Haptic sensation delivered to doctor's hands during CT-guided needle intervention complements insufficient visual information. Exploitation of the haptic information is to be trained using simulation. A model is necessary to compute the reflective forces occurring when the needle tip contacts with layers of soft tissues such as skin, membrane, and other layers of tissues. This paper proposes a nonlinear viscoelastic model based on measurements using porcine soft tissues. A 6-axis force-torque sensor and a needle are attached to the end of a 6-DOF articulated robot to measure the layer forces. The measurement results show that the layer forces increase nonlinearly with displacement of the needle. The force is affected by change of the velocity. It is also shown that the reflective force is relaxed when the needle stops. A standard linear solid model which can describe the relaxation phenomena is modified to describe nonlinear damping and stiffness forces. Accuracy of the developed model is verified through comparison between the model and measured data using porcine tissues. The proposed model can describe the nonlinear stiffness and relaxation phenomena with relative error less than 3.8 %.

ABSTRACT This paper proposes a novel method for a real‐time cutting simulation of deformable objects using meshless method. The method utilizes a rapid refinement of topological relations among the simulation nodes of meshless deformable objects. Topological relations are defined as an undirected graph based on a visibility criterion. The graph connects the adjacent nodes that lie within a support of each node. The topological relations are refined by removing the edges of the graph that is intersected by the cut surface during the cutting simulation. Our approach utilizes a bounding volume hierarchy (BVH) to accelerate the computation of the intersection test. The BVH reconstruction algorithm is proposed to account for the cases where pieces of the object are completely cut out from the object. Algorithms to examine the connectivity among simulation nodes and accordingly reconstructing the BVH using two‐level BVH are presented. The proposed approach achieves real‐time cutting simulation of deformable objects through the rapid refinement of the topological relation. In addition, the computational performance of the cutting procedure is preserved during the entire simulation, thanks to the real‐time reconstruction of the BVH. Copyright © 2012 John Wiley & Sons, Ltd.

This paper presents a method of self-intersection detection and resolution for dynamic cylindrical-lattice-based free-form deformation (FFD). The lattice-based approach allows efficient computation of deformation of complex geometries. But excessive deformation can cause visual anomalies such as surface infiltration and distortion. This paper derives a geometrically intuitive sufficient condition to guarantee that the FFD function is a homeomorphism and there is no self-intersection. The FFD function is defined by linear and quadratic B-Spline functions with the control points of the cylindrical lattice cell. The sufficient condition is satisfied if each trilinear function of the nine prism-shaped pentahedrons derived from the cell has a positive Jacobian determinant. The positivity is satisfied if the 12 tetrahedrons derived from the pentahedron have positive volumes. Based on the sufficient condition, the proposed method converts the self-intersection problem into a point-face collision detection and response problem suitable for dynamic simulation. The efficiency and accuracy of the self-intersection detection algorithm is analyzed and compared with a previous method. The results show that the proposed technique allows simulation of excessive deformation of tubular objects in an efficient and realistic manner.

This paper focuses on psychophysical evaluation of the control scheme developed to optimize the kinesthetic perception during the scaled teleoperation. The control problem is formulated as a multi-objective constrained optimization. The objective function is a metric which quantifies the detection and discrimination capacity of the human operator. The constraints are position tracking accuracy and absolute stability of the scaled teleoperation. Two popular control architectures, i.e., the position-position and the force-position control architectures are considered in this paper. The method of limits is employed in this paper to conduct the psychophysical experiments and evaluation. Results show that the developed control scheme is more effective in increasing the detection and discrimination capacity of human subjects as compared to the traditional transparency-optimized control laws.

This paper presents a control design framework for robust teleoperation. The teleoperation system with uncertainties is modeled as a linear parameter varying plant to employ the gain-scheduling control framework. The time-varying transmission delay, disturbances, and uncertainty of the environment are considered in the design of the control. The usual assumption that the human operator and the environment are passive is not made in this method. The control scheme employs an online estimation of the environment including disturbance and transmission time delay between master and slave. Simulation results show that position and force tracking errors are small, and the system shows stable behavior in spite of the uncertainties. A transparency analysis in the frequency domain shows that the developed control scheme guarantees perfect transparency in the low frequencies.

