Multi-joint Robot Research Articles

Robust Tracking Control of Multijoint Robots based on Adaptive Fuzzy Observer

Robust Tracking Control of Multijoint Robots based on Adaptive Fuzzy Observer

A Workspace Visualization Method for a Multijoint Industrial Robot Based on the 3D-Printing Layering Concept

The workspace of a robot provides the necessary constraint information for path planning and reliable control of the robot. In this paper, a workspace visualization method for a multijoint industrial robot is proposed to obtain a detailed workspace by introducing the 3D-printing layering concept. Firstly, all possible joint-angle groups of one pose in the joints’ ranges are calculated in detail according to the POE (product of exponential) theory-based forward-kinematics expressions of the multijoint industrial robot. Secondly, a multisolution selection method based on the key degree of the joint is proposed to select the appropriate joint-angle groups. The key degrees of all joints and their key order are obtained according to the sensitivity expressions of all joint angles, calculated from the Jacobian matrix of the robot. One principle based on the smallest differences of the nominal angle is established to select the possible solutions for one joint from the possible solutions for the joint with the smaller key order. The possible solutions for the joint with the highest key order are the appropriate joint-angle group. Thirdly, a workspace visualization method based on the layering concept of 3D printing is presented to obtain a detailed workspace for a multijoint industrial robot. The boundary formula of each layer is derived by forward kinematics, which is expressed as a circle or a ring. The maximum and minimum values of the radius are obtained according to the travel range of the joint angles. The height limitations of all layers are obtained with forward kinematics. A workspace boundary-extraction method is presented to obtain the array of path points of the boundary at each layer. The proposed postprocessing method is used to generate the joint-angle code of each layer for direct 3D printing. Finally, the effectiveness of the multisolution selection method and the workspace visualization method were verified by simulation and experiment.

Towards a next-generation production system for industrial robots: A CPS-based hybrid architecture for smart assembly shop floors with closed-loop dynamic cyber physical interactions

Given the multiple varieties and small batches, the production of industrial robots faces the ongoing challenges of flexibility, self-organization, self-configuration, and other “smart” requirements. Recently, cyber physical systems have provided a promising solution for the requirements mentioned above. Despite recent progress, some critical issues have not been fully addressed at the shop floor level, including dynamic reorganization and reconfiguration, ubiquitous networking, and time constrained computing. Toward the next generation production system for industrial robots, this study proposed a hybrid architecture for smart assembly shop floors with closed-loop dynamic cyber physical interactions. Aiming for dynamic reorganization and reconfiguration, the study also proposed modularized smart assembly units for the deployment of physical assembly processes. Enabling technologies, such as multiagent system (MAS), self-organized wireless sensor actuator networks, and edge computing, were discussed and then integrated into the proposed architecture. Furthermore, a multijoint robot assembly process was selected as a target scenario. Thus, an MAS was developed to simulate the coordination and negotiation mechanisms for the proposed architecture on the basis of the Java Agent Development Framework platform.

The frame optimization and validation of resistance spot welding gun

Resistance spot welding gun is generally used to bond parts in the automotive and consumer electronics industries. In the automotive industry, chassis assembly operations use resistance spot welding. High production speeds allow for mass production and automation, resulting in diverse uses of resistance spot welding. To automate the welding process, it is mounted on a multi-joint robot and the welding gun is designed considering the specifications of the robot. High-strength structural design is needed to prevent deformation during pressurization, but the weight of the weld gun affects the efficiency of the robot. For this reason, it is necessary to design a welding gun with high stiffness and light weight. In this study, the analysis is carried out to measure the stress and deformation amount of weld gun. Optimization for weight reduction is performed by genetic algorithm method and topology optimization. The optimization of the resistance spot weld gun frame is performed, and the optimized model is verified through experimental verification. The production cost of industry has been reduced through the high stiffness and light weight of welding gun.

Validation of Control with Contact Force Distribution for Multi-joint Wearable Robot for Body Trunk Assist

Validation of Control with Contact Force Distribution for Multi-joint Wearable Robot for Body Trunk Assist

Central pattern generator-based coupling control method for synchronously controlling the two-degrees-of-freedom robot.

