joint_limits_interface::PositionJointSoftLimitsHandle Class Reference

A handle used to enforce position and velocity limits of a position-controlled joint. More...

#include <joint_limits_interface.h>

Public Member Functions
void	enforceLimits (const ros::Duration &period)
	Enforce position and velocity limits for a joint subject to soft limits. More...
std::string	getName () const
	PositionJointSoftLimitsHandle ()
	PositionJointSoftLimitsHandle (const hardware_interface::JointHandle &jh, const JointLimits &limits, const SoftJointLimits &soft_limits)
void	reset ()
	Reset state, in case of mode switch or e-stop. More...

Private Attributes
hardware_interface::JointHandle	jh_
JointLimits	limits_
double	prev_cmd_
SoftJointLimits	soft_limits_

Detailed Description

A handle used to enforce position and velocity limits of a position-controlled joint.

This class implements a very simple position and velocity limits enforcing policy, and tries to impose the least amount of requisites on the underlying hardware platform. This lowers considerably the entry barrier to use it, but also implies some limitations.

Requisites

• Position (for non-continuous joints) and velocity limits specification.
• Soft limits specification. The k_velocity parameter is not used.

Open loop nature

Joint position and velocity limits are enforced in an open-loop fashion, that is, the command is checked for validity without relying on the actual position/velocity values.

• Actual position values are not used because in some platforms there might be a substantial lag between sending a command and executing it (propagate command to hardware, reach control objective, read from hardware).
• Actual velocity values are not used because of the above reason, and because some platforms might not expose trustworthy velocity measurements, or none at all.

The downside of the open loop behavior is that velocity limits will not be enforced when recovering from large position tracking errors. Only the command is guaranteed to comply with the limits specification.

Note

: This handle type is stateful, ie. it stores the previous position command to estimate the command velocity.

Definition at line 161 of file joint_limits_interface.h.

Constructor & Destructor Documentation

joint_limits_interface::PositionJointSoftLimitsHandle::PositionJointSoftLimitsHandle ( )

inline

Definition at line 164 of file joint_limits_interface.h.

joint_limits_interface::PositionJointSoftLimitsHandle::PositionJointSoftLimitsHandle ( const hardware_interface::JointHandle &  jh, const JointLimits &  limits, const SoftJointLimits &  soft_limits  )

inline

Definition at line 168 of file joint_limits_interface.h.

Member Function Documentation

void joint_limits_interface::PositionJointSoftLimitsHandle::enforceLimits ( const ros::Duration &  period )

inline

Enforce position and velocity limits for a joint subject to soft limits.

If the joint has no position limits (eg. a continuous joint), only velocity limits will be enforced.

Parameters

period

Control period.

Definition at line 192 of file joint_limits_interface.h.

std::string joint_limits_interface::PositionJointSoftLimitsHandle::getName ( ) const

inline

Returns

Joint name.

Definition at line 184 of file joint_limits_interface.h.

void joint_limits_interface::PositionJointSoftLimitsHandle::reset ( )

inline

Reset state, in case of mode switch or e-stop.

Definition at line 250 of file joint_limits_interface.h.

Member Data Documentation

hardware_interface::JointHandle joint_limits_interface::PositionJointSoftLimitsHandle::jh_

private

Definition at line 255 of file joint_limits_interface.h.

JointLimits joint_limits_interface::PositionJointSoftLimitsHandle::limits_

private

Definition at line 256 of file joint_limits_interface.h.

double joint_limits_interface::PositionJointSoftLimitsHandle::prev_cmd_

private

Definition at line 259 of file joint_limits_interface.h.

SoftJointLimits joint_limits_interface::PositionJointSoftLimitsHandle::soft_limits_

private

Definition at line 257 of file joint_limits_interface.h.

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

• joint_limits_interface.h