• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    method for operating a metal detection system and a metal detection system. The present invention relates to a method that serves to operate a metal detection system comprising a balanced coil system (2) with a transmitting coil (21) that is connected to a transmitting unit (1), which provides transmitter signals (s1) having a selectable transmitter frequency (ftx), and with first and second receiver coils (22, 23) providing output signals (s22, s23) to a receiver unit (3), the which compensate each other in the case where the metal detection system is in equilibrium and, in the case where a product (p) is present in the balanced coil system (2), provide an output signal that is transferred to a signal processing unit, which suppresses at least the product signal components and supplies the signal components by metallic contaminants contained in the product (p)
    公开号:BR112013008207B1
    申请号:R112013008207-0
    申请日:2011-09-21
    公开日:2021-06-01
    发明作者:Max Derungs
    申请人:Mettler-Toledo Safeline Limited；
    IPC主号:
    专利说明:

    [0001] The present invention relates to a method for operating a metal detection system that uses at least two operating frequencies and a metal detection system that implements this method.
    [0002] An industrial metal detection system is used to detect and reject unwanted metal contamination. When properly installed and operated, it will help reduce metal contamination and improve food safety. Most modern metal detectors use a search head that comprises a "balanced coil system". The detectors in this project are capable of detecting all types of metallic contaminants including ferrous, non-ferrous and stainless steels in a wide variety of products such as fresh and frozen products.
    [0003] A metal detection system that operates according to the "balanced coil" principle typically comprises three coils that are wound over a non-metallic structure, each one exactly parallel to the other. The transmitter coil located in the center is energized with a high-frequency electrical current that generates a magnetic field. The two coils on each side of the transmit coil act as receiver coils. Since the two receiver coils are identical and installed at the same distance from the transmitter coil, an identical voltage is induced in each of them. In order to receive an output signal that is zero when the system is in equilibrium, the first receiver coil is connected in series with the second receiver coil which has a reverse winding direction. With this the voltages induced in the receiver coils, which are of identical amplitude and reverse polarity, are canceling each other out in the case where the system, in the absence of metallic contamination, is in equilibrium.
    [0004] As a metal particle passes through the coil arrangement, the high frequency field is disturbed first near one receiver coil and then near the other receiver coil. As the metal particle is transported through the receiver coils the voltage induced in each receiver coil is changed (in nanovolts). This change in balance results in a signal at the output of the receiver coils that can be processed, amplified and subsequently used to detect the presence of metallic contamination.
    [0005] The signal processing channels divide the received signal into two separate components that are 90° apart from each other. The resulting vector has a magnitude and a phase angle, which is typical for products and contaminants that are transported through the coils. In order to identify a metallic contaminant, "product effects" need to be removed or reduced. If the product phase is known then the corresponding signal vector can be reduced. Eliminating unwanted signals from the signal spectrum thus leads to higher sensitivity to signals originating from contaminants.
    [0006] The methods applied to eliminate unwanted signals from the signal spectrum therefore exploit the fact that contaminants, product and other disturbances have different influences on the magnetic field so that the resulting signals differ in phase.
    [0007] The signals caused by various metals or products, as they pass through the coils of the metal detection system, can be divided into two components, namely resistive and reactive components, according to the conductivity and magnetic permeability of the measured object . The signal caused by ferrite is primarily reactive, whereas the stainless steel signal is primarily resistive. Products, which are conductive, typically cause signals with a strong resistive component.
    [0008] The distinction between the phases of the signal components of different origins through a phase detector allows to obtain information about the product and the contaminants. A phase detector, for example a frequency mixer or an analog multiplier circuit, generates a voltage signal which represents the difference in phase between the input signal, such as the signal from the receiver coils, and a reference signal provided. from the transmitting unit to the receiving unit. With this, by selecting the phase of the reference signal to coincide with the phase of the product signal component, a phase difference and a corresponding product signal are obtained at the output of the phase detector which is zero. In the case where the phase of the signal components originating from the contaminants differs from the phase of the product signal component, then the signal components of the contaminants can be detected. However in the case where the phase of the signal components of the contaminants is close to the phase of the product signal component, then the detection of contaminants fails, as the signal components of the contaminants are suppressed along with the product signal component. .
    [0009] In known systems the transmitter frequency is therefore selectable such that the phase of the signal components of the metallic contaminants will be out of phase with the product signal component.
    [00010] GB2423366A describes an apparatus that is arranged to switch between at least two different operating frequencies so that any metal particle in a product will be subject to scanning at different frequencies. The operating frequency is quickly changed so that any metal particle passing over a conveyor belt will be scanned at two or more different frequencies. In the case where for a first operating frequency the signal component caused by a metal particle is close to the phase of the product signal component and so is masked, then it is assumed that for a second frequency, the phase of the signal component caused by the metallic particle will differ from the phase of the product signal component so that these signal components can be distinguished. By switching between many frequencies, it is expected that one frequency will provide adequate sensitivity for any specific metal type, size and orientation.
