Yuehui Ji

A kinematic model of an upper limb rehabilitation robot system

This paper presents a kinematic model of an upper limb rehabilitation robot system based on Denavit-Hartenberg parameters method. The system possesses advantages of less weight, compact size, and interaction in the rehabilitation process. Furthermore it can provide a sufficient work room for the patients upper limb. This system mainly consists of an upper limb exoskeleton rehabilitation device (ULERD), a haptic device called PHANTOM Premium, and an interactive virtual reality environment. The proposed rehabilitation robot system is a master-slave system. The impaired hand is hard bolted to the ULERD, so the doctor (or the intact hand of patients) can move the stylus of PHAMTOM Premium and guide the injured hand to move along some predefined training track. This paper aims to establish a kinematic model of the rehabilitation robot system. A kinematic model focusing on the ULERD and the PHANTOM Premium is built to ensure the consistency for both the Phantom side and ULERD side. DH-parameters-based modeling can be an effective method in kinematic modeling of a robot.

Characteristics evaluation of a pressure sensitive rubber-based tactile sensor

Pressure sensitive rubber has been proposed to be used as the tactile sensor in robotic catheter system for MIS (minimally invasive surgery). The contact area in the blood vessels can not be clearly known within the current technical level. In this paper, supposing there are three different situations when the sensor contacts the blood vessel wall, including the contact area is one point, the contact area is part of the surface and the contact area is entire surface. This paper analyzes the strain based on FEA (finite element analysis) when the force loading area of pressure sensitive rubber is different. The linearity of pressure sensitive rubber is good on condition that the contact area is constant. Then we change the contact area to do more experiments and learn that the strain increases with the increase of the contact area. Keep contact area as a constant value, we can get an accurate calibration curve of pressure sensitive rubber. In this way, we evaluate the characteristics of the pressure sensitive rubber when it is used in robotic catheter system for MIS as a novel tactile sensor.

A Kinematic Modeling of an Amphibious Spherical Robot System

This paper presents a kinematic model of an amphibious spherical robot through the Denavit-Hartenberg parameters method which will allow us to describe the link to the next or the previous. Then it is going to allow us to precisely define the frames which are going to move with the links, but also allow us to connect with the base through the structure to the end-actuator. Based on the known position and orientation of the robot, a series of kinematics equations are deduced through homogeneous transformation matrix based on the kinematics model and the inverse kinematics and each joint angle can be obtained. The prototype of amphibious robot includes four water-jet propellers and eight servo motors, which can be capable of changing walking mode between water-jet system and quadruped walking system. The walking speed and direction of amphibious robot can be handled by controlling the PWM pulse duty ratio. At last, some gait experiments had been carried out on the flat floor. The results of experiments verified that the model can give important guidance to gait trajectory planning for amphibious spherical robot.

Performance evaluation of the wireless microrobot in pipe with symmetrical spiral structure

A wireless microrobot may be used in the small space and biomedical practice, especially in the industrial field and biomedical application. In this paper, we designed a new kind of wireless microrobot with symmetrical spiral structure, which have more compact volume, completely symmetrical mechanical structure, quick response, forward-backward motions and can clean the dirt adhering to the inner wall. According to the hydromechanical lubrication theory and Newton viscous law, we build the motion model of the microrobot. Through analysis, simulations and experiments, this paper had evaluated the effect of spiral depth and thread unit number. In addition, we verified the feasibility of this new kind of microrobots, and obtained the moving speeds of forward-backward and upward-downward motion in the pipe. The experimental results indicated that the maximum moving speed is 22.68 mm/s at 12 Hz in the horizontal direction and 6.29 mm/s at 13Hz in the vertical direction with input currents of 0.7A. Finally, we designed a control panel for this system, which can control the microrobot current motion states easily, and make our system more portable and compact. The designed wireless microrobot can move smoothly in water and other liquid medium and is very useful in the industrial application and microsurgery application.

Nonlinear path following for Water-jet-based Spherical Underwater Vehicles

A command filtered back-stepping path following control is exploited to design a dynamic state-feedback controller for a Water-jet-based Spherical Underwater Vehicles, which obviates the computation of analytic derivatives in the traditional back-stepping design. The ISS-modular approach provides a simple and effective way for controlling non-linear Underwater Vehicle satisfying the strict-feedback form, simultaneously solving the problem of “explosion of complexity” in conventional back-stepping approach by combining command filtered back-stepping, sliding-mode-based integral filters and Input-to-State Stability (ISS) analysis. The stability analysis of the closed-loop system is verified based on the small-gain theorem. Numerical simulations illustrate the performance of the proposed nonlinear control method.

