Diagnosis and compensation method for eccentric installation of motor encoder

Abstract

The invention discloses a diagnosis and compensation method for eccentric installation of a motor encoder. The diagnosis and compensation method is used for solving adverse effects caused by eccentric installation of the encoder. According to the technical scheme, firstly, a motor is controlled to accelerate to the rotating speed Nr in a no-load mode, and a frequency tracking algorithm is used for extracting characteristic components of quadrature-axis current; then respectively superposing the virtual eccentric signals theta k and-theta k, and respectively extracting quadrature-axis current characteristics in the two states; and calculating and diagnosing the eccentricity rate and the eccentricity initial phase of the eccentric installation of the encoder by combining the characteristic information in the three different states, and further realizing the compensation of the eccentric installation. According to the diagnosis and compensation method for the eccentric installation of the motor encoder, an extra high-precision encoder or optical sensor equipment does not need to be additionally arranged, the eccentric installation condition of the encoder of a motor driving system can be diagnosed in a short time, the eccentricity rate and the eccentric initial phase information of the encoder are accurately obtained, and the accuracy of the motor encoder is improved. Based on this, the compensation of the eccentric installation of the encoder is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control and fault diagnosis, and particularly relates to a method for diagnosing and compensating the eccentric installation of a motor encoder. Background Art

[0002] In recent years, fields such as industrial robots and servo control have developed rapidly, and the motor drive system is the core part among them. The control part of the motor drive system mostly adopts a closed-loop control mainly based on vector control, and an incremental encoder is generally used to measure the position and speed of the rotor. However, during the installation process of the encoder, it is usually difficult to ensure that the axis of the encoder completely coincides with the axis of the device, which makes the distribution of the indexing grating of the actual encoder disk uneven, thus generating a "false angle" signal and further causing a "false instantaneous angular velocity" signal, thereby affecting the closed-loop control of the motor drive system, resulting in abnormal vibration and noise during the operation of the motor, and even causing damage to the motor in severe cases.

[0003] Currently, researchers have relatively few studies on the diagnosis and compensation measures for the eccentric installation of motor encoders. However, the main measures are to use high-precision encoders or optical sensors as references to correct the errors of the encoder. However, the application of such methods is relatively limited. In actual application scenarios, it is difficult to equip the electric drive system with additional high-precision encoders or optical sensors, which brings higher costs and requires additional installation space. Summary of the Invention

[0004] 1. Technical problems to be solved:

[0005] In view of the above technical problems, the present invention provides a method for diagnosing and compensating the eccentric installation of a motor encoder. This method creatively amplifies the fault information by setting a virtual eccentric state, without the need to install additional high-precision encoder or optical sensor devices. It can diagnose the eccentric installation condition of the encoder of the motor drive system within a short time, accurately obtain the eccentricity and the initial phase information of the eccentricity of the encoder, and based on this, realize the compensation for the eccentric installation of the encoder.

[0006] 2. Technical solutions:

[0007] A method for diagnosing and compensating the eccentric installation of a motor encoder includes the following steps:

[0008] Step 1: Under the vector control framework, set the target speed of the motor speed loop to N r , and control the motor to accelerate from a standstill to the speed N under no-load conditions r ;

[0009] Step 2: After the speed is stable, use the frequency tracking algorithm to extract the first sine component I of the 1-fold mechanical frequency component in the quadrature axis current of the motor in real timeqz1 and the first cosine component I qy1 ;

[0010] Step 3: Superimpose the virtual eccentricity signal θ m on the position signal θ k , and then use the frequency tracking algorithm to extract the second sine component I qz1a and the second cosine component I qy1a of the 1x mechanical frequency component in the quadrature axis current of the motor, and then remove the superimposed signal;

[0011] Step 4: Superimpose the virtual eccentricity signal -θ m on the position signal θ k , and then use the frequency tracking algorithm to extract the third sine component I qz1b and the third cosine component I qy1b of the 1x mechanical frequency component in the quadrature axis current of the motor, and then remove the superimposed signal, and calculate the eccentricity ρ and the initial eccentricity phase θ e ;

[0012] Step 5: According to the calculated eccentricity ρ and the initial eccentricity phase θ e , superimpose the signal θ m on the position signal θ b measured by the encoder to compensate for the influence of the eccentric installation of the encoder.

