A Hybrid Actuation System for Enhancing the Performance Metrics Related to Kinesthetic-Type Haptic Devices

High torque to volume ratio, fast response, and high dynamic range are some of the desired performance metrics for kinesthetic-type haptic device actuation systems. In this article, we present a hybrid actuation system consisting of an active actuator and a magnetorheological fluid-based brake (MRF brake). MRF brake’s tradeoffs, namely, <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-state torque and slow response (compared to an electric motor), are investigated and resolved by this hybrid actuation system. First, the transient behavior of the MRF brake is investigated and an mathematical model is proposed to mimic its transient response behavior. It is found that the performance of the proposed model performs better than the conventionally used first-order transfer function. Second, hybrid actuation system is constructed. The active actuator is used for compensating for the speed of the response and the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-state torque based on the proposed mathematical model of the MRF brake. It is measured that the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-state torque is largely eliminated from 0.178 to 0.008 N<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula>m, the dynamic range is enlarged from 15 to 42.4 dB, and its time constant is improved from 69.6 to 4.4 ms when the hybrid actuation system is used instead of just an MRF brake.