transmission_interface::SimpleTransmission Class Reference

Implementation of a simple reducer transmission. More...

#include <simple_transmission.hpp>

Inheritance diagram for transmission_interface::SimpleTransmission:

Collaboration diagram for transmission_interface::SimpleTransmission:

Public Member Functions
	SimpleTransmission (const double joint_to_actuator_reduction, const double joint_offset=0.0)
void	configure (const std::vector< JointHandle > &joint_handles, const std::vector< ActuatorHandle > &actuator_handles) override
	Set up the data the transmission operates on.
void	actuator_to_joint () override
	Transform variables from actuator to joint space.
void	joint_to_actuator () override
	Transform variables from joint to actuator space.
std::size_t	num_actuators () const override
std::size_t	num_joints () const override
double	get_actuator_reduction () const
double	get_joint_offset () const

Protected Attributes
double	reduction_
double	jnt_offset_
JointHandle	joint_position_ = {"", "", nullptr}
JointHandle	joint_velocity_ = {"", "", nullptr}
JointHandle	joint_effort_ = {"", "", nullptr}
ActuatorHandle	actuator_position_ = {"", "", nullptr}
ActuatorHandle	actuator_velocity_ = {"", "", nullptr}
ActuatorHandle	actuator_effort_ = {"", "", nullptr}

Detailed Description

Implementation of a simple reducer transmission.

This transmission relates one actuator and one joint through a reductor (or amplifier). Timing belts and gears are examples of this transmission type, and are illustrated below.

	Effort	Velocity	Position
Actuator to joint	\[ \tau_j = n \tau_a \]	\[ \dot{x}_j = \dot{x}_a / n \]	\[ x_j = x_a / n + x_{off} \]
Joint to actuator	\[ \tau_a = \tau_j / n\]	\[ \dot{x}_a = n \dot{x}_j \]	\[ x_a = n (x_j - x_{off}) \]

where:

• \( x \), \( \dot{x} \) and \( \tau \) are position, velocity and effort variables, respectively.
• Subindices \( _a \) and \( _j \) are used to represent actuator-space and joint-space variables, respectively.
• \( x_{off}\) represents the offset between motor and joint zeros, expressed in joint position coordinates.
• \( n \) is the transmission ratio, and can be computed as the ratio between the output and input pulley radii for the timing belt; or the ratio between output and input teeth for the gear system. The transmission ratio can take any real value except zero. In particular:
  • If its absolute value is greater than one, it's a velocity reducer / effort amplifier, while if its absolute value lies in \( (0, 1) \) it's a velocity amplifier / effort reducer.
  • Negative values represent a direction flip, ie. actuator and joint move in opposite directions. For example, in timing belts actuator and joint move in the same direction, while in single-stage gear systems actuator and joint move in opposite directions.

Constructor & Destructor Documentation

SimpleTransmission()

transmission_interface::SimpleTransmission::SimpleTransmission ( const double  joint_to_actuator_reduction, const double  joint_offset = 0.0  )

inlineexplicit

Parameters

[in]	joint_to_actuator_reduction	Joint to actuator reduction ratio.
[in]	joint_offset	Joint position offset used in the position mappings.

Precondition

Nonzero reduction value.

Member Function Documentation

actuator_to_joint()

void transmission_interface::SimpleTransmission::actuator_to_joint ( )

inlineoverridevirtual

Transform variables from actuator to joint space.

This method operates on the handles provided when configuring the transmission. To call this method it is not required that all supported interface types are provided, e.g. one can supply only velocity handles

Implements transmission_interface::Transmission.

configure()

void transmission_interface::SimpleTransmission::configure ( const std::vector< JointHandle > &  joint_handles, const std::vector< ActuatorHandle > &  actuator_handles  )

inlineoverridevirtual

Set up the data the transmission operates on.

Parameters

[in]	joint_handles	Vector of interface handles of one joint
[in]	actuator_handles	Vector of interface handles of one actuator

Precondition

Vectors are nonzero.

Joint handles share the same joint name and actuator handles share the same actuator name.

Implements transmission_interface::Transmission.

joint_to_actuator()

void transmission_interface::SimpleTransmission::joint_to_actuator ( )

inlineoverridevirtual

Transform variables from joint to actuator space.

This method operates on the handles provided when configuring the transmission. To call this method it is not required that all supported interface types are provided, e.g. one can supply only velocity handles

Implements transmission_interface::Transmission.

num_actuators()

std::size_t transmission_interface::SimpleTransmission::num_actuators ( ) const

inlineoverridevirtual

Returns

Number of actuators managed by transmission, ie. the dimension of the actuator space.

Implements transmission_interface::Transmission.

num_joints()

std::size_t transmission_interface::SimpleTransmission::num_joints ( ) const

inlineoverridevirtual

Returns

Number of joints managed by transmission, ie. the dimension of the joint space.

Implements transmission_interface::Transmission.

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The documentation for this class was generated from the following file:

• ros2_control/transmission_interface/include/transmission_interface/simple_transmission.hpp