Implementation of a four-bar-linkage transmission. More...

#include <four_bar_linkage_transmission.h>

Inheritance diagram for transmission_interface::FourBarLinkageTransmission:

Public Member Functions
void	actuatorToJointAbsolutePosition (const ActuatorData &act_data, JointData &jnt_data) override
	Transform absolute encoder values from actuator to joint space. More...

void	actuatorToJointEffort (const ActuatorData &act_data, JointData &jnt_data) override
	Transform effort variables from actuator to joint space. More...

void	actuatorToJointPosition (const ActuatorData &act_data, JointData &jnt_data) override
	Transform position variables from actuator to joint space. More...

void	actuatorToJointTorqueSensor (const ActuatorData &act_data, JointData &jnt_data) override
	Transform torque sensor values from actuator to joint space. More...

void	actuatorToJointVelocity (const ActuatorData &act_data, JointData &jnt_data) override
	Transform velocity variables from actuator to joint space. More...

	FourBarLinkageTransmission (const std::vector< double > &actuator_reduction, const std::vector< double > &joint_reduction, const std::vector< double > &joint_offset=std::vector< double >(2, 0.0))

const std::vector< double > &	getActuatorReduction () const

const std::vector< double > &	getJointOffset () const

const std::vector< double > &	getJointReduction () const

bool	hasActuatorToJointAbsolutePosition () const override

bool	hasActuatorToJointTorqueSensor () const override

void	jointToActuatorEffort (const JointData &jnt_data, ActuatorData &act_data) override
	Transform effort variables from joint to actuator space. More...

void	jointToActuatorPosition (const JointData &jnt_data, ActuatorData &act_data) override
	Transform position variables from joint to actuator space. More...

void	jointToActuatorVelocity (const JointData &jnt_data, ActuatorData &act_data) override
	Transform velocity variables from joint to actuator space. More...

std::size_t	numActuators () const override

std::size_t	numJoints () const override

Public Member Functions inherited from transmission_interface::Transmission
virtual	~Transmission ()=default

Protected Attributes
std::vector< double >	act_reduction_

std::vector< double >	jnt_offset_

std::vector< double >	jnt_reduction_

Detailed Description

Implementation of a four-bar-linkage transmission.

This transmission relates two actuators and two joints through a mechanism in which the state of the first joint only depends on the first actuator, while the second joint depends on both actuators, as illustrated below. Although the class name makes specific reference to the four-bar-linkage, there are other mechanical layouts that yield the same behavior, such as the remote actuation example also depicted below.

	Effort	Velocity	Position
Actuator to joint	$\begin{eqnarray} \tau_{j_1} & = & n_{j_1} n_{a_1} \tau_{a_1} \\ \tau_{j_2} & = & n_{j_2} (n_{a_2} \tau_{a_2} - n_{j_1} n_{a_1} \tau_{a_1}) \end{eqnarray}$	$\begin{eqnarray} \dot{x}_{j_1} & = & \frac{ \dot{x}_{a_1} }{ n_{j_1} n_{a_1} } \\ \dot{x}_{j_2} & = & \frac{ \dot{x}_{a_2} / n_{a_2} - \dot{x}_{a_1} / (n_{j_1} n_{a_1}) }{ n_{j_2} } \end{eqnarray}$	$\begin{eqnarray} x_{j_1} & = & \frac{ x_{a_1} }{ n_{j_1} n_{a_1} } + x_{off_1} \\ x_{j_2} & = & \frac{ x_{a_2} / n_{a_2} - x_{a_1} / (n_{j_1} n_{a_1}) }{ n_{j_2} } + x_{off_2} \end{eqnarray}$
Joint to actuator	$\begin{eqnarray} \tau_{a_1} & = & \tau_{j_1} / (n_{j_1} n_{a_1}) \\ \tau_{a_2} & = & \frac{ \tau_{j_1} + \tau_{j_2} / n_{j_2} }{ n_{a_2} } \end{eqnarray}$	$\begin{eqnarray} \dot{x}_{a_1} & = & n_{j_1} n_{a_1} \dot{x}_{j_1} \\ \dot{x}_{a_2} & = & n_{a_2} (\dot{x}_{j_1} + n_{j_2} \dot{x}_{j_2}) \end{eqnarray}$	$\begin{eqnarray} x_{a_1} & = & n_{j_1} n_{a_1} (x_{j_1} - x_{off_1}) \\ x_{a_2} & = & n_{a_2} \left[(x_{j_1} - x_{off_1}) + n_{j_2} (x_{j_2} - x_{off_2})\right] \end{eqnarray}$

where:

, $\dot{x}$ and $\tau$ are position, velocity and effort variables, respectively.
Subindices and 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. (cf. SimpleTransmission class documentation for a more detailed description of this variable).
represents a transmission ratio (reducers/amplifiers are depicted as timing belts in the figure). A 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 it's a velocity amplifier / effort reducer.
- Negative values represent a direction flip, ie. input and output move in opposite directions.
- Important: Use transmission ratio signs to match this class' convention of positive actuator/joint directions with a given mechanical design, as they will in general not match.

