PUBLICATIONS

Follow the links below for publications. Contact Professor Imin Kao for more information.

Manuscripts:

  1. S.-F. Chen and I. Kao, "Approach the 6x6 Cartesian Stiffness Matrices of Robot Manipulators Via the Conservative Congruence Transformation", in preparation.
  2. S.-F Chen and I. Kao, "Extended Congruence Transformation for Joint and Cartesian Stiffness Matrices of Robotic Hands and Fingers", submitted for review. [Abstract] [PDF file]

 

Journal Papers:

  1. I. Kao, X. Wu, and S.-F Chen, "Dual Relationship in Dextrous Sliding Manipulation Under Force and Position Control", accepted for publication by International Journal of Robotics and Automation 1999. [Abstract only]
  2. N. Xydas and I. Kao, "Modeling of Contact Mechanics and Friction Limit Surface for Soft Fingers in Robotics with Experimental Results", International Journal of Robotics Research (IJRR) Vol. 18, No. 8, p941-950, September 1999. [Abstract only]
  3. I. Kao and C. Ngo, "Properties of Grasp Stiffness Matrix and Conservative Control Strategy", accepted for publication by the International Journal of Robotics Research (IJRR) 1999. [Abstract only]
  4. C. Gong and I. Kao, "Design for Accuracy and Repeatability for Robots Using Taguchi Methods", Journal of Concurrent Engineering Research and Applications, Vol. 5, pp. 263-278, September 1997. [Abstract only]
  5. I. Kao and C. Gong, "Robotic-Based Computer Integrated Manufacturing as Applied in Manufacturing Automation", Journal of Robotics and CIM, Vol. 13, No. 2, pp. 157-167, 1997. [Abstract only]
  6. I. Kao, M. R. Cutkosky, and R. S. Johansson, "Robotic Stiffness Control and Calibration as Applied to Human Grasping Tasks", IEEE Transactions of Robotics and Automation, 13(4): 557-566, August 1997. [Abstract only]
  7. I. Kao and M. R. Cutkosky, "Comparison of Theoretical and Experimental Force/Motion Trajectory for Dextrous Manipulation with Sliding", International Journal of Robotics Research, 12(6): 529-534, December 1993. [Abstract only]
  8. I. Kao and M. R. Cutkosky, "Quasistatic Manipulation with Compliance and Sliding", International Journal of Robotics Research, 11(1): 20-40, Feb. 1992. [Abstract only]
  9. M. R. Cutkosky and I. Kao, "Computing and Controlling the Compliance of a Robotic Hand", IEEE Transaction of Robotics and Automation, 5(2): 151-165, April 1989. [Abstract only]

 

Conference Proceedings:

  1. S.-F. Chen and I. Kao, "Geometrical Methods for Modeling the Asymmetric 6x6 Cartesian Stiffness Matrix", submitted to ICRA’00 conference. [Abstract] [PDF file]
  2. S.-F. Chen and I. Kao, "Simulation of Conservative Congruence Transformation: Conservative Properties in Joint and Cartesian Spaces", submitted to ICRA’00. [Abstract] [PDF file]
  3. N. Xydas, M. Bhagavat, and I. Kao, "Study of Soft Finger Contact Mechanics Using Finite Elements Analysis and Experiments", submitted ICRA’00. [Abstract] [PDF file]
  4. N. Xydas and I. Kao, "Influence of Material Properties and Fingertip Size on The Power-Law Equation for Soft Fingers", submitted to ICRA’00. [Abstract] [PDF file]
  5. S.-F Chen and I. Kao, "The Conservative Congruence Transformation of Stiffness Control in Robotic Grasping and Manipulation", the 9th International Symposium on Robotics Research (ISRR), Snowbird, Utah, October 1999. [Abstract only]
  6. S.-F Chen and I. Kao, "Simulation of Conservative Properties of Stiffness Matrices in Congruence Transformation’, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Canada, October 1998. [Abstract only]
  7. N. Xydas and I. Kao, "Modeling of contact mechanics with experimental results for soft fingers", in the Proceeding of IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), p 488-493, Canada, October 1998. [Abstract only]
  8. X. Wu and I. Kao, "Transmissibility of Force and Motion in Dextrous Manipulation", IEEE International Conference on Robotics and Automation, Vol. 1, pp. 616-621, April 1996. [Abstract only]
  9. J. Li and I. Kao, "Grasp Stiffness Matrix -- Fundamental Properties in Analysis of Grasping and Manipulation", IEEE/RSJ International Conference on Intelligent Robots and Systems, Vol. 2, pp. 381-386, August 1995. [Abstract only]
  10. Y. Xue and I. Kao, "Dextrous Sliding Manipulation Using Soft Fingers", IEEE International Conference on Robotics and Automation, Vol. 4, pp.3397-3402, 1994. [Abstract only]
  11. I. Kao, "Stiffness Control and Calibration of Robotic and Human Hands", IEEE International Conference on Robotics and Automation, Vol. 1, pp.399-406, 1994. [Abstract only]
  12. S.-T. Wang and I. Kao, "Artificial Neural Network Control of Flexible Manipulators", Artificial Neural Network in Engineering 93, pp. 587-592, Nov. 1993, ASME Publisher. [Abstract only]
  13. R. Howe, N. Popp, P. Akella, I. Kao and M. R. Cutkosky, "Grasping, Manipulation and Control with Tactile Sensing", In Proceedings of 1990 IEEE International Conference on Robotics and Automation, pp. 1258-1263, Cincinnati, Ohio, May 13-18, 1990. [Abstract only]
  14. I. Kao and M. R. Cutkosky, "Quasistatic Sliding Manipulation – on the transient response of quasistatic manipulation", Proceedings of the 4th IEEE International Symposium on Intelligent Control, pp. 438-443, Albany, New York, September 25-27, 1989. [Abstract only]
  15. I. Kao and M. R. Cutkosky, "Dextrous Manipulation with Compliance and Sliding", 5th International Symposium on Robotics Research, H. Miura and S. Arimoto, eds., M.I.T. Press, Cambridge, MA, 1990, Chapter 6, pp. 375-382. [Abstract only]
  16. R. Howe, I. Kao, and M. R. Cutkosky, "Sliding of robot fingers under combined torsion and shear loading", In Proceedings of 1988 IEEE International Conference on Robotics and Automation, Vol. 1, pp. 103-105, Philadelphia, Pennsylvania, April 24-29 1988. [Abstract only]
  17. M. R. Cutkosky, P. Akella, I. Kao, and R. Howe, "Grasping as a Contact Sport", 4th International Symposium on Robotics Research, B. Roth and R. Bolles, eds., pp.191-198, MIT Press, 1987. [Abstract only]

