Obstacle avoidance planning for redundant manipulator based on variational method

U svrhu smanjenja prekomjernog pomicanja zglobova, u radu se predlaže nova metoda za izbjegavanje prepreka kod redundantnog manipulatora. U toj smo metodi dizajnirali funkcionalnu procjenu pokreta kako bismo dobili najkraću stazu kretanja zgloba manipulatora i dobili indeks optimizacije vektora gradijenta primjenom varijacijske (variational) metode da bi za vrijeme izbjegavanja prepreke kretanje zgloba bilo minimalno. U međuvremenu, kako bismo izbjegli neuspjeh algoritma za izbjegavanje prepreke ili prekoraćenje krajnjih granica zglobova, do kojih je došlo zbog velike razlike između solucije najmanje norme i homogene solucije kinematike inverzne brzine manipulatora, u radu je primijenjena kontinuirana funkcija 2-norme da bi se dinamički podesio homogeni faktor rješenja metode projekcije gradijenta. Da bi se provjerila ispravnosti u radu predložene metode izbjegavanja prepreka, provedeni su simulacijski eksperimenti na 7-DOF redundantnom manipulatoru. Rezultati pokazuju da u usporedbi s tradicionalnom metodom projekcije gradijenta za izbjegavanje prepreka, u radu predloženim algoritmom smanjio se pomak zgloba 1 do zgloba 6 za 38,3 %, 83,3 %, 3,81 %, 7,85 %, 50,1 % i 45,6 %, a cjelokupni pomak prizmatičkih zglobova i okretnih (revolute) zglobova za 62,2 % i 26,4 %. U isto vrijeme, promjena brzine i ubrzanja zgloba 1 do zgloba 6 između početnog i završnog vremena tijekom izbjegavanja prepreke smanjila se 43,2 %, 97,3 %, 2,23 %, 36,6 %, 96,7 %, 72,7 % (brzina) i 91,04 %, 98,28 %, 73,33 %, 98,40 %, 93,86 % i 91,94 % (ubrzanje). Ispitivanje je pokazalo da je predložena metoda za izbjegavanje prepreka temeljena na varijacijskoj metodi, izvediva i praktična.To reduce the excessive joints movement, this paper proposed a new obstacle avoidance method for a redundant manipulator. In this method, we designed the performance evaluation functional to realize the shortest joints motion path of manipulator, and deduced the gradient vector optimizing index by variational method to make the joint movement minimum during obstacle avoiding. Meanwhile, in order to avoid the obstacle avoidance algorithm failure or joints exceeding their limits, which arose from the great difference between least-norm solution and homogeneous solution of velocity inverse kinematics of the manipulator, this paper used 2-norm continuous function to adjust homogeneous solution factor of gradient projection method dynamically. To verify the validity of the proposed obstacle avoidance method in the paper, simulation experiments were conducted on a 7-DOF redundant manipulator. The results show that, compared to the traditional gradient projection method for obstacle avoidance, the proposed algorithm in this paper has decreased the displacement of joint 1 to joint 6 by 38,3 %, 83,3 %, 3,81 %, 7,85 %, 50,1 % and 45,6 % respectively, and the total displacement of prismatic joints and revolute joints has reduced 62,2 % and 26,4 %. At the same time, the changes of joint 1 to joint 6’s velocity and acceleration between initial time and final time during obstacle avoiding has been decreased 43,2 %, 97,3 %, 2,23 %, 36,6 %, 96,7 %, 72,7 % (velocity) and 91,04 %, 98,28 %, 73,33 %, 98,40 %, 93,86 % and 91,94 % (acceleration) respectively. The test validated that the proposed obstacle avoidance method based on variational method is feasible and practicable

Research on Design Optimization of Offshore Booster Stations

[Introduction] In recent years, China has put into operation a large number of offshore booster stations and accumulated rich experience in the construction and operation of offshore booster stations. Based on these experiences, it is found that the current design of offshore booster stations has certain problems, such as relatively simple analysis of operation mode, general load of air conditioning power supply in important equipment rooms, the "unattended" design concept of offshore booster stations does not conform to reality, and inadequate consideration of environmental protection requirements. The design of offshore booster station still has new optimization space. [Method] The experience feedback of several offshore wind farms in the construction and operation stage in recent years were analyzed and the relevant of standards at home and abroad was studied. [Result] Design optimization suggestions are put forward for the operation mode, HVAC load classification of important equipment rooms, personnel duty form of offshore booster station. [Conclusion] The design optimization suggestions of offshore booster station summarized in this paper can be used as a reference for subsequent design of new offshore booster station

