Low-level Control System Research Articles

Abstraction, Sensory-Motor Coordination, and the Reality Gap in Evolutionary Robotics.

One of the major challenges of evolutionary robotics is to transfer robot controllers evolved in simulation to robots in the real world. In this article, we investigate abstraction of the sensory inputs and motor actions as a tool to tackle this problem. Abstraction in robots is simply the use of preprocessed sensory inputs and low-level closed-loop control systems that execute higher-level motor commands. To demonstrate the impact abstraction could have, we evolved two controllers with different levels of abstraction to solve a task of forming an asymmetric triangle with a homogeneous swarm of micro air vehicles. The results show that although both controllers can effectively complete the task in simulation, the controller with the lower level of abstraction is not effective on the real vehicle, due to the reality gap. The controller with the higher level of abstraction is, however, effective both in simulation and in reality, suggesting that abstraction can be a useful tool in making evolved behavior robust to the reality gap. Additionally, abstraction aided in reducing the computational complexity of the simulation environment, speeding up the optimization process. Preeminently, we show that the optimized behavior exploits the environment (in this case the identical behavior of the other robots) and performs input shaping to allow the vehicles to fly into and maintain the required formation, demonstrating clear sensory-motor coordination. This shows that the power of the genetic optimization to find complex correlations is not necessarily lost through abstraction as some have suggested.

Precision Control and Dynamic Positioning of ROVS in Intervention Operations

A smart Remotely Operated Vehicle, ROV LATIS, is a prototype platform to test and validate OceanRINGS - a suit of smart technologies for subsea operations, developed at Mobile & Marine Robotics Research Centre, University of Limerick. It is a next generation smart ROV with unique features, including multiple modes of operation, advanced 2D and 3D displays, intuitive, versatile and easy to use pilot interface, built-in autotuning of low-level controllers, voice navigation and fault-tolerant control system. With integrated state-of-the-art navigation sensors/instruments, the vehicle can achieve precision navigation and subsea positioning.

Supervisory Fuzzy Expert Controller for Sag Mill Grinding Circuits: Sungun Copper Concentrator

ABSTRACTSuccessful control of Semi-Autogenous Grinding (SAG) mill circuits has been the subject of many researches and main concern of plant operators for years. Distributed Control Systems (DCS) have had some degree of success in the mineral processing circuits, but maintaining operation of a SAG mill on the “edge” of its full capacity is not easily achievable by DCS. Advanced control systems, however, are a relatively new opportunity to successful control of mineral processing plants. This article presents the basis of a supervisory fuzzy expert controller for SAG mill circuits. Although leading companies in control and automation have their own commercial packages, this supervisory controller is coded in Matlab using Mamdani method and is able to connect to plant lower level control system. In the proposed controller, fuzzy system calculates optimum set points to the plant DCS control loops, enabling them to change the manipulating parameters to reach the new set points. This controller was installed, tested and verified in a copper grinding circuit. Results showed 1.8% increase in mill throughput, 3% decrease in power draw and more stable feeding regime at the same time.

Design and analysis of a bio-inspired module-based robotic arm

Abstract. This paper presents a novel bio-inspired modular robotic arm that is purely evolved and developed from a mechanical stem cell. Inspired by stem cell whilst different from the other robot "cell" or "molecule", a fundamental mechanical stem cell is proposed leading to the development of mechanical cells, bones and a Sarrus-linkage-based muscle. Using the proposed bones and muscles, a bio-inspired modular-based five-degrees-of-freedom robotic arm is developed. Then, kinematics of the robotic arm is investigated which is associated with an optimization-method-based numerical iterative algorithm leading to the inverse kinematic solutions through solving the non-linear transcendental equations. Subsequently, numerical example of the proposed robotic arm is provided with simulations illustrating the workspace and inverse kinematics of the arm. Further, a prototype of the robotic arm is developed which is integrated with low-level control systems, and initial motion and manipulation tests are implemented. The results indicate that this novel robotic arm functions appropriately and has the virtues of lower cost, larger workspace, and a simpler structure with more compact size.

Functional Design of a Powered Elbow Orthosis Toward its Clinical Employment

This paper presents the design and preliminary evaluation of a novel version of the robotic elbow exoskeleton NEUROExos, designed for the in-clinic treatment of stroke survivors in acute and subacute phases. The robotic design implements a novel series elastic actuation system, a 4-degree-of-freedom (DoFs) passive mechanism for the anatomical axis alignment, and one active DoF with remote cable-driven actuation. The low-level control system allows two working modalities: a torque control and a joint position control. The high-level control system employs a finite-state machine that allows the setting and execution of these modalities during rehabilitation exercises. Preliminary pilot tests based on passive exercises, with three chronic post-stroke patients, demonstrated the effectiveness of the proposed approach in assessing joint rigidity and its usability within a rehabilitation clinic.

