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.
std::string	getName () const
	PositionJointSoftLimitsHandle ()
	PositionJointSoftLimitsHandle (const hardware_interface::JointHandle &jh, const JointLimits &limits, const SoftJointLimits &soft_limits)
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 comand 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 156 of file joint_limits_interface.h.

Constructor & Destructor Documentation

joint_limits_interface::PositionJointSoftLimitsHandle::PositionJointSoftLimitsHandle ( ) [inline]

Definition at line 159 of file joint_limits_interface.h.

joint_limits_interface::PositionJointSoftLimitsHandle::PositionJointSoftLimitsHandle	(	const hardware_interface::JointHandle &	jh,
		const JointLimits &	limits,
		const SoftJointLimits &	soft_limits
	)		`[inline]`