pid: Scale PID Parameters with Sampling Rate

- Breaking changes

pykirdy/asyncio_exmaple.py

@@ -85,21 +85,22 @@ async def ld_thermostat_cfg(kirdy: Kirdy):
     await kirdy.thermostat.set_temp_mon_upper_limit(70)
     await kirdy.thermostat.set_temp_mon_lower_limit(0)
 
-    # Configure the thermostat PID parameters.
-    # You can configure the PID parameter by the included autotune script.
-    await kirdy.thermostat.set_temperature_setpoint(25)
-    await kirdy.thermostat.set_pid_kp(0.15668282198105507)
-    await kirdy.thermostat.set_pid_ki(0.002135962407793784)
-    await kirdy.thermostat.set_pid_kd(0.829254515277143)
-    await kirdy.thermostat.set_pid_output_max(1.0)
-    await kirdy.thermostat.set_pid_output_min(-1.0)
-
     # Configure the thermostat ADC Filter Setting / PID Update Rate / Report Rate.
     # The ADC sampling rate determines the report and pid update rate.
     # The chosen filter and sampling rate affects the noise of the readings.
     # For details, please refer to the AD7172 datasheet.
     await kirdy.thermostat.config_temp_adc_filter(FilterConfig.Sinc5Sinc1With50hz60HzRejection.f16sps)
 
+    # Configure the thermostat PID parameters.
+    # You can configure the PID parameter by the included autotune script.
+    # You should configure the filter sampling rate first before applying pid parameters.
+    await kirdy.thermostat.set_temperature_setpoint(25)
+    await kirdy.thermostat.set_pid_kp(0.15668282198105507)
+    await kirdy.thermostat.set_pid_ki(0.0001281321)
+    await kirdy.thermostat.set_pid_kd(13.82367)
+    await kirdy.thermostat.set_pid_output_max(1.0)
+    await kirdy.thermostat.set_pid_output_min(-1.0)
+
     # Configure thermostat to run in PID control mode
     await kirdy.thermostat.set_pid_control_mode()
     

pykirdy/pid_autotune.py

@@ -45,6 +45,7 @@ class PIDAutotune:
             raise ValueError('setpoint must be specified')
 
         self._inputs = deque(maxlen=round(lookback / sampletime))
+        self._sampletime = sampletime
         self._setpoint = setpoint
         self._outputstep = out_step
         self._noiseband = noiseband
@@ -69,6 +70,7 @@ class PIDAutotune:
         self._out_min = -step
         self._noiseband = noiseband
         self._inputs = deque(maxlen=round(lookback / sampletime))
+        self._sampletime = sampletime
 
     def setReady(self):
         self._state = PIDAutotuneState.STATE_READY
@@ -96,8 +98,8 @@ class PIDAutotune:
     def get_tec_pid (self):
         divisors = self._tuning_rules["tyreus-luyben"]
         kp = self._Ku * divisors[0]
-        ki = divisors[1] * self._Ku / self._Pu
+        ki = divisors[1] * self._Ku / self._Pu / (1 / self._sampletime)
-        kd = divisors[2] * self._Ku * self._Pu
+        kd = divisors[2] * self._Ku * self._Pu * (1 / self._sampletime)
         return kp, ki, kd
 
     def get_pid_parameters(self, tuning_rule='ziegler-nichols'):
@@ -109,8 +111,8 @@ class PIDAutotune:
         """
         divisors = self._tuning_rules[tuning_rule]
         kp = self._Ku * divisors[0]
-        ki = divisors[1] * self._Ku / self._Pu
+        ki = divisors[1] * self._Ku / self._Pu / (1 / self._sampletime)
-        kd = divisors[2] * self._Ku * self._Pu
+        kd = divisors[2] * self._Ku * self._Pu * (1 / self._sampletime)
         return PIDAutotune.PIDParams(kp, ki, kd)
 
     def run(self, input_val, time_input):

src/thermostat/pid_state.rs

@@ -142,16 +142,16 @@ impl PidState {
         self.controller.parameters = pid_params;
     }
 
-    pub fn set_pid_params(&mut self, param: PidSettings, val: f32) {
+    pub fn set_pid_params(&mut self, param: PidSettings, val: f32, curr_rate: f32) {
         match param {
             PidSettings::Kp => {
                 self.controller.parameters.kp = val;
             }
             PidSettings::Ki => {
-                self.controller.parameters.ki = val;
+                self.controller.parameters.ki = val * curr_rate;
             }
             PidSettings::Kd => {
-                self.controller.parameters.kd = val;
+                self.controller.parameters.kd = val / curr_rate;
             }
             PidSettings::Min => {
                 self.controller.parameters.output_min = val;
@@ -162,6 +162,18 @@ impl PidState {
         }
     }
 
