Motor position encoder signal anti-interference transmission circuit and rotor position detection method

Abstract

The application discloses a motor position encoder signal anti-interference transmission circuit and a rotor position detection method, and the circuit comprises an encoder mainboard and a direct-current brushless motor controller; the encoder mainboard comprises an encoder processing chip, an encoder coprocessor single-chip microcomputer, a coil module and a rotor position code disc, and the rotor position code disc and the coil module are coaxially and oppositely arranged; the rotor position detection method comprises the following contents: the encoder processing chip obtains a rotor position angle value through the rotor position code disc and the coil module, the encoder coprocessor single-chip microcomputer performs signal transformation on the rotor position angle value, a differential PWM signal containing the current rotor position angle value is transmitted to the direct-current brushless motor controller through an encoder transmission cable, and the position feedback of the brushless motor rotor is completed by the direct-current brushless motor controller. The application can accurately feed back the rotor angle position signal to the direct-current brushless motor controller, has strong stability, strong anti-interference and robustness, and is suitable for various electric vehicle operating environments.

Description

Technical Field

[0001] This invention relates to motor signal transmission circuits, specifically to an anti-interference transmission circuit for a position encoder signal of an electric vehicle motor, and also to a method for detecting the position of a motor rotor. Background Technology

[0002] Currently, electric two-wheelers and three-wheelers powered by battery packs all use brushless DC motors as their power output. Brushless DC motors require a matching brushless DC motor controller to operate. Typically, three Hall effect sensors are installed inside the brushless DC motor to feed back the rotor angle position signal to the brushless DC motor controller.

[0003] The brushless DC motor controller supplies power to three Hall elements installed inside the motor via signal lines. The rotor position signal detected by the Hall elements is then transmitted to the brushless DC motor controller via signal lines.

[0004] When electric two-wheelers and three-wheelers are in harsh operating environments such as high vibration, high temperature, high humidity, high dust, and salt and alkali corrosion, the Hall signal lines that transmit rotor position are easily damaged, leading to poor signal transmission. This causes the DC brushless motor controller to fail to output the correct control current, resulting in overcurrent faults and shutdowns, or even serious consequences such as burning out the DC brushless motor controller. The entire electric two-wheeler and three-wheeler industry faces this problem, which has not yet been resolved, resulting in a high product return rate. Summary of the Invention

[0005] Purpose of the invention: In order to solve the problems existing in the prior art, the purpose of this invention is to provide a safe and reliable anti-interference transmission circuit for electric vehicle motor position encoder signals. Another purpose of this invention is to provide a rotor position detection method that can quickly and accurately acquire motor rotor position signals.

[0006] Technical Solution: A signal anti-interference transmission circuit for a motor position encoder includes an encoder mainboard and a DC brushless motor controller, which are connected by an encoder transmission cable. The encoder mainboard includes an encoder processing chip, an encoder co-processor microcontroller, a coil module, and a rotor position code disk. The rotor position code disk and the coil module are placed coaxially opposite each other. Optionally, the rotor position code disk is a ring-shaped printed circuit board or a metal code disk. The DC brushless motor controller includes a main control microcontroller with a built-in comparator. The positive terminal of the PWM signal of the encoder co-processor microcontroller is connected to the positive terminal of the comparator, and the negative terminal of the PWM signal of the encoder co-processor microcontroller is connected to the negative terminal of the comparator.

[0007] Furthermore, the coil module includes an excitation coil, a sine receiving coil, and a cosine receiving coil; the sine receiving coil and the cosine receiving coil are arranged radially and evenly alternatingly inside the excitation coil; the diameter of the circle enclosed by the sine receiving coil and the cosine receiving coil is adapted to the outer diameter of the rotor position code disk; the positive terminal of the resonant signal of the encoder processing chip is connected to the positive input terminal of the excitation coil, and the negative terminal of the resonant signal of the encoder processing chip is connected to the negative input terminal of the excitation coil; the negative input terminal of the sensor cosine of the encoder processing chip is connected to the negative input terminal of the cosine receiving coil, the positive input terminal of the sensor cosine of the encoder processing chip is connected to the positive input terminal of the cosine receiving coil, the negative input terminal of the sensor sine of the encoder processing chip is connected to the negative input terminal of the sine receiving coil, and the positive input terminal of the sensor sine of the encoder processing chip is connected to the positive input terminal of the sine receiving coil.

