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[Objective] Reduce the running time and impact of Delta robot in food sorting trajectory, improve the efficiency and stability of Delta robot operation. [Methods] Based on the analysis of the food sorting system (using Delta robots), a Delta robot food sorting trajectory optimization method was proposed, which combined NURBS algorithm, sparrow search algorithm and butterfly optimization algorithm. Optimizing the running trajectory of Delta robot for NURBS curve planning with the goal of minimizing running time and impact, combining sparrow search algorithm and butterfly optimization algorithm to solve the model, which realized the optimization of Delta robot sorting trajectory. [Results] The proposed Delta robot sorting trajectory optimization method could balance running time and impact, reduce running time by more than 6.00% and running impact by more than 80.00%. The dynamic grasping success rate of the system was over 99.00%, which could meet the requirements of food sorting. [Conclusion] Optimizing NURBS curves through a combination of runtime and impact optimization can effectively improve the food sorting performance of Delta robots. [ABSTRACT FROM AUTHOR]

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Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: To solve the problems of low efficiency and poor motion stability of DELTA robots in the tomato sorting process of existing tomato processing production lines. Methods: Based on the analysis of the DELTA robot sorting system, the optimized gate shaped trajectory of the cyclotron was used for DELTA robot trajectory planning. By replacing the right angle part of the gate shaped trajectory with a convolutional line, an optimization model with the goal of time optimization was established. The optimized parameters of the gate shaped trajectory were solved using an improved ant colony optimization algorithm. Analyzed its performance through experiments. Results: The proposed method had better average sorting time and sorting success rate compared to the gate shaped trajectory and other methods, with an average sorting time reduction of 11.61% and 1.63%, respectively, and a sorting success rate increase of 2.05% and 0.56%. Conclusion: The proposed planning method effectively improves the sorting accuracy and efficiency of DELTA robots.

Objective: In order to solve the problems of poor accuracy and low efficiency of delta robot in dynamic target grasping in current food production. Methods: A new dynamic target grasping method was proposed for the grasping control of delta robot in food production line. The dynamic position of the target was calculated through the offset of the conveyor belt and the feedback value of the encoder, and the grasping order of the target was optimized. The dynamic target was grasped by combining the door trajectory and the improved trapezoidal acceleration and deceleration algorithm. The control methods before and after optimization were analyzed through experiments. Results: At the conveying speed of 20 mm/s, the missed grasping rate of the robot before and after optimization decreased from 3.33% to 0, and the grasping speed increased from 0.756 s-1 to 0.860 s-1. At the conveying speed of 30 mm/s, the missed grasping rate of the robot before and after optimization was reduced from 8.83% to 0, and the grasping speed was increased from 0.885 pieces/s to 1.130 pieces/s. Conclusion: The dynamic target grasping method can effectively improve the grasping efficiency of delta robot.

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: In order to solve the problems of low efficiency and poor precision of parallel robot in food sorting. Methods: Based on the structure of the food sorting system, a moving target grasping strategy of delta robot based on Improved BP neural network and PID control is proposed. The improved particle swarm optimization algorithm is used to optimize the initial weight of BP neural network, and the optimized BP neural network is used to adjust the PID control parameters in real time. The performance of this method is analyzed by experiments, and its superiority is verified. Results: Compared with traditional control methods, the proposed method can achieve dynamic target capture more accurately and efficiently, and the success rate of dynamic capture is more than 98%, which can meet the needs of food sorting. Conclusion: The grasping efficiency and accuracy of delta robot can be effectively improved by optimizing the grasping strategy of moving target.

Objective: Solve the problems of poor positioning accuracy and low grasping success rate of the Delta robot in food sorting, and improve the robot's flexible grasping ability. Methods: Based on the existing binocular vision and delta robot technology, a flexible grasping method of delta robot based on binocular vision was proposed. Zhang Zhengyou calibration method was used to calibrate the camera, the target was identified and located by Hough transform at the chord midpoint, and the delta robot was controlled to grasp the dynamic target according to PID tracking and grasping. The feasibility of this method was verified by analyzing the performance of single target sorting and multi-target sorting. Results: This method can accurately, quickly and stably grab the target dynamically （success rate was above 94.0%）. Conclusion: The combination of binocular vision and delta robot can effectively improve the positioning accuracy of the robot and the success rate of sorting and grasping.

In order to improve the accuracy and stability of the robot in the process of high-speed motion， the method of modeling the dynamic equation of the 4-DOF Delta high-speed parallel robot is studied. The geometrical method is used to solve the inverse kinematics equation of the robot， and the Kane method of screw theory is combined to establish the dynamic equation of the robot. Matlab programming is used to solve the kinematics and dynamics models， and the displacement， velocity， acceleration and torque curves of the driving arm are drawn. The dynamics control system of the Delta robot is established in Simscape， and the displacement curve of the driving arm is obtained with torque as input. Comparing the calculation and simulation results， the correctness of the dynamic equation is verified.

