fix(pid_longitudinal_controller): change pid structure with respect to design

Signed-off-by: Berkay Karaman <brkay54@gmail.com>

Author: brkay54

control/pid_longitudinal_controller/include/pid_longitudinal_controller/pid.hpp

@@ -29,14 +29,15 @@ class PIDController
   /**
    * @brief calculate the output of this PID
    * @param [in] error previous error
+   * @param [in] error_filtered filtered error
    * @param [in] dt time step [s]
    * @param [in] is_integrated if true, will use the integral component for calculation
    * @param [out] pid_contributions values of the proportional, integral, and derivative components
    * @return PID output
    * @throw std::runtime_error if gains or limits have not been set
    */
   double calculate(
-    const double error, const double dt, const bool is_integrated,
+    const double error, const double error_filtered, const double dt, const bool is_integrated,
     std::vector<double> & pid_contributions);
   /**
    * @brief set the coefficients for the P (proportional) I (integral) D (derivative) terms

control/pid_longitudinal_controller/src/pid.cpp

@@ -32,7 +32,7 @@ PIDController::PIDController()
 }
 
 double PIDController::calculate(
-  const double error, const double dt, const bool enable_integration,
+  const double error, const double filtered_error, const double dt, const bool enable_integration,
   std::vector<double> & pid_contributions)
 {
   if (!m_is_gains_set || !m_is_limits_set) {
@@ -55,12 +55,12 @@ double PIDController::calculate(
     error_differential = 0;
     m_is_first_time = false;
   } else {
-    error_differential = (error - m_prev_error) / dt;
+    error_differential = (filtered_error - m_prev_error) / dt;
   }
   double ret_d = p.kd * error_differential;
   ret_d = std::min(std::max(ret_d, p.min_ret_d), p.max_ret_d);
 
-  m_prev_error = error;
+  m_prev_error = filtered_error;
 
   pid_contributions.resize(3);
   pid_contributions.at(0) = ret_p;

control/pid_longitudinal_controller/src/pid_longitudinal_controller.cpp

@@ -1064,8 +1064,8 @@ double PidLongitudinalController::applyVelocityFeedback(const ControlData & cont
   const double error_vel_filtered = m_lpf_vel_error->filter(diff_vel);
 
   std::vector<double> pid_contributions(3);
-  const double pid_acc =
-    m_pid_vel.calculate(error_vel_filtered, control_data.dt, enable_integration, pid_contributions);
+  const double pid_acc = m_pid_vel.calculate(
+    diff_vel, error_vel_filtered, control_data.dt, enable_integration, pid_contributions);
 
   // Feedforward scaling:
   // This is for the coordinate conversion where feedforward is applied, from Time to Arclength.

control/pid_longitudinal_controller/test/test_pid.cpp

@@ -29,14 +29,14 @@ TEST(TestPID, calculate_pid_output)
   PIDController pid;
 
   // Cannot calculate before initializing gains and limits
-  EXPECT_THROW(pid.calculate(0.0, dt, enable_integration, contributions), std::runtime_error);
+  EXPECT_THROW(pid.calculate(0.0, 0.0, dt, enable_integration, contributions), std::runtime_error);
 
   pid.setGains(1.0, 1.0, 1.0);
   pid.setLimits(10.0, 0.0, 10.0, 0.0, 10.0, 0.0, 10.0, 0.0);
   double error = target - current;
   double prev_error = error;
   while (current != target) {
-    current = pid.calculate(error, dt, enable_integration, contributions);
+    current = pid.calculate(error, error, dt, enable_integration, contributions);
     EXPECT_EQ(contributions[0], error);
     EXPECT_EQ(contributions[1], 0.0);  // integration is deactivated
     EXPECT_EQ(contributions[2], error - prev_error);
@@ -50,18 +50,18 @@ TEST(TestPID, calculate_pid_output)
   enable_integration = true;
 
   // High errors to force each component to its upper limit
-  EXPECT_EQ(pid.calculate(0.0, dt, enable_integration, contributions), 0.0);
+  EXPECT_EQ(pid.calculate(0.0, 0.0, dt, enable_integration, contributions), 0.0);
   for (double error = 100.0; error < 1000.0; error += 100.0) {
-    EXPECT_EQ(pid.calculate(error, dt, enable_integration, contributions), 10.0);
+    EXPECT_EQ(pid.calculate(error, error, dt, enable_integration, contributions), 10.0);
     EXPECT_EQ(contributions[0], 10.0);
     EXPECT_EQ(contributions[1], 10.0);  // integration is activated
     EXPECT_EQ(contributions[2], 10.0);
   }
 
   // Low errors to force each component to its lower limit
-  EXPECT_EQ(pid.calculate(0.0, dt, enable_integration, contributions), 0.0);
+  EXPECT_EQ(pid.calculate(0.0, 0.0, dt, enable_integration, contributions), 0.0);
   for (double error = -100.0; error > -1000.0; error -= 100.0) {
-    EXPECT_EQ(pid.calculate(error, dt, enable_integration, contributions), -10.0);
+    EXPECT_EQ(pid.calculate(error, error, dt, enable_integration, contributions), -10.0);
     EXPECT_EQ(contributions[0], -10.0);
     EXPECT_EQ(contributions[1], -10.0);  // integration is activated
     EXPECT_EQ(contributions[2], -10.0);