Wave haptics: using motor dynamics for stiff coupling to virtual environments

Traditional haptic rendering creates virtual springs using DC motors with current amplifiers and encoder-based position feedback. It is well known that the stiffness of virtual environments is limited by quantization, discretization, and amplifier bandwidth effects. In this paper we propose a novel control architecture that, rather than canceling motor electrical dynamics, uses them to achieve better performances. First we recognize that the inductance L provides a natural sensor-less stiff behavior at high frequencies. Second, electrical resistance R serves as the basis of a wave transform that, performed through an analog circuit, allows to build a more stable interface with virtual environments, achieving robustness to servo delays and discretization. Encoder feedback and digital control loop are required only to provide parametric robustness at low frequencies. A prototype 1-DOF system has been implemented and confirms the promise of this novel paradigm