Open Control System Research Articles

Coordinate-based control for a materials handling equipment utilizing real-time simulation

This paper presents the development and implementation of an advanced control system for a hydraulic manipulator. Designing a suitable coordinate control system for materials handling machines is vital for desired machine performance. For this purpose, targets of developing a proper coordinate control system were defined and mathematical equations were formulated. The two common control methods, i.e. open-loop control and closed-loop control were specifically designed for the handler in question, and the performance of the machine was studied applying each control method. The simulation environment and the operation principle of the created models are discussed in detail in this paper. The two control strategies introduced were tested through real-time simulation, and the accuracy and the performance of the manipulator were investigated utilizing each control method. The limitations and problems of each control strategy are addressed, and suggestions for further research directions to improve the accuracy of tip control are recommended. The case study in this paper is a mobile harbor crane material handler provided by the Mantsinen Group.

Adaptive sliding mode control of manipulators based on fuzzy random vector function links for friction compensation

To solve the instability problem caused by external uncertain friction, interference, and load changes in the sliding mode control system of an n-link manipulator, this paper proposes a novel adaptive fuzzy random vector function link (FRVFL)-inherited sliding mode control scheme for tracking the position of robot manipulators. The random vector function link (RVFL) network is fuzzified to improve its generalization ability. On fuzzification, the RVFL network can achieve self-mapping between fuzzy rules and hidden layers, thereby reducing the complexity of the algorithm. The proposed algorithm uses adaptive rules to achieve self-adjustment for output weights. Thus, precise approximation of the unknown nonlinear dynamics in the control system can be realized. A robust control term is added to the controller to further weaken the sliding mode chattering and improve the tracking effect of a two-link manipulator. The closed-loop stability of the proposed algorithm is analyzed using the Lyapunov theorem. Simulation results on the control of the two-link manipulator prove the effectiveness of the proposed algorithm.

Design of auto disturbance rejection control system for pneumatic manipulator based on PLC Technology

Aiming at the coupling effect between joints of two degree of freedom pneumatic mechanism in reciprocating motion, and the reciprocating motion problem caused by the imprecision and jitter of dynamic model in high-speed motion, an auto disturbance rejection control system of Pneumatic Manipulator Based on PLC technology is designed, and the parameter model of flexible joint manipulator system is established, and the cubic spline interpolation is optimized by PLC technology, The effective control mode of operation space is realized. The correctness and stability of the active disturbance rejection control system of Pneumatic Manipulator Based on PLC technology are verified by simulation experiment.

Design of A Three-DOF Redundantly Driven Parallel Robot Control System

Parallel robot has advantages of no friction and clearance, fast response, compact structure, good rigidity, and low error accumulation, but they also have many shortcomings in geometric characteristics, such as small range of motion, poor flexibility, and singularity in the workspace. Adding redundancy can improve its geometric characteristics. Parallel robots are usually controlled by dedicated controllers, without openness, high development costs, and long cycles. This paper introduces the design of an open control system for a three-DOF redundant drive robot based on PC bus, and with "PC + motion control card" as the core.

Intelligent robust control of redun-dant smart robotic arm Pt II: Quantum computing KB optimizer

