Real-time Control Architecture Research Articles

Research on the key techniques of composite processing of EDM and vibration ultrasonic drilling

PurposeUtilizing electrical discharge machining (EDM) to process micro-holes in superalloys may lead to the formation of remelting layers and micro-cracks on the machined surface. This work proposes a method of composite processing of EDM and ultrasonic vibration drilling for machining precision micro-holes in complex positions of superalloys.Design/methodology/approachA six-axis computer numerical control (CNC) machine tool was developed, whose software control system adopted a real-time control architecture that integrates electrical discharge and ultrasonic vibration drilling. Among them, the CNC system software was developed based on Windows + RTX architecture, which could process the real-time processing state received by the hardware terminal and adjust the processing state. Based on the SoC (System on Chip) technology, an architecture for a pulse generator was developed. The circuit of the pulse generator was designed and implemented. Additionally, a composite mechanical system was engineered for both drilling and EDM. Two sets of control boards were designed for the hardware terminal. One set was the EDM discharge control board, which detected the discharge state and provided the pulse waveform for turning on the transistor. The other was a relay control card based on STM32, which could meet the switch between EDM and ultrasonic vibration, and used the Modbus protocol to communicate with the machining control software. FindingsThe mechanical structure of the designed composite machine tool can effectively avoid interference between the EDM spindle and the drilling spindle. The removal rate of the remelting layer on 1.5 mm single crystal superalloys after composite processing can reach over 90%. The average processing time per millimeter was 55 s, and the measured inner surface roughness of the hole was less than 1.6 µm, which realized the micro-hole machining without remelting layer, heat affected zone and micro-cracks in the single crystal superalloy.Originality/valueThe test results proved that the key techniques developed in this paper were suite for micro-hole machining of special materials.

Distributed real-time control architecture for electrohydraulic humanoid robots

PurposeThis paper aims to develop an adaptable control architecture for electrohydraulic humanoid robots (HYDROïD) that emulate the functionality of the human nervous system. The developed control architecture overcomes the limitations of classical centralized and decentralized systems by distributing intelligence across controllers.Design/methodology/approachThe proposed solution is a distributed real-time control architecture with robot operating system (ROS). The joint controllers have the intelligence to make decisions, dominate their actuators and publish their state. The real-time capabilities are ensured in the master controller by using a Preempt-RT kernel beside open robot control software middleware to operate the real-time tasks and in the customized joint controllers by free real-time operating systems firmware. Systems can be either centralized, where all components are connected to a central unit or decentralized, where distributed units act as interfaces between the I/Os and the master controller when the master controller is without the ability to make decisions.FindingsThe proposed architecture establishes a versatile and adaptive control framework. It features a centralized hardware topology with a master PC and distributed joint controllers, while the software architecture adapts based on the task. It operates in a distributed manner for precise, force-independent motions and in a decentralized manner for tasks requiring compliance and force control. This design enables the examination of the sensorimotor loop at both low-level joint controllers and the high-level master controller.Originality/valueIt developed a control architecture emulating the functionality of the human nervous system. The experimental validations were performed on the HYDROïD. The results demonstrated 50% advancements in the update rate compared to other humanoids and 30% in the latency of the master processor and the control tasks.

A Function Approximator Model for Robust Online Foot Angle Trajectory Prediction Using a Single IMU Sensor: Implication for Controlling Active Prosthetic Feet

Lower limb dysfunction hinders the locomotive activity in individuals and compels them to use assistive devices such as prostheses or orthoses to restore the missing locomotive functions. Passive assistive devices have limitations in replacing the lost functionality. On the other hand, active devices could restore more natural locomotion using motorized joints. To make proper use of these embedded motors, a control architecture is required to translate the motion intent of the user into the intended prosthesis joint trajectories. In this article, we propose a temporal convolution-based online foot angle trajectory prediction network (FATP-N) that predicts the foot angular positions during unconstrained walking from the shank angular position measured using a single wearable motion tracker sensor. The data acquisition experiments were designed to reflect natural gait with turns, varying inclines, speeds, and mixed cadences. The trained models were prepared for real-time prediction by compressing them to reduce the storage and time complexity. The validations were performed on different motion conditions, including those that have not been used for model training, to verify the robustness of the model. The proposed FATP-N achieved high accuracy and could generate predictions in real time. The results indicate that the proposed approach offers a possible architecture for real-time control of powered intelligent prostheses.

