Wave Haptics: Building Stiff Controllers from the Natural Motor Dynamics
International Journal of Robotics Research
Technical Section: Stable haptic rendering with detailed energy-compensating control
Computers and Graphics
DC Motor Damping: A Strategy to Increase Passive Stiffness of Haptic Devices
EuroHaptics '08 Proceedings of the 6th international conference on Haptics: Perception, Devices and Scenarios
Extending the Z-Width of a Haptic Device Using Acceleration Feedback
EuroHaptics '08 Proceedings of the 6th international conference on Haptics: Perception, Devices and Scenarios
Stable Multirate Control Algorithm for Haptic Dental Training System
ICIRA '08 Proceedings of the First International Conference on Intelligent Robotics and Applications: Part II
Haptic Effects of Surgical Teleoperator Flexibility
International Journal of Robotics Research
Motion control of impedance-type haptic devices
ICRA'09 Proceedings of the 2009 IEEE international conference on Robotics and Automation
Improved multi-DOF haptics with spring drive amplifiers
IROS'09 Proceedings of the 2009 IEEE/RSJ international conference on Intelligent robots and systems
Extension of Colgate's passivity condition for variable-rate haptics
IROS'09 Proceedings of the 2009 IEEE/RSJ international conference on Intelligent robots and systems
Stability of haptic obstacle avoidance and force interaction
IROS'09 Proceedings of the 2009 IEEE/RSJ international conference on Intelligent robots and systems
Influence of vibration modes and human operator on the stability of haptic rendering
IEEE Transactions on Robotics
Robustly Stable Haptic Interaction Control using an Energy-bounding Algorithm
International Journal of Robotics Research
Passive-set-position-modulation framework for interactive robotic systems
IEEE Transactions on Robotics
Automatica (Journal of IFAC)
Enhancing the Z-width of Haptics Interfaces through Dual-rate Sampling
Proceedings of Conference on Advances In Robotics
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The "virtual wall" is the most common building block used in constructing haptic virtual environments. A virtual wall is typically based on a simple spring model, with unilateral constraints that allow the user to make and break contact with a surface. There are a number of factors (sample-and-hold, device dynamics, sensor quantization, etc.) that cause virtual walls to demonstrate active (nonpassive) behavior, destroying the illusion of reality. In this paper, we find an explicit upper bound on virtual wall stiffness that is a necessary and sufficient condition for virtual wall passivity. We consider a haptic display that can be modeled as a mass with Coulomb-plus-viscous friction, being acted upon by two external forces: an actuator and a human user. The system is equipped with only one sensor, an optical encoder measuring the position of the mass. We explicitly model the effects of position resolution, which has not been done in previous work. We make no assumptions about the human user, and we consider arbitrary constant sampling rates. The main result of our analysis is a necessary and sufficient condition for passivity that relies on the Coulomb friction in the haptic device, as well as the encoder resolution. We experimentally verify our results with a one-degree-of-freedom haptic display, and find that the system can display nonpassive behavior in two decoupled modes that are predicted by the necessary and sufficient condition. One mode represents instability, while the other mode results in active tactile sensations.