Trajectory tracing of the manipulator tip in work space is one of the important research areas. Accurately controlling robot movement along a predetermined trajectory is necessary for many applications like are welding and laser cutting. Several methods are developed for this purpose. In this study robot arms are first reduced into dynamically equivalent point masses and balanced to eliminate gravity terms from the dynamical equations and also decouple them. Simple PD control is used at each servomotor for position control. Positional and velocity feedback gain factors are computed for a second-order critically damped linear control model. Satisfactory results are obtained for tracing straight line trajectory defined in the work space of the manipulator. (C) 1997 Elsevier Science Ltd.