In the first part of the article, two ways of fuzzy controller’s implementation showed. First way applied one controller for all links of the manipulator and showed the best performance. However, such an implementation is not possible in complex control objects, such as a planar redundant manipulator with seven degrees of freedom (DoF). The second way use of separated control when an independent fuzzy controller controls each link. The decomposition control due to a slight decrease in the quality of management has greatly simplified the processes of creating and placing knowledge bases. In this paper (Part II), the advantages and limitations of intelligent control systems based on soft computing technology described. To eliminate the mismatch of the work of separate independent fuzzy controllers, methods for self-organizing coordination control based on quantum computing technologies to create and design robust intelligent control systems for robotic manipulators with 3DOF and 7DOF described. Quantum fuzzy inference as quantum self-organization algorithm of imperfect KBs introduced. Quantum computational intelligence smart toolkit QCOptKBTMbased on quantum fuzzy inference applied. QCOptKBTM toolkit include quantum deep machine learning in on line. Successful engineering application of end-to-end quantum computing information technologies (as quantum sophisticated algorithms and quantum programming) in searching of solutions of algorithmic unsolved problems in classical dynamic intelligent control systems, artificial intelligence (AI) and intelligent cognitive robotics discussed. Quantum computing supremacy in efficient solution of intractable classical tasks as global robustness of redundant robotic manipulator in unpredicted control situations demonstrated. As result, the new synergetic self-organization information effect of robust KB design from responses of imperfect KBs (partial KB robustness cretead on toolkit SCOptKBTM in Pat I) fined.

Robotic grasping with obstacle avoidance using octrees

This paper considers the problems of the integration of independent manipulator control systems. Areas of control of the manipulator are: recognition of objects and obstacles, identification of objects to be grasped, determination of reliable positions by the grasping device, planning of movement of the manipulator to certain positions with avoidance of obstacles, and recognition of slipping or determination of reliable grasping. This issue is a current problem primarily in industry, general-purpose robots, and experimental robots. This paper considers current publications that address these issues. Existing algorithms and approaches have been found in the management of both parts of the robot manipulator and solutions that combine several areas, or the integration of several existing approaches. There is a brief review of current literature and publications on the above algorithms and approaches. The advantages and disadvantages of the considered methods and approaches are determined. There are solutions that cover either some areas or only one of them, which does not meet the requirements of the problem. Using existing approaches, integration points of existing implementations are identified to get the best results. In the process, a system was developed that analyzes the environment, finds obstacles, objects for interaction, poses for grasping, plans the movement of the manipulator to a specific position, and ensures reliable grasping of the object. The next step was to test the system, test the performance, and adjust the parameters for the best results. The resulting system was developed by the research team of RT-Lions, Technik University, Reutlingen. The hardware research robot includes an Intel Realsense camera, a Sawyer Arm manipulator from Rethink Robotics, and an internally grabbing device.

Fly-by-Pi: Open source closed-loop control for geotechnical centrifuge testing applications

Geotechnical centrifuges are valuable instruments for physical modelling of complex geotechnical problems in a controlled laboratory setting. In comparison to full-scale testing, scaled models are cost effective to construct and instrument and, when tested in a geotechnical centrifuge at increased centrifugal accelerations, are capable of replicating full-scale stress–strain soil behaviour. Centrifuge modellers require specialised hardware and instruments capable of functioning under high accelerations. Such hardware is costly, nearly always purpose built, and often rely on commercial, closed-source data acquisition systems, hardware and control systems.This paper demonstrates a novel and versatile, low cost, open source logger and control system that works in parallel alongside existing centrifuge hardware. This solution, termed Fly-by-Pi, was developed using the Raspberry Pi microcomputer. The system provides closed-loop control of linear actuators with the ability to operate in either cyclic, monotonic, or static load- or displacement-control. The control mechanism can be reprogrammed according to experimental requirements, even during flight in the centrifuge. Three independent experiments are described which included the Fly-by-Pi controller as a key component in their operation. Based on the experience gained during these experiments, the authors encourage wide-spread adoption of open-sourced hardware solutions in extreme testing environments.

Genetic Algorithm Approach for Gains Selection of Induction Machine Extended Speed Observer

The subject of this paper is gains selection of an extended induction machine speed observer. A high number of gains makes manual gains selection difficult and due to nonlinear equations of the observer, well-known methods of gains selection for linear systems cannot be applied. A method based on genetic algorithms has been proposed instead. Such an approach requires multiple fitness function calls; therefore, using a quality index based on simulations makes gains selection a time-consuming process. To find a fitness function that evaluates, in a short time, quality indices based on poles placement have been proposed. As the observer is nonlinear, equations describing the observer dynamics have been linearized. The relationship between poles placement and real dynamic properties has been shown. A series of studies has been performed to investigate the influence of the operating point of the machine on the dynamics of the observer. It has been proven that rotor speed has a significant impact on the placement of the poles and the observer may lose stability after a rotation direction change. A method of gains modification to maintain symmetrical properties of the observer for both directions has been presented. Experimental studies of the observer during machine reverse in the open and closed-loop control system have been performed. The results show that the observer can be implemented in a sensorless drive, using the proposed gains selection method.