This paper presents an improved haptic interface for the Korea Advanced Institute of Science and Technology Ewha Colonoscopy Simulator II. The haptic interface enables the distal portion of the colonoscope to be freely bent while guaranteeing sufficient workspace and reflective forces for colonoscopy simulation. Its force-torque sensor measures the profiles of the user. Manipulation of the colonoscope tip is monitored by four deflection sensors and triggers computations to render accurate graphic images corresponding to the rotation of the angle knob. Tack sensors are attached to the valve-actuation buttons of the colonoscope to simulate air injection or suction as well as the corresponding deformation of the colon. A survey study for face validation was conducted, and the result shows that the developed haptic interface provides realistic haptic feedback for colonoscopy simulations.

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.

This paper presents an output-estimation method with reduced multirate sampling for real-time multi-input-multi-output (MIMO) haptic rendering. Haptic systems employ physics-based deformation models such as finite-element models and mass-spring models. These physics-based deformation models for high fidelity have to deal with complex geometries, material properties, and realistic behavior of virtual objects. This incurs heavy computational burden and time delays so that the reflective force often cannot be computed at 1 kHz which is a safe frequency for stability of the haptic systems. Lower update rates of the haptic loop and the computational time delay also deteriorate the realism of the haptic system. This problem is resolved by the proposed MIMO output-estimation method. The haptic system is designed to have two sampling times, T and JT, for the haptic loop and the graphic loop, respectively. Dynamics of the physics-based deformation is captured in a discrete and deterministic input-output model. The MIMO output estimation method is developed drawing on a least-squares algorithm and an output-error estimation model. The P-matrix resetting algorithm is also designed to deal with the changing input-output relationship of the deformation model. The parameters of the discrete input-output model are adjusted online. Intersample outputs are computed from the estimated input-output model at a high rate, and traces the correct output computed from the deformation model. This method enables graphics rendering at a lower update rate, and haptic rendering at a higher update rate. Convergence of the proposed method is proved, and performance is demonstrated through simulation with both a linear tensor-mass and a linear mass-spring models.

This paper presents MIMO output estimation with reduced multirate sampling for real-time haptic rendering. The graphic models of the haptic systems are required to deal with complex geometries, material properties, and the dynamics of the virtual objects to display realistic deformation. Accurate graphic models often incur heavy computational burden, and the reflective force cannot be computed at 1 kHz. This problem is resolved by employing a multirate output estimation method. The dynamics of the graphic model is represented by a discrete input-output model. The parameters of the discrete input-output model are estimated on-line by the proposed multirate output estimation algorithm. The reflective force is computed from the estimated input-output model at a high rate, and traces the force computed from the graphic model as the estimation error quickly approaches zero. The convergence of the proposed estimation algorithm is proved, and the performance is evaluated with simulation

Bimanual robotic assembly is modeled at the task-level using contact states of workpieces and their transitions. Task-compatibility-based motion planning is developed to derive the lower-level velocity commands from the task-level symbolic transitions of the bimanual assembly model. The cost-function based on the manipulability and compatibility is designed to determine the assembly motions of the two manipulators. The assembly motions are executed along the direction of maximizing the sum of the performance indices to improve the control performance of the two manipulators. The problem is formulated as a constrained optimization considering the assembly constraints, position of the workpieces, and the kinematics and redundancy of the bimanual robot. The proposed approach is evaluated with 2D simulation of a peg-in-hole assembly with an L-shaped peg and two 3-dof manipulators.

This paper presents a model of frictional contact with soft tissue for the colonoscopy simulator with haptic fidelity. The colonoscopy simulator allows the user to navigate the three dimensional virtual colon constructed from CT (computer tomography) data of patients. The frictional contact model is proposed to integrate the therapeutic procedures such as polyp removal. The proposed model uses the finite element method based on the linear static elasticity to simulate deformation and reflective force including friction effects. The variation of the reflective force is computed according to the contact state, stick or slip state, during sliding contact motions. Simulation results show responses following the Coulomb's friction law.

Uncertainties are inevitable in robotic assembly in unstructured environment since it is difficult to construct fixtures to guide motions of robots. This study proposes an augmented Petri net to model and control assembly tasks in unstructured environment. Conditions and costs of state changes can be simply computed from the output functions of the Petri net model. An algorithm is also proposed to adapt the model on-line. The model constructed by the algorithm is more compact and efficient than an off-line model since its states and events are dynamically modified on-line. The proposed method is evaluated by experiments with L-type peg-in-hole assembly using a two-arm robot system.

This paper considers the stability of haptic interface that interacts with rigid virtual objects. Human arm is characterized with a linear time-invariant second-order impedance model, and a response model to the simulated force. Nonlinear virtual coupling is designed based on the human response model. This provides with less conservative constraint for the design of the stable haptic interface.