Development of a symmetrical spiral wireless microrobot in pipe for biomedical applications

Colonoscopy is an important procedure for the diagnosis of various pathologies, in particular cancer of the colon and of the rectum. However, colonoscopy is a procedure often painful for the patient and complex for the doctor. So in the biomedical field, a wireless microrobot in pipe that can move smoothly in water or aqueous medium has urgently been demanded. In this paper, we developed a new kind of wireless microrobot with symmetrical spiral structure, which also had symmetrical kinematic characteristics. According to the hydromechanical lubrication theory and Newton viscous law, we build the motion model of the microrobot, which will provide a theoretical basis on designing the optimal structure parameters of the microrobot. Through analysis, simulations and experiments, this paper had evaluated the effect of spiral angle, which could realize forward-backward, upward-downward motion and stopping at any position we need in the pipe. In addition, we obtained the moving speeds of forward-backward and upward-downward motion in the pipe. The experimental results indicated that the maximum moving speed is 36.5 mm/s at 14 Hz in the horizontal direction and 4.6 mm/s at 16Hz in the vertical direction with input currents of 0.7A. Finally, we designed a control panel for this system, which can control the microrobot current motion states intuitively and easily, and make our system more portable and compact. The developed wireless microrobot can move smoothly in water and other liquid medium and is very useful in the industrial.

A novel wavelet denoising method used for droplet volume detection in the microfluidic system

Microdroplet is found increasing use in the production of nanoparticles, chemical reactions and drug research and development. However, only some simple theory of droplet information is studied, automate droplet is the direction in the future. Size of droplet is detected in order to control the flow of the microfluid in automation droplet system. Image collected by image acquisition system has severe noise and denoising is the most important step. This paper describes a new wavelet threshold function to improve the wavelet threshold denoising. This approach successfully denoises the noise in the image. Compared with traditional wavelet threshold denoising, this approach has enormous improvements in objective evaluation of denoising such as Peak Signal Noise Ration (PSNR). With the demand of constant accurate flow in microfluidic system, the approach to measure droplet is in urgent need. The obtained results are in good agreement with the demand. The method is used to detect the radius of droplets in the microfluidic system. If dust or spot images are directly processed with noisy bring out error result even not able to be detected. Better results are achieved after processed by the approach in this paper. That boots application of microfluidic system in field of pharmacy, microchemistry, biochemistry and bioanalysis.

Image processing-based measurement of volume for droplets in the microfluidic system

This paper describes a new approach on the measurement of droplets volume in microfluidic system based on image processing. This approach successfully detects the diameter of a single droplet. Image processing via MATLAB is used to capture droplets volume in the microfluidic system. Compared with other methods, this approach has enormous advantages of real-time, simpleness and wide applications. Because of the demand of constant accurate flow in microfluidic system, the approach to measure volume of microfluid is in urgent need. The accuracy of the volume measurements is limited by the selected parameters of the image processing. During the experiment, the optimum parameters of the image processing are selected through repeated tests. The obtained results are in good agreement with the demand. The results show that microfluid can be controlled in quantitative. That makes an important application field of micro fluidic is in pharmacy, microchemistry, biochemistry and bioanalysis.

The underwater motion simulation of a spherical amphibious robot

Spherical amphibious robots, as a kind of novel robot, are being studied by researchers. Underwater analysis is an important field in underwater robot research. Underwater movement of the robot which this article mentioned is accomplished by interaction of servo motor and hydraulic motor. This paper presents the investigation of hydrodynamic performance of spherical amphibious robot with two essential motions, vertical motion and horizontal motion. Gambit 2.4.6 is employed to establish the 3D models and mesh. Meanwhile, simulation calculation and analysis of two models is implemented by Computational fluid dynamics (CFD) code, FLUENT 6.3.26. Finally, the velocity vectors, pressure contours, drag coefficient as well as force report for two states of motion are gained. Resistance of the report data shows that the robot is mainly subjected to differential pressure resistance.

Modeling of muscle forces around the elbow in the RITS

Muscle forces modeling and computation around the elbow are focused on in this paper when the elbow flexing and extending in the sagittal plane. The paper introduces a Rehabilitation Intelligent Training System (RITS) for restoration of motor function. The system has advantages of small size, less weight and interaction during the rehabilitation process. Furthermore, this system mainly consists of a force feedback device called PHANTOM Premium 1.5, ULERD, EEG (Electroencephalogram) based Brain-Computer Interfaces (BCI). The impaired hand wears the ULERD, so the therapist can control and move the injured hand by PHANTOM Premium in tele-operation. If the force feedback from PHAMTOM Premium is similar to the force generated by the muscle force of upper limb, the effect of upper limb rehabilitation to restore elbow motion may be suitable and satisfactory. This paper aims to computing the natural muscle forces and realizing the force which is generated by PHAMTOM and close to the computed one. Experiment has been performed to prove that the method is feasible in such robots. The development of this method can be a promising approach for further research in more effective rehabilitation to the elbow joint.