Servo drive bus capacitance evaluation method and system for robots

Abstract

The present invention relates to the field of robotics, and specifically to a method and system for evaluating bus capacitance of a servo driver for a robot. The method comprises: determining the bus capacitance capacity of the driver; determining whether the current driver capacitance configuration meets the requirements of harsh working conditions; collecting the speed and torque data of each joint for at least one complete operating cycle; calculating the comprehensive peak power of the entire robot; calculating the minimum bus voltage of the driver; calculating the peak value of the motor line voltage under typical working conditions; calculating the bus voltage fluctuation rate; performing comparison through a bus voltage evaluation and judgment module; calculating the bus capacitance discharge time; and calculating the bus capacitance. The present invention overcomes the potential product quality risks brought about by the fact that the selection of bus capacitance of traditional servo drivers is mostly based on experience and does not fully combine the specific operating conditions of the entire robot, and ensures that problems such as abnormal shutdown or rhythm drop will not occur when the operating conditions of the entire robot are relatively harsh or the input power supply is undervoltage.

Description

Technical Field

[0001] The present invention relates to the field of robotics technology, and in particular to a method and system for evaluating bus capacitance of a servo drive for a robot. Background Art

[0002] Multi-degree-of-freedom industrial robots, due to their high flexibility and programmability, are widely used in numerous industrial fields, including automotive, chemical, logistics, furniture, and bathroom products. As the robot's power actuator, the servo system plays a vital role in the efficient operation of the entire machine. Under the robot's fully linked operating conditions, the bus capacitance of the servo drive directly affects the fluctuations in the DC bus voltage and current, which in turn affects the motor's speed and torque output. When the robot is in an undervoltage condition, due to the drop in power supply voltage, when the bus capacitance is small, the bus voltage drop will exceed the drop in power supply voltage, making the system undervoltage condition more stringent. Therefore, the selection and evaluation of the bus capacitance of the robot servo drive plays a crucial role in whether the robot can meet the normal production and operation requirements under extreme operating conditions.

[0003] Existing robot servo drives are generally designed based on the bus capacitor selection of general servo drives, and are not fully analyzed in combination with the specific operating conditions of the robot. Under harsh operating conditions of the robot or under-voltage conditions of the input power supply, abnormal shutdown or rhythm drop may occur, seriously affecting the user experience. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a method and system for evaluating the bus capacitance of a servo drive for a robot.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] The method for evaluating the bus capacitance of a servo drive for a robot includes the following steps:

[0007] S1. Enable the robot driver bus capacitor selection calculation function through the driver bus capacitor selection function judgment module. The selection calculation result is used to determine the driver bus capacitor capacity.

[0008] S2. Enable the current bus capacitance evaluation calculation function of the robot driver through the driver bus capacitance evaluation function judgment module. The evaluation calculation result is used to determine whether the current driver capacitance configuration meets the requirements of severe working conditions.

[0009] S3. Using the extreme harsh working condition data acquisition module, operate the robot to be evaluated under full-load and full-speed harsh working conditions, and collect speed and torque data of each joint for at least one complete operating cycle;

[0010] S4, using the robot peak power calculation module to calculate the speed and torque data of each joint collected by S3 and obtain the comprehensive peak power of the robot;

[0011] S5. Calculate and obtain the minimum value of the driver bus voltage by using the driver bus voltage extreme value calculation module using the comprehensive peak power calculated according to S4 and the actual bus capacitance value of the driver;

[0012] S6. Calculate and obtain the motor line voltage peak value under typical working conditions by combining the robot joint motor parameters and the speed and torque data of each joint collected in S3 through the joint motor line voltage peak calculation module and based on the permanent magnet synchronous motor voltage equation;

[0013] S7. Calculate and obtain an ideal bus voltage value based on the input power voltage through a bus voltage fluctuation rate calculation module, and calculate and obtain a bus voltage fluctuation rate based on the ideal bus voltage value and a desired minimum bus voltage value;

[0014] S8, using the bus voltage evaluation and judgment module to compare the bus voltage minimum value obtained in S5 with the joint motor line voltage peak value obtained in S6;

[0015] S9, calculating and obtaining the bus capacitor discharge time through the bus capacitor discharge time calculation module according to the input power supply frequency phase number and the bus voltage fluctuation rate obtained in S7;

[0016] S10. Calculate and obtain the bus capacitance through a bus capacitance value calculation module under the condition that the lowest bus voltage is not lower than the peak value of the motor line voltage when the bus capacitance is discharged at peak power, while taking into account the inverter efficiency and the motor efficiency.

