Servo motor driving circuit

Abstract

According to the servo motor drive circuit of the utility model, the input end of the power supply module is provided with a power supply module input three-stage filter circuit; the first-stage filter circuit comprises two or more capacitors connected in parallel and is used for filtering low-frequency ripples, the second-stage filter circuit comprises two or more capacitors connected in parallel and is used for filtering medium-high frequency large-energy ripples, and the third-stage filter circuit comprises one or more capacitors and is used for filtering ultrahigh-frequency ripples. The capacitance of each capacitor in the same-stage filter circuit is the same, the capacitance value of a single capacitor of the first-stage filter circuit is greater than that of a single capacitor of the second-stage filter circuit, and the capacitance value of a single capacitor of the second-stage filter circuit is greater than that of a single capacitor of the third-stage filter circuit. The problem that a power supply module of an existing servo motor driving circuit cannot be suitable for various ripple interference environments such as low frequency, medium-high frequency large energy and ultrahigh frequency at the same time is solved.

Description

Technical Field

[0001] A servo motor drive circuit relates to the field of motor drive circuits, particularly to the field of servo motor vector control. Background Technology

[0002] Servo motors are crucial components in industrial control. In robots, servo motors are an important part of the joint module, providing power and directly affecting the robot's safety and flexibility in motion due to their motion accuracy and stability.

[0003] In industrial production and daily life, the servo motors of robot joint modules typically require high output power, strong anti-interference capabilities, and flexible direction and speed control. The drive circuit is the foundation of servo motor control. Therefore, the performance of the drive circuit directly affects the motion accuracy and stability of the servo motor.

[0004] To ensure the accurate and stable operation of a servo motor drive circuit, a stable power supply is paramount. An unstable power supply will cause other power-consuming modules of the servo motor to malfunction. Therefore, the stability of the power supply module in the servo motor drive circuit is of utmost importance.

[0005] We know that capacitor filtering is affected by the capacitive reactance X of the capacitor. c =1 / (2πfC) and the influence of the capacitor charging and discharging time constant τ=RC. We also know that high-frequency ripple is filtered out through fast charging and discharging, while low-frequency ripple is smoothed through slow charging and discharging. Therefore, we choose small-value capacitors for filtering high-frequency ripple and large-value capacitors for filtering low-frequency ripple.

[0006] Generally, low-frequency ripple has high energy, while high-frequency ripple has low energy; therefore, the above-mentioned selection of capacitor values ​​for filtering ripple at different frequencies is feasible. However, for mid-to-high frequency high-energy ripple, the above solution is not feasible. This is because if we choose a capacitor with a small capacitance value, the high energy of the ripple will burn out the capacitor, or the small-capacity capacitor will not be able to completely absorb and release the high energy of the ripple in a short time. If we choose a capacitor with a large capacitance value, the charging and discharging time of the capacitor will be longer, which cannot meet the fast charging and discharging requirements of high-frequency filtering, and thus cannot filter out high-frequency high-energy ripple.

[0007] Therefore, current servo motor drive circuit power modules are only suitable for typical low-frequency, high-energy or high-frequency, low-energy interference environments, but not for special environments with medium- to high-frequency, high-energy interference. However, it is precisely in these medium- to high-frequency, high-energy interference environments that robots are urgently needed to replace human labor, thereby ensuring personnel safety (e.g., in high-frequency heating treatment production lines for metal materials).

[0008] Although the power input terminal of the power module in application number 2020229945024, entitled "A Servo Circuit Controlled by an Optical Encoder," is equipped with a power input filter circuit, it can only filter out low-frequency, high-energy or high-frequency, low-energy ripple, but not high-frequency, high-energy ripple. Similarly, the power input terminals of the driver board MCU, optical encoder, motor drive module, and RS485 communication module in this illustrated solution all have filter circuits. However, they can only filter out high-frequency, low-energy ripple, with limited filtering of high-frequency, high-energy ripple, and high-frequency, high-energy ripple can even damage the filter capacitors. Likewise, the motor drive module in this illustrated solution only has a filter circuit on the low-side drive signal, while the high-side drive signal is not. This setup is also unsuitable for high-frequency, high-energy, or strong magnetic interference conditions. Furthermore, the current sampling circuits in the listed technical solutions lack power supply regulation in their respective detection circuits, making them capable of detecting small currents. The bus current detection sampling is a summation of the currents sampled from each phase. Due to the tolerance values ​​of each detection resistor, the value detected by the bus current sampling circuit using three detection resistors will have a significant error compared to the actual value. In other words, such a drive circuit is unsuitable for high-precision applications requiring high motion accuracy and low power output (such as the assembly of precision components). This servo motor drive circuit has poor versatility, and robots manufactured using it will also lack versatility.

