Signal conditioning circuit and electromagnetic inductive encoder

Abstract

The present disclosure relates to a signal conditioning circuit and an electromagnetic induction encoder, the signal conditioning circuit comprising: a voltage pickup circuit comprising: a capacitive element connected in parallel with an induction coil and constituting a resonant network to amplify the amplitude of a voltage signal collected from the induction coil; a detection circuit comprising: a reference signal terminal, a signal output terminal and a switching switch unit; the switching switch unit is connected across the induction coil and is used to switch the connection of the reference signal terminal and the signal output terminal across the two terminals of the coil circuit; a filter circuit coupled to the latter stage of the detection circuit, and the output terminal of the filter circuit leads to the output terminal of the signal conditioning circuit. By constructing a resonant network with the capacitive voltage pickup circuit and the induction coil, the amplification of the picked-up voltage can be realized, and the demodulation is completed by cooperating with the detection circuit with corresponding structural changes, and the signal amplification circuit is omitted, thereby simplifying the structure, volume, cost and reducing the power consumption, and the advantages are particularly prominent in high-precision multi-code channel encoders.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of encoder measurement, and in particular to a signal conditioning circuit and an electromagnetic induction type encoder. BACKGROUND

[0002] The electromagnetic induction type encoder is a non-contact sensor based on the principle of electromagnetic induction, which is widely used in high-precision position detection and precision control fields. The principle of the electromagnetic induction type encoder is that the stator integrates a transmitting coil and an induction coil, and the rotor carries a magnetic material to rotate with the measured object, which changes the magnetic field distribution around the stator coil, thereby generating a pickup voltage in the induction coil. Through the signal conditioning circuit, the pickup voltage signal is collected, and after demodulation and filtering, it is output to the backend for analog-to-digital conversion and calculation to obtain the measured quantity (such as displacement, angle, etc.).

[0003] At present, the pickup voltage signal in the electromagnetic induction type encoder is usually collected by a resistive pickup circuit, and after demodulation, it needs to be amplified to a suitable signal amplitude by a signal amplification circuit based on a high-precision operational amplifier before being output to the backend. Because there are usually multiple induction coils in the electromagnetic induction type encoder, such as at least a pair of orthogonal induction coils (a pair of Sin coils and Cos coils) for an incremental electromagnetic induction type encoder to obtain a single code channel measured quantity, i.e. 2 signal conditioning circuits are needed. An absolute electromagnetic induction type encoder needs at least two code channels to calculate the absolute measured result, i.e. 4 signal conditioning circuits are needed. With the increasing demand for precision, the number of code channels increases, and the number of induction coils and corresponding signal conditioning circuits also increases, such as 6, 8, 12 or more code channels, and the number of induction coils and signal conditioning circuits is twice as many. As can be seen, with the increase in the number of circuits, the number of circuit devices also increases, the circuit board complexity is high, the power consumption is high, and the cost is also high. It is more difficult to realize the miniaturization of the encoder. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a signal conditioning circuit and an electromagnetic induction type encoder, which effectively solve the problems in the related art.

[0005] The first aspect of the present disclosure provides a signal conditioning circuit applied to an electromagnetic induction type encoder comprising an induction coil, comprising: a voltage pickup circuit comprising a capacitive element connected in parallel with the induction coil and constituting a first resonant network to amplify the amplitude of a voltage signal collected from the induction coil; wherein the resonant frequency of the first resonant network matches the frequency of the pickup voltage of the induction coil and the frequency of an excitation signal of a transmitting coil in the electromagnetic induction type encoder; a detection circuit comprising a reference signal end, a signal output end and a switching switch unit; wherein the reference signal end is applied with a reference voltage; the switching switch unit is connected to both ends of the induction coil and is used to switch the connection state to exchange the connection of the reference signal end and the signal output end with both ends of the induction coil; a filter circuit coupled to the rear stage of the detection circuit, and the output end of the filter circuit leads to the output end of the signal conditioning circuit.

[0006] In an embodiment of the first aspect, the switching switch unit comprises a double-pole four-throw switch comprising a first static contact and a second static contact respectively coupled to both ends of the induction coil; a first moving contact and a second moving contact respectively coupled to the first static contact and the second static contact; the first moving contact and the second moving contact are respectively coupled to one of the reference signal end and the signal output end; wherein the double-pole four-throw switch has a switch control end for receiving a switch control signal and switches the coupling object of the first moving contact and the second moving contact in response to the switch control signal.

[0007] In an embodiment of the first aspect, the switching switch unit comprises two single-pole double-throw switches arranged to change the switching state synchronously.

[0008] In an embodiment of the first aspect, the capacitive element comprises a variable capacitor; and / or, in an embodiment of the first aspect, the capacitive element comprises a plurality of capacitive devices connected in parallel.

[0009] In an embodiment of the first aspect, the filter circuit comprises an RC filter.

[0010] In an embodiment of the first aspect, the transmitting coil is connected in parallel with a second capacitive element to constitute a second resonant network having the same resonant frequency as the first resonant network, and the first resonant network and the second resonant network produce a common amplification effect on the amplitude of the voltage signal on the induction coil; and / or, when the magnetic marker in the rotor of the electromagnetic induction type encoder that induces the magnetic field generated by the excitation signal is implemented as a coil, the magnetic marker is connected in parallel with a third capacitive element to constitute a third resonant network having the same resonant frequency as the first resonant network; wherein the first resonant network, the second resonant network and the third resonant network produce a common amplification effect on the amplitude of the voltage signal on the induction coil.

