Filter system for BDC ripple detection

Abstract

The invention discloses a filter system used for BDC ripple detection, which comprises a DC power supply, a ripple motor, a current sensing amplifier, a filter, an MCU central processing unit, a comparator and an LDO linear voltage regulator, the current sensing amplifier of the filter system senses current ripples, and the filter carries out filtering and amplification to obtain the ripple ripples. And then converting into a rising edge and a falling edge (PWM waves) of a 3.3 V digital logic level series which can be acquired by the MCU through a comparator, and finally, determining the speed and the position of the BDC through counting analysis of the MCU and feeding back so as to control the ripple motor.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and in particular to a filter system for BDC ripple detection. Background Art

[0002] With the continuous development of modern small motors, the demand for position memory of seats, windows, sliding doors, mirrors, lift gates and other motors driven by the motor is also increasing. BDC includes stator magnets and armature windings. A magnetic field is generated in the BDC by supplying DC current to the armature windings. The magnetic field interacts with the stator magnets to generate torque to rotate the armature, and then the armature provides the original power through the rotation of the output shaft.

[0003] Existing solutions utilize multiple magnetic sensors attached to the BDC body to provide a feedback loop for the motor control module, and in some cases additional sensors have certain requirements for the BDC, and connectors and cables are also required to feed signals to the motor control module, which increases the complexity and cost of the BDC. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a filter system for BDC ripple detection while avoiding the increase of complexity and cost of BDC.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] A filter system for BDC ripple detection, comprising:

[0007] Ripple motor;

[0008] A current sensing amplifier for sensing a ripple signal generated by a ripple motor;

[0009] A filter, used for filtering and amplifying a ripple signal sensed by the current sensing amplifier;

[0010] MCU central processing unit, which counts, analyzes and controls the operation of the ripple motor;

[0011] Comparator, used to provide the MCU with the rising and falling edges of the 3.3V digital logic level series;

[0012] LDO linear regulator, used to provide a stable 3.3V or 5V voltage.

[0013] In a preferred embodiment of the present invention, the ripple frequency of the ripple motor is 100 Hz to 1600 Hz; when operating under no-load conditions, the ripple current amplitude is greater than 0.5 A; the ripple build-up time is t, and t<50 ms; the waveform of the ripple current is a sine wave;

[0014] If the main harmonic of the ripple current frequency amplitude is 0dB, the amplitude of the remaining harmonics is less than -6dB; when the ripple current is the fundamental frequency, the fundamental frequency fn and the first harmonic 2fn account for the percentage of the total ripple energy The fundamental frequency fn accounts for the percentage of the total ripple energy

[0015] In a preferred embodiment of the present invention, the current sensing amplifier is connected to a sampling resistor and senses the current of the ripple motor through a low-end MOS current acquisition method, and the input end of the sampling resistor is connected to a common-mode RC input filter that can reduce noise.

[0016] In a preferred embodiment of the present invention, the filter comprises an analog filter, and the analog filter comprises an active bandpass filter connected to the output terminal of the current sensing amplifier and used for removing noise and DC component variance.

[0017] In a preferred embodiment of the present invention, the cut-off frequency of the active band-pass filter stage is 100 Hz to 1300 Hz, and the output end of the active band-pass filter is externally connected to a differential amplifier for DC bias adjustment.

[0018] In a preferred embodiment of the present invention, a comparator circuit is further included, and the comparator circuit includes an operational amplifier, R1 and R2 respectively connected to the input terminals of the operational amplifier, and R3 connected between the output terminal of the operational amplifier and ground.

[0019] In a preferred embodiment of the present invention, the influence of noise on the comparator input is reduced by using a reverse hysteresis topology, and the DC threshold of the hysteresis is:

[0020]

[0021] In a preferred embodiment of the present invention, the filter includes a digital filter, the digital filter includes a low-pass filter and a band-pass filter, and the low-pass filter and the band-pass filter are connected in series.

[0022] In a preferred embodiment of the present invention, the low-pass filter implementation includes 5 multipliers, 4 adders, and 2 states; the band-pass filter includes 3 multipliers, 3 adders, and 2 states.

