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URDF files dont work

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Tim De Witte
Tim De Witte el 20 de Abr. de 2024
Comentada: Tim De Witte el 23 de Abr. de 2024
robot = importrobot('irb6640.urdf');
by using a irb6640.urdf file from the internet the code I used for generating a robot traject doesnt work.
I tried this for different urdf files but the code can't run the inverse dynamics for some reason. Normally this should be possible. I need this for my thesis :(. Does someone know what I did wrong . this is the urdf file <?xml version="1.0" ?>
<!-- =================================================================================== -->
<!-- | This document was autogenerated by xacro from irb6640.xacro | -->
<!-- | EDITING THIS FILE BY HAND IS NOT RECOMMENDED | -->
<!-- =================================================================================== -->
<robot name="abb_irb6640" xmlns:xacro="http://ros.org/wiki/xacro">
<link name="base_link">
<collision name="collision">
<geometry>
<mesh filename="package://collision/base_link.stl"/>
</geometry>
<material name="yellow">
<color rgba="0 1 1 1"/>
</material>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/base_link.stl"/>
</geometry>
<material name="orange">
<color rgba="1 0.43 0 1"/>
</material>
</visual>
</link>
<link name="link_1">
<collision name="collision">
<geometry>
<mesh filename="package://collision/link_1.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/link_1.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="link_2">
<collision name="collision">
<geometry>
<mesh filename="package://collision/link_2.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/link_2.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="link_3">
<collision name="collision">
<geometry>
<mesh filename="package://collision/link_3.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/link_3.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="link_4">
<collision name="collision">
<geometry>
<mesh filename="package://collision/link_4.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/link_4.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="link_5">
<collision name="collision">
<geometry>
<mesh filename="package://collision/link_5.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/link_5.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="link_6">
<collision name="collision">
<geometry>
<mesh filename="package://collision/link_6.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/link_6.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="tool0"/>
<link name="link_cylinder">
<collision name="collision">
<geometry>
<mesh filename="package://collision/cylinder.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/cylinder.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<link name="link_piston">
<collision name="collision">
<geometry>
<mesh filename="package://collision/piston.stl"/>
</geometry>
<material name="yellow"/>
</collision>
<visual name="visual">
<geometry>
<mesh filename="package://visual/piston.stl"/>
</geometry>
<material name="orange"/>
</visual>
</link>
<joint name="joint_1" type="revolute">
<origin rpy="0 0 0" xyz="0 0 0.227"/>
<axis xyz="0 0 1"/>
<parent link="base_link"/>
<child link="link_1"/>
<limit effort="0" lower="-2.967" upper="2.967" velocity="1.7453"/>
</joint>
<joint name="joint_2" type="revolute">
<origin rpy="0 0 0" xyz="0.322 0.03 0.551"/>
<axis xyz="0 1 0"/>
<parent link="link_1"/>
<child link="link_2"/>
<limit effort="0" lower="-1.134" upper="1.4855" velocity="1.5707"/>
</joint>
<joint name="joint_3" type="revolute">
<origin rpy="0 0 0" xyz="0 -0.2 1.07"/>
<axis xyz="0 1 0"/>
<parent link="link_2"/>
<child link="link_3"/>
<limit effort="0" lower="-3.142" upper="1.222" velocity="1.5707"/>
</joint>
<joint name="joint_4" type="revolute">
<origin rpy="0 0 0" xyz="-0.275 0.181 0.2"/>
<axis xyz="1 0 0"/>
<parent link="link_3"/>
<child link="link_4"/>
<limit effort="0" lower="-5.236" upper="5.236" velocity="2.9671"/>
</joint>
<joint name="joint_5" type="revolute">
<origin rpy="0 0 0" xyz="1.67 0 0 "/>
<axis xyz="0 1 0"/>
<parent link="link_4"/>
<child link="link_5"/>
<limit effort="0" lower="-2.094" upper="2.094" velocity="2.4435"/>
</joint>
<joint name="joint_6" type="revolute">
<origin rpy="0 0 0" xyz="0.153 0 0 "/>
<axis xyz="1 0 0"/>
<parent link="link_5"/>
<child link="link_6"/>
<limit effort="0" lower="-6.283" upper="6.283" velocity="3.3161"/>
</joint>
<joint name="joint_6-tool0" type="fixed">
<parent link="link_6"/>
<child link="tool0"/>
<origin rpy="0 1.57079632679 0" xyz=".055 0 0"/>
</joint>
<joint name="joint_cylinder" type="fixed">
<origin rpy="0 -0.170 0" xyz="-0.365 -0.1895 0.405"/>
<axis xyz="0 1 0"/>
<parent link="link_1"/>
<child link="link_cylinder"/>
<limit effort="0" lower="-2.96705973" upper="2.96705973" velocity="0"/>
</joint>
<joint name="joint_piston" type="fixed">
<origin rpy="0 0 0" xyz="0.475 0 0"/>
<axis xyz="1 0 0"/>
<parent link="link_cylinder"/>
<child link="link_piston"/>
<limit effort="0" lower="0" upper="0.6" velocity="0"/>
</joint>
<link name="base"/>
<joint name="base_link-base" type="fixed">
<origin rpy="0 0 0" xyz="0 0 0"/>
<parent link="base_link"/>
<child link="base"/>
</joint>
</robot>

Respuestas (1)

Gaurav Bhosale
Gaurav Bhosale el 22 de Abr. de 2024
Editada: Gaurav Bhosale el 22 de Abr. de 2024
Hi Tim De Witte,
I am able to run shared URDF without any issue.