[0008] Furthermore, the encoder transmission cable includes a first encoder transmission cable and a second encoder transmission cable; the encoder mainboard also includes a first signal current differential transmission resistor R6 and a second signal current differential transmission resistor R7; the DC brushless motor controller includes a third signal current differential transmission resistor R8, a fourth signal current differential transmission resistor R10, and a fifth signal current differential transmission resistor R11, wherein the third signal current differential transmission resistor R8 is disposed between the first encoder transmission cable and the second encoder transmission cable; the positive terminal of the PWM signal of the encoder coprocessor microcontroller is connected to the positive terminal of the comparator via the first signal current differential transmission resistor R6, the first encoder transmission cable, and the fourth signal current differential transmission resistor R10, and the negative terminal of the PWM signal of the encoder coprocessor microcontroller is connected to the negative terminal of the comparator via the second signal current differential transmission resistor R7, the second encoder transmission cable, and the fifth signal current differential transmission resistor R11.

[0009] Furthermore, the brushless DC motor controller also includes an upper bias resistor R12; the lower end of the third signal current differential transmission resistor R8 is connected to the second encoder transmission cable, and forms an upper bias circuit through the first bias resistor R12 to the +5V voltage. The brushless DC motor controller also includes a lower bias resistor R13; the upper end of the third signal current differential transmission resistor R8 is connected to the first encoder transmission cable, and forms a lower bias circuit through the second bias resistor R13 to the GND voltage.

[0010] Furthermore, the encoder motherboard also includes a first single-wire communication receiving signal transmission resistor R5, and the DC brushless motor controller also includes a second single-wire communication receiving signal transmission resistor R9; the encoder transmission cable also includes a third encoder transmission cable; the single-wire communication receiving port of the encoder processing chip is connected to the single-wire communication transmitting port of the main control microcontroller via the first single-wire communication receiving signal transmission resistor R5, the third encoder transmission cable and the second single-wire communication receiving signal transmission resistor R9.

[0011] More preferably, an anti-interference capacitor is provided between the encoder transmission cable and ground.

[0012] A rotor position detection method based on the anti-interference transmission circuit of the motor position encoder signal includes the following steps:

[0013] (1) The encoder processing chip obtains the rotor position angle value through the rotor position code disk and coil module, and sends it to the encoder coprocessor microcontroller;

[0014] (2) The encoder coprocessor microcontroller performs signal transformation on the rotor position angle value and outputs a differential PWM signal containing the current rotor position angle value, which is transmitted to the DC brushless motor controller through the encoder transmission cable.

[0015] (3) The comparator of the main control microcontroller compares the positive and negative PWM current signals. The output of the comparator is flipped into a PWM duty cycle signal containing the current rotor position angle value. The main control microcontroller captures the duty cycle of the signal to complete the position feedback of the brushless motor rotor.

[0016] Furthermore, step (1) specifically includes the following:

[0017] (1.1) The encoder processing chip outputs the excitation current to the excitation coil. The sine receiving coil and the cosine receiving coil receive the sine current and cosine current transmitted from the rotor position code disk and send them to the encoder processing chip.

[0018] (1.2) The encoder processing chip performs calculations on the sine current and cosine current to obtain the rotor position angle value, and sends the rotor position angle value to the encoder coprocessor microcontroller through the SPI communication port.

[0019] The beneficial effects of the present invention are: compared with the prior art, the circuit structure of the present invention can accurately transmit the rotor angle position signal to the DC brushless motor controller, and has strong stability, strong anti-interference and robustness, and is suitable for various operating environments of electric vehicles. Attached Figure Description

[0020] Figure 1 This is a diagram showing the electrical component connections according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the excitation coil, the sine receiving coil, and the cosine receiving coil;

[0022] Figure 3 This is a schematic diagram of the rotor position encoder.

[0023] Figure 4 This is a diagram showing the adaptation of the rotor position encoder relative to the excitation coil, sine receiving coil, and cosine receiving coil. Detailed Implementation

[0024] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, an anti-interference transmission circuit for a position encoder signal of an electric vehicle motor includes an encoder mainboard 1 and a DC brushless motor controller 2, which are connected by an encoder transmission cable 3. In this embodiment, the encoder transmission cable 3 consists of a built-in 5-core signal line (encoder transmission cable line 1, encoder transmission cable line 2, encoder transmission cable line 3, encoder transmission cable line 4, and encoder transmission cable line 5).

[0026] The encoder mainboard 1 consists of an encoder processing chip IC1 (preferably an SC60340 chip), an encoder coprocessor microcontroller IC2 (preferably an LKS32MC082K6Q8 chip), an excitation coil L2, a sine receiving coil L1, a cosine receiving coil L3, resonant capacitors C4 and C5, filter capacitors C1, C2, and C3 for IC1 chip, SPI communication transmission resistors R1, R2, R3, and R4 for IC1 and IC2 chips, a first signal current differential transmission resistor R6, a second signal current differential transmission resistor R7, and a single-wire communication receiving signal transmission resistor R5. The encoder mainboard also includes a rotor position code disk that rotates synchronously with the motor rotor and has the same number of pole pairs as the rotor. Optionally, the rotor position code disk is made from a ring-shaped PCB (printed circuit board) or a metal code disk.

