From the block diagram of the test machine system, the gains of the three control loops are as follows: the open loop gain of the force control loop Kt1=KaKqKLAPKe; the open loop gain of the displacement control loop Kt2=KaKqKnApKceG; the open loop gain of the deformation control loop Kt3=KaKqKmApKeKδ; The open-loop gain of each loop is considered together with ωr=KeAP2(1/G+1/Kh) and ωc=Ktiωr. It can be seen that: (1) The three control loops are all differential system or type systems. The displacement control system consists of one inertia link and two second-order links. The force control system and the strain control system also have a second-order differential link. This type of O-system generally has contradictions in stability, steady-state accuracy, and rapidity. It is necessary to use the PID link to correct the control system. (2) The stiffness of the test piece directly affects the total stiffness of the system G, G varies greatly with the stiffness of the test piece. The test machine generally adjusts the PID parameters according to the large stiffness test piece before leaving the factory. If the PID parameters are no longer adjusted when the user uses it, the stability of the test piece is usually small, so the stability of the system is not a problem when using the load feedback loop, but the closed loop frequency The width is reduced; the displacement and deformation loops are reversed, the bandwidth is not a problem, but the stability is degraded and even becomes unstable. Therefore, the appropriate scale factor should be selected according to the stiffness of the test piece. P. The proportional coefficient P is adjusted properly and can be reflected in the reverberation sound of the test machine. If the P is insufficient, the working condition of the testing machine is weak and the rhythm is slow; when it is too large, there is oscillation and noise. (3) Since the gains in the three feedback loops are different, in order to achieve the bumpless switching without stopping the test, the "second-order error approaching zero" conversion method can be adopted in the control system, that is, by adjusting the to-be-converted (non-control) The magnitude of the error is such that when the difference between the error under the closed-loop control and the error to be converted (non-control) is zero, the trigger switching is performed to ensure that the servo valve operating current does not change before and after the switching, thereby achieving the conversion of the test process. No disturbance. (4) The hydraulic spring stiffness Kh increases, the open loop gain does not change and ωr increases, so that the crossing frequency ωc increases. The total flow-pressure coefficient Ke has an effect on the open loop gain Kti and the corner frequency ωr of the inertia link, but has no effect on the crossing frequency ωc. Plastic Bottle Printing Machine Screen Printing Machine For Plastic Bottles,Pet Bottle Printing Machine,Plastic Bottle Screen Printing Machine,Bottle Silk Screen Printer GIG (DONGGUAN) CO., LTD , https://www.sennyprinter.com
The gain of the three control loops of the test machine