An exoskeleton force feedback master finger distinguishing contact and non-contact mode

In this paper, a new type of master finger in exoskeleton type has been developed to implement master-slave operation for DLR/HIT dexterous hand. The finger has three novel characteristics. Firstly, the exoskeleton mechanism uses ldquofour-bar mechanism jointrdquo, which rotates about an instant center that coincides with joint center of operator´s finger. Secondly, the master finger can distinguish the contact and non-contact mode. The two modes enable free motion and natural contact sensation between operator and master finger respectively. Thirdly, the master finger can exert forces in the direction of extension and flexion because it can make active motion in the two directions. In order to assure faster data transmission and near zero delay in master-slave operation, a digital signal processing/field programmable gate array (DSP/FPGA-FPGA) structure is proposed to control the master finger. The kernel of the hardware system consists of a peripheral component interface (PCI)-based DSP/FPGA board configured as high-level and a FPGA board configured as low-level. By utilizing low-voltage differential signaling (LVDS) serial data bus and PCI bus, the high-level can communicate with the low-level and PC. Using the principle of Virtual work, the relationship between driving torque and the force acting at the tip of master finger is acquired and validated by an experiment conducted to the operation of master finger and DLR/HIT dexterous finger. Experimental results also demonstrate that the master finger can augment telepresence.