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

#include <four_bar_linkage_transmission.h>

Inheritance diagram for transmission_interface::FourBarLinkageTransmission:

Public Member Functions
void	actuatorToJointEffort (const ActuatorData &act_data, JointData &jnt_data)
	Transform effort variables from actuator to joint space.
void	actuatorToJointPosition (const ActuatorData &act_data, JointData &jnt_data)
	Transform position variables from actuator to joint space.
void	actuatorToJointVelocity (const ActuatorData &act_data, JointData &jnt_data)
	Transform velocity variables from actuator to joint space.
	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
void	jointToActuatorEffort (const JointData &jnt_data, ActuatorData &act_data)
	Transform effort variables from joint to actuator space.
void	jointToActuatorPosition (const JointData &jnt_data, ActuatorData &act_data)
	Transform position variables from joint to actuator space.
void	jointToActuatorVelocity (const JointData &jnt_data, ActuatorData &act_data)
	Transform velocity variables from joint to actuator space.
std::size_t	numActuators () const
std::size_t	numJoints () const
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

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 203 of file four_bar_linkage_transmission.h.

Member Function Documentation

void transmission_interface::FourBarLinkageTransmission::actuatorToJointEffort	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)		`[inline, virtual]`

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 226 of file four_bar_linkage_transmission.h.

void transmission_interface::FourBarLinkageTransmission::actuatorToJointPosition	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)		`[inline, virtual]`

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 252 of file four_bar_linkage_transmission.h.

void transmission_interface::FourBarLinkageTransmission::actuatorToJointVelocity	(	const ActuatorData &	act_data,
		JointData &	jnt_data
	)		`[inline, virtual]`

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 239 of file four_bar_linkage_transmission.h.

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

Definition at line 193 of file four_bar_linkage_transmission.h.

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

Definition at line 195 of file four_bar_linkage_transmission.h.

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

Definition at line 194 of file four_bar_linkage_transmission.h.

void transmission_interface::FourBarLinkageTransmission::jointToActuatorEffort	(	const JointData &	jnt_data,
		ActuatorData &	act_data
	)		`[inline, virtual]`

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 266 of file four_bar_linkage_transmission.h.

void transmission_interface::FourBarLinkageTransmission::jointToActuatorPosition	(	const JointData &	jnt_data,
		ActuatorData &	act_data
	)		`[inline, virtual]`

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 292 of file four_bar_linkage_transmission.h.

void transmission_interface::FourBarLinkageTransmission::jointToActuatorVelocity	(	const JointData &	jnt_data,
		ActuatorData &	act_data
	)		`[inline, virtual]`

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 279 of file four_bar_linkage_transmission.h.

std::size_t transmission_interface::FourBarLinkageTransmission::numActuators ( ) const [inline, virtual]

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

Implements transmission_interface::Transmission.

Definition at line 190 of file four_bar_linkage_transmission.h.

std::size_t transmission_interface::FourBarLinkageTransmission::numJoints ( ) const [inline, virtual]

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

Implements transmission_interface::Transmission.

Definition at line 191 of file four_bar_linkage_transmission.h.

Member Data Documentation

std::vector<double> transmission_interface::FourBarLinkageTransmission::act_reduction_ [protected]

Definition at line 198 of file four_bar_linkage_transmission.h.

std::vector<double> transmission_interface::FourBarLinkageTransmission::jnt_offset_ [protected]

Definition at line 200 of file four_bar_linkage_transmission.h.

std::vector<double> transmission_interface::FourBarLinkageTransmission::jnt_reduction_ [protected]

Definition at line 199 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

Member Function Documentation

Member Data Documentation