[0009] In summary, developing a servo motor drive circuit with high anti-interference capability and high-precision control that can adapt to all working conditions has become an urgent technical problem to be solved. Utility Model Content

[0010] To address the technical problem that existing servo motor drive circuits lack the high anti-interference and high-precision control performance to adapt to all working conditions, thus resulting in robots manufactured using them lacking versatility, this invention proposes an innovative solution.

[0011] A servo motor drive circuit includes a power supply module. The input terminal of the power supply module is equipped with a three-stage power supply input filter circuit. In order of current input, the three stages are: a first-stage filter circuit containing two or more parallel capacitors to filter low-frequency ripple; a second-stage filter circuit containing two or more parallel capacitors to filter mid-to-high frequency high-energy ripple; and a third-stage filter circuit containing one or more capacitors to filter ultra-high frequency ripple. Each capacitor in the filter circuit has the same capacitance, and the capacitance value of a single capacitor in the first-stage filter circuit is greater than that in the second-stage filter circuit, and the capacitance value of a single capacitor in the second-stage filter circuit is greater than that in the third-stage filter circuit.

[0012] Furthermore, it also includes power filtering circuits for the CAN communication module, magnetic encoder module, main control module, and drive module, all of which are filtering circuits containing two or more parallel capacitors to filter out high-frequency, high-energy ripple.

[0013] Furthermore, in the power filtering circuits of the CAN communication module, the magnetic encoder module, the main control module, and the drive module, the capacitance of the first capacitor in the direction of current input is greater than that of the second capacitor, and so on, the capacitance of each preceding capacitor is greater than that of the capacitor following it.

[0014] Furthermore, it also includes an RS485 communication module, which is a filter circuit containing two or more parallel capacitors to filter out high-frequency, high-energy ripple.

[0015] Furthermore, in the power filter circuit of the RS485 communication module, the capacitance value of the first capacitor in the direction of current input is greater than the capacitance value of the second capacitor, and so on, the capacitance value of each preceding capacitor is greater than the capacitance value of the capacitor following it.

[0016] Furthermore, it also includes an active module and a drive module, and each signal circuit that sends signals from the main control module to the drive module is equipped with a first-stage filtering circuit.

[0017] Furthermore, it also includes an inverter module and a detection module. The detection module samples any two phase currents and the total three-phase current from the three-phase current output by the inverter module. Both the random two-phase current sampling circuit and the total three-phase current sampling circuit are equipped with adjustable power supplies. The adjustable power supplies of the random two-phase current sampling circuit are equipped with clamping circuits.

[0018] Furthermore, a filter capacitor is provided between the positive and negative input terminals of the operational amplifier in each detection circuit of the detection module.

[0019] Furthermore, it also includes a temperature detection module, which is located on the PCB board area where the inverter module is located.

[0020] Furthermore, it also includes an inverter module power supply filter circuit, which is located at the power input terminal of the inverter module. The inverter module power supply filter circuit includes two or more parallel filter capacitors for filtering out high-frequency, high-energy ripple.

[0021] Beneficial effects: In order to solve the technical problems pointed out in the background art, the inventors of the present application have devised a method for calculating the parallel resistance: 1 / R 总 =1 / R1+1 / R 2， When R1=R2: R 总=R1 / n (where n is the number of parallel resistors). Similarly, it can be derived that: X C总 =X C1 / n (where n is the number of capacitors in parallel). In other words, for mid-to-high frequency, high-energy ripple, we can select multiple capacitors with matching capacitance values ​​based on the application conditions and connect them in parallel to form a filter circuit that can meet the filtering requirements for mid-to-high frequency, high-energy ripple. Furthermore, we know that each parallel filter capacitor can perform its filtering function independently; therefore, such a filter circuit can filter out ripple over a wide frequency range.

