Contraction engine

Abstract

The present invention is an electric motor capable of contracting itself to transmit its mechanical force in the form of traction to another attached object. This type of motor behaves similarly to a muscle and can be manufactured to its exact size and shape to replace it, thus enabling mechanical limb prostheses equipped with it to restore to the user almost all the motor skills of their lost limb, unlike other types of electric motors which only restore a portion of them. This motor consists of an assembly of contraction units, each comprising a solenoid attached to the outer fibrous sheath by central fibers, and a permanent magnet facing it, also attached in the same way.When an electric current passes through the solenoid, it becomes magnetic. The two attract each other, and their attractive force is transmitted via the fibers to the coating, causing it to contract. This force can then be transmitted to another object attached to the coating. A special damping system is also present. Everything relies on a clever interplay of mechanical tension coupled with a driving force source derived from the properties of electromagnetism to successfully reproduce the subtleties of muscle movement. This device is useful in improving the capabilities of active limb prostheses, in robotics for enhancing the capabilities of android robots, and is also likely to find applications in other fields.

Description

Title of the invention: Contraction motor

[0001] The present invention relates to an electric motor capable of contracting on itself, by biomimicry of the contraction of living muscle tissue, in order to substitute the latter in its function, in the context of the use of bionic limb prostheses.

[0002] To date, all active mechanical limb prostheses are equipped with so-called "direct current" electric motors, a type of motor that converts electrical energy into mechanical energy in the form of rotation. Mechanical energy is delivered in this form by virtue of their operating principle, and if it is desired that they deliver their force linearly or in another way, additional equipment is required to modify it. These installations are cumbersome compared to an electric motor capable of delivering mechanical force directly in the desired way.

[0003] Furthermore, current prostheses equipped with these direct current motors do not allow for the full recovery of fluidity, precision, and motor skills of living limbs. Some come close, but by using complex additional methods, specific to each constraint encountered, which only makes them much more expensive and less accessible. Currently, there still remains a gap between the capabilities provided by the muscles of living limbs and the capabilities offered by mechanical prostheses of these limbs.

[0004] The present invention, this new type of electric motor, is capable of delivering its mechanical force directly in the form of "self-contraction" without the need for additional converters. This means that its function is the same as that of living muscles, which contract with varying degrees of intensity to control limb movements. Hence the concept of biomimicry. Thus, with these motors equivalent to striated skeletal muscles, the prostheses equipped with them will allow users to regain all the fluidity, precision, strength and control of the movements of their original limb. Important note: Smooth muscles, i.e. the heart and small intestine which are both muscles and organs, cannot be replaced in their function by this motor.

[0005] First of all, let us observe the structure of a striated skeletal muscle. A muscle contains several fibers, each made up of numerous sarcomeres assembled in a chain. Sarcomeres have the ability to contract by shortening themselves when they receive nerve messages from the brain (from the will). The shortening of all sarcomeres in a chain leads to the shortening of the entire muscle structure. Muscle shortening leads to the expression of a force on the tendons, which in turn pull on the bones to which they are attached. The operating principle of a muscle is therefore based entirely on its ability to contract under nerve command.

[0006] The biomimicry of the motor, on the other hand, is based on the fact that it is composed of the assembly of numerous subunits capable of contracting on itself when an electric current is delivered to them, like muscles composed of their entire sarcomere. These contraction units are therefore the mechanical equivalent of sarcomeres; they allow the motor to mimic the motor skill of muscles, and can be assembled in such a way as to give the overall structure, the motor, any shape and size, which means that one can give this motor the shape and size of any striated skeletal muscle that one wishes to imitate, simply by assembling the contraction units in such a way as to obtain this desired shape.

