MXPA01000770A - Accurate rotor position sensor, method using magnet ring and linear output hall effect sensors - Google Patents

Abstract

An inexpensive and accurate device for sensing rotor position and detecting rotational speed over a broad range of speeds in an electric motor includes a sense ring magnet (200) and two analog Hall effect sensors (108, 109, 722). The sense ring (200) is magnetized in an alternating north-south fashion with a number of poles that correspond to a number of motor field poles. The Hall effect sensors (722) are placed so that they measure magnetic flux tangential to the sense ring. The Hall effect sensors (722) are preferably located at a distance from the sense ring where the Hall effect sensor output waveforms are substantially triangular, with a highly linear portion centered at zero flux between the minimum and maximum waveform peaks. The linear portions of the waveforms are decoded using an A/D converter and control software to provide an accurate measure of the rotor (724) position.

Description

DETECTOR OF THE PRECISE POSITION OF A ROTOR, METHOD THAT USES A MAGNET RING AND LINEAR OUTPUT HALL EFFECT DETECTORS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates generally to the field of electric motors and, in particular, to a detector and the method for accurately detecting the position of a rotor of a brushless electric motor using a sensing element. magnetic and linear output Hall effect detectors. 2. Description of Related Art Electric motors that require waveforms controlled in the current of the armature (for example, to rotate uniformly) also require accurate detection of the rotor position. Some engines use technologies without a detector, but these technologies do not provide detection of the precise position of the rotor at very low speeds and are not uniform at the start of the engine. Other engines inherently can not use technologies without a detector and must incorporate a mechanism for detecting the position of the rotor. Currently, state-of-the-art motors use either an encoder or a resolver together with the associated electronic circuitry to determine the rotor positions. However, depending on the resolution required, these solutions can become prohibitively expensive in applications that require low cost engines. In particular, many electric motor applications require smooth rotation and / or accurate P 10 control. Brushless motors usually achieve this by using 3-phase sine wave switching and precise rotor position detectors, usually in the form of an encoder or resolver. The precise position detector of the rotor ensures that the wave The sine-wave remains synchronized with the rotor, thus avoiding the fluctuation of the torque induced by the switching. The methods currently used in the ßk industry to accurately detect the positions of the rotor, use encoders and resolvers and have been known and used in motor units for many years. The encoders detect the mechanical movement and convert this detected motion into electrical signals. Optical encoders are the kind of most common encoder. An optical encoder usually includes a housing for supporting precision bearings and electronics, an arrow with a disk that is called an "optical disk" and having alternating transparent and opaque segments, a light-emitting diode (LED) for its acronyms in English) and a phototransistor receiver. A beam of light produced by the LED is pointed towards the optical disk. When the optical disc rotates, the beam of light passes through the transparent segments, but is blocked by the opaque segments, so that the optical disk makes f * 10 effectively push the beam of light. The pulsed light beam is received by the phototransistor receiver. The phototransistor receiver and the circuitry inside the encoder together supply signals to the controller of a motor outside the encoder and can also perform functions, such as improving noise immunity. The encoders in their simplest form have an output to determine the rotational speed of the arrow or to measure the number of revolutions of the arrow. Other encoders have two outputs and can provide the information on the direction of rotation as well as the speed and the number of revolutions. Other encoders additionally provide an index pulse, once per revolution, which indicates an absolute position of the rotor. The description is related specifically to encoders by increments, where after the start, the position of the encoder is not known. A second type of encoder, called an absolute encoder, has a unique value for each mechanical position during a whole rotation. This unit normally consists of the incremental encoder described above, with the addition of another signal channel that serves to generate the absolute position information, normally of less precision. Within an absolute encoder that is provided with an index pulse, the accuracy improves once the rotor crosses the index pulse. Increment encoders may be acceptable within asynchronous motors, where speed feedback is very important. Absolute encoders are desirable in synchronous motor applications, where both position and velocity feedback are important. Several companies produce another class of high resolution encoders referred to as "sine / cosine encoders". Sine / cosine encoders generate sine and cosine signals instead of pulse waveforms. When used with additional electronic components, processor capacity and software, the sine / cosine encoders indicate the position of the rotor with a fine resolution. The encoders of all types are sensitive devices, built with precision, which must be matched and calibrated mechanically, electrically and optically. On the other hand, the resolvers usually provide a period of signal per revolution and are known to be very tolerant of vibration and high temperatures. Typical use of this technology would include a resolver that generates two signals, a sine wave signal and a cosine wave signal, for every 10 ^ revolution. The advantage of using resolvers is that they provide information on the absolute position of the rotor, rather than incremental information, as is typical of most encoders. However, a major disadvantage is that the solvers deliver a performance increasingly deficient at low speeds. Due to this limitation, the possible range of the speed control with the resolvers is much smaller than with the encoders, in the order of 200: 1. In accordance with this, the use of resolvers is normally limited to applications that do not require high quality motor control over a wide range of speeds. As with encoders, resolvers are precisely constructed, commercially available detection devices that can be fragile and costly. 25 Ring magnets and digital Hall effect detectors are frequently used as a rotor position sensing mechanism in brushless direct current (DC) motor applications, where • use square wave or six-step units. This detection method provides a low resolution, typically six positions per electric cycle when three detectors are used. The six-step unit does not require a high resolution in detecting the position of the rotor, however, this is acceptable. At the same time, these driving methods also do not result in a torque without fluctuations from the engine. This may be unacceptable in a variety of applications.

