kin.generate.trajectory: Generate index and thumb trajectories accordind to Brenner...

In ccamp83/kinesis: R package for analyzing kinematic trajectories of reaching and grasping movements.

Generate index and thumb trajectories accordind to Brenner and Smeets' model (1998)

Description

Generate index and thumb trajectories accordind to Brenner and Smeets' model (1998)

Usage

kin.generate.trajectory(start, end, phi, ap, MT, r, index.only = F)

Arguments

start	a vector consisting of the x, y and z coordinates of the start position
end	a vector consisting of the x, y and z coordinates of the end position (target's geometrical center)
phi	final grip orientation (in radians). Must be 0 <= phi <= 3/4*pi. In case the final end z coordinate is negative, phi is automatically changed in sign too (otherwise positive pi/2 would result in the index reaching closer than the thumb)
ap	approaching parameter, as in Brenner & Smeets (1998)
MT	movement time (in millisec)
r	radius of the target object
index.only	logical: should the index trajectory be computed alone? (TRUE for pointing/reaching simulation; FALSE for grasping simulation; default to FALSE)

Note

If phi = pi/2 it becomes pi/2+0.00001 to avoid an unknown bug in kin.SmoothAndDerive(). Since Brenner and Smeets' model assumes unconstrained path for each digit, when phi is > pi*.64 (pi*16/25) the index takes an internal trajectory with respect to the thumb.

Examples

libraries()
dig <- kin.generate.trajectory(start=c(200,-300,0), end=c(0,0,400), phi=pi/4, ap=1000, MT=1500, r=40)
ggplot() + geom_point(aes(indexXraw, indexZraw), data=dig, color='red') +
   geom_point(aes(thumbXraw, thumbZraw), data=dig, color='blue') + coord_fixed()
plot3d(dig[,c(1,3,2)], col='red', radius=4, type='s')
spheres3d(dig[,c(4,6,5)], col="blue", radius=4)

ccamp83/kinesis documentation built on July 4, 2025, 6:19 p.m.