A distributed nonlinear control strategy for two-flexible-link manipulators is presented to track a desired trajectory in the robot’s workspace. The inverse dynamics problem is solved by transforming the desired trajectory from the workspace to the joint space using an intermediate space, called virtual space, and then using the quasi-static approach. To solve the nonminimum phase problem, an output redefinition technique is used. This output consists of the motor’s angle augmented with a weighted value of the link’s extremity. The distributed control strategy consists in controlling the last link by assuming that the first link is stable and follows its desired trajectories. The control law is developed to stabilize the error dynamics and to guarantee bounded internal dynamics such that the new output is as close as possible to the tip. The weighted parameter defining the noncollocated output is then selected. The same procedure is applied to control and stabilize the first link. The asymptotical stability is proved using Lyapunov theory. This algorithm is applied to a two-flexible-link manipulator in the horizontal plane, and simulations showed a good tracking of the desired trajectory in the workspace. 1. Introduction Many control strategies for manipulators have been the focus of several studies in recent years. The robot manipulators consist of a sequence of links and joints in various combinations. In industrial applications, most of the existing manipulators use rigid links and joints and are known as rigid manipulators. Rigid manipulators are generally slow, extremely rigid, and massive, and the useful load is very low compared to their weight. To improve the performance of the robot manipulators, their links must be lighter, and therefore they become more flexible. Flexible manipulators present more advantages when compared to rigid manipulators: they are faster and less massive and consume less energy. Some flexible manipulators are used in different areas, for example, the aerospace applications [1] and medical applications [2]. For flexible manipulators, the problem of workspace tracking trajectory is less covered so far than that of joint space tracking. There are few solutions to the workspace tracking problem, particularly for manipulators with many flexible links. The workspace tracking trajectory is very important since most of the tasks are defined in the operational space, such as painting, welding, and assembly. The flexible link manipulators are a nonminimum phase system when controlling the position of the end effector [3]. Unlike
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