FPGA based time domain Passivity Observer and Passivity Controller

In this paper, field programmable gate array (FPGA) based time domain passivity observer and passivity controller is proposed to improve the stability range of haptic interfaces. A simplified PO/PC algorithm is implemented on FPGA for improving the control efficiency. Thanks to the fast sampling rate and the parallel processing ability of the FPGA, the PO/PC can be updated irregularly only when encoder pulse happen instead of updating every single msec. Reference current calculated from virtual wall was used for the energy calculation instead of measured motor current to avoid signal noise. The simplified FPGA based PO/PC approach is compared with the software based approach. The experimental results show that the noise behavior during low velocity contact is dramatically reduced.