    [00011] Observing this method from a different angle it can be stated that for an optimal frequency adjustment numerous other frequency adjustments have been applied, revealing that this method requires considerable effort. Multiple frequency adjustments need to be applied when measuring a single product. This means that for the frequency adjustment, which provides the best result, only a short measurement period is available. Consequently, the measurement result will not be optimal. Furthermore, as the measurement is performed for all selected frequency settings most of the data, which is processed with considerable effort, will be disregarded. With this, this method, which requires considerable efforts in the signal processing stages, is characterized by a relatively low efficiency.
    [00012] The present invention is therefore based on the object of providing an improved method for operating a metal detection system that uses at least two operating frequencies as well as on the object of providing a metal detection system that operates in accordance with this method.
    [00013] Specifically, the present invention is based on the object of providing a method that allows detecting contaminants, specifically metallic contaminants, with reduced efforts and a high efficiency.
    [00014] Still, the present invention is based on the object of providing a method that allows detecting small size metallic contaminants with a higher sensitivity.
    [00015] Furthermore, the present invention is based on the object of providing a method that provides information about the capacity of the metal detection system that can advantageously be used for the automatic configuration of the system. SUMMARY OF THE INVENTION
    [00016] The above and other objects of the present invention are achieved by an improved method for operating a metal detection system as defined in claim 1 and a metal detection system operating in accordance with this method as defined in claim 16.
    [00017] The inventive method serves to advantageously operate a metal detection system comprising a balanced coil system that has a transmitter coil that is connected to a transmitter unit, which provides transmitter signals with a selectable transmitter frequency, and with first and second receiver coils that provide output signals to a receiver unit, which compensate each other in the case where the metal detection system is in equilibrium and in the case where the product is present in the balanced coil, provide an output signal that is transferred to a signal processing unit, which suppresses at least the components of the product signal and supplies the signal components caused by the metallic contaminant contained in the product.
    [00018] The inventive method comprises the steps of determining the phase and magnitude of the signals relative to at least a first metallic contaminant for at least two transmitter frequencies and for at least two particle sizes of the first metallic contaminant; determining the phase and magnitude of the signal relative to a specific product for the at least two transmitter frequencies; compare the information established for the at least first metallic contaminant and the information established for the product; determining at least one preferred transmitter frequency at which the signal components of smaller particle sizes of the at least first contaminant differ most in phase and amplitude from the phase and amplitude of the product signal; and select the preferred transmitter frequency to measure the specific product.
    [00019] The inventive method therefore allows to obtain optimal transmitter frequencies with which the smallest possible particles of one or more types of metallic contaminant can be detected. Consequently the inventive metal detection system will be optimally configured for any measurement involving products of any consistency and any type of potential metallic contaminant.
    [00020] Measuring a product at inappropriate transmitter frequencies and analyzing the relative data is avoided. The inventive method always applies the optimal frequencies so that measurements are performed with reduced efforts and high efficiency. As measurements are not performed at inappropriate transmitter frequencies, the time available to measure a product, ie to detect metallic contaminants in a product, is devoted to applying an optimal transmitter frequency. As a result, more high-quality measurement data is available for an individual metallic contaminant. This consequently leads to a significant improvement in the sensitivity of the metal detection system for all measured metal contaminant types and products. Optimal transmitter frequencies are therefore determined for all types of metallic contaminant that may occur in a product and for all products available for all transmitter frequencies that can be selected.
    [00021] In a preferred embodiment at least two curves of a first network for at least a first metallic contaminant are established. Each curve is plotted for a separate transmitter frequency that represents the phase and magnitude of the signal for a progressively increasing particle size of the first metallic contaminant. With this, a response curve or location is established for at least the first metallic contaminant for at least two separate transmitter frequencies which are used as fixed parameters and with particle size as a variable parameter. Each curve established for a specific transmitter frequency is part of a first network that refers to the first metallic contaminant. For each metallic contaminant a first network with at least two curves is established.
    [00022] The information established for at least the first metallic contaminant and the information established for the product for at least a first and a second transmitter frequency are then compared in order to determine the preferred transmitter frequency, for which the components of Signal particles of smaller contaminant size differ more in phase and amplitude from the phase and amplitude of the product signal.
    [00023] In the case where information has been accumulated for each transmitter frequency for more than one metallic contaminant, then the complete information established for all metallic contaminant types for a first and a second transmitter frequency is compared with the information from the product set for this first and second transmitter frequencies.
    [00024] For this purpose, for each transmitter frequency a second network is constructed with curves of different types of metallic contaminant recorded with the same transmitter frequency. Then for a specific transmitter frequency an overlay of a second network and the product information is arranged, which allows to determine which parts of the curves fall within or outside the area or range of the product signals. The parts of the curves that fall outside the range of the product signs indicate the particle sizes of the metallic contaminant, which will not be masked or suppressed along with the product signs.
    [00025] With this, the inventive method and the metal detection system not only allow to determine the optimal transmitter frequency of a metallic contaminant but also allow to determine the minimum particle sizes of the types of metallic contaminant that can be detected. This valuable information can be used to configure the metal detection system more efficiently.
