CN114061741B - Measuring device and measuring method for measuring resonant frequency of industrial robot - Google Patents
Measuring device and measuring method for measuring resonant frequency of industrial robot Download PDFInfo
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- CN114061741B CN114061741B CN202111353396.4A CN202111353396A CN114061741B CN 114061741 B CN114061741 B CN 114061741B CN 202111353396 A CN202111353396 A CN 202111353396A CN 114061741 B CN114061741 B CN 114061741B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H13/00—Measuring resonant frequency
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
- B25J19/0095—Means or methods for testing manipulators
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/18—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration in two or more dimensions
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Abstract
The invention discloses a measuring device and a measuring method for measuring the resonant frequency of an industrial robot, wherein the industrial robot comprises a machine base, N joints and N motors which are respectively used for driving the corresponding joints to rotate, wherein the N joints and the N motors are numbered in sequence from the near to the far according to the sequence from the machine base, and N is more than or equal to 4; the measuring device comprises a terminal plate connected with an Nth joint, m three-way accelerometers, a multichannel dynamic signal analyzer, an upper computer and a force hammer. The invention has the characteristics of high efficiency and high measurement accuracy of the resonance frequency of the industrial robot.
Description
Technical Field
The invention relates to the technical field of robots, in particular to a measuring device and a measuring method for measuring the resonant frequency of an industrial robot, which have high efficiency and high accuracy.
Background
The industrial robot can vibrate in a transportation or working state, when the vibration frequency of the excitation source is close to or equal to the resonance frequency of the industrial robot, the industrial robot can vibrate severely to seriously influence the working performance of the industrial robot and reduce the production efficiency, so that the resonance frequency of the industrial robot needs to be measured, the vibration frequency of the excitation source is enabled to avoid the resonance frequency of the industrial robot, and the normal work of the industrial robot is ensured.
In the prior art, a single-response-point method is generally adopted to measure the resonance frequency of the industrial robot, and the problems of large measurement error and low measurement precision exist.
Disclosure of Invention
The invention aims to overcome the defects of large measurement error and low measurement precision in the prior art of measuring the resonance frequency of an industrial robot by a single-response-point method, and provides a measuring device and a measuring method for measuring the resonance frequency of the industrial robot, which are high in efficiency and accuracy.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the measuring device for measuring the resonant frequency of the industrial robot comprises a machine base, N joints and N motors, wherein the N joints and the N motors are respectively used for driving the corresponding joints to rotate, and the N is more than or equal to 4, and the N joints and the N motors are sequentially numbered from the machine base from near to far; the measuring device is characterized by comprising a terminal plate connected with an Nth joint, m three-way accelerometers, a multichannel dynamic signal analyzer, an upper computer and a force hammer; the 1 three-way accelerometer is respectively arranged in the middle of the outer surface of the end plate, in addition, the m-1 three-way accelerometer is respectively arranged on the (N-m+2) -th joint to the (N-th joint, and m is less than or equal to N; the three-way accelerometer is electrically connected with the multichannel dynamic signal analyzer, the multichannel dynamic signal analyzer is electrically connected with the upper computer, and the multichannel dynamic signal analyzer is electrically connected with the force sensor arranged on the outer peripheral surface of the force hammer.
Preferably, the joint comprises a cylinder with one end open, and the bottom plate of the cylinder is fixedly connected with the rotating shaft of the corresponding motor; in the N-m+2th joint to the N joint, for the joint of which the outer end of the opening end of the cylinder is exposed out of the outer peripheral surface of the industrial robot, the three-way accelerometer is arranged on the outer end surface of the opening end of the cylinder; the N-m+2th joint to the N-th joint, for the joints of the cylinder located within the outer peripheral surface of the industrial robot, the three-way accelerometer is mounted on the outer peripheral surface of the industrial robot near the outer end surface of the open end of the cylinder; the three-way accelerometer on the nth joint is mounted on the bottom plate of the cylinder.
