Discrete Control Loops Simulator

This project implements the control of two systems: Motor Speed Control and Cruise Control, and allows the user to tune some parameters and visualize different outputs thanks to a custom GUI. It is archieved thanks to three concurrent actions, two discrete control loops and a supervision task.

The software uses many classes to make the code easier to process. The following class diagram describes them and how they interact with each other:

Follow this link (Spanish) to a document with extra diagrams and explanations.

Control loops general description.

Two discrete control loops are implemented. In each of them, two threads corresponding to the Regulator (R) and Plant (G) are executed in a cyclic manner. Each control loop has a different period: 50 ms for the Motor Speed Control and 20 ms for the Cruise Control.

The Motor Speed Control (T = 50 ms) is implemented by the following equations:

$$R_{Motor}=Kp\times \frac{414.1z^2-647.8z+250.1}{z^3+0.82z^2-z-0.82}$$ $$G_{Motor}=\frac{0.0005663z+0.0005125}{z^2-1.73z+0.7408}$$

The following sequence diagram describes how the loop works:

The Cruise Control (T = 20 ms) is implemented by the following equations:

$$R_{Cruise}=Kp\times \frac{414.1z^2-647.8z+250.1}{z^3+0.82z^2-z-0.82}$$ $$G_{Cruise}=\frac{0.0005663z+0.0005125}{z^2-1.73z+0.7408}$$

The following sequence diagram describes how the loop works:

The inputs to this systems are always considered to be steps. Their amplitude can be modifyed in the GUI.

Control loops threads.

There is no alternating between the execution of the threads in each control loop. Eaxh of them activates according to its period and will work with the available data at the time. The following sequence of threads happens inside each control loop:

Regulator thread.

It is held inside the class Regulator.

1. The thread executes method Read( int channel, int *datareg) from the class Conversor. This is a function that simulates the capture of an analog signal and its conversion to a discrete value, giving Yk, the last value of the control loop output.
2. The error is calculated and stored as a field of the class Variables Compartidas ( Shared Variables). These are the variables shared betwween plant and regulator:

$$E_k=Y_k-ref$$

3. The regulator thread stops executing until its next activation period.

Plant thread

It is held inside the class Plant.

1. The corresponding plant takes the shared variable Uk (output of the regulator, control action) and generates a new Yk (also a shared variable). This task is two times faster than its regulator.
2. The plant thread stops executing until its next activation period.

Sensor simulation

The Sensor class provides a voltage value to an angular velocity. Yk is only known by the system after passing through the sensor and the conversor. The following table describes sensor specifications:

Gain	Ratio [mV/(rad/s)]
500	1

Conversor

It is a simulated ADC thread (includin the sensor in the thread) with two hardware registers: CSR (Control State Register, 8 bit) and DR (Data Register). It works between -10 and +10 V with 12 bit resolution. CSR is detailed in the following table:

Function	Bit(s)
ERROR	[0, 1]
IE	2
DONE	3
CH	[4, 5]
-	6
START	7

The function Read( int channel, int *datareg) uses the channel (0 for Motor, 1 for Cruise) and the memory location where the 12 bit int that has just been read will be stored. There is only one Conversor, therefore only one Regulator can use this method at a time. Before executing the operation, CSR must be in initial conditions:

csr.ERROR=0;                    // Poner el error a 0
csr.IE=1;                       // Habilitar interrupción
csr.DONE=0;                     // Done a 0
csr.CANAL=Ncanal;               // Seleccion de canal
csr.START=1;                    // Inicio de conversión

GUI

User-case diagram:

The graphic interface shows for each control loop:

• Last 5 output values (Yk) with a button to refresh them.
• Reference adjustemnt slider.
• Box to modify regulator's gain (Kp) value.
• Exit button.
• A graph showing the system's output against the reference.