When I input 3 control quantities, why doesn't the model move in the direction of freedom? <body name="torso" pos="0 0 0"> <joint type="slide" name="slider1" pos="0 0 0" axis="1 0 0"/> <joint type="slide" name="slider2" pos="0 0 0" axis="0 1 0"/> <joint type="hinge" name="rot" pos="0 0 0" axis="0 0 1"/> <geom type="box" pos=".15 0 0.25" size="0.1 0.1 0.05"/> </body> -<actuator> <position joint="slider1" gear="100.0"/> <position joint="slider2" gear="100.0"/> <position joint="rot" gear="100.0"/> </actuator>