+    pub fn update_pid_params_with_new_sampling_rate(&mut self, old_rate: f32, new_rate: f32) {
+        self.controller.parameters.ki = self.controller.parameters.ki * old_rate / new_rate;
+        self.controller.parameters.kd = self.controller.parameters.kd * new_rate / old_rate;
+    }
+
+    pub fn get_abs_pid_params(&mut self, curr_rate: f32) -> Parameters {
+        let mut pid_params = self.controller.parameters.clone();
+        pid_params.ki = self.controller.parameters.ki / curr_rate;
+        pid_params.kd = self.controller.parameters.kd * curr_rate;
+        pid_params
+    }
+
     pub fn reset_pid_state(&mut self) {
         self.controller.u1 = 0.0;
         self.controller.x1 = 0.0;

src/thermostat/thermostat.rs

@@ -453,7 +453,8 @@ impl Thermostat {
     }
 
     pub fn set_pid(&mut self, param: PidSettings, val: f32) {
-        self.pid_ctrl_ch0.set_pid_params(param, val);
+        let curr_rate = self.ad7172.get_filter_type_and_rate(0).unwrap().3;
+        self.pid_ctrl_ch0.set_pid_params(param, val, curr_rate);
     }
 
     pub fn set_sh_beta(&mut self, beta: f32) {
@@ -492,20 +493,35 @@ impl Thermostat {
     }
 
     pub fn set_temp_adc_sinc5_sinc1_filter(&mut self, index: u8, odr: ad7172::SingleChODR) {
+        let old_rate = self.ad7172.get_filter_type_and_rate(0).unwrap().3;
+        let new_rate = odr.output_rate().unwrap();
+        self.pid_ctrl_ch0
+            .update_pid_params_with_new_sampling_rate(old_rate, new_rate);
         self.ad7172.set_sinc5_sinc1_filter(index, odr).unwrap();
     }
 
     pub fn set_temp_adc_sinc3_filter(&mut self, index: u8, odr: ad7172::SingleChODR) {
+        let old_rate = self.ad7172.get_filter_type_and_rate(0).unwrap().3;
+        let new_rate = odr.output_rate().unwrap();
+        self.pid_ctrl_ch0
+            .update_pid_params_with_new_sampling_rate(old_rate, new_rate);
         self.ad7172.set_sinc3_filter(index, odr).unwrap();
     }
 
     pub fn set_temp_adc_sinc5_sinc1_with_postfilter(&mut self, index: u8, odr: ad7172::PostFilter) {
+        let old_rate = self.ad7172.get_filter_type_and_rate(0).unwrap().3;
+        let new_rate = odr.output_rate().unwrap();
+        self.pid_ctrl_ch0
+            .update_pid_params_with_new_sampling_rate(old_rate, new_rate);
         self.ad7172
             .set_sinc5_sinc1_with_50hz_60hz_rejection(index, odr)
             .unwrap();
     }
 
     pub fn set_temp_adc_sinc3_fine_filter(&mut self, index: u8, rate: f32) {
+        let old_rate = self.ad7172.get_filter_type_and_rate(0).unwrap().3;
+        self.pid_ctrl_ch0
+            .update_pid_params_with_new_sampling_rate(old_rate, rate);
         self.ad7172.set_sinc3_fine_filter(index, rate).unwrap();
     }
 
@@ -548,7 +564,7 @@ impl Thermostat {
             pid_engaged: self.get_pid_engaged(),
             temperature_setpoint: self.pid_ctrl_ch0.get_pid_setpoint(),
             tec_settings: self.get_tec_settings(),
-            pid_params: self.get_pid_settings(),
+            pid_params: self.pid_ctrl_ch0.get_abs_pid_params(temp_adc_settings.rate.unwrap()),
             temp_adc_settings: temp_adc_settings,
             temp_mon_settings: self.get_temp_mon_settings(),
             thermistor_params: self.get_steinhart_hart(),
@@ -580,6 +596,7 @@ impl Thermostat {
 
         self.set_pid_engaged(settings.pid_engaged);
         self.pid_ctrl_ch0.apply_pid_params(settings.pid_params);
+        self.pid_ctrl_ch0.update_pid_params_with_new_sampling_rate(settings.temp_adc_settings.rate.unwrap(), 1.0);
         self.set_temperature_setpoint(settings.temperature_setpoint);
         if !settings.pid_engaged {
             self.set_i(settings.tec_settings.i_set.value);