vexide_math/
pid.rs

1//! PID controllers.
2//!
3//! PID controllers are first created with [`PidController::new`]
4//! and then can be utilized by calling [`PidController::update`] repeatedly.
5
6use core::time::Duration;
7
8/// A proportional–integral–derivative controller.
9///
10/// This controller is used to smoothly move motors to a certain point,
11/// and allows for feedback-based power adjustments. This is desirable
12/// over just setting the motor power, as it can be tuned to make the
13/// motor stop in exactly the right position without overshooting.
14#[derive(Debug, Clone, Copy)]
15pub struct PidController {
16    /// Proportional constant. This is multiplied by the error to get the
17    /// proportional component of the output.
18    pub kp: f32,
19    /// Integral constant. This accounts for the past values of the error.
20    pub ki: f32,
21    /// Derivative constant. This allows you to change the motor behavior
22    /// based on the rate of change of the error (predicting future values).
23    pub kd: f32,
24
25    last_time: vexide_core::time::Instant,
26    last_position: f32,
27    i: f32,
28}
29
30impl PidController {
31    /// Create a new PID controller with the given constants.
32    pub fn new(kp: f32, ki: f32, kd: f32) -> Self {
33        Self {
34            kp,
35            ki,
36            kd,
37            last_time: vexide_core::time::Instant::now(),
38            last_position: 0.0,
39            i: 0.0,
40        }
41    }
42
43    /// Update the PID controller with the current setpoint and position.
44    pub fn update(&mut self, setpoint: f32, position: f32) -> f32 {
45        let mut delta_time = self.last_time.elapsed();
46        if delta_time.is_zero() {
47            delta_time += Duration::from_micros(1);
48        }
49        let error = setpoint - position;
50
51        self.i += error * delta_time.as_secs_f32();
52
53        let p = self.kp * error;
54        let i = self.ki * self.i;
55
56        let mut d = (position - self.last_position) / delta_time.as_secs_f32();
57        if d.is_nan() {
58            d = 0.0
59        }
60
61        let output = p + i + d;
62
63        self.last_position = position;
64        self.last_time = vexide_core::time::Instant::now();
65
66        output
67    }
68}
vexide_math/pid.rs

vexide_math/
pid.rs