[0013] Furthermore, in Step 1, the rotational speed N r is in the range of 0.8 to 1 times the rated rotational speed.

[0014] Furthermore, in Step 2, the specific expression of the frequency tracking algorithm used to extract the sine component I qz1 and the cosine component I qy1 of the 1x mechanical frequency component in the quadrature axis current of the motor in real time is:

[0015]

[0016] In the above formula, i q is the quadrature axis current of the motor under the vector control framework, t represents time, and LP represents a low-pass filter.

[0017] Furthermore, in Step 3, superimpose the virtual eccentricity signal θ m on the position signal θ k , and the virtual eccentricity signal θ k is specifically expressed as:

[0018] θ k = ρ k sinθ m (2)

[0019] In the above formula, ρ k is the virtual eccentricity signal θ k corresponding virtual eccentricity.

[0020] Furthermore, in step four, the calculation methods of the eccentricity ρ and the initial eccentricity phase θ e of the encoder eccentric installation specifically include the following steps:

[0021] S41: Calculate the difference dI qz1 and dI qy1 of the sine component and the cosine component of the 1x mechanical frequency component caused by the two superimposed virtual eccentricity signals in step two and step three:

[0022]

[0023] S42: Construct the complex representation of the 1x mechanical frequency component feature according to the result of S41, and solve its complex ratio with the result of step two:

[0024]

[0025] S43: Since the 1x mechanical frequency component feature should be proportional to the encoder eccentricity feature, the eccentricity and the initial eccentricity phase of the encoder eccentricity can be calculated according to the result of S42 and the set virtual eccentricity information:

[0026]

[0027] θ e = arg(Z gain ) (6).

[0028] Furthermore, in step five, according to the calculated eccentricity ρ and the initial eccentricity phase θ e add the signal θ m to the position signal θ b measured by the encoder, and complete the compensation through the added signal θ b . The calculation method of the added signal θ b is:

[0029] θ b = -ρsin(θ m - θ e ) (7).

[0030] 3. Beneficial effects:

[0031] A diagnostic and compensation method for eccentric installation of a motor encoder, which creatively amplifies fault information by setting a virtual eccentric state, does not require additional high-precision encoders or optical sensor devices, can diagnose the eccentric installation of the encoder in the motor drive system in a short time, accurately obtain the eccentricity and the initial phase information of the eccentricity of the encoder, and realize the compensation for the eccentric installation of the encoder based on this. Description of the Drawings

[0032] Figure 1 is a schematic diagram of eccentric encoder installation;

[0033] Figure 2 is a speed loop block diagram under the eccentric state of the encoder;

[0034] Figure 3 is a simulation diagram of the waveform influence of encoder installation eccentricity on current;

[0035] Figure 4 is a waveform extraction diagram of the 1-fold mechanical frequency component of the quadrature-axis current under the eccentric state of the encoder;

[0036] Figure 5 is a simulation diagram of the current waveform after compensating for encoder installation eccentricity;

[0037] Figure 6 is a waveform extraction diagram of the 1-fold mechanical frequency component of the quadrature-axis current after compensating for encoder installation eccentricity;

[0038] Figure 7 is a flowchart of the diagnostic and compensation method for eccentric installation of the motor encoder. Detailed Embodiment

[0039] The present invention will be specifically described below in conjunction with specific embodiments and the accompanying drawings.