 

Non-Refereed Papers, Reports

  1. I. Kao, "Conservative Properties of a Stiffness Matrix in Grasping and Manipulation", 1998 NSF Design and Manufacturing Grantees Meeting, January 5-8, 1998, Monterrey, Mexico.
  2. I. Kao, "Dual Relationship in Dextrous Sliding Manipulation Under Force and Position Control", NSF Grantees Conference, 1/7--1/10/97, Seattle, Washington.
  3. I. Kao, "Taguchi Methods as Applied in Robotic-Based CIM", The First Regional Symposium on Manufacturing Science and Technology, October 12-13, 1995.
  4. C. Gong and I. Kao, "Design of Accuracy and Repeatability Using Taguchi Methods", Department of Mechanical Engineering Technical Report: TR96-001, 1996.
  5. C. Gong and I. Kao, "Design and Analysis of Robotic Manipulators Using Signal-to-Noise Ratio", Department of Mechanical Engineering Technical Report: TR95-001, 1995.

ABSTRACTS

[Abstract] In this paper, we develop the theoretical work on the properties and mapping of stiffness matrices between joint and Cartesian spaces of robotic hands and fingers, and propose the extended congruence transformation. In this paper, we show that the conventional congruence transformation between the joint and Cartesian spaces, Kq =Jq TKpJq , first derived by Salisbury, is only valid at the equilibrium configuration. Once the grasping configuration is deviated from its equilibrium (for example, by the application of an external force), the extended congruence transformation should be used. Theoretical development and numerical simulation are presented. The extended congruence transformation accounts for the change in geometry via the differential Jacobian (Hessian matrix) of the robot manipulators when an external force is applied. The effect is captured in an effective stiffness matrix, Kq , of the extended congruence transformation. The results of this paper also indicate that the omission of the changes in Jacobian in the presence of external force would result in discrepancy of the work and lead to contradiction to the fundamental conservative properties of stiffness matrices. Through extended congruence transformation, conservative and consistent properties of stiffness matrices can be preserved during mapping regardless of the usage of coordinate frames and the existence of external force. [Back to top] 

[Abstract] In this paper, we investigate the dextrous sliding manipulation under both force and position controls using soft fingers. We study the motion trajectory of sliding manipulation under force control as well as the force/moment trajectory on the limit surface under position control. It is found that the characteristic pitch, l , (defined as the ratio between the maximum moment and the maximum friction force of a soft finger) and x (the ratio between characteristic dimension and the characteristic pitch) characterize sliding manipulation. The rate of change of grasping parameters, such as the velocity of grasped object, can be represented by the dimensionless geometric parameter, x , and the partial geometric velocity, x / t. In addition, a dual relationship for the parameters of the manipulation is deduced. The dual relationship is a consequence of the force control (trajectory prediction) and position control (trajectory planning) as applied in sliding manipulation. The results are presented with both analytical results and simulation using x and l . The results of numerical simulation were found to match well with the theoretical analysis using differential relationship. [Back to top] 

