Method and system for evaluating bus capacitance of servo driver for robot

Abstract

The invention relates to the technical field of robots, in particular to a method and system for evaluating bus capacitance of a servo driver for a robot, and the method comprises the steps: determining the capacity of the bus capacitor of the driver; determining whether the current driver capacitor configuration meets the severe working condition requirement or not; acquiring rotating speed and torque data of each joint in at least one complete operation cycle; calculating the comprehensive peak power of the whole robot; calculating the minimum value of the bus voltage of the driver; calculating a motor line voltage peak value under a typical working condition; calculating a bus voltage fluctuation ratio; a bus voltage evaluation and judgment module is used for comparison; calculating bus capacitor discharge time; and calculating to obtain the bus capacitance. According to the method, the potential product quality risk caused by the fact that traditional servo driver bus capacitor type selection is mostly based on experience and is not fully combined with the specific operation condition of the whole robot is overcome; and the problems of abnormal shutdown or rhythm decline and the like cannot occur under the condition that the overall operation condition of the robot is relatively bad or the input power supply is under-voltage.

Description

Technical Field

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

[0002] Multi-DOF industrial robots are widely used in many industrial fields such as automobiles, chemicals, logistics, furniture, and bathrooms due to their high flexibility and programmability. The servo system, as the power actuator of the robot, plays a vital role in the efficient operation of the whole machine. Under the linkage working condition of the whole robot, the bus capacitance of the servo drive directly affects the fluctuation of the DC bus voltage and current, and then affects the speed and torque output of the motor; when the robot is in the undervoltage condition of the power supply, due to the drop in the power supply voltage, when the bus capacitance is small, the bus voltage drop will exceed the drop in the 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 vital role in whether the robot can meet the normal production and operation requirements under extreme operating conditions.

[0003] Existing servo drives for robots 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. When the operating conditions of the robot are relatively harsh or the input power supply is undervoltage, 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 driver bus capacitor selection calculation function for the robot 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 and calculation function of the robot driver through the driver bus capacitance evaluation function judgment module. The evaluation and 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 to make the robot to be evaluated work in a harsh working condition with full load and full speed, and collect the 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. The driver bus voltage extreme value calculation module is used to calculate and obtain the minimum value of the driver bus voltage by using the comprehensive peak power calculated according to S4 and the actual bus capacitance value of the driver;

[0012] S6, using the joint motor line voltage peak value calculation module to combine the robot joint motor parameters and the speed and torque data of each joint collected by S3, and based on the permanent magnet synchronous motor voltage equation, calculate and obtain the motor line voltage peak value under typical working conditions;

[0013] S7. Calculate and obtain the ideal bus voltage value according to the input power voltage through the bus voltage fluctuation rate calculation module, and calculate and obtain the bus voltage fluctuation rate according to the ideal bus voltage value and the expected minimum bus voltage value;

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

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

[0016] S10. The bus capacitance is calculated and obtained by a bus capacitance value calculation module under the condition that the minimum 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 severe 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 indicates 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 peak value of the joint motor line voltage, it indicates that the current driver capacitor configuration does not meet the requirements of severe 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 of 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 input voltage phase number, 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, P k is the comprehensive 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] In the formula, 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 value of 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 value of 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 indicates 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 indicates that the current bus capacitance capacity of the driver is insufficient.

[0031] As a further improvement of the present invention, the calculation formula of 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] In the formula, C neededCap is the expected bus capacitance under typical operating conditions, P k is the comprehensive 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 value of line voltage under typical operating conditions.

[0037] A 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 servo driver bus capacitance evaluation method and system for a robot. The driver bus capacitance is evaluated based on collected data of harsh working conditions of the robot as a whole, and is analyzed in combination with the robot joint mechanical parameters, 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 robot as a whole. This ensures that when the operating conditions of the robot as a whole are relatively harsh or the input power supply is undervoltage, there will be no abnormal shutdown or rhythm drop, and the user experience is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0041] Figure 1 is a 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 robot joints 1-6;

[0045] Figure 5 This is a schematic diagram of the rotation speed waveform of robot joints 1-6. DETAILED DESCRIPTION

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

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

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

[0049] S2. Enable the current bus capacitance evaluation and calculation function of the robot driver through the driver bus capacitance evaluation function judgment module. The evaluation and calculation results are used to determine whether the current driver capacitance configuration meets the requirements of severe working conditions. 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 capacitance 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 capacitance configuration does not meet the requirements of severe working conditions.

[0050] S3. Make the robot to be evaluated work in full-load and full-speed harsh working conditions through the extreme harsh working condition data acquisition module, and collect the speed and torque data of each joint for at least one complete operating cycle. In this embodiment, the torque and speed sampling data waveforms of robot joints 1-6 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 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 value 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 input voltage phase number, 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, P k is the comprehensive peak power, η d is the inverter efficiency, η m is the motor efficiency.