OBJECTS AND SUMMARY OF THE INVENTION In accordance with the foregoing, there is a need for a precise and inexpensive device that | fc detect the position of the rotor and detect the rotation speed. In accordance with one modality of the According to the invention, this need is satisfied by providing a unit that includes a magnetic sensing element, such as an economical annular detection magnet and two analogue Hall-effect detectors. In this embodiment, the detection element is fixed with respect to the rotor of the motor and the detectors are fixed with respect to the motor stator. The detection ring is magnetized in an alternating north-south shape where the number of poles corresponds to the number of field poles of the motor. Hall effect detectors are positioned so that they measure the magnetic flux tangential to an outer circumference of the ring and at a certain distance from it. The orientation of the Hall effect detectors to measure the tangential magnetic flux to an outer circumference of the ring and at a certain distance from the ring, results in a Hall effect detector that emits a voltage waveform that is practically triangular, with a very linear centered in the zero flow, between the minimum and maximum peaks. This linear portion can be decoded using, for example, an analog-to-digital (A / D) converter and control software, for the accurate measurement of the rotor position. The waveform of the cycle or output repeats itself in each pair of poles. For example, when there are only two pairs of equally spaced poles, the output waveform of a Hall effect detector will be repeated twice for each mechanical revolution, that is, it will have two complete electrical cycles. Accordingly, the method of the invention can be used to decode the position of the rotor in a complete electric cycle or relative to a complete electric cycle, although not necessarily in a complete mechanical rotation that includes more than one electric cycle, unless I also know • provide an absolute position reference, such as 5 an index pulse. The relationship between electrical and mechanical degrees is given as ° E = ° -PP, where ° E represents electrical degrees, ° M represents mechanical degrees and PP represents the number of magnetic pole pairs of the motor W 10. By detecting the absolute position of the rotor in a complete electric cycle, the current can be controlled precisely at all times to result in a uniform rotation of the rotor. In accordance with another embodiment of the invention, the two Hall-effect detectors can be placed further away from the detection ring, so that each Hall effect detector emits a form of F wave practically sinusoidal. When two Hall effect detectors are placed with a separation of 90 electric degrees, one output becomes a sine wave and the other becomes a cosine wave. Further features and advantages of the invention will be apparent from the following description of the preferred embodiments, taken together with the accompanying drawings. The accompanying drawings illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS 5 FIG. 1 is a side view along a radial direction of magnetic fields generated by a multi-pole sensing disk magnet that is magnetized in an axial direction. Figure 2 is an end view along an axial direction of magnetic fields generated by a multi-pole sensing ring magnet that is magnetized in the radial direction. Figure 3 is a graph of a magnetic field close to and normal to an axial face of the disk magnet of figure 15 to a radial face of the ring magnet of Figure 2. Figure 4 is a graph of a magnetic field parallel to an axial face of the disk magnet of figure 1 • or tangential to a radial face of the ring magnet of figure 2, which was measured at the distance of an air gap away from the disk or ring. Figures 5A and 5B show the outputs of two Hall effect detectors, located near a detection disk or a detection ring of a modality Preferred of the invention and a range in which the outputs are used to decode the position of the rotor. Figure 6 is a graph of a tangential magnetic field to one face of the disk magnet of Figure 1 or the ring magnet of Figure 2, at a greater distance than that shown in Figure 4. Figure 7 is a side view of an electric motor with a detection ring, in accordance with one embodiment of the invention. Figure 8 is a side view of an electric motor with a detection disk, in accordance with an embodiment of the invention. Figure 9 is a side view of an electric motor with a detection ring, in accordance with an embodiment of the invention. Figure 10 is a front view of a conventional 3-conductor Hall effect detector.