Rotary transformer control protection circuit and protection method thereof

Abstract

The application relates to the technical field of rotary transformers, in particular to a rotary transformer control protection circuit and a protection method thereof, wherein the circuit compares a feedback signal with a normal feedback threshold interval to determine the circuit state of the rotary transformer, can realize fast response to the abnormal state of the circuit, and thus protects the circuit in time. Meanwhile, when the feedback signal is in the normal feedback threshold interval, the feedback signal detection circuit can be regarded as an open circuit due to the high-impedance input characteristics of the comparator, the current of the feedback signal shared by the feedback signal detection circuit is very small, the feedback signal detection circuit cannot lower the amplitude of the feedback signal received by the AD decoding chip, the accuracy of the rotor angle calculated by the AD decoding chip is ensured, and the independence of protection and measurement is realized.

Description

Technical Field

[0001] This invention relates to the field of rotary transformer technology, and more specifically to a rotary transformer control and protection circuit and its protection method. Background Technology

[0002] In the field of electric vehicles, resolvers are typically used to measure the rotation angle of the vehicle's drive motor. In practical applications, due to the distance between the drive motor and the control system, long wiring harnesses are required to connect the control system to the resolver, posing risks of wire breakage, short circuits, or external electrostatic interference. For example, a short circuit in the excitation circuit can easily lead to the burnout of the excitation winding or other components, and also cause the loss of feedback signals. Conversely, a short circuit in the feedback circuit or electrostatic interference can cause the feedback voltage to exceed the threshold, easily leading to errors in the control system's calculation of the motor's rotation angle, resulting in abnormal motor control such as vibration or sudden acceleration, and potentially causing danger.

[0003] The prior art CN107834515B discloses a short-circuit protection circuit for a resolver excitation system. It achieves short-circuit protection for the resolver excitation winding by connecting a short-circuit protection circuit in series between the excitation power amplifier circuit and the resolver excitation winding. The short-circuit protection circuit determines whether a short-circuit fault has occurred in the resolver excitation system by detecting the output status of the resolver excitation system. If a short-circuit fault occurs, it controls the excitation power amplifier circuit to stop outputting the excitation signal and pulls the current of the excitation system down to near 0, thereby protecting the excitation circuit.

[0004] However, the control system's calculation of the motor's rotation angle depends on the feedback signal from the rotary transformer. Therefore, the calculation accuracy is very sensitive to the voltage amplitude. If the above-mentioned existing technology is applied to the short-circuit protection of the feedback circuit, it will inevitably affect the amplitude of the feedback signal collected by the system and reduce the accuracy of the angle calculation. Summary of the Invention

[0005] To address the technical problem that existing technologies affect the amplitude of feedback signals during short-circuit protection, this application provides a control and protection circuit for a rotary transformer and its protection method, wherein the circuit includes:

[0006] A feedback output circuit is used to output the feedback signal generated by the rotary transformer. The output terminal of the feedback output circuit is connected to both the input terminal of the AD decoding chip and the input terminal of the feedback signal detection circuit.

[0007] The AD decoding chip is used to calculate the rotor angle of the rotary transformer based on the received feedback signal;

[0008] The feedback signal detection circuit includes a comparator, the output of which is connected to the excitation signal conditioning circuit. The comparator is used to compare the input feedback signal with the normal feedback threshold range and send a control signal to the excitation signal conditioning circuit based on the comparison result.

[0009] The excitation signal conditioning circuit is used to send an excitation electrical signal to the rotor winding of the rotary transformer;

[0010] When the feedback signal is outside the normal feedback threshold range, the feedback signal detection circuit sends an abnormal signal to the excitation signal conditioning circuit, and the excitation signal conditioning circuit stops sending excitation electrical signals to the rotary transformer.

[0011] The beneficial effect of the above circuit is that by comparing the feedback signal with the normal feedback threshold range to determine the circuit state of the rotary transformer, a rapid response to abnormal circuit conditions can be achieved, thereby protecting the circuit in a timely manner. Simultaneously, when the feedback signal is within the normal feedback threshold range, due to the high impedance input characteristics of the comparator, the feedback signal detection circuit can be approximated as an open circuit. The current diverted by the feedback signal detection circuit is very small, ensuring that the feedback signal detection circuit does not lower the amplitude of the feedback signal received by the AD decoding chip. This guarantees the accuracy of the rotor angle calculated by the AD decoding chip, achieving independence between protection and measurement.

