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vehicle_constants_manager#

This is the design document for the vehicle_constants_manager package.

Purpose / Use cases#

This library provides a struct for holding vehicle specific constants. It also provides a helper method to declare vehicle specific constants which have already been passed into a node and provide a VehicleConstants object.

Design#

Provided VehicleConstants struct holds vehicle parameters. Its parameters can be split in 2 categories: (The detailed descriptions and units of the variables is in the vehicle_constants_manager.hpp file.)

  • Primary Constants - wheel_radius - wheel_width - wheel_base - wheel_tread - overhang_front - overhang_rear - overhang_left - overhang_right - vehicle_height - cg_to_rear - tire_cornering_stiffness_front_n_per_deg - tire_cornering_stiffness_rear_n_per_deg - mass_vehicle - inertia_yaw_kg_m_2
  • Derived Constants - cg_to_front - vehicle_length - vehicle_width - offset_longitudinal_min - offset_longitudinal_max - offset_lateral_min - offset_lateral_max - offset_height_min - offset_height_max

The VehicleConstants constructor is initialized with the primary parameters.

The library also provides a declare_and_get_vehicle_constants method. Using this method, the user can declare vehicle parameters that are already passed into the node and obtain a VehicleConstants object.

Assumptions / Known limits#

This library assumes the vehicle is defined with Ackermann steering geometry.

declare_and_get_vehicle_constants method requires the passed node to have following parameters overridden:

(Pay attention to the vehicle namespace) 

vehicle:
  wheel_radius:
  wheel_width:
  wheel_base:
  wheel_tread:
  overhang_front:
  overhang_rear:
  overhang_left:
  overhang_right:
  vehicle_height:
  cg_to_rear:
  tire_cornering_stiffness_front_n_per_deg:
  tire_cornering_stiffness_rear_n_per_deg:
  mass_vehicle:
  inertia_yaw_kg_m_2:

Inputs / Outputs / API#

The constructor of VehicleConstants takes the primary vehicle constants and generates the derived parameters.

declare_and_get_vehicle_constants method takes a rclcpp::Node object. And returns a VehicleConstants object if it succeeds.

Example usage: 

// In the constructor of a node which received primary vehicle parameters from a
// .yaml file or run args.
auto vehicle_constants = declare_and_get_vehicle_constants(*this);

Inner-workings / Algorithms#

Not Available.

Error detection and handling#

The VehicleConstants struct performs some sanity checks upon construction.

It will throw std::runtime_error in case certain parameters are negative or cg_to_rear is larger than wheel_base (to ensure center of gravity is within front and rear axles.)

Security considerations#

To Be Determined.

References / External links#

Not Available.

Future extensions / Unimplemented parts#

Not Available.

Related issues#

https://gitlab.com/autowarefoundation/autoware.auto/AutowareAuto/-/issues/1294

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