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In accordance with the invention, the magnetic detection element can be configured in a variety of ways. For example, the magnetic sensing element may be a magnetized ring, that is, a detection ring or a magnetized disk, ie, a detection disk and may be magnetized axially or radially. In a first preferred embodiment of the invention, the ring or disc is magnetized with several magnetic poles that coincide with the various field poles of the motor. By making the number of poles • magnetic is equal to the number of field poles of motor 5 is achieved that, in general, the process of decoding the outputs of the Hall effect detector to indicate the position of the rotor is simplified. The magnetic poles of the ring or disk alternate polarity, as shown in Figures 1 and 2. In particular, Figure 1 shows a side view of an axially magnetized disk 100, while FIG. 2 shows a radially magnetized ring 200. The waveforms shown in Figures 3 to 6 represent the relationships between the position of the rotor and the measured magnetic flux, with the position of the rotor at along the horizontal axis and the magnetic flux measured along the vertical axis. Figures 7 and 8 show electric motors with a detection ring and a detection disk, respectively, in accordance with the • embodiments of the invention. Figure 7 shows a motor 700 having a stator 716, a rotor 724 and an arrow 712, positioned within a housing 710. The housing 710 supports the arrow 712 by the bearings 726. A detection ring 200, like the shown in figure 2, is fixed to the arrow 712 and rotates with the arrow 712 and the rotor 724 around an axis 714. A Hall effect detector 722 is placed near the detection disk 200 via a support 720, so that the detector 722 measures the flow of the detection ring 200 which is tangential to an outer circumference 219 of the detection ring 200. See, for example, Figure 2, wherein the Hall effect detectors 108 and 109 are oriented to measure the magnetic flux which is parallel or tangential to the outer circumference 219, ie, perpendicular to the radial direction 202. The detector 722 is fixed with respect to the stator 716. The detection ring 200 includes magnets 204 arranged so that the ring 200 is magnetized in radial directions from a axis of rotation, for example, in the radial direction 202. The ring 200 is provided with an inner ring or backing material 206. The material 206 may be a soft magnetic material, for example or, a ferrous material such as carbon steel or it can be a non-magnetic material, for example, nylon. Figure 8 shows an engine 800 that is similar to the one shown in Figure 7, but has a detection disk 100 similar to that shown in Figure 1. A support 820 locates the Hall effect detector 722, so that the detector 722 measures the magnetic flux of the detection disk 100 which is perpendicular to the axis of rotation 714 and parallel to a face 119 of the detection disk 100. See, for example, Figure 1, wherein the Hall effect detectors 108 and 109 are oriented to measure the flow • magnetic that is parallel to a face 119 of the detection disk 100, that is, perpendicular to an axial direction 102, around which the disk 100 rotates. 202. As in Figure 7, the detector 722, according to shown in Figure 8 is fixed with respect to the stator 716. The disk 100 includes magnets 104 arranged such that the disk 100 is magnetized in the axial direction 102. The disk 100 is also provided with a backing material 106 that is magnetically soft, such as ferrous material such as carbon steel or is it not magnetic. Each magnetic pole of the detection disk or disk must be uniformly magnetized, either in radial or axial direction, so that the "wave conformation" of magnetization is not necessary. The magnets can are made of an inexpensive material, such as ferrite or bound NdFeB. Hall effect detectors should be of the analogous linear type, with a signal output that is linear in a certain range of magnetic flux (± | B |). For example, analog linear Hall effect detectors, which are suitable and currently available, typically have linear magnetic flux ranges between approximately ± 500 gauss and ± 1,500 gauss. • The detectors 108 and 109 are aligned or oriented, so as to measure the magnetic fields perpendicular to the magnetization directions 102 and 202. In other words, the detectors are aligned to measure the magnetic flux tangential to the surface of the ring or disk detection. w? As will be appreciated by those of ordinary skill in the art, a Hall effect occurs when, in the context of a three-dimensional coordinate system with three orthogonal axes x, y, z, an element carrying an electric current in the direction of the x axis is placed on a field magnetic whose flow or, lines of force, are aligned parallel to the z-axis. Because the charged particles that pass through a magnetic field experience a Lorentz force, the electrons that • travel in the direction of the x-axis will be diverted by a Lorentz force in the y-axis direction. This creates an imbalance of charges across the current carrying element in the direction of the y axis, and a corresponding voltage across the current carrying element in the direction of the y axis. 25 A typical Hall effect detector has a plane element oriented in the x-y plane, where current is flowing through the element in the direction of the x-axis. When the magnetic flux along the z-axis happens to • Through the element, a voltage will appear across the element in the direction of the y axis, which is proportional to the magnetic flux passing through the plane element. This voltage is the output of the Hall effect detector. In a situation where the Hall effect detectors 108 and 109 are provided with a flat conductor element