[0040] A diagnostic and compensation method for eccentric installation of a motor encoder includes the following steps:

[0041] Step 1: Under the vector control framework, set the target speed of the motor speed loop to N r , and control the motor to accelerate from a standstill to the speed N under no-load conditions r ;

[0042] Step 2: After the speed is stable, use the frequency tracking algorithm to continuously extract the first sine component I qz1 and the first cosine component I qy1 of the 1-fold mechanical frequency component in the quadrature-axis current of the motor;

[0043] Step 3: Superimpose a virtual eccentric signal θ m on the position signal θ k, and then the frequency tracking algorithm is used to extract the second sine component I of the fundamental mechanical frequency component in the quadrature axis current of the motor qz1a and the second cosine component I qy1a , and then the superimposed signal is removed;

[0044] Step 4: Superimpose the virtual eccentricity signal -θ m on the position signal θ k , and then the frequency tracking algorithm is used to extract the third sine component I of the fundamental mechanical frequency component in the quadrature axis current of the motor qz1b and the third cosine component I qy1b , and then the superimposed signal is removed, and the eccentricity ρ and the initial eccentricity phase θ of the eccentric installation of the encoder are calculated e ;

[0045] Step 5: According to the calculated eccentricity ρ and the initial eccentricity phase θ e , superimpose the signal θ m on the position signal θ measured by the encoder b to compensate for the influence of the eccentric installation of the encoder.

[0046] Furthermore, in Step 1, the rotational speed N r should be close to the rated speed of the motor, and it is recommended to be in the range of 0.8 to 1 times the rated speed.

[0047] Furthermore, in Step 1, the sine component I of the fundamental mechanical frequency component in the quadrature axis current of the motor is extracted in real time qz1 and the cosine component I qy1 The frequency tracking algorithm adopted is specifically expressed as:

[0048]

[0049] In the above formula, i q is the quadrature axis current of the motor under the vector control framework, t represents time, and LP represents a low-pass filter.

[0050] Furthermore, in Step 3, the virtual eccentricity signal θ m is superimposed on the position signal θ k , and the virtual eccentricity signal θ k is specifically expressed as:

[0051] θ k =ρ k sinθ m (2)

[0052] In the above formula, ρ k is the virtual eccentricity corresponding to the virtual eccentricity signal θ k .

[0053] Further, in step four, the eccentricity ρ and the initial eccentric phase θ of the eccentric installation of the encoder e are calculated as follows:

[0054] S41: Calculate the difference dI between the sine component and the cosine component of the 1x mechanical frequency component caused by the two superimposed virtual eccentric signals in step two and step three qz1 and dI qy1 :

[0055]

[0056] S42: Construct a complex representation of the 1x mechanical frequency component characteristics according to the result of S41, and solve the complex ratio of it and the result of step two:

[0057]

[0058] S43: Since the 1x mechanical frequency component characteristics should be proportional to the encoder eccentricity characteristics, the eccentricity and the initial eccentric phase of the encoder eccentricity can be calculated according to the result of S42 and the set virtual eccentricity information:

[0059]

[0060] θ e = arg(Z gain ) (6).

[0061] Further, in step five, according to the calculated eccentricity ρ and the initial eccentric phase θ e a signal θ m is superimposed on the position signal θ b measured by the encoder. The calculation method of the superimposed signal θ b is as follows:

[0062] θ b = -ρsin(θ m - θ e ) (7).

[0064] In this specific embodiment, a 4-pole surface-mounted permanent magnet synchronous motor drive system is taken as an example to illustrate the present solution:

[0065] As shown in the appendix Figure 1 , when the encoder is eccentrically installed, that is, the geometric center O of the code disk and the actual rotation center O' are offset. The dotted line and the solid line in the figure respectively represent the ideal position and the actual position of the code disk. δr represents the eccentricity distance. The eccentric installation of the encoder introduces an error in the measured angle. Starting from the initial eccentric phase point, the error δθ between the measured angle θ 2 and the actual angle θ 1 satisfies:

[0066]

[0067] Where ρ is the eccentricity and satisfies:

[0068]

[0069] Where r represents the radius of the code disk. It should be noted that usually, the eccentricity distance δr of the encoder is much smaller than the radius r of the code disk, and the eccentricity is about 10 -2 orders of magnitude. At this time, formula (8) can be simplified to:

[0070] δθ≈ρsinθ 1 (10).

[0071] Since the initial eccentricity phase point usually does not coincide with the 0 position of the encoder, let the initial eccentricity phase be θ e , at this time formula (8) can be expressed as:

[0072] δθ≈ρsin(θ - θ e ) (11)

[0073] Where θ represents the true position of the rotor.