Development of a Low-Level Control System for the ROV Visor3

This paper addresses the development of the simulation of the low-level control system for the underwater remotely operated vehicle Visor3. The 6-DOF mathematical model of Visor3 is presented using two coordinated systems: Earth-fixed and body-fixed frames. The navigation, guidance, and control (NGC) structure is divided into three layers: the high level or the mission planner; the mid-level or the path planner; and the low level formed by the navigation and control systems. The nonlinear model-based observer is developed using the extended Kalman filter (EKF) which uses the linearization of the model to estimate the current state. The behavior of the observer is verified through simulations using Simulink®. An experiment was conducted with a trajectory that describes changes in the x and y and yaw components. To accomplish this task, two algorithms are compared: a multiloop PID and PID with gravity compensation. These controllers and the nonlinear observer are tested using the 6-DOF mathematical model of Visor3. The control and navigation systems are a fundamental part of the low-level control system that will allow Visor3’s operators to take advantage of more advanced vehicle’s capabilities during inspection tasks of port facilities, hydroelectric dams, and oceanographic research.

High-accuracy diagnostic tool for electron cloud observation in the LHC based on synchronous phase measurements

Electron cloud effects, which include heat load in the cryogenic system, pressure rise, and beam instabilities, are among the main intensity limitations for the LHC operation with 25 ns spaced bunches. A new observation tool was proposed and developed to monitor the e-cloud activity and it has already been used successfully during the LHC run 1 (2010-2012) and it is being intensively used in operation during the start of the LHC run 2 (2015-2018). It is based on the fact that the power loss of each bunch due to e-cloud can be estimated using bunch-by-bunch measurement of the synchronous phase. The measurements were done using the existing beam phase module of the low-level rf control system. In order to achieve the very high accuracy required, corrections for reflection in the cables and for systematic errors need to be applied followed by a post-processing of the measurements. Results clearly show the e-cloud buildup along the bunch trains and its time evolution during each LHC fill as well as from fill to fill. Measurements during the 2012 LHC scrubbing run reveal a progressive reduction in the e-cloud activity and therefore a decrease in the secondary electron yield. The total beam power loss can be computed as a sum of the contributions from all bunches and compared with the heat load deposited in the cryogenic system.

RCCS operation with a resonant frequency error in the KOMAC

The resonance control cooling systems (RCCSs) of the Korea Multi-purpose Accelerator Complex have been operated for cooling the drift tubes (DT) and controlling the resonant frequency of the drift tube linac (DTL). The DTL should maintain a resonant frequency of 350 MHz during operation. A RCCS can control the temperature of the cooling water to within ±0.1 °C by using a 3-way valve opening and has a constant-cooling-water-temperature control mode and resonant-frequency-control mode. In the case of the resonant-frequency control, the error in the frequency is measured by using the low-level radio-frequency control system, and the RCCS uses a proportional-integral-derivative control algorithm to compensate for the error by controlling the temperature of the cooling water to the DT.

Operational Optimization of High Voltage Power Station Based Fuzzy Logic Intelligent Controller

This paper discusses the use of the intelligent microcontroller and also discusses the results from the simulation application of fuzzy logic theory to the control of the high voltage direct and alternation current (HVDC)& (HVAC) power station systems. The application considered their implementation in both low and high level control systems in HVDC& HVAC power station systems. The results for the fuzzy logic based controller shows many improvements compared to the conventional HVDC& HVAC control system. The fuzzy logic based controller concept was further successfully extended to high level control of optimization problems such as the power swings. Based on simulation results, HVDC and HVAC breaker design are online protection against unwanted incidents happening to the system.

