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Fix steering controllers library kinematics #1150

Merged
merged 12 commits into from
Jul 3, 2024
Merged

Fix steering controllers library kinematics #1150

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aa34f02
Fix IK
christophfroehlich May 28, 2024
35f34d8
Fix controller tests and add notes
christophfroehlich May 28, 2024
21afbc5
Improve tests for other steering types
christophfroehlich May 28, 2024
8809f62
Improve odometry of overdetermined measurements
christophfroehlich May 28, 2024
0209540
Remove debug output
christophfroehlich May 28, 2024
f7486dd
Use std:: namespace for trigonometric functions
christophfroehlich Jun 8, 2024
8729f9e
Use the full name
christophfroehlich Jun 19, 2024
5eba4e4
Merge commit 'b81be48fb1b6101a3c601c0ea11c5393e5a7026e' into fix/stee…
christophfroehlich Jun 19, 2024
37b8f0a
Fix method name
christophfroehlich Jun 19, 2024
1504bc5
Add helper function
christophfroehlich Jun 19, 2024
fe2ba4b
Add default value to avoid breaking API
christophfroehlich Jun 20, 2024
3fa39cc
Merge branch 'master' into fix/steering_controllers_library_kinematics
destogl Jul 3, 2024
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6 changes: 5 additions & 1 deletion ackermann_steering_controller/test/test_ackermann_steering_controller.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -173,6 +173,7 @@ TEST_F(AckermannSteeringControllerTest, test_update_logic)
controller_->update(rclcpp::Time(0, 0, RCL_ROS_TIME), rclcpp::Duration::from_seconds(0.01)),
controller_interface::return_type::OK);

// we test with open_loop=false, but steering angle was not updated (is zero) -> same commands
EXPECT_NEAR(
controller_->command_interfaces_[CMD_TRACTION_RIGHT_WHEEL].get_value(), 0.22222222222222224,
COMMON_THRESHOLD);
Expand Down Expand Up @@ -211,8 +212,9 @@ TEST_F(AckermannSteeringControllerTest, test_update_logic_chained)
ASSERT_EQ(
controller_->update(rclcpp::Time(0, 0, RCL_ROS_TIME), rclcpp::Duration::from_seconds(0.01)),
controller_interface::return_type::OK);
EXPECT_NEAR(

// we test with open_loop=false, but steering angle was not updated (is zero) -> same commands
EXPECT_NEAR(
controller_->command_interfaces_[STATE_TRACTION_RIGHT_WHEEL].get_value(), 0.22222222222222224,
COMMON_THRESHOLD);
EXPECT_NEAR(
Expand Down Expand Up @@ -261,6 +263,7 @@ TEST_F(AckermannSteeringControllerTest, receive_message_and_publish_updated_stat
controller_->update(rclcpp::Time(0, 0, RCL_ROS_TIME), rclcpp::Duration::from_seconds(0.01)),
controller_interface::return_type::OK);

// we test with open_loop=false, but steering angle was not updated (is zero) -> same commands
EXPECT_NEAR(
controller_->command_interfaces_[CMD_TRACTION_RIGHT_WHEEL].get_value(), 0.22222222222222224,
COMMON_THRESHOLD);
Expand All @@ -276,6 +279,7 @@ TEST_F(AckermannSteeringControllerTest, receive_message_and_publish_updated_stat

subscribe_and_get_messages(msg);

// we test with open_loop=false, but steering angle was not updated (is zero) -> same commands
EXPECT_NEAR(
msg.linear_velocity_command[CMD_TRACTION_RIGHT_WHEEL], 0.22222222222222224, COMMON_THRESHOLD);
EXPECT_NEAR(
Expand Down
10 changes: 5 additions & 5 deletions bicycle_steering_controller/test/test_bicycle_steering_controller.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -158,7 +158,7 @@ TEST_F(BicycleSteeringControllerTest, test_update_logic)
controller_interface::return_type::OK);

EXPECT_NEAR(
controller_->command_interfaces_[CMD_TRACTION_WHEEL].get_value(), 0.253221, COMMON_THRESHOLD);
controller_->command_interfaces_[CMD_TRACTION_WHEEL].get_value(), 0.1 / 0.45, COMMON_THRESHOLD);
EXPECT_NEAR(
controller_->command_interfaces_[CMD_STEER_WHEEL].get_value(), 1.4179821977774734,
COMMON_THRESHOLD);
Expand Down Expand Up @@ -190,7 +190,7 @@ TEST_F(BicycleSteeringControllerTest, test_update_logic_chained)
controller_interface::return_type::OK);