Develop Real-Time Robot Control Architecture Using Robot Operating System and EtherCAT

This paper presents the potential of combining ROS (Robot Operating System), its state-of-art software, and EtherCAT technologies to design real-time robot control architecture for human–robot collaboration. For this, the advantages of an ROS framework here are it is easy to integrate sensors for recognizing human commands and the well-developed communication protocols for data transfer between nodes. We propose a shared memory mechanism to improve the communication between non-real-time ROS nodes and real-time robot control tasks in motion kernel, which is implemented in the ARM development board with a real-time operating system. The jerk-limited trajectory generation approach is implemented in the motion kernel to obtain a fine interpolation of ROS MoveIt planned robot path to motor. EtherCAT technologies with precise multi-axis synchronization performance are used to exchange real-time I/O data between motion kernel and servo drive system. The experimental results show the proposed architecture using ROS and EtherCAT in hard real-time environment is feasible for robot control application. With the proposed architecture, a user can efficiently send commands to a robot to complete tasks or read information from the robot to make decisions, which is helpful to reach the purpose of human–robot collaboration in the future.

Commonsense visual sensemaking for autonomous driving – On generalised neurosymbolic online abduction integrating vision and semantics

We demonstrate the need and potential of systematically integrated vision and semantics solutions for visual sensemaking in the backdrop of autonomous driving. A general neurosymbolic method for online visual sensemaking using answer set programming (ASP) is systematically formalised and fully implemented. The method integrates state of the art in visual computing, and is developed as a modular framework that is generally usable within hybrid architectures for realtime perception and control. We evaluate and demonstrate with community established benchmarks KITTIMOD, MOT-2017, and MOT-2020. As use-case, we focus on the significance of human-centred visual sensemaking —e.g., involving semantic representation and explainability, question-answering, commonsense interpolation— in safety-critical autonomous driving situations.The developed neurosymbolic framework is domain-independent, with the case of autonomous driving designed to serve as an exemplar for online visual sensemaking in diverse cognitive interaction settings in the backdrop of select human-centred AI technology design considerations.

An integrated software architecture for the pollution-based real-time control of urban drainage systems

Abstract This paper presents a complete methodology for the development of an integrated software architecture, which can achieve a closed-loop application between the integrated real-time control (RTC) and a virtual reality simulation for the urban drainage system (UDS). Quality measurements are considered during the simulation and optimization process. Model predictive control (MPC) and rule-based control (RBC) are the two main RTC methods embedded in this architecture. The proposed integration environment allows the different software components to efficiently and effectively communicate and work in a system-wide way, as well as to execute all the necessary steps regarding input parameter management, scenario configuration and results extraction. The proposed approaches are implemented into a pilot based on the Badalona UDS (Spain). Results from different scenarios with individual control approaches and rain episodes are evaluated and discussed.

Experimental validation of integrated and robust control system for mobile robots

The need to design a robust, accurate and lightweight real-time control architecture for a low-cost embedded system has become a necessary step in robotics applications. Therefore, the goal of this work is to design an integrated and accurate control system for a differential wheeled mobile robot. A hierarchical control approach has been adopted in this work which, takes into account the sub-systems controller of the problem related to robot path tracking. To this end, the control structure includes the design of a sliding mode control (SMC) scheme to stabilize the robot and precisely track the path that matches the kinematics of the mechanical structure. Moreover, the control structure provides a new design of the DC motor controller for optimum performance. To obtain an integrated control system for automated tasks, an accurate position estimation and an optimized high-level path planning algorithm have been proposed. The robustness and performance of the approved control and estimation systems have been verified through real-time implementations in different experiments. The results show the high accuracy of the robot’s tracking on different paths.