[0011] The second aspect of the present disclosure provides an electromagnetic induction encoder, comprising: a stator, comprising: at least one transmitting coil; at least one induction coil group, comprising a pair of induction coils arranged with a preset phase difference; circuitry, comprising: at least two signal conditioning circuits according to any one of the first aspect, each corresponding to one of the induction coils; and a signal processing unit coupled to the output of the signal conditioning circuit.

[0012] In an embodiment of the second aspect, the transmitting coil is connected in parallel with a second capacitive element to form a second resonant network having the same resonant frequency as the first resonant network, the first resonant network and the second resonant network jointly amplifying the amplitude of the voltage signal on the induction coil; the magnetic marker is implemented as a coil connected in parallel with a third capacitive element to form a third resonant network having the same resonant frequency as the first resonant network, the first resonant network, the second resonant network and the third resonant network jointly amplifying the amplitude of the voltage signal on the induction coil.

[0013] In an embodiment of the second aspect, the electromagnetic induction encoder is implemented as an absolute electromagnetic induction encoder, comprising: at least two induction coil groups and a corresponding number of signal conditioning circuits.

[0014] In an embodiment of the second aspect, the electromagnetic induction encoder is implemented as an incremental electromagnetic induction encoder, comprising: at least one induction coil group and a corresponding number of signal conditioning circuits.

[0015] In an embodiment of the second aspect, each of the pair of induction coils arranged with a preset phase difference comprises a pair of differential sub-coils connected in series.

[0016] As described above, the present disclosure relates to a signal conditioning circuit and an electromagnetic induction type encoder, the signal conditioning circuit comprising: a voltage pickup circuit comprising: a capacitive element connected in parallel with the induction coil and constituting a first resonant network to amplify the amplitude of the voltage signal collected from the induction coil; wherein the resonant frequency of the first resonant network matches the frequency of the pickup voltage of the induction coil and the frequency of the excitation signal of the transmitting coil in the electromagnetic induction type encoder; a detection circuit comprising: a reference signal end, a signal output end and a switching switch unit; wherein the reference signal end is applied with a reference voltage; the switching switch unit is connected to both ends of the induction coil and is used to switch the switching state to exchange the connection of the reference signal end and the signal output end with both ends of the induction coil; a filter circuit coupled to the rear stage of the detection circuit, and the output end of the filter circuit leads to the output end of the signal conditioning circuit. By constructing a resonant network with the capacitive voltage pickup circuit and the induction coil, the amplification of the pickup voltage can be realized, and the demodulation is completed by cooperating with the detection circuit with corresponding structural changes, and the signal amplification circuit is omitted, thereby simplifying the structure, volume, cost and reducing the power consumption, and the advantages are particularly prominent in the encoder with high precision and multiple code channels. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A structural schematic diagram of an electromagnetic induction type encoder in the related art is shown.

[0018] Figure 2 A structural schematic diagram of a signal circuit in the related art is shown.

[0019] Figure 3 And Figure 4 A schematic diagram of a single-pole double-throw switch switching different signal flow directions in Figure 2

[0020] Figure 5 A schematic diagram of a signal waveform after shaping in the related art is shown.

[0021] Figure 6 A structural schematic diagram of a signal conditioning circuit in an embodiment of the present disclosure is shown.

[0022] Figure 7 And Figure 8 A schematic diagram of the signal flow direction switched by the switching switch unit in an embodiment of the present disclosure is shown.

[0023] Figure 9 A structural schematic diagram of an electromagnetic induction type encoder in an embodiment of the present disclosure is shown.

[0024] Figure 10 A schematic diagram of the transmitting coil, the magnetic marker and the induction coil respectively constituting LC resonant networks to collectively amplify the signal in an embodiment of the present disclosure is shown. ​

[0025] Figure 11 Figure 1 shows a schematic diagram of a signal amplification system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] The embodiments of the present disclosure will be described in detail with specific examples in the following. Other advantages and effects of the present disclosure can be easily understood by those skilled in the art from the messages disclosed in the present disclosure. The present disclosure can also be implemented or applied by other different embodiments or modules, and the details in the present disclosure can be modified or changed in various ways without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0027] The embodiments of the present disclosure will be described in detail with specific examples in the following. Other advantages and effects of the present disclosure can be easily understood by those skilled in the art from the messages disclosed in the present disclosure. The present disclosure can also be implemented or applied by other different embodiments or modules, and the details in the present disclosure can be modified or changed in various ways without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0028] In the present disclosure, the expressions of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics represented in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics represented can be combined in any one or a group of embodiments or examples in a suitable manner. In addition, the different embodiments or examples represented in the present disclosure and the features of the different embodiments or examples can be combined and combined by those skilled in the art without conflict.

[0029] In addition, the terms "first", "second" are only used for the purpose of representation, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the present disclosure, the meaning of "a group" is two or more, unless otherwise specifically limited.

[0030] In order to clearly illustrate the present disclosure, the devices irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar constituent elements throughout the description.

[0031] Throughout this specification, when it is said that a device is "connected" to another device, this includes not only "direct connection" but also "indirect connection" by placing other components in between. Furthermore, when it is said that a device "comprises" a certain constituent element, unless otherwise stated otherwise, this does not exclude other constituent elements, but rather implies that other constituent elements may be included.