[0012] The rotary transformer circuit protection method provided by this invention is based on the above-mentioned circuit and specifically includes the following steps:

[0013] Obtain the sinusoidal and cosine feedback signals of the rotary transformer;

[0014] When either the sinusoidal feedback signal or the cosine feedback signal is outside the normal feedback threshold range, stop supplying the excitation signal to the rotary transformer; otherwise, calculate the sum of squares of the sinusoidal feedback signal and the cosine feedback signal, and calculate the absolute difference between the sum of squares and the induced voltage constant.

[0015] The absolute difference is compared with the trigonometric relationship threshold. If the absolute difference is greater than the trigonometric relationship threshold, a fault command is issued, and the rotor angle of the rotary transformer is no longer calculated using the sine and cosine feedback signals.

[0016] The beneficial effect of the above method is that it makes a preliminary judgment on whether the feedback signal of the rotary transformer is normal by checking whether the sine and cosine feedback signals are within the normal feedback threshold range. Then, it further judges whether the sine and cosine feedback signals are normal by checking whether the relationship between them conforms to the basic trigonometric function relationship. This dual protection mechanism not only retains the rapid response of the hardware level and can protect the circuit in time when serious faults occur, but also has the precise analysis and identification of the software to discover potential faults and anomalies. It effectively avoids the omissions that may occur due to a single signal threshold judgment, and greatly improves the reliability and safety of the feedback circuit. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the circuit provided by the present invention.

[0018] Figure 2 This is an overall flowchart of the method provided by the present invention.

[0019] The attached figures are labeled as follows: 10, feedback output circuit; 20, AD decoding chip; 30, feedback signal detection circuit; 40, excitation signal conditioning circuit; 50, MCU unit. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] When the excitation current of the rotor winding of a rotary transformer varies according to a fixed pattern (e.g., a sine wave with a fixed amplitude), the magnitude of the induced electromotive force generated in its stator winding is determined by the angle between the stator winding and the rotor winding. For a given circuit, the amplitude fluctuation range of the induced electromotive force generated by the stator winding under normal conditions is fixed.

[0023] Based on the above analysis, and referring to Figure 1 The present invention provides a control and protection circuit for a rotary transformer, comprising: a feedback output circuit 10, an AD decoding chip, a feedback signal detection circuit 30, and an excitation signal conditioning circuit 40.

[0024] The output terminal of the feedback output circuit 10 is connected to both the AD decoding chip and the input terminal of the feedback signal detection circuit 30, and is used to output the feedback signal generated by the stator winding of the rotary transformer.

[0025] The AD decoding chip is used to calculate the rotor angle of the rotary transformer based on the received feedback signal;

[0026] The feedback signal detection circuit 30 includes a comparator, the output of which is connected to the excitation signal conditioning circuit 40. The comparator is used to compare the input feedback signal with the normal feedback threshold range and send a control signal to the excitation signal conditioning circuit 40 according to the comparison result.

[0027] The excitation signal conditioning circuit 40 is used to send an excitation electrical signal to the rotor winding of the rotary transformer according to the control signal;

[0028] When the feedback signal deviates from the normal feedback threshold range, the feedback signal detection circuit 30 sends an abnormal signal to the excitation signal conditioning circuit 40, and the excitation signal conditioning circuit 40 stops sending excitation electrical signals to the rotary transformer to protect the entire rotary transformer control circuit.

[0029] When the excitation current of the rotor winding of a rotary transformer varies according to a fixed pattern (e.g., a sine wave with a fixed amplitude), the magnitude of the induced electromotive force (feedback signal) generated by its stator winding is determined by the angle between the stator and rotor windings. For a given circuit, the amplitude fluctuation range of the induced electromotive force generated by the stator winding under normal conditions is fixed. Therefore, by comparing the feedback signal with the normal feedback threshold range to determine the circuit state of the rotary transformer, a rapid response to abnormal circuit conditions can be achieved, thereby protecting the circuit in a timely manner. Simultaneously, when the feedback signal is within the normal feedback threshold range, due to the high impedance input characteristics of the comparator, the feedback signal detection circuit 30 can be approximated as an open circuit. The current allocated to the feedback signal by the feedback signal detection circuit 30 is very small, ensuring that the feedback signal detection circuit 30 does not lower the amplitude of the feedback signal received by the AD decoding chip, thus guaranteeing the accuracy of the rotor angle calculated by the AD decoding chip and achieving independence between protection and measurement.

