Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
Measurement principle of brake disc DTV of commercial vehicle
The circumferential thickness difference of the brake disc, abbreviated as the DTV of the brake disc, is the maximum thickness difference on the same circumference of two parallel friction surfaces when the brake disc rotates around the central axis for one circle, and the unit μm represents that the brake disc DTV test principle diagram is shown in fig. 1.
During the rotation of the brake disc, the thickness variation of the brake disc on the same circumference can not be directly measured, so that the method of indirectly measuring the thickness variation of the brake disc is adopted. The distance between two non-contact displacement sensors is S0The distance between the displacement sensor 1 and the inner end face of the brake disc is S1The distance between the displacement sensor 2 and the outer end face of the brake disc is S2Thickness of the brake disc is S3The specific mathematical relationship is as follows:
S3=S0-(S1+S2) (formula 1)
The distance between two non-contact displacers is kept constant during the test, i.e. S0Keeping the same; thus having the thickness S of the brake disc3The sum (S) of the variation of (A) and the distance of the two displacement sensors from the brake disc1+S2) Are equal, the specific mathematical relationship is as follows:
ΔS3=Δ(S1+S2) (formula 2)
In the testing process, the brake disc keeps rotating at a low speed, data of the two non-contact displacement sensors are collected in real time, the variation of the sum of the displacements of the two non-contact displacement sensors after the brake disc rotates for one or more circles is the DTV of the brake disc, and the specific arithmetic relation is as follows:
DTV=Δ(S1+S2) (formula 3)
Test scheme of brake disc DTV of commercial vehicle
Mounting requirements for non-contact displacement sensor
The non-contact displacement sensor with the measuring range of 0 mm-2.5 mm is used in the brake disc DTV test, the distance between a probe of the sensor and a brake disc is installed and controlled within the effective measuring range, the sampling frequency is 1kHz, and the measuring point is shown in figure 2, wherein the displacement sensor 1 and the displacement sensor 2 move to the point 1 and the point 2 to measure the thickness change of the inner diameter of the brake disc, the displacement sensor 1 and the displacement sensor 2 move to the point 3 and the point 4 to measure the thickness change of the middle diameter of the brake disc, and the displacement sensor 1 and the displacement sensor 2 move to the point 5 and the point 6 to measure the thickness change of the outer diameter of the brake disc. The first displacement sensor 1 and the second displacement sensor 1 are positioned at a point 1 and a point 2 to measure the thickness change of the inner diameter of the brake disc, the first displacement sensor 2 and the second displacement sensor 2 are positioned at a point 3 and a point 4 to measure the thickness change of the middle diameter of the brake disc, and the first displacement sensor 3 and the second displacement sensor 3 are positioned at a point 5 and a point 6 to measure the thickness change of the outer diameter of the brake disc.
TABLE 1 brake disc position definition
| Inner diameter (mm)
|
Middle diameter (mm)
|
Outer diameter (mm)
|
| Inner diameter of friction surface of brake disc +10mm
|
Effective working diameter of brake disc
|
The outer diameter of the friction surface of the brake disc is 10mm below zero |
Calculation of test moment of inertia
The experimental moment of inertia is calculated as follows:
I=Gmr2(formula 4)
In equation 4:
i-calculated value of moment of inertia, kg · m 2;
Gmdistributing the maximum designed total mass of the automobile to the part of mass, kg, born by the wheels corresponding to the tested brake according to the braking force distribution ratio design value;
r-rolling radius of wheel, m.
Specification of test conditions
Starting to measure the DTV when the temperature of the friction plate reaches (60 +/-1) DEG C, wherein the rotating speed of a main shaft is constant at 30r/min, and the data measuring time is 8.5 s; taking the arithmetic mean value of DTV measured by 3 groups of displacement sensors as the final measurement result; table 2.DTV growth test sequence number 1 measures DTV for new discs, DTV growth being the DTV value measured at the 34 th time minus the DTV value for new discs.