[0027] like Figure 2 , Figure 3 , Figure 4 As shown, the sine receiving coil L1 and the cosine receiving coil L3 are arranged radially and evenly alternately inside the excitation coil L2. The rotor position code disk and the circular plane containing the excitation coil, the sine receiving coil and the cosine receiving coil are placed coaxially opposite each other. The diameter of the circle enclosed by the sine receiving coil and the cosine receiving coil is basically equal to the outer diameter of the rotor position code disk.

[0028] Specifically, the OSCP terminal of the IC1 chip is connected to the OSCP terminal of the excitation coil, and the OSCN terminal of the IC1 chip is connected to the OSCN terminal of the excitation coil. The SNCOS terminal of the IC1 chip is connected to the INCOS terminal of the cosine receiving coil, the SPCOS terminal of the SC60340 chip is connected to the IPCOS terminal of the cosine receiving coil, the SNSIN terminal of the IC1 chip is connected to the INSIN terminal of the sine receiving coil, and the SPSIN terminal of the IC1 chip is connected to the IPSIN terminal of the sine receiving coil.

[0029] Furthermore, the DC brushless motor controller 2 consists of a main control microcontroller IC3 (LKS32MC081C8T8 chip), a third signal current differential transmission resistor R8, a fourth signal current differential transmission resistor R10, a fifth signal current differential transmission resistor R11, an upper bias resistor R12, a lower bias resistor R13, a single-wire communication receiving signal transmission resistor R9, etc.

[0030] PIN18 (MCPWM_CH0P / P1.4) of IC2 chip is connected to PIN13 (CMP0_IP1 / P0.11) of IC3 chip via the first signal current differential transmission resistor R6, encoder transmission cable line 3, and the fourth signal current differential transmission resistor R10; PIN19 (MCPWM_CH0N / P1.5) of IC2 chip is connected to PIN17 (CMP0_IN1 / P0.15) of IC3 chip via the second signal current differential transmission resistor R7, encoder transmission cable line 4, and the fifth signal current differential transmission resistor R11.

[0031] The third signal current differential transmission resistor R8 is located between encoder transmission cable line 3 and encoder transmission cable line 4. The lower end of R8 is connected to encoder transmission cable line 4 and forms an upper bias circuit through the upper bias resistor R12 to +5V voltage. The upper end of R8 is connected to encoder transmission cable line 3 and forms a lower bias circuit through the lower bias resistor R13 to GND voltage.

[0032] A rotor position detection method based on the above-mentioned anti-interference transmission circuit for motor position encoder signals includes the following:

[0033] Step 1: The encoder processing chip obtains the rotor position angle value through the rotor position code disk and coil module, and sends it to the encoder coprocessor microcontroller.

[0034] Step 2: The encoder coprocessor microcontroller performs signal transformation on the rotor position angle value and outputs a differential PWM signal containing the current rotor position angle value, which is transmitted to the DC brushless motor controller through the encoder transmission cable.

[0035] Step 3: The comparator of the main control microcontroller compares the positive and negative PWM current signals. The comparator output is flipped into a PWM duty cycle signal containing the current rotor position angle value. The main control microcontroller captures the duty cycle of the signal to complete the position feedback of the brushless motor rotor.

[0036] The details are as follows:

[0037] The encoder processing chip IC1 outputs excitation current to the excitation coil L2 through the OSCP and OSCN terminals. The sine receiving coil L1 and cosine receiving coil L3 receive the sine and cosine currents transmitted through the rotor position code disk and send them to pins 7, 8, 9, and 10 of the encoder processing chip IC1. After processing the signal, the encoder processing chip IC1 sends the obtained rotor position angle value to the encoder coprocessor microcontroller IC2 chip through the SPI communication port for signal conversion. The differential PWM signal output by the encoder coprocessor microcontroller IC2 chip after conversion contains the current rotor position angle value.

[0038] After the rotor position angle value is converted into a differential PWM signal, the encoder processing chip IC2 outputs PWM+ current through PIN18 (MCPWM_CH0P / P1.4), which enters the first signal current differential transmission resistor R6, encoder transmission cable line 3, third signal current differential transmission resistor R8, encoder transmission cable line 4, and second signal current differential transmission resistor R7, before returning to the IC2 chip's PIN19 (MCPWM_CH0N / P1.5) port; a current signal with positive at the top and negative at the bottom is formed on the third signal current differential transmission resistor R8.

