Opto-electric cosine encoder

Abstract

The utility model discloses a kind of photoelectric cosine encoders, it is related to the field of encoder.A kind of photoelectric cosine encoder, including stator and rotor, rotor includes shaft and glass code disc, glass code disc at least contains three incremental code channels of different number of lines;Stator includes light source and PCBA, PCBA is provided with photoelectric sensor, light source driving circuit, MCU chip and conditioning circuit, light source and photoelectric sensor position correspond, light source driving circuit drives light source to emit parallel light to be received by photoelectric sensor and be output three code channel differential analog signal M, S and N with the all code channel of glass code disc being penetrated by parallel light;M signal is output differential cosine signal A after being handled by conditioning circuit and MCU chip, B;N, S signal is output differential cosine signal C after being handled by conditioning circuit and MCU chip, D;MCU chip outputs a preset width pulse signal in the one complete 360 ° rotation period of the glass code disc, and conditioning circuit outputs analog cosine signal zero position signal R.

Description

Technical Field

[0001] This utility model relates to the field of encoders, and in particular to an optoelectronic sine / cosine encoder. Background Technology

[0002] like Figure 1 A sine-cosine rotary encoder outputs A, B, C, D, and R (zero-position index, also known as the Z signal) signals. These signals allow the motor driver to calculate the motor's running position in real time and obtain position information. Typically, the A and B signals are subdivided and interpolated to obtain higher-resolution incremental angle information. C and D are sine-cosine signals with one cycle per revolution, providing a relatively coarse absolute position signal compared to A and B. Calculating the C and D signals yields absolute position information with a certain resolution within the photoelectric encoder, allowing the motor to acquire its current electrical angle information after power-on. The R signal is a zero-position signal with one cycle per revolution, facilitating rapid counting of the A and B incremental signals during movement and providing a zero-position reference.

[0003] Currently, most traditional sine and cosine encoders on the market use imported dedicated photodiodes to collect the A, B, C, D, and R signals generated by corresponding code tracks on the glass code disk. These signals are then combined with dedicated signal conditioning chips to adjust the amplitude, bias, and phase of the differentially output A, B, C, D, and R signals to ensure the output signal quality meets standards. However, this approach has significant drawbacks. The analog signals output by sine and cosine encoders have strict requirements for amplitude, phase, and bias. Therefore, traditional encoders require external oscilloscopes for observation and adjustment during assembly and debugging. The large number of signal channels and high quality requirements lead to low production efficiency, a high risk of defective products, and negatively impact end-user experience. Furthermore, the reliance on foreign proprietary chips, which are expensive, have long procurement cycles, and incur high after-sales costs, severely restricts the localization of core components. Summary of the Invention

[0004] To address the aforementioned problems, this utility model provides an optoelectronic sine / cosine encoder to solve these issues.

[0005] This utility model provides a photoelectric sine and cosine encoder, including a stator and a rotor. The rotor includes a rotating shaft and a glass code disk, the glass code disk containing at least three incremental code tracks with different numbers of engravings. The stator includes a light source and a PCBA. The PCBA is equipped with a photoelectric sensor, a light source driving circuit, an MCU chip, and a conditioning circuit. The light source driving circuit is electrically connected to the light source, the photoelectric sensor is electrically connected to the conditioning circuit, and the MCU chip forms an electrical connection loop with the light source driving circuit and the conditioning circuit respectively. The light source and the photoelectric sensor are positioned correspondingly. The photoelectric sensor includes at least three analog code track scanning channels. The light source driving circuit drives the light source to emit parallel light that passes through all the code tracks of the glass code disk and is received by the photoelectric sensor. The photoelectric sensor outputs three-track differential analog signals M, N, and S. The M, N, and S signals are processed by the conditioning circuit and the MCU chip to output analog sine and cosine signals A, B, C, and D. The MCU chip outputs a pulse signal of a preset width within one complete 360° rotation cycle of the glass code disk, and outputs a pulse zero-position signal R after being processed by the conditioning circuit.

[0006] Preferably, the output current intensity of the light source driving circuit is adjusted by the PWM signal output by the MCU chip.

