Wave Haptics: Building Stiff Controllers from the Natural Motor Dynamics

Haptics, like the fields of robotics and motion control, relies on high stiffness position control of electric motors. Traditionally, DC motors are driven by current amplifiers designed to hide their electrical dynamics. Meanwhile encoder-based position feedback creates virtual springs. Unfortunately this cancellation-replacement approach experiences performance limits due to sensor quantization, discretization, and amplifier bandwidths. An alternate approach is presented, noting the inherent inductor-resistor dynamics of the motor are beneficial to the haptic task. Two main insights are followed, which may be utilized independently or preferably in combination. First, the electrical inductance L can serve as a stiffness, providing a natural sensorless coupling between the virtual environment and the user. Second, the electrical resistance R can create a natural wave transformation, providing a robust computer interface between the discrete and continuous time domains. The resulting analog circuit implements a simple voltage drive and can achieve higher stiffness than traditional approaches, especially in the frequency range where human users are most sensitive. A prototype 1-DOF system has been implemented and confirms the promise of this novel paradigm.

[1]  Günter Niemeyer,et al.  Practical limitations of wave variable controllers in teleoperation , 2004, IEEE Conference on Robotics, Automation and Mechatronics, 2004..

[2]  Vincent Hayward,et al.  High-fidelity passive force-reflecting virtual environments , 2005, IEEE Transactions on Robotics.

[3]  J. Edward Colgate,et al.  Passivity of a class of sampled-data systems: Application to haptic interfaces , 1997, J. Field Robotics.

[4]  Allison M. Okamura,et al.  A Sufficient Condition for Passive Virtual Walls With Quantization Effects , 2004 .

[5]  Karun B. Shimoga,et al.  A survey of perceptual feedback issues in dexterous telemanipulation. II. Finger touch feedback , 1993, Proceedings of IEEE Virtual Reality Annual International Symposium.

[6]  Blake Hannaford,et al.  Time domain passivity control of haptic interfaces , 2001, Proceedings 2001 ICRA. IEEE International Conference on Robotics and Automation (Cat. No.01CH37164).

[7]  R. Rosenberg,et al.  System Dynamics: Modeling and Simulation of Mechatronic Systems , 2006 .

[8]  Jean-Jacques E. Slotine,et al.  Telemanipulation with Time Delays , 2004, Int. J. Robotics Res..

[9]  J. Edward Colgate,et al.  Factors affecting the Z-Width of a haptic display , 1994, Proceedings of the 1994 IEEE International Conference on Robotics and Automation.

[10]  Günter Niemeyer,et al.  Switching motor control: an integrated amplifier design for improved velocity estimation and feedback , 2004, IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004.

[11]  A. Galip Ulsoy,et al.  CONTROL OF dc SERVO-MOTOR DRIVEN ROBOTS. , 1982 .

[12]  Neal A. Tanner,et al.  Wave Haptics: Encoderless Virtual Stiffnesses , 2005, ISRR.

[13]  Randy A. Freeman,et al.  Environment delay in haptic systems , 2000, Proceedings 2000 ICRA. Millennium Conference. IEEE International Conference on Robotics and Automation. Symposia Proceedings (Cat. No.00CH37065).

[14]  M. Kawai,et al.  Haptic display with an interface device capable of continuous-time impedance display within a sampling period , 2004, IEEE/ASME Transactions on Mechatronics.

[15]  R. W. Daniel,et al.  Fundamental Limits of Performance for Force Reflecting Teleoperation , 1998, Int. J. Robotics Res..

[16]  J. Edward Colgate,et al.  Increasing the impedance range of a haptic display by adding electrical damping , 2005, First Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems. World Haptics Conference.

[17]  Thomas H. Massie,et al.  The PHANToM Haptic Interface: A Device for Probing Virtual Objects , 1994 .

[18]  Werner Leonhard,et al.  Control of Electrical Drives , 1990 .

[19]  John Kenneth Salisbury,et al.  The effect of quantization and Coulomb friction on the stability of haptic rendering , 2005, First Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems. World Haptics Conference.

[20]  Günter Niemeyer,et al.  Wave Haptics: Providing Stiff Coupling to Virtual Environments , 2006, 2006 14th Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems.

[21]  John Kenneth Salisbury,et al.  Stability of Haptic Rendering: Discretization, Quantization, Time Delay, and Coulomb Effects , 2006, IEEE Transactions on Robotics.

[22]  Allison M. Okamura,et al.  Effects of position quantization and sampling rate on virtual-wall passivity , 2005, IEEE Transactions on Robotics.

[23]  Arjan van der Schaft,et al.  Geometric scattering in robotic telemanipulation , 2002, IEEE Trans. Robotics Autom..

[24]  Jean-Jacques E. Slotine,et al.  Using wave variables for system analysis and robot control , 1997, Proceedings of International Conference on Robotics and Automation.

[25]  Lucy Y. Pao,et al.  Rate-hardness: a new performance metric for haptic interfaces , 2000, IEEE Trans. Robotics Autom..