Synchronous control is a fundamental and significant problem for controlling a multi-joint robot. In this article, by applying two coupled Rayleigh oscillators as the referred central pattern generator models for the two joints of a two-degrees-of-freedom robot, the central pattern generator-based coupling control method is proposed for controlling the two-degrees-of-freedom robot's joints. On these bases, the co-simulation model of the two-degrees-of-freedom robot with the proposed central pattern generator-based coupling control method is established via ADAMS and MATLAB/Simulink, and the performance of the central pattern generator-based coupling control method on synchronizing two motions of two-degrees-of-freedom robot's joints is numerically simulated. Furthermore, the experimental setup of a two-degrees-of-freedom robot is established based on the real-time simulations system via the proposed central pattern generator-based coupling control method. And experiments are carried out on the established setup. Simulations and experimental results show that the phase of the controlled two-degrees-of-freedom robot's joints is mutual locked to other, and their motion pattern can be adjusted through the coupling parameter in the central pattern generator-based coupling control method. In conclusion, the proposed central pattern generator-based coupling control method can control the two-degrees-of-freedom robot's joints to produce the coordinated motions and adjust the rhythmic pattern of the two-degrees-of-freedom robot.

Research and Design of Multi-Joint Bionic Robot

According to the various movement patterns of snakes and caterpillars, the body structure of Multi-Joint Bionic Robot is designed and analyzed, and the Multi-Joint Bionic Robot model was printed by ABS material 3D.The multi-Joint Bionic Robot is designed to achieve winding forward, multi-limb reversal movement, turning, curled up and other movements, through the voice signal detection, ultrasonic distance detection to mimic the ears and eyes of the creature. At the same time, for the problem of controlling joints, a control method combining distributed control and centralized control is proposed, and the parallel control method of multi-joint joints is studied. Experiments were carried out on the multi-joint robot body to analyze the force of the Multi-Joint Bionic Robot during the movement, and the smoothness and fluency of the robot movement were realized.

Adaptive block compensation trajectory tracking control based on LuGre friction model

Aiming at the problems of modeling error and uncertain external disturbance in the multi-joint robot control model, an adaptive block compensation trajectory tracking controller based on LuGre friction model is proposed. Firstly, the algorithm divides the interference term of LuGre friction model into three parts with different physical quantities. Secondly, an adaptive neural network compensator is designed to assess the three parts of the LuGre friction model. Thirdly, a robust sliding mode controller is developed to reduce the influence of these estimation errors of neural network compensator and other uncertain disturbances and ensure that the system converges in a finite time at the same time. Finally, numerical simulations under different input and disturbance signals for the planar multi-joint robot and the inverted pendulum are conducted to validate the effectiveness of the proposed controller, and the performance of the proposed controller is compared with conventional sliding mode controller to illustrate the usefulness and efficiency of the proposed controller.

Parameter estimation survey for multi-joint robot dynamic calibration case study

Accurate model parameters are the basis of robot dynamics. Many linear and nonlinear models have been proposed to calibrate the inertial parameters and friction parameters of multi-joint robots. However, methods of choosing a model and calculating its parameters still have few summaries. This paper reviews typical linear/nonlinear models and different calculation methods for robot dynamic calibration. Through simulations, the features of different methods are analyzed, including torque error, parameter error, model adaptability, solution time, and anti-interference ability of the calibration results. Finally, an experiment performed on a six-degree-of-freedom industrial manipulator is used as an example to illustrate how to select the model for a specified robot. These comparisons and experiments provide references for the parameter calibration of multi-joint robots.

Optimized Design of Improved Permanent Magnet Synchronous Motor for Articulated Robot Using the Penalty Function Method and Response Surface Methodology

In this paper, an improved motor is presented for a smart, vertical, multi-joint robot actuator. The motor design was optimized using methodologies such as the penalty function method (PFM) and response surface methodology. To improve its performance, different pole-slot combinations were applied considering its electrical and mechanical characteristics. Using 2D finite element analysis, results were compared from a previous model and a newly proposed model. The experimental results confirmed that the proposed model achieved improved performance at the rated point.