[0007] As for their operation, the units exploit the force of magnetic attraction to contract. A magnetic attraction occurs between two magnetic components, in this case a permanent magnet and an electromagnet (a component that can generate a powerful magnetic field when an electric current passes through it, and therefore ceases to be magnetic when the current is interrupted). The fact that one of the two components is an electromagnet allows direct control over the magnetic attraction and thus over the contraction of the unit, acting as an on / off switch for the magnetic attraction, which ceases as soon as one of the two components is no longer magnetic. The contraction is therefore directly dependent on whether or not electricity arrives in the electromagnet, and thus, controlling the delivery of the electric current means controlling the contraction. A central fiber system connects each component at the ends of the structure on both sides so that they can be suspended "in a vacuum" to prevent any friction with the wall in order to maximize the force they exert on each other, and to be able to transmit this force efficiently because the transmission of their mechanical force plays a key role in the operation of the invention. The magnetic attraction between the two components manifests as a mechanical force because it acts on their mass and their movement. This force can then be transmitted through the central fibers to the two ends of the structure's fibrous coating. The structure then experiences this internal attractive force, causing the two magnets to move closer together. Each component thus pulls one end of the structure in its direction via the central fibers, resulting in the unit contracting upon itself. Once transmitted into the unit's structure, this force can be propagated to an external body or combined with other forces before being transmitted. In the context of the motor consisting of several contraction units, when all the units contract each transmits its force into its fibrous coating, and since all the fibrous coatings are linked together to form the coating of the motor, we can add the contraction force of all these units and then propagate it to another body that is attached to the motor.

[0008] Once at rest, that is to say when the muscle no longer receives any nerve messages from the brain (from the will), the muscles will tend to relax. However, even at rest, the muscle possesses muscle tone. It is a slight, permanent, and involuntary contraction that aims to prevent excessive relaxation of the muscle. This state of muscle tone is the result of the myotatic reflex, an automatic muscle contraction mechanism. It also functions independently of the will, continuously and instantaneously, and therefore maintains a state of muscle tone. In concrete terms, the muscle has a minimum tension threshold value (or maximum relaxation threshold), which, when crossed, triggers the myotatic reflex in a significant way so that it brings the muscle back to a tension level above the threshold. The level of contraction / relaxation is measured by the body through neuromuscular spindles, these sensory organs which are fixedly wrapped around the muscle fibers so that they undergo the same levels of contraction / relaxation as the fibers. They are also capable of sending nerve signals in a quantity proportional to the intensity of the relaxation they (and the muscle) undergo. When they reach their relaxation threshold, these neuromuscular spindles then send nerve signals in sufficient quantity to trigger the myotatic reflex response, which will be proportional to the quantity of nerve signals received. Thanks to this quantification of the intensity of relaxation, the myotatic reflex is able to measure and determine the deviation from its threshold value, and to respond appropriately to each intensity of relaxation it encounters. In simple terms, the myotatic reflex is an automatic and proportionate contraction mechanism, muscle tone is a state of slight permanent contraction of the muscle. Muscle tone is a consequence of the myotatic reflex.

[0009] In the engine, the state of muscle tone and the myotatic reflex capacity are reproduced by specific components, namely spring dampers which, by their assembly, allow the shortening of the springs to be attributed to relaxation rather than contraction. This causes the springs to resist in order to maintain their initial shape and avoid flattening, which would counteract the relaxation of the contracting unit. The springs are also capable of reacting proportionally to the forces to which they are subjected. This mechanism is passive and requires no electrical power, allowing it to operate continuously without restrictions. It plays a major role in the biomimetic capability of this invention, contributing to the smooth and controlled movements of the prostheses equipped with it.

[0010] To mimic an actively controlled myotatic reflex, i.e., one powered by electricity, force sensors can be placed to continuously measure the internal voltage of the motor and send this value to an electronic motor control system. The motor then compares this value with a threshold value programmed into its system. If the voltage value is detected as being below the threshold, the system will activate the motor's contraction in proportion to the intensity of the contraction and return it to an acceptable voltage level. This mechanism remains optional; it would complement the damping system, and its presence or absence does not affect the proper functioning of the invention. Regarding the fibrous coating: The precise choice of weave and the nature of the material(s) constituting the covering is very important: - A fiber that is too resistant cannot properly imitate the properties of a muscle. - A fiber that is too malleable creates a loss of energy which is absorbed by its deformation. It reduces the maximum potential that the motor can reach. The choice of materials used in the coating will have to vary depending on the engines, so as not to hinder their full potential of use. For example, the coating on a motor designed to replace the quadriceps (a thigh muscle and one of the most powerful muscles in the human body) to best suit and optimize its function will not have exactly the same coating as the coating on a motor designed to replace the palmaris brevis, a small muscle in the hand. Therefore, even if many materials are suitable and do not impair the proper functioning of the invention, they are not necessarily the most optimal. It is best not to mention specific material choices here; experimental tests will be much better at determining the choice of materials for each engine model based on their: - Maximum power, size, weight, and expectations for the engine as a whole. - Maximum power and size of the contraction units that compose it.