[0007] Preferably, the glass code disk further includes two absolute code tracks that divide the code disk into four sections, and the photoelectric sensor further includes two digital code track scanning channels. The photoelectric sensor receives the optical signals from the two absolute code tracks and outputs two orthogonal square wave signals MTA and MTB.

[0008] Preferably, the resolution of the ADC module built into the MCU chip is 12 bits or higher.

[0009] Preferably, the conditioning circuit includes a differential amplifier unit, which converts the N and S signals output by the photovoltaic cell into single-ended signals of appropriate amplitude before inputting them into the MCU chip.

[0010] Preferably, the conditioning circuit includes a fixed gain and bias adjustment unit, which controls the differential amplification factor of the M signal by the modulation signal output from the PWM port (or DAC) of the MCU chip, and controls the bias of the M single-ended signal to be stabilized at 1 / 2 of the ADC reference voltage.

[0011] Preferably, the conditioning circuit includes a differential amplifier and filter unit to convert the C and D signals into differential signals.

[0012] Preferably, the conditioning circuit includes an attenuation and differential output unit, which attenuates the A and B signals and converts them into differential signals.

[0013] Preferably, the MCU chip counts the quadrature square wave of the M signal after it has been shaped by a comparator through the QEP module, and outputs a pulse signal of a preset width within a complete 360° rotation cycle. The pulse signal is converted into a differential signal R by the differential amplification and filtering unit included in the conditioning circuit, and its common-mode bias is consistent with that of the A, B, C, and D signals. Attached Figure Description

[0014] Figure 1 It is existing technology.

[0015] Figure 2 This is a schematic diagram of a photoelectric sine / cosine encoder circuit.

[0016] Figure 3 This is a schematic diagram of a portion of the circuitry of an optoelectronic sine / cosine encoder.

[0017] Figure 4-Figure 4d This is a schematic diagram of another part of the circuit of a photoelectric sine / cosine encoder.

[0018] Figures 5a-5c This is a schematic diagram of another part of the circuit of a photoelectric sine / cosine encoder.

[0019] Figures 6a-6b This is a schematic diagram of another part of the circuit of a photoelectric sine / cosine encoder. Detailed Implementation

[0020] The utility model will be further described in detail below with reference to the accompanying drawings.