[0030] Specifically, when the feedback signal of the rotary transformer exceeds the upper limit of the normal feedback threshold range, it indicates that the feedback output circuit 10 is likely to have a short-circuit fault. The comparator can quickly respond to the overload current signal and rapidly send a high-level signal (abnormal signal) to the excitation signal conditioning circuit 40. The excitation signal conditioning circuit 40 then stops sending excitation signals to the rotary transformer, thereby preventing circuit current overload caused by the short-circuit fault. At the same time, since there is no current in the excitation circuit, the feedback output circuit 10 no longer generates an induced electromotive force, thus achieving simultaneous protection of both the excitation circuit and the feedback output circuit 10.

[0031] When the feedback signal of the rotary transformer falls below the lower limit of the normal feedback threshold range, it indicates a fault in the circuit. For example, a short circuit in the excitation circuit of the rotary transformer causes current to flow through the short circuit, resulting in no current flowing through the rotor windings and preventing the stator windings from generating an induced electromotive force, thus causing the feedback signal to be zero. Alternatively, an open circuit in the feedback output circuit 10 will also cause the feedback signal detection circuit 30 to measure a zero feedback signal. In this case, the feedback output detection circuit sends an abnormal signal to the excitation signal conditioning circuit 40, stopping the power supply to the rotor windings of the rotary transformer and protecting the circuit.

[0032] Furthermore, this circuit also includes an MCU unit, which is connected to the output of the comparator in the feedback signal detection circuit 30 and the output of the AD decoding chip. The MCU unit is used to send motor control signals to the motor drive unit according to the rotor angle calculated by the AD decoding chip. At the same time, when the feedback signal detection circuit 30 issues an abnormal signal, the excitation signal conditioning circuit 40 and the MCU unit synchronously receive this abnormal signal, and the MCU unit no longer sends motor control signals to the motor drive unit according to the rotor angle calculated by the AD decoding chip.

[0033] When the feedback signal is outside the normal feedback threshold range, the motor rotation angle calculated based on the induced electromotive force is likely to be incorrect. If the drive motor is controlled based on this incorrect calculation, the vehicle's driving state may deviate from the driver's intention. Therefore, upon receiving an abnormal signal, the MCU unit stops controlling the drive motor based on the rotor angle, thereby preventing abnormal drive motor operation.

[0034] Furthermore, the AD decoding chip is also used to determine whether there is a fault in the feedback output circuit 10 based on the feedback signal.

[0035] Specifically, in practical applications, the stator of a rotary transformer typically has two mutually perpendicular induction windings. When an excitation current is applied to the excitation coil in the rotor, different induced electromotive forces (EMFs) are generated in the two induction windings. The induced EMFs generated by the two stator windings change with the rotation of the drive motor, exhibiting sinusoidal and cosine waveforms respectively. This is essentially because the two stator windings are perpendicular, resulting in a 90° phase difference in the generated EMFs. The relationship between the induced EMFs generated by the two stator windings and the rotation angle of the drive motor is as follows:

[0036]

[0037]

[0038] In the formula, The transformer ratio is determined by the arrangement of the rotor excitation winding and stator winding of the rotary transformer, as well as the coil ratio. It is the excitation signal (excitation signal) input to the rotor excitation winding, which is generated by the excitation signal conditioning circuit. That is, the angle of the drive motor. , These are the feedback signals output from the sine and cosine windings, respectively.

[0039] When detecting feedback signals from a rotary transformer, four detection circuits can be set up: SIN+ detection circuit, SIN- detection circuit, COS+ detection circuit, and COS- detection circuit, to detect the feedback signals generated by the two stator windings respectively. When calculating the angle of the drive motor, the sinusoidal feedback signal... The cosine feedback signal is the amplitude difference (i.e., the sum of the absolute values ​​of the two amplitudes) measured by the SIN+ and SIN- detection circuits. The difference in amplitude of the feedback signal measured by the COS+ detection circuit and the COS- detection circuit (i.e., the sum of the absolute values ​​of the two amplitudes).

[0040] Based on the sine and cosine relationship at the same angle:

[0041]

[0042] Therefore, sinusoidal feedback signal Sum and cosine feedback signals The ideal relationship between them is:

[0043]

[0044] In the formula, It is a constant (induced voltage constant), determined by the specific design parameters of the circuit.

[0045] When the result calculated based on the amplitude difference of the feedback signal deviates significantly from the induced voltage constant C (for example, the deviation exceeds the trigonometric relationship threshold), it indicates that although the amplitude of the feedback signal itself is normal, it has lost the correct sine and cosine relationship, and the calculated angle is definitely incorrect. This usually means that a more complex fault has occurred in the resolver or front-end circuit. The AD decoding chip sends a fault command to the MCU unit. At this time, the MCU unit no longer uses the angle calculated from this feedback signal as a basis to control the drive motor's operation, thus preventing the drive motor from performing abnormal actions due to incorrect angle.