[0032] While the terms first, second, etc., are used in some examples herein to refer to various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, first interface and second interface, etc., are used. Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of the stated feature, step, operation, element, module, item, kind, and / or group, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, modules, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition will only occur if the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way.

[0033] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the scope of this disclosure. The singular form used herein includes the plural form unless the statement explicitly indicates otherwise. The word "comprising" as used in this specification means to specify a particular characteristic, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0034] Although not explicitly defined, all terms, including technical and scientific terms used herein, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries shall be further interpreted as having a meaning consistent with the relevant technical literature and the message of the present disclosure, and shall not be over-interpreted as having an ideal or overly formulaic meaning unless otherwise defined.

[0035] Let me first briefly introduce the principle of electromagnetic induction encoders.

[0036] like Figure 1 The diagram shows a structural schematic of an electromagnetic induction encoder in the related art.

[0037] existFigure 1 In some embodiments, the electromagnetic inductive encoder comprises a moving part (mover) and a stationary part (stator).

[0038] In some embodiments, the mover can be arranged on the measured object to move with the measured object, such as being mounted on a motor to move with the motor. The mover can be provided with a magnetic target, such as a coil or a metal conductor.

[0039] The stator comprises at least one transmitting coil J and at least one pair of sensing coils arranged at a spatial angle offset, which are denoted as sensing coil A and sensing coil B in the figure. The transmitting coil J is connected to an alternating signal to generate a periodically changing magnetic field in space. When the magnetic target moves in the magnetic field, it modulates the distribution of the magnetic field, and in turn changes the magnetic flux of the sensing coils, to generate a pickup voltage in each sensing coil A and B. Each sensing coil A and B is connected to a signal circuit X, which collects the pickup voltage on the sensing coil to form an output signal. The output signal is a sinusoidal wave. A pair of sensing coils are usually arranged at a spatial angle offset. For example, corresponding to an angle to be measured, a pair of sensing coils can be arranged orthogonally. In some examples, a pair of sensing coils can be implemented as a periodically changing pattern with the same shape and size arranged coaxially along the circumference, such as a sine wave, a sawtooth wave, etc., and the spatial angle offset of the two patterns can be 90° to achieve orthogonality.

[0040] It can be understood that there is a corresponding phase difference between the pickup voltages on the sensing coil A and the second sensing coil B arranged at a spatial angle offset. For example, there is a 90° phase difference between the pickup voltages on a pair of sensing coils arranged orthogonally.

[0041] Specifically, the pickup voltage V in the sensing coil is related to the rate of change of the magnetic flux Φ passing through the coil with respect to time t, which is expressed as:

[0042] ;

[0043] Where N is the number of turns of the coil.

[0044] The magnetic flux Φ depends on the magnetic field strength B and the effective area A of the sensing coil. Then, we can get:

[0045] Φ=B·A·cosα; α is the angle between the magnetic field and the normal direction of the sensing coil. The normal direction of the sensing coil and the magnetic field can be arranged at a preset angle, and the angle between the normal direction and the magnetic field is 0°, and cos0°=1.

[0046] The magnetic field strength B varies with the motion amount of the magnetic target. For example, for the measured angle, the magnetic field strength B varies with the rotation angle θ of the magnetic target, expressed as B = B0 sin θ. Wherein, the inductive coil A is used to induce the sinusoidal varying magnetic field signal generated when the rotor rotates. It is called as sin inductive coil. When the rotor rotates, the relative position of the magnetic mark and the sin inductive coil changes, resulting in the change of the magnetic flux passing through the coil, and further generating an induced electromotive force in the coil, the size and phase of the induced electromotive force are related to the position of the rotor. Then, B = B0 sin θ can be expressed as: Φ = B0 A sin θ; θ is the rotation angle of the magnetic target. Then, the pickup voltage of the first inductive coil can be expressed as V sin = V sin θ.

[0047] The inductive coil B is a cos inductive coil cooperating with the sin inductive coil, and the signals output by the two exist a phase difference of 90°, which is used to induce the cosine varying magnetic field signal generated when the rotor rotates. Similarly, the magnetic flux of the inductive coil B is expressed as Φ = B0 A cos θ; then, the pickup voltage of the inductive coil B can be expressed as V cos = V cos θ.

[0048] By solving θ = arctan (V sin / V cos ), θ can be solved. Thus, by the sin inductive coil and the cos inductive coil, the magnetic flux change caused by the rotor motion is induced, that is, the different signal amplitude changes corresponding to the different magnetic flux changes caused by the motion of the measured object to different positions, so as to calculate the angle information of the position reached by the measured object.

[0049] It is worth mentioning that the above pair of sin and cos induction coils realizes the calculation of the angle information in one "code track", and the obtained angle information is a kind of "incremental angle information". Therefore, on the basis of a marker (which can be a unique structure) capable of determining the starting / reference position, the incremental electromagnetic induction type encoder can obtain the actual angle position of the measured object by accumulating each incremental angle information. Therefore, the incremental electromagnetic induction type encoder can only need a single code track, that is, to arrange a pair of sin and cos induction coils, and a corresponding pair of signal circuits X, that is, two signal circuits X. The absolute electromagnetic induction type encoder needs two or more code tracks. As an example, two or more code tracks include a coarse code track and a fine code track, each corresponding to a pair of induction coils. The coarse code track and the fine code track correspond to the coarse and fine accuracy angle information, such as the high and low bit information of the angle. Therefore, the winding pattern of the pair of induction coils corresponding to the fine code track is higher than that of the pair of induction coils corresponding to the coarse code track. Two code tracks correspond to two pairs of induction coils, that is, four induction coils, and four signal circuits X are needed. In the scene where the measurement accuracy is higher, the code track can be 6, 8, 12, and the corresponding induction coils and signal circuits X are 12, 16 and 24. That is, the higher the accuracy, the higher the circuit device and layout complexity.

