HAS-Motion Software Documentation

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modify_force_structure_parameters]] as follows. amti_steps2.jpg each structure is defined as a plane (or polygon) defined by four corners. if the force structure is not a single plane, but multiple planes, each surface should be defined in the force structure surfaces list box ==== modify_force_structure_parameters ==== **modify_force_structure_parameters** /used= number of force structures used ! /type= not currently used ! /num_fp_in= number of force platforms assigned to each force structure ! /fp_index= index number of each platform ! /num_surfaces_out= number of output surfaces for each force structure ! /speed_values= the speed of the surface of each structure (e.g. an instrumented treadmill) ! /speed_channels= analog channel number for the speed of each structure ! /speed_scales= scale factor for the analog channel ! /corner1= corner locations for each output surface ! /corner2= ! /corner3= ! /corner4= /use_forces_for_kinetics= are forces kinematics only? /combine_input_forces= combine all forces for each structure into a single force ! /[[visual3d:documentation:pipeline:file_commands:update_c3d_file|update_c3d_file]]=false **;** for example, the following force structure has one surface attached to two force platforms. forcestructuredlg1x2.jpg \\ **modify_force_structure_parameters** /used=2 /type=0+0 /num_fp_in=2+1 /fp_index=2+3+4 /num_surfaces_out=2+2 /speed_values=0+0 ! /speed_channels= ! /speed_scales= /corner1=1533.16+464.5+0+2038.16+464.5+355.6+1450+0.5+177.8+2017.84+0.5+533.4 /corner2=1533.16+0.5+0+2038.16+0.5+355.6+1450+464.5+177.8+2017.84+464.5+533.4 /corner3=1269+0.5+0+1774+0.5+355.6+1810+464.5+177.8+2282+464.5+533.4 /corner4=1269+464.5+0+1774+464.5+355.6+1810+0.5+177.8+2282+0.5+533.4 /use_forces_for_kinetics=true+true /combine_input_forces=true+false ! /update_c3d_file=false **;** see also [[visual3d:documentation:pipeline:force_commands:modify_force_structure_parameters|modify_force_structure_parameters]] ===== structure consisting of 1 force platform and 2 surfaces ===== the following dialog creates a force structure that is comprised of 2 surfaces attached to the same platform. amti_steps3.jpg visual3d creates two surfaces, so it creates two force signals. the signals appear in the data tree as: **fs1_1** and **fs1_2** which stands for force structure 1 surface 1 and force structure 1 surface 2. visual3d assigns the force computed from fp1 (in this case) to the surface that is intersected by the force. the surface is defined by the four sided polygon defined by the corners. the force assignments are included in the data tree. **cop_1**, **force_1** and **freemoment_1** forcestructuredatatree.jpg in the following figure the right foot makes contact with 2 steps forcestructuregraph.jpg ===== structure consisting of 2 force platforms and 1 surface ===== the following dialog creates a force structure that is comprised of 1 surface spanning 2 force platforms. forcestructuredig1x2.jpg the user has the option to treat each force independently, which means that each force fp1 and fp2 could be assigned to the same segment. the automatic gait events are search for segments that have been assigned a force, so if a foot steps on one platform at heel strike and a different platform at toe off, visual3d will create 1 heel strike and 1 toe off event even though there are two different forces being used. the inverse dynamics are computed correctly regardless of whether the two forces are combined into one force or left as two forces; visual3d keeps track of the bookkeeping for the user. the combined force is computed as follows: * transform the force, cop, and free moment of each force platform into the output polygon (force structure surface) coordinate system * solve the following 6 equations for the resultant force and moment forcestructureeqn1.jpg solve for the 3 components of the force forcestructureeqn2.jpg assume the resultant center of pressure lies on the output surface, and that the free moment is computed only about the normal to the surface * solve for the x and y component of the cop on the surface * solve for tz of the free moment * transform these values back into the laboratory coordinate system if there are two force platforms, the resulting signal will appear in the data tree as **fs1_1** and **fs1_2** this is interpreted as force structure 1 contribution from force platform 1, and force structure 1contribution from force platform 2. \\ if, for example, instead of fp1 and fp2, there was fp1 and fp3, the signals would be **fs1_1** and **fs1_3** \\ if the option to combine all input forces is selected, there will be one resulting signal **fs1_1** ===== curved surfaces ===== if the force structure is actually a continuous curved surface, it must be approximated by a series of contiguous surfaces. }}}}}}}}}}}}}}}}