    [00026] The operator can enter the type of metallic contaminant to be detected. Based on this information provided by the operator, the computer program implemented in the metal detection system will often find a transmitter frequency that will be suitable for detecting two or more types of metallic contaminant. During the measurement process the metal detection system can therefore be configured and operated with one of at least two transmitter frequencies that preferably meets all requirements set by the operator.
    [00027] In the event that a single transmitter frequency does not satisfy the operator's requirements, then the computer program will select two or more transmitter frequencies that are optimal for the individual metallic contaminant types and that are applied during product measurement . The selected frequencies are then applied according to an appropriate method.
    [00028] The selected transmitter frequencies can be applied alternately or simultaneously, for example as a mixture of the selected transmitter frequencies, which are filtered accordingly in the receiver stage.
    [00029] With this, only optimal transmitter frequencies are applied that allow the measurement of metallic contaminants for the maximum available time so that the contaminants can be detected with the highest possible sensitivity.
    [00030] In a preferred embodiment the operating program is designed in such a way that the operator can enter the minimum particle sizes for the types of metallic contaminant that are to be detected. This allows the operating program to select a transmitter frequency that is suitable for two or more contaminant types for which the specified particle size can be detected.
    [00031] The required information of the types of metallic and product contaminants can be gathered in several ways. Information can be pre-stored and is downloaded. Alternatively, a calibration process can be performed for product and metallic contaminant types, in which, for example, a product and metallic contaminants of at least one particle size are measured.
    [00032] Product information can be obtained when scanning a product, for which typically several signal components occur that have an individual phase and magnitude. Connecting the vectors of all the signal components leads to an envelope that is the boundary of the area of the product signals or the product signature that will be suppressed by a signal discriminator, typically a signal processor that is programmed to suppress the components. of product sign. The area, in which product and contaminant signals are suppressed, is closely matched to the product signature but typically slightly larger, so that a margin of safety is provided. The product subscription changes from transmitter frequency to transmitter frequency. For a general product, an algorithm, based on empirical data, allows establishing the preferred product information based on only one measurement performed on a single transmitter frequency.
    [00033] During a factory setup period or before the start of a measurement process the metallic contaminant types data is gathered by measuring metallic particles with at least one particle size. Preferably, only one or a few points on the curve are measured, while the remainder of the curve is obtained by applying the empirical data that are typical for that metallic contaminant. In preferred embodiments, models or mathematical formulas are used to establish the curves or to interpolate the sections between two measured points. Thus, the calibration of the metal detection system requires only a few measurements that provide at least the starting points of the curves or the first and/or second networks.
    [00034] The information gathered is preferably stored in a memory of the control unit or a computer system that is attached or integrated with the metal detection system. The stored information can then be selectively downloaded and used for future calibration and configuration of the metal detection system. BRIEF DESCRIPTION OF THE DRAWINGS
    [00035] Some of the objects and advantages of the present invention have been presented, others will appear when the following description is considered together with the accompanying drawings, in which: Figure 1 shows a block diagram of an inventive metal detection system; and Figure 2 shows a transmission stage of the inventive metal detection system; Figure 3a shows an established response curve or location for a first metallic contaminant MC1 for a transmitter frequency fTX1 used as a fixed parameter and with the particle size as a variable parameter;Fig. 3b shows a first network of curves established for the first metallic contaminant MC1 for three different transmitter frequencies fTX1, fTX2, fTX3;Fig. 3c shows a second network of curves established for three different types of metallic contaminant MC1, MC2, MC3 for a transmitter frequency fTX1;Fig. 3d shows an APS area of the product signals for a scanned product with signal vectors of different phases and amplitudes that define the envelope of the APS area of the product signals and discriminator lines D that delimit the APS area of the product signals, which will be deleted;Fig. 3e shows an overlay of the second network of curves shown in Figure 3c and the APS area of the product signals shown in Figure 3d; and Figure 4 shows an illustration of the computer program 50 that is used to implement the inventive method. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES
    [00036] Figure 1 shows a block diagram of an inventive metal detection system, which comprises a transmitter unit 1, a balanced coil system 2 with a transmitter coil 21, a first and a second receiver coils 22, 23 , a receiver unit 3, a signal processing unit 4, and a control unit 5 comprising standard interfaces, input devices and output devices, specifically a monitor. Figure 1 further shows a conveyor 6, over which products P are transferred through the transmitting coil 21 and the receiving coils 22, 23.
    [00037] The transmitter unit 1, for which a preferred embodiment is shown in detail in Figure 2, provides a transmitter signal s1 to the transmitter coil 21 of the balanced coil system 2. In addition, the transmitter unit 1 provides a signal of reference s10 which has the transmitter frequency fTX to the receiver unit 3.
    [00038] The transmitter signal s1 induces the signals s22, s23 in the identical receiver coils 22, 23 which are of the same magnitude but of reverse polarity while the system is in equilibrium, that is, as long as the transported P products are not influencing the magnetic field themselves and are not contaminated with metals.