[0022] This servo motor drive circuit incorporates a three-stage power module input filter circuit. The first stage filters out low-frequency ripple; the second stage filters out mid-to-high frequency high-energy ripple, and as described above, also smooths out low-frequency ripple that the first stage failed to completely remove; the third stage filters out ultra-high frequency ripple and completely absorbs and releases mid-to-high frequency ripple that the second stage failed to completely remove. This power module exhibits high anti-interference capabilities and can adapt to various interference environments, thus ensuring high-precision control of the servo motor drive circuit under all operating conditions. Because the capacitor used to filter low-frequency ripple has a large capacitance (typically an electrolytic capacitor), it is placed in the first-stage filter circuit, allowing it to be positioned near the power interface on the board edge. The second and third stage filter capacitors are used to filter out mid-to-high frequency and ultra-high frequency ripple. Their capacitance values ​​are smaller than those of the capacitors in the first stage filter circuit (usually surface-mount ceramic or tantalum capacitors). Therefore, they can be more easily placed closer to the power chip (because the pin size of the chip is usually relatively small; if large components are placed near the chip, the wiring connecting to the chip will have to detour to avoid the space occupied by the components, which can easily generate parasitic inductance). This hierarchical arrangement of the filter circuit is beneficial for a compact PCB layout. Since the second and third stage filter circuits can be placed near the power chip, secondary interference from interference sources is avoided after filtering. At the same time, the first and second stage filter circuits have already filtered out high-energy ripple, which can prevent parasitic inductance in the power input circuit from generating a magnetic field, thereby interfering with other circuits in the servo motor drive circuit.

[0023] The power module of "A Servo Circuit Controlled by an Optical Encoder" (application number 2020229945024) has three parallel filter capacitors at its current input terminal, with capacitance values ​​of 47µF, 100nF, and 220µF respectively. The 47µF and 100nF capacitors effectively filter out low-frequency and high-frequency, low-energy ripple, respectively, but they are ineffective at filtering out mid-to-high-frequency, high-energy ripple. The 220µF capacitor can smooth out the ripple that the first two capacitors failed to completely filter, but it cannot filter out ultra-high-frequency ripple. Therefore, such a power module is not suitable for operating conditions with multiple interference sources. In contrast, the technical solution of this application has better anti-interference performance, can adapt to operating conditions with multiple interference sources, and has better versatility.

[0024] The power filtering circuits for the CAN communication module, magnetic encoder module, main control module, drive module, RS485 communication module, and inverter module in this application are all filtering circuits that include two or more parallel capacitors to filter out high-frequency, high-energy ripple. As described in the first paragraph of the "Beneficial Effects" section, this filtering circuit configuration allows the filter circuit to filter out ripple over a wide frequency range, while the multiple parallel capacitors also increase the overall capacitance of the filtering circuit. Therefore, this configuration is particularly beneficial for filtering out high-frequency, high-energy ripple, while also considering the filtering of low-frequency ripple. In the two or more parallel capacitors, the capacitance of the first capacitor in the current input direction is greater than the capacitance of the second capacitor, and so on, with each preceding capacitor having a larger capacitance than the one following it. This configuration is designed to allow the filtering circuit to better filter out low-frequency and ultra-high-frequency ripple while still possessing the ability to filter out high-frequency, high-energy ripple. The patent application No. 2020229945024, "A Servo Circuit Controlled by an Optical Encoder," also includes a filter capacitor at the power input terminal of each power module, but these are only for high-frequency, low-energy ripple. Under medium-to-high frequency, high-energy interference sources, due to the strong penetrating power of high-frequency electromagnetic waves, the interference from these sources to the power modules of the servo motor drive circuit is also very significant. The power module's filter circuit cannot completely replace the filtering function of the individual power module's filter circuit. Therefore, compared to this application, the technical solution has superior anti-interference performance, can adapt to multiple interference sources, and has better versatility.

[0025] In this application's technical solution, each signal circuit that sends signals from the main control module to the drive module is equipped with a primary filtering circuit. This is primarily to avoid situations where, under strong interference sources, only the low-side signal circuits are filtered, as in application number 2020229945024's "A Servo Circuit Controlled by an Optical Encoder," which only filters the high-side signal circuits and not the low-side signal circuits, thus failing to effectively prevent interference.

