PID control algorithm is a widely used control algorithm, PID control has the advantages of adjustable parameters, wide range of applications, high control accuracy. In practical engineering, PID algorithm can be applied to electromechanical control, industrial automation, robot control, microprocessor control and many other fields.
The three parameters of PID algorithm are adjusted: proportionality constant Kp, integral time constant Ti, differential time constant Td. Different systems need to set different PID parameters, and it is generally necessary to obtain the optimal parameters through experiments and debugging. The proportionality constant Kp adjusts the proportion, adjusting the ratio of output and feedback error in the control system; the integral time constant Ti adjusts the integral, adjusting the accumulation of error in the control system; the differential time constant Td adjusts the differential, adjusting the rate of change of error in the control system.
What is the idea of realizing pid algorithm with microcontroller
To realize the PID control algorithm on a microcontroller, the following is the general idea of realization:
1. **Determine the PID parameters**:
- According to the characteristics and needs of the actual control object, select the appropriate proportionality coefficient (Kp), integration time (Ti) and differentiation time (Td).
2. **Sensor data acquisition**:
- Use appropriate sensors (e.g., temperature sensors, position sensors, etc.) to collect feedback data from the control object in real time.
3. **Set value and feedback value comparison**:
- Compare the set value (desired value) with the feedback value and calculate the error value (Error).
4. **PID calculation**:
- The control amount (output) is calculated according to the PID algorithm formula: PID = Kp * Error + Ki * ∫ Error dt + Kd * d(Error)/dt.
- Kp, Ki and Kd are the PID parameters, Error is the error value, ∫ Error dt denotes the integral term and d(Error)/dt denotes the differential term.
5. **Limit Handling** (optional):
- For some applications, it may be necessary to limit the range of the output value to avoid exceeding the acceptable range of the control object.
6. **Output control signal**:
- The calculated control quantity is output as a control signal to the actuator (e.g. motor, valve, etc.) to realize the regulation and control of the control object.
7. **Set control frequency**:
- According to the needs of specific applications, set the appropriate control frequency to control the execution cycle of the algorithm.
8. **Cycle execution of PID algorithm**:
- In the real-time cycle, the above steps are executed repeatedly to continuously monitor the feedback value, calculate the control quantity, and output the control signal to realize the stable control of the object.
In the actual microcontroller programming, you can choose the appropriate development tools and programming language (such as C or assembly language) according to the specific microcontroller model and development platform. It should be noted that in practical applications, there will be many techniques to optimize and improve the PID algorithm, such as integral separation, adaptive PID, etc., which can be further researched and implemented according to specific needs.
PID controller principle and workflow
The PID controller consists of three parts: proportional (P), integral (I) and differential (D), and generates the control output by processing the error, deviation and rate of change of the system. Its workflow includes the following steps:
- Obtaining target and feedback values
- Calculate the error
- Calculate the control output based on the proportionality coefficient, integral term and differential term.
- Updating the controller parameters
- Outputting control signals
STM32 code implementation
The following is sample code for designing and implementing a PID controller using an STM32 microcontroller:
```c
#include "stm32f4xx.h"
// Define the PID controller parameters
float Kp = 0.5; // scale factor
float Ki = 0.2; // Integral coefficient
float Kd = 0.1; // Differential coefficient
// Define storage variables
float setpoint = 50.0; // target value
float feedback = 0.0; // feedback value
float error = 0.0; // error
float last_error = 0.0; // last error
float integral = 0.0; // Integral term
// PID controller output calculation function
float pidController(float dt)
float pidController(float dt) {
// Calculate the error
error = setpoint - feedback; // Calculate the integral term.
// Calculate the integral term
integral += error * dt; // compute the differential term
// Calculate the differential
float derivative = (error - last_error) / dt; // compute the control output.
// Calculate the control output
float output = Kp * error + Ki * integral + Kd * derivative; // Calculate the control output.
// Update last error
last_error = error; // update last error.
last_error = error; return output; // Calculate the control output.
}
int main(void)
{
while(1)
{
// Get the feedback value
// Get the time interval
// Calculate the PID output
float dt = 0.01; // 0.01s as time interval in the example
float control_output = pidController(dt); // output the control signal.
// Output the control signal
// Delay the control signal for a certain period of time
for (int i = 0; i 《 10000;i++).
}
return 0; }
}