COTS-Based Real-Time System Development: An Effective Application in Pump Motor Control

The progress of embedded control systems in the last several years has made possible the realization of highly-effective controllers in many domains. It is essential for such systems to provide effective performance at an affordable cost. Furthermore, real-time embedded control systems must have low energy consumption, as well as be reliable and timely. This research investigates primarily the feasibility of implementing an embedded real-time control system, based on a low-cost, commercially off-the-shelf (COTS) microcontroller platform. It explores real-time issues, such as the reliability and timely response, of such a system implementation. This work presents the development and performance evaluation of a novel real-time control architecture, based upon a BeagleBoard microcontroller, and applied into the PWM (pulse width modulation) control of a three-phase induction motor in a suction pump. The approach followed makes minimal use of general-purpose hardware (BeagleBone Black microcontroller board) and open-source software components (including Linux Operating System with PREEMPT_RT real-time support) for building a reliable real-time control system. The applicability of the proposed control system architecture is validated and evaluated in a real case study in manufacturing. The results provide sufficient evidence of the efficiency and reliability of the proposed approach into the development of a real-time control system based upon COTS components.

A many-core CPU prototype of an MCAO and LTAO RTC for ELT-scale instruments

We propose a many-core CPU architecture for Extremely Large Telescope (ELT) scale adaptive optics (AO) real-time control (RTC) for the multi-conjugate AO (MCAO) and laser-tomographic AO (LTAO) modes. MCAO and LTAO differ from the more conventional single-conjugate (SCAO) mode by requiring more wavefront sensor (WFS) measurements and more deformable mirrors to achieve a wider field of correction, further increasing the computational requirements of ELT-scale AO. We demonstrate results of our CPU based AO RTC operating firstly in SCAO mode, using either Shack-Hartmann or Pyramid style WFS processing, and then in MCAO mode and in LTAO mode using the specifications of the proposed ELT instruments, MAORY and HARMONI. All results are gathered using a CPU based camera simulator utilising UDP packets to better demonstrate the pixel streaming and pipe-lining of the RTC software. We demonstrate the effects of switching parameters, streaming telemetry and implicit pseudo open-loop control (POLC) computation on the MCAO and LTAO modes. We achieve results of < 600$\mu$s latency with an ELT scale SCAO setup using Shack-Hartman processing and < 800$\mu$s latency with SCAO Pyramid WFS processing. We show that our MCAO and LTAO many core CPU architecture can achieve full system latencies of < 1000$\mu$s with jitters < 40$\mu$s RMS. We find that a CPU based AO RTC architecture has a good combination of performance, flexibility and maintainability for ELT-scale AO systems.

Distributed control architecture for real-time model predictive control for system-level harmonic mitigation in power systems

It can be challenging to design and implement Model Predictive Control (MPC) schemes in systems with fast dynamics. As MPCs often introduce high computational loads, it can be hard to assure real-time properties required by the dynamic system. An understanding of the system’s behavior, to exploit system properties that can benefit real-time implementation is imperative. Moreover, MPC implementations on embedded local devices rarely allows flexibility to changes in model and control philosophy, due to increased complexity and computational loads. A change in control philosophy (run-time) can be quite relevant in power systems that can change from an integrated to a segregated state. This paper proposes a distributed control hierarchy with a real-time MPC implementation, designed as a higher-level control unit, to feed a lower-level control device with references. The higher-level control unit’s objective in this paper is to generate the control reference of an Active Power Filter for system-level harmonic mitigation. In particular, a novel system architecture, which incorporates the higher-level MPC control and handles distribution of control action to low-level controllers, as well as receiving measurements used by the MPC, is proposed to obtain the application’s real-time properties and control flexibility. The higher-level MPC control, which is designed as a distributed control node, can be swapped with another controller (or control philosophy) if the control objective or the dynamic system changes. A standard optimization framework and standard software and hardware technology is used, and the MPC is designed on the basis of repetitive and distributed control, which allows the use of relatively low control update rate. A simulator architecture is implemented with the aim of mimicking a Hardware-In-Loop (HIL) simulator test to evaluate the application’s real-time properties, as well as the application’s resource usage. The results demonstrates that the implementation of the harmonic mitigation application exhibits the real-time requirements of the application with acceptable resource usage.

