pid_tests.cpp

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#include <ros/ros.h>

#include <gtest/gtest.h>

#include <control_toolbox/pid.h>

#include <boost/math/special_functions/fpclassify.hpp>

using namespace control_toolbox;

TEST(ParameterTest, ITermBadIBoundsTest)
{
  RecordProperty("description","This test checks that the integral contribution is robust to bad i_bounds specification (i.e. i_min > i_max).");

  // Check that the output is not a non-sense if i-bounds are bad, i.e. i_min > i_max
  Pid pid(1.0, 1.0, 1.0, -1.0, 1.0);
  double cmd = 0.0;
  double pe,ie,de;

  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  pid.getCurrentPIDErrors(&pe,&ie,&de);
  EXPECT_FALSE(boost::math::isinf(ie));
  EXPECT_FALSE(boost::math::isnan(cmd));

  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  pid.getCurrentPIDErrors(&pe,&ie,&de);
  EXPECT_FALSE(boost::math::isinf(ie));
  EXPECT_FALSE(boost::math::isnan(cmd));
}

TEST(ParameterTest, integrationWindupTest)
{
  RecordProperty("description","This test succeeds if the integral contribution is prevented from winding up when the integral gain is non-zero.");

  Pid pid(0.0, 1.0, 0.0, 1.0, -1.0);

  double cmd = 0.0;

  // Test lower limit
  cmd = pid.computeCommand(-10.03, ros::Duration(1.0));
  EXPECT_EQ(-1.0, cmd);

  // Test upper limit
  cmd = pid.computeCommand(30.0, ros::Duration(1.0));
  EXPECT_EQ(1.0, cmd);
}

TEST(ParameterTest, integrationWindupZeroGainTest)
{
  RecordProperty("description","This test succeeds if the integral contribution is prevented from winding up when the integral gain is zero. If the integral contribution is allowed to wind up while it is disabled, it can cause sudden jumps to the minimum or maximum bound in control command when re-enabled.");

  double i_gain = 0.0;
  double i_min = -1.0;
  double i_max = 1.0;
  Pid pid(0.0, i_gain, 0.0, i_max, i_min);

  double cmd = 0.0;
  double pe,ie,de;

  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  pid.getCurrentPIDErrors(&pe,&ie,&de);
  EXPECT_LE(i_min, cmd);
  EXPECT_LE(cmd, i_max);
  EXPECT_EQ(0.0, cmd);

  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  EXPECT_LE(i_min, cmd);
  EXPECT_LE(cmd, i_max);
  EXPECT_EQ(0.0, cmd);
}

TEST(ParameterTest, gainSettingCopyPIDTest)
{
  RecordProperty("description","This test succeeds if a PID object has its gain set at different points in time then the values are get-ed and still remain the same, as well as when PID is copied.");

  // Test values
  double p_gain = rand() % 100;
  double i_gain = rand() % 100;
  double d_gain = rand() % 100;
  double i_max = rand() % 100;
  double i_min = -1 * rand() % 100;

  // Initialize the default way
  Pid pid1(p_gain, i_gain, d_gain, i_max, i_min);
  
  // Test return values  -------------------------------------------------
  double p_gain_return, i_gain_return, d_gain_return, i_max_return, i_min_return;
  pid1.getGains(p_gain_return, i_gain_return, d_gain_return, i_max_return, i_min_return);

  EXPECT_EQ(p_gain, p_gain_return);
  EXPECT_EQ(i_gain, i_gain_return);
  EXPECT_EQ(d_gain, d_gain_return);
  EXPECT_EQ(i_max, i_max_return);
  EXPECT_EQ(i_min, i_min_return);

  // Test return values using struct -------------------------------------------------

  // New values
  p_gain = rand() % 100;
  i_gain = rand() % 100;
  d_gain = rand() % 100;
  i_max = rand() % 100;
  i_min = -1 * rand() % 100;
  pid1.setGains(p_gain, i_gain, d_gain, i_max, i_min);

  Pid::Gains g1 = pid1.getGains();
  EXPECT_EQ(p_gain, g1.p_gain_);
  EXPECT_EQ(i_gain, g1.i_gain_);
  EXPECT_EQ(d_gain, g1.d_gain_);
  EXPECT_EQ(i_max, g1.i_max_);
  EXPECT_EQ(i_min, g1.i_min_);

  // \todo test initParam() -------------------------------------------------
  

  // \todo test bool init(const ros::NodeHandle &n); -----------------------------------


  // Send update command to populate errors -------------------------------------------------
  pid1.setCurrentCmd(10);
  pid1.computeCommand(20, ros::Duration(1.0));

  // Test copy constructor -------------------------------------------------
  Pid pid2(pid1);

  pid2.getGains(p_gain_return, i_gain_return, d_gain_return, i_max_return, i_min_return);

  EXPECT_EQ(p_gain, p_gain_return);
  EXPECT_EQ(i_gain, i_gain_return);
  EXPECT_EQ(d_gain, d_gain_return);
  EXPECT_EQ(i_max, i_max_return);
  EXPECT_EQ(i_min, i_min_return);

  // Test that errors are zero
  double pe2, ie2, de2;
  pid2.getCurrentPIDErrors(&pe2, &ie2, &de2);
  EXPECT_EQ(0.0, pe2);
  EXPECT_EQ(0.0, ie2);
  EXPECT_EQ(0.0, de2);
    