[0021] An embodiment of the utility model discloses an optoelectronic sine / cosine encoder. Figure 2This is a block diagram for this example. Its basic operation is as follows: the light source driving circuit 23 drives the light source 22 to emit light. The light source 22 is an LED with a built-in lens, capable of emitting parallel light. The glass code disk 11 rotates with the shaft, and the parallel light simultaneously illuminates all the code tracks on the glass code disk 11, then shines through the glass code disk 11 onto the corresponding photocell 21. The photocell 21 acts as a photoelectric sensor to receive the light signal. The glass code disk 11 has three incremental code tracks (with 2048, 2046, and 1984 lines respectively) and two absolute code tracks (dividing the code disk into four sections). The photocell 21 has three analog code track scanning channels and two digital code track scanning channels. After receiving changes in the brightness of the light signal, it outputs analog sine and cosine signals M, N, and S generated by the incremental code tracks, and orthogonal square wave signals MTA and MTB generated by the absolute code tracks. In the scanning count of photovoltaic cell 21, M / N / S is 2x1024 / 1023 / 992CPR, that is, the count difference between N and M is 1 within one half-cycle of rotation, and the phase difference between the two is uniquely determined within the 180° interval; the phase difference between S and M is periodically distributed throughout the 180° interval, divided into 32 intervals; at the same time, the orthogonal square wave signals MTA and MTB output within the 360° rotation cycle are used to distinguish the 180° region. The signal processing process output by photovoltaic cell 21 is as follows: analog signals M, N, and S are acquired by the 12-bit ADC built into the MCU chip. After digital signal conversion, the rotation angle is calculated in the MCU chip 24 by means of arctangent method or PLL phase-locked loop, and then the corresponding phase difference is obtained; digital signals MTA and MTB are input through the I / O port of the MCU chip. Combined with their quadrant information, the absolute position information of a single turn can be obtained. Based on the single-turn absolute position information, the PWM port (or DAC) of the MCU chip 24 is low-pass filtered and inversely converted into sine and cosine analog signals C (C-Sin) and D (D-Cos) for output. To improve anti-interference, these two signals are processed by the first differential amplifier and filter unit 254 of the conditioning circuit to generate differential signals C-Sin-, C-Sin+ and D-Cos-, D-Cos+. To quickly calculate the position information of a single loop, after determining the absolute position of the initial single loop, the subsequent step only requires converting the orthogonal analog signal of the M code channel into a square wave signal, and then using the QEP module (Quadrature Encoder Pulse module) built into the MCU chip 24 to obtain the incremental position information. Since the M, N, and S analog signals are differential signals, and the MCU chip 24 only supports single-ended ADC input, the N and S signals need to be processed by the first and second differential amplification units 251 of the conditioning circuit to convert them into single-ended signals of appropriate amplitude before being input to the corresponding ADC peripheral I / O port of the MCU chip 24. The M signal is first differentially amplified into a single-ended signal by the fixed gain and bias adjustment unit 252 of the conditioning circuit and input to the ADC and comparator input terminals of the MCU chip 24. It is compared with the target signal to generate a modulation signal to control the conditioning circuit to adjust the differential amplification factor and bias voltage. After the bias is adjusted, the M signal is attenuated by the differential output unit 253 of the conditioning circuit and outputs A signal (A-Sin- and A-Sin+) and B signal (B-Cos- and B-Cos+). Furthermore, the reference voltage output by the DAC can stabilize the bias of the M single-ended signal at half the ADC reference voltage (i.e., 1.65V, corresponding to a reference voltage of 3.3V). Specifically, the MCU chip 24 internally acquires the peak and valley values ​​of the M signal, calculates the M channel bias voltage of the photovoltaic cell 21, and then outputs the signal through the PWM port (or DAC). The bias adjustment circuit in the fixed gain and bias adjustment unit 252 biases the differential-to-single-ended signal to 1.65V. Since the sine and cosine analog output encoder requires a bias of 2.5V and a peak-to-peak value of 1V, the 2.5V voltage needs to be attenuated, and the 1.65V bias is converted to 2.5V and then converted into differential information output. To ensure that the peak-to-peak values ​​of signals A and B are stable and reach the desired values, the brightness of light source 22 needs to be dynamically adjusted: increase the brightness when the peak-to-peak value is too small, and decrease the brightness when it is too large. Specifically, MCU chip 24 acquires the analog signal M through the ADC peripheral and converts it into a digital signal. It monitors the amplitude of the output M signal through formula (1), and then adjusts the current output of the light source driving circuit through the PWM port (or DAC) so that the peak-to-peak value of the single-ended analog signal M is 2.5V. The PWM wave generated by the MCU chip is converted into a DC adjustment quantity through a two-stage RC low-pass filter, which is used to control the driving current of transistor Q1. The driving circuit of the light source is shown in the figure. Figure 3 .

[0022] (1) In the formula, Vscq represents the amplitude corresponding to the target M that needs to be controlled, VPSOUT and VNSOUT represent the sinusoidal differential positive and differential negative analog signals of M, and VPCOUT and VNCOUT represent the cosine differential positive and differential negative analog signals of M. The output circuit principle of signals A and B is as follows: Figure 4 As shown ( Figure 4 (This is the schematic diagram of one of the paths). Figure 4aIn the process, the PWM_Cos generated by the MCU chip 24 is converted into a DC PWM_Cos_REF through a second-order low-pass filter circuit and connected to... Figure 4b R8 and C30 are used as bias points for the differential amplifier circuit, biasing the output Cos_M_U to 1.65V. Cos_M_U is connected to both the AD port corresponding to MCU chip 24 for analog-to-digital conversion and the internal comparator peripheral I / O port to shape the analog signal into a square wave. This square wave signal is then connected to the corresponding QEP unit inside the MCU chip for quadrature pulse counting. Simultaneously, Cos_M_U is connected to... Figure 4 c and Figure 4d In this process, the overall bias is transformed to 2.5V, becoming a differential output of BCos+ and BCos-, and the differential peak-to-peak value is controlled to 1V by a fixed attenuation coefficient. The C and D analog signal output circuits are shown in Figure 5 (Figure 5 shows one of the schematic diagrams). The MCU chip 24 transforms the internally calculated single-turn absolute position information into Sinwt and Coswt, which are then converted into corresponding analog amplitude outputs via the DAC peripheral (DA1_C in the figure connects to the corresponding interface of the MCU chip, corresponding to the amplitude of Sinwt). DA1_C is also connected to... Figure 5b and Figure 5c It is converted into differential C-Sin+ and C-Sin- outputs, with the output bias fixed at 2.5V, and the differential peak-to-peak value is made 1V by configuring the gain. Since the M-track of photovoltaic cell 21 has 2048 lines, 8192 count values ​​can be obtained through the QEP module within a 360° rotation cycle. Therefore, one R pulse is output every 8192 pulses. Because the sine / cosine analog output encoder has requirements on the amplitude of the R signal and requires differential output, the pulse signal output by MCU chip 24 is converted according to the circuit shown in Figure 6: the R signal in Figure 6 is connected to the I / O port of MCU chip 24, and is periodically output by MCU chip 24 according to the QEP count. The 3.3V pulse signal is then... Figure 6a and Figure 6b The circuit converts the output into differential R+ and R- signals, with the bias fixed at around 2.5V. Compared with traditional sine and cosine encoders, the photoelectric sine and cosine encoder provided by this utility model has advantages such as reducing hardware costs, improving procurement flexibility, ensuring signal compatibility and output accuracy, improving design flexibility and functional expandability, and ensuring signal output stability and reliability. The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are within its protection scope. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within its protection scope.