TABLE 2 DTV growth test sequence
Bench test
The DTV testing device (testing device a) is mounted on a commercial vehicle brake inertia test bed (comprising a tailstock 1a, a force arm 2a, a force sensor 3a, a disc brake assembly 4a, a throttling ring 5a, a speed detector 6a, a middle support 7a, a flywheel disc 8a, a transmission shaft 9a and a motor 10a) to realize the measurement of the DTV of the commercial vehicle brake disc, as shown in FIG. 3, a K-type thermocouple (the temperature measuring range is minus 40 ℃ to 1300 ℃) is mounted on the effective friction radius of the outer friction plate of the friction plate, and the surface of the thermocouple is about (0.5 to 1) mm away from the surface of the friction plate according to the specific requirements of QC/T556 (automobile brake temperature measurement and thermocouple mounting) and the key point of verification. The support frame is arranged at the fixed end of the rack, and the displacement signal enters a computer for storage through a data acquisition system. The brake disc is connected to a direct current motor 10a through an intermediate support 7a and a transmission shaft 9a, wherein the motor 10a is used for simulating the rotating speed of a wheel, and the flywheel disc 8a is used for simulating the load borne by the disc brake assembly 4 a. The fixed end (namely a brake bottom plate) of the brake assembly is connected to a tailstock of the commercial vehicle inertia test bench, and a force arm on the tailstock is connected with a force sensor; in the braking process, the braking force generated by the brake is transmitted to the force sensor through the force arm, and the product of the testing value of the force sensor and the force arm is the braking torque in the test.
Data processing of brake disc DTV of commercial vehicle
Taking the original data of the DTV measured at the middle diameter position of the brake disc of the commercial vehicle as an example, the specific test data is shown in Table 3.
TABLE 3 brake disc pitch diameter DTV raw data
The sampling frequency is 1kHz, the acquisition time is 8.5s, the rotation angle of the brake disc measured by the DTV at one time is 1530 degrees, the acquired data are 8500 groups, and the precision error of the testing equipment, the interference of external electromagnetic signals and the like can influence the acquired test data of the brake disc DTV to a certain extent, so that the test data fluctuation is large, a plurality of bad spots are generated, the test result is not favorably obtained, and the initial test curve of the DTV is shown in FIG. 4.
Therefore, in the process of processing the test data, the filter is required to be used for eliminating interference items in the DTV data, and the accuracy of the data is improved. The invention provides a system suitable for DTV data filtering and test result processing. The data filtering and result calculating part of the procedure is shown in fig. 5. The data reading end of the reading test data module is connected with the test data output end of the controller, the data input end of the data filtering module is connected with the data output end of the reading test data module, the data output end of the data filtering module is connected with the data input end of the DTV data calculating module, the data output end of the DTV data calculating module is connected with the data input end of the cursor intercepting data module, and the data output end of the cursor intercepting data module is connected with the data display end of the curve display module;
the data filtering module generates a digital Butterworth filter by calling a Butterworth coefficient VI, the type of the filter is selected to be a low-pass filter (Lowpass), the sampling frequency is set to be 1Hz, the low cut-off frequency is set to be 0.008Hz, and the order is set to be 1; the cursor intercepting data module sets a starting point and an ending point of the DTV data in the DTV data calculating module by using a cursor option in the XY diagram; and calling the array subset VI and the data maximum value and minimum value VI to calculate the maximum value and minimum value of the data in the cursor selected region and calculate the maximum DTV of the brake disc. The filtered DTV curves and the experimental results are shown on the curve display module as shown in fig. 6.