[0050] As shown in Figure 2 , a structure schematic diagram of a signal circuit in the related art is shown.

[0051] In Figure 2 , the coil equivalent circuit of the induction coil can be equivalent to a series inductance L and resistance R. To represent the uniformity of the resistance, there are two resistances R, and the inductance L is connected in series between the two resistances R. The signal conditioning circuit includes a resistance voltage acquisition circuit, which exemplarily includes resistances R1 and R2. One end of the resistances R1 and R2 is connected to the two ends of the inductance L, respectively, and the other end of the resistances R1 and R2 is commonly connected and leads out a reference signal end for applying a constant reference voltage V R . Assuming that the original amplitude of the pickup voltage obtained by the induction coil sensing the change of the magnetic flux is V1, V R can be superimposed on the pickup voltage V1 to obtain the voltage signal V2=V1+V RThis avoids the small pickup voltage being overwhelmed by noise and also facilitates subsequent analog-to-digital converter calculations. The signal conditioning circuit includes a shaping circuit located after the resistive voltage acquisition circuit. The shaping circuit includes a single-pole double-throw switch, whose two stationary contacts are respectively coupled to the common terminals of the resistive voltage acquisition circuit and the coil equivalent circuit. The signal circuit includes an amplification circuit located after the shaping circuit. The amplification circuit can be built based on a high-precision operational amplifier. For example, operational amplifier U can be constructed as a differential amplifier circuit by connecting resistors R3, R4, etc. The input terminal of the amplification circuit is connected to the moving contact and then connected to the negative input terminal of the operational amplifier via resistor R3. The reference voltage V is applied to the positive input terminal of operational amplifier U. R。 Because the voltage signal V2 acquired by the resistive voltage acquisition circuit from the induction coil includes V1 superimposed on it... R The output voltage, calculated using a differential amplifier circuit, is A*(V2-V). R The signal is calculated as A * V1, where A is the amplification gain. This amplifies the amplitude of the picked-up voltage V1 by a factor of A. After filtering by a subsequent filtering circuit, the signal is output to an analog-to-digital converter (ADC) for analog-to-digital conversion, which is then used for subsequent measurement calculations (such as angle). As an example, the filtering circuit can be an RC filter circuit. Resistor R5 is connected to the output of the amplification circuit and one end of capacitor C2, respectively, to lead out the output of the signal circuit. The other end of C2 is grounded.

[0052] You can refer to them together. Figure 3 and Figure 4 The diagrams shown illustrate the switching of different signal flows by the single-pole double-throw switch. Figure 3 In the diagram, when a first-level (e.g., high-level) switch control signal is applied to the switch control terminal of a single-pole double-throw switch, the first switching state of the switch is triggered. Its moving contact E is connected to a stationary contact D below. It can be seen that the signal flow originates from the reference signal terminal, flows downwards through the induction coil, and is output from the stationary contact D to the moving contact E. Figure 4 In the diagram, when a second-level (e.g., low-level) switching control signal is applied to the switching control terminal of a single-pole double-throw switch, the second switching state of the switch is triggered. The moving contact E connects to the other stationary contact F. The signal flow can be seen flowing upwards from the reference signal terminal through the induction coil and outputting from the stationary contact F to the moving contact E. The switching frequency of the high and low levels of the switching control signal can be the same as the excitation signal of the transmitting coil; that is, the switching control signal can be a square wave signal with the same frequency as the excitation signal. For a sinusoidal voltage signal, its negative half-cycle will be flipped upwards to a positive amplitude due to the switching of the signal flow direction, exhibiting a similar pattern. Figure 5 The waveform ensures that the voltage amplitude of the signal input to the subsequent stage is positive, and is superimposed with the reference signal V. RRaising the voltage makes it easier for subsequent circuits to process / calculate.

[0053] It is understandable that the examples of related technologies only show one induction coil and its corresponding signal circuit. For incremental electromagnetic induction encoders, at least one code track is required, and a single code track requires two induction lines and two signal conditioning circuits. For absolute electromagnetic induction encoders, since at least two code tracks (coarse and fine) are required, four induction coils and four signal conditioning circuits are needed. In encoders with higher precision requirements, such as 6, 8, or 12 code tracks, 12 induction coils and 12 signal conditioning circuits, 16 induction coils and 16 signal conditioning circuits, and 24 induction coils and 24 signal conditioning circuits are needed, respectively. In some applications, since the noise on the signal is the same (called "common-mode" interference), to reduce errors, each induction coil is configured to include a connected pair of differential numerator coils. For example, a pair of differential numerator coils can be arranged in a symmetrical, opposite sinusoidal wave pattern. Then, the induced voltage on the induction coil will be the difference between the induced voltages of the pair of differential numerator coils. On the one hand, the alternating magnetic field cancels out the induced voltages between the two sub-coils through differential calculation, resulting in a voltage signal amplitude of 0 for the induction coil when the rotor is not moving. When the reference voltage is superimposed, the amplitude becomes V. R The changes only become apparent after the rotor moves, reducing the difficulty of acquiring dynamic changes in the voltage signal amplitude. On the other hand, differential switching can also eliminate noise, making the voltage signal from the induction coil more accurate.

