Matlab / Simulink simulation of double closed loop DC speed regulation system

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One 、 System principle and block diagram

Because the speed single closed-loop system can not fully control the dynamic process of current as required , For some production machines, different speed and current values are required under different production conditions , That is, there are two kinds of negative feedback of speed and current , Therefore, speed and current regulators are adopted .ACR Form an inner ring ,ASR Form an outer ring , Double closed-loop speed regulation system .

In actual modeling , There will be some differences in the system , The feedback link should become a low-pass filter with a small inertia link , The input should also have a corresponding inertia link .（ The following figure shows the current ring and speed converter respectively ）

Two 、 Parameter calculation and design

When designing double closed-loop speed regulation system , Generally, the inner ring is first followed by the outer ring , The structure and parameters of the regulator depend on the requirements of steady-state accuracy and dynamic correction , The design and debugging of dynamic correction of double closed-loop speed regulation system are carried out in the order of inner loop first and then outer loop , In the dynamic process, it can be considered that the outer ring has little effect on the inner ring , The inner ring is an integral part of the outer ring .

3、 ... and 、 Current loop simulation block diagram

We need to use integral module and proportional module to build PI controller , Then add a limiting module at the output end . Set the output limiting of the integration module , Set it to the same limiting amplitude as the limiting module , thus ,PI The controller has the same working characteristics as the actual analog controller .

Four 、 Current loop simulation results

KT=0.25, No overshoot , But the rise time is long

KT=1, Overshoot , Short rise time

5、 ... and 、 Double closed loop simulation block diagram

The current regulator acts as the regulator of the inner ring , In the process of adjusting the speed of the outer ring , Its function is to make the current follow its given voltage ( That is, the output of the outer ring regulator ) change . The corresponding relationship between speed and current is reflected in the oscilloscope module .

6、 ... and 、 Double closed loop simulation results

ASR The regulator is unsaturated , saturated , Desaturation has three stages , Finally, it operates stably at a given speed . When the DC motor reaches the steady-state speed , The current drops rapidly , Ensure that the output matrix is balanced with the load torque , The motor enters a stable operation state .

Given 10V, No load

Given 10V, Full load

Add load current at the input of load current . After no-load start to stable operation, start at 4s Speed and current response curve when disturbed by rated load . It can be seen that the speed decreases after loading , The current rises and the speed rises again , It is still the given speed in steady state .

7、 ... and 、 Simulation summary

In the dynamic process of DC motor rotor speed , The current regulator can ensure the maximum current allowed by the motor , So as to speed up the dynamic process . When the motor is overloaded or even locked , Limit the maximum armature current , Protection . Once the fault disappears , The system automatically returns to normal immediately .

The correspondence of the outer ring is slower than that of the inner ring , This is the characteristic of designing multi loop control system according to engineering design method , Although it is not conducive to rapidity , But each control loop itself is stable , It is conducive to the composition and debugging of the system .