Real-time control architecture based on Xenomai using ROS packages for a service robot

This paper proposes a real-time (RT) control architecture based on Xenomai, an RT embedded Linux, to control a service robot along with non-real-time (NRT) robot operating system (ROS) packages. Most software, including device drivers and ROS, are developed to operate under the standard Linux kernel that does not provide RT guarantees. Standard Linux system calls in an RT context stimulates mode switching, resulting in non-deterministic responses and stability problems such as priority inversion and kernel panic. This paper overcomes such issues through a communication interface between RT and NRT tasks, termed cross-domain datagram protocol. The proposed architecture supports priority-based scheduling of multiple tasks while exposing an interface compatible with the original ROS packages. Moreover, it enables standard device driver operation inside RT tasks without developing RT device drivers that requires significant amount of development time. Feasibility is proven by implementation on a Raspberry Pi 3, a low-cost open embedded hardware platform, and conducted various experiments to analyze its performance and applied it to a service robot using ROS navigation packages. The results indicate that the proposed architecture can effectively provide an RT environment without stability issues when utilizing ROS packages and standard device drivers.

Nonlinear receding horizon control-based real-time guidance, navigation, and control architecture for launch vehicles

For almost as long as the Western world has had rockets and missiles, people have been interested in incorporating guidance systems into them [1], [2]. Robert Goddard experimented with rudimentary gyroscopic systems as early as the 1930s. Under the leadership of Wernher Von Braun and his team in the 1940s, V2 rockets used gyroscopes and an accelerometer, along with a simple analog computer, to help adjust their azimuth. Advancements continued to be made after World War II, including the development of guidance systems that adhered as closely as possible to a preplanned reference trajectory [1]-[3]. Expanding on this, studies (such as Launius and Jenkins [4]) provide a broader perspective into the history of the launch vehicle control problem. In his doctrine, Friedberg touches upon the history of U.S. launch vehicle missions [5], while Bilstein sheds light on the Apollo/Saturn launch vehicle program [6]. Such systems, and their offshoots, used differences in the actual velocity vector vs. the expected velocity vector, as well as vector cross products and partial derivatives, to determine what corrective guidance actions to take.

High Performance Motion-Planner Architecture for Hardware-In-the-Loop System Based on Position-Based-Admittance-Control

This article focuses on a Hardware-In-the-Loop application developed from the advanced energy field project LIFES50+. The aim is to replicate, inside a wind gallery test facility, the combined effect of aerodynamic and hydrodynamic loads on a floating wind turbine model for offshore energy production, using a force controlled robotic device, emulating floating substructure’s behaviour. In addition to well known real-time Hardware-In-the-Loop (HIL) issues, the particular application presented has stringent safety requirements of the HIL equipment and difficult to predict operating conditions, so that extra computational efforts have to be spent running specific safety algorithms and achieving desired performance. To meet project requirements, a high performance software architecture based on Position-Based-Admittance-Control (PBAC) is presented, combining low level motion interpolation techniques, efficient motion planning, based on buffer management and Time-base control, and advanced high level safety algorithms, implemented in a rapid real-time control architecture.

Real-time modeling, control and optimization of turbo-machinery auxiliary plants

In the Oil & Gas industry, the testing of auxiliary lubrication plants represents a mandatory preliminary activity before the whole turbo-machinery train (including the auxiliary lubrication plant) can be put in operation. To this end, the employment of both efficient and accurate plant models becomes very important to synthesize satisfactory control strategies for both testing and normal operation purposes. This way, many benefits (e.g. in terms of safety, times and costs of execution) can be achieved. Therefore, this article focuses on the development of innovative and efficient real-time models and control architectures to describe and regulate the auxiliary lubrication systems. All the new strategies have been validated through accurate real experimental campaign and real-time hardware. According to the Bond-Graph modeling strategy, an efficient lumped parameter model of the lube oil console has been built to properly optimize the description of such system and the efficiency of the control strategies...

