Changes between Initial Version and Version 1 of Hand/282/MassProperties


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Timestamp:
Jul 11, 2013, 1:52:27 PM (11 years ago)
Author:
dc
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  • Hand/282/MassProperties

    v1 v1  
     1= Inertial Tensors and Mass Properties for the BarrettHand BH8-280 =
     2
     3The inertial properties calculated here represent the masses and inertias of each link of the BarrettHand BH8-280. All calculations were made using SolidWorks 2012 SP 3.0 and CAD models that include all mechanical components of the hand (including fasteners) and all electrical components except wiring. To verify that the SolidWorks model was correct, assemblies and parts of an actual hand were massed for comparison.
     4
     5The mass of an actual finger was measured at 179 g, which matches the mass of the CAD model. The hand base (including pucks and finger motors) measured 664 g while SolidWorks calculated the mass of the CAD model to be only 643 g. This discrepancy could come from a number of sources:
     6
     7 1. Lack of wiring in CAD
     8 1. Lack of grease in CAD
     9 1. Inadequately modeled PCB and components
     10
     11Further investigation narrowed the source of error to electrical subassemblies with dozens of strands of wire, all of which were omitted in the CAD model. To replicate the mass of these wires, slugs of the missing mass were created to fill the cavities in which wires could run. The base CAD model used in the calculations below measures 664 g.
     12
     13In the following images, all parts are left transparent to display all parts of the mass calculations. Yellow denotes frame parts, red denotes electrical pieces, and blue is for motors and drivetrain components.
     14
     15The following inertial frames are established on the hand. In each of the following diagrams, coordinate systems are oriented with the Z-axis coincident to the axis of rotation of each joint. These inertial frames follow the same convention as on the BarrettHand BH8-262.
     16[[Image(AllFrames_crop.jpg)]]
     17
     18Since no one is likely to wish to attempt computed-torque control on the Hand axes (since the frictions in the Hand are very high), the backdriven, reflected drive inertias of the drives were not computed. Since backdriven drive inertias have no effect on gravity terms, the frame inertias should give you good results for controlling the WAM arm and wrist torques as functions of hand-finger positions.
     19
     20You may also view mass properties of the entire hand in various configurations here: [http://web.barrett.com/support/BarrettHand_Documentation/BarrettHand280MassProp-2010Dec10.pdf]
     21
     22
     23== Mass Properties for Frame W (hand base frame) with palm pad ==
     24
     25[[Image(HandFrameW_NoDialog_crop.jpg)]]
     26
     27Output coordinate System: Frame W (opaque)
     28
     29Mass = 0.60858 kilograms
     30
     31Volume = 0.00024871 cubic meters
     32
     33Surface area = 0.24908 square meters
     34
     35Center of mass: (meters)
     36 X = 5.0019e-005 Y = -0.0044561 Z = 0.037268
     37
     38Principal axes of inertia and principal moments of inertia: (kilograms * square meters)
     39Taken at the center of mass.
     40 || Ix = (0.0025349, 0.91612, -0.4009) || Px = 0.00047536
     41 || Iy = (0.012636, -0.40089, -0.91604) || Py = 0.0006507
     42 || Iz = (-0.99992, -0.0027435, -0.012592) || Pz = 0.00069861
     43
     44Moments of inertia: (kilograms * square meters)
     45Taken at the center of mass and aligned with the output coordinate system.
     46 || Lxx = 0.0006986 || Lxy = 2.7577e-007 || Lxz = -7.8138e-007
     47 || Lyx = 2.7577e-007 || Lyy = 0.00050354 || Lyz = -6.44e-005
     48 || Lzx = -7.8138e-007 || Lzy = -6.44e-005 || Lzz = 0.00062253
     49
     50Moments of inertia: (kilograms * square meters)
     51Taken at the output coordinate system.
     52 || Ixx = 0.001556 || Ixy = 1.4013e-007 || Ixz = 3.5309e-007
     53 || Iyx = 1.4013e-007 || Iyy = 0.0013488 || Iyz = -0.00016547
     54 || Izx = 3.5309e-007 || Izy = -0.00016547 || Izz = 0.00063461
     55
     56== Mass Properties for Frame W (hand base frame) without palm pad ==
     57
     58[[Image(HandFrameW_NOPP_NoDialog_crop.jpg)]]
     59
     60Output coordinate System: Frame W (opaque)
     61
     62Mass = 0.59573 kilograms
     63
     64Volume = 0.00023933 cubic meters
     65
     66Surface area = 0.23262 square meters
     67
     68Center of mass: (meters)
     69 X = 5.1098e-005
     70 Y = -0.0050433
     71 Z = 0.036671
     72
     73Principal axes of inertia and principal moments of inertia: (kilograms * square meters)
     74Taken at the center of mass.
     75 || Ix = (0.0027331, 0.90166, -0.43244) || Px = 0.00045391
     76 || Iy = (0.01699, -0.43242, -0.90151) || Py = 0.00063852
     77 || Iz = (-0.99985, -0.0048831, -0.016501) || Pz = 0.00067156
     78
     79Moments of inertia: (kilograms * square meters)
     80Taken at the center of mass and aligned with the output coordinate system.
