1. Field of the Invention
The present invention relates to a control device adapted for performing flexible control of robot.
2. Description of the Related Art
There is performed a flexible control adapted for realizing flexibility of force exerted between tools of a robot and a workpiece in a direction defined by the tool coordinate system having a predetermined positional attitude relationship with respect to the mechanical interface or the end effector of the robot, or the task coordinate system having a predetermined positional attitude relationship with respect to the robot base coordinate system.
Such a flexible control is disclosed in the Japanese Patent Application Laid Open No. 2010-253676, the Japanese Patent Publication No. 3681431, the Japanese Patent Publication No. 3283650 and the Japanese Patent Application Laid Open No. 5-158514, for example. Further, in the Japanese Patent Application Laid Open No. 2004-148466, it is disclosed that parameter sets are switched at the time of executing the flexible control.
As a main use purpose of a flexible control on the orthogonal coordinate of the robot, die-cast taking-out working may be exemplified. The die-cast taking-out working is a working to hold a workpiece in a metal mold of a die-cast machine by means of an end effector of the robot thereafter to extrude the workpiece from the metal mold by using cylinder, or the like, on the die-cast machine side. In the die-cast taking-out working, the robot operates, in correspondence with the operation and the force, by which the workpiece is extruded, by making use of flexible control on the orthogonal coordinate. In other words, the robot performs “following operation”. The Japanese Patent Publication No. 4051526 discloses a flexible control synchronous with such extrusion working.
In the prior art, first a control device capable of storing a plurality of parameter sets indicating flexibility is prepared. Further, as disclosed in the Japanese Patent Application Laid Open No. 2004-148466, the control device switches such parameter sets on the basis of signals from the side where the extruding operation performs. For example, there is prepared a program of robot to wait such a signal output during flexible control based on, e.g., the first parameter set, and to implement switching into the second parameter set on receiving such signal thus to perform the flexible control.
However, in this method, electric delay of signal and physical delay of the extruding operation are independent from each other. For this reason, there is a problem that it is difficult to precisely synchronize the switching work and the extruding work. Further, in this method, the parameter sets cannot be always switched at respective suitable timings. Accordingly, since the direction of the robot is limited also at the time of holding a workpiece, there are cases where variation in the dimension of the workpiece may not be absorbed. In addition, also at the time of extruding the workpiece by means of the cylinder, or the like, there are instances where the robot may follow in all directions so that the robot cannot go straight.
Moreover, when it is difficult to switch parameter sets on the basis of signal, there was prepared a single parameter set capable of complying, to a certain degree, with both the working for holding the workpiece and the extrusion working for extruding the workpiece by means of the end factor. However, in this case, there is a problem that the both performances of the workpiece holding working operation and the workpiece extruding working operation are inferior in comparison to the case where dedicated parameter sets are respectively prepared.
The present invention has been made in view of such circumstances, and has an object to provide a robot control device adapted to securely implement, without using any complicated peripheral equipment, a function to switch setup value in a following direction of the flexible control, i.e., parameter sets of flexibility strictly in synchronism with the extrusion working in order to switch the following direction at a suitable timing.