Development of 3D scanning system for robotic plasma processing of medical products with complex geometries

This paper describes the development of an intelligent automated control system of a robot manipulator for plasma treatment of medical implants with complex shapes. The two-layer coatings from the Ti wire and hydroxyapatite powders are applied on the surface of Ti medical implants by microplasma spraying to increase the biocompatibility of implants. The coating process requires precise control of a number of parameters, particularly the plasma spray distance and plasma jet traverse velocity. Thus, the development of the robotic plasma surface treatment involves automated path planning. The key idea of the proposed intelligent automatic control system is the use of data of preliminary three-dimensional (3D) scanning of the processed implant by the robot manipulator. The segmentation algorithm of the point cloud from laser scanning of the surface is developed. This methodology is suitable for robotic 3D scanning systems with both non-contact laser distance sensors and video cameras, used in additive manufacturing and medicine.

High-speed algorithms for automatic manipulators control systems

This article presents options for implementing high-speed algorithms for controlling automatic manipulators operating as part of robotic complexes (RTCs). Software control systems for automatic manipulators with the use of noise-resistant coding algorithms are considered in the conditions of operation in production conditions, when there is instability in the supply of energy resources, the presence of sources of network interference, interference that violates the safe working conditions of radio-electronic equipment. Examples of implemented control algorithms with different software cycles are given, regarding into account the peculiarities of production. A comparative analysis is made with analogs that have similar technological characteristics.

Modular approach application in development of computer numerical control software

Subject of Research. The paper proposes an approach to the development of a numerical control kernel. The approach implies creating software from separate modules interacting via a unified programming interface with a high level of granularity. Thus, a system with a required configuration can be developed in a relatively short time. The study also considers the possibility of using open source computer numerical control systems as a basis, which will further reduce the design time. The approach for computer numerical control development is considered in the context of its application on multipurpose modular equipment. Method. The proposed solution is based on a multi-protocol control system and combines software and hardware components from different manufacturers. Platform independence is also provided. This method allows a prompt development of the numerical control system for any type of processing or other operations according to the requirements of hardware, and also gives wide opportunities for further modifications that increase the equipment efficiency. Main Results. The practical result obtained is a software trajectory-planning library, including geometry analysis, feed rate control and interpolation. Commands for controlling outputs and status of inputs are integrated into the cyclic data of the drive control and transmitted via the same interface. All developed modules are independently designed and can be embedded into other open source systems, as well as be further modified for processing efficiency increase. Practical Relevance. The work is aimed at increasing the economic independence of small design organizations and enterprises. The proposed modular approach allows the development of a required numerical control system for multipurpose modular equipment in a short time, and will significantly expand the capabilities of rapid prototyping and ensure the prompt production of pilot batches.

Design and Implementation of CNC System for WEDM Machine Tool Based on Active Object

A software framework design method for embedded real-time control system is proposed for the conversion of internal behavior state of CNC machine tool control system. This method uses the active object calculation model to plan and model the internal state of the linear cutting CNC system. On this basis, an open machine tool control system is built, and the design of the linear cutting machine bed control system is realized. The system design realizes the middle layer of the system based on a lightweight framework, and truly realizes the separation of the hardware and software of the control system. Each object is independent of each other and does not share resources. Information events are distributed through the “Publication-Subscription” method, and the line is designed to be cut. It can solve the problem of poor reconstruction ability of the original system and improve the portability of the system.

