Shaowei Fan

Multisensory five-finger dexterous hand: The DLR/HIT Hand II

This paper presents a new developed multisensory five-fingered dexterous robot hand: the DLR/HIT Hand II. The hand has an independent palm and five identical modular fingers, each finger has three DOFs and four joints. All the actuators and electronics are integrated in the finger body and the palm. By using powerful super flat brushless DC motors, tiny harmonic drivers and BGA form DSPs and FPGAs, the whole fingerpsilas size is about one third smaller than the former finger in the DLR/HIT Hand I. By using the steel coupling mechanism, the phalanx distalpsilas transmission ratio is exact 1:1 in the whole movement range. At the same time, the multisensory dexterous hand integrates position, force/torque and temperature sensors. The hierarchical hardware structure of the hand consists of the finger DSPs, the finger FPGAs, the palm FPGA and the PCI based DSP/FPGA board. The hand can communicate with external with PPSeCo, CAN and Internet. Instead of extra cover, the packing mechanism of the hand is implemented directly in the finger body and palm to make the hand smaller and more human like. The whole weight of the hand is about 1.5Kg and the fingertip force can reach 10N.

Development of a Flexible 3-D Tactile Sensor System for Anthropomorphic Artificial Hand

In this paper, we report a novel flexible tactile sensor array for an anthropomorphic artificial hand with the capability of measuring both normal and shear force distributions using quantum tunneling composite as a base material. There are four fan-shaped electrodes in a cell that decompose the contact force into normal and shear components. The sensor has been realized in a 2 ×  6 array of unit sensors, and each unit sensor responds to normal and shear stresses in all three axes. By applying separated drops of conductive polymer instead of a full layer, cross-talk between the sensor cells is decreased. Furthermore, the voltage mirror method is used in this circuit to avoid crosstalk effect, which is based on a programmable system-on-chip. The measurement of a single sensor shows that the full-scale range of detectable forces are about 20, 8, and 8 N for the x-, y-, and z-directions, respectively. The sensitivities of a cell measured with a current setup are 0.47, 0.45, and 0.16 mV/mN for the x-, y-, and y-directions, respectively. The sensor showed a high repeatability, low hysteresis, and minimum tactile crosstalk. The proposed flexible three-axial tactile sensor array can be applied in a curved or compliant surface that requires slip detection and flexibility, such as a robotic finger.

Experimental study on impedance control for the five-finger dexterous robot hand DLR-HIT II

This paper presents experimental results on the five-finger dexterous robot hand DLR-HIT II, with Cartesian impedance control based on joint torque and nonlinearity compensation for elastic dexterous robot joints. To improve the performence of the impedance controller, system parameter estimations with extended kalman filter and gravity compensation have been investigated on the robot hand. Experimental results show that, for the harmonic drive robot hand with joint toruqe feedback, accurate position tracking and stable torque/force response can be achieved with cartesian and joint impedance controller. In addition, a FPGA-based control architecture with flexible communication is proposed to perform the designed impedance controller.

A dexterous humanoid five-fingered robotic hand

This paper presents a new developed multisensory five-fingered dexterous robot hand : the DLR/HIT Hand II. The hand has an independent palm and five identical modular fingers, each finger has three DOFs and four joints. All the actuators and electronics are integrated in the finger body and the palm. By using powerful super flat brushless DC motors, tiny harmonic drives and BGA form DSPs and FPGAs, the whole fingerpsilas size is about one third smaller than the former finger in the DLR/HIT Hand I. By using the steel coupling mechanism, the phalanx distalpsilas transmission ratio is exact 1:1 in the whole movement range. At the same time, the multisensory dexterous hand integrates position, force/torque and temperature sensors. The hierarchical hardware structure of the hand consists of the finger DSPs, the finger FPGAs, the palm FPGA and the PCI based DSP/FPGA board. The hand can communicate with external with PPSeCo , CAN and Internet. Instead of extra cover, the packing mechanism of the hand is implemented directly in the finger body and palm to make the hand smaller and more human like. The whole weight of the hand is about 1.5 Kg and the fingertip force can reach 10N.

Development of a multi-DOF prosthetic hand with intrinsic actuation, intuitive control and sensory feedback

Purpose – The purpose of this paper is to present a five-fingered, multisensory prosthetic hand integrating both intuitive myoelectric control and sensory feedback. Design/methodology/approach – The artificial hand’s palm has a three-arcuate configuration and the thumb can move along a cone surface, improving the resemblance with the biological hand. By using a coupling linkage mechanism, each finger is independently actuated by a direct current motor. Both torque and position sensors are embedded in the finger to sense the hand’s status and its interaction with the outer environment. The proposed human-in-the-loop control system consists of an internal motion control scheme and an external human–machine interface. The pattern recognition-based electromyography (EMG) control scheme is adopted to control the motion of the hand, and the transcutaneous electrical nerve stimulation (TENS) is utilized to feedback the hand’s sensory information to its user. Findings – The hand prototype shows that it has an ant...