EXPECT_NEAR(
controller_->command_interfaces_[CMD_TRACTION_WHEEL].get_value(), 0.253221, COMMON_THRESHOLD);
controller_->command_interfaces_[CMD_TRACTION_WHEEL].get_value(), 0.1 / 0.45, COMMON_THRESHOLD);
EXPECT_NEAR(
controller_->command_interfaces_[CMD_STEER_WHEEL].get_value(), 1.4179821977774734,
COMMON_THRESHOLD);
Expand Down Expand Up @@ -237,22 +237,22 @@ TEST_F(BicycleSteeringControllerTest, receive_message_and_publish_updated_status
EXPECT_EQ(msg.linear_velocity_command[0], 1.1);
EXPECT_EQ(msg.steering_angle_command[0], 2.2);

publish_commands();
publish_commands(0.1, 0.2);
ASSERT_TRUE(controller_->wait_for_commands(executor));

ASSERT_EQ(
controller_->update(rclcpp::Time(0, 0, RCL_ROS_TIME), rclcpp::Duration::from_seconds(0.01)),
controller_interface::return_type::OK);

EXPECT_NEAR(
controller_->command_interfaces_[CMD_TRACTION_WHEEL].get_value(), 0.253221, COMMON_THRESHOLD);
controller_->command_interfaces_[CMD_TRACTION_WHEEL].get_value(), 0.1 / 0.45, COMMON_THRESHOLD);
EXPECT_NEAR(
controller_->command_interfaces_[CMD_STEER_WHEEL].get_value(), 1.4179821977774734,
COMMON_THRESHOLD);

subscribe_and_get_messages(msg);

EXPECT_NEAR(msg.linear_velocity_command[0], 0.253221, COMMON_THRESHOLD);
EXPECT_NEAR(msg.linear_velocity_command[0], 0.1 / 0.45, COMMON_THRESHOLD);
EXPECT_NEAR(msg.steering_angle_command[0], 1.4179821977774734, COMMON_THRESHOLD);
}

Expand Down
17 changes: 16 additions & 1 deletion steering_controllers_library/include/steering_controllers_library/steering_odometry.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
#ifndef STEERING_CONTROLLERS_LIBRARY__STEERING_ODOMETRY_HPP_
#define STEERING_CONTROLLERS_LIBRARY__STEERING_ODOMETRY_HPP_

#include <cmath>
#include <tuple>
#include <vector>

Expand All @@ -36,6 +37,9 @@ namespace steering_odometry
const unsigned int BICYCLE_CONFIG = 0;
const unsigned int TRICYCLE_CONFIG = 1;
const unsigned int ACKERMANN_CONFIG = 2;

inline bool is_close_to_zero(double val) { return std::fabs(val) < 1e-6; }

/**
* \brief The Odometry class handles odometry readings
* (2D pose and velocity with related timestamp)
Expand Down Expand Up @@ -188,10 +192,11 @@ class SteeringOdometry
* \brief Calculates inverse kinematics for the desired linear and angular velocities
* \param v_bx Desired linear velocity of the robot in x_b-axis direction
* \param omega_bz Desired angular velocity of the robot around x_z-axis
* \param open_loop If false, the IK will be calculated using measured steering angle
* \return Tuple of velocity commands and steering commands
*/
std::tuple<std::vector<double>, std::vector<double>> get_commands(
const double v_bx, const double omega_bz);
const double v_bx, const double omega_bz, const bool open_loop);

/**
* \brief Reset poses, heading, and accumulators
Expand Down Expand Up @@ -230,6 +235,16 @@ class SteeringOdometry
*/
double convert_twist_to_steering_angle(const double v_bx, const double omega_bz);

/**
* \brief Calculates linear velocity of a robot with double traction axle
* \param right_traction_wheel_vel Right traction wheel velocity [rad/s]
* \param left_traction_wheel_vel Left traction wheel velocity [rad/s]
* \param steer_pos Steer wheel position [rad]
*/
double get_linear_velocity_double_traction_axle(
const double right_traction_wheel_vel, const double left_traction_wheel_vel,
const double steer_pos);

