[0052] Embodiment: A method for automatic adjustment of excitation voltage of electrodynamic vibration table
[0053] Assuming the rated current value I of the moving coil when the system is running at full thrust 2 is 1000A; rated excitation output voltage value V 2 is 100V; the adjustment coefficient δ is selected as 0.1.
[0054] like figure 2 As shown in the figure, the excitation voltage automatic adjustment system of the electric vibrating table is mainly composed of a current detection circuit, a control circuit and an excitation voltage adjustment circuit, wherein the control circuit and the excitation voltage adjustment circuit constitute a closed-loop control adjustment. In addition, the acceleration measurement sensor, the controller and the power amplifier constitute a closed-loop control system that automatically increases the moving coil current.
[0055] The excitation voltage automatic adjustment method of the present invention is as follows:
[0056] (1) After the tested equipment or components are installed on the electric vibration table, use the electric vibration table to start the pre-test process, and on the premise of satisfying the formal vibration test parameters, use the current detection circuit to detect the pre-test of the power amplifier output to the moving coil The maximum current value of the moving coil I 1 is 600A.
[0057] (2) After the pre-test, according to the relationship between the moving coil current and the thrust of the electric vibration table, the maximum current value I of the moving coil detected in the pre-test is used. 1 , the target value V of the adjusted excitation output voltage is automatically calculated by the following formula in the control circuit 1 :
[0058] V 1 =(I 1 /I 2 +δ)×V 2 =(600A/1000A+0.1)×100V=70V
[0059] (3) Using the control circuit, the excitation output voltage is closed-loop adjusted to the target value by adjusting the conduction angle of the thyristor excitation rectifier module, or by modulating the pulse width duty cycle of the switching power supply.
[0060] (4) After the excitation output voltage is adjusted to the target value, the excitation output voltage is maintained until reselection adjustment or power amplifier restart.
[0061] In the control circuit, the closed-loop adjustment of the output voltage of the excitation rectifier module includes an excitation output voltage detection circuit, and the output value of the detection circuit is compared with the target value to control the adjustment of the excitation output voltage. Generally speaking, there are two forms of excitation voltage regulation circuit, the first is to use thyristor excitation voltage regulation and rectifier module, and the second is to use switching power supply excitation voltage regulation module. For the first form, the excitation output voltage can be adjusted by adjusting the conduction angle of the thyristor, see image 3 shown. The stepless adjustment of the output DC voltage can be realized under the control of the control circuit. The G1 to G6 terminals are the control terminals, which control the conduction phase of the thyristor under the control of the control circuit. The thyristor rectifier module is used as the rectifier unit, which can smoothly adjust the output voltage, which meets the requirement that the excitation voltage can be continuously adjusted after the pre-test operation. For the second form, the excitation output voltage can be adjusted by modulating the pulse width duty cycle, see Figure 4 shown. Its basic circuit structure and modulation principle are as follows: PWM voltage regulation circuit is mainly composed of triangular wave generator, PWM circuit, signal distributor and drive circuit. The PWM generation circuit uses the triangular wave generated by the triangular wave generator to be amplified and compared with an adjustable DC voltage. The output of the voltage comparator is a series of square wave signals. If the size of the control signal changes, the square wave pulse width will change, so as to achieve the purpose of adjusting the output voltage.
[0062] In the present invention, in order to ensure the continuous and stable operation of the system, the excitation output voltage is adjusted in place at one time after the pre-test, and the excitation output voltage is maintained until re-selection adjustment or restart of the power amplifier. There are two ways to maintain the excitation output voltage:
[0063] (1) After the excitation output voltage is adjusted to the target value, the self-characteristics of the closed-loop adjustment control are used to maintain the stability of the excitation output voltage.
[0064] (2) After the excitation output voltage is adjusted to the target value, directly keep the conduction angle or the duty cycle of the pulse width unchanged to maintain the stability of the excitation output voltage.
[0065] The process of automatically adjusting the excitation output voltage is described as follows:
[0066] (1) The controller sets up the vibration test program and prepares for the vibration test.
[0067] (2) Start the power amplifier.
[0068] (3) Select automatic adjustment of excitation output voltage (or not adjusted).
[0069] (4) Run the pre-test. When the pre-test is in progress, the control circuit always detects the output current of the power amplifier (ie, the current input to the moving coil), and samples the maximum value.
[0070] (5) The control circuit substitutes the maximum current value recorded by sampling into the calculation formula to calculate the target value of the excitation output voltage.
[0071] (6) Generate a control signal to the excitation voltage adjustment circuit through the comparison control circuit until the excitation voltage reaches the target value. Because both the control device and the actuator are electronic components, the adjustment time is short. After the adjustment, the system will no longer adjust the excitation voltage except to re-select the automatic adjustment, but the system will automatically restore the rated excitation output voltage when the system restarts.
[0072] The scope of application of the present invention to automatically adjust the excitation output voltage is as follows:
[0073] (1) The maximum thrust of the shaking table required for this test is smaller than the rated thrust of the shaking table, and there is a large gap, such as more than 20%.
[0074] (2) It is suitable for long-term vibration test, such as 2 hours. The short-term vibration test is of little significance.