A Real-Time Robust Fuzzy-based Level Control using Programmable Logic Controller

Industrial software are specially designed to meet specific process. And sometimes this software can be very expensive. One way to reduce this cost is to develop own algorithm. This paper presents a real-time liquid level control implementation for an industrial process. The implementation of the level control is achieved using a fuzzy-based control algorithm. A Programmable Logic Controller (PLC) was used in which the fuzzy control algorithm has been embedded and can withstand against abrupt changes in the outlet flow. In addition, the fuzzy control algorithm is introduced to the system without a fuzzy module or software package. As a consequence, a robust and low cost liquid level control system has been realized. A Mamdani Fuzzy Inference System (MFIS) has been proposed. Membership functions of the input and output variables of the system were obtained and verified using Matlab/Simulink environment. The obtained functions have been used for the construction of fuzzy control algorithm in PLC. A robust fuzzy-based level controller has been achieved and quite satisfactory results were obtained in real-time implementation for different outlet flow rates. DOI: http://dx.doi.org/10.5755/j01.eee.21.1.7812

The MxCuBE2/ISPyB environment for remote data collection at the ESRF

MxCuBE, is a beamline control graphical user interface (GUI) for macromolecular crystallography (MX) experiments that was developed by the ESRF and has been in use since 2005. The GUI provides the user with a friendly interface to electronic devices, permitting to carry out experiments in a intuitive environment while benefiting from the increasing automation. Since its release, MxCuBE has become the preferred MX data acquisition software, also installed at other European synchrotron sites [SOLEIL, EMBL@PETRAIII, BESSY and MAXLAB].In September 2013, after intense recoding, experiment design and testing, the ESRF has deployed MxCuBE2 on all the ESRF's MX beamlines. This new generation of GUI is capable of interfacing with a variety of low level control systems. MxCuBE2, written in the Python programming language, has a radical new appearance and provides an updated environment for performing complicated multi-crystal/multi-position MX experiments in a modular, logical and automatic fashion. ISPyB is a Laboratory Information Management System (LIMS) conceived to record experimental parameters and basic reporting of the data obtained. Since 2009 ISPyB has been a collaboration between ESRF and Diamond Light Source (DLS) and the LIMS is now a multi-site, generic system for synchrotron-based (MX) experiments. The current version allows users to track their sample location (to/from & at the synchrotron), facilitates transmission of information from and to other LIMS, records experiment details, and provides the results - including reflection files - of automatic data processing protocols. Indeed as experiments have become more complex and automated ISPyB has become more than just a repository for project histories - it has become a support for rapid decision making during experiments. The combination of these two indispensable tools in every day users life at the European Synchrotron Radiation Facility will be presented and discussed.

Integration of Drive-by-Wire with Navigation Control for a Driverless Electric Race Car

This article presents the design and implementation of a drive-by-wire system and a navigation control system for an autonomous Formula SAE race car. The result is the development of a platform for research into autonomous driving which can be easily replicated. Drive-by-wire actuators for acceleration, braking and steering of the vehicle are discussed, as well as the embedded low-level control system. The high-level navigation system features sensor fusion of a 6-dof IMU with a standard GPS and the integration of an automotive LIDAR. Operation of the vehicle is via a multi-threaded program with asynchronous IO and is based upon recording and driving waypoints. In addition to independent safety interlocks, active safety systems are an integral part to both the drive-by-wire and navigation systems.

Development of a low-level RF control system for PET cyclotron CYCIAE-14

The project of a 14MeV PET cyclotron aiming at medical diagnosis and treatment was proposed and started at CIAE in 2010. The low-level RF system is designed to stabilize acceleration voltage and control the resonance of the cavity. Based on the experience of the existing CRM Cyclotron in CIAE, a new start-up sequence is developed and tested. The frequency sweeping is used to activate the RF system. Before the tuner is put into use, a new state called “DDS tuning” is applied to trace the resonance frequency to the designed value. This new option state helps to cover the tuning range, if a large frequency variation occurs because of a thermal cavity deformation. The logic control unit detects the spark, reflection, Pulse/CW state and the frequency of the RF source to perform all kinds of protection and state operations. The test bench and on-line test are carried out to verify the initial design.

Analysis for Operation Control System Based on IDEF Method

The optimal operation of the process is achieved as a whole by analyzing the hierarchical control system for industrial process operation based on IDEF method. A loop setting controller is projected for the generalized object consisting of the controlled process and the lower-level control system by using the IDEF method. According to the desired technical indices, the loop setting controller is able to automatically adjusts the set points for the lower-level controllers from top to bottom, meet the requirements of operation control for the production process, ensure the quality of products and stable operation of the production process.