[0023] In a preferred embodiment of the present invention, the cut-off frequency of the low-pass filter is 1300 Hz, and the order is 2; the cut-off frequency of the band-pass filter is 100 Hz to 1300 Hz, and the order is 2.

[0024] The beneficial effects of the present invention are as follows: the filter system includes a DC power supply, a ripple motor, a current sensing amplifier, a filter, an MCU central processing unit, a comparator and an LDO linear regulator. Based on the current ripple count in the steady-state stage of startup operation, the operating state of the ripple motor is determined according to the determined ripple period and frequency, and the operating speed and position of the ripple motor are calculated by the current ripple quantity; at the same time, the ripple quantity in the operating stage is determined in analog or digital logic, thereby replacing the method of providing a feedback loop for the motor control module through multiple magnetic sensors attached to the BDC body, thereby avoiding the complexity and cost increase of the BDC. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a framework diagram of the filter system of the present invention;

[0026] Figure 2 It is a relationship diagram of the content amplitude of other harmonics when the ripple current of the ripple motor is the fundamental frequency;

[0027] Figure 3 is a current sensing circuit diagram of the present invention;

[0028] Figure 4 is a filter circuit diagram of the present invention;

[0029] Figure 5 is a comparator circuit diagram of the present invention;

[0030] Figure 6 is a circuit diagram of a filter system of the present invention;

[0031] Figure 7 It is a waveform diagram of the ripple signal extracted by the present invention;

[0032] Figure 8 is a response diagram of the amplitude response and phase of the low-pass filter of the present invention;

[0033] Fig. 9 is a schematic diagram of the ripple current waveform before and after low-pass filtering of the present invention;

[0034] Fig.10 is a response diagram of the amplitude response and phase of the bandpass filter of the present invention;

[0035] Fig.11 is a schematic diagram of the ripple current waveform before and after the bandpass filtering of the present invention;

[0036] Fig.12 It is a digital discrete model diagram of the low-pass filter of the present invention;

[0037] Fig.13 It is a digital discrete model diagram of the bandpass filter of the present invention. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0039] Reference Figures 1 to 13 , a filter system for BDC ripple detection, comprising:

[0040] A DC power supply for providing power;

[0041] Ripple motor (BDC), with an even number of commutators;

[0042] A current sensing amplifier for sensing a ripple signal generated by a ripple motor;

[0043] A filter, used for filtering and amplifying a ripple signal sensed by the current sensing amplifier;

[0044] MCU central processing unit, which counts, analyzes and controls the operation of the ripple motor;

[0045] Comparator, used to provide the MCU with the rising and falling edges of the 3.3V digital logic level series;

[0046] LDO linear regulator, used to provide a stable 3.3V or 5V voltage.

[0047] In this way, when the ripple motor rotates, the armature commutation will cause the resistance to decrease, and the change of the armature resistance will cause current ripple. This change of impedance changes the current in a periodic pattern proportional to the actual speed of the motor. The current ripple is sensed by the current sensing amplifier of the filter system, filtered and amplified by the filter, and then converted by the comparator into a 3.3V digital logic level series of rising and falling edges (PWM wave) that can be collected by the MCU. Finally, the speed and position of the BDC can be determined through MCU counting analysis and feedback is provided to control the ripple motor.

[0048] In the present embodiment, the ripple motor is a brushed DC motor, including a stator and a rotor, and the rotor includes an armature, windings, a commutator, carbon brushes, a drive rod, etc. Compared with ordinary brushed DC motors, the ripple motor removes the Hall magnetic ring at the drive rod, which reduces the cost; and adds a filter capacitor at one end of the brush, through which the high-frequency signal generated during the rotation of the motor can be reduced or filtered out, thereby reducing unnecessary interference information in the motor current. Since the number of commutator segments is fixed, the number of ripples generated by one rotation of the motor is also fixed. Therefore, the motor position information and speed information can be obtained by reading the current ripple information. If p is the number of pole pairs, k is the number of commutator segments, n is the motor speed, and f is the current ripple frequency, then If several brushes pass through the phase changer at the same time, there is a common factor M between 2p and k, then