[0017] As a further improvement of the present invention, the conditions for determining whether the current driver capacitor configuration meets the requirements of harsh working conditions in S2 are: if the lowest value of the driver bus voltage is greater than the peak value of the joint motor line voltage, it means that the current driver capacitor configuration meets the requirements of harsh working conditions; if the lowest value of the driver bus voltage is less than the peak value of the joint motor line voltage, it means that the current driver capacitor configuration does not meet the requirements of harsh working conditions.

[0018] As a further improvement of the present invention, the calculation formula of the comprehensive peak power of the robot in S4 is:

[0019]

[0020] Where, P k is the comprehensive peak power, T m is the motor torque, ω n is the motor speed.

[0021] As a further improvement of the present invention, the calculation formula for the minimum value of the driver bus voltage in S5 is:

[0022]

[0023] Where, t dischargetime is the discharge time, f in is the input voltage frequency, n is the number of input voltage phases, U bus is the bus voltage, U min is the lowest voltage of the actual bus capacitor at peak power, C act is the actual bus capacitance used, P k is the integrated peak power, η d is the inverter efficiency, η m is the motor efficiency.

[0024] As a further improvement of the present invention, the calculation formula of the permanent magnet synchronous motor voltage equation in S6 is:

[0025]

[0026] Where u d is the D-axis voltage, R s is the stator resistance, i d D-axis current, L d is the D-axis inductance, ω e is the electrical angular velocity, L q is the Q-axis inductance, i q is the Q-axis current, u q is the Q-axis voltage, ψ f is the rotor flux, U lp is the peak line voltage under typical operating conditions.

[0027] As a further improvement of the present invention, the calculation formula of the bus voltage fluctuation rate in S7 is:

[0028]

[0029] Where A is the voltage fluctuation rate, U bus is the bus voltage, U lp is the peak line voltage under typical operating conditions.

[0030] As a further improvement of the present invention, in S8, if the lowest value of the driver bus voltage is greater than the peak value of the joint motor line voltage, it means that the current bus capacitance capacity of the driver is sufficient; if the lowest value of the driver bus voltage is less than the peak value of the joint motor line voltage, it means that the current bus capacitance capacity of the driver is insufficient.

[0031] As a further improvement of the present invention, the calculation formula for the bus capacitor discharge time in S9 is:

[0032]

[0033] Where, t dischargetime is the discharge time, n is the number of input voltage phases, f in is the input voltage frequency, and A is the voltage fluctuation rate.

[0034] As a further improvement of the present invention, the calculation formula of the bus capacitance in S10 is:

[0035]

[0036] Where C neededCap is the expected bus capacitance under typical operating conditions, P k is the integrated peak power, η d is the inverter efficiency, η m is the motor efficiency, t dischargetime is the discharge time, U bus is the bus voltage, U lp is the peak line voltage under typical operating conditions.

[0037] The robot servo drive bus capacitance evaluation system is applied to the above-mentioned robot servo drive bus capacitance evaluation method, including a drive bus capacitance selection function judgment module, a drive bus capacitance evaluation function judgment module, an extreme harsh working condition data acquisition module, a robot peak power calculation module, a drive bus voltage extreme value calculation module, a joint motor line voltage peak value calculation module, a bus voltage fluctuation rate calculation module, a bus voltage evaluation judgment module, a bus capacitance discharge time calculation module, and a bus capacitance value calculation module.

