qb_device_joint_limits_interface::PositionJointSaturationInterface Class Reference

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

#include <qb_device_joint_limits_interface.h>

Inheritance diagram for qb_device_joint_limits_interface::PositionJointSaturationInterface:

Public Member Functions
Real-Time Safe Functions
void	reset ()
	Reset all managed handles. More...
Public Member Functions inherited from joint_limits_interface::JointLimitsInterface< HandleType >
void	enforceLimits (const ros::Duration &period)
void	enforceLimits (const ros::Duration &period)
HandleType	getHandle (const std::string &name)

Detailed Description

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

Note

: The only difference from joint_limits_interface::PositionJointSoftLimitsHandle is that this exploit a dynamical management of the joint limits, i.e. the limits can be modified at runtime by others.

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. Construct the saturation handle with dynamic joint limits.

Parameters

joint_handle	The joint handle of interest.
limits	The pointer to the joint limits structure of the joint. Enforce position and velocity limits for a joint that is subject to soft limits.

Note

: Be aware of dynamic joint limits.

Parameters

period

The control period.

Returns

The joint name. Reset the interface state. Interface for enforcing limits on a position-controlled joint through saturation. The only difference from joint_limits_interface::PositionJointSaturationInterface is that this exploit a dynamical management of the joint limits, i.e. the limits can be modified at runtime by others.

Definition at line 201 of file qb_device_joint_limits_interface.h.

Member Function Documentation

void qb_device_joint_limits_interface::PositionJointSaturationInterface::reset ( )

inline

Reset all managed handles.

Definition at line 207 of file qb_device_joint_limits_interface.h.

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

• qb_device_joint_limits_interface.h