[0039] The PWM current output from PIN19 (MCPWM_CH0N / P1.5) of the IC2 chip enters the second signal current differential transmission resistor R7, encoder transmission cable line 4, the third signal current differential transmission resistor R8, encoder transmission cable line 3, and the first signal current differential transmission resistor R6, before returning to the PIN18 (MCPWM_CH0P / P1.4) port of the IC2 chip, forming a current signal with negative on top and positive on the bottom in the third signal current differential transmission resistor R8.

[0040] A differential PWM signal containing the current rotor position angle value is transmitted to the DC brushless motor controller via the encoder transmission cable.

[0041] The PWM+ current signal at the upper end of the third signal current differential transmission resistor R8 is transmitted to PIN13 (CMP0_IP1 / P0.11) of IC3 chip via the fourth signal current differential transmission resistor R10.

[0042] The PWM-current signal at the lower end of the third signal current differential transmission resistor R8 is transmitted to PIN17 (CMP0_IN1 / P0.15) of IC3 chip via the fifth signal current differential transmission resistor R11.

[0043] The main control microcontroller IC3 chip of the DC brushless motor controller has its PIN13 (CMP0_IP1 / P0.11) configured as the non-inverting input of the comparator, its PIN17 (CMP0_IN1 / P0.15) configured as the inverting input of the comparator, its PIN16 (CMP0_OUT / P0.14) configured as the output of the comparator, its PIN33 (TIM0_CH0 / P1.10) configured as the high-level trigger input of the timer, and its PIN34 (TIM0_CH1 / P1.11) configured as the low-level trigger input of the timer.

[0044] The comparator compares the positive and negative PWM current signals at the upper and lower ends of the third signal current differential transmission resistor R8, and the output is flipped into a PWM duty cycle signal containing the current rotor position angle value. This signal is directly transmitted to PIN33 (TIM0_CH0 / P1.10) and PIN34 (TIM0_CH1 / P1.11) of the main control single-chip microcomputer IC3 of the DC brushless motor controller to capture the duty cycle and complete the position feedback of the brushless motor rotor.

[0045] Since the current signal on resistor R8 is transmitted differentially from the encoder motherboard, it has strong common-mode rejection capability, which can effectively resist external interference, thereby improving the system's stability and anti-interference capability.

[0046] Secondly, because an upper bias resistor R12 is set at the lower end of resistor R8 and a lower bias resistor R13 is set at the upper end of resistor R8, bias voltages are formed at both ends. If any one of the encoder transmission cable lines 3 or 4 is broken, the upper bias resistor R12 and the lower bias resistor R13 inside the DC brushless motor controller will automatically switch the differential current transmission mode to the voltage comparison mode. The system signal redundancy design significantly improves the system robustness.

[0047] The encoder mainboard also includes a first single-wire communication signal receiving and transmission resistor R5, and the DC brushless motor controller also includes a second single-wire communication signal receiving and transmission resistor R9. The single-wire communication signal output from PIN14 (P0.12) of the DC brushless motor controller main control microcontroller IC3 is transmitted through R9 and R5 to the PIN1 (P0.0) port of the encoder co-processing microcontroller IC2 for operations such as sensor signal amplitude calibration and rotor position zeroing. Encoder interface anti-interference filter capacitors C6, C7, and C8 are also provided between encoder transmission cable line 2, encoder transmission cable line 3, encoder transmission cable line 4 and ground for filtering stray signals, thereby further improving the stability of circuit operation.

Claims

1. A signal anti-interference transmission circuit for a motor position encoder, characterized in that: The system includes an encoder motherboard and a brushless DC motor controller, which are connected via an encoder transmission cable. The encoder motherboard includes an encoder processing chip, an encoder coprocessor microcontroller, a coil module, and a rotor position code disk, which are placed coaxially opposite to each other. The coil module includes an excitation coil, a sine receiving coil, and a cosine receiving coil. The sine receiving coil and cosine receiving coil are arranged radially and evenly alternatingly inside the excitation coil; the diameter of the circle enclosed by the sine receiving coil and the cosine receiving coil is adapted to the outer diameter of the rotor position encoder. The positive terminal of the resonant signal of the encoder processing chip is connected to the positive input terminal of the excitation coil, and the negative terminal of the resonant signal of the encoder processing chip is connected to the negative input terminal of the excitation coil. The encoder processing chip has its sensor cosine negative input terminal connected to the negative input terminal of the cosine receiving coil, its sensor cosine positive input terminal connected to the positive input terminal of the cosine receiving coil, its sensor sine negative input terminal connected to the negative input terminal of the sine receiving coil, and its sensor sine positive input terminal connected to the positive input terminal of the sine receiving coil. The encoder processing chip outputs an excitation current to the excitation coil. The sine receiving coil and the cosine receiving coil receive the sine current and cosine current transmitted from the rotor position code disk. The encoder processing chip performs calculations on the sine current and cosine current to obtain the rotor position angle value. The DC brushless motor controller includes a main control microcontroller with a built-in comparator; the positive terminal of the PWM signal of the encoder coprocessor microcontroller is connected to the positive terminal of the comparator, and the negative terminal of the PWM signal of the encoder coprocessor microcontroller is connected to the negative terminal of the comparator. The PWM signal is obtained by signal transformation of the rotor position angle value obtained by the rotor position code disk and the coil module.