[0060] In this embodiment, the comprehensive peak power of the 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] In the formula, 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 value of 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 according to the input power voltage through the bus voltage fluctuation rate calculation module, and calculate and obtain the bus voltage fluctuation rate according to the ideal bus voltage value and the expected minimum bus voltage value.

[0071] The calculation formula of 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 value of line voltage under typical operating conditions.

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

[0075] S8, compare the bus voltage minimum value obtained by S5 with the joint motor line voltage peak value obtained by S6 through the bus voltage evaluation and judgment module. If the driver bus voltage minimum value is greater than the joint motor line voltage peak value, it means that the current bus capacitor capacity of the driver is sufficient; if the driver bus voltage minimum value is less than the joint motor line voltage peak value, it means 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 phase number and the bus voltage fluctuation rate obtained in S7.

[0077] The calculation formula for bus 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 50Hz, and the bus capacitor discharge time is 22mS.

[0081] S10. The bus capacitance is calculated and obtained by a bus capacitance value calculation module under the condition that the minimum 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 of bus capacitance is:

[0083]

[0084] In the formula, C neededCap is the expected bus capacitance under typical operating conditions, P k is the comprehensive 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 value of 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 motor efficiency are both 90%, to ensure that when the bus capacitor is discharged, the bus will not be under-voltage at the maximum output power, 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 above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for evaluating bus capacitance of a servo drive for a robot, characterized in that: The following steps are involved: S1. Enable the driver bus capacitor selection calculation function for the robot 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 and calculation function of the robot driver through the driver bus capacitance evaluation function judgment module. The evaluation and 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 to make the robot to be evaluated work in a harsh working condition with full load and full speed, and collect the 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. The driver bus voltage extreme value calculation module is used to calculate and obtain the minimum value of the driver bus voltage by using the comprehensive peak power calculated according to S4 and the actual bus capacitance value of the driver; S6, using the joint motor line voltage peak value calculation module to combine the robot joint motor parameters and the speed and torque data of each joint collected by S3, and based on the permanent magnet synchronous motor voltage equation, calculate and obtain the motor line voltage peak value under typical working conditions; S7. Calculate and obtain the ideal bus voltage value according to the input power voltage through the bus voltage fluctuation rate calculation module, and calculate and obtain the bus voltage fluctuation rate according to the ideal bus voltage value and the expected minimum bus voltage value; S8, using the bus voltage evaluation and judgment module to compare the bus voltage minimum value obtained by S5 with the joint motor line voltage peak value obtained by S6; S9, calculating and obtaining the bus capacitor discharge time according to the input power supply frequency phase number and the bus voltage fluctuation rate obtained in S7 through the bus capacitor discharge time calculation module; S10. The bus capacitance is calculated and obtained by a bus capacitance value calculation module under the condition that the minimum 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 servo drive for a robot according to claim 1, characterized in that: The conditions for determining whether the current driver capacitor configuration meets the requirements of severe working conditions in S2 are as follows: if the minimum value of the driver bus voltage is greater than the joint motor line voltage peak value, it indicates that the current driver capacitor configuration meets the requirements of severe working conditions; if the minimum value of the driver bus voltage is less than the joint motor line voltage peak value, it indicates that the current driver capacitor configuration does not meet the requirements of severe working conditions.

3. The method for evaluating bus capacitance of a servo drive for a robot according to claim 1, characterized in that: 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 servo drive for a robot according to claim 1, characterized in that: 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 input voltage phase number, 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, P k is the comprehensive peak power, η d is the inverter efficiency, η m is the motor efficiency.

5. The method for evaluating bus capacitance of a servo drive for a robot according to claim 1, characterized in that: The calculation formula of the permanent magnet synchronous motor voltage equation in S6 is: In the formula, 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 value of line voltage under typical operating conditions.

6. The method for evaluating bus capacitance of a servo drive for a robot according to claim 1, characterized in that: 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 value of line voltage under typical operating conditions.

7. The method for evaluating bus capacitance of a servo drive for a robot according to claim 1, characterized in that: 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 servo drive for a robot according to claim 1, characterized in that: The calculation formula for the bus 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, characterized in that: The calculation formula of bus capacitance in S10 is: In the formula, C neededCap is the expected bus capacitance under typical operating conditions, P k is the comprehensive 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 value of line voltage under typical operating conditions.

10. Servo drive bus capacitance evaluation system for robots, characterized by: The method for evaluating the bus capacitance of a servo drive for a robot as described in 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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