flfc 10, the view of FIGS. 1 and 2 of the Hall effect detectors 108 and 109 is along an edge of the conductive element. plane of each detector. In other words, the plane of the element can be defined by the axis of rotation of the disk 100 or of the ring 200 and a radial direction of the disc 100 or of the ring 200 that intersects the axis of rotation and that is perpendicular thereto. When the detector 108 is positioned on a pole, as shown in FIGS. 1 and 2, through the • detector 108 does not pass any magnetic flux and voltage to through its plane element in a direction perpendicular to the direction of current flow will be zero. As can be seen from Figures 1 and 2, with reference to the detectors 109, the magnetic flux passing through the detector 109 is at a maximum when the detector 109 is located equidistantly between two adjacent magnetic poles and the magnitude of the voltage across its planar element in a direction perpendicular to the direction of current flow will be at a maximum. • Figure 10 shows a front view of a conventional Hall 1000 effect detector with three electrical conductors 1002, 1004 and 1006. Normally, one of the conductors is connected to ground, another is connected to a voltage source and the third provides the output voltage of the detector, which indicates the magnitude and dfc 10 direction or polarity of the magnetic flux passing through the flat face of the detector 1000. The conventional three-conductor Hall effect detectors, such as the detector 1000, typically are set so that the output voltage of the detector in the third conductor, varies from 0 volts up to the source voltage, where 0 volts represents the maximum magnetic flux with a first polarity and the voltage of the source ^^ represents the maximum magnetic flux with the opposite polarity and an output of half the voltage of the source is a fixed output representing a zero magnetic flux passing through the detector. The Hall effect detectors 108 and 109 may be of this type or may be of any other suitable type of Hall effect detector. The Hall effect detectors 108 and 109 can be located at a specified iron distance from the surface of the detection ring or disk, so that the waveform output of each of the detectors 108 and 109 will be quasi-triangular, as shown • in Figure 4. The output of the waveform shown in Figure 4 is a graph of the output voltage of the detector along the vertical axis and the position of the detector with respect to the disk 100 or the ring 200 a along the horizontal axis. The air gap distance can be, for example, of the order of 100 thousandths of fB) 10 inch (about 2.5 millimeters) or less. The distance of the air gap to which the output of the Hall effect detector will be quasi-triangular may vary, depending on the particular characteristics of the detection ring and the Hall effect detector used and can be easily determined by experimentation, providing the specific device components and conditions of use. At an additional distance, the waveform output becomes sinusoidal, as • shown in figure 6. 20 By contrast, the traditional Hall effect detector arrangements align Hall effect detectors to measure magnetic flux in the direction of magnetization, normal to the detection ring and emit similar flow waveforms to those shown in the Figure 3. For example, with respect to Figures 1 and 2, a Hall effect detector arranged in the traditional manner, would have its conductive element flat parallel to the surface 119 or tangential to the surface 219 and would have • a maximum output at a magnetic pole and a minimum output 5 at an equidistant location between two adjacent magnetic poles. As shown in Figure 3, the waveform generated using traditional arrangements of the Hall effect detector is linear, i.e. has a constant slope, only for a small portion of the waveform period, near the crossings of zero flow. In the rest of the waveform period, the waveform is curved and then relatively flat (that is, it has a low value slope) for a large waveform. portion of the period of the waveform, near the ends of the waveform. This conformation of the waveform will not produce an accurate detection of the rotor position for several reasons. The first, the conformation of the waveform , which is shown in FIG. 3, is undesirable because only a small portion of the period of the waveform is linear. By contrast, the ideal conformation of the waveform would have a linear slope during at least half the period of the waveform. It is desirable linear form, because the conversion or decoding of a voltage level in a rotor position can be made more simply and consistently when the voltage level changes linearly with the position of the rotor. Second, the waveform shown in Figure 3 is relatively flat for a large portion of the period of the waveform, near the ends of the waveform; this is undesirable because the ratio of the voltage change to the change in rotor position becomes smaller as the slope of the waveform is flattened. This small proportion requires greater measurement sensitivity and increases the vulnerability of the system to noise. Third, for the portions of the period of the waveform, where the shape of the waveform is curved, the