Research and development of multi-joint Wall Mobile Robot using differential module

Research and development of multi-joint Wall Mobile Robot using differential module

Trajectory Planning Strategy for Robotic Water Polo Matches

An area partition-based ball-pushing control strategy is proposed for the real robot water polo events since the multi-joint robot fishes often play the edge ball or are unable to touch the ball in their attempt of pushing the ball. As a first step, the venue image acquired is partitioned into several areas for separate implementation of different control options regarding the position judgment of ball and fishes and the ball-pushing strategy. According to the line connecting the ball to the goal midpoint, the area around the ball is divided into the ball-pushing area and the non-ball-pushing area, and a temporary point is designed for the ball-pushing area. The robot fishes are set to hit the ball when they are in the ball-pushing area; and when they are in the non-ball-pushing area, the fishes are driven into the ball-pushing area via the temporary point to hit the ball. The experimental results show that the use of this method allows the robot fishes in the water to push the target ball to the goal more quickly and accurately. Aside from the 2V2 water polo competition, the proposed method is also applicable to the N V N water polo competition, and even robot path planning.

Design of Mechanical Structure of Punch Feeding Manipulator

In this paper an automatic feed manipulator for automobile stamping is introduced. It can achieve the process cycle for various cars parts manufactured such as automatic grab, loading and blanking, which is suitable for the large quantities and small mechanical parts material process. The primary purpose of this article is to present the manipulator structure and to design the virtual prototype of the manipulator. The calculation and optimization of stress and strain are carried out for the robot key moving parts by the analysis of the movement process and sport principle. Compared with the multi-joint robot, its manufacture, control requirements and the cost are low. The robot is suitable for large quantities and small parts process.

A multi-jointed underactuated robot hand with fluid-driven stretchable tubes

Inspired from flexible bending of octopus’ tentacles and outside-driving kind of traditional exoskeletons, this paper proposed a novel self-adaptive underactuated finger mechanism, called OS finger. OS finger is similar to an octopus’ tentacle and consists of an artificial muscle which is through all joints and driven by fluid, eight serial-hinged joints, and force-changeable assembly. The force-changeable assembly is mainly composed of a spring and elastic rubber membrane, which is coordinated for stable grasping by a layer of rubber material in the surface of the finger. OS finger can execute different grasping modes depending on the shapes and dimensions of the grasped objects and grip objects in a gentle and form-fitting manner. The OS finger combines good qualities of both rigid grasp of traditional fingers and form-fitting grasp of flexible fingers. Kinematic analysis and experimental results show that the OS robot Hand with four OS fingers is valid for precise pinching, self-adaptive powerful encompassing, and grasping forces that are freely changeable in a wide range. With the advantage of high self-adaptation, various grasp configurations and large range of grasping forces, the OS Hand has a wide range of applications in the area of service robotics which requires a lot of flexible operations of general grasping, moving and releasing.

Development of a Multi-Joint Robotic Ultrasonic Inspection System to Secure the Integrity of Composite Structures

Composite materials are lighter and better than existing metal materials in terms of corrosion and fatigue resistance, and have thus become popular as materials for structures that require lightening, such as automobiles and aircrafts. However, as these composite materials involve mechanical and physical degradation owing to delamination and voids, the reliability of the structures has become a concern. The ultrasonic inspection method is the most popular nondestructive method for detecting defects occurring in these structures, but this method has limitations in detecting defects owing to high anisotropy and sound attenuation. Moreover, the existing ultrasonic inspection method requires significant time and costs if used for large materials and structures. Therefore, we have developed a water squirter using a multi-joint robot and an automatic ultrasonic inspection system that adopts the through transmission ultrasonic inspection method to resolve these issues. The study observed that this system could effectively detect defects occurring in the composite material.