Claims

1. A photoelectric sine / cosine encoder, comprising a stator and a rotor, characterized in that, The rotor includes a rotating shaft and a glass code disk, the glass code disk containing at least three incremental code tracks with different numbers of engraving lines; The stator includes a light source and a PCBA. The PCBA is equipped with a photoelectric sensor, a light source driving circuit, an MCU chip, and a conditioning circuit. The light source driving circuit is electrically connected to the light source, and the photoelectric sensor is electrically connected to the conditioning circuit. The MCU chip forms an electrical connection loop with the light source driving circuit and the conditioning circuit respectively. The light source and the photoelectric sensor are positioned correspondingly. The photoelectric sensor includes at least three analog code track scanning channels. The light source driving circuit drives the light source to emit parallel light that passes through all the code tracks of the glass code disk and is received by the photoelectric sensor. The photoelectric sensor outputs three-code track differential analog signals M, N, and S. The differential analog signals M, N, and S are processed by the conditioning circuit and the MCU chip to output analog sine and cosine signals A, B, C, and D; the MCU chip outputs a pulse signal of a preset width within one complete 360° rotation cycle of the glass code disk, and outputs a pulse zero-position signal R through the conditioning circuit.

2. A photoelectric cosine encoder according to claim 1, characterized in that The output current intensity of the light source driving circuit is adjusted by the PWM signal output by the MCU chip.

3. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The glass code disk also includes two absolute code tracks that divide the code disk into four sections. The photoelectric sensor also includes two digital code track scanning channels to receive the optical signals from the two absolute code tracks and output two orthogonal square wave signals MTA and MTB.

4. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The MCU chip has a built-in ADC module with a resolution of 12 bits or higher.

5. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The conditioning circuit includes a differential amplifier unit, which converts the N and S signals output by the photovoltaic cell into single-ended signals of appropriate amplitude before inputting them into the MCU chip.

6. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The conditioning circuit includes a fixed gain and bias adjustment unit, which adjusts the differential amplification factor of the M signal by controlling the modulation signal output from the PWM port of the MCU chip or the DAC, and controls the bias of the M single-ended signal to be stabilized at 1 / 2 of the ADC reference voltage.

7. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The conditioning circuit includes a differential amplifier and filter unit that converts C and D signals into differential signals.

8. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The conditioning circuit includes an attenuation and differential output unit, which attenuates the A and B signals and converts them into differential signals.

9. A photoelectric sine-cosine encoder according to claim 1, characterized in that, The MCU chip counts the quadrature square wave of the M signal after it has been shaped by a comparator through the QEP module, and outputs a pulse signal of a preset width within a complete 360° rotation cycle. The pulse signal is converted into a differential signal R by the differential amplification and filtering unit included in the conditioning circuit, and its common mode bias is consistent with that of the A, B, C, and D signals.

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