src/cdlbt/dynamics.c File Reference

#include <syslog.h>
#include <libconfig.h>
#include <gsl/gsl_blas.h>
#include <barrett/cdlbt/dynamics.h>
#include <barrett/cdlbt/gsl.h>

Functions
int	bt_dynamics_create (struct bt_dynamics **dynptr, config_setting_t *dynconfig, int ndofs)
int	bt_dynamics_destroy (struct bt_dynamics *dyn)
int	bt_dynamics_eval_inverse (struct bt_dynamics *dyn, const struct bt_kinematics *kin, const gsl_vector *jvel, const gsl_vector *jacc, gsl_vector *jtor)
int	bt_dynamics_eval_jsim (struct bt_dynamics *dyn, struct bt_kinematics *kin)
Private functions
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Detailed Description

Implementation of bt_dynamics, a simple dynamics library which uses the Recursive Newton-Euler Algorithm for single-chain revolute robots.

Author:

Christopher Dellin

Date:

2008-2009

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Function Documentation

int bt_dynamics_create	(	struct bt_dynamics **	dynptr,
		config_setting_t *	dynconfig,
		int	ndofs
	)

Create a bt_dynamics object from a given configuration.

This function creates a new dynamics object, center-of-mass and inertial information from the configuration given by dynconfig. Currently, the number of moving links (ndofs) is also passed, and the creating fails if the number of moving links read from the configuration file does not match the expected number. It is also necessary to pass a previously-created bt_kinematics object for kinematics information.

Parameters:

[out]	dynptr	The bt_dynamics object on success, or 0 on failure
[in]	dynconfig	Dynamics configuration, from libconfig
[in]	ndofs	Expected number of moving links
[in]	kin	Previously-created bt_kinematics object describing robot

Return values:

0

Success

int bt_dynamics_destroy

(

struct bt_dynamics *

dyn

)

Destroy a bt_dynamics object.

This function destroys a bt_dynamics object created by bt_dynamics_create().

Parameters:

[in]

dyn

bt_dynamics object to destroy

Return values:

0

Success

int bt_dynamics_eval_inverse	(	struct bt_dynamics *	dyn,
		const struct bt_kinematics *	kin,
		const gsl_vector *	jvel,
		const gsl_vector *	jacc,
		gsl_vector *	jtor
	)

Evaluate inverse dynamics using the RNEA, both forward and backward.

This function is used in a control loop to calculate the inverse dynamics of the robot, given a particular configuration (calculated in the kinematics object), set of joint velocities, and set of desired joint accelerations. The resulting joint torques are stored in jtor.

Note:

Throw a switch in there for gravity on/off?

How to account for base acceleration (even gravity?)

This takes ~ 152us on PC104 right now.

Parameters:

[in]	dyn	bt_dynamics object
[in]	jvel	Present joint velocity vector
[in]	jacc	Desired joint acceleration vector
[out]	jtor	Computed joint torque vector

Return values:

0

Success

int bt_dynamics_eval_jsim	(	struct bt_dynamics *	dyn,
		struct bt_kinematics *	kin
	)

Calculate the Joint-Space Inertia Matrix (JSIM).

The formulation used is the explicit formulation given in Spong, Hutchinson, and Vidyasagar: Robot Modeling and Control, 2006 page 254.

Parameters:

[in]

dyn

bt_dynamics object