Preferably, in the (N-m+2) -th joint to the (N) -th joint, for the joint of which the outer end of the opening end of the cylinder is exposed out of the outer peripheral surface of the industrial robot, two sliding rails are arranged on the outer end surface of the opening end of the cylinder, the extending directions of the two sliding rails are parallel to one diameter of the end surface of the opening end of the cylinder, and the two sliding rails are respectively positioned at two sides of the diameter;
the two slide rails are provided with a plurality of groups of through holes which are arranged at intervals along the extending direction of the slide rails, and one group of through holes comprises two through holes which are respectively positioned on the opposite side surfaces of the two slide rails; the two slide rails are fixedly connected with the corresponding three-way accelerometer through the clamp, the clamp comprises a substrate, a rectangular groove arranged on the upper surface of the substrate, a threaded hole arranged on the rectangular groove, a front clamping plate and a rear clamping plate arranged on two sides of the threaded hole on the lower surface of the substrate; rectangular convex blocks are arranged on the lower surface of the base plate between the front clamping plate and the rear clamping plate, vertical holes corresponding to the threaded holes are formed in the upper surface of the rectangular convex blocks, and threads are formed in the inner side walls of the vertical holes; a rear gap is arranged between the rear side surface of the rectangular lug and the rear clamping plate, a front gap is arranged between the front side surface of the rectangular lug and the front clamping plate, the rear gap and the front gap are respectively connected with two guide rails in a matched mode, and a threaded rod arranged on the three-way accelerometer is connected with the threaded hole and the vertical hole in a matched mode.
Preferably, the front side surface of the rectangular convex block is provided with two front elastic protrusions, the rear side surface of the rectangular convex block is provided with two rear elastic protrusions, the two front elastic protrusions are respectively connected with 2 front through holes of the 2 groups of through holes in a matched mode, and the two rear elastic protrusions are respectively connected with the two rear through holes of the 2 groups of through holes in a matched mode.
The arrangement of the front elastic protrusion, the rear elastic protrusion and the through hole pair enables the sliding block to move relative to the sliding rail, so that the three-way accelerometer can be arranged at different positions of the outer end face of the opening end of the cylinder of the joint, the detected positions are more changeable, and the detection requirement is met.
Preferably, the device also comprises a moving mechanism for moving the power hammer, wherein the moving mechanism comprises a rear vertical plate, a horizontal supporting arm arranged on the upper part of the front surface of the rear vertical plate, a vertical supporting plate arranged on the front part of the lower surface of the horizontal supporting arm and a cylinder arranged on the inner side of the joint of the vertical supporting plate and the horizontal supporting arm; the vertical supporting plate is provided with a bar-shaped opening, the right end of a telescopic rod of the air cylinder extends out of the front of the bar-shaped opening and is connected with the upper end of the lever, the middle part of the lever is rotationally connected with a supporting piece arranged on the edge of the bar-shaped opening, the lower end of the lever is hinged with the right end of the horizontal rod, the left end of the horizontal rod is connected with the force hammer, the lower end of the vertical supporting plate is provided with a horizontal plate, the upper surface of the horizontal plate is provided with a transverse chute, the lower side of the force hammer is connected with a guide rod, the guide rod is in sliding connection with the transverse chute, and the distance between the supporting piece and the upper end of the lever is larger than the distance between the supporting piece and the lower end of the lever; the industrial robot is located between the rear vertical plate and the vertical supporting plate, and the force hammer is located in front of the outer periphery of the cylinder of the Nth joint.
The telescopic rod of the air cylinder of the moving mechanism drives the upper end of the lever to move forwards and backwards, so that the power hammer is driven to move forwards and backwards, when the power hammer approaches to and hits the front side of the outer periphery of the cylinder of the N joint, the force sensor on the power hammer detects an excitation signal, and each three-way accelerometer detects a response signal. The cylinder of the moving mechanism can control the stroke of the telescopic rod to ensure that the forward and backward moving amplitude of the force hammer is the same during each test, so that the striking force of the force hammer is kept stable during each test.
A measurement method of a measurement device for measuring a resonance frequency of an industrial robot, comprising the steps of:
step 1, enabling the X, Y, Z direction of each three-way accelerometer to coincide with a machine base coordinate system of an industrial robot, and installing a shock insulation base between the machine base of the industrial robot and the ground; energizing each motor to drive each joint to rotate;
step 2, knocking an Nth joint by using a force hammer, providing a transient impact force for the industrial robot, reading an input excitation signal delta (t) detected by a force sensor by a dynamic signal analyzer, and reading a response signal y (t) of each three-way accelerometer by the dynamic signal analyzer, wherein t is time;
the upper computer carries out Fourier transformation on the response signal y (t) of each three-way accelerometer to obtain a frequency response function, reads the maximum value point of the curve of the frequency response function according to the sequence from the small frequency value to the large frequency value of the frequency response function, and the frequency corresponding to the read maximum value point is the resonance frequency of the industrial robot measured by each three-way accelerometer;
step 3, setting the measured resonance frequencies of the m three-way accelerometers to be f respectively 1 、f 2 、…、f m By f 1 ，f 2 ，…，f m The resonant frequency f of the industrial robot is calculated.