Design of Sensor Data Flow for Ship Information System

In this paper, the design principles of sensor data flow in ship information system (SIS) structure are researched. In order to save communication resources to achieve the practicable maximum without sacrificing the expected performance of system, an observability analysis-based setting method is proposed to shorten the length of each sensor data flow. In addition, according to the determined data flow length, a scheduling algorithm is presented to set the content of data flow as well. This scheduling algorithm is based on a double-index evaluation method, which includes the variation of sensor data during assigned steps, meanwhile the deviation between estimated value and real value of observation is considered as well. Besides these, algorithm and hardware realization examples are provided at the end of this paper. 1. Introduction The past three decades have witnessed the rapid spreading of a ship information system (SIS) architecture in which sensors and actuators exchange information with a Command Control Interface (CCI) through a communication network. Based on such wide-scale networks, ship control/monitoring systems (such as Integrated Bridge System, Standard Machinery Control System) are able to be linked together. These technological advances make it possible to create a highly integrated real-time control architecture in a modern ship (Geer 2009). As a result, several SISs have been widely applied in different types of ships, e.g., RICE (Lister and Rosie 1995), Ship System 2000 (Källberg and Stråhle 2001), GEDMS (Meier and Manfredi 2006), FORCEnet (Waters et al. 2005), and Total Ship Computing Environment (Henry et al. 2009). For most designers, the SIS is more like a special application case of Supervisory Control and Data Acquisition (SCADA) system, the theory research of SIS is scattered and immethodical. However, there also exist several differences in normal SCADA system and SIS. For example, the connection principle between distributed controller units (DCUs) and remote terminal units in SIS is mere proximity instead of task relation, which has reduced the difficulty of planning and laying networks greatly, but increases the complexity of every control processes in SIS, most missions in SIS are designed to be completed by several DCUs cooperatively. Such structure has been summarized briefly by Liu et al. (2014a). Mostly, a SIS could be regarded as a wide-scale sensor/actuator network under a highly integrated structure in the ship environment, which increases the importance of sensor information obtaining ability. In recent years, the U.S. Naval Research Laboratory has developed a multisensory real-time detection system for situational awareness named "Volume Sensor" (Minor et al. 2007). This designed framework can serve as a template for a variety of real-time sensing and situational awareness applications.

Open-loop and closed-loop flow control based on Van der Pol modeling

A real-time modeling and control architecture for coupled shear layer von Karman instabilities on a wing section wake is developed. Previous wind tunnel experiments highlighted that these wake instabilities give rise to limit cycles on both local and resulting airloads. The two-state Van der Pol system is employed to model the self-sustained oscillations exhibited by the actual flow. Schemes featuring either one or two coupled Van der Pol oscillators in parallel are taken under consideration. Open-loop and closed-loop control laws to manipulate and reduce the self-sustained oscillations are extensively studied. An adaptive control scheme is developed to optimize the performance of the controller, according to the flow conditions. For the open-loop control scheme, the consistency with experimental tests performed on a wind tunnel model is shown.

Distributed Real-time Control Architecture for ROS-based Modular Robots

Nowadays ROS (Robot Operating System) based platforms have been widely used in state of art robot researches because of providing reliable mechanisms for fast robot development and algorithm reuse. Among them, modular robots are presented as a Distributed Control System (DCS), in which the data supply and the flow rates must be ensured to guarantee a proper execution. Although ROS network architecture provides a solution for distributed communication, it entails some disadvantages. Real-time constraints assurance and large networks management are some of the main problems. Therefore, this works introduces a ROS-compatible solution for Smart Resource services decoupling on modular robots. Smart Resources are defined as cyber-physical systems that provide high-level operation services. The design and analysis of a new distributed communication architecture for accessing Smart Resource services is addressed along this document. This architecture is called ROS Multi-Peer Architecture (RMPA) and features real-time communication, fully decoupled ROS device execution, and device discovery. So, the integration of RMPA in ROS based developments provides realtime access to the high-level supplied by the Smart Resources. This integration promotes the development of ROS-compatible robot modules based on the Smart Resource design. Next, a set of tests is presented to compare RMPA and ROS communication performance. Moreover, a detailed study of the RMPA performance is also addressed. Finally, as a result of these experiments main advantages and withdrawals of this solution are discussed leading to the establishment of future work and enhancements.