    [00039] In the case where a PC product is contaminated with an electroconductive object, then the signals s22, s23 on the identical receiver coils 22, 23 will change as the PC product passes through the balanced coil system 2. As a result the frequency of induced fTX transmitter in the receiver coils 22, 23 is modulated with a baseband signal, whose amplitude and frequency are dependent on the property, dimension and displacement speed of the electroconductive object.
    [00040] The output signals s22, and s23 of the receiver coils 22, 23 are applied to the central derived primary windings of a balanced transformer 31 that mirror the receiver coils 22, 23. Furthermore, the balanced transformer 31 comprises two central derived secondary windings identical tails whose opposite tails are connected to an amplifier 32. The outputs of the amplifier 32 are connected to a filter unit 33 which provides the amplified and filtered signals to a demodulation unit 34 which provides at its outputs the in-phase components of quadrature of the demodulated monitoring signal s30 and the in-phase and quadrature components of the baseband signal, which originates from the transported P products.
    [00041] The in-phase and quadrature signals provided at the outputs of the demodulation unit 34 are transferred to an additional filter unit 35, which allows the desired signals to pass through a gain unit 36 that allows to adjust the amplitudes of the signals. processed to a desired value. Subsequently the filtered and calibrated signals are converted in an analog to digital converter 37 from analog to digital form. The output signals from the analog to digital converter 37 are transferred to a signal processing unit, such as a known digital signal processor 4, which compares the demodulated and processed monitoring signals with reference values. The data resulting in the evaluation process is then transferred to a data processing unit such as the central processing unit of the metal detection system, an internal or external control unit such as a computer terminal 5.
    [00042] In order to control the measurement process the signal processor 4 or the control unit 5 is capable of controlling the functions of the various modules provided in the transmitting unit 1 and in the receiving unit 3. For this purpose, the signal processor 4 is transferring a first control signal c32 to the amplifier unit 32, a second control signal c33 to the first filter unit 33, a third control signal c35 to the second filter unit 35, a fourth control signal c36 to the gain unit 36 and a fifth control signal c37 to the analog to digital converter 37. With these control signals c32, c33, c35, c36 and c37 the amplification and filter characteristics in the individual receiver units 32, 33, 35, 36 and 37 can be selected or adjusted. A sixth control signal c12 is transferred to transmitter unit 1 as described below.
    [00043] Receiver stage 3 described above is, of course, a preferred embodiment. The inventive method however can be implemented in metal detection systems using differently structured receivers.
    [00044] Figure 2 shows a block diagram of transmitter unit 1 of the metal detection system shown in Figure 1.
    [00045] The transmitter unit 1 comprises a reference unit 11 which provides a reference signal s0 with a reference frequency fREF to a signal source 12, such as a frequency synthesizer 12 which is controlled by the sixth control signal c12 received from the signal processor 4 or control unit 5. Signal processor 4 can therefore select a suitable transmitter frequency fTX which is transferred with signal s10 to a power amplifier 13, which is providing the amplified transmitter signal s1 to the transmit coil 21 of the balanced coil system 2. The signal s10 is also transferred to a module 38 at the receiver stage 3 and provides in-phase and quadrature components of the reference signal s10 to the demodulation unit 34.
    [00046] The metal detection system described above allows to measure products and contaminants with the application of various fTX transmitter frequencies that are selected according to the inventive method. The inventive method is implemented by means of a computer program (see Figure 4) which is preferably stored in signal processor 4 or control unit 5. Computer program modules can also be implemented in distributed processors.
    [00047] Figure 3a shows an established response curve or location for a first metallic contaminant MC1 for a transmitter frequency fTX1, which is used as a fixed parameter, and with the particle size of the first metallic contaminant MC1 as a parameter variable. This curve can be obtained in several ways. With one method the operator sequentially transfers metallic particles of uniformly increasing sizes, eg 1mm, 2mm, 3mm, ..., through the balanced coil system 20 and records the relative signal vectors sv1, sv2, sv3. By connecting the endpoints of the signal vectors sv1, sv2, sv3 a program module builds the relative curve. In the case where only a small number of signal vectors sv1, sv2, sv3 were recorded, then the line sections between two points are obtained by interpolation. In the case where typical progression of such a curve or characteristics have been recorded for metallic contaminants MC, then it is sufficient to measure only one or two signal vectors sv1, sv2, and build the curve based on empirical values. In the event that the metal detection system has not changed its status and a calibration is not required, then the pre-stored curves for one or more metallic contaminant types MC1, MC2, MC3, ., potentials can be downloaded from memory.
    [00048] Figure 3b shows a first network of curves established for the first metallic contaminant MC1 for three different transmitter frequencies fTX1, fTX2, fTX3. The curves can again be obtained by measuring the signal vectors for different sizes of metallic contaminant MC1 for each of the frequencies fTX1, fTX2, fTX3. Alternatively, curves can be obtained by taking just one measurement, eg for a particle size of 2 mm at transmitter frequency fTX2 and applying the empirical data.
    [00049] Figure 3c shows a second network of curves established for three different types of metallic contaminant MC1, MC2, MC3 for a transmitter frequency fTX1. The curves were established as described above for Figures 3a and 3b.