Preferably, step 3 comprises the steps of:
step 3-1, the transfer function of the known Z-degree-of-freedom industrial robot is:
b is the serial number of m three-way accelerometers, and b is more than or equal to 1 and less than or equal to m; k represents the kth excitation point, and k is more than or equal to 1; a is that b,k,i The obtained remainder is identified according to the structure of the industrial robot; lambda (lambda) i Is the pole of the ith order mode of the industrial robot,is A b,k,i Is in the form of dual->Lambda is lambda i ω is the angular frequency of the transfer function, j is the imaginary number;
step 3-2, setting an error e (ω) of the transfer function as:
wherein,
wherein H is b,k (ω) is a function frequency response prediction value of the industrial robot at ω,for the average value of the actual frequency response measurement values of each joint of the industrial robot at omega, H' b,k,i1 (ω) is an actual frequency response measurement at ω for each joint of the industrial robot; and the error of the transfer function is the integrated result of the individual joint errors, namely:
wherein H is b,k,i1 (ω) is the joint transfer function;
step 3-3, optimizing e (omega) by adopting a least square algorithm, and setting a function f (e (omega)) obtained after optimization as a weight function W (omega);
step 3-4, calculating f 1 ，f 2 ，…，f m Average value of (2)
Step 3-5, calculating f 1 ，f 2 ，…，f m Weight w of (2) 1 ，w 2 ,...,w m :
Step 3-6, calculating the resonant frequency f of the industrial robot by using the following formula:
the machine base of the industrial robot is arranged on the vibration isolation base, so that vibration of the industrial robot in the measuring process is reduced, the three-way accelerometer is connected to the multichannel dynamic signal analyzer, the multichannel dynamic signal analyzer is in data exchange and communication with the upper computer through the USB port and is used for processing and analyzing vibration data of the industrial robot and obtaining resonant frequency of the industrial robot, meanwhile, the multichannel dynamic signal analyzer is connected with the force sensor, and the force hammer is used for knocking the N joint of the industrial robot, so that vibration of the end plate and each joint is generated.
The invention obtains the resonance frequency of the industrial robot through efficient and accurate measurement and calculation, so that the vibration frequency of the excitation source can effectively avoid the resonance frequency of the industrial robot, the working performance of the industrial robot is improved, and the production efficiency and the service life of the industrial robot are improved.
Therefore, the invention has the following beneficial effects: the method can efficiently and accurately measure and calculate the resonant frequency of the industrial robot, so that the resonant frequency of the industrial robot can be effectively avoided by the vibration frequency of the excitation source, and the working performance, the production efficiency and the service life of the industrial robot are improved.
Drawings
FIG. 1 is a side view of the movement mechanism of the present invention;
FIG. 2 is a schematic block diagram of the present invention;
FIG. 3 is a top view of the guide rail of the present invention;
FIG. 4 is a top view of the clamp of the present invention;
FIG. 5 is a bottom view of the clamp of the present invention;
FIG. 6 is a schematic view of a construction of an industrial robot in an embodiment of the invention;
FIG. 7 is a graph comparing the results of the measurement of the present invention and the single point method.
Detailed Description
The invention is further described below with reference to the drawings and detailed description.
The embodiment shown in fig. 6 is a measuring device for measuring the resonant frequency of an industrial robot, the industrial robot 10 comprises a stand 11, 6 joints 12 and 6 motors 13 for driving the corresponding joints to rotate, respectively, sequentially numbered in the order from the near to the far from the stand; the measuring device comprises a circular end plate 14 connected with the 6 th joint, 5 three-way accelerometers 1, a multichannel dynamic signal analyzer 2, an upper computer 3 and a force hammer 4 as shown in figure 2; the 1 three-way accelerometer is arranged in the middle of the outer surface of the end plate, and the other 4 three-way accelerometers are respectively arranged on the 3 rd joint to the 6 th joint; the three-way accelerometer is electrically connected with the multichannel dynamic signal analyzer, the multichannel dynamic signal analyzer is electrically connected with the upper computer, and the multichannel dynamic signal analyzer is electrically connected with the force sensor 401 arranged on the outer circumferential surface of the force hammer.