Definition at line 117 of file four_bar_linkage_transmission.h.

Constructor & Destructor Documentation

◆ FourBarLinkageTransmission()

transmission_interface::FourBarLinkageTransmission::FourBarLinkageTransmission	(	const std::vector< double > &	actuator_reduction,
		const std::vector< double > &	joint_reduction,
		const std::vector< double > &	joint_offset = `std::vector<double>(2, 0.0)`
	)

inline

Parameters

actuator_reduction	Reduction ratio of actuators.
joint_reduction	Reduction ratio of joints.
joint_offset	Joint position offset used in the position mappings.

Precondition: Nonzero actuator reduction values.

Definition at line 224 of file four_bar_linkage_transmission.h.

Member Function Documentation

◆ actuatorToJointAbsolutePosition()

void transmission_interface::FourBarLinkageTransmission::actuatorToJointAbsolutePosition	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)

overridevirtual

Transform absolute encoder values from actuator to joint space.

Parameters

[in]	act_data	Actuator-space variables.
[out]	jnt_data	Joint-space variables.

Precondition: Actuator, joint position and absolute encoder position vectors must have the same size. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Reimplemented from transmission_interface::Transmission.

Definition at line 286 of file four_bar_linkage_transmission.h.

◆ actuatorToJointEffort()

void transmission_interface::FourBarLinkageTransmission::actuatorToJointEffort	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)

inlineoverridevirtual

Transform effort variables from actuator to joint space.

Parameters

[in]	act_data	Actuator-space variables.
[out]	jnt_data	Joint-space variables.

Precondition: Actuator and joint effort vectors must have size 2 and point to valid data. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Implements transmission_interface::Transmission.

Definition at line 246 of file four_bar_linkage_transmission.h.

◆ actuatorToJointPosition()

void transmission_interface::FourBarLinkageTransmission::actuatorToJointPosition	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)

inlineoverridevirtual

Transform position variables from actuator to joint space.

Parameters

[in]	act_data	Actuator-space variables.
[out]	jnt_data	Joint-space variables.

Precondition: Actuator and joint position vectors must have size 2 and point to valid data. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Implements transmission_interface::Transmission.

Definition at line 272 of file four_bar_linkage_transmission.h.

◆ actuatorToJointTorqueSensor()

void transmission_interface::FourBarLinkageTransmission::actuatorToJointTorqueSensor	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)

overridevirtual

Transform torque sensor values from actuator to joint space.

Parameters

[in]	act_data	Actuator-space variables.
[out]	jnt_data	Joint-space variables.

Precondition: Actuator, joint position and torque sensor vectors must have the same size.

Reimplemented from transmission_interface::Transmission.

Definition at line 301 of file four_bar_linkage_transmission.h.

◆ actuatorToJointVelocity()

void transmission_interface::FourBarLinkageTransmission::actuatorToJointVelocity	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)

inlineoverridevirtual

Transform velocity variables from actuator to joint space.

Parameters

[in]	act_data	Actuator-space variables.
[out]	jnt_data	Joint-space variables.

Precondition: Actuator and joint velocity vectors must have size 2 and point to valid data. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Implements transmission_interface::Transmission.

Definition at line 259 of file four_bar_linkage_transmission.h.

◆ getActuatorReduction()

const std::vector<double>& transmission_interface::FourBarLinkageTransmission::getActuatorReduction ( ) const

inline

Definition at line 214 of file four_bar_linkage_transmission.h.

◆ getJointOffset()

const std::vector<double>& transmission_interface::FourBarLinkageTransmission::getJointOffset ( ) const

inline

Definition at line 216 of file four_bar_linkage_transmission.h.

◆ getJointReduction()

const std::vector<double>& transmission_interface::FourBarLinkageTransmission::getJointReduction ( ) const

inline

Definition at line 215 of file four_bar_linkage_transmission.h.

◆ hasActuatorToJointAbsolutePosition()

bool transmission_interface::FourBarLinkageTransmission::hasActuatorToJointAbsolutePosition ( ) const

inlineoverridevirtual

Reimplemented from transmission_interface::Transmission.

Definition at line 211 of file four_bar_linkage_transmission.h.

◆ hasActuatorToJointTorqueSensor()

bool transmission_interface::FourBarLinkageTransmission::hasActuatorToJointTorqueSensor ( ) const

inlineoverridevirtual

Reimplemented from transmission_interface::Transmission.

Definition at line 212 of file four_bar_linkage_transmission.h.

◆ jointToActuatorEffort()

void transmission_interface::FourBarLinkageTransmission::jointToActuatorEffort	(	const JointData &	jnt_data,
		ActuatorData &	act_data
	)

inlineoverridevirtual

Transform effort variables from joint to actuator space.

Parameters

[in]	jnt_data	Joint-space variables.
[out]	act_data	Actuator-space variables.

Precondition: Actuator and joint effort vectors must have size 2 and point to valid data. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Implements transmission_interface::Transmission.

Definition at line 316 of file four_bar_linkage_transmission.h.