    [00050] Figure 3d shows an APS area of the product signals that were taken while scanning a product P with transmitter frequency fTX1. Product signals are represented by signal vectors of different phases and amplitudes that define the envelope of the APS area of the product signals. Additionally shown are the discriminator lines D delimiting the APS area of the product signals, which will be suppressed or erased by the computer program 50 (see Figure 4) provided in the signal processing unit 4 and/or in the control unit 5 Typically, computer program modules 50 which are concerned with controlling the acquisition of calibration data are implemented in the control unit 5, while computer program modules 50 which are concerned with signal processing, specifically suppression of unwanted signals are implemented in signal processing unit 4.
    [00051] The APS area of the product signals is suppressed, for example, by adjusting the product phase until the discriminator lines D surround the measured product signal. Signals from metallic contaminants MC1, MC2, MC3, ..., which will extend beyond the D discriminator lines will then be detected, while the product signals will be suppressed. However, it is understood that there are other options to suppress unwanted signals. For example, received signals can be mapped into a two- or three-dimensional representation, in which areas or volumes are defined, which will be suppressed. Signals that fall within this area or volume will be disregarded.
    [00052] Figure 3e shows an overlay of the second network of curves shown in Figure 3c and the APS area of the product signals shown in Figure 3d. In this illustration it can be seen that only small sections of the curves of the first and second metallic contaminants MC1, MC2 fall within the APS area of the product signals. With this, for this fTX1 transmitter frequency the metal detector system is able to detect particles of the first and second metallic contaminants MC1, MC2 that are significantly smaller than 1 mm. However, it is shown that for the third metallic contaminant MC3 a large part of the curve, including the point referring to a particle size of 1 mm, falls within the APS area of the product signals.
    [00053] In Figure 3e the intersection points IPMC1, IPMC2, IPMC3 of the discriminator lines and the curves of the metallic contaminant types MC1, MC2, MC3, which forms a second network, are shown. These intersection points IPMC1, IPMC2, IPMC3 indicate particle sizes of metallic contaminant types MC1, MC2, MC3 that can no longer be measured. However, the comparison of the intersection points IPMC1, IPMC2, IPMC3 obtained with at least a first and a second transmitter frequencies fTX1, fTX2 allows to determine, with which transmitter frequency fTX1 or fTX2 smaller particle sizes of metallic contaminant types MC1 , MC2, MC3, of interest can be measured. Based on the collected data, as shown in Figure 3e, the computer program 50 can therefore decide which of the transmitter frequencies fTX1, fTX2, ... should be applied. In the given example the computer program 50 may decide that for metallic contaminant types MC1 and MC2 the first transmitter frequency fTX1 is suitable, while for the third metallic contaminant MC3 another transmitter frequency fTX-x may provide better results.
    [00054] In the case where the APS area of the product signals was precisely mapped, then the intersection points of the boundary of the APS area of the product signals and the curves of the metallic contaminant types MC1, MC2, MC3, which form a second network can be determined.
    [00055] When scanning a P product the computer program 50 can alternately or simultaneously apply the selected fTX1 and fTX-x transmitter frequencies. In the case where transmitter frequencies fTX1 and fTX-x are applied alternately then the application sequence is preferably selected or selectable according to one or more process parameters. The number of alternations will typically depend on the size of the P products and the types of metallic contaminant MC and can be freely selected. Typically, the number of alternations is selected in the range between 1 and 50.
    [00056] In the case where the first of two metallic contaminants MC1, MC2 would provide a strong signal and the second would provide a small signal, then the active cycles with which the transmitter frequencies fTX1 and fTX-x are applied can advantageously be adapted . The optimized fTX transmitter frequency application time for the second metallic contaminant MC2 will typically be by a factor in the range of 2 to 10 higher than the application time of the fTX transmitter frequency that has been selected for the first metallic contaminant MC1.
    [00057] The inventive method therefore allows to start the measurement processes, that is, the process of scanning the products P transported with the transmitter frequencies fTX1 and fTX-x preferred or optimized. With this, the time that is available for the measurement, when the product P is passing through the balanced coil system 2, is fully utilized by the application of the most preferable fTX transmitter frequencies. All data collected therefore contributes to the final measurement results. With this, due to the application of optimized fTX transmitter frequencies for a longer period of time, the resulting sensitivity for the detection of metallic contaminants MC increases significantly. Furthermore, although at least for the initial setup of the metal detection system, additional efforts are required, the total efforts of operating the metal detection system are significantly reduced. A process for analyzing, evaluating and selecting data is no longer required.
    [00058] Furthermore, the inventive method constitutes an important improvement for the simultaneous application of more than one transmitter frequency fTX. Based on the calibration process described above only a few fTX transmitter frequencies will be required to perform an optimized measurement. Consequently efforts to separate the reduced number of fTX transmitter frequencies, for example, by means of filter techniques implemented in signal processor 4 or by means of switched filterbanks 33 (see Figure 1), will be relatively low compared to the known systems.
    [00059] Figure 4 shows an illustration of a preferred embodiment of the computer program 50 that is used to implement the inventive method. The computer program 50 comprises four essential modules 51, 52, 53 and 54.