     81 || Lxx = 0.00067154 || Lxy = 2.9365e-007 || Lxz = -7.6321e-007
     82 || Lyx = 2.9365e-007 || Lyy = 0.00048844 || Lyz = -7.1984e-005
     83 || Lzx = -7.6321e-007 || Lzy = -7.1984e-005 || Lzz = 0.00060401
     84
     85Moments of inertia: (kilograms * square meters)
     86Taken at the output coordinate system.
     87 || Ixx = 0.0014878 || Ixy = 1.4013e-007 || Ixz = 3.5309e-007
     88 || Iyx = 1.4013e-007 || Iyy = 0.0012896 || Iyz = -0.00018216
     89 || Izx = 3.5309e-007 || Izy = -0.00018216 || Izz = 0.00061916
     90
     91
     92
     93== Mass Properties for Frame 1 (finger spread frame) ==
     94
     95[[Image(HandFrame1_NoDialog_crop.JPG)]]
     96
     97Output coordinate System: F1 (opaque)
     98
     99Mass = 0.14109 kilograms
     100
     101Volume = 3.919e-005 cubic meters
     102
     103Surface area = 0.058268 square meters
     104
     105Center of mass (meters):
     106 X = 0.030616 Y = -7.3219e-005 Z = -0.011201
     107 
     108Principal axes of inertia and principal moments of inertia (kilograms * square meters), taken at the center of mass:
     109 || Ix = (-0.99149, -0.0047957, -0.13013)  || Px = 1.9838e-005
     110 || Iy = (0.13011, 0.0033343, -0.99149)  || Py = 6.904e-005
     111 || Iz = (0.0051888, -0.99998, -0.0026819)  || Pz = 7.4106e-005
     112 
     113Moments of inertia (kilograms * square meters), taken at the center of mass and aligned with the output coordinate system:
     114 || Lxx = 2.0672e-005 || Lxy = 2.6024e-007 || Lxz = 6.3481e-006
     115 || Lyx = 2.6024e-007 || Lyy = 7.4105e-005 || Lyz = 1.7118e-008
     116 || Lzx = 6.3481e-006 || Lzy = 1.7118e-008 || Lzz = 6.8207e-005
     117 
     118Moments of inertia (kilograms * square meters), taken at the output coordinate system:
     119 || Ixx = 3.8374e-005 || Ixy = -5.604e-008 || Ixz = -4.2034e-005
     120 || Iyx = -5.604e-008 || Iyy = 0.00022405 || Iyz = 1.3283e-007
     121 || Izx = -4.2034e-005 || Izy = 1.3283e-007 || Izz = 0.00020045
     122
     123== Mass Properties for Frame 2 (finger inner link frame) without fingertip torque sensor ==
     124
     125[[Image(HandFrame2_NOSG_NoDialog_crop.JPG)]]
     126
     127Output coordinate System: F2_Origin
     128
     129Mass = 0.05832 kilograms
     130
     131Volume = 1.629e-005 cubic meters
     132
     133Surface area = 0.026068 square meters
     134
     135Center of mass (meters):
     136 X = 0.022042 Y = 0.00082603 Z = 0.0005526
     137
     138Principal axes of inertia and principal moments of inertia (kilograms * square meters), taken at the center of mass:
     139 || Ix = (-0.99971, -0.016746, 0.017324)  || Px = 4.7372e-006
     140 || Iy = (0.016611, -0.99983, -0.007873)  || Py = 4.1939e-005
     141 || Iz = (0.017453, -0.0075829, 0.99982)  || Pz = 4.3077e-005
     142
     143Moments of inertia (kilograms * square meters), taken at the center of mass and aligned with the output coordinate system:
     144 || Lxx = 4.7592e-006 || Lxy = 6.2295e-007 || Lxz = -6.6417e-007
     145 || Lyx = 6.2295e-007 || Lyy = 4.1929e-005 || Lyz = -2.1644e-009
     146 || Lzx = -6.6417e-007 || Lzy = -2.1644e-009 || Lzz = 4.3066e-005
     147
     148Moments of inertia (kilograms * square meters), taken at the output coordinate system:
     149 || Ixx = 4.8168e-006 || Ixy = 1.6848e-006 || Ixz = 4.6191e-008
     150 || Iyx = 1.6848e-006 || Iyy = 7.0281e-005 || Iyz = 2.4457e-008
     151 || Izx = 4.6191e-008 || Izy = 2.4457e-008 || Izz = 7.144e-005
     152
     153
     154== Mass Properties for Frame 2 (finger inner link frame) with fingertip torque sensor ==
     155
     156[[Image(HandFrame2_NoDialog_crop.JPG)]]
     157
     158Output coordinate System: F2_Origin
     159
     160Mass = 0.062139 kilograms
     161
     162Volume = 1.7634e-005 cubic meters
     163
     164Surface area = 0.028654 square meters
     165
     166Center of mass (meters):
     167 X = 0.023133 Y = 0.00078642 Z = 0.00052792
     168