[0054] Therefore, as the number of circuits increases, there will be more circuit components, such as more operational amplifiers and resistors. This leads to higher circuit board complexity, higher power consumption, and higher cost, making it more difficult to miniaturize the encoder.

[0055] In view of this, the present disclosure provides a signal conditioning circuit that simplifies the circuit structure while amplifying the acquired voltage signal. By eliminating the amplification circuit, the complexity, size and cost of the circuit layout are greatly reduced, thereby solving the problems in the related technology.

[0056] like Figure 6 The diagram shown illustrates the structure of a signal conditioning circuit in one embodiment of this disclosure.

[0057] The signal conditioning circuit 102 includes a voltage pickup circuit 121, a second detection circuit 122, and a filter circuit 123.

[0058] and Figure 2The difference between the embodiments is that the voltage pickup circuit 121 in the embodiment is capacitive. Specifically, the voltage pickup circuit 121 includes a capacitive element C, which is connected in parallel with the inductive coil 101 to form a first resonant network. The resonant frequency of the first resonant network matches the frequency of the pickup voltage, which is generated based on the movement of the magnetic marker in the alternating magnetic field generated by the alternating signal of the transmitting coil. The pickup voltage has the same frequency as the alternating signal, and thus the resonant frequency can be set to match the frequency of the excitation signal of the transmitting coil in the electromagnetic encoder. For example, the excitation signal is an alternating signal with a frequency of w, the inductance of the inductive coil 101 is denoted as L, and the capacitance of the capacitive element C is denoted as C. The resonant frequency f is:

[0059] ;

[0060] The resonant frequency f matches the frequency w of the excitation signal, for example, f = w.

[0061] When resonating, the combination of the inductive coil 101 and the voltage pickup circuit 121 presents a pure resistance, so that the pickup voltage is amplified by a gain, i.e., the quality factor Q = 1 / (2π*f*C*R), where R is the equivalent resistance impedance in the combination circuit, which in the embodiment is determined by the resistance R across L, so that the pickup voltage is amplified by a factor of Q. As can be seen, the amplification gain Q can be set according to L, C, and the equivalent resistance of the inductive coil 101. In a specific example, the required Q is obtained by selecting the capacitance value and the inductance value, and the amplification gain of the differential amplifier circuit in the example is the same or close to the amplification gain of the differential amplifier circuit, so that the differential amplifier circuit can be replaced well. Figure 2 The amplification gain of the differential amplifier circuit in the example is the same or close to the amplification gain of the differential amplifier circuit, so that the differential amplifier circuit can be replaced well.

[0062] Therefore, by selecting the capacitive pickup circuit 111, the specified useful frequency band (set according to the excitation frequency and the corresponding pickup voltage frequency) can be obtained, so that the effective amplification of the signal amplitude of the pickup voltage in the useful frequency band can be realized. Therefore, the amplification circuit in the related art can be omitted, so that the circuit structure is effectively simplified, the circuit layout complexity is reduced, the cost is reduced, and the size of the electromagnetic encoder is greatly reduced to meet the miniaturization requirement.

[0063] Since the capacitive voltage pickup circuit 121 is used, to meet the requirement that the signal flow corresponding to the reference voltage needs to be switched bidirectionally through the inductive coil 101, the capacitive element will block the signal flow, and thus the detection circuit 122 needs to bypass the capacitive element C and directly act on the inductive coil 101. Therefore, the single-pole double-throw switch in the related art is not applicable to the signal conditioning circuit 102 in the embodiment.

[0064] In this embodiment, different detection circuits 122 are designed. Each detection circuit 122 includes a reference signal terminal, a signal output terminal O, and a switching unit 1221. The reference signal terminal is supplied with a reference voltage VR. The switching unit 1221 is connected to both ends of the induction coil 101 and is used to switch its state, thereby exchanging the connections of the reference signal terminal and the signal output terminal O with the two ends of the induction coil.

[0065] In some embodiments, the switching unit 1221 includes a double-pole four-throw switch. The double-pole four-throw switch includes: a first stationary contact 12211 and a second stationary contact 12212 respectively coupled to the two ends of the induction coil 101; and a first moving contact 12213 and a second moving contact 12214 respectively coupled to the first stationary contact 12211 and the second stationary contact 12212. The first moving contact 12213 and the second moving contact 12214 are respectively coupled to one of a reference signal terminal and a signal output terminal O. The double-pole four-throw switch has a switch control terminal 12215 that allows receiving a switch control signal, and responds to the switch control signal to switch the coupling object of the first moving contact 12213 and the second moving contact 12214, i.e., switch V. R One end of the induction coil is connected to form a signal flow that flows in from that end and out from the other end.

[0066] like Figure 7 and Figure 8 The diagrams shown illustrate the signal flow direction of the switching unit 1221 being controlled to switch between different switching states in one embodiment of this disclosure.

