Honggen Fang

An exoskeleton master hand for controlling DLR/HIT hand

In order to eliminate the drawbacks of conventional force feedback gloves, a new type of master hand has been developed. By utilizing three “four-bar mechanism joint” in series and wire coupling mechanism, the master finger transmission ratio is kept exact 1:1.4:1 in the whole movement range and it can make active motions in both extension and flexion direction. Additionally, 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 with 200µs cycle time is designed. The operating modes of the master hand can be contact or non-contact, which depends on the motion states of slave hand, free motion or constrained motion. The position control employed in non-contact mode ensures unconstrained motion and the force control adopted in contact mode guarantees natural contact sensation. To evaluate the performances of the master hand, an master-slave control experiment based on Force-Position control method between the master hand and DLR/HIT hand is conducted. The results demonstrate this new type master hand can augment telepresence.

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 “four-bar mechanism joint”, which rotates about an instant center that coincides with joint center of operators 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.

DSP&FPGA-based joint impedance controller for DLR/HIT II dexterous robot hand

A position-based joint impedance controller and a DSP&FPGA-based multilevel control structure were developed to improve the capabilities of robot hand performing task in a variety of environments. Based on finite element analysis technologies, the new torque sensors and giant magnetoresistance (GMR) position sensors were designed and applied, and meet the challenge of joint torque measuring and position measuring. The experimental results of joint impedance control show that proposed strategy not only improves the effectiveness of contact task performance, but also provides compliant interaction of robot hand with a person, thus enables robot hand to work in different environments.

Collision detection of flexible joint manipulator by using joint torque sensors

In this paper, we discuss a collision detection approach which enables the flexible joint manipulator to work safely in an unstructured environment. By using joint torque sensors, a novel Cartesian impedance control law is proposed to implement the compliance control at first; then adaptive dynamics joint controller is extended to all the joints for achieving precision control performance; furthermore, a Cartesian force-feedback path generation is developed for collision detection. The proposed approach simplifies application to the manipulator, keeps the manipulation friendly to the environment, and rigorously guarantees the asymptotical stability of the entire system. The experimental results illustrate the validity of the developed collision detection and planning scheme.

An Exoskeleton System for Measuring Mechanical Characteristics of Extravehicular Activity Glove Joint

This paper presents a novel exoskeleton hand system for measuring extravehicular activity spacesuit glove (EVA glove) joints mechanical characteristics. For adapting to variety sizes of gloves, the proximal phalanx of exoskeleton finger can be adjusted through an additional four-bar transmission mechanism. The exoskeleton hand can apply forces that actuate both flexion and extension of EVA glove. Based on its special mechanical structure, a mathematic model of flexible EVA glove joint has been built.