shape of the curve must be known and additional calculations must be made, using the shape of the curve to determine the shape precise the position of the rotor. Figure 4 shows a waveform of the output of the Hall effect detector which is much more desirable than the waveform shown in Figure 3. As shown in Figure 4, the conformation of the waveform surrounding the The crossing of the zero flow is linear, while the conformation of the waveform in the peaks is slightly rounded. As shown in Figure 4, more than half of the shaping of the waveform is linear. A preferred embodiment of the invention • avoid using the rounded waveform conformation 5 at the peaks to determine the position of the rotor using two linear Hall effect detectors, separated by 90 ° electrical. The information of the position of the rotor is supplied by both detectors in alternate form, as shown, for example, in FIGS. 5A? 10 and 5B, so that only the linear portions of the output waveforms of the detector are used. Since the output waveforms of the detector are not linear only near their peaks, the nonlinear portions of the waveform forms can be identified. wave when comparing an output of the detector with a threshold value, which is less than or equal to a magnitude below which the waveform is linear and above which the waveform is not linear. As can be seen in Figures 4 and 5A, the The waveform of each detector is generally linear within approximately 60 ° on each side of a junction with zero of that waveform. Since the two detectors (and, therefore, their respective crossings with zero) are separated by 90 ° electrical, for example, the detectors of Hall effect 108 and 109, as shown in FIGS. 1 and 2, this means that both detectors 108 and 109 simultaneously will have a linear output in a region halfway between two adjacent zero junctions, in • where one of the crosses with zero adjacent is the zero crossing of the detector 108 and the other crossing with the adjacent zero is the zero crossing of the detector 109, for example, two adjacent zero crossings of the 550 and 560 waveforms of figure 5A. Since the distance between the detectors 108 and 109 (and, thus, the waveforms 550 and 560) is of fl 10 90 electrical degrees and, since each of the wave forms 550 and 560 is practically linear within of the 60 electric degrees on either side of its junction with zero, the width of each superimposed region, where both waveforms 550 and 560 are simultaneously linear is 30 electrical degrees. Thus, in any position at least one of the detectors 108 and 109 will have a linear voltage output with respect to the position of the detection element with respect to the detector and in some • positions (between 30 and 60 electrical degrees away from each zero of the waveform) both detectors 108 and 109 will have a linear output. If detectors are used where the output waveform of each detector has a linear region that covers less than 60 electrical degrees on each side of a junction with zero of that detector, then the region of overlap where both detectors have a linear output, will be correspondingly smaller. Where each of the two detector waveforms is linear within 45 ° of a zero crossing of that waveform, but which is not linear beyond 45 ° from the zero crossing (up to that is within 45 ° of the next zero crossing of that waveform), then, because the two detectors 108 and 109 are separated by 90 electrical degrees, the linear regions of the two w? 10 waveforms will not overlap although in any location one of the waveforms will be linear. A simple solution is to choose the threshold value equal to the value of the waveform that occurs in plus or minus 45 electrical degrees of the zero crossing of the form wave. With this threshold value, as shown in Figures 5A and 5B, at any time point and only one of the two detectors 108 and 109 will have an output that is below the threshold value. In this way, the • Motor controller can use this threshold value to To easily determine which detector to attend for information on the position of the rotor. In particular, as shown in Figure 5A, one of the detectors 108 and 109 emits the waveform 550 and the other detector emits the waveform 560. The axis The vertical represents the voltage and the horizontal axis represents the position, for example, the positions of each detector with respect to the detection element. A reference line 574 is placed at 45 electrical degrees from the • source 576, which is also a "zero point junction" of waveform 550. Waveforms 550 and 560 are linear between thresholds 570 and 572. The linear segments of the two waveforms 550 and 560 which are located between the thresholds, are labeled 550A-F and 560A-F. The reference lines 578 and 580 are fl 10 located at 45 electrical degrees of the zero point crossings of the waveforms 550 and 560. As can be seen in Figure 5A, each position along the horizontal axis corresponds to a point only in one of the segments 550-AF and 560A-F. Figure 5B is similar to Figure 5A, although it omits the portions of the waveforms 550 and 560 that fall outside the thresholds 570 and 572, so that the linear portions of the waveforms that will be used by the motor controller, i.e.