[0049] At the same time, in order to accurately extract the ripple current, the ripple frequency of the ripple motor is 100Hz~1600Hz; when running under no-load conditions, the ripple current amplitude is greater than 0.5A; the ripple establishment time is t, and t<50ms; the waveform of the ripple current is a sine wave;

[0050] like Figure 2 As shown, if the main harmonic of the ripple current frequency amplitude is 0dB, the amplitude of the remaining harmonics is less than -6dB; when the ripple current is the fundamental frequency, the fundamental frequency fn and the first harmonic 2fn account for a percentage of the total ripple energy The fundamental frequency fn accounts for the percentage of the total ripple energy

[0051] like Figure 1 As shown, in this scheme, an H-bridge circuit for driving a ripple motor is also included, the power supply range is 9-14V, the current sensing amplifier is connected to a sampling resistor and senses the current of the ripple motor through a low-end MOS current acquisition method to ensure the accuracy of the ripple signal. And the input end of the sampling resistor is connected to a common-mode RC input filter that can reduce the high-frequency noise and PWM switching noise generated by the motor brush.

[0052] like Figures 3 to 7 As shown, in one embodiment of the present solution, the filter includes an analog filter, and the analog filter includes an active bandpass filter connected to the output of the current sensing amplifier and used to remove noise and DC component variance. Specifically, the cutoff frequency of the active bandpass filter stage is 100Hz to 1300Hz. Since the lower limit cutoff frequency of the bandpass filter stage is configured to be approximately 100Hz, this requires a relatively large RC filter to achieve; and it also produces a huge time constant, which shows its impact on the signal during the initial spike period when the motor current is very large at startup. This current spike is large enough and slow enough not to be filtered out by the high-pass circuit, and the value of the RC time constant means that the low-frequency DC component of the signal will not quickly stabilize to a resting point. During this current spike and ripple generation, the motor begins to rotate. If this change in the effective DC bias point of the signal remains unchanged, the comparator will miss multiple ripples for counting. For this reason, a differential amplifier for DC bias adjustment is externally connected to the output of the active bandpass filter to generate a clean, low-noise AC signal for the comparator to measure.

[0053] like Figures 3 to 6As shown, the filter system circuit includes a current sensing circuit, a filter circuit and a comparator circuit connected in sequence, wherein the filter circuit also includes a differential amplifier circuit, wherein the comparator circuit includes an operational amplifier, R1 and R2 respectively connected to the input terminals of the operational amplifier, and R3 connected between the output terminal of the operational amplifier and the ground. The LDO linear regulator provides a 5V voltage to the current sensing circuit, the filter circuit and the comparator circuit, and provides a 3.3V voltage to the MCU. Therefore, after passing through the comparator, a final 0-3.3V signal will be generated, and the MCU's single-chip microcomputer will use it for counting. An open-drain output device is used to create an appropriate 3.3V level for input to a typical MCU's GPIO pin. At the same time, the reverse hysteresis topology is used to reduce the impact of noise on the comparator input, and for the reverse open-drain topology, the DC threshold of the hysteresis is:

[0054]

[0055] like Figure 7 As shown, in (a), A is the motor current curve, which is expressed in the form of voltage. When the motor starts, a large surge current will appear. After entering the running state, a relatively stable ripple current will appear. The ripple current is filtered and amplified by the filter system circuit to obtain a clean and low-noise signal. After comparison by the comparator, a square wave of 0-3.3V is output. In (b), the T1 moment is the voltage corresponding to the detection of the current ripple peak. The amplified filtered voltage and the comparator output voltage correspond to each other. For (c), the TI moment is opposite to T1 in (b). The output voltage is close to 0V. The T2 moment is the surge current, and there is an obvious large current. After the filter is conditioned, the output waveform is stable and suitable for being used as the input of the comparator. The number of square waves collected by the MCU is consistent with the number of ripples.