A Control System of SEMG Signal Based on Deep Learning

The research of control system based on sEMG signal is a popular field at present. It collects bioelectricity of human body through surface electrode. It has the new characteristic of subject fusion, and it is the combination of engineering technology and medical theory, specifically the application of cross combination of control science and electrophysiology. In this paper, the human surface EMG signal is taken as the research object, and a manipulator control system based on one-dimensional convolutional neural network (CNN) is proposed, and the functions and implementation methods of each part of the system are analyzed. The experimental results show that the recognition accuracy of the training model is 0.973, and the design scheme of EMG signal recognition and classification system with deep learning method is feasible. The successful design of the system provides technical support and theoretical basis for the further study of electrophysiological signals.

Improved neural network-based adaptive tracking control for manipulators with uncertain dynamics

In this article, a robust adaptive tracking controller is developed for robot manipulators with uncertain dynamics using radial basis function neural network. The design of tracking control systems for robot manipulators is a highly challenging task due to external disturbance and the uncertainties in their dynamics. The improved radial basis function neural network is chosen to approximate the uncertain dynamics of robot manipulators and learn the upper bound of the uncertainty. The adaptive law based on the Lyapunov stability theory is used to solve the uniform final bounded problem of the radial basis function neural network weights, which guarantees the stability and the consistent bounded tracking error of the closed-loop system. Finally, the simulation results are provided to demonstrate the practicability and effectiveness of the proposed method.

Control system of the six-axis serial manipulator based on active disturbance rejection control

This study considers the problems of manipulators with high coupling, parameter uncertainties, and external disturbances. A six-axis serial manipulator control system based on active disturbance rejection control strategy is proposed without the requirement of the exact dynamic model. First, the operating circuit of the manipulator joint motor is analyzed, and the mathematical model of the direct-current torque motor is established. Second, the components of active disturbance rejection control are designed, and a new nonlinear function is selected to construct the extended state observer and nonlinear state error feedback control law. Then, Kalman filter is introduced into an extended state observer to estimate the disturbance efficiently. Finally, the proportion–integration–differentiation control, traditional active disturbance rejection control, and improved active disturbance rejection control are simulated and compared under the same input signal. The results show that the proposed control strategy has good dynamic performance and uncertain disturbance robustness, which proves the effectiveness of the proposed method.

A Low-Cost, Disposable and Portable Inkjet-Printed Biochip for the Developing World.

Electrowetting on dielectric-based digital microfluidic platforms (EWOD-DMF) have a potential to impact point-of-care diagnostics. Conventionally, EWOD-DMF platforms are manufactured in cleanrooms by expert technicians using costly and time consuming micro-nanofabrication processes such as optical lithography, depositions and etching. However, such high-end microfabrication facilities are extremely challenging to establish in resource-poor and low-income countries, due to their high capital investment and operating costs. This makes the fabrication of EWOD-DMF platforms extremely challenging in low-income countries, where such platforms are most needed for many applications such as point-of-care testing applications. To address this challenge, we present a low-cost and simple fabrication procedure for EWOD-DMF electrode arrays, which can be performed anywhere with a commercial office inkjet printer without the need of expensive cleanroom facilities. We demonstrate the utility of our platform to move and mix droplets of different reagents and physiologically conductive buffers, thereby showing its capability to potentially perform a variety of biochemical assays. By combining our low-cost, inkjet-printed EWOD-DMF platform with smartphone imaging technology and a compact control system for droplet manipulation, we also demonstrate a portable and hand-held device which can be programmed to potentially perform a variety of biochemical assays.