This paper considers the problem of on-line scheduling of robotic cells with post-processing residency constraints. We model this scheduling problem with temporal constraints using Dechter, Meiri, and Pearl's formalism. Then, we present an on-line scheduling algorithm with polynomial computational complexity. The on-line scheduling algorithm consists of FEASIBLE/spl I.bar/SCHED/spl I.bar/SPACE and OPTIMAL/spl I.bar/SCHED. The former finds feasible solution space for a newly inserted part, which guarantees both logical and temporal correctness. The latter computes the optimal solution in the feasible solution space obtained previously. The objective of the scheduling is to minimize the completion time of the last operation of the part. We prove that each procedure has polynomial complexity.

This paper presents an efficient approach to real-time scheduling of integrated equipment in semiconductor fabrication. To accomplish high level of automation and flexibility, the supervisory control system of an integrated equipment should comprehend the management of machine failures and deadlock while optimizing equipment utilization. This paper proposes a real-time scheduling approach that can perform scheduling and deadlock management in an efficient way in spite of machine failures. First, we present a novel framework where we decompose deadlock management problem into sub-problems for computational efficiency, and then integrate them with scheduling algorithms. To realize the proposed framework, a resource request matrix representation is introduced to identify deadlock-prone modules, and to apply deadlock management algorithms. We also present algorithms of polynomial complexity to identify deadlock-prone modules, and algorithms to manage deadlock considering machine failures.

This paper presents the KAIST interactive bicycle racing simulator system, which consists of a pair of bicycle simulators. The rider on the racing simulator experiences realistic sensations of motion, while being able to see the other bicycle simulator and having the audio-visual experience of riding in a velodrome or on the KAIST campus. The 2nd bicycle of the racing simulator system consists of a bicycle, a 4-DOF platform, a handlebar and a pedal resistance system to generate motion feelings; a real-time visual simulator a HMD and beam projection system; and a 3D sound system. The system has an integrating control network with an AOIM (Area Of Interest Management) based network structure for multiple simulators.

This paper presents key technologies and system integration issues of the KAIST interactive bicycle simulator. The rider on the bicycle feels the motion and has the visual experience as if he/she is riding in the campus of the Korea Advanced Institute of Science and Technology. The simulator consists of a bicycle, a Stewart platform, a magnetorheological handle, a pedal resistance system to generate motion feelings, a real-time visual simulator and projection system, sub-controllers and an integrating control network.

Addresses an efficient method to identify the process modules that can potentially cause deadlock in semiconductor track systems. Track systems carry out important functions in the photolithography process of semiconductor fabrication. Trends toward high automation and flexibility in the track systems accelerate the necessity of the intelligent controller that can guarantee deadlock-free operation of the track systems. However, there is a limitation when applying a deadlock avoidance policy in real-time due to the computational complexity caused by scores of modules, and complex and flexible process flows. To cope with that problem, the paper proposes an efficient method to identify potential deadlock process modules by introducing the concept of a potential deadlock set. The potential deadlock set is defined as the set of resources or modules that can result in deadlock in near future. Once the potential deadlock set is identified in the track system, a deadlock avoidance policy can be applied only to the process modules included in the potential deadlock set. Therefore, the approach using the potential deadlock set can significantly reduce the computational complexity when applying deadlock avoidance policy. A resource request matrix and a genetic algorithm are used to find the potential deadlock set in the track systems.

Presents a simulator of track systems in semiconductor fabrication. A track system is a clustered set of equipment for photolithographic processes with complex and diverse process flows, and its layout can be changed according to the production demand. Simulation is required to evaluate the performance of proposed track systems and their control policies. We have developed a virtual 3D dynamic simulator of track systems, which consists of four modules, viz. a simulation module, a scheduling module, a performance analysis module and a graphical user interface (GUI) module. The simulation module is constructed using a commercial discrete event system simulation software package called AutoMod. The scheduling module includes dispatching rules and input release rules. Users enter track parameters and empirical data via the GUI module. Based on the simulations, users can select the best-performing scheduling rule for the targeted track systems and reconfigure the layout. Users can also easily grasp the entire situation through such virtual 3D simulations.