[Abstract] A new theory in contact mechanics for modeling of soft fingers is proposed to define the relationship between the normal force and radius of contact for soft fingers by considering general soft finger materials,including linear and nonlinearly elastic materials. The results show that the radius of contact is proportional to the normal force raised to the power of g which ranges from 0 to 1/3. This new theory subsumes the Hertzian contact model for linear elastic materials where g=1/3. Experiments are conducted to validate the theory using artificial soft fingers made of various materials such as rubber and silicone. Results for human fingers are also compared. This theory provides basis for constructing friction limit surface numerically. The numerical friction limit surface can be approximated by an ellipse with the major and minor axes as the maximum friction force and maximum moment with respect to the normal axis of contact, respectively. Combining the results of the contact mechanics model with the contact pressure distribution, the normalized friction limit surface can be derived for anthropomorphic soft fingers. The results of the contact mechanics model and pressure distribution for soft fingers facilitate the construction of numerical friction limit surface, and will enable us to analyze and simulate contact behaviors of grasping and manipulation in robotics. [Back to top] 

[Abstract]  

[Abstract] In this paper, we study the 6x6 Cartesian stiffness matrices of conservative systems using the method of changing basis in differential geometry of the motion of the rigid body. We prove that the stiffness matrix is symmetric at an unloaded equilibrium configuration. When the system is subjected to external loads, the 6x6 Cartesian stiffness matrix becomes asymmetric. The skew-symmetric part of the stiffness matrix is equal to the negative one-half of the cross-product matrix formed by the externally applied load, referenced to the inertial frame. The Cartesian stiffness referenced to the moving frame is the transpose of that referenced to inertial frame. [Back to top] 

[Abstract] In this paper, the stiffness characteristics of robot systems via the conservative congruence transformation (CCT) and the conventional congruence transformation (CT) between the joint and Cartesian spaces are investigated by implementing the simulation of a two-link planar manipulator manipulating along closed paths with no self-intersection. A stiffness matrix is conservative if (1) the force resulting from the stiffness matrix is conservative, and (2) the work done by such force along a closed path is zero, i.e., independent of the path. The numerical simulation shows that a stiffness matrix in R3x3 Cartesian space or joint space with n generalized coordinates will be conservative if it is symmetric and satisfies the exact differential criterion. Simulation of a two-link manipulator is presented to illustrate the effects of geometrical changes on differential motions in grasp manipulation and conservative stiffness control. The results show that the CCT is the correct mapping for stiffness matrices in the joint and Cartesian spaces. [Back to top] 

[Abstract] 

[Abstract] 

[Abstract] In this paper, we present the new theory of conservative congruence transformation (CCT) to replace the conventional congruence formulation, Kq =Jq TKpJq , first derived by Salisbury in 1980. The conservative congruence transformation defines the correct and consistent mapping of the stiffness matrices between the joint and Cartesian spaces. We present the theory and simulation, and show that the conventional formulation is only valid when the manipulator is maintained at unloaded position all the time. Once the grasping and manipulation are deviated from the unloaded configuration by the application of conservative force, the CCT must be used. The CCT takes into consideration the changes in geometry through the differential Jacobian, or the Hessian, matrix of the robot manipulators. We also show that the omission of the changes in the Jacobian during grasping and manipulation would result in discrepancy of the work, and lead to contradiction to the fundamental physical properties of stiffness control. The CCT, however, preserves the conservative and consistent properties of stiffness control in robotics for the mapping between the joint and Cartesian spaces. [Back to top] 

[Abstract] In this paper, the conservative properties of stiffness matrices via the nonconservative congruence mapping between the joint and Cartesian spaces are investigated with simulation of two fingers manipulating an object. The properties of both constant and configuration dependent stiffness matrices are presented with integration of work when manipulating along a closed path with no self-intersection. A stiffness matrix is conservative if the force resulting from the stiffness matrix is conservative, and the work done by such force along a closed path is zero, i.e., independent of the path. Both theoretical derivation and numerical simulation show that a stiffness matrix in R3x3 Cartesian space or joint space with n generalized coordinates will be conservative if it is symmetric and satisfies the exact differential criterion. Simulation of two fingers manipulating an object is implemented using OpenGL with both Cartesian-based and joint-based stiffness control schemes. The results show that the congruence transformation generally results in nonconservative stiffness matrix, except for a special group of configuration dependent solutions. [Back to top] 

[Abstract] A new theory in contact mechanics for modeling of soft fingers is proposed to define the relationship between normal force and area of contact for soft fingers by considering the soft finger materials as nonlinearly elastic. The results show that the radius of contact is proportional to the normal force raised to the power of g; which ranges from 0 to 1/3. This new theory subsumes the Hertzian contact model for linear elastic materials where g= 1/3. Experiments are conducted to validate the theory using artificial soft fingers made of various materials such as rubber and silicone. This theory provides basis for constructing friction limit surface numerically. Combining the results of the contact mechanics model with the contact friction model the normalized friction limit surface is derived for anthropomorphic soft fingers. [Back to top] 

Last edited on October 22, 1999.