[0026] The detection module in this application samples any two phase currents and the total three-phase current output from the inverter module. Based on the working principle of the inverter circuit, it is known that the current flowing into the input terminal of one phase coil of the servo motor flows out through the output terminals of the other two phase coils. Therefore, by measuring any two phase currents and the total three-phase current, the current of the other phase can be calculated (i.e., knowing I...). U、 I W and I BUS ,I V =I BUS -I U Or I W This simplifies the detection circuit. Measuring the instantaneous current of each phase is to detect whether the motor coil is overcurrent due to unstable input power, overload, or phase loss. It provides data feedback for the safe operation of the servo motor (if the instantaneous current of a certain phase is detected to be greater than the theoretical operating current of that phase, the servo motor can be controlled to stop working and a fault code will be reported, making it easier for engineers to diagnose the fault).

[0027] Measuring the instantaneous current of the bus serves two purposes: firstly, it allows for the calculation of the instantaneous current of the other phase, simplifying the detection circuit; secondly, it allows for the calculation of the motor power by averaging multiple sampled values ​​of the bus current, rather than averaging multiple sampled values ​​of each phase and then summing the average values ​​of all phases, or averaging the summed current values ​​of all three phases multiple times. This avoids the cumulative error caused by errors from multiple detection circuits. Each detection circuit must have at least one detection resistor and one current-limiting resistor, and even without considering the detection error of the operational amplifier, these resistors have tolerances. Therefore, the servo motor power calculated by measuring the bus current using a separate detection circuit is closer to the actual value than the servo motor power calculated by measuring the current of each phase using individual phase detection circuits. Furthermore, in this application's technical solution, the current of any two phases and the total three-phase current are sampled separately, unlike the bus current detection sampling in application number 2020229945024, "A Servo Circuit Controlled by an Optical Encoder," which involves summing the currents sampled from each phase (because each detection resistor has a tolerance value, the value detected by the bus current sampling circuit using three detection resistors will have a large error compared to the actual value). Therefore, the detection module in this application's technical solution not only simplifies the circuit but also makes each detection value more accurate; this provides data support for the safety and precise power control of servo motors.

[0028] The technical solution of this application incorporates adjustable power supplies in both the two-phase current sampling circuit and the three-phase total current sampling circuit. This adjustable power supply ensures that the detection module can detect the current in any two phases and the bus even when the output power of the servo motor is very low (e.g., during the grinding and assembly of high-precision, small parts). Although the operational amplifier can amplify the input signal, its minimum detection value is limited by the input offset voltage V. OS The restriction is that the sampled value is less than V. OS The power amplifier will not be able to recognize the sampled value; after adding a regulating power supply, the sampled value will be amplified. Since the parameter value of the regulating power supply is fixed, the sampled value can be calculated by subtracting the amplified part from the value after amplification by the operational amplifier. Clamping circuits are set in the regulating power supply of any two-phase current sampling circuit. The clamping circuit is set to ensure that the sampling circuit has a stable and definite superimposed value from the regulating power supply. The detection module of "A Servo Circuit Controlled by an Optical Encoder" with application number 2020229945024 does not have such a setting. Therefore, the servo motor control using the technical solution of this application is more precise and applicable to more application scenarios.

[0029] The temperature detection module makes the drive circuit safer to operate and better adaptable to high-current working environments. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the power supply circuit for a servo motor drive circuit.

[0031] Figure 2 This is a schematic diagram of the main control circuit for a servo motor drive circuit.

[0032] Figure 3 This is a schematic diagram of a magnetic encoder circuit for a servo motor drive circuit.

[0033] Figure 4 This is a schematic diagram of an RS485 communication circuit for a servo motor drive circuit.

[0034] Figure 5 This is a schematic diagram of a CAN communication circuit for a servo motor drive circuit.

[0035] Figure 6 This is a schematic diagram of the drive and inverter module of a servo motor drive circuit.

[0036] Figure 7 This is a schematic diagram of a current detection circuit for a servo motor drive circuit.