  // Test assignment constructor -------------------------------------------------
  Pid pid3;
  pid3 = pid1;

  pid3.getGains(p_gain_return, i_gain_return, d_gain_return, i_max_return, i_min_return);

  EXPECT_EQ(p_gain, p_gain_return);
  EXPECT_EQ(i_gain, i_gain_return);
  EXPECT_EQ(d_gain, d_gain_return);
  EXPECT_EQ(i_max, i_max_return);
  EXPECT_EQ(i_min, i_min_return);

  // Test that errors are zero
  double pe3, ie3, de3;
  pid3.getCurrentPIDErrors(&pe3, &ie3, &de3);
  EXPECT_EQ(0.0, pe3);
  EXPECT_EQ(0.0, ie3);
  EXPECT_EQ(0.0, de3);

  // Test the reset() function, it should clear errors and command
  pid1.reset();

  double pe1, ie1, de1;
  pid1.getCurrentPIDErrors(&pe1, &ie1, &de1);
  EXPECT_EQ(0.0, pe1);
  EXPECT_EQ(0.0, ie1);
  EXPECT_EQ(0.0, de1);

  double cmd1 = pid1.getCurrentCmd();
  EXPECT_EQ(0.0, cmd1);
}

TEST(CommandTest, proportionalOnlyTest)
{
  RecordProperty("description","This test checks that a command is computed correctly using the proportional contribution only.");

  // Set only proportional gain
  Pid pid(1.0, 0.0, 0.0, 0.0, 0.0);
  double cmd = 0.0;

  // If initial error = 0, p-gain = 1, dt = 1
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect command = error
  EXPECT_EQ(-0.5, cmd);

  // If call again
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect the same as before
  EXPECT_EQ(-0.5, cmd);

  // If call again doubling the error
  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  // Then expect the command doubled
  EXPECT_EQ(-1.0, cmd);

  // If call with positive error
  cmd = pid.computeCommand(0.5, ros::Duration(1.0));
  // Then expect always command = error
  EXPECT_EQ(0.5, cmd);
}

TEST(CommandTest, integralOnlyTest)
{
  RecordProperty("description","This test checks that a command is computed correctly using the integral contribution only (ATTENTION: this test depends on the integration scheme).");

  // Set only integral gains with enough limits to test behavior
  Pid pid(0.0, 1.0, 0.0, 5.0, -5.0);
  double cmd = 0.0;

  // If initial error = 0, i-gain = 1, dt = 1
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect command = error
  EXPECT_EQ(-0.5, cmd);

  // If call again with same arguments
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect the integral part to double the command
  EXPECT_EQ(-1.0, cmd);

  // Call again with no error
  cmd = pid.computeCommand(0.0, ros::Duration(1.0));
  // Expect the integral part to keep the previous command because it ensures error = 0
  EXPECT_EQ(-1.0, cmd);

  // Double check that the integral contribution keep the previous command
  cmd = pid.computeCommand(0.0, ros::Duration(1.0));
  EXPECT_EQ(-1.0, cmd);

  // Finally call again with positive error to see if the command changes in the opposite direction
  cmd = pid.computeCommand(1.0, ros::Duration(1.0));
  // Expect that the command is cleared since error = -1 * previous command, i-gain = 1, dt = 1
  EXPECT_EQ(0.0, cmd);
}

TEST(CommandTest, derivativeOnlyTest)
{
  RecordProperty("description","This test checks that a command is computed correctly using the derivative contribution only with own differentiation (ATTENTION: this test depends on the differentiation scheme).");

  // Set only derivative gain
  Pid pid(0.0, 0.0, 1.0, 0.0, 0.0);
  double cmd = 0.0;

  // If initial error = 0, d-gain = 1, dt = 1
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect command = error
  EXPECT_EQ(-0.5, cmd);

  // If call again with same error
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect command = 0 due to no variation on error
  EXPECT_EQ(0.0, cmd);

  // If call again with same error and smaller control period
  cmd = pid.computeCommand(-0.5, ros::Duration(0.1));
  // Then expect command = 0 again
  EXPECT_EQ(0.0, cmd);

  // If the error increases,  with dt = 1
  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  // Then expect the command = change in dt
  EXPECT_EQ(-0.5, cmd);

  // If error decreases, with dt = 1
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect always the command = change in dt (note the sign flip)
  EXPECT_EQ(0.5, cmd);
}

TEST(CommandTest, completePIDTest)
{
  RecordProperty("description","This test checks that  a command is computed correctly using a complete PID controller (ATTENTION: this test depends on the integral and differentiation schemes).");

  Pid pid(1.0, 1.0, 1.0, 5.0, -5.0);
  double cmd = 0.0;

  // All contributions are tested, here few tests check that they sum up correctly
  // If initial error = 0, all gains = 1, dt = 1
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect command = 3x error
  EXPECT_EQ(-1.5, cmd);

  // If call again with same arguments, no error change, but integration do its part
  cmd = pid.computeCommand(-0.5, ros::Duration(1.0));
  // Then expect command = 3x error again
  EXPECT_EQ(-1.5, cmd);

  // If call again increasing the error
  cmd = pid.computeCommand(-1.0, ros::Duration(1.0));
  // Then expect command equals to p = -1, i = -2.0 (i.e. - 0.5 - 0.5 - 1.0), d = -0.5
  EXPECT_EQ(-3.5, cmd);
}

int main(int argc, char** argv) {
  testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}