Deals with a sawing task performed by two cooperating arms. The two-arm system under our hand consists of a four degree-of-freedom (DOF) SCARA robot and a five DOF PT200V robot. When the two arms are rigidly grasping a saw, the mobility of the system is three, which is not enough for sawing tasks. Therefore, we deliberately insert a passive joint at the end of the SCARA robot to increase the mobility up to four. A hybrid control method to regulate the force and velocity by the two arms is proposed in this work. The proposed scheme has three typical features; first, the two arms are treated as one arm in a kinematic viewpoint. Secondly, our approach is different from other acceleration-based approaches, in the sense that our hybrid control method is based on a Jacobian and an internal kinematics for a single closed-kinematic chain of the two arms to reflect the nature of the position-controlled industrial manipulator. Thirdly, the proposed scheme is not only able to operate the system even if a passive joint exists, but also is able to utilize the internal loads for useful applications such as pitch motion control. We experimentally show that the performance of the velocity and force response are satisfactory, and that one additional passive joint not only prevents the system from unwanted roll motion in the sawing task, but also allows an unwanted pitch motion to be notably reduced by an internal load control. To show the effectiveness of the proposed algorithms, we perform experimentation under several, different conditions for saw, such as three saw blades, two sawing speeds, and two vertical forces.

Concerns a sawing task by two cooperating arms. To follow a line in a horizontal plane, three directional motions must be controlled, 2 translational and 1 rotational. A certain level of force must be controlled in the vertical direction, to keep contact with the object to be sawn. The two-arm system consists of a 4-DOF SCARA robot and a 5-DOF PT200V robot. When the two arms are rigidly grasping a saw, the mobility of the system is 3, which is not enough. Therefore, we deliberately insert a passive joint at the end of the SCARA robot to increase the mobility to 4. A hybrid control method to regulate force and position is proposed. The proposed scheme has three typical features: First, the two arms are treated as one in a kinematic viewpoint. Second, the hybrid control method is based on a Jacobian and an internal kinematics for a single closed-kinematic chain of the two arms to reflect the nature of the position-controlled manipulator. Third, the proposed scheme is not only able to operate the system even if a passive joint exists, but also is able to utilize the internal loads for useful applications such as pitch motion control. We experimentally show that the performance of the position and force response are satisfactory, and that one additional passive joint not only prevents the system from unwanted roll motion in the sawing task, but also allows an unwanted pitch motion to be notably reduced.

This paper presents a design experience of a supervisory control system for coordination of multiple robotic devices. To effectively program job commands, a Petri net-type graphical robot language(PGRL) is proposed, where some functions for coordination among tasks such as concurrency and synchronization, can be easily programmed. Each task of PGRL is described by employing formal model languages, which are composed of three modules, sensory, data handling, and action module. It is expected that by using our proposed PGRL and formal model languages, one can efficiently describe a job or task, and hence can easily operate a complex real-time concurrent system. The proposed control system has been implemented by using VME-based 32-bit microprocessor boards and a real-time multitasking operating system (VxWorks), and is shown to successfully work for robotic jobs.

In this paper, a fuzzy force control algorithm is suggested for commercialized industrial robots equipped with the position servo drives, where control rules of the proposed fuzzy controller are changed according to the magnitude of environmental stiffness in such a way that good force response is maintained regardless of changes of environmental stiffness. Specifically, some fuzzy control rules are designed for several representative environmental stiffness values, and then a control action for a given arbitrary environmental stiffness value is decided by a fuzzy interpolation method. To show the validity of the proposed fuzzy controller, several experimental results are illustrated, where a 5-axis articulated robot manipulator equipped with the wrist force/torque sensor system and our prototype dual robot controller are employed.>