Stiffness
Stiffness On
When NAO is switched on, he initially has zero stiffness. When at zero stiffness, you can send any commands to the motors, but he will not move.
To give power to the motors, you can call one of Motion's stiffness methods:
# Example showing how to interpolate to maximum stiffness in 1 second names = 'Body' stiffness = 1.0 time = 1.0 proxy.stiffnessInterpolation(names, stiffness, time)
When changing stiffness away from zero, it is best to do it gently so as to reduce the chance of a judder when powering up the motors.
Many tasks can be achieved at less than maximum stiffness (stiffness = 0.6), but tasks such as "Get up" require all the power they can get (stiffness = 1.0).
Stiffness Off
When you reduce the stiffness to zero, you cut all the power to the motors, so you should be careful that NAO is in a self-stable pose, otherwise he could fall.
# Example showing how to interpolate to minimum stiffness in 1 second names = 'Body' stiffness = 0.0 time = 1.0 proxy.stiffnessInterpolation(names, stiffness, time)
Stiffness Trajectories
Should you wish to vary the stiffness of a joint over time, you can request a 'trajectory' of stiffness.
# Example showing a stiffness trajectory # Here the stiffness of the HeadYaw Joint, rises to # 0.8, then goes back to zero. pNames = "HeadYaw" pStiffnessLists = [0.0, 0.8, 0.0] pTimeLists = [0.5, 1.0, 1.5] proxy.stiffnessInterpolation(pNames, pStiffnessLists, pTimeLists)
Like angle interpolation commands, multiple trajectories can be specified in the same command.
# Example showing multiple stiffness trajectories # Here the stiffness of the HeadYaw Joint, rises to # 0.5, then goes back to zero, while the HeadPitch # joint rises to 1.0 pNames = ["HeadYaw","HeadPitch"] pStiffnessLists = [[0.0, 0.5, 0.0],[0.0, 1.0, 0.0]] pTimeLists = [[0.5, 1.0, 1.5],[0.5, 1.0, 1.5]] proxy.stiffnessInterpolation(pNames, pStiffnessLists, pTimeLists)