    [00060] The first program module 51 serves to establish the data of metallic contaminants MC that possibly appear in the P products. More specifically, the first program module 51 serves to establish the first and/or second networks of discussed curves shown in the Figures 3b and 3c. For this purpose the first program module 51 accesses data file 553, in which the available transmitter frequencies fTX1, fTX2, fTX3, fTX4, ... , are listed which serve as variable parameters for the first networks and as fixed parameters for the second networks. The number of fTX transmitter frequencies is typically in the range between six and twenty, but can be freely selected. The first program module 51 can access data files 5511, 5512, . additional. In data file 5511 empirical data of MC metallic contaminants are listed. Data file 5512 preferably contains pre-recorded curves and/or first and/or second networks of metallic contaminants MC. In the case where at least one calibration process for a metallic contaminant MC1 is performed, with a particle size and a transmitter frequency fTX1, then the relative data is transferred to the first program module 51 via the data bus 5513. Established data, such as a plurality of first and second networks, are transferred in data files 510 to the third program module 53.
    [00061] The second program module 52 serves to establish the data of at least one product P for the transmitter frequencies fTX1, fTX2, fTX3, fTX4, . selectable. The second program module 52 can access data files 5521, 5522, .. Data file 5521 contains empirical data of P products. Data file 5522 preferably contains pre-recorded data of P products of interest. In the case where at least one calibration process with a product P is performed, then the relative data is transferred to the second program module 52 via data bus 5523. The data set such as a plurality of APS areas, each set to a transmitter frequency ÍTXI; fTX2; fTX3; f™; ..., are transferred in data files 520 to the third program module 53.
    [00062] Selectively using data files 5511, 5512, .; 5521, 5522, . and/or concurrent data from calibration processes the data required for the comparison processes, i.e. the evaluation of the results of applying the transmitter frequency fTx1; fTx2; fTx3; fTx4 can be set in various modes.
    [00063] In the third program module 53 the data established for the product P and the contaminants MC are compared for each transmitter frequency fTx1; fTx2; fTx3; fTx4; .. As symbolically shown in Figure 4, the data overlaps of product P and two contaminants MC1, MC2 are established for a first and a second transmitter frequency fTx1; fTx2. Then it is determined, with which transmitter frequency fTx1; fTx2 the smallest particle sizes of MC1, MC2 contaminants can be detected. This process is preferably carried out for all transmitter frequencies fTx1, fTx2, fTx3, fTx4, . selectable.
    [00064] Finally, the results of the third program module 53 are transferred to the fourth program module 54 which controls and coordinates the individual processes, preferably including the measurement calibration processes. Specifically, transmitter frequencies fTx1; fTx2; fTx3; fTx4; . and the minimum particle sizes of metallic contaminant types MC1, MC2, . that can be detected with these are reported to the fourth program module 54. Depending on the configuration parameters selected by the operator, for example, at a data terminal 5, the fourth program module 54 is configuring the measurement process and transfers the control signals relative to the individual electronic modules of the metal detection system. Specifically, the fourth program module 54 starts sending the control signal c12 to the transmitter unit 1. Furthermore, the status of the measurement process can be continuously observed by electronic sensors, preferably optical sensors that provide signals to the fourth module. of program 54 allowing timed executed measurement sequences.
    [00065] The fourth program module 54 preferably comprises data storage units, such as data files 541, 542, in which at least the results of the calibration processes are stored. In data file 541 the results of the calibration processes, specifically the minimum particle sizes of metallic contaminant types MC1, MC2, ... and the relative transmitter frequencies fTX1, fTX2, fTX3, fTX4, are stored. In data file 542 configuration data for various measurement processes can be stored for repeated use.
    [00066] The fourth program module 54 preferably also communicates with the signal processor 4, the control unit 5 and other devices that are contained in, for example, a computer terminal.
    [00067] During the operation of the metal detection system the fourth program module 54 preferably collects additional data derived from the product P and the metallic contaminants MC in order to maintain optimal conditions with a calibration process running in parallel with the process of measurement.
    [00068] For the operation of the metal detection system it would be desirable to reduce the number of transmitter frequencies fTX1, fTX2, so that not for each individual product a specific frequency needs to be selected.
    [00069] According to the invention different products are assigned to groupings that are each assigned to an optimized fTX transmitter frequency. Grouping the products therefore allows to obtain improved measurement results with high efficiency.
    [00070] The grouping process can be performed in various modes. Preferably the product information is further obtained for all available fTX transmitter frequencies. As shown above, when scanning a product, typically several signal components occur each having an individual phase and magnitude. Connecting the vectors of all signal components leads to an envelope which is the boundary of the APS area of the product signals or the product signature that will be suppressed by the signal discriminator.
    [00071] Figure 3d shows an APS area of the product signals that were taken while scanning a product P with transmitter frequency fTX1. Product signals are represented by signal vectors of different phases and amplitudes that define the envelope of the APS area of the product signals. Also shown are the D discriminator lines that delimit the APS area of the product signals, which will be suppressed.
