feat!: clean up Controller API

Remove return value from Controller.Update to align with the API of the
other controllers.

README.md

@@ -10,7 +10,7 @@ PID controllers for Go.
 
 ### `pid.Controller`
 
-A standard PID controller.
+A basic PID controller.
 
 ```go
 import (

controller.go

@@ -4,8 +4,10 @@ import "time"
 
 // Controller implements a basic PID controller.
 type Controller struct {
+	// Config for the Controller.
 	Config ControllerConfig
-	State  ControllerState
+	// State of the Controller.
+	State ControllerState
 }
 
 // ControllerConfig contains configurable parameters for a Controller.
@@ -41,18 +43,18 @@ type ControllerInput struct {
 }
 
 // Update the controller state.
-func (s *Controller) Update(input ControllerInput) float64 {
-	previousError := s.State.ControlError
-	s.State.ControlError = input.ReferenceSignal - input.ActualSignal
-	s.State.ControlErrorDerivative = (s.State.ControlError - previousError) / input.SamplingInterval.Seconds()
-	s.State.ControlErrorIntegral += s.State.ControlError * input.SamplingInterval.Seconds()
-	s.State.ControlSignal = s.Config.ProportionalGain*s.State.ControlError +
-		s.Config.IntegralGain*s.State.ControlErrorIntegral +
-		s.Config.DerivativeGain*s.State.ControlErrorDerivative
-	return s.State.ControlSignal
+func (c *Controller) Update(input ControllerInput) {
+	previousError := c.State.ControlError
+	c.State.ControlError = input.ReferenceSignal - input.ActualSignal
+	c.State.ControlErrorDerivative = (c.State.ControlError - previousError) / input.SamplingInterval.Seconds()
+	c.State.ControlErrorIntegral += c.State.ControlError * input.SamplingInterval.Seconds()
+	c.State.ControlSignal =
+		c.Config.ProportionalGain*c.State.ControlError +
+			c.Config.IntegralGain*c.State.ControlErrorIntegral +
+			c.Config.DerivativeGain*c.State.ControlErrorDerivative
 }
 
 // Reset the controller state.
-func (s *Controller) Reset() {
-	s.State = ControllerState{}
+func (c *Controller) Reset() {
+	c.State = ControllerState{}
 }

controller_test.go

@@ -17,12 +17,12 @@ func TestSpeedControl_ControlLoop_OutputIncrease(t *testing.T) {
 		},
 	}
 	// Check output value when output increase is needed
-	assert.Equal(t, float64(121), pidControl.Update(ControllerInput{
+	pidControl.Update(ControllerInput{
 		ReferenceSignal:  10,
 		ActualSignal:     0,
 		SamplingInterval: 100 * time.Millisecond,
-	}))
-	// Check proportional error
+	})
+	assert.Equal(t, float64(121), pidControl.State.ControlSignal)
 	assert.Equal(t, float64(10), pidControl.State.ControlError)
 }
 
@@ -36,12 +36,12 @@ func TestSpeedControl_ControlLoop_OutputDecrease(t *testing.T) {
 		},
 	}
 	// Check output value when output value decrease is needed
-	assert.Equal(t, float64(0), pidControl.Update(ControllerInput{
+	pidControl.Update(ControllerInput{
 		ReferenceSignal:  10,
 		ActualSignal:     10,
 		SamplingInterval: 100 * time.Millisecond,
-	}))
-	// Check proportional error
+	})
+	assert.Equal(t, float64(0), pidControl.State.ControlSignal)
 	assert.Equal(t, float64(0), pidControl.State.ControlError)
 }