# KDL - Calculation of Dynamics - how to integrate frame taking Torque into account

Submitted by niebieski222 on Sat, 2013-10-12 21:00 |

In KDL package there is a nice example how to use KDL - namely -

kukaLWRtestDHnew.cpp

Most of this example seems clear:

Chain kLWR=KukaLWR_DHnew();

JntArray q(kLWR.getNrOfJoints());

JntArray qdot(kLWR.getNrOfJoints());

JntArray qdotdot(kLWR.getNrOfJoints());

JntArray tau(kLWR.getNrOfJoints());

Wrenches f(kLWR.getNrOfSegments());

Frame T;

int errorInputs = getInputs(q, qdot,qdotdot,linenum);

ChainIdSolver_RNE idsolver(kLWR,Vector(0.0,0.0,-9.81));

idsolver.CartToJnt(q,qdot,qdotdot,f,tau);

The *idsolver* object (*ChainIdSolver_RNE* class) should calculate Torques

originating from gravity force acting on segments.

How to incorporate these Tau Torques to the chain and integrate whole chain

by new deltaTime?

At http://www.orocos.org/kdl/usermanual/geometric-primitives#toc39 - I've

found that next time frame can be calculated by command:

F_w_B = F_w_A.addDelta(t,timestep)//integration

Where the F_w_a, F_w_B are frames, t is an array of twists (angular

and linear velocities of segments) and timestep is delaTime [s].

But this integration looks like it is purely kinematic - it would not

take Torques Tau acting upon segments into account.

How to do it ? How to calculate new positions of segments/chain in

deltaTime seconds later taking Torques into account?

Really requiring a helping hand

Conrad

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