The invention discloses a measuring device of a brake disc DTV (digital television) of a commercial vehicle, which comprises a support frame, wherein a support rod 11 is fixedly arranged on the support frame, and a first lead screw stepping motor module and a second lead screw stepping motor module which move along the axial direction of the support rod 11 are fixedly arranged on the support rod 11; the first lead screw stepping motor module and the second lead screw stepping motor module are arranged in parallel;
a first lead screw stepping motor module 7 is fixedly installed on a sliding block of the first lead screw stepping motor module, and a first K displacement sensor 8, a first 2 displacement sensor, a first 3 displacement sensor … … and a first K displacement sensor are respectively arranged on a sliding block 7A of the first lead screw stepping motor module 7; the K is a positive integer larger than or equal to 1, a second lead screw stepping motor module 9 is fixedly installed on a sliding block of the second lead screw stepping motor module, and a second K displacement sensor is arranged on a sliding block 9A of the second lead screw stepping motor module 9 and is respectively a second 1 displacement sensor 10, a second 2 displacement sensor, a second 3 displacement sensor … … and a second K displacement sensor; wherein, the 1 st displacement sensor 8 and the 1 st displacement sensor 10 are the 1 st group displacement sensors, the 2 nd displacement sensor 2 and the 2 nd displacement sensor 2 are the 2 nd group displacement sensors, the 3 rd displacement sensor 3 and the 3 rd displacement sensor 3 are the 3 rd group displacement sensors, and the … … Kth displacement sensor 8 and the Kth displacement sensor two are the Kth group displacement sensors; only group 1 displacement sensors are shown in fig. 7. The first distance between every displacement sensor that sets up on the sliding block 7A equals, and every displacement sensor measures the displacement of coplanar and equals, and is corresponding, and the second distance between every displacement sensor that sets up on the sliding block 9A equals, and every displacement sensor measures the displacement of coplanar and equals.
The object to be detected is positioned between the first K displacement sensor and the second K displacement sensor, and the moving directions of the first K displacement sensor and the second K displacement sensor are vertical to the axial direction of the support rod 11;
the controller also comprises a controller, wherein the controller end of a stepping motor of the first lead screw stepping motor module is connected with the control end of a stepping motor of the first lead screw stepping motor module of the controller, the controller end of a stepping motor of the second lead screw stepping motor module is connected with the control end of a stepping motor of the second lead screw stepping motor module of the controller, the controller end of a stepping motor of the first lead screw stepping motor module 7 is connected with the control end of a stepping motor of the lead screw stepping motor module of the controller, the controller end of a stepping motor of the second lead screw stepping motor module 9 is connected with the control end of a stepping motor of the lead screw stepping motor module of the controller, the displacement data output end of the first kth displacement sensor is connected with the displacement kth data input end of the controller, and the displacement data output end of the second kth displacement sensor is connected with the displacement kth + K data input end of the controller; namely, the displacement data output end of the 1 st displacement sensor I is connected with the 1 st data input end of the displacement of the controller, and the displacement data output end of the 1 st displacement sensor II is connected with the K +1 th data input end of the displacement of the controller; the displacement data output end of the 2 nd displacement sensor I is connected with the displacement 2 nd data input end of the controller, and the displacement data output end of the 2 nd displacement sensor II is connected with the displacement K +2 th data input end of the controller; the displacement data output end of the 3 rd displacement sensor I is connected with the displacement 3 rd data input end of the controller, and the displacement data output end of the 3 rd displacement sensor II is connected with the displacement K +3 th data input end of the controller; … …, respectively; the displacement data output end of the first Kth displacement sensor is connected with the displacement Kth data input end of the controller, and the displacement data output end of the second Kth displacement sensor is connected with the displacement 2 Kth data input end of the controller;
and measuring the thickness of the object to be detected at different positions or the thickness variation of the object to be detected at different positions according to the positions of the first K displacement sensor and the second K displacement sensor.
In a preferred embodiment of the invention, the support frame comprises a Z-shaped support seat 2, a connecting cross rod 3, an adjusting block 4, a fixed cross rod 5, a first fixed block 6 and a second fixed block 12;
a first support seat through hole 1 for fixing the Z-shaped support seat 2 through a bolt and a second support seat through hole for connecting one end of a cross rod 3 to pass through are formed in the Z-shaped support seat 2;
the adjusting block 4 is provided with an adjusting block through hole I for one end of the fixed cross rod 5 to pass through and an adjusting block through hole II for the other end of the connecting cross rod 3 to pass through;
a first fixing block through hole and a second fixing block through hole for the other end of the fixing cross rod 5 to pass through are respectively formed in the first fixing block 6 and the second fixing block 12, a third fixing block through hole for one end of the supporting rod 11 to pass through is formed in the first fixing block 6, and a fourth fixing block through hole for the other end of the supporting rod 11 to pass through is formed in the second fixing block 12;
threads matched with the first nut and the second nut are respectively arranged at two ends of the connecting cross rod 3, the Z-shaped supporting seat 2 and the connecting cross rod 3 are fixed through the first nut, and the connecting cross rod 3 and the adjusting block 4 are fixed through the second nut;
threads matched with the three phases of the nuts are arranged at one end of the fixed cross rod 5, and the adjusting block 4 is fixed with the fixed cross rod 5 through the third nut;
a first thread and a second thread which are matched with a fourth nut and a fifth nut are arranged at the other end of the fixed cross rod 5, the first fixed block 6 is fixed with the fixed cross rod 5 through the fourth nut, and the second fixed block 12 is fixed with the fixed cross rod 5 through the fifth nut;
and a thread which is matched with the nut six is arranged at one end of the supporting rod 11, the supporting rod 11 is fixed with the first fixing block 6 through the nut six, a thread which is matched with the nut seven is arranged at the other end of the supporting rod 11, and the supporting rod 11 is fixed with the second fixing block 12 through the nut seven. The support frame realizes the regulation to measuring position, is convenient for install and measure.
