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2012-03-28 01:12:52 -0500	answered a question	Choosing the right coefficients for Gazebo simulation Here is the output from Solidworks for the chassis: Output coordinate System: -- default -- Mass = 489.90 grams Volume = 181445.50 cubic millimeters Surface area = 189380.73 millimeters^2 Center of mass: ( millimeters ) X = 41.53 Y = 93.76 Z = 131.23 Principal axes of inertia and principal moments of inertia: ( grams * square millimeters ) Taken at the center of mass. Ix = (0.00, 0.01, 1.00) Px = 4157521.05 Iy = (1.00, 0.00, 0.00) Py = 5704820.80 Iz = (0.00, 1.00, -0.01) Pz = 9356042.65 Moments of inertia: ( grams * square millimeters ) Taken at the center of mass and aligned with the output coordinate system. Lxx = 5704820.80 Lxy = 0.00 Lxz = -0.00 Lyx = 0.00 Lyy = 9355391.53 Lyz = 58176.21 Lzx = -0.00 Lzy = 58176.21 Lzz = 4158172.18 Moments of inertia: ( grams * square millimeters ) Taken at the output coordinate system. Ixx = 18448329.91 Ixy = 1907623.47 Ixz = 2669963.78 Iyx = 1907623.47 Iyy = 18637105.26 Iyz = 6086030.51 Izx = 2669963.78 Izy = 6086030.51 Izz = 9309884.18 And here is how I've put it in URDF: `<link name="base_link"> <inertial> <mass value="${chassis_mass}" /> <origin xyz="0.04153 0.09376 0.13123" /> <inertia ixx="0.00415752105" ixy="0.0" ixz="0.0" iyy="0.0057048208" iyz="0.0" izz="0.00935604265" /> </inertial>` Is this correct? I guess this is only correct if my model has the coordinate system aligned with the representation from Gazebo, right?
2012-03-27 01:25:16 -0500	received badge	● Editor (source)
2012-03-27 01:24:10 -0500	asked a question	Choosing the right coefficients for Gazebo simulation Hello, I am trying to create an URDF and simulate it in Gazebo for a 4WD Skid steering robot. The chasis is actually a box with the following properties: body_width (base_size_y) : 22 cm body_length (base_size_x) : 27 cm body_height (base_size_z) : 5 cm body_mass : 5 kg and wheels: wheel_diameter : 0.12065 m wheel_width : 0.060325 m wheel_mass 0.181436948 kg I have created the URDF and a differential drive plugin for gazebo to simulate the model but I have no idea how to choose appropriate values for torque, mu1, mu2, kp, kd and inertia matrix. The values that I am currently using are taken/combined from the erratic/guardian/turtlebot stacks. By publishing the odometry (calculated in the plugin) and comparing the robot's position in Gazebo and RViz I can see that the model slips a lot while performing turns. Relevant files: myrobot.urdf.xacro myrobot_constants.xacro myrobot_wheel.xacro myrobot_materials.xacro Any help is appreciated. Thanks in advance. Update: Here is the output from Solidworks for the chassis: Output coordinate System: -- default -- Mass = 489.90 grams Volume = 181445.50 cubic millimeters Surface area = 189380.73 millimeters^2 Center of mass: ( millimeters ) X = 41.53 Y = 93.76 Z = 131.23 Principal axes of inertia and principal moments of inertia: ( grams * square millimeters ) Taken at the center of mass. Ix = (0.00, 0.01, 1.00) Px = 4157521.05 Iy = (1.00, 0.00, 0.00) Py = 5704820.80 Iz = (0.00, 1.00, -0.01) Pz = 9356042.65 Moments of inertia: ( grams * square millimeters ) Taken at the center of mass and aligned with the output coordinate system. Lxx = 5704820.80 Lxy = 0.00 Lxz = -0.00 Lyx = 0.00 Lyy = 9355391.53 Lyz = 58176.21 Lzx = -0.00 Lzy = 58176.21 Lzz = 4158172.18 Moments of inertia: ( grams * square millimeters ) Taken at the output coordinate system. Ixx = 18448329.91 Ixy = 1907623.47 Ixz = 2669963.78 Iyx = 1907623.47 Iyy = 18637105.26 Iyz = 6086030.51 Izx = 2669963.78 Izy = 6086030.51 Izz = 9309884.18 And here is how I've put it in URDF: `<link name="base_link"> <inertial> <mass value="${chassis_mass}" /> <origin xyz="0.04153 0.09376 0.13123" /> <inertia ixx="0.00415752105" ixy="0.0" ixz="0.0" iyy="0.0057048208" iyz="0.0" izz="0.00935604265" /> </inertial>` Is this correct? I guess this is only correct if my model has the coordinate system aligned with the representation from Gazebo, right?
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2011-12-04 06:33:29 -0500	asked a question	RGBDSLAM Ubuntu 11.10 Hello, I'm trying to build RGBDSLAM on a Ubuntu 11.10 32bit and ROS Electric. The build fails with the following output: http://pastebin.com/1SNcy0pR
2011-12-03 00:23:17 -0500	asked a question	usb_cam low FPS from webcam Hello, I found out I can use usb_cam to publish images from my webcam. I tested it with my laptop's webcam and it performs poorly, only 7 FPS. OS: Ubuntu 11.10 Oneric ROS: Electric (installed via apt-get) dmesg output regarding webcam: [ 7209.629430] usb 2-1: USB disconnect, device number 3 [ 7211.188071] usb 2-1: new high speed USB device number 6 using ehci_hcd [ 7211.383400] uvcvideo: Found UVC 1.00 device CNF7231 (04f2:b073) [ 7211.395092] input: CNF7231 as /devices/pci0000:00/0000:00:1d.7/usb2/2-1/2-1:1.0/input/input11 I downloaded http://www.ros.org/wiki/usb_cam and compiled it using rosmake. Compilation log: http://pastebin.com/rJYMR0Bw As you can see it complains about libswscale (although I have it installed) but it managed to compile it. Starting usb_cam gives the following output: http://pastebin.com/6JQ2CSpP Any ideas? Thanks in advance.