     169Principal axes of inertia and principal moments of inertia (kilograms * square meters), taken at the center of mass:
     170 || Ix = (-0.99972, -0.015048, 0.018278)  || Px = 4.7942e-006
     171 || Iy = (0.014917, -0.99986, -0.0073066)  || Py = 4.3325e-005
     172 || Iz = (0.018386, -0.0070319, 0.99981)  || Pz = 4.4454e-005
     173
     174Moments of inertia (kilograms * square meters), taken at the center of mass and aligned with the output coordinate system:
     175 || Lxx = 4.8162e-006 || Lxy = 5.7981e-007 || Lxz = -7.2483e-007
     176 || Lyx = 5.7981e-007 || Lyy = 4.3317e-005 || Lyz = -2.6653e-009
     177 || Lzx = -7.2483e-007 || Lzy = -2.6653e-009 || Lzz = 4.4441e-005
     178
     179Moments of inertia (kilograms * square meters), taken at the output coordinate system:
     180 || Ixx = 4.872e-006 || Ixy = 1.7103e-006 || Ixz = 3.4041e-008
     181 || Iyx = 1.7103e-006 || Iyy = 7.6588e-005 || Iyz = 2.3133e-008
     182 || Izx = 3.4041e-008 || Izy = 2.3133e-008 || Izz = 7.7733e-005
     183
     184
     185== Mass Properties for Frame 3 (fingertip frame) without fingertip pressure pad ==
     186
     187[[Image(HandFrame3_NOPP_NoDialog_crop.JPG)]]
     188
     189Output coordinate System: F3 (opaque)
     190
     191Mass = 0.041377 kilograms
     192
     193Volume = 1.5627e-005 cubic meters
     194
     195Surface area = 0.019684 square meters
     196
     197Center of mass (meters):
     198 X = 0.022825 Y = 0.0010491 Z = 0.00042038
     199 
     200Principal axes of inertia and principal moments of inertia (kilograms * square meters), taken at the center of mass:
     201 || Ix = (-0.99921, -0.032055, 0.023536) || Px = 3.0842e-006
     202 || Iy = (0.023767, -0.0068431, 0.99969)  || Py = 1.568e-005
     203 || Iz = (-0.031884, 0.99946, 0.0075995)  || Pz = 1.6826e-005
     204 
     205Moments of inertia (kilograms * square meters), taken at the center of mass and aligned with the output coordinate system:
     206 || Lxx = 3.1053e-006 || Lxy = 4.3996e-007 || Lxz = -2.9595e-007
     207 || Lyx = 4.3996e-007 || Lyy = 1.6812e-005 || Lyz = -1.8205e-008
     208 || Lzx = -2.9595e-007 || Lzy = -1.8205e-008 || Lzz = 1.5673e-005
     209 
     210Moments of inertia (kilograms * square meters), taken at the output coordinate system:
     211 || Ixx = 3.1582e-006 || Ixy = 1.4308e-006 || Ixz = 1.0106e-007
     212 || Iyx = 1.4308e-006 || Iyy = 3.8376e-005 || Iyz = 0
     213 || Izx = 1.0106e-007 || Izy = 0 || Izz = 3.7275e-005
     214 
     215
     216== Mass Properties for Frame 3 (fingertip frame) with fingertip pressure pad ==
     217
     218[[Image(HandFrame3_NoDialog_crop.JPG)]]
     219
     220Output coordinate System: F3 (opaque)
     221
     222Mass = 0.04166 kilograms
     223
     224Volume = 1.5911e-005 cubic meters
     225
     226Surface area = 0.02168 square meters
     227
     228Center of mass (meters):
     229 X = 0.02295 Y = 0.0010739 Z = 0.00041752
     230 
     231Principal axes of inertia and principal moments of inertia (kilograms * square meters), taken at the center of mass:
     232 || Ix = (-0.99919, -0.032581, 0.023483)  || Px = 3.0982e-006
     233 || Iy = (0.023724, -0.0070039, 0.99969)  || Py = 1.5816e-005
     234 || Iz = (-0.032406, 0.99944, 0.0077712)  || Pz = 1.6962e-005
     235 
     236Moments of inertia (kilograms * square meters), taken at the center of mass and aligned with the output coordinate system:
     237 || Lxx = 3.1199e-006 || Lxy = 4.5115e-007 || Lxz = -2.9813e-007
     238 || Lyx = 4.5115e-007 || Lyy = 1.6948e-005 || Lyz = -1.8635e-008
     239 || Lzx = -2.9813e-007 || Lzy = -1.8635e-008 || Lzz = 1.5809e-005
     240 
     241Moments of inertia (kilograms * square meters), taken at the output coordinate system:
     242 || Ixx = 3.1752e-006 || Ixy = 1.4779e-006 || Ixz = 1.0106e-007
     243 || Iyx = 1.4779e-006 || Iyy = 3.8897e-005 || Iyz = 0
     244 || Izx = 1.0106e-007 || Izy = 0 || Izz = 3.78e-005