A dynamic angular acceleration measurement and evaluation method

Abstract

This invention discloses a method for measuring and evaluating dynamic angular acceleration, belonging to the field of measurement and control technology and instruments. The method involves rigidly connecting a circular grating encoder to the moving part of the angular acceleration generating device being evaluated, and ensuring that the axis of the circular grating encoder is in the same direction as the rotation axis corresponding to the angular acceleration generating device being measured; using a sampling frequency F... S The invention records two orthogonal discrete signal sequences V(i) and U(i) output from a circular grating encoder; removes the DC component of V(i) to obtain a signal sequence V′(i) with a mean of 0; obtains the instantaneous frequency I(i) at each point using an instantaneous frequency estimation method; obtains the angular velocity sequence |ω(i)|; determines the direction of angular motion, with the motion direction corresponding to the i-th point determined by the phase difference between the V(i) and U(i) signals, thus obtaining the angular velocity sequence ω′(i); and numerically differentiates the angular velocity sequence ω′(i) to obtain the angular acceleration sequence a(i). This invention enables the measurement and evaluation of dynamic angular acceleration with a large range of angular velocity variations and high precision.

Description

Technical Field

[0001] This invention belongs to the field of measurement and control technology and instruments, and relates to a method for measuring and calibrating angular acceleration inertial parameters using a circular grating encoder. Background Technology

[0002] When an object rotates, it generates angular velocity and angular acceleration. In practical applications, sensors such as gyroscopes are typically used to acquire these values, for example, in the inertial navigation systems of aircraft. However, the static and dynamic characteristics of a gyroscope need to be calibrated using turntables, angular acceleration testers, etc. Currently, various methods for measuring constant angular velocity generated by uniform rotation are relatively mature, but the evaluation of changing angular acceleration still faces many challenges.

[0003] Circular grating encoders are widely used devices for measuring angular motion parameters. They have high measurement accuracy and good dynamic characteristics. In particular, their gratings have advantages such as easy installation and good traceability, and they are gradually becoming important equipment for angular acceleration calibration.

[0004] The output signal of a circular grating encoder is typically two orthogonal sinusoidal signals. The phase of the signal is proportional to the angular displacement of the measured object, and the instantaneous frequency of the signal is proportional to the instantaneous angular velocity of the measured object. When the angular acceleration changes dynamically, such as through rapid reciprocating rotation or variable speed rotation, the signal becomes a time-varying, non-periodic signal, meaning that the frequency at each point is inconsistent, which poses a challenge to the calculation of angular acceleration. Furthermore, the resolution of the angular velocity is positively correlated with the number of lines in the circular grating encoder; that is, the more lines, the higher the resolution of the angular velocity. However, due to limitations imposed by internal photoelectric converters, the range of angular veneers is negatively correlated with the number of lines in the circular grating encoder, meaning that encoders with fewer lines are required at high speeds. Summary of the Invention

[0005] The purpose of this invention is to provide a method for measuring and evaluating dynamic angular acceleration. This method uses a circular grating encoder to measure angular acceleration inertial parameters and calculates dynamic angular acceleration with a large range of angular rate variations and high precision based on the measurement information. In other words, it uses a circular grating encoder to measure, evaluate, and calibrate angular acceleration inertial parameters.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The present invention discloses a method for measuring and evaluating dynamic angular acceleration, comprising the following steps:

[0008] Step (1) rigidly connect the circular grating encoder to the angular acceleration generating device being evaluated, and make the shaft of the circular grating encoder the same as the rotation direction axis corresponding to the angular acceleration being evaluated;

[0009] Step (2) uses a sampling frequency FS Record the discrete point sequence V of two orthogonal signals output by the circular grating encoder. i and U i i = 1, 2, ..., n, where n is the number of sampling points;

[0010] Step (3) Remove V i DC component:

[0011]

[0012] Obtain a signal sequence V′(i) with a mean of 0;

[0013] Step (4) Obtain the instantaneous frequency I(i) at each point using the instantaneous frequency estimation method:

[0014] I(i)=T[V′(i)]