/**
* \brief Reset linear and angular accumulators
*/
Expand Down
2 changes: 1 addition & 1 deletion steering_controllers_library/src/steering_controllers_library.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -401,7 +401,7 @@ controller_interface::return_type SteeringControllersLibrary::update_and_write_c
last_angular_velocity_ = reference_interfaces_[1];

auto [traction_commands, steering_commands] =
odometry_.get_commands(last_linear_velocity_, last_angular_velocity_);
odometry_.get_commands(last_linear_velocity_, last_angular_velocity_, params_.open_loop);
if (params_.front_steering)
{
for (size_t i = 0; i < params_.rear_wheels_names.size(); i++)
Expand Down
82 changes: 60 additions & 22 deletions steering_controllers_library/src/steering_odometry.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@

#include <cmath>
#include <iostream>
#include <limits>

namespace steering_odometry
{
Expand Down Expand Up @@ -128,13 +129,26 @@ bool SteeringOdometry::update_from_velocity(
return update_odometry(linear_velocity, angular_velocity, dt);
}

double SteeringOdometry::get_linear_velocity_double_traction_axle(
const double right_traction_wheel_vel, const double left_traction_wheel_vel,
const double steer_pos)
{
double turning_radius = wheelbase_ / std::tan(steer_pos);
// overdetermined, we take the average
double vel_r = right_traction_wheel_vel * wheel_radius_ * turning_radius /
(turning_radius + wheel_track_ * 0.5);
double vel_l = left_traction_wheel_vel * wheel_radius_ * turning_radius /
(turning_radius - wheel_track_ * 0.5);
return (vel_r + vel_l) * 0.5;
}

bool SteeringOdometry::update_from_velocity(
const double right_traction_wheel_vel, const double left_traction_wheel_vel,
const double steer_pos, const double dt)
{
double linear_velocity =
(right_traction_wheel_vel + left_traction_wheel_vel) * wheel_radius_ * 0.5;
steer_pos_ = steer_pos;
double linear_velocity = get_linear_velocity_double_traction_axle(
right_traction_wheel_vel, left_traction_wheel_vel, steer_pos_);

const double angular_velocity = std::tan(steer_pos_) * linear_velocity / wheelbase_;

Expand All @@ -145,10 +159,18 @@ bool SteeringOdometry::update_from_velocity(
const double right_traction_wheel_vel, const double left_traction_wheel_vel,
const double right_steer_pos, const double left_steer_pos, const double dt)
{
steer_pos_ = (right_steer_pos + left_steer_pos) * 0.5;
double linear_velocity =
(right_traction_wheel_vel + left_traction_wheel_vel) * wheel_radius_ * 0.5;
const double angular_velocity = std::tan(steer_pos_) * linear_velocity / wheelbase_;
// overdetermined, we take the average
const double right_steer_pos_est = std::atan(
wheelbase_ * std::tan(right_steer_pos) /
(wheelbase_ - wheel_track_ / 2 * std::tan(right_steer_pos)));
const double left_steer_pos_est = std::atan(
wheelbase_ * std::tan(left_steer_pos) /
(wheelbase_ + wheel_track_ / 2 * std::tan(left_steer_pos)));
steer_pos_ = (right_steer_pos_est + left_steer_pos_est) * 0.5;
Comment on lines +162 to +169
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Calculations are fine, but I thin we can split it a little to re-use and improve readability having "atan" and "tan" at the same line is a little confusing.

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Nah that's fine since this is following the docs.


double linear_velocity = get_linear_velocity_double_traction_axle(
right_traction_wheel_vel, left_traction_wheel_vel, steer_pos_);
const double angular_velocity = steer_pos_ * linear_velocity / wheelbase_;

return update_odometry(linear_velocity, angular_velocity, dt);
}
Expand Down Expand Up @@ -181,30 +203,41 @@ void SteeringOdometry::set_odometry_type(const unsigned int type) { config_type_

double SteeringOdometry::convert_twist_to_steering_angle(double v_bx, double omega_bz)
{
if (omega_bz == 0 || v_bx == 0)
if (fabs(v_bx) < std::numeric_limits<float>::epsilon())
{
return 0;
// avoid division by zero
return 0.;
}
return std::atan(omega_bz * wheelbase_ / v_bx);
}

std::tuple<std::vector<double>, std::vector<double>> SteeringOdometry::get_commands(
const double v_bx, const double omega_bz)
const double v_bx, const double omega_bz, const bool open_loop)
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{
// desired wheel speed and steering angle of the middle of traction and steering axis
double Ws, phi;
double Ws, phi, phi_IK = steer_pos_;

