Guanjun Bao

Research on novel flexible pneumatic actuator FPA

A novel flexible pneumatic actuator FPA is proposed in this paper. The structure and properties of FPA are described. Based on FPA, flexible pneumatic bending joint, flexible pneumatic torsion joint and flexible pneumatic spherical joint are developed. The mathematical models of flexible pneumatic bending joint and flexible pneumatic spherical joint are established. Experiments are carried out to investigate the characteristics of these two joints by utilizing intelligent control techniques. Experimental results demonstrate that flexible pneumatic bending joint and flexible pneumatic spherical joint can meet the designed requirement of application. Finally, the aim and direction of the future work are forecasted.

Static Model of Flexible Pneumatic Bending Joint

Flexible pneumatic bending joint is a new type of joint based on FPA, which can be adopted in multi-fingered dexterous hand design. The changing of average radius and shell thickness of bending joint during movement are analyzed, which implies that the average radius is almost invariable while the shell thickness changes obviously. The static model of bending joint is established based on principle of moment equilibrium, and was validated by experiment. Experimental result indicates that the theoretical model can basically describe the static properties of bending joint. Finally, the reasons of error between theoretical curve and experimental data are discussed

Multi-template matching algorithm for cucumber recognition in natural environment

A multi-template matching library was established by proportional scaling and rotating the standard cucumber image.Multi-template matching algorithm for cucumber recognition for harvesting robot was developed.High recognition accuracy of 98% was obtained from the verification test. The automatic recognition of cucumber target within its cultivating environment is one of the key techniques for the cucumber harvesting robot. Since cucumber grows in the complex environment and its color is similar to that of branches and leaves, it is quite challenging to achieve high identification accuracy when employing algorithms based on color features, image segmentation and shape features. Adopting spectroscopy can simplify the algorithm. However it increases the complexity and cost of the robot system. The multi-template matching method was proposed to solve this problem in this paper. A multi-template matching library, which contained 65 cucumber images, was established based on the statistical parameters of the matured Radit cucumber, by proportional scaling the standard cucumber image with step of 0.1 in the range of 0.8, 1.2 and rotating with step of pi/36 in the range of -pi/6, pi/6. To identify the cucumber in the visual field of the robot, cucumber templates in the library are used to calculate the matrix of normalized correlation coefficients (NCC) with the target image, one after another. If the maximum NCC is above the threshold, there is the target cucumber in the image frame. Otherwise, there is no target in the visual field. To verify the algorithm, 100 photos of the Radit cucumber with different size and angle were sampled in the test. The results indicated that cucumbers were correctly recognized and positioned in 87 images. Cucumbers which were correctly recognized but with picking position deviation appeared in 11 images. Cucumbers were not found in two images. In general, the correct recognition accuracy is 98%, with 11% fault position.

Navigation line detection based on robotic vision in natural vegetation-embraced environment

In order to detect navigation line for agricultural vehicles in natural vegetation-embraced environment, a method was presented based on robotic vision. Firstly, an improved region growing algorithm was introduced to segment path. Then the two edges of path were extracted and an array of points through the center was computed. Lastly, the guidance line for vehicles to follow was obtained by Hough transform. The method was also extended to forestry environments and tall-crop fields where planting is discretely spaced. Difference was that the two edges of a path were square-fitted to offset edge imperfections. Batch processing of images under Matlab shows logicalness and steadiness of this method and its extensive appliance in various scenarios.

A Dynamic Threshold Segmentation Algorithm for Cucumber Identification in Greenhouse

Aiming at realizing cucumber identification and location for cucumber harvesting robot in greenhouse, a segmentation algorithm for cucumber image was presented. Using M (M=2G) component as the threshold segmentation channel, choosing an initial threshold to segment the images. The threshold was dynamic revised based on shape characteristics of cucumber fruits after the initial segmentation threshold was judged. The pixel region which did not belong to fruit was removed by erosion and dilation using structure elements. Final segmentation images were obtained after region marking. Thirty images were tested to verify the correctness of the algorithm, and twenty-three images were segmented correctly with satisfactory results. Experimental results show that the segmentation success rate is 76.7%, and the segmentation effect is acceptable which can be used in greenhouse cucumber identification.