    [00072] According to the invention products with similar or equivalent APS signatures are grouped and assigned to an optimized fTX transmitter frequency. For this group or grouping the discriminator lines D are then fitted, which ensures that each APS product signature is suppressed when the corresponding product is passing through the detector.
    [00073] Alternatively, products with D discriminator lines that fall within a selected range are grouped to an optimized fTX transmitter frequency.
    [00074] As a further alternative, D discriminator lines can be defined, based on which stored APS product signatures or stored D discriminator lines are retrieved, which lie between said D discriminator lines. The operator can therefore select the acceptable particle sizes of metallic contaminant types MC1, MC2, MC3 and corresponding D discriminator lines. For these lines of discriminator D the implemented computer program 50 will list all products that can be grouped for individual transmitter frequencies fTX1, fTX2, ....
    [00075] In an additional preferred mode, the operator can select a first product P that needs to be measured. The computer program 50 can then analyze whether additional P products exist, preferably within a selected tolerance range which can be grouped together with the first product.
    [00076] The reduced set of transmitter frequencies fTX1, fTX2, ., preferably consists of transmitter frequencies fTX1, fTX2, ., which are selected in such a way that cluster sizes are obtained containing a maximum number of products.
    [00077] With this grouping process, which can be performed with the computer program 50 based on product data stored in the database 5, the efficiency of the metal detection system can be significantly increased.
    权利要求:
    Claims (16)
    [0001]
    1. Method for operating a metal detection system comprising a balanced coil system (2) with a transmitter coil (21) that is connected to a transmitter unit (1) which provides transmitter signals (s1) that have a selectable transmitter frequency (fTX), and with first and second receiver coils (22, 23) providing output signals (s22, s23) to a receiver unit (3), which compensate each other in the case in that the metal detection system is in equilibrium and, in the case where the product is present in the balanced coil system (2), they provide an output signal that is transferred to a signal processing unit, which suppresses at least the product signal components and provides the signal components caused by metallic contaminants (MC1, MC2, ...) contained in the product, characterized by the fact that it comprises the following steps: a) determining the phase and magnitude of the relative signals for one or more contaminants me thallics (MC1; MC2; ...) for each of at least two transmitter frequencies and for at least two metallic contaminant particle sizes (MC1, ...); b) determine the phase and magnitude of the signal relative to a product (P) specific for the at least two transmitter frequencies (fTX1, fTX2); c) compare the information established for the one or more metallic contaminants (MC1; MC2; ...) and the information established for the product (P) for the skin minus two transmitter frequencies; d) determine a preferable transmitter frequency with which the smallest particle size signal components of the one or more contaminants (MC1; MC2; ...) differ most in phase and amplitude from phase and amplitude of the product sign; ee) select the preferred transmitter frequency to measure the product (P) specific for each type of metallic contaminant (MC1; MC2; ...); and f1) apply the selected transmitter frequencies alternately and filter them accordingly in the receiving unit (3); orf2) apply the selected transmitter frequencies simultaneously and filter them accordingly in the receiving unit (3).
    [0002]
    2. Method according to claim 1, characterized in that it comprises the following steps: a) establishing at least a first and a second curve of a first network at least for a first metallic contaminant (MC1, ...), each curve representing the phase and magnitude of the signal for a progressively increasing particle size of the first metallic contaminant (MC1, ...) for one of the selectable transmitter frequencies; and b) compare the information established for at least the first metallic contaminant (MC1, ...) and the information established for the product (P) for each transmitter frequency in order to determine the preferred transmitter frequency, for which the components of Signal particles of smaller contaminant size differ more in phase and amplitude from the phase and amplitude of product signals.
    [0003]
    3. Method according to claim 1 or 2, characterized by the fact that information, preferably the first network of curves, is established for at least the first and second metallic contaminant (MC1, MC2, ...), and where the curves that have been established for the same transmitter frequency for different types of metallic contaminant (MC1, MC2, ...) are combined for a second network.
    [0004]
    4. Method according to any one of claims 1 to 3, characterized in that for each metallic contaminant (MC1; MC2; ...) the preferred transmitter frequency is determined in such a way that the transmitter frequency (fTX ) selected is optimal for one or more of the metallic contaminant types (MC1; MC2; ...).
    [0005]
    5. Method according to claim 3 or 4, characterized in that the minimum particle size values are determined for each metallic contaminant (MC1; MC2; ...) and in that these values are transferred to a module of a computer program that selects one or more optimal transmitter frequencies (fTX) or where the values are transferred to an output module of a computer program that provides preference status information in a table.
    [0006]
    6. Method according to any one of claims 2 to 5, characterized in that a) each curve for at least the first metallic contaminant (MC1, ...) for the first and second transmitter frequency is established by measuring the phase and magnitude for different particle sizes of the metallic contaminant (MC1, ...) and determining the desired curve based on the resulting signal vectors by extrapolation, or b) each curve for at least the first metallic contaminant (MC1, . ..) for the first and second transmitter frequency is established by measuring the phase and magnitude for only one particle size of the metallic contaminant (MC1, ...) and determining the desired curve based on empirical data and/or a mathematical model adapted for the metallic contaminant (MC1, ...) relative.