[0038] The beneficial effects of the present invention are:

[0039] The present invention provides a method and system for evaluating the bus capacitance of a servo driver for a robot. The method evaluates the bus capacitance of the driver based on data collected from the harsh working conditions of the entire robot, and performs analysis in combination with the mechanical parameters of the robot joints, the joint motor line voltage model, and the driver bus voltage fluctuation rate model. This overcomes the potential product quality risks brought about by the fact that traditional servo driver bus capacitance selection is mostly based on experience and does not fully combine the specific operating conditions of the entire robot. It ensures that abnormal shutdowns or rhythm drops will not occur when the operating conditions of the entire robot are relatively harsh or the input power supply is undervoltage, thereby significantly improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0041] Figure 1 Flow chart of the method of the present invention;

[0042] Figure 2This is a schematic diagram of the peak power of the robot;

[0043] Figure 3 This is a schematic diagram of the line voltage waveform of the robot joint motor;

[0044] Figure 4 This is a schematic diagram of the torque waveform of joints 1-6 of the robot;

[0045] Figure 5 Schematic diagram of the rotational speed waveform of joints 1-6 of the robot. DETAILED DESCRIPTION

[0046] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0047] like Figure 1 As shown in FIG, the method for evaluating the bus capacitance of a servo drive for a robot includes the following steps:

[0048] S1. Enable the robot driver bus capacitor selection calculation function through the driver bus capacitor selection function judgment module. The selection calculation result is used to determine the driver bus capacitor capacity.

[0049] S2. The driver bus capacitance evaluation module enables the robot driver's current bus capacitance evaluation and calculation function. The evaluation result is used to determine whether the current driver capacitance configuration meets the requirements for harsh operating conditions. If the minimum driver bus voltage is greater than the joint motor line voltage peak, the current driver capacitance configuration meets the requirements for harsh operating conditions. If the minimum driver bus voltage is less than the joint motor line voltage peak, the current driver capacitance configuration does not meet the requirements for harsh operating conditions.

[0050] S3. The robot to be evaluated is operated in a full-load, full-speed and harsh working condition through the extreme harsh working condition data acquisition module, and the speed and torque data of each joint are collected for at least one complete operating cycle. In this embodiment, the torque and speed sampling data waveforms of the robot 1-6 joints are as follows: Figure 4 and Figure 5 shown.

[0051] S4, the robot peak power calculation module uses the speed and torque data of each joint collected by S3 to calculate and obtain the comprehensive peak power of the robot. The comprehensive power curve of the robot is as follows Figure 2 shown.

[0052] The calculation formula for the comprehensive peak power of the robot is:

[0053]

[0054] Where, P kis the comprehensive peak power, T m is the motor torque, ω n is the motor speed.

[0055] In this embodiment, the comprehensive peak power of the entire robot is 15.37KW.

[0056] S5. The driver bus voltage extreme value calculation module calculates and obtains the minimum value of the driver bus voltage by using the comprehensive peak power calculated according to S4 and the actual bus capacitance of the driver.

[0057] The calculation formula for the minimum value of the driver bus voltage is:

[0058]

[0059] Where, t dischargetime is the discharge time, f in is the input voltage frequency, n is the number of input voltage phases, U bus is the bus voltage, U min is the lowest voltage of the actual bus capacitor at peak power, C act is the actual bus capacitance used, P k is the integrated peak power, η d is the inverter efficiency, η m is the motor efficiency.

[0060] In this embodiment, the comprehensive peak power of the entire robot is 15.37KW, and the actual bus capacitance of the driver is 3000uF.

[0061] S6. Through the joint motor line voltage peak calculation module, the robot joint motor parameters and the speed and torque data of each joint collected by S3 are combined, and based on the permanent magnet synchronous motor voltage equation, the motor line voltage peak under typical working conditions is calculated and obtained.

[0062] The calculation formula of the permanent magnet synchronous motor voltage equation is:

[0063]

[0064] Where u d is the D-axis voltage, R s is the stator resistance, i d D-axis current, L d is the D-axis inductance, ω e is the electrical angular velocity, L q is the Q-axis inductance, i q is the Q-axis current, u q is the Q-axis voltage, ψ f is the rotor flux, U lp is the peak line voltage under typical operating conditions.

[0065] In this embodiment, the key parameters of the motors of each joint of the robot are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] In this embodiment, the peak value of the motor line voltage is 427.6V. The peak value curve of the joint motor line voltage is as follows: Figure 3 shown.

[0070] S7. Calculate and obtain the ideal bus voltage value based on the input power voltage through the bus voltage fluctuation rate calculation module, and calculate and obtain the bus voltage fluctuation rate based on the ideal bus voltage value and the expected minimum bus voltage value.

