Vibration model composition This laboratory bench consists of masses, sensors, front and rear suspension systems, excitation systems, and benches. The vibration model is shown schematically. The mass M is 1/100 of the prototype of the tracked vehicle and is supported on the steel rod and spring on the pallet. The suspension system is mounted between the spring-loaded mass and the tray, and the suspension system includes two parallel suspension springs K and a magneto-rheological damper C, all located on the mass median line. The excitation system consists of a cam mechanism, a power source, etc. The power source of the excitation system is a variable-speed variable-frequency motor, which drives the chain and drives the cam to make a circle so that the tray moves, which in turn drives the mass upward and downward and generates an excitation for the shock absorber.
Calculation of vibration model parameters In order to determine the structural parameters of the model, the following basic principles must be followed: that is, the requirements of similar laws should be met between the model and the prototype. To do this, first analyze and determine the similarity of the system. Design Principle The cam is a member with a curved profile or groove, which can achieve any desired movement during movement by simulating the contour of the follower. It simulates the sinusoidal road surface of the vehicle and obtains excitation input that meets the test requirements. Through experimental verification, the excitation system programmed by Visual Basic is used to simulate the sinusoidal road surface with accurate wavelength and economical processing, which meets the test requirements. The most typical road profile after track or wheel vehicle rolling over the dirt road can be summarized as the superposition of various amplitudes and the harmonic path type at the round frequency.
Tracked vehicles are more complex in the actual driving process. It is impossible to consider all kinds of non-planar roads. Therefore, only the most typical non-planar is selected as the input of interference. Assume that the road surface frequency and elevation passed by the vehicle are constant and ignore the influence of the track. The excitation (road) function obtained by the suspension system is: f=hsin(2Lx). According to the relative relativity of motion, when a road wheel with a radius R is moving at a constant speed on the road surface function f=hsin(2Lx), the trajectory at the axis is the same as the function, so the outer contour is =R-hsin. This is also a function of the trajectory of the cam at the axis when the cam is moving at the same speed in the horizontal plane. As a graphic design, as shown in the disc cam, the harmonic wave conforms to the law of cosine acceleration motion, and the theoretical contour line is expressed in polar coordinates as: R-hsin(k1).
According to Russian statistics, the average wavelength of continuous rolling road is 7m～16m, and the difference between the most convex and concave road surface is 0.2m～0.4m. According to the similarity ratio, the simulation wavelength of typical sinusoidal road surface simulated by cam outer edge should be simulated. Wavelength L = 70mm ~ 160mm, analog wave height h = 1mm ~ 2mm. Example According to the GB/T276-1994 primary selection 60,000 series model bearing, the inner diameter of 30mm, outer diameter of 42mm, width 7mm. At this time take the analog wavelength L = 160mm, h = 2mm, bearing outer radius r = 21mm, from R = k1 ∫ L01 + 2dx2, calculated base circle radius R1 = 12.7990mm. Due to the heavier cam bearing, requires a larger shaft diameter, taking into account the need to subtract corresponding The amount of ball bearing radius, therefore, take the number of analog waves k1 = 5, that is, the cam rotates one revolution and obtains five analog wavelengths at the theoretical contour line. Calculate the theoretical contour radius R2=63.9045 and take 64mm. At this time, the theoretical contour line polar equation is =64+2sin(5), the actual contour line is =64-21cos+2sin(5), and the pressure angle is equal to arctan ( 10cos(5)64). By using VB for secondary development of AutoCAD, the program runs to generate the results.scr file as shown. The dashed line represents the theoretical outline and the solid line represents the actual outline.
Cam profile 3 generated by scr format condition monitoring and control system condition monitoring system principle. The state monitoring system uses acceleration sensors, line displacement sensors, and force sensors. Acquisition card selects USB2000A type, the card is equipped with 12Bit resolution A/D converter, providing users with 32 single-ended and 16 dual-ended analog signal input channels. The acquisition card comes with a clock and a timer. After the first and last channels are set, the analog signal is input from the interface, output to the A/D converter via the amplifier, the conversion result is written to the memory FIFO, and finally the data is sent to the computer via the USB system. . The sensor collects the shaking table and the excitation source signal. After conditioning, the acquisition card is input into the computer. Processing and analysis are performed on the virtual instrument measurement and control platform based on LabVIEW. Then the required control current is calculated according to the vibration reduction requirements, and then the virtual instrument is passed. Control the output of the adjustable power supply and control the damping force to achieve vibration reduction.
Concluding remarks The similarity theory is used to simulate the semi-active suspension simulation test rig based on simple harmonic excitation, which can simulate the common road surface on which a tracked vehicle travels. Based on the principles of geometric similarity and dynamic similarity, this article discusses the design principles of the vibration test bench and calculates the parameters. The input to its excitation is analyzed from the principle to the example, and the principle and implementation method of the condition monitoring and control system are discussed.
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