#if 0
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if (v_bx == 0 && omega_bz != 0)
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{
// TODO(anyone) would be only valid if traction is on the steering axis -> tricycle_controller
// TODO(anyone) this would be only possible if traction is on the steering axis
phi = omega_bz > 0 ? M_PI_2 : -M_PI_2;
Ws = abs(omega_bz) * wheelbase_ / wheel_radius_;
}
else
{
phi = SteeringOdometry::convert_twist_to_steering_angle(v_bx, omega_bz);
Ws = v_bx / (wheel_radius_ * std::cos(steer_pos_));
// TODO(anyone) this would be valid only if traction is on the steering axis
Ws = v_bx / (wheel_radius_ * std::cos(phi_IK)); // using the measured steering angle
}
#endif
// steering angle
phi = SteeringOdometry::convert_twist_to_steering_angle(v_bx, omega_bz);
if (open_loop)
{
phi_IK = phi;
}
// wheel speed
Ws = v_bx / wheel_radius_;

if (config_type_ == BICYCLE_CONFIG)
{
Expand All @@ -216,32 +249,37 @@ std::tuple<std::vector<double>, std::vector<double>> SteeringOdometry::get_comma
{
std::vector<double> traction_commands;
std::vector<double> steering_commands;
if (fabs(steer_pos_) < 1e-6)
// double-traction axle
if (is_close_to_zero(phi_IK))
{
// avoid division by zero
traction_commands = {Ws, Ws};
}
else
{
const double turning_radius = wheelbase_ / std::tan(steer_pos_);
const double turning_radius = wheelbase_ / std::tan(phi_IK);
const double Wr = Ws * (turning_radius + wheel_track_ * 0.5) / turning_radius;
const double Wl = Ws * (turning_radius - wheel_track_ * 0.5) / turning_radius;
traction_commands = {Wr, Wl};
}
// simple steering
steering_commands = {phi};
return std::make_tuple(traction_commands, steering_commands);
}
else if (config_type_ == ACKERMANN_CONFIG)
{
std::vector<double> traction_commands;
std::vector<double> steering_commands;
if (fabs(steer_pos_) < 1e-6)
if (is_close_to_zero(phi_IK))
{
// avoid division by zero
traction_commands = {Ws, Ws};
// shortcut, no steering
steering_commands = {phi, phi};
}
else
{
const double turning_radius = wheelbase_ / std::tan(steer_pos_);
const double turning_radius = wheelbase_ / std::tan(phi_IK);
const double Wr = Ws * (turning_radius + wheel_track_ * 0.5) / turning_radius;
const double Wl = Ws * (turning_radius - wheel_track_ * 0.5) / turning_radius;
traction_commands = {Wr, Wl};
Expand Down Expand Up @@ -279,8 +317,8 @@ void SteeringOdometry::integrate_runge_kutta_2(
const double theta_mid = heading_ + omega_bz * 0.5 * dt;

// Use the intermediate values to update the state
x_ += v_bx * cos(theta_mid) * dt;
y_ += v_bx * sin(theta_mid) * dt;
x_ += v_bx * std::cos(theta_mid) * dt;
y_ += v_bx * std::sin(theta_mid) * dt;
heading_ += omega_bz * dt;
}

Expand All @@ -289,7 +327,7 @@ void SteeringOdometry::integrate_fk(const double v_bx, const double omega_bz, co
const double delta_x_b = v_bx * dt;
const double delta_theta = omega_bz * dt;

if (fabs(delta_theta) < 1e-6)
if (is_close_to_zero(delta_theta))
{
/// Runge-Kutta 2nd Order (should solve problems when omega_bz is zero):
integrate_runge_kutta_2(v_bx, omega_bz, dt);
Expand All @@ -300,8 +338,8 @@ void SteeringOdometry::integrate_fk(const double v_bx, const double omega_bz, co
const double heading_old = heading_;
const double R = delta_x_b / delta_theta;
heading_ += delta_theta;
x_ += R * (sin(heading_) - sin(heading_old));
y_ += -R * (cos(heading_) - cos(heading_old));
x_ += R * (sin(heading_) - std::sin(heading_old));
y_ += -R * (cos(heading_) - std::cos(heading_old));
}
}

Expand Down
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