In a preferred embodiment of the invention, the diameters of the two ends of the connecting cross rod 3 are smaller than the diameter of the middle of the connecting cross rod 3, and the diameter of the middle of the connecting cross rod 3 is larger than the diameters of the supporting seat through hole II and the adjusting block through hole II;
the diameter of one end of the fixed cross rod 5 is smaller than the diameter of the middle of the fixed cross rod 5, and the diameter of the middle of the fixed cross rod 5 is larger than the diameter of the first adjusting block through hole; the first diameter of the other end of the fixed cross rod 5 is smaller than the diameter of the middle of the fixed cross rod 5, the diameter of the middle of the fixed cross rod 5 is larger than the diameter of the first fixing block through hole, the second diameter of the other end of the fixed cross rod 5 is smaller than the first diameter of the other end of the fixed cross rod 5, and the first diameter of the other end of the fixed cross rod 5 is larger than the diameter of the second fixing block through hole;
the diameters of the two ends of the supporting rod 11 are smaller than the diameter of the middle of the supporting rod 11, and the diameter of the middle of the supporting rod 11 is larger than the diameters of the third fixing block through hole and the fourth fixing block through hole.
The invention also discloses a measuring system of the brake disc DTV of the commercial vehicle, wherein a measuring device of the brake disc DTV of the commercial vehicle is arranged near the object to be measured, and the thickness of the object to be measured or the thickness variation of different positions is measured.
The invention also discloses a measurement processing method of the brake disc DTV of the commercial vehicle, which comprises the following steps:
s1, mounting the measuring device of the brake disc DTV of the commercial vehicle near an object to be measured;
and S2, acquiring the thickness of the object to be detected at different positions or the thickness variation of the object to be detected at different positions.
In a preferred embodiment of the present invention, step S1 includes the following steps:
s11, the controller sends a motion command to the first lead screw stepping motor module, the second lead screw stepping motor module, the first lead screw stepping motor module 7 and the second lead screw stepping motor module 9 to enable the first 1 st displacement sensor 8 and the second 1 st displacement sensor 10 to respectively reach a first position and a second position, and when the first position and the second position are located, the brake disc of the object to be detected can be placed between the first 1 st displacement sensor 8 and the second 1 st displacement sensor 10;
s12, placing the brake disc of the object to be detected between the first 1 st displacement sensor 8 and the second 1 st displacement sensor 10;
s13, the controller sends motion commands to the first lead screw stepping motor module, the second lead screw stepping motor module, the first lead screw stepping motor module 7 and the second lead screw stepping motor module 9 to enable the first 1 st displacement sensor 8 and the second 1 st displacement sensor 10 to respectively reach the measuring positions, and the distance between the first 1 st displacement sensor 8 and the second 1 st displacement sensor 10 is S0;
S14, establishing a rectangular coordinate system:
taking the center of the brake disc of the object to be measured as the origin O of a rectangular coordinate system; the moving direction of the 1 st displacement sensor I8 or the 1 st displacement sensor II 10 to the support rod 11 is the positive direction of the X axis; the moving direction of the screw rod stepping motor module I7 or the screw rod stepping motor module II 9 to the fixing block II 12 is the positive direction of the Y axis;
s15, the brake disc of the object to be detected starts to rotate at the moment t;
s16, recording the distance measured by the first displacement sensor 8 at the moment t +1 as S1,t+1The distance measured by the second displacement sensor 10 at the time t +1 is recorded as S2,t+1
In a preferred embodiment of the present invention, in step S2, the thickness of the object to be detected at different positions of the brake disc is calculated by:
ΔSt+1=S0-(S1,t+1+S2,t+1),