    [0007]
    7. Method according to claim 6, characterized in that the mathematical model is preferably provided for each type of metallic contaminant (MC1; MC2; ...) with which, starting from at least one signal vector, the curves of the first and/or second networks are calculated for each metallic contaminant (MC1; MC2; ...).
    [0008]
    8. Method according to any one of claims 1 to 7, characterized in that the step of establishing the information for the product (P) for at least a first and a second transmitter frequency includes the detection of various components of the product signals that have different phases and magnitudes defining an area (APS) of the product signals.
    [0009]
    9. Method according to claim 8, characterized in that the signals that occur within the area (APS) of the product signals or within discriminator lines (D) that delimit the area (APS) of the product signals are suppressed for the selected transmitter frequency (fTX).
    [0010]
    10. Method according to claim 8 or 9, characterized in that at least for a first and a second transmitter frequency the points of intersection (IPMC1, IPMC2, IPMC3) relative on the one hand to the area boundary ( APS) of the product signals or the discriminator lines delimiting the area (APS) of the product signals and on the other hand the curves of the first or second network are determined and where the intersection points (IPMC1, IPMC2, IPMC3) are determined for the different transmitter frequencies are compared in order to determine the preferred transmitter frequency for one, each or a combination of metallic contaminant types (MC1; MC2; ...).
    [0011]
    11. Method according to any one of claims 8 to 10, characterized in that the discriminator lines (D) are individually selected for each transmitter frequency (fTX).
    [0012]
    12. Method according to any one of claims 1 to 11, characterized in that the information established for the types of metallic contaminant (MC1; MC2; ...) and the information established for the products (P) that are stored in a memory unit of the metal detection system and are downloaded whenever the metal detection system is configured for a new measurement process or where the required information for metallic contaminant types (MC1; MC2; ... ) and for product (P) are established whenever the metal detection system is configured for a new measurement process.
    [0013]
    13. Method according to any one of claims 1 to 12, characterized in that at least one grouping with products (P) is formed which a) displays product areas (APS) with a predetermined maximum deviation and for which the lines of discriminator (D) are determined; or b) displays product areas (APS) that fall between predetermined discriminator lines (D).
    [0014]
    14. Method according to any one of claims 1 to 13, characterized in that two or more groupings with products (P) are defined which are assigned to a reduced set of transmitter frequencies.
    [0015]
    A metal detection system operating in accordance with a method as defined in any one of claims 1 to 14, comprising a balanced coil system (2) with a transmitter coil (21) that is connected to a transmitter unit ( 1), which provides transmitter signals (s1) that have a selectable transmitter frequency (fTX), and with first and second receiver coils (22, 23) that provide output signals (s22, s23) to a unit receiver (3), which compensate each other in the case where the metal detection system is in equilibrium and, in the case where the product (P) is present in the balanced coil system (2), it provides a signal of output which is transferred to a signal processing unit, which suppresses at least the components of the product signal and supplies the signal components caused by metallic contaminants (MC1, MC2, ...) contained in the product (P), characterized by the fact that a control unit is provided with a computer program that is designed: a) ) to determine the phase and magnitude of related signals for one or more metallic contaminants (MC1; MC2; ...) for each of at least two frequencies and for at least two particle sizes of the metallic contaminant (MC1, ...); and b) ) to determine the phase of magnitude of the signal related to a specific product (P) for the at least two transmitter frequencies; and c) to compare the established information for one or more metallic contaminants (MC1; MC2; ...) for at least two transmitter frequencies (fTX) and the established product information (P) for the at least two transmitter frequencies (fTX); and d) to determine a preferable transmitter frequency (fTX) with which the signal components of smaller particles of the one or more contaminants (MC1; MC2; ...) differ most in phase and amplitude from the phase and amplitude of the signal of product; ee) to select the preferred transmitter frequency (fTX) to measure the specific product (P) for each metallic contaminant (MC1; MC2; ...); and f1) to alternately apply selected transmitter frequencies and to filter them accordingly in the receiving unit (3); or (f2) to simultaneously apply the selected transmitter frequencies and filter them accordingly in the receiving unit (3).
    [0016]
    16. Metal detection system according to claim 15, characterized in that the computer program, which preferably is implementing a mathematical model, is designed) to establish a first network consisting of at least two curves by the minus for the at least first metallic contaminant (MC1, ...), each curve, which is established for a transmitter frequency (fTX), representing the phase and magnitude of the signal for a progressively increasing particle size of the first metallic contaminant (MC1, ...); and b) to compare the information established for at least the first metallic contaminant (MC1, ...) and the information established for the product (P) in order to determine the preferred transmitter frequency (fTX) for which the signal components of smaller sized contaminant particles differ more in phase and amplitude from the phase and amplitude of the product signal
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    法律状态:
    2018-12-26| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2020-03-03| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2021-04-06| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-06-01| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 21/09/2011, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    EP10186895.8|2010-10-07|
    EP10186895|2010-10-07|
    PCT/EP2011/066395|WO2012045578A1|2010-10-07|2011-09-21|Method for operating a metal detection system and metal detection system|
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