A modern system theory point of view is offered for the design of sequencing controllers for discrete event manufacturing systems, whereby the controller is considered as separate from the workcell. The controller has...
详细信息
A modern system theory point of view is offered for the design of sequencing controllers for discrete event manufacturing systems, whereby the controller is considered as separate from the workcell. The controller has a rule-based structure with inner loops where no shared-resource conflict resolution is required, and extra control inputs in an outer loop to resolve conflict and remove deadlock (where needed). The controller design is based on the required task sequence and the available resources; it is described by linear (i.e. matrix) and nonlinear logical equations. The controller-workcell interaction expressed both in qualitative and quantitative terms supports a rigorous analysis of conflicts and deadlock. Three methods for conflict and deadlock resolution related to current work are efficiently incorporated in the general design framework. The design algorithm naturally accommodates a performance analysis in terms of the (R,max,+) representation as a consequence of the link established between that approach and the rule-based controller equations. Compatibility with other analysis/design techniques is briefly addressed.
A matrix framework is developed for modelling the workcell dynamics and designing digital controllers. The workcell functions are seperated from the controller, in the contrast to the Petri-net model where the workcel...
详细信息
A matrix framework is developed for modelling the workcell dynamics and designing digital controllers. The workcell functions are seperated from the controller, in the contrast to the Petri-net model where the workcell and the controller functions are undifferentiated This framework unites the industrial engineering approaches with the petri-net formulations and opens perspecrives for the sample-data control of flexible manufacturing systems. An illustrative example gives an overview of the overall design procedure.
In this paper a three-step active deburring strategy is proposed based on force feedback control. Strategies for automatic contour following are developed to identify unknown workpiece contours, to automatically gener...
详细信息
In this paper a three-step active deburring strategy is proposed based on force feedback control. Strategies for automatic contour following are developed to identify unknown workpiece contours, to automatically generate desired robot motions, and to detect unknown burr sizes. Under the active deburring strategy burr size variations are identified through contour following and different sizes of burrs are removed with a specification of a variable desired deburring force. Implementation of and experiments with the proposed strategies are described.
This paper is concerned with introducing a genetic-based algorithm for the minimum-time trajectory planning of articulated robotic manipulators. The planning procedure is performed in the configuration space and respe...
详细信息
This paper is concerned with introducing a genetic-based algorithm for the minimum-time trajectory planning of articulated robotic manipulators. The planning procedure is performed in the configuration space and respects all physical constraints imposed on the manipulator design, including the limits on the torque values applied to the motor of each joint of the arm; consequently, the complete nonlinear dynamic robot model is incorporated in the formulation.< >
A new fuzzy reasoning is proposed so that the conclusion consists of a function of mean-values on each membership function in antecedent. It is then shown that the constant parameters in conclusion can be rationally d...
详细信息
A new fuzzy reasoning is proposed so that the conclusion consists of a function of mean-values on each membership function in antecedent. It is then shown that the constant parameters in conclusion can be rationally designed from the view point of a control theory, if the conclusion is regarded as a sliding controller with the mean values in antecedent as state variables.
control methods based on using the relative motion between the manipulator and the workpiece are described for controlling the force of a one-dimensional manipulator, in which it is assumed that there are no collision...
详细信息
control methods based on using the relative motion between the manipulator and the workpiece are described for controlling the force of a one-dimensional manipulator, in which it is assumed that there are no collisions between the manipulator and the workpiece and we use a computed force law which is similar to the computed torque law in the trajectory tracking problem of a manipulator. We consider two cases depending on whether the position and velocity of the workpiece (or end-effector) are available or not to calculate the computed force control. The effectiveness of the proposed control methods is illustrated by some computer simulations.
This paper presents the kinematic analysis and trajectory planning for a six-degrees-of-freedom end-effector whose design is based on the Stewart platform mechanism. The end-effector is composed of two platforms and s...
详细信息
This paper presents the kinematic analysis and trajectory planning for a six-degrees-of-freedom end-effector whose design is based on the Stewart platform mechanism. The end-effector is composed of two platforms and six linear actuators driven by stepper motors. A spring-loaded platform is used to provide passive compliance to the end-effector during a part assembly. A closed-form solution is derived for the inverse kinematic transformation and a computationally effective numerical solution is obtained for the forward kinematic transformation using the Newton-Raphson method. Three trajectory planning schemes, two for fine motion and one for gross motion are developed. Experimental results of tracking various test paths are presented.
The difficulties in devising reliable assembly strategies result from tlie complexity and the uncertainties of the assembly process and its environments such as imperfect knowledge of the parts being assembled as well...
详细信息
Tip position control of flexible arms with friction in the joints is studied in this paper. The control scheme is based on two nested loops: an inner loop to control the position of the motor and an outer loop that co...
详细信息
Tip position control of flexible arms with friction in the joints is studied in this paper. The control scheme is based on two nested loops: an inner loop to control the position of the motor and an outer loop that controls the tip position. The design of the inner loop is quite straightforward. However, the the outer loop may be designed several different ways. Three methods are proposed here to control the tip position: a feedforward based control method, a method that eliminates the principal natural frequency of the beam, and a method based on the sensing at several intermediate points of the mechanical structure of the arm. In the ideal case (when there are no perturbations), these three methods produce the same dynamic behavior of the arm. This paper compares their performances when perturbations and unmodelled dynamics are present. In particular, three cases are considered, i.e.. external disturbances in the tip. unmodelled dynamics in the inner loop, and changes in the carried load. Analytic and simulation studies have been carried out to compare these methods and the results show that the third method which uses sensing at the intermediate points of the arm, had the best performance in all three cases.
暂无评论