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[DiffDriveController] Add velocity limits for individual wheels #471

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[DiffDriveController] Add velocity limits for individual wheels #471

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6 changes: 6 additions & 0 deletions diff_drive_controller/include/diff_drive_controller/diff_drive_controller.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,12 @@ class DiffDriveController : public controller_interface::ControllerInterface
double separation_multiplier = 1.0;
double left_radius_multiplier = 1.0;
double right_radius_multiplier = 1.0;
bool left_wheel_has_velocity_limits = false;
bool right_wheel_has_velocity_limits = false;
double left_wheel_max_velocity = NAN;
double right_wheel_max_velocity = NAN;
double left_wheel_min_velocity = NAN;
double right_wheel_min_velocity = NAN;
} wheel_params_;

struct OdometryParams
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64 changes: 62 additions & 2 deletions diff_drive_controller/src/diff_drive_controller.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,14 @@ controller_interface::CallbackReturn DiffDriveController::on_init()
auto_declare<double>("wheel_separation_multiplier", wheel_params_.separation_multiplier);
auto_declare<double>("left_wheel_radius_multiplier", wheel_params_.left_radius_multiplier);
auto_declare<double>("right_wheel_radius_multiplier", wheel_params_.right_radius_multiplier);
auto_declare<bool>(
"left_wheel.has_velocity_limits", wheel_params_.left_wheel_has_velocity_limits);
auto_declare<bool>(
"right_wheel.has_velocity_limits", wheel_params_.right_wheel_has_velocity_limits);
auto_declare<double>("left_wheel.max_velocity", wheel_params_.left_wheel_max_velocity);
auto_declare<double>("right_wheel.max_velocity", wheel_params_.right_wheel_max_velocity);
auto_declare<double>("left_wheel.min_velocity", wheel_params_.left_wheel_min_velocity);
auto_declare<double>("right_wheel.min_velocity", wheel_params_.right_wheel_min_velocity);

auto_declare<std::string>("odom_frame_id", odom_params_.odom_frame_id);
auto_declare<std::string>("base_frame_id", odom_params_.base_frame_id);
Expand Down Expand Up @@ -280,11 +288,51 @@ controller_interface::return_type DiffDriveController::update(
}

// Compute wheels velocities:
const double velocity_left =
double velocity_left =
(linear_command - angular_command * wheel_separation / 2.0) / left_wheel_radius;
const double velocity_right =
double velocity_right =
(linear_command + angular_command * wheel_separation / 2.0) / right_wheel_radius;

// Limit individual wheel velocity to keep heading:
if (wheels.left_wheel_has_velocity_limits)
{
if (velocity_left > wheels.left_wheel_max_velocity && velocity_left != 0)
{
const double reduction_ratio = wheels.left_wheel_max_velocity / velocity_left;
velocity_left *= reduction_ratio;
velocity_right *= reduction_ratio;
}
else if (velocity_left < wheels.left_wheel_min_velocity && velocity_right != 0)
{
// If velocity and limit is on the same side of the sign we won't be able to keep heading
if (copysign(1.0, velocity_left) == copysign(1.0, wheels.left_wheel_min_velocity))
{
const double ratio = wheels.left_wheel_min_velocity / velocity_left;
velocity_left *= ratio;
velocity_right *= ratio;
}
}
}
if (wheels.right_wheel_has_velocity_limits)
{
if (velocity_right > wheels.right_wheel_max_velocity)
{
const double reduction_ratio = wheels.right_wheel_max_velocity / velocity_right;
velocity_left *= reduction_ratio;
velocity_right *= reduction_ratio;
}
else if (velocity_right < wheels.right_wheel_min_velocity)
{
// If velocity and limit is on the same side of the sign we wont be able to keep heading
if (copysign(1.0, velocity_right) == copysign(1.0, wheels.right_wheel_min_velocity))
{
const double ratio = wheels.right_wheel_min_velocity / velocity_right;
velocity_left *= ratio;
velocity_right *= ratio;
}
}
}

// Set wheels velocities:
for (size_t index = 0; index < wheels.wheels_per_side; ++index)
{
Expand Down Expand Up @@ -328,6 +376,18 @@ controller_interface::CallbackReturn DiffDriveController::on_configure(
get_node()->get_parameter("left_wheel_radius_multiplier").as_double();
wheel_params_.right_radius_multiplier =
get_node()->get_parameter("right_wheel_radius_multiplier").as_double();
wheel_params_.left_wheel_has_velocity_limits =
node_->get_parameter("left_wheel.has_velocity_limits").as_bool();
wheel_params_.right_wheel_has_velocity_limits =
node_->get_parameter("right_wheel.has_velocity_limits").as_bool();
wheel_params_.left_wheel_max_velocity =
node_->get_parameter("left_wheel.max_velocity").as_double();
wheel_params_.right_wheel_max_velocity =
node_->get_parameter("right_wheel.max_velocity").as_double();
wheel_params_.left_wheel_min_velocity =
node_->get_parameter("left_wheel.min_velocity").as_double();
wheel_params_.right_wheel_min_velocity =
node_->get_parameter("right_wheel.min_velocity").as_double();

const auto wheels = wheel_params_;

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