Pneumatic squirming robot based on flexible pneumatic actuator

The design of a kind of pneumatic squirming robot is presented. It is based on the use of flexible pneumatic actuator. The flexible pneumatic actuator was made of caoutchouc. Its working principle is described. The structure, working principle, pneumatic and electrical control system of the pneumatic squirming robot are designed. All of the actuators driving and squirming parts are composed of pneumatic elements. The vacuum osculums, which act as feet, are connected to the flexible pneumatic actuator. When the vacuum pumps operate, vacuum will be produced in the corresponding osculums, which can adsorb on the contacting surface and orient the robot. The actuator, operating under air pressure, drives the robot. By controlling the vacuum pumps and the actuator, straight and bending squirming of this robot can be obtained.

Influences of electric-hydraulic chattering on backward extrusion process of 6061 aluminum alloy

The possibility of the electric-hydraulic chattering technology and its application in the cold extrusion were presented. The conventional and electric-hydraulic chattering assisted backward extrusion processes were performed on 6061 aluminum alloy billets at room temperature. The experimental results showed that 5.65% reduction in the extrusion load was attained if the die and ejector were vibrated at a frequency of 100 Hz and amplitude of 0.013 mm in the longitudinal direction. The friction coefficient at the billet and tool system interface determined from the finite element analysis (FEA) decreased from 0.2 without chattering to 0.1 with application of electric-hydraulic chattering. The higher values of instantaneous velocity and direction change of material flow were achieved during the chattering assisted backward extrusion process. The strain distribution of the chattering assisted backward extrusion billet revealed lower maximum strain and smoother strain distribution in comparison with that produced by the conventional extrusion method.

Development and simulation of ZJUT hand based on flexible pneumatic actuator FPA

Based on flexible pneumatic actuator FPA, two new kinds of pneumatic rigid-flexible joints are proposed. Three bending joints and one side-sway joints are used for designing two kinds of 4-DOF robot fingers. When inflating the FPA of each joint of 4-DOF fingers with different compressed air pressure, the fingers can simulate human fingers and realize bending movement and side-sway movement. Then the 20-DOF robot multi-fingered dexterous hand composed five fingers and a palm is designed which is named ZJUT Hand. Driving directly by FPA is ZJUT Hands most notable characteristic. Because of this, ZJUT Hand has many advantages such as good adaptability, simple structure, small size and little energy loss and so on. At last, simulation experiments are carried to verify the grasping ability of ZJUT Hand. Simulation experimental results show that ZJUT Hand can complete power grasp and precision grasp for objects with different size and shape.

Research on output force of flexible pneumatic bending joint

In order to eliminate twisting deformation of the flexible pneumatic bending joint, a rigid chain component is designed for it. Compressed air is filled into the pneumatic bending joint, the deformation of rubber tube occurred near the grasping point, and then the force is outputted by the pneumatic bending joint. The characteristics of the output force of the pneumatic bending joint are analyzed from the view of static mechanics, and the mathematic model is built up. Simulation experiment illustrates that the output force of the pneumatic bending joint increases with the air pressure inside the pneumatic bending joint, but the relation between them is nonlinear. But the output force is determined by the value of the air pressure, which means that the output force is controllable. The simulation also shows that the output force of the pneumatic bending joint is relatively small.

Kinematics Model and Simulation of 5-DOF Finger Based on Flexible Pneumatic Actuator

Based on flexible pneumatic bending joint and flexible pneumatic spherical joint, a kind of flexible pneumatic 5-DOF finger is proposed, which is composed of two bending joints and a spherical joint. The mathematic model of flexible pneumatic spherical joint is further analyzed. On the researching foundation of flexible pneumatic bending joint and flexible pneumatic spherical joint, the kinematics equation of the 5-DOF finger is deduced. And the redundancy problem of the inverse kinematics solution is resolved by genetic algorithm. The simulation experiment illustrates that genetic algorithm for solving of inverse kinematics is feasible and effective.