◆ jointToActuatorPosition()

void transmission_interface::FourBarLinkageTransmission::jointToActuatorPosition	(	const JointData &	jnt_data,
		ActuatorData &	act_data
	)

inlineoverridevirtual

Transform position variables from joint to actuator space.

Parameters

[in]	jnt_data	Joint-space variables.
[out]	act_data	Actuator-space variables.

Precondition: Actuator and joint position vectors must have size 2 and point to valid data. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Implements transmission_interface::Transmission.

Definition at line 342 of file four_bar_linkage_transmission.h.

◆ jointToActuatorVelocity()

void transmission_interface::FourBarLinkageTransmission::jointToActuatorVelocity	(	const JointData &	jnt_data,
		ActuatorData &	act_data
	)

inlineoverridevirtual

Transform velocity variables from joint to actuator space.

Parameters

[in]	jnt_data	Joint-space variables.
[out]	act_data	Actuator-space variables.

Precondition: Actuator and joint velocity vectors must have size 2 and point to valid data. To call this method it is not required that all other data vectors contain valid data, and can even remain empty.

Implements transmission_interface::Transmission.

Definition at line 329 of file four_bar_linkage_transmission.h.

◆ numActuators()

std::size_t transmission_interface::FourBarLinkageTransmission::numActuators ( ) const

inlineoverridevirtual

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

Implements transmission_interface::Transmission.

Definition at line 209 of file four_bar_linkage_transmission.h.

◆ numJoints()

std::size_t transmission_interface::FourBarLinkageTransmission::numJoints ( ) const

inlineoverridevirtual

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

Implements transmission_interface::Transmission.

Definition at line 210 of file four_bar_linkage_transmission.h.

Member Data Documentation

◆ act_reduction_

std::vector<double> transmission_interface::FourBarLinkageTransmission::act_reduction_

protected

Definition at line 219 of file four_bar_linkage_transmission.h.

◆ jnt_offset_

std::vector<double> transmission_interface::FourBarLinkageTransmission::jnt_offset_

protected

Definition at line 221 of file four_bar_linkage_transmission.h.

◆ jnt_reduction_

std::vector<double> transmission_interface::FourBarLinkageTransmission::jnt_reduction_

protected

Definition at line 220 of file four_bar_linkage_transmission.h.

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

four_bar_linkage_transmission.h

	Effort	Velocity	Position
Actuator to joint	$\begin{eqnarray} \tau_{j_1} & = & n_{j_1} n_{a_1} \tau_{a_1} \\ \tau_{j_2} & = & n_{j_2} (n_{a_2} \tau_{a_2} - n_{j_1} n_{a_1} \tau_{a_1}) \end{eqnarray}$	$\begin{eqnarray} \dot{x}_{j_1} & = & \frac{ \dot{x}_{a_1} }{ n_{j_1} n_{a_1} } \\ \dot{x}_{j_2} & = & \frac{ \dot{x}_{a_2} / n_{a_2} - \dot{x}_{a_1} / (n_{j_1} n_{a_1}) }{ n_{j_2} } \end{eqnarray}$	$\begin{eqnarray} x_{j_1} & = & \frac{ x_{a_1} }{ n_{j_1} n_{a_1} } + x_{off_1} \\ x_{j_2} & = & \frac{ x_{a_2} / n_{a_2} - x_{a_1} / (n_{j_1} n_{a_1}) }{ n_{j_2} } + x_{off_2} \end{eqnarray}$
Joint to actuator	$\begin{eqnarray} \tau_{a_1} & = & \tau_{j_1} / (n_{j_1} n_{a_1}) \\ \tau_{a_2} & = & \frac{ \tau_{j_1} + \tau_{j_2} / n_{j_2} }{ n_{a_2} } \end{eqnarray}$	$\begin{eqnarray} \dot{x}_{a_1} & = & n_{j_1} n_{a_1} \dot{x}_{j_1} \\ \dot{x}_{a_2} & = & n_{a_2} (\dot{x}_{j_1} + n_{j_2} \dot{x}_{j_2}) \end{eqnarray}$	$\begin{eqnarray} x_{a_1} & = & n_{j_1} n_{a_1} (x_{j_1} - x_{off_1}) \\ x_{a_2} & = & n_{a_2} \left[(x_{j_1} - x_{off_1}) + n_{j_2} (x_{j_2} - x_{off_2})\right] \end{eqnarray}$

Public Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ FourBarLinkageTransmission()

Member Function Documentation

◆ actuatorToJointAbsolutePosition()

◆ actuatorToJointEffort()

◆ actuatorToJointPosition()

◆ actuatorToJointTorqueSensor()

◆ actuatorToJointVelocity()

◆ getActuatorReduction()

◆ getJointOffset()

◆ getJointReduction()

◆ hasActuatorToJointAbsolutePosition()

◆ hasActuatorToJointTorqueSensor()

◆ jointToActuatorEffort()

◆ jointToActuatorPosition()

◆ jointToActuatorVelocity()

◆ numActuators()

◆ numJoints()

Member Data Documentation

◆ act_reduction_

◆ jnt_offset_

◆ jnt_reduction_