Just-in-time control method for a free-joint manipulator

The present paper proposes a just-in-time (JIT) control method for a free-joint manipulator moving in a horizontal plane. The manipulator consists of two links, where only the first link at the base is driven and the second link has a passive joint. Although it is difficult to control the manipulator by conventional methods, a human can operate the manipulator at a certain level. The input of a human operator is observed and is regarded as a rectangular signal. The control input is then represented in terms of the parameters of the rectangular signal. The database for the proposed JIT control system is constructed using these input parameters. Experimental and simulation results reveal that, by using the proposed control method, both of these links successfully reach the target angles. However, the control method is only useful when the target angle for the free link is relatively small. The simulation results reveal that the performance of the control method depends on the target angle and on the parameters of the manipulator. The reason for this dependency is discussed based on the distribution of the database. The discussion suggests that the performance may be improved by modifying the database such that data will be distributed throughout the range of the target position.