Understanding factors affecting technical debt

Technical debt is the debt in the software development incurred due to preference of short term deadlines over the strategic ones. Analysis of the factors effecting technical debt (TD) is need of the hour from business as well as technical context. Based on the state of the art described in the literature, we have tried to identify the most contributing factors effecting TD. For doing so various statistical tools and models are used. The paper studies different factors effecting technical debt specifically commit frequency, LOC, coverage, code smells and reputation of the contributor. To unveil affect of these variables, SonarQube tool is used to find the technical debt and related metrics. The dataset taken for the purpose is open source version control system from Github. It is proved through the study that as we increase the commit frequency, lines of code, coverage and code smells there is corresponding considerable change in the technical debt as well. While, the reputation factors viz., stars, followers and repositories do not affect technical debt so considerably. The regression model of reputation and TD is also developed.

Tutorial Review of Bio-Inspired Approaches to Robotic Manipulation for Space Debris Salvage.

We present a comprehensive tutorial review that explores the application of bio-inspired approaches to robot control systems for grappling and manipulating a wide range of space debris targets. Current robot manipulator control systems exploit limited techniques which can be supplemented by additional bio-inspired methods to provide a robust suite of robot manipulation technologies. In doing so, we review bio-inspired control methods because this will be the key to enabling such capabilities. In particular, force feedback control may be supplemented with predictive forward models and software emulation of viscoelastic preflexive joint behaviour. This models human manipulation capabilities as implemented by the cerebellum and muscles/joints respectively. In effect, we are proposing a three-level control strategy based on biomimetic forward models for predictive estimation, traditional feedback control and biomimetic muscle-like preflexes. We place emphasis on bio-inspired forward modelling suggesting that all roads lead to this solution for robust and adaptive manipulator control. This promises robust and adaptive manipulation for complex tasks in salvaging space debris.

Proposal of Takagi-Sugeno Fuzzy-PI Controller Hardware.

This work proposes dedicated hardware for an intelligent control system on Field Programmable Gate Array (FPGA). The intelligent system is represented as Takagi–Sugeno Fuzzy-PI controller. The implementation uses a fully parallel strategy associated with a hybrid bit format scheme (fixed-point and floating-point). Two hardware designs are proposed; the first one uses a single clock cycle processing architecture, and the other uses a pipeline scheme. The bit accuracy was tested by simulation with a nonlinear control system of a robotic manipulator. The area, throughput, and dynamic power consumption of the implemented hardware are used to validate and compare the results of this proposal. The results achieved allow the use of the proposed hardware in applications with high-throughput, low-power and ultra-low-latency requirements such as teleoperation of robot manipulators, tactile internet, or industry 4.0 automation, among others.

ANALYSIS OF THE SPEED OF THE DEFUZZIFIER IN THE TASK OF CONTROLLING THE ROBOT-MANIPULATOR

Linear, nonlinear, modified, high-speed defuzzifiers based on the area ratio method are presented in this paper. The proposed defuzzifiers are used in a fuzzy digital filter device and make it possible to ensure the additivity of the robotic manipulator control system, since traditional models do not have this property. The essence of this development is to find a crisp value of the output fuzzy variable, which in this case are the regulation coefficients of the fuzzy digital filter. Reducing the number of computational operations provides an increase in the performance of the defuzzifier. The reduction in number of computational operations is carried out by eliminating the output variable’s truncated term’s height calculation, thereby reducing the computation time. A simulation model which was implemented in the MatLab Simulink system, for a neuro-fuzzy device of the robotic arm using linear and non-linear defuzzifiers is presented. The dependence of time graphs on the angle of rotation of the joints of the robotic manipulator are compared, based on the traditional center of gravity method and the method shown in this paper. It was found that the traditional center of gravity method does not ensure the fulfillment of the specified rotation angles of the links of the robotic arm, while the proposed models of defuzzifiers have this property, which can be seen from the presented dependency graphs. The simulation model of the device was also designed as a parallel-conveyor device for implementation in the field-programmable gate array of the Xilinx Spartan 3Е family. The analysis showed that the calculation time for a crisp value with high-speed defuzzification is 130 ns, which is two orders of magnitude higher than existing models. The experiment was conducted at a frequency of 100 MHz.