As can be seen from fig. 6, the stand is connected with the 1 st joint through a first motor, the 1 st joint is connected with a second motor through a first connecting rod, the second motor is connected with a third joint through a second connecting rod, the third joint is connected with a fourth motor through a third connecting rod, the fourth motor is connected with the fourth joint, the fourth joint is connected with a fifth motor through a fourth connecting rod, the fifth motor is connected with the fifth joint through a belt pulley and a belt, the fifth joint is connected with a sixth motor, and the sixth motor is connected with the sixth joint;
as shown in fig. 6, the joint comprises a cylinder 121 with one end open, and the bottom plate of the cylinder is fixedly connected with the rotating shaft of the corresponding motor; the outer ends of the open ends of the cylinders of the 3 rd joint and the 6 th joint are exposed out of the outer peripheral surface of the industrial robot, and the three-way accelerometer is arranged on the outer end surface of the open end of the cylinder; the cylinder of the 4 th joint is positioned in the outer peripheral surface of the industrial robot, and the three-way accelerometer is arranged on the outer peripheral surface of the industrial robot close to the outer end surface of the opening end of the cylinder; the three-way accelerometer on the 6 th joint is arranged on the bottom plate of the cylinder.
As shown in fig. 3, 4 and 5, two sliding rails 2 are arranged on the outer end surfaces of the opening ends of the cylinders of the 3 rd joint and the 6 th joint, the extending directions of the two sliding rails are parallel to one diameter of the end surface of the opening end of the cylinder, and the two sliding rails are respectively positioned on two sides of the diameter;
the two slide rails are provided with 5 groups of through holes which are arranged at intervals along the extending direction of the slide rails, and one group of through holes comprises two through holes which are respectively positioned on the opposite side surfaces of the two slide rails; the two slide rails are fixedly connected with the corresponding three-way accelerometer through a clamp 3, the clamp comprises a base plate 31, a rectangular groove 32 arranged on the upper surface of the base plate, a threaded hole 33 arranged on the rectangular groove, a front clamping plate 34 and a rear clamping plate 35 arranged on two sides of the threaded hole on the lower surface of the base plate; rectangular convex blocks 36 are arranged on the lower surface of the base plate between the front clamping plate and the rear clamping plate, vertical holes corresponding to the threaded holes are formed in the upper surface of the rectangular convex blocks, and threads are formed in the inner side walls of the vertical holes; a rear gap is arranged between the rear side surface of the rectangular lug and the rear clamping plate, a front gap is arranged between the front side surface of the rectangular lug and the front clamping plate, the rear gap and the front gap are respectively connected with two guide rails in a matched mode, and a threaded rod arranged on the three-way accelerometer is connected with the threaded hole and the vertical hole in a matched mode.
The front side of the rectangular lug is provided with two front elastic protrusions, the rear side of the rectangular lug is provided with two rear elastic protrusions, the two front elastic protrusions are respectively connected with 2 front through holes of the 2 groups of through holes in a matched mode, and the two rear elastic protrusions are respectively connected with the two rear through holes of the 2 groups of through holes in a matched mode.
As shown in fig. 1, the device also comprises a moving mechanism for moving the power hammer, wherein the moving mechanism comprises a rear vertical plate 40, a horizontal supporting arm 41 arranged on the upper part of the front surface of the rear vertical plate, a vertical supporting plate 42 arranged on the front part of the lower surface of the horizontal supporting arm, and an air cylinder 43 arranged on the inner side of the joint of the vertical supporting plate and the horizontal supporting arm; the vertical supporting plate is provided with a bar-shaped opening, the right end of a telescopic rod of the air cylinder extends out of the front of the bar-shaped opening and is connected with the upper end of a lever 44, the middle part of the lever is rotationally connected with a supporting piece 45 arranged on the edge of the bar-shaped opening, the lower end of the lever is hinged with the right end of a horizontal rod 46, the left end of the horizontal rod is connected with a force hammer, the lower end of the vertical supporting plate is provided with a horizontal plate 47, the upper surface of the horizontal plate is provided with a transverse chute, the lower side of the force hammer is connected with a guide rod 48, the guide rod is in sliding connection with the transverse chute, and the distance between the supporting piece and the upper end of the lever is larger than the distance between the supporting piece and the lower end of the lever; the industrial robot is positioned between the rear vertical plate and the vertical supporting plate, and the force hammer is positioned in front of the outer periphery of the cylinder of the 6 th joint.