Can you please share me more details such as MATLAB version, error/warning message details or reproduction steps ?
Thanks
  6 comentarios
Tim De Witte
Tim De Witte el 23 de Abr. de 2024
I dont get an error but the power calculations are zero when i run the code which is weird. Do you have a working power calculations.
clear all
clc
close all
% Create the Robot Model
% (*** List of other built-in robot models:)
% *** https://nl.mathworks.com/help/robotics/ref/loadrobot.html)
%
% Create a Rigid Body Tree for the robot, set the home configuration and
% calculate the transformation at the home configuration:
robot = importrobot('irb6640.urdf');
% 7-axis manipulator
% Continuous payload: 4 kg / 8.8 lbs
% Maximum reach: 902 mm
% Weight: 8.2 kg / 18 lbs
% Power consumption: 36 W
% loadrobot(robotname) loads a robot model from the robot library as a
% rigidBodyTree object.
% To import other robot models in Unified Robot Description Format (URDF),
% XML Macros (Xacro), or Simulation Description Format (SDF) file
% or Simscape Multibody model, the 'importrobot' function can be used.
robot.Gravity = [0 0 -9.81];
robot.DataFormat = 'column';
% To see robot details:
% showdetails(robot)
% Define arbitrary home configuration
q_home = [0 0 0 0 0 0]'*pi/180;
% Another option would be to create a random home configuration:
% q_home = randomConfiguration(robot);
% To interact with the robot model:
% interactiveGUI = interactiveRigidBodyTree(robot);
show(robot,q_home);
axis auto;
view([60,10]); % camera line of sight view(az,el)
% To see the names of links:
% robot.BodyNames
% (or "showdetails(robot)")
% The end-effector is the last body. Its name is 'EndEffector_Link'
% So we can define:
% eeName = 'EndEffector_Link';
% A more automated way to identify the end-effector is:
eeName = string(robot.BodyNames(length(robot.BodyNames)));
% The home configuration is described by a homogeneous transformation
% matrix:
T_home = getTransform(robot, q_home, eeName);
% From T_home we can determine the position of the end-effector (we
% extract the first 3 components of the last 4x1 column):
toolPositionHome = T_home(1:3,4);
% Define a Set of Waypoints Based on the Tool Position
waypoints = toolPositionHome + ...
[0 0 0 ; 1 2 5 ; 3 4 6 ; 1 1 1 ; 0 0 0]';
% EXERCISE: how to have the robot stopping for a few seconds at a
% specified point?
% Let's define the desired orientation of the end-effector in the
% waypoints.
% The orientation is represented in Euler angles and the convention used
% is the Tait-Bryan, extrinsic ZYX. Extrinsic rotations apply to axis
% in world coordinate system.
orientations = [-2.845 -0.971 -0.569;
0.26 -0.85 2.82;
0.175 0.625 2.89;
0.421 -0.744 -2.81;
-2.845 -0.971 -0.569;
]';
waypointTimes = [0 4 8 12 16];
% The trajectory will be divided into "Number_of_steps" steps:
Number_of_steps = 100;
% Time is discretized in steps of duration ts:
ts = waypointTimes(length(waypointTimes))/Number_of_steps;
% Vector of discretized times:
trajTimes = 0:ts:waypointTimes(end);
% End effector velocity at waypoints:
waypointVels = 5 *[ 0 1 0;
-1 0 0;
0 -1 0;
1 0 0;
0 1 0]';
% Acceleration at waypoints is computed from velocity. But first we must
% allocate memory for accelerations:
waypointAccels = zeros(size(waypointVels));
waypointAccelTimes = diff(waypointTimes)/4;
% Create Inverse Kinematics Solver and set solver parameters. The
% algorithm for solving inverse kinematics can be specified: either
% 'BFGSGradientProjection' (default) or 'LevenbergMarquardt'.
ik = inverseKinematics('RigidBodyTree',robot);
% Weights for pose tolerances, specified as a six-element vector.
% The first three elements of the vector correspond to the weights
% on the error in orientation for the desired pose.
% The last three elements of the vector correspond to the weights on
% the error in the xyz position for the desired pose.
ikWeights = [1 1 1 1 1 1];
% inverseKinematics has several additional options (e.g. max number of
% interations, joint limits, tolerances, etc.)