• Segments 550A-F and 560A-F can be observed more easily.

Each of the Hall effect detectors 108 and 109 will emit the fixed value Vfij0 when there is no magnetic flux passing through the Hall effect detector. For example, the Hall effect detector 108 has no magnetic flux passing through it and, thus, will emit the fixed value. When one of the Hall effect detectors 108 and 109 has the maximum amount of magnetic flux passing through it, such as, for example, the Hall effect detector 109 shown in Figure 1, it will emit either the minimum value Vm? Not the value maximum of Vmax. Whether it emits the maximum or the minimum value, the value depends on the direction in which the magnetic flux passes through the Hall effect detector 109. Since the magnets 104 alternate polarity and, thus, the direction of the flow In this case, the outputs of the Hall effect detectors 108 and 109 will also alternate between the minimum and maximum values, for example, as the Hall effect detectors 108 and 109 move through the magnetic fields in the direction 121 shown in FIG. Figure 1. When the Hall effect detectors 108 and 109 are of the conventional 3-conductor type, described above with respect to Figure 10, the maximum maximum value of the emitted waveforms 550 and 560 is an input voltage Vj. n, supplied to the corresponding Hall effect detectors, the fixed value Vfij0 or "zero" of the emitted waveforms 550 and 560 is half the input voltage or V? n / 2 and the minimum value Vm? n is zero volts. The absolute position of the rotor, in an electric cycle, can be determined using the two detectors. As shown, for example, in Figure 5A with respect to waveforms 550 and 560, for each waveform, all values of the waveform (with the exception of the minimum and maximum values) will be presented • twice in an electric cycle. For example, for a given value of the waveform 550 that is between the fixed voltage Vfij0 and the threshold 570, the position may be either in segment 550A or segment 550B. When a value of waveforms 550 and 560 is between thresholds 570 and 572, it is being used to indicate the ifl 10 position of the rotor, the value of the other of waveforms 550 and 560, can be used to determine which of the two segments of the first waveform should be used. For example, when a value of waveform 560 is above the fixed voltage, although by below the threshold 570 and the corresponding value of the waveform 550 is greater than the fixed voltage, the position of the rotor corresponds to the linear segment 560A instead of the linear segment 560B. In this way, waveforms 550 • and 560 indicate together an absolute position of the rotor in a electric cycle. In the above-described embodiment, two detectors are located separately at 90 electrical degrees and the thresholds 570 and 572 are chosen so that each location along the horizontal axis corresponds to with a point in a linear waveform segment.

However, other configurations may be used. For example, the distance between detectors can be adjusted to an appropriate value that is different from the electric 90 degrees, 5 more than two detectors can be used and the thresholds can be set differently. The reasons for using a different configuration may include, for example, using waveforms emitted by the detector that have different linear regions. The linear regions may vary, depending on the characteristics of the detectors, the air gap distances between the detectors and the sensing element, and other factors. Configurations that have: a) points in linear waveform segments only for some positions of the detector-detection element, b) multiple points in the linear waveform segments only for some detector-element detection positions or c) multiple points for each position, may also be useful or desirable in a variety of ways, depending on the particular applications of the invention. Preferred embodiments use a microprocessor based controller, to take the analog signals supplied by the linear Hall effect detectors and convert them into digital signals, using an A / D converter. This configuration can provide a high resolution in the detection of the rotor position. For example, suppose that an engine contains eight pairs of poles and that each diagonal line in Figure 5 is equal to 256 stages of rotor position. 5 Because there are eight electrical cycles per rotation and four lines per electric cycle, the total resolution per rotation is equal to 8192 (256 x 8 x 4). This is an excellent resolution in a motor driven system. Another significant advantage is that this system can be incorporated into an engine at a low cost. In another embodiment of the invention, the air gap between the detection ring and the detector is increased, so that the detector output describes a substantially sinusoidal waveform, as shown in Figure 6.