A measurement method of a measurement device for measuring a resonance frequency of an industrial robot, comprising the steps of:
step 1, enabling the X, Y, Z direction of each three-way accelerometer to coincide with a machine base coordinate system of an industrial robot, and installing a shock insulation base between the machine base of the industrial robot and the ground; energizing each motor to drive each joint to rotate;
step 2, the telescopic rod of the air cylinder drives the upper end of the lever to move back and forth, so that the power hammer moves back and forth, the power hammer approaches to and strikes the front side of the outer periphery of the cylinder of the 6 th joint, a transient impact force is provided for the industrial robot, the dynamic signal analyzer reads an input excitation signal delta (t) detected by the force sensor, and the dynamic signal analyzer reads a response signal y (t) of each three-way accelerometer, wherein t is time;
the upper computer carries out Fourier transformation on the response signal y (t) of each three-way accelerometer to obtain a frequency response function, reads the 1-order maximum point of the curve of the frequency response function according to the sequence from the small frequency value to the large frequency value of the frequency response function, and takes the 1-order maximum point as the resonance frequency of the industrial robot measured by each three-way accelerometer;
step 3, setting the measured resonance frequencies of the m three-way accelerometers to be f respectively 1 、f 2 、…、f m By f 1 ,f 2 ,…,f m Calculating the resonant frequency f of the industrial robot:
step 3-1, the transfer function of the known 6-degree-of-freedom industrial robot is:
b is the serial number of 5 three-way accelerometers, and b is more than or equal to 1 and less than or equal to 5; k represents the kth excitation point, the invention uses a force hammer to strike the front side of the cylinder of the 6 th joint, the force hammer only strikes the position, the invention has only one excitation point, and k=1; if the force hammer can strike other positions, a plurality of excitation points exist;
A b,k,i representing the remainder obtained according to the structure identification of the industrial robot; lambda (lambda) i Is the pole of the ith order mode of the industrial robot,is A b,k,i Is in the form of dual->Lambda is lambda i ω is the angular frequency of the transfer function;
step 3-2, setting an error e (ω) of the transfer function as:
wherein,
wherein H is b,k (ω) is a function frequency response prediction value of the industrial robot at ω,for the average value of the actual frequency response measurement values of each joint of the industrial robot at omega, H' b,k,i1 (ω) is an actual frequency response measurement at ω for each joint of the industrial robot; and the error of the transfer function is the integrated result of the individual joint errors, namely:
wherein H is b,k,i1 (ω) is the joint transfer function;
step 3-3, optimizing e (omega) by adopting a least square algorithm, and setting a function f (e (omega)) obtained after optimization as a weight function W (omega);
step 3-4, calculating f 1 ，f 2 ，…，f m Average value of (2)
Step 3-5, calculating f 1 ，f 2 ，…，f m Weight w of (2) 1 ，w 2 ,...,w m :
Step 3-6, calculating the resonant frequency f of the industrial robot by using the following formula:
the simultaneous measurement of a plurality of joints is to ensure the accuracy of measurement results, and 7 acceleration data can be formed by adding 2 three-way accelerometers to the 1 st joint and the 2 nd joint, and then the resonance frequency of the industrial robot can be obtained through a data average weighting method.
And (3) experimental effect analysis:
the six-axis industrial robot S5A901 is adopted, the resonance frequency of the six-axis industrial robot S5A901 is measured by using a sweep frequency method, and the 1-order resonance frequency is determined to be 10.2HZ, but the sweep frequency method has the defects of long measurement time, more needed equipment, complex operation and high measurement cost.
Simultaneously, the resonance frequency of the six-axis industrial robot S5A901 is measured by adopting the method and the sweep frequency method, and the average value is obtained by measuring 5 times in each method.