[0011] The attached drawings illustrate the invention: [Fig.l] represents in cross-section the contraction unit with the central fiber of the permanent magnet highlighted. [Fig.2] shows in cross-section the contraction unit with the central fiber of the solenoid highlighted. [Fig.3] represents the plastic support of the solenoid. [Fig.4] represents in cross-section the contraction unit at rest. [Fig.5] represents in cross-section the unit of contraction contracted upon itself. [Fig.6] represents the three-dimensional structure of a contraction unit. [Fig.7] shows a cross-section of a shock absorber module. [Fig.8] represents the platform of the shock absorber module before being linked to the central fiber. [Fig. 9] shows the two faces of the platform after it is connected to the central fiber. [Fig. 10] shows a cross-section of a motor made up of an assembly of several contraction units with an example of a power line highlighted. [Fig.1 1] represents in cross-section the motor consisting of the assembly of several contraction units attached to the rigid fibers.

[0012] With reference to these drawings, the contraction unit (1) comprises a copper solenoid (2) fitted into a special plastic support (6) and a cylindrical permanent magnet (3) which are each attached by rigid central fibers (4) to the two opposite ends of the structure (5), on one side directly to the top, on the other, to the center of the faces just to the side of this top by several attachment points, one for each face. There is a slight offset of the central fiber (4) of the magnet (3) relative to that of the solenoid (2) so that the two do not overlap over part of their length. For this purpose, the orifices of the magnet (3) intended to make a link are placed so that the central fiber (4) which attaches it is offset from its center without this influencing its movements. Furthermore, it is the plastic support (6) which is attached to the walls (5) by the central fibers (4), the solenoid (2) is connected to an electrical power source by wires. This plastic support (6) prevents any deformation of the solenoid (2) under stress, because copper is a malleable material. An opening, or several when necessary, are present in the unit's casing (5) to allow the electrical supply wires (9) to reach the solenoid (2).

[0013] In its initial position, the magnet (3) is located opposite the solenoid (2), close but not touching it, aligned with its center axis. It must be as large as possible while remaining small enough to pass through the solenoid (2). The gap between the solenoid (2) and the magnet (3), once the magnet (3) has passed through the solenoid (2), must not exceed a few millimeters so that the magnetic attraction remains sufficiently strong. (The magnetic pole of the magnet (3) facing the solenoid (2) must be the opposite pole of charge to that which the solenoid (2) will generate when the electric current passes through it, so that the two opposite poles attract each other and not that two identical poles repel each other.) Thus, in the presence of an electric current, the magnet (3) and the solenoid (2) are attracted to each other, tending to move closer together and thereby pulling on the central fibers (4) that connect them to the two ends of the unit (1). This pulling force is then propagated by these central fibers (4) to the two ends of the unit (1), which are thus pulled towards each other, leading to the shortening of the entire structure (1). The fibrous covering (5) of the unit (1) serves both as a "casing" and as a means of transmitting and utilizing the mechanical force. This is how we have a structure capable of converting electrical energy into mechanical energy directly in the form of contraction.

