A model based on a Petri net (PN) is proposed for controlling flexible manufacturing systems (FMSs). The model can describe not only normal sequential processes but also interruptive exceptional handling processes by means of simple structures. A layered structure and two types of token are introduced into a PN to describe exception handling and error recovery. An application in which this model was used to program a programmable logic controller (PLC) is described. The description of cell control can be simplified by the model.>

The authors propose and analyze a method for position-based compliance control with position gain control. It is shown that, for a stiff manipulator, the stable regions of desired compliance are extended by adjusting the internal position feedback gain to a level suitable to the desired compliance. The stable regions in an infinitely stiff environment for various position feedback gains are also described. This position-gain control method was implemented in a compliance-controller consisting of a few microprocessors and a 2-MFLOPS (million floating-point operations per second) floating-point processor. It can control the compliance of an industrial manipulator with six degrees of freedom at a frequency of 500 Hz. As a result of an experiment in which the manipulator under the compliance control was in contact with an infinitely stiff object, it was confirmed that the motion of the manipulator was stable when the compliance parameters were within the theoretically stable region.>

To represent compliant motion, the authors present a theory for specifying and generating the motion path of a robot in contact with the environment. Included is a formulation for specifying single contact motion, in which only one geometric feature (a vertex, an edge, or a plant) or a robot and one geometric feature of the environment participate. Single contact motion is categorized into four types according to the combinations of the movabilities of the contact positions on the robot and the environment. For each type of single contact motion, an interpolating transformation is assigned to generate motion from the path specification. In addition, motion constraints are provided according to combinations of geometric features. A geometric model of the task environment allows the formulation to be applied to automatic path generation in programming motion segments.>