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is significant for Delta robot design to research on the work characteristics of the whole reachable workspace. The closed-loop vector equation is taken to solve the inverse kinematics of Delta robots， and vector expression of Jacobian matrix is deduced， the global stiffness index and the global dexterity index is established. The relationship between stiffness index and transmission angles of branched chains is obtained and verified， which make it possible to predict the stiffness performance by transmission angles. On the basis of the workspace and Jacobian matrix， the global stiffness index and the global dexterity index in the whole reachable workspace of two Delta robots with different configurations is obtained by Matlab， and the mechanism of the work characteristics difference between two kinds of Delta robots is researched. The conclusion shows that with the similar volume of reachable workspace， the stiffness of the linear Delta robot is superior to the rotational Delta robot， while the kinematics performance of the rotational Delta robot is better.

In order to give full play of the advantages of error accumulated small and fast running speed of the high speed Delta robot,the research of bar optimization for the Delta robot is need. Based on establishing the kinematics and dynamics of rigid body model of the system,the global dexterity and the shock vibration function of driving arm are defined,according to the actual work requirements of the Delta robot,the work trajectory is planned. By using MATLAB genetic algorithm toolbox,respectively with dexterity and shock and vibration function as fitness function,the optimal solution of global is got. Then,taking the obtained optimal solution as the upper and lower bounds,by using the weight factor transformation method,the multi- objective optimization of dexterity and shock vibration function is transformed into a single objective optimization,then according to the above method,a set of meet the scale parameter optimization objectives are synthesized,a reference for the Delta robot structure optimization design is provided.

Aiming at the problem of elastic deformation in Delta robot motion, the elastic dynamic model was established based on the finite element theory. According to characteristics of the structure, the components of the robot were divided into rigid parts and flexible parts, respectively, which consist of a rigid-flexible coupling system. The motion relation of the parallelogram structure was fully considered, and the motion compatible matrix of each component was deduced. Then the elastic dynamic equation of the system was obtained, on which was based, the influence of the cross-sectional dimension of Delta parallel robot’s rods on the elasticity error in motion was analyzed. The results indicate that the bending stiffness increases with the increase of the cross section size of the drive rod, elastic deformation of the robot can be reduced. And the self - weight increases with the increase of the cross section size of the driven rod, which makes the deformation greater. [ABSTRACT FROM AUTHOR]

For the economical and practical parallel robot, there exists joint clearance in its mechanical structure, and the effect of joint clearance on the position precision of the moving platform and the vibration characteristics of the system can not be ignored. In order to analyze the problem, taking Delta robot as the study object, this paper puts forward a new thought that studies the elastic dynamic model with joint clearance and the vibration characteristics of the system. In the process of analysis, knowing that the joint clearance changes with the change of the robot motion state, which is random, the mathematical statistics principle is used innovatively to analyze the kinematics of the branched chain of Delta robot with joint clearance, and the mathematical expectation of joint clearance vector's probability density in the joint coordinate system is used to express joint clearance's numerical value quantitatively before the collision between shaft and shaft sleeve. Then, because the joint clearance is narrow, ignore the acceleration inertia force of the shaft in shaft sleeve, and only consider the collision force and the friction when shaft and sleeve collide. The probability that the shaft hits arbitrary point on the inner wall of the shaft sleeve is the same and obeys the normal distribution, and on the basis of this theory, combining with the Lankarani-Nikravesh collision contact force model and the Coulomb friction model with dynamic correction coefficient, the generalized collision force of joint clearance is studied. By using the finite element theory and the Lagrange equation, fully considering the active arm and the driven arm's spatial dynamic characteristics and motion coordination, the Delta robot system's elastic dynamic model is established. Based on the definition of bar virtual length, the generalized collision force produced by joint space is combined with the elastic dynamics model, the Delta robot elastic dynamic model with joint clearance is established. The system clearance elastic dynamic model is highly nonlinear time varying equation group, and for the characteristics of the equation group, the time discretization method is used to solve the problem, by using the Newmark algorithm with high stability, accuracy and computational efficiency. Then, with the aid of the FARO laser tracker, the clearance elastic dynamic model is verified, and the vibration characteristics of the Delta robot is analyzed by using the hammer impulse method and the simulation of the Workbench software. Experimental results show that the moving trajectory of the center point of the moving platform when considering the joint clearance is closer to the experimental results than that without the consideration of joint clearance. Then, the rationality and correctness of the clearance elastic dynamic model are verified, and the relative errors between theoretical and experimental values of the non zero natural frequency of the first 2 orders are 3.544% and 12.026%, respectively. The two results are very close, which also indirectly proves the correctness of the theoretical derivation of the clearance elastic dynamic model. In addition, from the simulation results it can be found that the 3 groups of subordinate moving arms are the weakest link in the whole Delta robot system. The study can provide a reference for economical and practical parallel robot's position error compensation and system vibration reduction optimization. [ABSTRACT FROM AUTHOR]