[0067] exist Figure 7 In the diagram, when a first-level (e.g., high-level) switch control signal is applied to the switch control terminal 12215 of the double-pole four-throw switch, the first switching state of the double-pole four-throw switch is triggered. The first moving contact 12213 is connected to the reference signal terminal, and the second moving contact 12214 is connected to the second stationary contact 12212. The signal flow enters the upper end of the inductor L from the first moving contact 12213 and the second moving contact 12214, flows downward from the lower end of the inductor L, and passes through the second moving contact 12214 and the second stationary contact 12212 to the signal output terminal O. Figure 8In the middle, when the switch control end 12215 of the double-pole four-throw switch applies a second level (such as a low level) of the switch control signal, the second switch state of the double-pole four-throw switch is triggered, the first moving contact 12213 is coupled with the first stationary contact 12211, and the second moving contact 12214 is connected with the reference signal end. It can be seen that the signal flow enters the lower end of the inductor L from the second moving contact 12214, flows out from the upper end of the inductor L, and is output to the signal output end O through the first moving contact 12213 and the first stationary contact 12211. The switching frequency of the high and low levels of the switch control signal can be the same as the excitation signal of the transmitting coil, that is, the switch control signal can be a square wave signal with the same frequency as the excitation signal.

[0068] It is particularly worth mentioning that, in the present embodiment, since the capacitive voltage pickup circuit 121 has already amplified, no amplification circuit is needed in the rear stage. Therefore, the rear stage of the detection circuit 122 can be directly connected to the second filter circuit 123. The second filter circuit 123 is coupled to the rear stage of the detection circuit 122, and the output end thereof leads out the output end of the signal conditioning circuit 102. Optionally, the second filter circuit 123 can adopt a simple RC filter circuit 123, which is exemplarily composed of R6 and C3. After signal filtering, the signal enters the signal processing unit 103.

[0069] As an example, the signal processing unit 103 can include an analog-to-digital converter in the front stage, and a processor for solving the measured value in the rear stage. In some embodiments, the processor can be implemented by a central processing unit (CPU), a micro processing unit (MCU), a system on chip (SoC), or a field programmable logic array (FPGA), etc. The processor can be used in cooperation with a memory, which can include a volatile memory (Volatile Memory) for data temporary storage when running a program, such as a random access memory (RAM). Alternatively, the memory can also include a non-volatile memory (non-volatile memory) for data storage, such as a read-only memory (Read-Only Memory, ROM), a flash memory, etc.

[0070] In some embodiments, considering the cost of the double-pole four-throw switch, the two single-pole double-throw switches can be replaced. The two single-pole double-throw switches are arranged to change synchronously in switch state. In a specific example, the switch control ends 12215 of the two single-pole double-throw switches can be connected in common to be applied with a switch control signal.

[0071] It should be particularly noted that, Figure 6 to Figure 8The capacitor element C in the equivalent circuit is only a representation of the equivalent circuit, and in actual implementation, can be implemented by one or more capacitor devices.

[0072] In some embodiments, considering that the excitation frequency can change, the capacitor element C can include a variable capacitor, for example Figure 7 The variable capacitor is a capacitor whose capacitance can be adjusted within a certain range. The relative inter-plate spacing or effective area between the plates forming the capacitance can be changed through a mechanical structure, and then the capacitance of the variable capacitor changes accordingly. When the excitation frequency changes, the capacitance value of the capacitor element is adjusted so that the resonant frequency still matches the changed excitation frequency, thereby completing the tuning.

[0073] In some embodiments, the capacitor element can include a plurality of capacitor devices connected in parallel, and the capacitance value of the capacitor element is the sum of the capacitance values of the respective capacitor devices connected in parallel. Through the parallel connection of a plurality of capacitor devices, not only the total capacitance value can be improved, but also the parallel connection of the capacitor devices can offset the reactive power of the inductive load to improve the power factor, and the resistances contained in the capacitor devices are connected in parallel to reduce the equivalent resistance value. Moreover, by connecting large and small capacitor devices with large capacitance value difference in parallel, the ripple in the application scenario of the switching power supply can be effectively reduced.

[0074] As shown in Figure 9 , a structural schematic diagram of an electromagnetic induction encoder in an embodiment of the present disclosure is shown.

[0075] In Figure 9 , the electromagnetic induction encoder includes a rotor and a stator. The stator includes at least one transmitting coil 104, at least one inductive coil group, and circuit system. Each inductive coil group includes a pair of inductive coils 101 arranged with a preset phase difference, for example, a sin inductive coil and a cos inductive coil.

[0076] The circuit system includes the signal conditioning circuit 102 in the embodiment, the number of which is consistent with the number of inductive coils 101, and each inductive coil 101 is coupled one by one.

[0077] The circuit system further includes a signal processing unit 103 coupled with the output end of the signal conditioning circuit 102. As an example, the signal processing unit 103 can include an analog-to-digital converter and a processor. The analog-to-digital converter and the processor can be separately arranged and communicatively connected with each other; or the analog-to-digital converter and the processor can also be integrated as a whole. For example, the analog-to-digital converter is integrated into the processor.

