Seong Youb Chung

Motion planning of bimanual robot for assembly

This paper presents motion planning method for bimanual robot for bimanual assembly task. Bimanual robotic assembly is modeled at the task-level using contact states of workpieces and their transitions. The lower-level velocity commands of workpieces are automatically derived by solving optimization problem formulated with assembly constraints, position of the workpieces, and kinematics of manipulators. The motion requirements of workpieces are transformed to the motion command of the bimanual robot. A hierarchical coordination scheme for bimanual robot is also proposed to perform cooperative assembly motions. The proposed approach is evaluated with experiments on peg-in-hole assembly with an L-shaped peg.

Assembly approach for bimanual robots

Bimanual, or two-handed, robots can be useful for assembly tasks in unstructured environment where it is difficult to have fixtures. The assembly is planned at the task-level with assembly models using contact states and their transitions. The lower-level velocity commands are automatically derived from the task-level symbolic transitions by solving constrained optimization problem formulated with assembly constraints and positions of the workpieces. The proposed approach is evaluated with simulation of the peg-in-hole assembly with an L-shape peg, that ordinary position control scheme cannot complete

Generating a contact state graph of polyhedral objects for robotic application

Traditional methods require large computation to model a contact state graph of polyhedral objects for robotic application, and moreover they are heuristic. In this paper, we propose a framework to generate the contact state graph automatically. All faces of the polyhedral objects are triangulated. A sub-contact is defined as single contact between two polyhedral objects and a contact state is presented with a set of the sub-contacts. There are two sub-contacts, a vertex-triangle contact and an edge-edge contact. According to convexity or concavity of the edges composing the triangle, the vertex-triangle contact and the edge-edge contact are classified into 10 types and 7 types, respectively. A contact state graph is made by evolutionary transitions of the sub-contacts. This procedure is accomplished only using the topology of the sub-contacts, which is possible in real-time. The proposed framework is evaluated by an example of square peg-in-hole assembly.

A framework for automatic generation of a contact state graph for robotic assembly

Dynamic manipulation of an active object is introduced as a general model of hopping and juggling tasks. In this setting, juggling and hopping are two extreme cases of this general model. Behavioral resemblance of these two tasks is afterwards extended to a detailed mathematical analogy between them. Then the analogy is exploited to develop a unified and abstract planning framework for juggling and hopping. To this end, dynamic manipulation of an active object is decomposed into three distinct phases and two transitions: Carry I, Free flight and Carry II phases. These phases are analogous to Lift off, Free flight and Touch down in hopping. In the next step, a mathematical model for each phase is developed. It is shown that dynamic grasp (in Carry phases of juggling) and foot stability (in Support phases of hopping) conditions share similar sets of dynamic equations. Accordingly, Lift off/Release and Touch down/Catch conditions in hopping/juggling are derived. It is shown that analogous strategies can be developed for Lift off and Release. The analogy is held for Touch down and Catch conditions as well. It is discussed that in the planning framework the initial and the goal configurations of the three phases are set in a model-based and forward manner. To do so, Touch down/Landing time, Free flight duration and robot/object maneuvers during Free flight are used as free parameters for planning in order to ensure foot stability in hopping and dynamic grasp in juggling along with other constraints.

Multi-agent-based scheduling methods for hybrid cellular production lines in semiconductor industry

This article addresses scheduling problems for the hybrid cellular production lines in the semiconductor industry, in which the hybrid cellular production line is defined as the production system composed of both single-functional and multi-functional cellular layouts. Detailed system configuration and material flow of a hybrid cellular production line are presented, and then, the scheduling problems in the hybrid cellular production line are separated into an inter-cell scheduling problem and intra-cell scheduling problems. A multi-agent-based scheduling method is proposed for the inter-cell scheduling problem, and a real-time heuristic scheduling method is proposed for the intra-cell scheduling problem. In the simulation experiments, various scenarios have been compared under the proposed inter-cell and intra-cell scheduling methods with the hybrid cellular production line composed of six cells.

Motion Planning of Bimanual Robot Using Adaptive Model of Assembly

This paper presents a motion planning method for a bimanual robot for executing assembly tasks. The method employs an adaptive modeling which can automatically generate an assembly model and modify the model during actual assembly. Bimanual robotic assembly is modeled at the task-level using contact states of workpieces and their transitions. The lower-level velocity commands of the workpieces are automatically derived by solving optimization problem formulated with assembly constraints, position of the workpieces, and kinematics of manipulators. Motion requirements of the workpieces are transformed to motion commands of the bimanual robot. The proposed approach is evaluated with experiments on peg-in-hole assembly with an L-shaped peg.

Registration between robot and workpiece in virtual environment for off-line programming

Robot has been widely used for industrial application in the flexible manufacturing system. The time-consuming teaching process by skilled engineers is inevitable to teach real robot manipulators for generating the robot program and recording locations which the robot should follow for the given task. The off-line programming (OLP) method is proposed to generate the robot program from CAD format data without the teaching process. It needs a registration process to find the translational and rotational relations between the reference frame of real robot and the reference frame in CAD format data. This paper presents the simple registration method between real robot and workpiece in virtual environment. Also a method to assign position and orientation of TCP (Tool Center Point) in real robot is presented when the target point is selected in the virtual environment by the user. The proposed methods are evaluated by the simulation with the commercial industrial robot for placing tool on the surface of the workpiece which is given in STL format data.

A motion planning method using triangulation of polyhedral objects for robotic assembly

We propose a method to plan assembly motion of an object from a planned contact sequence which consists of vertex-triangle contact and edge-edge contact, where faces of polyhedral objects are triangulated. The distance functions are determined according to contact situation of a vertex-triangle contact or an edge-edge contact in order to approach the next contact state while maintaining the current contact and avoiding collisions. The triangulation enables reduction of search range for determining the distance functions. The motion of an object is optimized using differential distance functions until reaching the next contact state. We show through simulations of two assembly tasks that the proposed method can simply determine distance functions and plan the assembly motion.

Adaptive Modeling of Robotic Assembly Using Augmented Petri Nets

Robotic assembly process is modeled as a discrete event dynamic system using contact states of the workpieces and their transitions. The goal assembly state is obtained by changing the contact states. A primitive contact is defined as a relation between a vertex and an edge of two workpieces. An augmented Petri net is presented as a framework to model, plan, and control the assembly process. The augmented Petri-net assembly model is automatically built and modified on-line during the actual assembly to handle un-modeled and infeasible contact situations. Reachability graph of the assembly model is used to find sequence from the augmented Petri net model, by the weights of the arcs. The proposed method is evaluated by simulation with L-shaped peg-in-hole assembly.