EXPERIMENTAL EVALUATION OF CARTESIAN AND JOINT IMPEDANCE CONTROL WITH ADAPTIVE FRICTION COMPENSATION FOR THE DEXTEROUS ROBOT HAND DLR-HIT II

This paper presents impedance controllers with adaptive friction compensation for the five-finger dexterous robot hand DLR-HIT II in both joint and Cartesian space. An FPGA-based control hardware and software architecture with real-time communication is designed to fulfill the requirements of the impedance controller. Modeling of the robot finger with flexible joints and mechanical couplings in the differential gear-box are described in this paper. In order to address the friction due to the complex transmission system and joint coupling, an adaptive model-based friction estimation method is carried out with an extended Kalman filter. The performance of the impedance controller with both adaptive and parameter-fixed friction compensations for the robot hand DLR-HIT II are analyzed and compared in this paper. Furthermore, gravity estimation is implemented with Least Squares technique to address uncertainties in gravity compensation due to the close proximity and complexity of robot hand components. Experimental results prove that accurate position tracking and stable torque/force response can be achieved with the proposed impedance controller with friction compensation on five-finger dexterous robot hand DLR-HIT II.

Object shape recognition approach for sparse point clouds from tactile exploration

In this paper a novel approach is proposed for tactile shape recognition, which uses tactile point location and normal information. Superquadric functions are applied to construct several shape primitives and k-means unsupervised clustering method is used to partition the objects as several patches. By extracting geometrical features from each patch and rearranging features, object feature vectors are constructed for Gaussian process (GP) classifier to identify object shapes. Simulations results prove that our approach can achieve a high recognition rate in object shape classification task from sparse and noisy tactile point clouds.

An anthropomorphic design guideline for the thumb of the dexterous hand

The preeminent manipulation capabilities of the human hand are undoubtedly related to the thumb. In view of this, this paper presents an anthropomorphic design guideline for the thumb of the dexterous hand. Anatomy analysis of the human thumb represents an excellent base from which a robotic design can be inferred. With simplification of human thumbs joint motion model, five configurations of thumb are given for the design of dexterous robotic hand. A new method for determining the position of thumb on the palm is proposed, according to the Euler Theorem about Finite Rotation of Rigid Body. A numeric method for computing the opposability of the thumb is described based on Monte Carlo methods, to evaluate dexterity of the hand in object manipulation. In order to verify the effectiveness of the proposed method, it is applied to the revised design of the HIT/DLR II hand. Performance indexes of both the original and the revised hand are calculated for comparison. The opposability of the thumb on revised dexterous robotic hand is 2.92 times of the original, which indicates the effectiveness of the proposed method.

Cartesian impedance control on five-finger dexterous robot hand DLR-HIT II with flexible joint

This paper presents an impedance controller for five-finger dexterous robot hand DLR-HIT II, which is derived in Cartesian space. By considering flexibility in finger joints and strong mechanical couplings in differential gear-box, modeling and control of the robot hand are described in this paper. The model-based friction estimation and velocity observer are carried out with an extended Kalman filter, which is implemented with parameters estimated by Least Squares Method. The designed estimator demonstrates good prediction performance, as shown in the experimental results. Stability analysis of the proposed impedance controller is carried out and described in this paper. Impedance control experiments are conducted with the five-finger dexterous robot hand DLR-HIT II in Cartesian coordinates system to help study the effectiveness of the proposed controller with friction compensation and hardware architecture.

Haptic Perception of Unknown Object by Robot Hand: Exploration Strategy and Recognition Approach

In this paper, the exploration and recognition in unknown object perception by robot hand is discussed. Inspired by the touch and exploration of human hand, a haptic exploration strategy for multi-fingered robot hand is proposed. Based on the observations from human experiments, the proposed strategy can be used to guide the robot hand to plan a series of movements to get tactile information from different unknown objects, with the precondition of avoiding unexpected collisions with the objects. A recognition approach is then presented to recognize object shapes based on the tactile point data collected by the strategy. Geometric feature vectors are extracted from tactile point locations and normal vectors after clustering, and the object shapes are recognized by the random forests classifier. Simulations and experiments results show that the exploration strategy can be used to guide the robot to gather tactile information from unknown object automatically, and the recognition approach is effective and robust in object shape recognition work. This framework provides a sensible solution for robot unknown object perception problem, which is suitable for the multi-fingered robot hand with low-resolution tactile sensors.