[0015] Where T[·] represents the instantaneous frequency estimate;

[0016] Step (5) Obtain the sequence of angular velocity magnitudes |ω(i)|:

[0017] |ω(i)|=I(i)2π / L

[0018] Where L is the number of lines in the circular grating encoder;

[0019] Step (6) Determine the positive and negative directions of the angular motion and obtain the angular velocity sequence ω′(i):

[0020]

[0021] Step (7) numerically differentiates the angular velocity sequence ω′(i) to obtain the angular acceleration sequence a(i):

[0022] a(i) = [ω′(i+1) - ω′(i)]F S i = 0, 1, 2, ..., n-1

[0023] In step (1), the circular grating encoder is rigidly connected to the angular acceleration generating device being evaluated, and the axis of the circular grating encoder is the same as the rotation direction axis corresponding to the angular acceleration being evaluated.

[0024] In step (4), the instantaneous frequency is calculated by the phase method, spectral peak detection method, zero-crossing method, root estimation method or Hilbert transform method;

[0025] In step (5), the measurement signal of the grating is determined to be usable based on the number of lines of the grating and the value of the angular velocity |ω(i)|.

[0026] In step (6), the direction of motion corresponding to the i-th point is determined by the phase difference between the V(i) and U(i) signals. When the phase difference between V(i) and U(i) is π / 2, it is a forward motion, and when the phase difference is -π / 2, it is a reverse motion.

[0027] Beneficial effects:

[0028] 1. The present invention discloses a method for measuring and evaluating dynamic angular acceleration, which uses a circular grating to quickly and conveniently calculate dynamic angular acceleration, and is highly practical.

[0029] 2. The present invention discloses a dynamic angular acceleration measurement and evaluation method, which utilizes the output signal characteristics of a circular grating to achieve accurate measurement of a large range of angular rate changes.

[0030] 3. The present invention discloses a dynamic angular acceleration measurement and evaluation method, which cleverly obtains high-precision dynamic angular acceleration measurement and evaluation by utilizing the positive correlation between the resolution of angular rate and the number of lines of the circular grating encoder. Attached Figure Description

[0031] Figure 1 This is a schematic diagram showing the connection between two circular grating encoders with different line counts and the angular acceleration generator being evaluated.

[0032] Figure 2 This is a schematic diagram of the discrete point sequence V(i) of the signal output from the recorded circular grating encoder.

[0033] Figure 3 This is a schematic diagram of the steps involved in the measurement method. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in detail below with reference to the invention description and accompanying drawings.

[0035] like Figure 1 As shown in the figure, the specific implementation steps of the dynamic angular acceleration measurement and evaluation method disclosed in this embodiment are as follows:

[0036] (1) The circular encoder 1 with 36,000 grating lines and the circular encoder 2 with 4,000 grating lines are rigidly connected to the angular acceleration generating device to be evaluated, and the axis of the circular encoder is the same as the rotation direction axis corresponding to the angular acceleration to be evaluated.

[0037] (2) Using sampling frequency F S Record the discrete point sequence V of the two orthogonal signals output by each circular grating encoder. i and U i i = 1, 2, ..., n, where n is the number of sampling points;

[0038] (3) Remove Vi DC component:

[0039]

[0040] Obtain a signal sequence V′(i) with a mean of 0;

[0041] (4) Obtain the instantaneous frequency I(i) at each point using the instantaneous frequency estimation method:

[0042] I(i)=T[V′(i)]

[0043] Where T[·] represents the instantaneous frequency estimation, we use the Hilbert transform method here, the steps of which are as follows:

[0044] (4.1) Obtain the continuous signal s(t) corresponding to the discrete sequence V′(i) by function fitting, and then use Hilbert transform to obtain the conjugate signal q(t) of s(t).

[0045]

[0046] (4.2) Obtain the analytic signal corresponding to s(t)

[0047]

[0048] (4.3) Obtain instantaneous phase information

[0049]

[0050] (4.4) The instantaneous frequency of the signal is obtained by taking the derivative.