In particular, Figure 6 shows the output waveforms of two detectors located with a separation of 90 electric degrees, wherein the waveform 630 corresponds to a first detector and the waveform 632 • corresponds to a second detector. The information of The position can be decoded or extracted from the practically sinusoidal waveforms 630 and 632, shown in Figure 6, applying principles well known in the art, similar to the "sine-cosine" method used within some conventional resolvers. As in the method of the triangular waveform described above with respect to Figures 4 and 6, the portions of each waveform closest to the zero flow crossings of the waveform may be the primary signals • used to decode the position of the rotor. In another embodiment of the invention, a single analog switch is used, that is, a Hall effect detector, with a detection ring. The linear portions of the detector output can be used as described above to determine the position of the rotor 10. The non-linear portions of the detector output close to the peaks of the waveform can either be ignored or used to estimate the position of the rotor.You can also use the rotor speed and acceleration information to estimate the position of the rotor during a period of time in which the output of the detector is not linear. In another embodiment of the invention, two detection rings and at least two and, of • preference 3, Hall effect detectors. A ring is used to detect the high resolution increases and the other ring was used to detect the absolute position. When three detectors are available, two of the detectors can be used with the high resolution detection ring, to provide an indication of the The absolute position of the rotor in an electric cycle and the third detector can be used with the absolute position detection ring to provide information that can be used to indicate in which electrical cycle of the mechanical revolution the rotor is located. The high resolution detection ring preferably has a number of magnetic poles that is equal to the number of field poles of the motor or is equal to an integer multiple of the number of field poles of the motor. The absolute position detection ring has two poles (magnetic north and south magnetic), the poles can have the same size, for example each pole occupies half or 180 ° of the detection ring. pole can occupy a larger portion of the absolute position detection ring and the other pole can occupy the rest, a smaller portion of the ring. As an alternative mode, with the high-resolution detection ring, at least one detector and the position detection ring can be used.

• Absolute can be used with two detectors mounted with one separation of 90 °, which have two poles, so that the absolute mechanical position of the rotor can be determined at any moment of time. As a further alternative, a different method can be used that does not use an effect detector Hall oriented to measure the tangential magnetic flux to the surface of the sensing ring or disk to supply the absolute position signal once for each mechanical revolution of the rotor. In another embodiment, an analog signal from a Hall effect detector is used to directly detect the position of the rotor, instead of a digital signal which is based on the analog signal and which is obtained by supplying the analog signal to an A converter. / D. According to one embodiment of the invention, the Hall effect detectors can be fixed with respect to the motor rotor and the detection element can be fixed with respect to the motor stator. According to one embodiment of the invention, the number of magnetic poles of the detection element is different from the number of field poles of the motor. For example, a greater number of magnetic poles of the sensing element than the motor poles of the motor can be provided. In general, when poles of the sensing element are used to determine an increase in the position of the motor rotor with respect to the stator of the motor, the increase in the number of poles of the sensing element increases the accuracy and resolution of the increase in position. determined. The detection disk or disk can be made of, for example, ferrite, bound NdFeB, sintered NdFeB or SmCo. Other detectors in addition to the Hall effect detectors that also generate a practically triangular or sinusoidal output waveform that is a 5-position plot against the detector output, can be used instead of or in addition to the detector detectors. Hall effect. Figure 9 shows another embodiment, wherein a motor 900 is similar to the motor 700 shown in figure 7, f 10 although it differs in that the detection ring 902 has the form of a vessel or cup, so that the magnets 904 are arranged in the inner diameter of the edge of the cup 906, which is formed of weak or non-magnetic magnetic material. A support 920 holds the effect detector Hall 922 near the inner diameter of the ring formed by the magnets 904 along the edge 906 of the cup. Although the invention has been described in detail with reference only to the modalities currently • preferred, those skilled in the art will appreciate that Various modifications can be made without departing from the invention. Accordingly, the invention is defined only by the following claims, which are intended to cover all equivalents thereof. 25

Claims (20)

1. CLAIMS; A device for detecting the rotation position, comprising: • a first detection element with a first multitude of magnetic poles uniformly spaced around an axis of rotation of the first detection element; and at least one detector mounted for measuring a first magnetic field in a direction of rotation 10 perpendicular to the magnetization direction of the first multitude of poles of the magnetic detection element, wherein the first magnetic field is generated by the first multitude of magnetic poles of the detection element.