[0078] It should be noted that the relationship between the bandwidth B W and the quality factor Q is B W=f / Q, i.e. a negative correlation between them. If the Q of the first resonant network of the induction coil 101 is increased, the bandwidth will be correspondingly narrowed. In order to balance the relationship between the stable bandwidth and the larger amplification gain, the multi-stage magnetic field coupling relationship between the transmitting coil 104, the magnetic marker 210 and the induction coil 101 can be utilized, and a resonant network can also be constructed for the transmitting coil 104 and / or the magnetic marker 210. The required total quality factor is distributed to each resonant network, so that a suitable bandwidth and a not very large quality factor are obtained at each stage, but the amplification effect of the multi-stage resonant network is superimposed to obtain a larger total quality factor, thereby achieving the desired bandwidth and total amplification gain of the pickup voltage signal amplitude.

[0079] As shown in FIG. 1, a schematic diagram of the transmitting coil 104, the magnetic marker 210 and the induction coil 101 respectively constituting an LC resonant network in an embodiment of the present disclosure is shown. Figure 10

[0080] In the present embodiment, the transmitting coil 104 is connected in parallel with a second capacitive element C1 to construct a second resonant network having the same resonant frequency as the first resonant network. In addition, the magnetic marker 210 can be implemented in the form of a coil, which is defined as a magnetic field variation coil herein. The magnetic field variation coil is connected in parallel with a third capacitive element C2 to construct a third resonant network having the same resonant frequency as the first resonant network.

[0081] As an example, a receiving coil 211 can also be provided on the mover, which is arranged in pairs with the transmitting coil 104, for obtaining electrical energy from the transmitting coil 104 through electromagnetic induction. The receiving coil 211 can be connected to the magnetic field variation coil as a power supply through a magnetic field generation signal circuit (not shown) to make the magnetic field variation coil form a regularly varying magnetic field acting on the induction coil 101 by powering and working the magnetic field generation signal circuit to output a magnetic field generation signal (which can be consistent with the excitation signal frequency, such as a regularly varying voltage signal, current signal, etc.) to the magnetic field variation coil. The induction coil 101 generates an induction signal under the action of the varying magnetic field and is collected by the signal conditioning circuit 102 in FIG. 1. The receiving coil 211 can also be connected in parallel with a fourth capacitive element C3 to construct a fourth resonant network. The first resonant network, the second resonant network, the third resonant network and the fourth resonant network have matching resonant frequencies, and gradually form a common amplification effect on the amplitude of the induction signal on the induction coil 112. In some embodiments, for the multi-stage resonant network based on the transmitting coil 104, the receiving coil 211 and the magnetic marker 210 implemented by a coil to the magnetic field induction coil 112, a product effect will be presented between their amplification gains. Figure 6

[0082] ​​Alternatively, if the magnetic marker 210 is not implemented as an inductive element such as a coil, but as a metal conductor (which can also be magnetic), then no third resonance network can be built at the level of the magnetic marker 210, and only the first and second resonance networks can be provided, which together amplify the amplitude of the voltage signal on the induction coil 101.

[0083] Reference can be made to Figure 11 As shown, a schematic diagram is shown to illustrate that in another embodiment of the disclosure, the transmission coil 104 and the induction coil 101 respectively constitute LC resonance networks.

[0084] In this embodiment, the transmission coil 104 is connected in parallel with a second capacitive element C1 to construct a second resonance network having the same resonance frequency as the first resonance network. In addition, the magnetic marker 210 is implemented as a metal conductor. The first and second resonance networks together amplify the amplitude of the voltage signal on the induction coil 101. As an example, a product effect can be exhibited between their amplification gains. Figure 10 and Figure 11 It is also shown in the figure that the signal conditioning circuit 102 is connected to the induction coil 101.

[0085] In the following, the improved effects brought by the signal conditioning circuit 102 in the embodiments of the disclosure on the electromagnetic induction encoder are specifically illustrated.

[0086] In some embodiments, the electromagnetic induction encoder is implemented as an incremental electromagnetic induction encoder, including at least one of the induction coil groups and a corresponding number of signal conditioning circuits 102. For example, an incremental electromagnetic induction encoder has one induction coil group corresponding to a single code track, including one sin induction coil and one cos induction coil, and accordingly has two signal conditioning circuits 102. Compared with the prior art Figure 2 In the embodiment, the two signal conditioning circuits 102 can reduce two amplification circuits.

[0087] In some embodiments, the electromagnetic induction encoder is implemented as an absolute electromagnetic induction encoder, including at least two of the induction coil groups and a corresponding number of signal conditioning circuits 102. For example, a double-code-track absolute electromagnetic induction encoder has two induction coil groups, including two pairs of sin induction coils and cos induction coils, and accordingly has four signal conditioning circuits 102. Compared with the prior art Figure 2 In the embodiment, the four signal conditioning circuits 102 can reduce four amplification circuits.

[0088] Similarly, in the absolute type electromagnetic induction encoder of 6 channels, 8 channels, 12 channels, corresponding to 12 signal conditioning circuits 102, 16 signal conditioning circuits 102, 24 signal conditioning circuits 102, 12, 16, 24 amplification circuits can be reduced accordingly.

[0089] Therefore, the signal conditioning circuit in the embodiment of the present disclosure can achieve circuit structure simplification, circuit cost saving, power consumption reduction, and circuit volume reduction, that is, a large number of high-precision operational amplifier chips can be saved, the board layout complexity of the circuit board can be greatly simplified, the circuit cost can be greatly reduced, the circuit power consumption can be greatly reduced, the product volume of the encoder can be greatly reduced, and great commercial value is obtained.