[0051]

[0052] (5) Obtain the sequence of angular velocity magnitudes |ω(i)|:

[0053] |ω(i)|=I(i)2π / L

[0054] Where L is the number of lines in the circular grating encoder;

[0055] (6) Determine the positive and negative directions of the angular motion and obtain the angular velocity sequence ω′(i):

[0056]

[0057] (7) The angular acceleration sequence a(i) is obtained by numerically differentiating the angular velocity sequence ω′(i):

[0058] a(i) = [ω′(i+1) - ω′(i)]F S i = 0, 1, 2, ..., n-1

[0059] In step (1), the circular grating encoder is rigidly connected to the angular acceleration generating device being evaluated, and the axis of the circular grating encoder is the same as the rotation direction axis corresponding to the angular acceleration being evaluated.

[0060] In step (4), the instantaneous frequency is calculated using a variety of methods, including phase method, spectral peak detection method, zero-crossing method, root estimation method and Hilbert transform method.

[0061] In step (5), the usability of the measurement signal of the grating is determined based on the number of lines of the grating and the value of the angular rate |ω(i)|.

[0062] In step (6), the direction of motion corresponding to the i-th point is determined by the phase difference between the V(i) and U(i) signals. When the phase difference between V(i) and U(i) is π / 2, it is a forward motion, and when the phase difference is -π / 2, it is a reverse motion.

[0063] In step (7), the obtained angular acceleration sequence a(i) can be used to evaluate the rate of change of angular acceleration.

[0064] This invention addresses the problems existing in the measurement and evaluation of varying angular acceleration by implementing angular acceleration measurement and evaluation based on a circular grating encoder. It is applicable to related fields of angular acceleration generation or measurement where a circular grating encoder can be installed.

[0065] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring and evaluating dynamic angular acceleration, characterized in that: Includes the following steps, Step (1) rigidly connect the circular grating encoder to the moving part of the angular acceleration generating device being evaluated, and make the shaft of the circular grating encoder and the rotation axis corresponding to the angular acceleration generating device being measured be in the same direction. Step (2) uses a sampling frequency F S Record the discrete point sequences V(i) and U(i) of two orthogonal signals output by the circular grating encoder, i = 1, 2, ..., n, where n is the number of sampling points; Step (3) Remove the DC component of V(i): Obtain a signal sequence V′(i) with a mean of 0; Step (4) Obtain the instantaneous frequency I(i) at each point using the instantaneous frequency estimation method: I(i)=T[V′(i)] Where T[·] represents the instantaneous frequency estimate; Step (5) Obtain the sequence of angular velocity magnitudes |ω(i)|: |ω(i)|=I(i)2π / L Where L is the number of lines in the circular grating encoder; Step (6) Determine the positive and negative directions of the angular motion and obtain the angular velocity sequence ω′(i): Step (7) numerically differentiates the angular velocity sequence ω′(i) to obtain the angular acceleration sequence a(i): a(i)=[ω′(i+1)-ω′(i)]F S ,i=0,1,2,...,n-1。 2. The method for measuring and evaluating dynamic angular acceleration according to claim 1, characterized in that: In step (1), based on the range of angular velocity, two or more circular grating encoders with different line counts are selected and connected to the angular acceleration generating device being evaluated.

3. The method for measuring and evaluating dynamic angular acceleration according to claim 1, characterized in that: In step (4), the instantaneous frequency is calculated using the phase method, spectral peak detection method, zero-crossing method, root estimation method, or Hilbert transform method.

4. The method for measuring and evaluating dynamic angular acceleration according to claim 1, characterized in that: In step (5), the measurement signal of the grating is determined to meet the usage requirements based on the number of lines and the value of angular velocity |ω(i)|.

5. The method for measuring and evaluating dynamic angular acceleration according to claim 1, characterized in that: In step (6), the direction of motion corresponding to the i-th point is determined by the phase difference between the V(i) and U(i) signals. When the phase difference between V(i) and U(i) is π / 2, it is a forward motion, and when the phase difference is -π / 2, it is a reverse motion.

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