[0074] The rotational speed error caused by eccentricity can be expressed as:

[0075] δω≈ωρcos(θ - θ e ) (12)

[0076] Where ω is the actual rotational speed.

[0077] Therefore, the 1 - times mechanical frequency component of the rotational speed error can be expressed as

[0078]

[0079] It can be seen that the influence of encoder eccentricity on the motor drive system is mainly reflected in two aspects: the offset of the measured angle and the rotational speed error. Usually, due to the small eccentricity, the influence of the measured - angle offset is extremely small and can be ignored, and at the same time, the introduced rotational speed error is also relatively weak.

[0080] However, it can be seen from formulas (12) and (13) that as the rotational speed increases, the error caused by encoder eccentricity in the motor rotational speed will increase. Therefore, in the present invention, the motor is set to operate at a relatively high rotational speed, in the range of 0.8 to 1 times the rated rotational speed, so as to fully amplify the fault characteristics of encoder eccentricity.

[0081] Appendix Figure 2 shows the rotational - speed loop block diagram of the permanent - magnet synchronous motor in the eccentric state. It can be seen from the figure that the δω introduced by encoder eccentricity1 Under closed-loop control, a characteristic component will be induced in the quadrature-axis current, and the frequency of this component is 1 times the mechanical frequency. Attached Figure 3 The current waveforms of the direct axis and quadrature axis of the motor are given with an eccentricity of 0.01 and an initial eccentricity phase of 0. The reference speed is 1200 rpm. From the attached Figure 3 It can be seen that after setting the encoder eccentricity at 0.5 s, obvious periodic fluctuations appear in the quadrature-axis current. Through the frequency tracking algorithm, the corresponding 1 times mechanical frequency component can be extracted, and the extraction result is as attached Figure 4 shown. The 1 times mechanical frequency component in the quadrature-axis current is caused by the speed error δω 1 in the attached Figure 2 closed-loop modulation shown, so the complex gain Z cl can be

[0082]

[0083] In the formula, Z ρ is the complex representation of the 1 times mechanical frequency speed error in formula (13), and there is

[0084]

[0085] Superimposing the virtual eccentricity signal θ k will affect the 1 times mechanical frequency fault component in the quadrature-axis current. The virtual eccentricity signal θ k is specifically expressed as:

[0086] θ k = ρ k sinθ m ≈ ρ k sinθ (16) where ρ k is the virtual eccentricity corresponding to the virtual eccentricity signal θ k .

[0087] The corresponding 1 times mechanical frequency speed error can be expressed as

[0088]

[0089] At this time, the complex form of the 1 times mechanical frequency speed error in formula (17) Z k is

[0090]

[0091] Since there is no change in the speed closed-loop before and after superimposing the virtual eccentricity signal, obviously there is still

[0092]

[0093] Similarly, superimposing the virtual eccentricity signal -θk There is

[0094]

[0095] By simultaneously solving equations (19) and (20), we can obtain

[0096]

[0097] where dI qz1 and dI qy1 respectively represent the differences between the sine and cosine components of the 1x mechanical frequency component caused by the two superimposed virtual eccentricity signals, that is

[0098]

[0099] At this time, by combining equations (14) and (21), we can find

[0100]

[0101] Substituting equations (15) and (18) into the above equation, we get

[0102]

[0103] It is easy to obtain

[0104]

[0105] So far, the diagnosis of the eccentricity and the initial phase of the encoder eccentricity has been completed. Subsequently, the compensation can be completed by superimposing the signal θ b There is

[0106] θ b = -ρsin(θ m -θ e ) (26).

[0107] The current waveforms of the direct axis and quadrature axis of the compensated motor are as shown in the appendix Figure 5 shown. The waveform of the 1x mechanical frequency component of the quadrature axis current extracted by the compensated frequency tracking algorithm is as shown in the appendix Figure 6 shown. It can be seen that the influence caused by the encoder eccentricity after compensation can be better compensated. Figure 7 This is the flowchart of a method for diagnosing and compensating the eccentric installation of a motor encoder according to the present invention.