[0056] like Figures 8 to 13 As shown, in another embodiment of the present solution, the filter includes a digital filter, and the digital filter includes a low-pass filter and a band-pass filter, and the low-pass filter and the band-pass filter are connected in series. At the same time, the cut-off frequency of the low-pass filter is 1300Hz, and the order is 2; the cut-off frequency of the band-pass filter is 100Hz to 1300Hz, and the order is 2. In this way, the high-frequency noise in the ripple current is eliminated by the low-pass filter, so that the band-pass filter can maximize the signal-to-noise ratio of the ripple current as much as possible. Fig.11 As shown, A is the unfiltered waveform, B is the bandpass filter output waveform, that is, the extracted ripple current, and C is the pulse signal obtained by using a digital comparator based on the bandpass filter result. The number of pulses is the number of ripples extracted from the ripple current.

[0057] like Fig.12 and Fig.13As shown, through the digital discrete models of the low-pass filter and the band-pass filter, it can be known that the low-pass filter implementation includes 5 multipliers, 4 adders, and 2 states; the band-pass filter includes 3 multipliers, 3 adders, and 2 states.

[0058] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A filter system for BDC ripple detection, characterized in that: Included are: Ripple motor; A current sensing amplifier for sensing a ripple signal generated by a ripple motor; A filter, used for filtering and amplifying a ripple signal sensed by the current sensing amplifier; MCU central processing unit, which counts, analyzes and controls the operation of the ripple motor; Comparator, used to provide the MCU with the rising and falling edges of the 3.3V digital logic level series; LDO linear regulator, used to provide a stable 3.3V or 5V voltage.

2. A filter system for BDC ripple detection according to claim 1, characterized in that: The ripple frequency of the ripple motor is 100Hz-1600Hz; when operating under no-load conditions, the ripple current amplitude is greater than 0.5A; the ripple build-up time is t, and t<50ms; the waveform of the ripple current is a sine wave; If the main harmonic of the ripple current frequency amplitude is 0dB, the amplitude of the remaining harmonics is less than -6dB; when the ripple current is the fundamental frequency, the fundamental frequency fn and the first harmonic 2fn account for the percentage of the total ripple energy The fundamental frequency fn accounts for the percentage of the total ripple energy 3. A filter system for BDC ripple detection according to claim 1, characterized in that: The current sensing amplifier is connected to a sampling resistor and senses the current of the ripple motor through a low-end MOS current acquisition method. The input end of the sampling resistor is connected to a common-mode RC input filter that can reduce noise.

4. A filter system for BDC ripple detection according to any one of claims 1 to 3, characterized in that: The filter includes an analog filter, which includes an active bandpass filter connected to the output terminal of the current sensing amplifier and used for removing noise and DC component variance.

5. A filter system for BDC ripple detection according to claim 4, characterized in that: The cut-off frequency of the active band-pass filter stage is 100 Hz to 1300 Hz, and the output end of the active band-pass filter is externally connected to a differential amplifier for DC bias adjustment.

6. A filter system for BDC ripple detection according to claim 5, characterized in that: A comparator circuit is also included. The comparator circuit includes an operational amplifier, R1 and R2 respectively connected to input terminals of the operational amplifier, and R3 connected between an output terminal of the operational amplifier and ground.

7. A filter system for BDC ripple detection according to claim 6, characterized in that: The influence of noise on the comparator input is reduced by using an inverting hysteresis topology, the DC threshold of the hysteresis is:

8. A filter system for BDC ripple detection according to any one of claims 1 to 3, characterized in that: The filter includes a digital filter, and the digital filter includes a low-pass filter and a band-pass filter. The low-pass filter and the band-pass filter are connected in series.

9. A filter system for BDC ripple detection according to claim 8, characterized in that: The low-pass filter implementation includes 5 multipliers, 4 adders, and 2 states; the band-pass filter includes 3 multipliers, 3 adders, and 2 states.

10. A filter system for BDC ripple detection according to claim 8, characterized in that: The cut-off frequency of the low-pass filter is 1300 Hz, and the order is 2; the cut-off frequency of the band-pass filter is 100 Hz to 1300 Hz, and the order is 2.

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