[0071] The calculation formula for bus voltage fluctuation rate is:

[0072]

[0073] Where A is the voltage fluctuation rate, U bus is the bus voltage, U lp is the peak line voltage under typical operating conditions.

[0074] In this embodiment, the input power voltage is three-phase 380V power supply with a frequency of 50 Hz. The ideal bus voltage is 456.8V, and the bus voltage fluctuation rate is 6.38%.

[0075] S8. The bus voltage evaluation module compares the lowest bus voltage value obtained in S5 with the joint motor line voltage peak value obtained in S6. If the lowest bus voltage value of the driver is greater than the joint motor line voltage peak value, it indicates that the current bus capacitor capacity of the driver is sufficient. If the lowest bus voltage value of the driver is less than the joint motor line voltage peak value, it indicates that the current bus capacitor capacity of the driver is insufficient.

[0076] S9. The bus capacitor discharge time calculation module calculates and obtains the bus capacitor discharge time according to the input power supply frequency and phase number and the bus voltage fluctuation rate obtained in S7.

[0077] The calculation formula for the busbar capacitor discharge time is:

[0078]

[0079] Where, t dischargetime is the discharge time, n is the number of input voltage phases, f in is the input voltage frequency, and A is the voltage fluctuation rate.

[0080] In this embodiment, the input power supply frequency phase number is three-phase 380V power supply, the frequency is 50 Hz, and the bus capacitor discharge time is 22 mS.

[0081] S10. Calculate and obtain the bus capacitance through a bus capacitance value calculation module under the condition that the lowest bus voltage is not lower than the peak value of the motor line voltage when the bus capacitance is discharged at peak power, while taking into account the inverter efficiency and the motor efficiency.

[0082] The calculation formula for busbar capacitance is:

[0083]

[0084] Where C neededCap is the expected bus capacitance under typical operating conditions, P k is the integrated peak power, η d is the inverter efficiency, η m is the motor efficiency, t dischargetime is the discharge time, U bus is the bus voltage, U lp is the peak line voltage under typical operating conditions.

[0085] In this embodiment, the peak discharge power is 15.37KW, the minimum bus voltage can reach 395.6V, the motor line voltage peak is 427.6V, the inverter efficiency and the motor efficiency are both taken as 90%. In order to ensure that the bus will not be under-voltage at the maximum output power when the bus capacitor is discharged, the expected bus capacitance is calculated to be 3223uF.

[0086] In addition, the present invention also includes a servo drive bus capacitance evaluation system for a robot, which is applied to the above-mentioned servo drive bus capacitance evaluation method for a robot, including a drive bus capacitance selection function judgment module, a drive bus capacitance evaluation function judgment module, an extreme harsh working condition data acquisition module, a robot peak power calculation module, a drive bus voltage extreme value calculation module, a joint motor line voltage peak value calculation module, a bus voltage fluctuation rate calculation module, a bus voltage evaluation judgment module, a bus capacitance discharge time calculation module, and a bus capacitance value calculation module.

[0087] The driver bus capacitance selection function judgment module is used to judge whether to enable the robot driver bus capacitance selection calculation function. The driver bus capacitance evaluation function judgment module is used to judge whether to enable the robot driver current bus capacitance evaluation calculation function.