[0090] In summary, the present disclosure relates to a signal conditioning circuit and an electromagnetic induction encoder. The signal conditioning circuit comprises: a voltage pickup circuit comprising: a capacitive element connected in parallel with the induction coil and constituting a first resonant network to amplify the amplitude of the voltage signal collected from the induction coil; wherein the resonant frequency of the first resonant network matches the frequency of the pickup voltage of the induction coil and the frequency of the excitation signal of the transmitting coil in the electromagnetic induction encoder; a detection circuit comprising: a reference signal end, a signal output end and a switching switch unit; wherein the reference signal end is applied with a reference voltage; the switching switch unit is connected between the two ends of the induction coil and is used to switch the connection state to exchange the connection between the reference signal end and the signal output end and the two ends of the induction coil; and a filter circuit coupled to the rear stage of the detection circuit, and the output end of the filter circuit leads out the output end of the signal conditioning circuit. The voltage pickup circuit and the induction coil constitute a resonant network, which can amplify the pickup voltage, and the detection circuit with the corresponding structure change completes demodulation, and the signal amplification circuit is omitted, thereby simplifying the structure, volume, cost and reducing the power consumption, and the advantages are particularly prominent in the encoder with high precision and multiple channels.

[0091] The above embodiments only exemplarily illustrate the principles and effects of the present disclosure, and are not used to limit the present disclosure. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present disclosure shall be covered by the protection scope of the present disclosure.

Claims

1. A signal conditioning circuit, characterized in that, Applications include electromagnetic induction encoders that incorporate induction coils, including: A voltage pickup circuit includes: a capacitor element connected in parallel with the induction coil to form a first resonant network, so as to amplify the amplitude of the voltage signal acquired from the induction coil; wherein the resonant frequency of the first resonant network is matched with the frequency of the pickup voltage of the induction coil and the frequency of the excitation signal of the transmitting coil in the electromagnetic induction encoder. The detection circuit includes: a reference signal terminal, a signal output terminal, and a switching unit; wherein, the reference signal terminal is supplied with a reference voltage; the switching unit is connected to both ends of the induction coil and is used to switch the switching state so that the reference signal terminal and the signal output terminal exchange their connections with both ends of the induction coil; A filter circuit is coupled to the stage following the detector circuit, and its output is led out from the output of the signal conditioning circuit.

2. The signal conditioning circuit according to claim 1, characterized in that, The switching unit includes: A double-pole four-throw switch includes: a first stationary contact and a second stationary contact respectively coupled to the two ends of an induction coil; a first moving contact and a second moving contact respectively coupled to the first stationary contact and the second stationary contact; the first moving contact and the second moving contact are respectively coupled to one of a reference signal terminal and a signal output terminal; The double-pole four-throw switch has a switch control terminal that allows receiving switch control signals, and switches the coupling objects of the first moving contact and the second moving contact in response to the switch control signals.

3. The signal conditioning circuit according to claim 1, characterized in that, The switching unit includes two single-pole double-throw switches, which are configured to change their switching states synchronously.

4. The signal conditioning circuit according to claim 1, characterized in that, The capacitor element includes a variable capacitor; and / or, the capacitor element includes a plurality of capacitor elements connected in parallel.

5. The signal conditioning circuit according to claim 1, characterized in that, The filtering circuit includes an RC filter.

6. The signal conditioning circuit according to claim 1, characterized in that, The transmitting coil is connected in parallel with a second capacitor to construct a second resonant network with the same resonant frequency as the first resonant network. The first and second resonant networks together amplify the amplitude of the voltage signal on the induction coil. And / or, when the magnetic marker in the rotor of the electromagnetic induction encoder, which senses the magnetic field generated by the excitation signal, is implemented as a coil, the magnetic marker is connected in parallel with a third capacitor to construct a third resonant network with the same resonant frequency as the first resonant network. The first, second, and third resonant networks together amplify the amplitude of the voltage signal on the induction coil.

7. An electromagnetic induction encoder, characterized in that, include: The rotor includes: magnetic markings; Stator, including: At least one transmitting coil; At least one induction coil group, including a pair of induction coils arranged with a predetermined phase difference; The circuit system includes: At least two signal conditioning circuits as described in any one of claims 1 to 6 are coupled one-to-one with each of the induction coils; The signal processing unit is coupled to the output terminal of the signal conditioning circuit.

8. The electromagnetic induction encoder according to claim 7, characterized in that, The transmitting coil is connected in parallel with a second capacitor to construct a second resonant network with the same resonant frequency as the first resonant network. The first and second resonant networks together amplify the amplitude of the voltage signal on the induction coil. The magnetic mark is implemented as a coil, and the magnetic mark is connected in parallel with a third capacitor to construct a third resonant network with the same resonant frequency as the first resonant network. The first, second, and third resonant networks together amplify the amplitude of the voltage signal on the induction coil.

9. The electromagnetic induction encoder according to claim 7, characterized in that, The electromagnetic induction encoder is implemented as an absolute electromagnetic induction encoder, including: at least two of the induction coil groups and a corresponding number of signal conditioning circuits; or, the electromagnetic induction encoder is implemented as an incremental electromagnetic induction encoder, including: at least one of the induction coil groups and a corresponding number of signal conditioning circuits.

10. The electromagnetic induction encoder according to claim 9, characterized in that, Each of a pair of induction coils arranged according to a preset phase difference includes a pair of connected differential coils.

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