to claim 5, characterized in that the activated machine is a Stirling free piston cooler.