Elastic Structure Preserving (ESP) Control for Compliantly Actuated Robots

Physical compliance can be considered one of the key technical properties a robot should exhibit to increase its mechanical robustness. In addition, the accompanying temporal energy-storing capabilities enable explosive and energy efficient cyclic motions. But these advantages come at a price, as compliance introduces unwanted intrinsic oscillatory dynamics, underactuation, and reduces the natural frequency of the plant. These aspects make control of the link configuration variables a challenging task. This paper presents two novel control methods for implementing link-side motion tracking capabilities and injecting a desired damping characteristic to suppress link vibrations along the reference trajectory for compliantly actuated robots with nonlinear elastic characteristics. We prove their uniform global asymptotic stability by invoking a theorem by Matrosov. Both approaches, namely elastic structure preserving (ESP) and ESP+, have in common that they preserve the link-side inertial properties and the elastic structure of the original plant dynamics, hence the name ESP control. Apart from that, ESP control focuses on preserving the inertial properties of motor dynamics. While ESP+ control aims at minimizing the dynamic shaping on the motor side. The performance of the feedback control laws have been evaluated on the Hand Arm System from the German Aerospace Center (DLR), a variable stiffness robot arm, where the stiffness in each of its joints is highly nonlinear. To the best of our knowledge, this is the first experimentally validated tracking controller for compliantly actuated, multijoint robots with nonlinear elastic elements.

The Design of Control System for Multi Joint Robot based on PC+DSP

A multi joint robot control system was designed based on the universal processor PC+DSP in order to overcome the shortcomings of the control system in terms of flexibility, cost performance, and software transplantation, which use Industrial Personal Computer for the upper monitor and MAC Motion control card for the lower computer. The design of multi joint robot control system is accomplished through hardware circuit design, VC++ programming and so on. Finally, six joint robot platform is used to test the control performance, The results show that the designed control system has the advantages of flexible function, easy expansion and easy porting of software.

Automatic transformation tools of UML design models from virtual prototypes of multi-jointed robots

Most of robotic companies develop a control programming of multi-jointed robots, which spend too much time to manually adjust the moving functions of the robots. To solve this problem, we adapt the virtual prototyping (VP) to develop the control program of the robotic behaviors. For software engineers, in order for them to easily program this robot, we also apply metamodel mechanism to convert UML models with virtual prototyping model. We propose the automatic model transformation from the virtual prototyping model to UML models, which will then develop coding based on UML models. To prove our mechanism’s efficiency, we implement Robot to UML Translator (RUT) as our transformation rules with ATLAS transformational language. Lastly, we show experimental validation about the consistency of our proposed technique with an example of multi-joined robot prototype models.

Multi-Joint Robot Transfer System in Three Dimensional Space

Multi-Joint Robot Transfer System in Three Dimensional Space

Learning from demonstration: Teaching a myoelectric prosthesis with an intact limb via reinforcement learning.

Prosthetic arms should restore and extend the capabilities of someone with an amputation. They should move naturally and be able to perform elegant, coordinated movements that approximate those of a biological arm. Despite these objectives, the control of modern-day prostheses is often nonintuitive and taxing. Existing devices and control approaches do not yet give users the ability to effect highly synergistic movements during their daily-life control of a prosthetic device. As a step towards improving the control of prosthetic arms and hands, we introduce an intuitive approach to training a prosthetic control system that helps a user achieve hard-to-engineer control behaviours. Specifically, we present an actor-critic reinforcement learning method that for the first time promises to allow someone with an amputation to use their non-amputated arm to teach their prosthetic arm how to move through a wide range of coordinated motions and grasp patterns. We evaluate our method during the myoelectric control of a multi-joint robot arm by non-amputee users, and demonstrate that by using our approach a user can train their arm to perform simultaneous gestures and movements in all three degrees of freedom in the robot's hand and wrist based only on information sampled from the robot and the user's above-elbow myoelectric signals. Our results indicate that this learning-from-demonstration paradigm may be well suited to use by both patients and clinicians with minimal technical knowledge, as it allows a user to personalize the control of his or her prosthesis without having to know the underlying mechanics of the prosthetic limb. These preliminary results also suggest that our approach may extend in a straightforward way to next-generation prostheses with precise finger and wrist control, such that these devices may someday allow users to perform fluid and intuitive movements like playing the piano, catching a ball, and comfortably shaking hands.