[0046] Example 2

[0047] refer to Figure 2 Based on the circuit provided in Embodiment 1, the present invention also provides a method for protecting a rotary transformer circuit, comprising the following steps:

[0048] S1. Obtain the sinusoidal and cosine feedback signals of the rotary transformer;

[0049] S2. When either the sinusoidal feedback signal or the cosine feedback signal is outside the normal feedback threshold range, stop supplying the excitation signal to the rotary transformer; otherwise, calculate the sum of squares of the sinusoidal feedback signal and the cosine feedback signal, and calculate the absolute difference between the sum of squares and the induced voltage constant.

[0050] S3. Compare the absolute difference with the trigonometric relationship threshold. If the absolute difference is greater than the trigonometric relationship threshold, issue a fault command and stop calculating the rotor angle of the rotary transformer using sine and cosine feedback signals.

[0051] The advantage of this method lies in its comprehensive protection of the rotary transformer feedback signal through a dual-judgment mechanism. First, in step S2, it judges whether a single feedback signal (sine or cosine) is within the normal feedback threshold range. If an anomaly is detected, the supply of excitation signal to the rotary transformer is immediately stopped, preventing potential damage to subsequent circuits from continuous input of abnormal signals. This is a fast and direct primary protection measure. Second, for feedback signals that pass the primary judgment, steps S2 and S3 further introduce the calculation of the absolute difference between the sum of squares and the induced voltage constant, and compare it with a trigonometric threshold. This judgment, based on the fundamental trigonometric relationship that the sine and cosine feedback signals of the rotary transformer should satisfy (i.e., the sum of the squares of the sine and cosine equals 1, corresponding to the relationship with the induced voltage constant in practical applications), can accurately identify situations where a single signal, although within the threshold range, has an abnormal phase or amplitude relationship with the induced voltage constant, thus achieving deeper and more precise fault detection. This dual protection mechanism not only responds quickly and can protect the circuit in time when a serious fault occurs, but also makes accurate judgments, effectively avoiding the omissions that may occur due to judgment based on a single signal threshold. This greatly improves the reliability and safety of the feedback circuit and ensures the stable operation of the motor control system under complex working conditions.

[0052] The sinusoidal feedback signal is the sum of the absolute value of the amplitude of the feedback signal measured by the SIN+ detection circuit and the absolute value of the amplitude of the feedback signal measured by the SIN- detection circuit.

[0053] The cosine feedback signal is the sum of the absolute value of the amplitude of the feedback signal measured by the COS+ detection circuit and the absolute value of the amplitude of the feedback signal measured by the COS- detection circuit.

[0054] Because the sinusoidal and cosine feedback signals output by the resolver are differential signals, the feedback signal of each phase (SIN phase or COS phase) is determined by the voltage signals transmitted on the two lines (SIN+ and SIN-), which have equal amplitude but opposite phase. Therefore, the effective signal information is the voltage difference between SIN+ and SIN- and the voltage difference between COS+ and COS-, rather than their respective voltages to ground. The advantage of using differential signals is that any common-mode noise superimposed on the two signal lines (such as external electrostatic interference or electromagnetic interference) will cancel each other out, because the receiver only cares about the difference between the two. This is very suitable for harsh environments with long wiring harnesses.

[0055] Furthermore, the fault type can be preliminarily determined using four detection circuits (SIN+ detection circuit, SIN- detection circuit, COS+ detection circuit, and COS- detection circuit). The specific determination method is as follows:

[0056] S4. For any detection circuit, if the feedback signal on the detection circuit is greater than the upper limit of the normal feedback threshold range, while the feedback signals of other detection circuits are within the normal feedback threshold range, then the detection circuit is short-circuited to the power supply.

[0057] S5. For any detection circuit, if the feedback signal on the detection circuit is less than the lower limit of the normal feedback threshold range, while the feedback signals of other detection circuits are within the normal feedback threshold range, then the detection circuit is disconnected.

[0058] S6. For two detection circuits in the same phase, if the feedback signals on both detection circuits are not within the normal feedback threshold range at the same time, then the two detection circuits in that phase are short-circuited.

[0059] S7. When all feedback signals from the detection circuits are within the normal feedback threshold range, but the absolute difference between the sum of the squares of the sine and cosine feedback signals and the induced voltage constant is greater than the trigonometric relationship threshold, it indicates external interference or device damage.