[0014] Regarding the damping system, several damping modules (10) are present in a unit (1): They are always located intermediately in the central fibers (4), that of the solenoid (2) and that of the magnet (3), between them and the wall (5). They are therefore attached to the central fibers (4) of the two parts. They consist of springs (15) around rods (14) encapsulated in a housing (11). The rods (14) and the walls of the housing are rigid and cannot deform. This housing (11) also contains a movable platform (12) capable of mounting and descending via a vertical rail system (13) on the walls of the enclosure. A rail (13) is installed on each of the four vertical walls of the enclosure (11). This platform (12), being attached by the rail system (13), has no direct contact with the walls in order to avoid any friction. This platform (12) is connected at its center to the central fibers (4) leading to the magnet (3) or the solenoid (2), with holes (16) provided for connection, and also has other holes (17) through which the rods (14) pass on the sides of this center. In short, the platform (12) rests solely on the springs (15) wound around the rods (14). The rods (14) are rigid and cannot move because they are fixed to the top and bottom walls of the housing and serve as supports for the springs (15), allowing them to wind around and maintain their position within the housing (H). Similarly, an opening (18) in the casing (11) is provided to allow the central fibers (4) to pass through it until they connect with the platform (12). When the contraction unit (1), and therefore the central fibers (4), relax, they will stretch and pull the platform (12), which will move downwards within the casing (11), pressing down on the springs (15). Thus, the springs (15) will resist the descent of the platform (12) by absorbing the force exerted by their deformation, but also by exerting a force opposite to that exerted on them, because the more they are compressed, the more they will try to return to their original dimensions, thus offering greater resistance. They will thus allow the mechanical tension of the central fibers (4) and therefore of the contraction unit (1) to return to normal, and have a reaction proportionate to the forces they undergo.

[0015] The springs (15) must be able to push the platform (12) to its upper end, that is, to the top of the housing (11), when they are in their normal state, i.e., when they are not subjected to any force. However, when assembled and fitted into these housings (11), the normal tension of the unit (1) must maintain the platform (12) not at the very top of the housing (11), but around the middle in order to allow a margin of expansion and contraction for the unit (1). This contraction margin allows the springs (15) to retension the secondary portion of the central fibers (4) that are relaxed during the contraction of the unit (1). The shorter the central fibers (4) are than the fibers of the unit's (1) cladding but forcibly assembled, the greater the minimum tension of the central fiber (4) will be, because the outer walls (5) will have been forced to deform to be assembled onto the shorter central fiber (4) and will struggle to return to their normal shape. It is this minimum tension that must be set to keep the platform (12) centered and allow for slack in both directions. This means indirectly that in this so-called "normal" state with the platform (12) in the middle, the springs (15) are actually under stress, since the platform (12) is not pushed to the top of the housing (11), they are therefore not at rest.

[0016] The walls (5) of the contraction units (1), and by extension of all the motor coatings (19), are made of fibers in order to obtain a material with the properties of a rope, that is to say, a fiber that is both strong and flexible, which efficiently propagates the applied forces, especially tensile and pushing forces. The central fibers (4) are, in a way, an extension of the coating fibers (5). Here is a non-exhaustive, non-limiting list of materials that can compose the coating (5) and the central fibers (4): polyester, aramid, carbon fibers, polyolefins. The nature of the composition itself is not of real importance as long as it meets the required conditions to imitate the rigidity, deformability, and elasticity of muscle tissue, while effectively transmitting driving forces.

[0017] The contraction unit (1), from the outside, has a hexagonal shape on its four faces, with a central part that can be more or less elongated (7). In three dimensions, it is a parallelepiped (7) having two pyramids (8) of identical size joined at its two furthest ends. The fibrous covering (5) of the unit must be braided so as to give this shape to the structure.

[0018] Within the framework of the motor formed by the assembly of these units (1), for the different faces of the contraction units (1) in contact, the fibrous coverings (5) that touch each other must be properly attached so that they form a single structure, that of the motor. These surfaces must therefore be braided together. The assembly of all the fibrous coatings (5) of all the contraction units (1) forms the structure, the coating of the motor (19). The motor is then attached at both ends of each by a totally rigid fiber (20) incapable of extending or shortening, which thins in length and can easily be attached to an external body, to which the motor can transmit its mechanical traction force. To ensure that the motor coating (19) and the rigid fiber (20) are properly bonded, they are braided together so that they form a single structure, although it may be composed of different materials and have different physical properties. An opening in the motor casing is provided to allow the passage of electrical wires linking the current source to the solenoids (2).

