Zongwu Xie

The Modular Multisensory DLR-HIT-Hand: Hardware and Software Architecture

This paper presents hardware and software architecture of the newly developed compact multisensory German aerospace research (DLR)-Harbin Institute of Technology (HIT)-Hand. The hand has four identical fingers and an extra degree of freedom for the palm. In each finger, there is a field-programmable gate array (FPGA) for data collection, brushless dc motors for control, and communication is accomplished with palms FPGA by point-to-point serial communication (PPSeCo). The kernel of the hardware system is a peripheral component interconnect (PCI)- based high-speed floating-point DSP for data processing, and FPGA for high-speed (up to 25 Mb/s) real-time serial communication with the palms FPGA. In order to achieve high modularity and reliability of the hand, a fully mechatronic integration and analog signals in situ digitalization philosophy is implemented to minimize the dimension and number of the cables (five cables including power supply), and protect data communication from outside disturbances. Furthermore, according to the hardware structure of the hand, a hierarchical software structure has been established to perform all data processing and the control of the hand. It provides basic air position indicator (API) functions and skills to access all hardware resources for data acquisition, computation, and teleoperation. With the nice design of the hands envelop, the hand looks more like a humanoid.

A robot arm/hand teleoperation system with telepresence and shared control

This paper describes a master-slave teleoperation system which is developed to evaluate the effectiveness of teleopresence in telerobotics applications. The operator wears a dataglove augmented with an arm-grounded force feedback device to control the dexterous hand and utilizes a spaceball to control robot arm. Contact forces measured by the finger sensors can be feedback to the operator and visual telepresence systems collect the remote operation scenes and display to the operator by a stereo helmet. A primitive autonomous grasp system based on parallel joint torque/position control is developed. The experimental results show that this teleoperation system is intuitive and productive and the primitive autonomous grasp is feasible and efficient

A Five-fingered Underactuated Prosthetic Hand Control Scheme

This paper presents a five-fingered underactuated prosthetic hand controlled by surface electromyographic (EMG) signals. The prosthetic hand control part is based on an EMG motion pattern classifier which combines variable learning rate (VLR) based neural network with parametric autoregressive (AR) model and wavelet transform. This motion pattern classifier can successfully identify flexion and extension of the thumb, the index finger and the middle finger, by measuring the surface EMG signals through three electrodes mounted on the flexor digitorum profundus, flexor pollicis longus and extensor digitorum. Furthermore, via continuously controlling single fingers motion, the five-fingered underactuated prosthetic hand can achieve more prehensile postures such as power grasp, centralized grip, fingertip grasp, cylindrical grasp, etc. The experimental results show that the classifier has a great potential application to the control of bionic man-machine systems because of its fast learning speed, high recognition capability

EMG Control for a Five-fingered Underactuated Prosthetic Hand Based on Wavelet Transform and Sample Entropy

A new five-fingered underactuated prosthetic hand control system is presented in this paper. The prosthetic hand control part is based on an EMG motion pattern classifier which combines VLR (variable learning rate) based neural network with wavelet transform and sample entropy. This motion pattern classifier can successfully identify flexion and extension of the thumb, the index finger and the middle finger, by measuring the surface EMG signals through three electrodes mounted on the flexor digitorum profundus, flexor pollicis longus and extensor digitorum. Furthermore, via continuously controlling single fingers motion, the prosthetic hand can achieve more prehensile postures such as power grasp, fingertip grasp, etc. The experimental results show that the classifier has a great potential application to the control of bionic man-machine systems because of its high recognition capability

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.

EMG Control for a Five-fingered Prosthetic Hand Based on Wavelet Transform and Autoregressive Model

A five-fingered underactuated prosthetic hand controlled by surface electromyographic (EMG) signals is presented in this paper. The prosthetic hand control part is based on an EMG motion pattern classifier which combines Levenberg-Marquardt (LM) or variable learning rate (VLR) based neural network with parametric autoregressive (AR) model and wavelet transform. This motion pattern classifier can successfully identify flexion and extension of the thumb, the index finger and the middle finger, by measuring the surface EMG signals through three electrodes mounted on the flexor digitorum profundus, flexor pollicis longus and extensor digitorum. Furthermore, via continuously controlling single fingers motion, the five-fingered underactuated prosthetic hand can achieve more prehensile postures such as power grasp, centralized grip, fingertip grasp, cylindrical grasp, etc. The experimental results show that the classifier has a great potential application to the control of bionic man-machine systems because of its fast learning speed, high recognition capability

DSP/FPGA-based Controller Architecture for Flexible Joint Robot with Enhanced Impedance Performance

Some practical issues associated with enhancing the Cartesian impedance performance of flexible joint manipulator are investigated. A digital signal processing/field programmable gate array (DSP/FPGA) structure is proposed to realize the singular perturbation based impedance controller. To increase the bandwidth of torque control and minimize the joint torque ripple, boundary layer system and field-oriented control (FOC) are fully implemented in a FPGA of each joint. The kernel of the hardware system is a peripheral component interface (PCI)-based high speed floating-point DSP for the Cartesian level control, and FPGA for high speed (200 us cycle time) multipoint low-voltage differential signaling (M-LVDS) serial data bus communication between robot Cartesian level and joint level. Experimental results with a four-degree-of-freedom flexible-joint manipulator under constrained-motion task, demonstrate that the controller architecture can enhance the robot impedance performance effectively.

A Highly Integrated Joint Servo System Based on FPGA with Nios II Processor

In this paper, FPGA (field programmable gate array) based joint servo system for the HIT/DLR arm has been investigated. A new fully digitized hardware design scheme of a joint servo controller has been presented, which is verified and implemented on one-chip FPGA with embedded NIOS II processor. This scheme not only realizes all sensor data acquisition, SPWM generation and motor vector control, but also realizes joint position, torque control and trajectory generation. Moreover, the realized controller IC also contains a high speed serial (25 Mbps) communication interface based on LVDS (low voltage differential signal), which permits the on-line configuration for all kinds of control parameters. Experimental results demonstrate the effectiveness of the compact joint servo controller for the HIT/DLR arm

Ground verification of space robot capturing the free-floating target based on visual servoing control with time delay

Purpose – The purpose of this paper is to solve the ground verification and test method for space robot system capturing the target satellite based on visual servoing with time-delay in 3-dimensional space prior to space robot being launched. Design/methodology/approach – To implement the approaching and capturing task, a motion planning method for visual servoing the space manipulator to capture a moving target is presented. This is mainly used to solve the time-delay problem of the visual servoing control system and the motion uncertainty of the target satellite. To verify and test the feasibility and reliability of the method in three-dimensional (3D) operating space, a set of ground hardware-in-the-loop simulation verification systems is developed, which adopts the end-tip kinematics equivalence and dynamics simulation method. Findings – The results of the ground hardware-in-the-loop simulation experiment validate the reliability of the eye-in-hand visual system in the 3D operating space and prove the...

The ground-based verification system of visual servoing control for a space robot

Owing to the high cost and risks of robotic tasks in space, space robots require that all procedures should be strictly verified and tested before launching. A ground-based multi-loop simulation verification testbed has been developed which can validate and test the visual servoing system for free-floating space robot to capture the target satellite in 3-dimensional space. The verification testbed which includes the real hardware and the simulation software adopts the method of kinematics equivalence and multi-loop simulation. Finally, the multi-loop simulation experimental results demonstrate the effectness of the ground verification testbed and validate the correctness and accuracy of the eye-in-hand visual servoing system in the 3-dimensional space.