% The numerical solution starts from an initial guess, taken here as the
% home configuration:
ikInitGuess = q_home';
% Angles are adapted so to be between -pi e +pi:
ikInitGuess(ikInitGuess > pi) = ikInitGuess(ikInitGuess > pi) - 2*pi;
ikInitGuess(ikInitGuess < -pi) = ikInitGuess(ikInitGuess < -pi) + 2*pi;
plotMode = 2; % 0 = None, 1 = Trajectory, 2 = Coordinate Frames
show(robot,q_home,'Frames','off','PreservePlot',false);
hold on
if plotMode == 1
hTraj = plot3(waypoints(1,1),waypoints(2,1),waypoints(3,1),'b.-');
end
plot3(waypoints(1,:),waypoints(2,:),waypoints(3,:),'ro','LineWidth',2);
axis auto;
view([30 15]);
% The inverse kinematics problem can be solved with reference to
% positions only, or we can also include the orientation of the EE
% by setting the following Boolean flag to "true":
includeOrientation = false;
numWaypoints = size(waypoints,2); % Number of waypoints
numJoints = numel(robot.homeConfiguration);
% Allocate memory:
jointWaypoints = zeros(numJoints,numWaypoints);
% Waypoints have been defined in Cartesian coordinates. They must be
% converted to the corresponding homogeneous transformation. This is done
% using "trvec2tform".
% Orientations have been described using Euler's angles (Tait-Bryan,
% extrinsic ZYX). They must be transformed into homogeneous transformation.
% This is done by the command "eul2tform".
for idx = 1:numWaypoints
if includeOrientation
tgtPose = trvec2tform(waypoints(:,idx)') * eul2tform(orientations(:,idx)');
else
tgtPose = trvec2tform(waypoints(:,idx)') * eul2tform([pi/2 0 pi/2]);
end
[config,info] = ik(eeName,tgtPose,ikWeights',ikInitGuess');
jointWaypoints(:,idx) = config';
end
% The trajectory is generated by interpolating between waypoints. The
% interpolation can be done in differen ways:
% - trap: trapezoidal
% - cubic
% - quintic
% - bspline
trajType = 'bspline';
switch trajType
case 'trap'
[q,qd,qdd] = trapveltraj(jointWaypoints,numel(trajTimes), ...
'AccelTime',repmat(waypointAccelTimes,[numJoints 1]), ...
'EndTime',repmat(diff(waypointTimes),[numJoints 1]));
case 'cubic'
[q,qd,qdd] = cubicpolytraj(jointWaypoints,waypointTimes,trajTimes, ...
'VelocityBoundaryCondition',zeros(numJoints,numWaypoints));
case 'quintic'
[q,qd,qdd] = quinticpolytraj(jointWaypoints,waypointTimes,trajTimes, ...
'VelocityBoundaryCondition',zeros(numJoints,numWaypoints), ...
'AccelerationBoundaryCondition',zeros(numJoints,numWaypoints));
case 'bspline'
ctrlpoints = jointWaypoints; % Can adapt this as needed
[q,qd,qdd] = bsplinepolytraj(ctrlpoints,waypointTimes([1 end]),trajTimes);
% Remove the first velocity sample
qd(:,1) = zeros (6,1);
otherwise
error('Invalid trajectory type! Use ''trap'', ''cubic'', ''quintic'', or ''bspline''');
end
for idx = 1:numel(trajTimes)
config = q(:,idx)';
% Find Cartesian points for visualization
eeTform = getTransform(robot,config',eeName);
% plotMode == 1 means "show trajectory"; "0" was: nothing;
% "2" was: show axes
if plotMode == 1
eePos = tform2trvec(eeTform);
set(hTraj,'xdata',[hTraj.XData eePos(1)], ...
'ydata',[hTraj.YData eePos(2)], ...
'zdata',[hTraj.ZData eePos(3)]);
elseif plotMode == 2
plotTransforms(tform2trvec(eeTform),tform2quat(eeTform),'FrameSize',0.05);
end
% Show the robot
show(robot,config','Frames','off','PreservePlot',false);
title(['Trajectory at t = ' num2str(trajTimes(idx))])
drawnow
end
% Let's compute joint torques and power.
%
% Number of time intervals:
N = numel(trajTimes);
% jointTorq = inverseDynamics(gen3,q(:,1)',qd(:,1)',qdd(:,1)')
% preallocate memory:
jointTorques = zeros(numJoints,N);
Power = zeros(1,N); % vector with N 0's
TotalPower = zeros(1,N);
JointPower = zeros(numJoints,N);
for i = 1:N
jointTorques(:,i) = inverseDynamics(robot,q(:,i),qd(:,i),qdd(:,i));
Power(i) = dot(qd(:,i),jointTorques(:,i)); % scalar product
JointPower(:,i) = qd(:,i).*jointTorques(:,i); % element-wise product
TotalPower(i) = sumabs(JointPower(:,i)); % sum of absolute values
end
figure
plot(trajTimes,Power,'b-o')
hold on
plot(trajTimes,TotalPower,'r-*')
title('Power')
xlabel('Time [s]')
ylabel('Power [W]')
hold off
legend('Total power (algebraic)','Total power (Absolute values)')
figure
plot(trajTimes,jointTorques)
title('Joint torques')
xlabel('Time [s]')
ylabel('Joint torques [Nm]')
Tim De Witte
Tim De Witte el 23 de Abr. de 2024
maybe you can share your output?

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