[0108] The method proposed by the present invention creatively amplifies the fault information by setting the virtual eccentricity state, without the need to install additional high-precision encoder or optical sensor equipment. It can diagnose the eccentric installation of the encoder of the motor drive system in a short time, accurately obtain the eccentricity and the initial phase information of the encoder, and based on this, realize the compensation of the eccentric installation of the encoder.

[0109] Although the present invention has been disclosed above in preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the protection scope of the claims of this application.

Claims

1. A method for diagnosing and compensating for eccentric installation of a motor encoder, characterized in that: The following steps are involved: Step 1: In the vector control framework, set the motor speed loop target speed to N r , control the motor to accelerate from rest to speed N under no-load condition r ; Step 2: After the speed stabilizes, the frequency tracking algorithm is used to extract the first sinusoidal component I of the 1-fold mechanical frequency component in the motor quadrature-axis current in real time. qz1 and the first cosine component I qy1 ; Step 3: In the position signal θ m The virtual eccentricity signal θ is superimposed on k Then, the frequency tracking algorithm is used to extract the second sinusoidal component I of the motor quadrature axis current with the 1-fold mechanical frequency component. qz1a and the second cosine component I qy1a , and then remove the superimposed signal; Step 4: In the position signal θ m Superimpose virtual eccentricity signal -θ k Then, the frequency tracking algorithm is used to extract the third sinusoidal component I of the motor quadrature axis current, which is 1 times the mechanical frequency component. qz1b and the third cosine component I qy1b , then remove the superimposed signal and calculate the eccentricity ρ and eccentric initial phase θ of the eccentric encoder installation e ; Step 5: Based on the calculated eccentricity ρ and eccentric initial phase θ e The position signal θ measured by the encoder m The superimposed signal θ b , to compensate for the effect of eccentric encoder installation.

2. A method for diagnosing and compensating for eccentric installation of a motor encoder according to claim 1, characterized in that: In step 1, the speed N r In the range of 0.8 to 1 times the rated speed.

3. The method for diagnosing and compensating for eccentric installation of a motor encoder according to claim 1, characterized in that: In step 2, the first sinusoidal component I of the 1-fold mechanical frequency component in the motor quadrature-axis current is extracted in real time. qz1 and the first cosine component I qy1 The frequency tracking algorithm used is specifically expressed as: In the above formula, i q is the quadrature-axis current of the motor under the vector control framework, t represents time, and LP represents a low-pass filter.

4. A method for diagnosing and compensating for eccentric installation of a motor encoder according to claim 1, characterized in that: In step 3, the position signal θ m The virtual eccentricity signal θ is superimposed on k , virtual eccentricity signal θ k Specifically expressed as: i k =ρ k sinth m (2) In the above formula, ρ k is the virtual eccentricity signal θ k The corresponding virtual eccentricity.

5. The method for diagnosing and compensating for eccentric installation of a motor encoder according to claim 1, characterized in that: In step 4, the eccentricity ρ and the eccentric initial phase θ of the encoder eccentric installation e The calculation method specifically includes the following steps: S41: Calculate the difference dI between the sine component and the cosine component of the 1-fold mechanical frequency component caused by the superposition of the virtual eccentricity signal in step 2 and step 3 qz1 and dI qy1 : S42: Construct a complex representation of the 1-fold mechanical frequency component characteristic based on the result of S41, and solve its complex ratio with the result of step 2: S43: Since the 1x mechanical frequency component characteristic should be proportional to the encoder eccentricity characteristic, the eccentricity ratio and eccentricity initial phase of the encoder eccentricity can be calculated according to the result of S42 and the set virtual eccentricity information: θ e =arg(Z gain ) (6)。 6. A method for diagnosing and compensating for eccentric installation of a motor encoder according to claim 1, characterized in that: In step 5, according to the calculated eccentricity ρ and eccentric initial phase θ e The position signal θ measured by the encoder m The superimposed signal θ b , by superimposing the signal θ b Compensation is completed, and the superimposed signal θ b The calculation method is θ b =-ρsin(θ m -θ e ) (7).

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