The adopted three-way accelerometer is a MEMS zero-frequency sensor, the model is BWJ38511, the sensitivity is 2000mV/g, the measuring range is 2g, the frequency range (+ -3 dB) is 0-200Hz, and the appearance is 23mm multiplied by 20mm.
The model of the dynamic signal analyzer is as follows: MI-7008, grade A;
the impact hammer model is as follows: 086D05,0.23mV/N; the single-point method is simply referred to as a single-point method.
The experimental results obtained for both test methods are shown in the following table:
as can be seen from the above graph, the error of the resonance frequency measured by the multipoint method is only 1.3%, and the error measured by the single-point method is up to 6.9%, so that the accuracy of the multipoint measurement is obviously improved compared with that of the measurement by the single-point method, and the measurement result of the resonance frequency measured by the multipoint method is more accurate than that of the measurement method for only measuring 1 point.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (5)
1. The measuring device for measuring the resonant frequency of the industrial robot comprises a machine base (11), N joints (12) and N motors (13) which are respectively used for driving the corresponding joints to rotate, wherein the N joints are sequentially numbered according to the sequence from the near to the far from the machine base, and N is more than or equal to 4; the measuring device is characterized by comprising an end plate (14) connected with an N joint, m three-way accelerometers (1), a multichannel dynamic signal analyzer (2), an upper computer (3) and a force hammer (4); the 1 three-way accelerometer is respectively arranged in the middle of the outer surface of the end plate, in addition, the m-1 three-way accelerometer is respectively arranged on the (N-m+2) -th joint to the (N-th joint, and m is less than or equal to N; the three-way accelerometer is electrically connected with the multichannel dynamic signal analyzer, the multichannel dynamic signal analyzer is electrically connected with the upper computer, and the multichannel dynamic signal analyzer is electrically connected with the force sensor (401) arranged on the outer peripheral surface of the force hammer; the joint comprises a cylinder (121) with one end open, and the bottom plate of the cylinder is fixedly connected with the rotating shaft of the corresponding motor; in the N-m+2th joint to the N joint, for the joint of which the outer end of the opening end of the cylinder is exposed out of the outer peripheral surface of the industrial robot, the three-way accelerometer is arranged on the outer end surface of the opening end of the cylinder; the N-m+2th joint to the N-th joint, for the joints of the cylinder located within the outer peripheral surface of the industrial robot, the three-way accelerometer is mounted on the outer peripheral surface of the industrial robot near the outer end surface of the open end of the cylinder; the three-way accelerometer on the nth joint is arranged on the bottom plate of the cylinder;
in the N-m+2 joints to the N joints, for the joints, the outer end of the opening end of the cylinder is exposed out of the outer peripheral surface of the industrial robot, two sliding rails (2) are arranged on the outer end surface of the opening end of the cylinder, the extending directions of the two sliding rails are parallel to one diameter of the end surface of the opening end of the cylinder, and the two sliding rails are respectively positioned at two sides of the diameter;
the two slide rails are provided with a plurality of groups of through holes which are arranged at intervals along the extending direction of the slide rails, and one group of through holes comprises two through holes which are respectively positioned on the opposite side surfaces of the two slide rails; the two slide rails are fixedly connected with the corresponding three-way accelerometer through the clamp (3), the clamp comprises a base plate (31), a rectangular groove (32) arranged on the upper surface of the base plate, threaded holes (33) arranged on the rectangular groove, a front clamping plate (34) and a rear clamping plate (35) arranged on two sides of the threaded holes on the lower surface of the base plate; rectangular convex blocks (36) are arranged on the lower surface of the base plate between the front clamping plate and the rear clamping plate, vertical holes corresponding to the threaded holes are formed in the upper surface of the rectangular convex blocks, and threads are formed in the inner side walls of the vertical holes; a rear gap is arranged between the rear side surface of the rectangular lug and the rear clamping plate, a front gap is arranged between the front side surface of the rectangular lug and the front clamping plate, the rear gap and the front gap are respectively connected with two guide rails in a matched mode, and a threaded rod arranged on the three-way accelerometer is connected with the threaded hole and the vertical hole in a matched mode.
2. The measuring device for measuring the resonance frequency of the industrial robot according to claim 1, wherein two front elastic protrusions are provided on the front side of the rectangular bump, two rear elastic protrusions are provided on the rear side of the rectangular bump, the two front elastic protrusions are respectively connected with 2 front through holes of the 2 sets of through holes in a matching manner, and the two rear elastic protrusions are respectively connected with two rear through holes of the 2 sets of through holes in a matching manner.