wherein, Delta St+1Represents the thickness of the brake disc of the object to be detected at position P; s0The distance between a 1 st displacement sensor I8 and a 1 st displacement sensor II 10 is shown; s1,t+1The distance between a first 1 st displacement sensor 8 and a brake disc of an object to be detected is represented; s2,t+1The distance between the second 1 st displacement sensor 10 and a brake disc of an object to be detected is represented;
ΔSt+1′=(S1,t+1+S2,t+1)-(S1,0+S2,0),
wherein, Delta St+1' indicates that the brake disk is at position P on the object to be detectedThe amount of thickness variation; s1,t+1The distance between the first displacement sensor (8) 1 and a brake disc of an object to be detected is represented; s2,t+1The distance between the second displacement sensor (10) 1 and a brake disc of an object to be detected is represented; s1,0The initial distance between the first displacement sensor (8) 1 and a brake disc of an object to be detected is represented; s2,0The initial distance between the second 1 st displacement sensor (10) and the brake disc of the object to be detected is shown.
In a preferred embodiment of the present invention, the position P is calculated by:
s61, calculating the initial position (x) at the time tt,yt) Distance from origin of coordinates:
wherein (x)t,yt) Two-dimensional coordinates representing an initial position at time t; d represents the distance between the initial position and the origin of coordinates;
s62, calculating the initial position (x) at the time tt,yt) The connecting line between the coordinate origin and the X axis forms an angle:
wherein alpha represents an angle formed between a connecting line between the initial position and the origin of coordinates and the positive direction of the X axis; alpha is more than or equal to 0 and less than 2 pi;
Wherein, & represents a logical relationship and;
s63, calculating the rotating angle of the brake disc of the object to be measured from the moment t to the moment t + 1:
wherein, betat→t+1Representing the rotating angle of the brake disc of the object to be measured from the moment t to the moment t + 1;
t represents the rotation period of the brake disc of the object to be measured;
t → t +1 represents the time from time t to time t + 1;
s64, calculating the measuring position (x) at the t +1 momentt+1,yt+1) The connecting line between the coordinate origin and the X axis forms an angle:
wherein, betat+1Representing an angle formed between a connecting line between the measurement position at the t +1 moment and the origin of coordinates and the X axis;
q is more than 0, which indicates that the brake disc of the object to be detected rotates clockwise;
q < 0 represents that the brake disc of the object to be detected rotates anticlockwise;
| | represents taking an absolute value;
s65, calculating the coordinates of the measurement position P:
wherein (x)t+1,yt+1) Coordinates representing the measurement location.
In a preferred embodiment of the present invention, the controller sends a motion command to the first lead screw stepping motor module or/and the second lead screw stepping motor module, so that the distance between the first displacement sensor 8 and the second displacement sensor 10 is S0′;S0′<S0。
In a preferred embodiment of the present invention, the controller sends a motion command to the first lead screw stepping motor module 7 and the second lead screw stepping motor module 9 to change the distance between the measuring point of the brake disc of the object to be measured and the origin.
The invention also discloses a measurement display system of the commercial vehicle brake disc DTV, which comprises a measurement device of the commercial vehicle brake disc DTV or a measurement system of the commercial vehicle brake disc DTV or a measurement processing method of the commercial vehicle brake disc DTV;
the data reading end of the reading test data module is connected with the test data output end of the controller, the data input end of the data filtering module is connected with the data output end of the reading test data module, the data output end of the data filtering module is connected with the data input end of the DTV data calculating module, the data output end of the DTV data calculating module is connected with the data input end of the cursor intercepting data module, and the data output end of the cursor intercepting data module is connected with the data display end of the curve display module.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.