2. The anti-interference transmission circuit for motor position encoder signals according to claim 1, characterized in that: The encoder transmission cable includes a first encoder transmission cable and a second encoder transmission cable. The encoder motherboard also includes a first signal current differential transmission resistor R6 and a second signal current differential transmission resistor R7; The DC brushless motor controller includes a third signal current differential transmission resistor R8, a fourth signal current differential transmission resistor R10, and a fifth signal current differential transmission resistor R11. The third signal current differential transmission resistor R8 is located between the first encoder transmission cable and the second encoder transmission cable. The positive terminal of the PWM signal of the encoder coprocessor microcontroller is connected to the positive terminal of the comparator via the first signal current differential transmission resistor R6, the first encoder transmission cable, and the fourth signal current differential transmission resistor R10. The negative terminal of the PWM signal of the encoder coprocessor microcontroller is connected to the negative terminal of the comparator via the second signal current differential transmission resistor R7, the second encoder transmission cable, and the fifth signal current differential transmission resistor R11.

3. The anti-interference transmission circuit for motor position encoder signals according to claim 2, characterized in that: The DC brushless motor controller also includes an upper bias resistor R12; the lower end of the third signal current differential transmission resistor R8 is connected to the second encoder transmission cable, and forms an upper bias circuit through the first bias resistor R12 to the +5V voltage.

4. The anti-interference transmission circuit for motor position encoder signals according to claim 2 or 3, characterized in that: The DC brushless motor controller also includes a lower bias resistor R13; the upper end of the third signal current differential transmission resistor R8 is connected to the first encoder transmission cable, and forms a lower bias circuit through the second bias resistor R13 to the GND voltage.

5. The anti-interference transmission circuit for motor position encoder signals according to claim 2, characterized in that: The encoder motherboard also includes a first single-wire communication signal receiving transmission resistor R5, and the DC brushless motor controller also includes a second single-wire communication signal receiving transmission resistor R9. The encoder transmission cable also includes a third encoder transmission cable; The single-wire communication receiving port of the encoder processing chip is connected to the single-wire communication transmitting port of the main control microcontroller via the first single-wire communication receiving signal transmission resistor R5, the third encoder transmission cable, and the second single-wire communication receiving signal transmission resistor R9.

6. The anti-interference transmission circuit for motor position encoder signals according to claim 1, characterized in that: An anti-interference capacitor is provided between the encoder transmission cable and ground.

7. The anti-interference transmission circuit for motor position encoder signals according to claim 1, characterized in that: The rotor position encoder uses a ring-shaped printed circuit board or a metal encoder.

8. A rotor position detection method based on the anti-interference transmission circuit of the motor position encoder signal as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) The encoder processing chip obtains the rotor position angle value through the rotor position code disk and coil module, and sends it to the encoder coprocessor microcontroller; (2) The encoder coprocessor microcontroller performs signal transformation on the rotor position angle value and outputs a differential PWM signal containing the current rotor position angle value, which is transmitted to the DC brushless motor controller through the encoder transmission cable. (3) The comparator of the main control microcontroller compares the positive and negative PWM current signals. The output of the comparator is flipped into a PWM duty cycle signal containing the current rotor position angle value. The main control microcontroller captures the duty cycle of the signal to complete the position feedback of the brushless motor rotor.

9. The rotor position detection method according to claim 8, characterized in that, Step (1) specifically includes the following: (1.1) The encoder processing chip outputs the excitation current to the excitation coil. The sine receiving coil and the cosine receiving coil receive the sine current and cosine current transmitted from the rotor position code disk and send them to the encoder processing chip. (1.2) The encoder processing chip performs calculations on the sine current and cosine current to obtain the rotor position angle value, and sends the rotor position angle value to the encoder coprocessor microcontroller through the SPI communication port.

Images