[0060] Through the above steps, the independent analysis and cross-verification of the feedback signals from each detection circuit can achieve accurate identification of various fault types in the rotary transformer feedback system. This provides maintenance personnel with reference opinions when faults occur, facilitating timely troubleshooting and improving maintenance efficiency.

[0061] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control and protection circuit for a rotary transformer, characterized in that, include: A feedback output circuit is used to output the feedback signal generated by the rotary transformer. The output terminal of the feedback output circuit is connected to both the input terminal of the AD decoding chip and the input terminal of the feedback signal detection circuit. The AD decoding chip is used to calculate the rotor angle of the rotary transformer based on the received feedback signal; The feedback signal detection circuit includes a comparator, the output of which is connected to the excitation signal conditioning circuit. The comparator is used to compare the input feedback signal with the normal feedback threshold range and send a control signal to the excitation signal conditioning circuit based on the comparison result. The excitation signal conditioning circuit is used to send an excitation electrical signal to the rotor winding of the rotary transformer; When the feedback signal is outside the normal feedback threshold range, the feedback signal detection circuit sends an abnormal signal to the excitation signal conditioning circuit, and the excitation signal conditioning circuit stops sending excitation electrical signals to the rotary transformer.

2. The circuit according to claim 1, characterized in that, The feedback signal detection circuit includes: SIN+ detection circuit and SIN- detection circuit are used to measure sinusoidal feedback signals; COS+ and COS- detection circuits are used to measure cosine feedback signals.

3. The circuit according to claim 2, characterized in that, The sinusoidal feedback signal is the sum of the absolute value of the amplitude of the feedback signal measured by the SIN+ detection circuit and the absolute value of the amplitude of the feedback signal measured by the SIN- detection circuit. The cosine feedback signal is the sum of the absolute value of the amplitude of the feedback signal measured by the COS+ detection circuit and the absolute value of the amplitude of the feedback signal measured by the COS- detection circuit.

4. The circuit according to claim 1, characterized in that, The rotary transformer control and protection circuit also includes an MCU unit. The output of the comparator is connected to the MCU unit. When the feedback signal is not within the normal feedback threshold range, the comparator sends an abnormal signal to the MCU unit, and the MCU unit no longer controls the drive motor according to the rotor angle.

5. The circuit according to claim 4, characterized in that, The AD decoding chip also determines whether to issue a fault command based on the feedback signal. The specific steps include: The sum of squares of the sinusoidal and cosine feedback signals is calculated. When the absolute difference between the sum of squares and the induced voltage constant is greater than the trigonometric relationship threshold, a fault command is sent to the MCU unit.

6. A method for protecting a rotary transformer circuit, employing the circuit described in any one of claims 1-5, characterized in that, Includes the following steps: Obtain the sinusoidal and cosine feedback signals of the rotary transformer; When either the sinusoidal feedback signal or the cosine feedback signal is outside the normal feedback threshold range, stop supplying the excitation signal to the rotary transformer; otherwise, calculate the sum of squares of the sinusoidal feedback signal and the cosine feedback signal, and calculate the absolute difference between the sum of squares and the induced voltage constant. The absolute difference is compared with the trigonometric relationship threshold. If the absolute difference is greater than the trigonometric relationship threshold, a fault command is issued, and the rotor angle of the rotary transformer is no longer calculated using the sine and cosine feedback signals.

7. The method according to claim 6, characterized in that, The sinusoidal feedback signal is the sum of the absolute value of the amplitude of the feedback signal measured by the SIN+ detection circuit and the absolute value of the amplitude of the feedback signal measured by the SIN- detection circuit. The cosine feedback signal is the sum of the absolute value of the amplitude of the feedback signal measured by the COS+ detection circuit and the absolute value of the amplitude of the feedback signal measured by the COS- detection circuit.

8. The method according to claim 6, characterized in that, The method further includes: For any detection circuit, if the feedback signal on the detection circuit is greater than the upper limit of the normal feedback threshold range, while the feedback signals of other detection circuits are within the normal feedback threshold range, then the detection circuit is short-circuited to the power supply. For any detection circuit, if the feedback signal on the detection circuit is less than the lower limit of the normal feedback threshold range, while the feedback signals of other detection circuits are within the normal feedback threshold range, then the detection circuit is disconnected. For two detection circuits in the same phase, if the feedback signals on both detection circuits are not within the normal feedback threshold range at the same time, then the two detection circuits in that phase are short-circuited. When the feedback signals of all detection circuits are within the normal feedback threshold range, but the absolute difference between the sum of the squares of the sine and cosine feedback signals and the induced voltage constant is greater than the trigonometric relationship threshold, it indicates external interference or device damage.

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