Intelligent control of biped robot with heterogeneous legs

Intelligent bionic leg (IBL) is important for above-knee amputees. Biped robot with heterogeneous legs (BRHL) including artificial leg and bionic leg is proposed as a good test-bed for IBL. Mechanism and virtual prototype of BRHL is designed and built. Model of BRHL is established. Based on the complex differential algebraic equation of bionic leg, computed torque and PD feedback control of joint angle are introduced for gait tracking. The iterative learning control is applied in conjunction with computed torque and PD control law for good tracking performance. Control simulation is done and shows intelligent control is good for BRHL. Copyright © 2005 IFAC

A Simplification Method for Point Cloud of T-Profile Steel Plate for Shipbuilding

According to the requirements of point cloud simplification for T-profile steel plate welding in shipbuilding, the disadvantages of the existing simplification algorithms are analyzed. In this paper, a point cloud simplification method is proposed based on octree coding and the threshold of the surface curvature feature. In this method, the original point cloud data are divided into multiple sub-cubes with specified side lengths by octree coding, and the points that are closest to the gravity center of the sub-cube are kept. The k-neighborhood method and the curvature calculation are performed in order to obtain the curvature features of the point cloud. Additionally, the point cloud data are divided into several regions based on the given adjustable curvature threshold. Finally, combining the random sampling method with the simplification method based on the regional gravity center, the T-profile point cloud data can be simplified. In this study, after obtaining the point cloud data of a T-profile plate, the proposed simplification method is compared with some other simplification methods. It is found that the proposed simplification method for the point cloud of the T-profile steel plate for shipbuilding is faster than the three existing simplification methods, while retaining more feature points and having approximately the same reduction rates

Gait perception and coordinated control of a novel biped robot with heterogeneous legs

This paper presents gait perception and coordinated control of a Biped robot with heterogeneous legs (BRHL), which is a new type of humanoid robot. This paper first introduces the concepts and research objectives of a BRHL. Then configuration of a BRHL is discussed in detail. The coordinated dynamics model and MR damper model are given. Rules based on gait perception are introduced. In the end, this paper discusses the control structure of a BRHL. Simulation and prototype of a BRHL are discussed. The research indicates that intelligent bionic leg controlled by MR damper can track artificial leg\u27s gait well. A BRHL provides an ideal test-bed for advanced intelligent prosthesis. © 2006 IEEE

Path Planning for Detection Robot Climbing on Rotor Blade Surfaces of Wind Turbine Based on Neural Network

Two-feet climbing robot is proposed for rotor blade surface damage detection. The penalty function is designed based on the simulated annealing neural network for waypoints inside blade. According to the derivative of path energy function to time, waypoints are updated and move toward the direction reducing the path energy consisting of length and penalty function. According to the curvature variation range, a novel weighted simulated-annealing-temperature updating method is designed to get comprehensive optimization of the path energy and convergence speed. The path planning is accomplished for the root, middle, and tip blade parts, respectively. The asymptotic analysis of the waypoint coordinating updating process was given, and the updated start point is adopted during escaping from inside. The effect of weight on path energy and convergence speed is analyzed. The planning results show the effectiveness of the proposed path planning algorithm, and the weighted average method is valid for the comprehensive optimization

Multi-sensor fusion positioning of detection robot for tailings pond flood discharge tunnel

