For the Aibo robot, and for most standard robots, you will find the following motor device variables useful (replace device by the actual device name):
device.load : sets the torque power in a joint, between 0 (totaly loose) and 1 (rigid).
device.PGain : set the P gain of a joint in the associated PID.
device.IGain : set the I gain of a joint in the associated PID.
device.DGain : set the D gain of a joint in the associated PID.
You also have useful properties, which are not variables in a strict sense (properties are part of the language semantics), but you can read and set them:
device->rangemin : minimal value of the device
device->rangemax : maximal value of the device
device->delta : precision of the device,used in fuzzy tests
device->unit : unit of the device (for information only in URBI 1)
device->blend : the device blend mode (normal, mix, add, queue, discard, cancel)
device->info : some information about the device.
Note that the above properties are not properties of the device, but they are in fact properties of the device.val variable, since we still assume here that aliases are defined on the device name.