[0019] The contraction units (1), and more specifically the solenoids (2) in them, do not consume much electricity but require, in order to function efficiently, to be traversed by a powerful electric current, which is then lost if it is not reused downstream. The formula that links the power of the magnetic field generated by a solenoid (2) and the power of the electricity flowing through it is as follows:

[0020] [Math.l] A / m² = N x I x S

[0021] With "A / m²" the power of the generated magnetic field in Amperes per square meter. This power of the generated magnetic field is also called the "magnetic moment". "N" the number of turns of the solenoid (2). "I" represents the intensity of the electric current in Amperes. "S" is the surface area in m2 formed by one turn of the coil, the coil in question being here the solenoid (2), moreover, all the turns are supposed to be of the same size.

[0022] The formula for calculating the area in m² of a circle is:

[0023] [Math.2] 7TXR1

[0024] With " pi (ji) " approximately equal to 3.14.

[0025] And "R" the radius of the loop.

[0026] The only real electricity consumption of the solenoids (2) is the energy loss by Joule effect, it is a part of the electricity which is converted into heat, and therefore lost.

[0027] In the case of the motor consisting of the assembly of many contraction units (1), in order for it to function correctly, the power supply of the units (1) must be adapted and a distribution network made. For this motor to respond correctly to its functions, it must be able to activate up to all of its contraction units (1) in a synchronized manner. For this purpose, power supply lines (21) are present along the length of the motor, supplying all the contraction units (1) along their path, with a sufficient number of lines (21) to supply all the units (1). These lines (21) are each series circuits, because series circuits have the property of maintaining a constant current (in Amperes) at every point so that all the units (1) in the line receive exactly the same current and therefore generate a magnetic field of the same strength. Thus, a portion of the voltage (in Volts) will decrease along the circuit, consumed by the Joule effect of the solenoids (2), it being specified that the voltage does not influence the strength of the generated magnetic field.

[0028] Each supply line (21) will need to be connected to the power source, these lines (21) all connected to the source form a parallel branch, which inevitably distributes the current delivered equally over the supply lines, . the maximum intensity that these lines (21) can supply to the contraction units (1) is greatly reduced compared to the maximum intensity supplied by the power source, so the more lines (21) are added the more the intensity is split between them. For example, for a battery that delivers an intensity of 5 Amps and that supplies two supply lines (21), the voltage in the lines (21) will be only 2.5 Amps, if two more lines (21) are connected, there will be only 1.25 Amps in each of the lines. We end up with a 5 Amp battery, but which will only be able to deliver 1.25 Amps to the units (1), the initial current is divided by the number of lines (21) that it powers. If we want to be able to supply the contraction units (1) with a certain intensity, the power source must deliver much more than that.

[0029] If this becomes a problem, the required voltage can be reduced by ensuring that the power supply comes from only one initial source and that all the supply lines (21) can be connected to it in series one after the other with an opening / closing system that allows selection of the combinations of lines (21) in which to allow current to flow or not. This means that regardless of the combinations, even if all lines (21) are open, the circuit will always be a series circuit and therefore delivers the entire available current on this single circuit, it is no longer distributed. Another solution would be to use an upstream transformer that can convert part of the voltage into the missing current before delivering it. Alternatively, something could be placed at the end of the line (21) to recover the electricity (transformer, batteries, etc.) and redirect it to other electrical systems. All of these solutions mentioned above remain optional, and their presence or absence does not affect the proper functioning of the invention.

[0030] To calculate the force of a unit contraction (1), it is necessary to multiply the magnetic moment of the solenoid (2) in Ampere per square meter, by the magnetic flux density in Tesla of the magnet (3).

[0031] The formula that gives the traction power of one unit (1) is therefore:

[0032] [Math.3] A / m 2 x T = N / m

[0033] With "A / m2" in Amperes per square meter.

[0034] "T" in Tesla

[0035] And "N / m" in Newton-meters

[0036] The magnetic moment of the solenoid (2) in A / m2 is calculated using the formula mentioned above:

[0037] [Math.4] N x I x S- Al m-

[0038] (Number of turns times Intensity times Surface equals magnetic moment.)

[0039] That said, we can replace the Amperes per square meter with the formula which allows us to to obtain them and thus express the traction power of one unit (1) in the form:

[0040] [Math.5] Tx (NxIxS) =N!m

[0041] But Amperes per square meter can also be expressed in Newton-meters per Tesla:

[0042] [Math.6] 4 / N / m

[0043] Therefore, expressing it in this way in the formula:

[0044] [Math.7] Al m1* T -NI m

[0045] We obtain:

[0046] [Math. 8] ^*T = ^=Nhn

[0047] The "T"s cancel out in the numerator and denominator.