Real-Time Controller Based on FPGA and DSP for Solar Ground Layer Adaptive Optics Prototype System at 1-m NVST

Solar ground layer adaptive optics (GLAO), containing a large field of view (FOV) wavefront sensor (WFS) and one deformable mirror (DM), can be used to reduce and stabilize the seeing effectively over a wide FOV. As the brain of the GLAO system, the real-time controller (RTC) computes the commands to drive the DM according to the average wavefront errors measured by the multi-direction correlating Shack–Hartmann WFS, which is a time-consuming process. A customized RTC based on a high-speed field programming gate array and a multi-core digital signal processor was developed for the solar GLAO prototype system at the 1-m New Vacuum Solar Telescope. Several parallel acceleration techniques are used to reduce the computation time of the RTC. Compared with the previous RTCs, our RTC architecture has nearly no timing jitter. In this paper, the design of the RTC for our solar GLAO prototype will be introduced. The test results of the RTC are also presented. Moreover, the on-sky Sun observational results of the solar GLAO prototype are shown.

Robot programming by demonstration using teleoperation through imitation

PurposeThis paper aims to present a new learning from demonstration-based trajectory planner that generalizes and extracts relevant features of the desired motion for an industrial robot.Design/methodology/approachThe proposed trajectory planner is based on the concept of human arm motion imitation by the robot end-effector. The teleoperation-based real-time control architecture is used for direct and effective imitation learning. Using this architecture, a self-sufficient trajectory planner is designed which has inbuilt mapping strategy and direct learning ability. The proposed approach is also compared with the conventional robot programming approach.FindingsThe developed planner was implemented on the 5 degrees-of-freedom industrial robot SCORBOT ER-4u for an object manipulation task. The experimental results revealed that despite morphological differences, the robot imitated the demonstrated trajectory with more than 90 per cent geometric similarity and 60 per cent of the demonstrations were successfully learned by the robot with good positioning accuracy. The proposed planner shows an upper hand over the existing approach in robustness and operational ease.Research limitations/implicationsThe approach assumes that the human demonstrator has the requisite expertise of the task demonstration and robot teleoperation. Moreover, the kinematic capabilities and the workspace conditions of the robot are known a priori.Practical implicationsThe real-time implementation of the proposed methodology is possible and can be successfully used for industrial automation with very little knowledge of robot programming. The proposed approach reduces the complexities involved in robot programming by direct learning of the task from the demonstration given by the teacher.Originality/valueThis paper discusses a new framework blended with teleoperation and kinematic considerations of the Cartesian space, as well joint space of human and industrial robot and optimization for the robot programming by demonstration.

Control design, simulation and validation of a turbo-machinery auxiliary plant

In the oil and gas industry, the testing of auxiliary lubrication plants represents an important preliminary activity before the whole turbo machinery train (including the auxiliary lubrication plant) can be put in operation. Therefore, the employment of both efficient and accurate plant models becomes mandatory to synthesize satisfactory control strategies both for testing and normal operation purposes. For this reason, this paper focuses on the development of innovative real-time models and control architectures to describe and regulate auxiliary lubrication plants. In particular, according to the Bond-Graph modelling strategy, a novel lumped parameter model of the lube oil unit has been developed to properly optimize the behaviour of this unit if it is controlled. The code has been compiled and uploaded on a commercial real-time platform, employed to control the pressure control valve of the physical plant, for which a new controller has been developed. The comparison between the data obtained from the simulated system and acquired from the physical plant shows good agreement and the good performance and reliability of the proposed model and control strategy. The modelling approach and the control strategy have been developed in collaboration with GE Nuovo Pignone S.p.a. while the experimental data were acquired in a plant located in Ptuj (Slovenia).