An adaptive-method for velocity estimation using time-to-digital converter

Efficient velocity estimation plays an important role in the stability of haptic interfaces. In this work, a new digital circuit is realized to reduce the noise level in low velocity estimation. The proposed adaptive-method (A-method) is based on the concept of measuring the time-interval between two or more incoming quadrature pulses from the optical encoder to the order of picoseconds (ps). A time-to-digital converter (TDC) is used initially to implement the conventional velocity estimation techniques like frequency-count method (M-method) and period-count method (T-method). Later, the two methods are implemented simultaneously using the TDC for the adaptive estimation. The range of TDC used is 0-110 nanoseconds with 420-425 ps resolution. A carry-chain was implemented in order to remove non-linearity and increase precision. Experimental results demonstrate the superiority of the proposed A-method over the conventional T- and M-methods.