[0048] With the "T" of the numerator which is the value of the magnetic flux density of the magnet (3) in Tesla (do not forget to select the flux density exerted by the magnet (3) in Tesla at the corresponding distance between the two dipoles, and not the default value of the flux density of the magnet (3) because this is the value exerted by the magnet (3) at its own surface.) To know the total power of the motor made up of the assembly of contraction units (1) it is necessary to multiply the result, (the traction force of one unit) by the total number of units (1) which make up this motor, on the basis of the principle that all the units (1) in a motor are supposed to be identical, although the assembly of units (1) of different sizes is not impossible.

[0049] To calculate the Volts consumed along a series circuit, it is done in two steps:

[0050] First, the Joule effect, the power dissipated in Watts "W" is calculated by the formula:

[0051] [Math.9] W = RxI2

[0052] With "I" the intensity in Amperes.

[0053] And "R" the resistance of the copper wire in ohms, it can be calculated by the formula:

[0054] [Math. 10] R = P x L + S

[0055] With "P" the resistivity of copper in ohm / meter = l,7xl0e-8.

[0056] "L" the length in meters.

[0057] And "S" the cross-section of the copper wire in m2.

[0058] Next, to determine how many volts will be missing at the end of the line depending on the watts consumed by the Joule effect, we do:

[0059] [Math. 11] V = W^Z

[0060] With "V" in Volt.

[0061] "I" in Amperes.

[0062] And "W" in Watt.

[0063] With an intensity that does not vary in a series circuit (law of uniqueness of intensity in a series circuit) we deduce the missing Volts at the end of the line, consumed by the Joule effect.

[0064] This invention finds its use in the improvement of mechanical limb prostheses, in the field of robotics, to make the movements of Android and humanoid robots more realistic, however a new type of motor is inexorably opening the way to new demands and applications, this invention is therefore likely to have many other present and future applications in very varied fields.

Claims

Demands

1. A motor capable of contracting upon itself in order to transmit its mechanical force to another body attached to it, characterized in that it contracts upon itself when an electric current is delivered to it, and thus converts electrical energy into mechanical energy; this unit (1) is delimited by a fibrous coating (5) the interior of which is composed of a solenoid (2) contained in a plastic support (6) which deploys a magnetic field when electricity flows through it, and a permanent magnet (3) both facing each other; this device then exploits the mutual magnetic attraction force between the permanent magnet (3) and the solenoid (2) by transmitting it through central fibers (4) to the walls of the unit (5) in which they are contained;This mechanical force, once propagated through the central fibers (4) into the walls of the unit (5), has the effect of contracting the unit (1) upon itself; this force can then be transmitted to another body through contact with the fibers of the coating (5).

2. Motor according to claim 1 characterized in that spring dampers (10) are placed between the central fibers (4) inside the units (1) in order to perform various functions, including an influence on the mechanical forces and the contribution to the biomimicry of the units (1) and by extension of the motor.

3. Motor according to the preceding claims characterized in that the motor consists of a pattern assembly of several of these units (1); motor also having the property of being able to contract on itself, of converting electrical energy into mechanical energy, and which has the purpose of transmitting up to the whole of the cumulative mechanical force of the units (1) in their common coating (19) to an external body attached thereto by the gripping fibers (20) of the motor provided for this purpose.

4. Motor according to the preceding claims, characterized in that the unit (1) and the motor directly deliver their mechanical force in the form of a shortening on themselves, without requiring any additional external installations, and this respectively in each of their cases, installations which would serve as a "converter", that is to say, which would be capable, once assembled with the unit (1) or with the motor, of changing the driving force which would initially be delivered respectively by the unit (1) and / or the motor in the form of rotation or otherwise, as motive force delivered by contraction on themselves.

5. Motor according to the preceding claims characterized in that it can have the desired shape and dimensions depending on the number of units (1) which constitute it and the way in which they are assembled.

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