PID Theory and Practice Part 3, P,I,PI Control of Speed

Overview of PID controllers starting with basic definitions through using PI / PD controllers for controlling a (simulated) DC motor

Part 1
Definitions, basic terms

Part 2
Simple DC motor model

Part 3
P, I, and PI control of motor velocity

Part 4
Practical considerations
Simple tuning rules

Part 5
PI, PD, and PID control of motor position

Psuedo Code for a PID controller - Typically only the P and I parts or P and D parts would be used.

Const F32 P_Gain = 1; // Gain for proportional controller
Const F32 I_Gain = .1; // Gain for integral controller
Const F32 D_Gain = .01 // Gain for derivative controller
Const F32 Filter_Const = .25 // Filter constant for filtering input to derivative controller
// minimum value = 0, maximum value = 1
F32 P_Control; // output of proportional controller
F32 I_Control; // output of integral controller
F32 D_Control; // output of integral controller
F32 Filter_Out; // output of filter
F32 Filter_Out_Prev // previous output of thefilter - use to get delta change
Const F32 Target_Value = 100; // target set point for controller
F32 Measured_Value; // measured plant output
F32 Error_Value; // difference between desired and measured plant output.
F32 PID_Out; // final controller output value
F32 Loop_Time // time for one control loop - could be a constant or a measured value

Measured_Value = input(); // get A/D reading -- convert units if necessary
Error_Value = Target_Value -- Measured_Value;

P_Control = P_Gain * Error_Value;

I_Control = I_Control + I_Gain * Error_Value * Loop_Time; // integrate error * gain*delta time
// If you leave out the loop time, you can adjust the gain value to somewhat compensate

Filter_Out_Prev = Filter_Out; // save previous value
Filter_Out = Filter_Const*Error_Value + (1-Filter_Constant)* Filter_Out;
// take a portion of the new input and a portion of the old value to average out over several samples
// simulate a first order exponential filter.
D_Control = D_Gain * (Filter_Out - Filter_Out_Previous) / Loop_Time; // derivative output based on filtered value

PID_Out = P_Control + I_Control + D_Control; // Final output

[robbievalentine]

Where are the rest of the videos? These are very enlightening! Great job!

[LightAndSportyGuy]

How are you planning to control the induction motor?
Changing voltage usually has only a little effect on the speed - the speed is primarily a function of the AC frequency and the number of poles in the motor. Some induction motors are wired to let you select different numbers of poles to have a few specific speeds - otherwise you typically use a variable frequency source. The motor itself is pretty non-linear with the stable and unstable operating areas. I've never modeled one myself.

[zk]

Thank you for your sharing, quite useful for my project.

[bilalsarwari]

According to the plot at 2:30 the applied step voltage is only 50V, while the target speed is 500RPM. Isnt the input signal supposed to be equal to the desired output?

[sukhvirmani]

hello sir, i working on my project to control the speed of induction motor with simple PID contorller only, please help me how make the transfer fuction of induction motor with pid controller

[piglink]

why does error x gain (kp) give you voltage?

[bellamano]

plzz can u help me, t want PI with AC induction motor on simulink