[0037] Figure 8 This is a schematic diagram of a temperature detection circuit for a servo motor drive circuit. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solution of this utility model, we will now select preferred embodiments to provide a detailed description of the technical solution of this utility model.

[0039] like Figures 1 to 8 As shown, a servo motor drive circuit includes a power supply module, a drive module, an inverter module, a detection module, a magnetic encoder module, an RS485 communication module, a CAN communication module, a main control module, and a temperature detection module.

[0040] like Figure 1 As shown, the power module's input terminal is equipped with a three-stage input filtering circuit. In order of current input, the circuit consists of: a first-stage filter circuit with two 47µF / 50V capacitors in parallel to filter low-frequency ripple; a second-stage filter circuit with two 10µF capacitors in parallel to filter mid-to-high frequency, high-energy ripple; and a third-stage filter circuit with a 0.1µF capacitor to filter ultra-high frequency ripple. The first-stage filter circuit provides optimal filtering for mid-to-low frequency ripple from 500MHz to 50kHz. The second-stage filter circuit provides optimal filtering for mid-to-high frequency ripple from 50kHz to 1MHz. The third-stage filter circuit provides optimal filtering for ultra-high frequency ripple from 1MHz to 100MHz. The frequency of a high-frequency heating furnace is generally in the range of 10kHz to 1MHz, and the current is typically 100A to 700A, sometimes even reaching 1000A. This design prevents interference from power surges and multi-frequency noise.

[0041] like Figures 2 to 6 As shown, the power filtering circuits for the main control module, magnetic encoder module, RS485 communication module, CAN communication module, drive module, and inverter module all use two parallel capacitors. The capacitance of the first capacitor in the direction of current input is greater than or equal to the capacitance of the second capacitor. For example, the first capacitor in the main control module and inverter module power filtering circuits has a capacitance of 10µF, and the second capacitor has a capacitance of 0.1µF. Since a 10µF capacitor provides optimal filtering for mid-to-high frequencies (5kHz to 500kHz) and optimal filtering for ultra-high frequency ripple (1MHz to 100MHz), and the 10µF capacitor has a moderate capacitance, this filtering circuit has good filtering capability for high-energy mid-to-high frequency ripple while also providing filtering capability for low-frequency and ultra-high frequency ripple. The functions of the power filtering circuits in other modules are basically the same as those in the main control module, and will not be listed individually here.

[0042] In cases where external real-time monitoring of the servo motor is not required, this specific embodiment can omit the RS485 communication module, thereby simplifying the servo motor drive circuit. In environments with relatively mild interference or where high precision is required, the inverter module's power supply filter circuit can also be omitted; this is because the inverter module's current input can be connected to the power module's three-stage input filter circuit, and the MOSFETs in the inverter circuit have stronger anti-interference capabilities compared to other electronic components.

[0043] like Figure 6 As shown, each signal circuit from the main control module to the drive module is equipped with a primary filtering circuit. Furthermore, the filtering circuit is located at the signal input terminal of the drive module. This configuration ensures the accuracy of the drive circuit.

[0044] like Figure 6 and 7 As shown, the detection module samples the current of any two phases and the total three-phase current output from the inverter module. Both the arbitrary two-phase current sampling circuit and the total three-phase current sampling circuit are equipped with adjustable power supplies. The adjustable power supplies of the arbitrary two-phase current sampling circuits are equipped with clamping circuits. A filter capacitor is placed between the positive and negative input terminals of the operational amplifier in each detection circuit of the detection module. Figure 7 The sampling circuits shown are relatively independent, each separated by a 0.1R detection resistor for sampling and isolation, preventing interference. The power supply used is a filtered 5V supply from the power module; the addition of a clamping circuit ensures a stable and consistent power supply superposition value for the sampling circuit. Ultra-precision grinding (such as silicon wafer grinding) and ultra-precision assembly (such as the positioning of nanoscale platforms) typically require grinding or positioning power ranging from 1mW to 10mW. As market demands for precision continue to increase, the required power accuracy may even fall below 1mW. For example... Figure 6 The inverter module shown has a servo motor input voltage of 24V. Assuming a power of 1mW, using the formula W=UI, the bus current of the servo motor at this time can be calculated to be approximately 41mA. The minimum detection current of the operational amplifier is 1µA, therefore the minimum sampling resistor value cannot be less than 1KΩ. Figure 6 and 7 As shown, the bus detection resistor is 0.1R, and the sampling resistor is 2KΩ. The sampling current flowing through the bus is approximately 2PA, which is much smaller than the power amplifier's minimum detection current of 1µA. Without power supply adjustment, the servo motor's power cannot be detected, making precise control impossible. The description of the beneficial effects demonstrates that the servo motor control using the detection module in this specific implementation scheme is more accurate and applicable to a wider range of scenarios.

