Complex sentence: Rotation of the drive wheel itself can provide control in only one dimension (i.e., forwards and backwards): control in other dimensions generally requires other actuators, such as auxiliary pendulums, reaction wheels, or control moment gyroscopes attached to the main unicycle pendulum.
Split into simpler sentences: Rotation of the drive wheel itself can provide control in only one dimension, forwards and backwards. Control in other dimensions generally requires other actuators, such as auxiliary pendulums, reaction wheels, or control moment gyroscopes attached to the main unicycle pendulum.