3. The measuring device for measuring the resonance frequency of the industrial robot according to claim 1, further comprising a moving mechanism for the movement of the powered hammer, the moving mechanism comprising a rear vertical plate (40), a horizontal support arm (41) provided at the upper part of the front surface of the rear vertical plate, a vertical support plate (42) provided at the front part of the lower surface of the horizontal support arm, and a cylinder (43) provided at the inner side of the junction of the vertical support plate and the horizontal support arm; the vertical supporting plate is provided with a bar-shaped opening, the right end of a telescopic rod of the air cylinder extends out of the front of the bar-shaped opening and is connected with the upper end of a lever (44), the middle part of the lever is rotationally connected with a supporting piece (45) arranged on the edge of the bar-shaped opening, the lower end of the lever is hinged with the right end of a horizontal rod (46), the left end of the horizontal rod is connected with a force hammer, the lower end of the vertical supporting plate is provided with a horizontal plate (47), the upper surface of the horizontal plate is provided with a transverse chute, the lower side of the force hammer is connected with a guide rod (48), the guide rod is in sliding connection with the transverse chute, and the distance between the supporting piece and the upper end of the lever is larger than the distance between the supporting piece and the lower end of the lever; the industrial robot is located between the rear vertical plate and the vertical supporting plate, and the force hammer is located in front of the outer periphery of the cylinder of the Nth joint.
4. A measurement method based on the measurement device for measuring the resonance frequency of an industrial robot according to claim 1, characterized by comprising the steps of:
step 1, enabling the X, Y, Z direction of each three-way accelerometer to coincide with a machine base coordinate system of an industrial robot, and installing a shock insulation base between the machine base of the industrial robot and the ground; energizing each motor to drive each joint to rotate;
step 2, knocking an Nth joint by using a force hammer, providing a transient impact force for the industrial robot, reading an input excitation signal delta (t) detected by a force sensor by a dynamic signal analyzer, and reading a response signal y (t) of each three-way accelerometer by the dynamic signal analyzer, wherein t is time;
the upper computer carries out Fourier transformation on the response signal y (t) of each three-way accelerometer to obtain a frequency response function, reads the maximum value point of the curve of the frequency response function according to the sequence from the small frequency value to the large frequency value of the frequency response function, and the frequency corresponding to the read maximum value point is the resonance frequency of the industrial robot measured by each three-way accelerometer;
step 3, setting the measured resonance frequencies of the m three-way accelerometers to be f respectively 1 、f 2 、…、f m By f 1 ,f 2 ,…,f m The resonant frequency f of the industrial robot is calculated.
5. The method for measuring a resonant frequency of an industrial robot according to claim 4, wherein step 3 comprises the steps of:
step 3-1, the transfer function of the known Z-degree-of-freedom industrial robot is:
b is the serial number of m three-way accelerometers, and b is more than or equal to 1 and less than or equal to m; k represents the kth excitation point, and k is more than or equal to 1; a is that b,k,i Representing the remainder obtained according to the structure identification of the industrial robot; lambda (lambda) i Is the pole of the ith order mode of the industrial robot,is A b,k,i Is in the form of dual->Lambda is lambda i ω is the angular frequency of the transfer function, j is the imaginary number;
step 3-2, setting an error e (ω) of the transfer function as:
wherein,
wherein H is b,k (ω) is a function frequency response prediction value of the industrial robot at ω,for the average value of the actual frequency response measurement values of each joint of the industrial robot at omega, H' b,k,i1 (ω) is an actual frequency response measurement at ω for each joint of the industrial robot; and the error of the transfer function is the integrated result of the individual joint errors, namely:
wherein H is b,k,i1 (ω) is the joint transfer function;
step 3-3, optimizing e (omega) by adopting a least square algorithm, and setting a function f (e (omega)) obtained after optimization as a weight function W (omega);
step 3-4, calculating f 1 ，f 2 ，…，f m Average value of (2)
Step 3-5, calculating f 1 ，f 2 ，…，f m Weight w of (2) 1 ，w 2 ,...,w m :
Step 3-6, calculating the resonant frequency f of the industrial robot by using the following formula:
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