2. 2. The device according to claim 1, wherein the at least one detector is a Hall effect detector.
3. 3. The device according to claim 1, wherein the first magnetic poles of the element of 20 detection are uniformly magnetized.
4. The device according to claim 1, wherein the magnetization direction is parallel to an axis of rotation of the first detection element.
5. The device according to claim 1, wherein the magnetization direction is radial to a rotation axis of the first detection element.
6. The device according to claim 1, wherein the at least one detector includes a first • Hall effect detector and a second effect detector 5 Hall mounted with a separation of 90 electrical degrees with respect to the first Hall effect detector.
7. The device according to claim 1, wherein the at least one detector is a Hall effect detector that is mounted at a predetermined distance from the detector. 10 first detection element, so that the output of the detector is practically triangular.
8. The device according to claim 1, wherein the at least one detector is mounted at a predetermined distance from the first detection element, 15 so that the output of the at least one detector is practically sinusoidal.
9. The device according to claim 1, wherein at least one of the first and second detection elements is formed of at least ferrite, bound NdFeB, sintered NdFeB and SmCo.
10. The device according to claim 1, further comprising: a second detection element with at least two magnetic poles; and at least one mounted detector for measuring a second magnetic field in a direction of rotation perpendicular to a magnetization direction of the at least two magnetic poles, wherein the second magnetic field is generated by the at least two magnetic poles. .
11. The device according to claim 10, wherein the at least one detector mounted to measure the second magnetic field is a Hall effect detector.
12. The device according to claim 10, wherein the at least one detector mounted for measuring the second magnetic field is used to measure an absolute position of the second detection element, with respect to the at least one mounted detector for measuring the second magnetic field and the at least one detector mounted to measure the first magnetic field is used to measure an increase in the position of the first detection element, with respect to the at least one detector mounted to measure the first magnetic field.
13. The device according to claim 10, wherein the at least one of the first and second detection elements is formed of at least ferrite, bound NdFeB, sintered NdFeB and SmCo.
14. 14. An electric motor with a device for detecting the rotation position, comprising: a detection element with a first multitude of magnetic poles uniformly spaced around an axis of rotation of the detection element; and at least one detector mounted to measure a • first magnetic field in a direction of rotation 5 perpendicular to a magnetization direction of the first multitude of poles of the magnetic detection element, wherein the first magnetic field is generated by the first multitude of magnetic poles of the detection element.
15. The device according to claim 14, wherein the number of poles of the magnetic detection element equals the number of field poles of the motor.
16. 16. The device according to claim 14, wherein the detection element is fixed with respect to the 15 motor rotor and the at least one detector is fixed with respect to the stator of the motor.
17. 17. A method for controlling a brushless electric motor that has a rotor, a detection element • with a multitude of magnetic poles and at least one 20 mounted detector for measuring the magnetic flux of the magnetic poles in a direction tangential to the detection ring, wherein one of the detection ring and the detector is mounted in a fixed relationship with the rotor, comprising the steps of: magnetic flow tangential to the at least one detection element, using the at least one detector and emitting a corresponding measurement signal for each of the at least one detector; • use the measurement signal to decode the rotor's rotational position; and controlling the motor based on the position of the decoded rotor.
18. 18. The method according to claim 17, wherein the measurement signal has a substantially triangular waveform shape.
19. 19. The method according to claim 17, wherein the measurement signal has a substantially sinusoidal waveform conformation.
20. 20. The method according to claim 17, wherein the number of the plurality of magnetic poles is equal to the number of field poles of the motor.