Projects

In this paper, a new method for optimal calibration of parallel kinematic machines (PKMs) is presented. The basis of the methodology is to exploit the least error sensitive regions in the workspace to yield optimal calibration. To do so, an error model is devel- oped that takes into consideration all the geometric errors due to imprecision in manu- facturing and assembly. Based on this error model, it is shown that the error mapping from the geometric errors to the pose error of the PKM depends on the Jacobian inverse. The Jacobian inverse would introduce spurious errors that would affect the calibration results, if used without proper care. Hence, areas in the workspace with smaller condition numbers are selected for calibration. Simulations and experiments are presented to show the effectiveness of the proposed method. Calibration software based on the proposed method has been embedded in the tripod developed at the National Research Council of Canada’s Integrated Manufacturing Technologies Institute.

Verner, M., Xi, F., Mechefske, C. K.,  “Optimal Calibration of Parallel Kinematic Machines“, ASME Journal of Mechanical Design, vol. 127, no. 1, pp 62-69, Jan, 2005.

In this paper, a reconfigurable tripod machine tool system is introduced, with a focus on dynamic modeling. The Newton-Euler approach is applied and a new modeling procedure is proposed. In the procedure of the dynamic modeling, the reference coordinate system for the forces/torques calculation and that for the equilibrium equations derivation are dealt with respectively. As a result, specific structural features of the tripod system are utilized to simplify the dynamic model and, thus, reduce the calculation complexity. The prototype tripod system is developed and the presented method is implemented for its configuration design. An experiment is conducted to validate the dynamic model.

Bi, Zhuming, Lang, Sherman, and Verner, Marcel, “Dynamic Modeling and Validation of a Tripod-based Machine Tool“, The International Journal of Advanced Manufacturing Technology, vol. 37, no 3-4, pp. 410-421, May 2008.

This paper presents a new methodology and framework for web-based systems that can be used in distributed manufacturing environments. A prototype is developed to demonstrate its application to remote monitoring and control of a Tripod – one type of parallel kinematic machine. It utilizes the latest Java technologies (Java 3D and Java Servlets) as enabling technologies for system implementation. Instead of using a camera for monitoring, the Tripod is modeled using Java 3D with behavioral control nodes embedded. Once downloaded from its server, the 3D model behaves in the same way of its counterpart at client-side. It remains alive by connecting with the Tripod through message passing, e.g. sensor signals and control commands transmissions. The goal of this research is to eliminate network traffic with Java 3D models, while still providing users with intuitive environments. In the near future, open-architecture devices will be web-ready having Java virtual machines embedded. This will make the approach more effective for web-based device monitoring and control.

Wang, L., Sams, R., Verner, M., Xi. F., “Web-Based and Sensor-Driven Device Monitoring and Control Using Java 3D”, Proceedings of the 12th International Conference on Flexible Automation and Intelligent Manufacturing, Dresden, Germany, pp. 772-781, July 2002.

Winner of the Best Paper Award at the 12th International Conference on Flexible Automation & Intelligent Manufacturing, July 16th – 17th, 2002, Dresden Germany

A tripod is one type of parallel kinematic machine having three degrees of freedom. The sliding-leg tripod presented in this paper is designed as a programmable add-on device for manufacturing and shop floor automation. It can be used as a toolhead for machine tools, or as a work stage for coordinate measuring machines. Its purpose is to enhance the capability of a machine by providing it with a more flexible range of motion and controllability from any distance. As decentralization of manufacturing grows, shop floor equipment like this is required to become networkable and remotely accessible. This paper focuses on two separate issues: Tripod design optimization and its remote manipulation, including real-time monitoring and remote control of the tripod. A tripod prototype and a web-based software system are developed to verify the feasibility of the approach as well as the tripod accessibility in a distributed environment. It is shown that the proposed approach can improve the tripod design and its controllability. A large application potential of this approach is also predicted.

Wang, L., Xi, F., Zhang, D., Verner, M.,  “Design Optimization and Remote Manipulation of a Tripod“, International Journal of Computer Integrated Manufacturing, vol. 18, no. 1, pp. 85-95, Jan, 2005.

This paper summarizes our survey on the development of reconfigurable machines (RMs). The goals of this survey were to (i) clarify the needs and drivers to develop the RMs, (ii) define the academic and practical issues involved in the development of RMs, (iii) learn the state of the art of the R&D on design methodologies of the RMs, and (iv) identify future research directions, which benefit the manufacturing industries in short and long terms. The survey has concluded that reconfigurable manufacturing systems (RMSs) are advantageous in dealing with changes and uncertainties in the ever-changing environment; while RMs are essential components to implement an RMS. RMs should be designed to meet a variety of task requirements via its reconfigurability. It has been found that few existing RMs can achieve this objective. The survey has concluded that the obstacles of the development of RMs include (i) the difficulties to identify and generalize design requirements since an RM is application-oriented and the design requirements have to be defined from an actual application; and in fact, some requirements are very difficult to be quantified; (ii) the lacking of efficient automated robot programming tools despite that the robots are essential components for most of the RMs; (iii) the lack of effective technologies that can be used to support system reconfigurations; (iv) no international organization that serves for standardizing the modular components for manufacturing and assembly processes; (v) the lack of the effort in implementing a heterogeneous system consisting of different types of RMs. The survey has suggested some future research works to overcome these obstacles.

Bi, Z. M., Lang, S. Y. T., Verner, M., Orban, P. “Development of reconfigurable machines”, The International Journal of Advanced Manufacturing Technology, online, Dec 2007.