This paper addresses a deadlock-free scheduling method for track systems in semiconductor fabrication. A track system is clustered equipment performing the photolithography process in semiconductor fabrication. Trends toward high automation and flexibility in the track systems accelerate the necessity of the intelligent scheduler that can guarantee reliability and optimize productivity of the track systems. We propose an efficient deadlock-free scheduling method that can avoid deadlock inherent to track systems and optimize the productivity. We employ two procedures for the deadlock-free scheduling. First, we define the potential deadlock set and deadlock-safe set to apply the deadlock avoidance policy efficiently. After introducing the potential deadlock set and the deadlock-safe set we propose a deadlock avoidance policy using an online Gantt chart, which can generate optimal or near-optimal schedules without deadlock. The proposed deadlock-free scheduling method is shown to be efficient in handling deadlock inherent to the track systems through simulation.

This paper presents a high-level design approach to cooperative control of multiple mobile robots with local sensors. The method consists of two stages. In the first stage, we design global control plans for multiple robots, which include task allocation and task change plans to complete the goal. In the second stage, we design control logic and error recovery methods for an individual robot. Sensor information is integrated by merging similar sensor states together using AND or OR logic. Unique control commands are generated by eliminating logical conflicts using transition firing sequences in the Petri net models. Errors are recovered by changing control commands dynamically using reference and control models. To demonstrate the effectiveness of the proposed method, an object-searching task is evaluated. This task is to search an object such as a box using two robots, and consists of two sub-tasks, i.e., a wall-tracking task and a robot-tracking task. Simulation results of the object-searching task, the wall-tracking task, and the error recovery are presented.

This paper presents a new method for scheduling cluster tools in semiconductor fabrication. A cluster tool consists of a group of single-wafer chambers organized around a wafer transport device, or robot. The cluster fabrication considered consists of serial cluster tools. Due to constraints imposed by multiple routes of each type of wafer and machines with no buffer, it is very difficult to find an optimal or near-optimal schedule. The proposed method uses a job requirement table with random keys as a solution representation, and simulated annealing to find an optimal or near-optimal schedule. To determine which operation can be scheduled, a candidate list is used. To show the effectiveness of the proposed method, a scheduling example of cluster fabrication is presented. From the experimental results, it is shown that the proposed method is promising.

A scheduling method that uses Petri net modeling and heuristic search is extended to handle the tool setup. The machine setup is to attach a tool to a particular machine and detach the tool from the machine, and this is a time-consuming activity. The processing time of operations varies according to the attached tool and the machine used. The method proposed in this paper uses timed-transition Petri net to model these features and applies a search algorithm to the reachability of the Petri net model to generate an optimal or near-optimal schedule. In addition, this method can determine how many tools are needed in order to reduce the makespan. Search algorithm employs an evaluation function to guide the search procedure. New heuristic functions are developed for efficient search. The experimental results that show the effectiveness of the proposed method are presented.

Petri net modeling combined with heuristic search provides a new scheduling method for flexible manufacturing systems. The method formulates a scheduling problem with a Petri net model. Then, it generates and searches a partial reachability graph to find an optimal or near optimal feasible schedule in terms of the firing sequence of the transitions of the Petri net model. The method can handle features such as routing flexibility, shared resources, lot sizes and concurrency. By following the generated schedule, potential deadlocks in the Petri net model and the system can be avoided. Hence the analytical overhead to guarantee the liveness of the model and the system is eliminated. Some heuristic functions for efficient search are explored and the experimental results are presented.>

In industrial applications, the quantity of error recovery codes far exceeds that required for supervisory control. Declarative programming techniques can be integrated with the traditional procedural control to reduce the efforts in developing error recovery codes and to provide flexibility for future modifications as new error types are encountered. A flexible control system that employs reasoning for both control and error recovery should distribute its functions among hierarchical levels. A symbolic level for task level control and error recovery reasoning is composed of a system model, an assembly plan and a reasoning system. A device level includes all the devices and modular control programs. A robotic assembly of a gear plate is presented as an example application of the intelligent error recovery system. The results from two implemented versions of the example application show that incremental revisions to such a system can be made easily and cost effectively, but the system requires a relatively large initial declarative programming investment.>

A method for scheduling of flexible manufacturing systems by merging Petri net modeling and heuristic search is presented. The method uses the Petri net model to generate and search a partial reachability graph, and presents an optimal or near-optimal schedule in terms of a firing sequence of transitions of the Petri net model of the system. This method can easily handle routing flexibility and shared resources. Taking this approach also relieves the analytical burden since it becomes less urgent to analyze the large net to guarantee freedom from deadlock, or liveliness once an optimal schedule is developed. Some heuristic functions to guide the search are explored, and preliminary results and the search algorithm are presented.>