The environment in the flood discharge tunnel of tailings pond is complex, and the existing positioning algorithm of detection robot has the problem of positioning failure in weak texture indoor scene, which is difficult to be applied to the precise positioning and accumulative error elimination of detection robot in this kind of environment. In order to solve the above problems, a multi-sensor fusion positioning algorithm of detection robot for tailings flood discharge tunnel is proposed. Based on the odometry method and graph theory, the algorithm simplifies the long-distance positioning in the flood discharge tunnel environment to multi-segment short-distance positioning by using the ArUco code. Firstly, the odometer is calibrated by UMBmark algorithm, which effectively eliminates two types of system errors of wheel diameter and axle diameter. Secondly, the extended Kalman filter (EKF) algorithm is used to fuse the information of the odometer and the inertial measurement unit (IMU), and the odometry method is used to realize the calculation of the position and attitude information of the detection robot during the movement process. Finally, the ArUco code is used as a road sign and fixed inside the tunnel. The detection robot carries the calibrated camera to identify and process the ArUco code information. The robot uses the measurement values of each sensor to form constraints, and combines constraints with the graph optimization method to achieve position and attitude optimization. And according to the information carried by the ArUco code, the accumulative error is eliminated so as to realize the long-distance high-precision positioning of the detection robot in the narrow and long space and weak texture scene. The multi-sensor fusion positioning algorithm is operated and closed in the actual scene of the tailings pond flood discharge tunnel, and 10 groups of repeated positioning experiments traveling 40 m are carried out respectively. The results show that the multi-sensor fusion positioning algorithm has high stability and precision, can correct the accumulative error effectively and realize the precise positioning of the detection robot in the flood discharge tunnel environment. The average positioning error of traveling 20 m is 19.77 cm, the average positioning error of traveling 40 m is 21.23 cm, and the average corrected error of traveling 20 m is 4.2 mm

Design of control system and motion analysis of vision capture for small hexapod robot

Aiming at the difficulties in motion control and performance analysis of hexapod robot, stm32 embedded processor is used to drive the 18-channel steering gear control board to control the robot's motion. CAM Shift algorithm is designed to track the centroid target of the moving robot and calculate the motion speed. The gait experiment and performance analysis of straight line and steering were carried out on the self-developed prototype. The results show that the design integrates the machine vision tracking technology and the motion control technology of the hexapod robot, which can realize the control and motion analysis functions

Design and Passive Training Control of Elbow Rehabilitation Robot

In this paper, a rehabilitation robot driven by multifilament muscles is designed based on the rehabilitation robot motion model and a system elbow joint model. The passive training mode of rehabilitation robots were researched, and active disturbance rejection control (ADRC) leveraged to improve the tracking angle of robot joints. In the no-load motion simulation of rehabilitation robots, disturbances are added to the control variables to complete the ADRC and Proportional Integral Differential (PID) position control simulation. The simulation results indicate that the auto disturbance rejection control can quickly keep up the expected signal without overshoot, solve the contradiction between the system rapidity and overshoot. Moreover, it can better suppress the interference even if the external load changes. The upper limbs of the human body are used as the load on the robot body to complete the simulation of ADRC and PID position control objects of different weights. Finally, a passive rehabilitation training experiment was conducted to verify the safety of the rehabilitation robot, the rationality, comfort, and robustness of the mechanism design, and the effectiveness and feasibility of the ADRC

Modeling Contact Stiffness of Soft Fingertips for Grasping Applications

Soft fingertips have distinct intrinsic features that allow robotic hands to offer adjustable and manageable stiffness for grasping. The stability of the grasp is determined by the contact stiffness between the soft fingertip and the object. Within this work, we proposed a line vector representation method based on the Winkler Model and investigated the contact stiffness between soft fingertips and objects to achieve control over the gripping force and fingertip displacement of the gripper without the need for sensors integrated in the fingertip. First, we derived the stiffness matrix of the soft fingertip, analyzed the contact stiffness, and constructed the global stiffness matrix; then, we established the grasp stiffness matrix based on the contact stiffness model, allowing for the analysis and evaluation of the soft fingertip’s manipulating process. Finally, our experiment demonstrated that the variation in object orientation caused by external forces can indicate the contact force status between the fingertip and the object. This contact force status is determined by the contact stiffness. The position error between the theoretical work and tested data was less than 9%, and the angle error was less than 5.58%. The comparison between the theoretical contact stiffness and the experimental results at the interface indicate that the present model for the contact stiffness is appropriate and the theoretical contact stiffness is consistent with the experiment data