[0088] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and description merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating busbar capacitance of a robot servo drive, characterized by: The following steps are involved: S1. Enable the robot driver bus capacitor selection calculation function through the driver bus capacitor selection function judgment module. The selection calculation result is used to determine the driver bus capacitor capacity. S2. Enable the current bus capacitance evaluation calculation function of the robot driver through the driver bus capacitance evaluation function judgment module. The evaluation calculation result is used to determine whether the current driver capacitance configuration meets the requirements of severe working conditions. S3. Using the extreme harsh working condition data acquisition module, operate the robot to be evaluated under full-load and full-speed harsh working conditions, and collect speed and torque data of each joint for at least one complete operating cycle; S4, using the robot peak power calculation module to calculate the speed and torque data of each joint collected by S3 and obtain the comprehensive peak power of the robot; S5. Calculate and obtain the minimum value of the driver bus voltage by using the driver bus voltage extreme value calculation module using the comprehensive peak power calculated according to S4 and the actual bus capacitance of the driver; S6. Calculate and obtain the motor line voltage peak value under typical working conditions by combining the robot joint motor parameters and the speed and torque data of each joint collected in S3 through the joint motor line voltage peak calculation module and based on the permanent magnet synchronous motor voltage equation; S7. Calculate and obtain an ideal bus voltage value based on the input power voltage through a bus voltage fluctuation rate calculation module, and calculate and obtain a bus voltage fluctuation rate based on the ideal bus voltage value and a desired minimum bus voltage value; S8, using the bus voltage evaluation and judgment module to compare the bus voltage minimum value obtained in S5 with the joint motor line voltage peak value obtained in S6; S9, calculating and obtaining the bus capacitor discharge time through the bus capacitor discharge time calculation module according to the input power supply frequency phase number and the bus voltage fluctuation rate obtained in S7; S10. Calculate and obtain the bus capacitance through a bus capacitance value calculation module under the condition that the lowest bus voltage is not lower than the peak value of the motor line voltage when the bus capacitance is discharged at peak power, while taking into account the inverter efficiency and the motor efficiency.

2. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The conditions for determining whether the current driver capacitor configuration meets the requirements of severe working conditions in S2 are as follows: if the lowest value of the driver bus voltage is greater than the joint motor line voltage peak value, it means that the current driver capacitor configuration meets the requirements of severe working conditions; if the lowest value of the driver bus voltage is less than the joint motor line voltage peak value, it means that the current driver capacitor configuration does not meet the requirements of severe working conditions.

3. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The calculation formula for the comprehensive peak power of the robot in S4 is: Where, P k is the comprehensive peak power, T m is the motor torque, ω n is the motor speed.

4. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The calculation formula for the minimum value of the driver bus voltage in S5 is: Where, t dischargetime is the discharge time, f in is the input voltage frequency, n is the number of input voltage phases, U bus is the bus voltage, U min is the lowest voltage of the actual bus capacitor at peak power, C act is the actual bus capacitance used, P k is the integrated peak power, η d is the inverter efficiency, η m is the motor efficiency.

5. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The calculation formula of the permanent magnet synchronous motor voltage equation in S6 is: Where u d is the D-axis voltage, R s is the stator resistance, i d D-axis current, L d is the D-axis inductance, ω e is the electrical angular velocity, L q is the Q-axis inductance, i q is the Q-axis current, u q is the Q-axis voltage, ψ f is the rotor flux, U lp is the peak line voltage under typical operating conditions.

6. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The calculation formula of bus voltage fluctuation rate in S7 is: Where A is the voltage fluctuation rate, U bus is the bus voltage, U lp is the peak line voltage under typical operating conditions.

7. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: In S8, if the lowest value of the driver bus voltage is greater than the joint motor line voltage peak value, it means that the current bus capacitance capacity of the driver is sufficient. If the lowest value of the driver bus voltage is less than the joint motor line voltage peak value, it means that the current bus capacitance capacity of the driver is insufficient.

8. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The calculation formula for the busbar capacitor discharge time in S9 is: Where, t dischargetime is the discharge time, n is the number of input voltage phases, f in is the input voltage frequency, and A is the voltage fluctuation rate.

9. The method for evaluating bus capacitance of a robot servo drive according to claim 1, wherein: The calculation formula for the busbar capacitance in S10 is: Where C neededCap is the expected bus capacitance under typical operating conditions, P k is the integrated peak power, η d is the inverter efficiency, η m is the motor efficiency, t dischargetime is the discharge time, U bus is the bus voltage, U lp is the peak line voltage under typical operating conditions.

10. A robot servo drive busbar capacitance evaluation system, characterized by: The robot servo drive bus capacitance evaluation method applied to any one of claims 1 to 9 includes a drive bus capacitance selection function judgment module, a drive bus capacitance evaluation function judgment module, an extreme harsh working condition data acquisition module, a robot peak power calculation module, a drive bus voltage extreme value calculation module, a joint motor line voltage peak value calculation module, a bus voltage fluctuation rate calculation module, a bus voltage evaluation judgment module, a bus capacitance discharge time calculation module, and a bus capacitance value calculation module.

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