[0045] like Figure 8As shown, the temperature detection module is located on the PCB board where the inverter module is located. A filter circuit is also included in the temperature detection module to prevent interference with the temperature signal. The inclusion of the temperature detection module makes the drive circuit safer to operate and better adapts to high-current operating environments.

[0046] The above specific embodiments are merely preferred embodiments of the present patent's technical solution. Many specific embodiments of the present patent's technical solution exist, and they are not all listed here. All other specific embodiments or modifications derived by those skilled in the art after understanding the present patent's technical solution without inventive effort are within the scope of protection obtained by the present patent's technical solution under patent law.

Claims

1. A servo motor drive circuit comprising a power module, characterized by: The power module's input terminal is equipped with a three-stage power module input filter circuit. In order of current input, the circuit consists of a first-stage filter circuit containing two or more parallel capacitors to filter low-frequency ripple, a second-stage filter circuit containing two or more parallel capacitors to filter mid-to-high frequency high-energy ripple, and a third-stage filter circuit containing one or more capacitors to filter ultra-high frequency ripple. Each capacitor in the same stage of the filter circuit has the same capacitance, and the capacitance value of a single capacitor in the first-stage filter circuit is greater than that in the second-stage filter circuit, and the capacitance value of a single capacitor in the second-stage filter circuit is greater than that in the third-stage filter circuit.

2. A drive circuit for a servo motor as claimed in claim 1, characterized in that: It also includes a power filter circuit for the CAN communication module, a power filter circuit for the magnetic encoder module, a power filter circuit for the main control module, and a power filter circuit for the drive module. All of these circuits contain two or more parallel capacitors to filter out high-frequency, high-energy ripple.

3. A drive circuit for a servo motor as claimed in claim 2, wherein: In the power filtering circuits of the CAN communication module, magnetic encoder module, main control module, and drive module, the capacitance of the first capacitor in the direction of current input is greater than that of the second capacitor, and so on. The capacitance of each preceding capacitor is greater than that of the capacitor following it.

4. A drive circuit for a servo motor as claimed in claim 3, wherein: It also includes an RS485 communication module power supply filter circuit, which is a filter circuit containing two or more parallel capacitors to filter out high-frequency, high-energy ripple.

5. A drive circuit for a servo motor as claimed in claim 4, wherein: In the power filter circuit of the RS485 communication module, the capacitance of the first capacitor in the direction of current input is greater than that of the second capacitor, and so on. The capacitance of each preceding capacitor is greater than that of the capacitor following it.

6. A drive circuit for a servo motor according to any one of claims 1 to 5, wherein: It also includes an active module and a drive module. Each signal circuit that sends a signal from the main control module to the drive module is equipped with a first-stage filtering circuit.

7. A drive circuit for a servo motor as claimed in claim 6, characterized in that: It also includes an inverter module and a detection module. The detection module samples any two phase currents and the total three-phase current from the three-phase current output by the inverter module. Both the random two-phase current sampling circuit and the total three-phase current sampling circuit are equipped with adjustable power supplies. The adjustable power supplies of the random two-phase current sampling circuit are equipped with clamping circuits.

8. A drive circuit for a servo motor as claimed in claim 7, characterized in that: A filter capacitor is provided between the positive and negative input terminals of the operational amplifier in each detection circuit of the detection module.

9. A drive circuit for a servo motor as claimed in claim 8, wherein: It also includes a temperature detection module, which is located on the PCB board area where the inverter module is located.

10. A drive circuit for a servo motor as claimed in claim 9, wherein: It also includes an inverter module power supply filter circuit, which is located at the power input terminal of the inverter module. The inverter module power supply filter circuit includes two or more parallel filter capacitors to filter out high-frequency, high-energy ripple.

Images