EPICS based low-level radio frequency control system in LIPAc

The IFMIF–EVEDA (International Fusion Materials Irradiation Facility – Engineering Validation and Engineering Design Activity) linear accelerator, known as Linear IFMIF Prototype Accelerator (LIPAc), will be a 9MeV, 125mA continuous wave (CW) deuteron accelerator prototype to validate the technical options of the accelerator design for IFMIF. The primary mission of such facility is to test and verify materials performance when subjected to extensive neutron irradiation of the type encountered in a fusion reactor to prepare for the design, construction, licensing and safe operation of a fusion demonstration reactor (DEMO). The radio frequency (RF) power system of IFMIF–EVEDA consists of 18 RF chains working at 175MHz with three amplification stages each. The low-level radio frequency (LLRF) controls the amplitude and phase of the signal to be synchronized with the beam and it also controls the resonance frequency of the cavities. The system is based on a commercial compact peripheral component interconnect (cPCI) field programmable gate array (FPGA) board, provided by Lyrtech and controlled by a Windows host PC. For this purpose, it is mandatory to communicate the cPCI FPGA board from EPICS Channel Access [1]. A software architecture on EPICS framework in order to control and monitor the LLRF system is presented.

A low-level rf control system for a quarter-wave resonator

A low-level rf control system was designed and built for an rf deflector, which is a quarter wave resonator, and was designed to deflect a secondary electron beam to measure the bunch length of an ion beam. The deflector has a resonance frequency near 88 MHz, its required phase stability is approximately ±1° and its amplitude stability is less than ±1%. The control system consists of analog input and output components and a digital system based on a field-programmable gate array for signal processing. The system is cost effective, while meeting the stability requirements. Some basic properties of the control system were measured. Then, the capability of the rf control was tested using a mechanical vibrator made of a dielectric rod attached to an audio speaker system, which could induce regulated perturbations in the electric fields of the resonator. The control system was flexible so that its parameters could be easily configured to compensate for the disturbance induced in the resonator.

Low Level Control Layer Definition for Autonomous Vehicles Based on Fuzzy Logic

Abstract The intelligent control of autonomous vehicles is one of the most important challenges that intelligent transport systems face today. The application of artificial intelligence techniques to the automatic management of vehicle actuators enables the different Advanced Driver Assistance Systems (ADAS) or even autonomous driving systems, to perform a low level management in a very similar way to that of human drivers by improving safety and comfort. In this paper, we present a control schema to manage these low level vehicle actuators (steering throttle and brake) based on fuzzy logic, an artificial intelligence technique that is able to mimic human procedural behavior, in this case, when performing the driving task. This automatic low level control system has been defined, implemented and tested in a Citroen C3 testbed vehicle, whose actuators have been automated and can receive control signals from an onboard computer where the soft computing-based control system is running.

RF system of HIRFL-CSRe

The operational frequency range of RF system at HIRFL-CSRe (cooling storage experimental ring) is 0.5–2 MHz, and it works in fundamental and second harmonic. It includes five sections: ferrite ring loaded RF cavity, RF generator, low-level system, computer system and cavity cooling. The cavity is based on the coaxial resonator type which is short at the terminal with one gap and loaded with domestic ferrite rings. The RF generator is designed in a push-pull mode. The low-level control system is based on PID, DSP, FPGA and DDS9854+USB interface and has three feedback loops. This RF system is designed independently and manufactured domestically. For the first time, it realized the pulse modulation, variable harmonic and CW operational modes. The maximum output power is up to 70 kW and the 10 kV RF voltage is used to capture the irradiative beam and decelerate the beam from 400 to 30 MeV/u.

Intelligent Operation Control for the Fused Magnesia Production

An electro-fused magnesia furnace (EFMF) is used to produce electro-fused magnesia. Due to the complex dynamic characteristics of the EFMF production process, it is difficult to achieve the satisfactory control performances only by the independent conventional control method. As a result, the lower loop control with manual operations is still widely used in practice. However, the manual operation cannot ensure that the actual production qualities and the energy consumption of unit production meet the technical requirements all the time. In this paper, an intelligent operation control strategy is developed for the EFMF to automatically adjust the setpoints of the lower level control system. Based on the proposed intelligent control strategy, an intelligent control system for the EFMF is built and implemented on site. Industrial application has demonstrated that the intelligent control system can achieve reliable, accurate and timely control performances.

Design of Intelligent Rehabilitation Crutch Based on Accelerometer

In order to meet the daily needs of the elderly patients and walking ability of injury rehabilitation, design an intelligent rehabilitation crutch. This design combine with empowered walking aid’s mechanical features and robot technology, its signal is collected by MMA7260 accelerometer, this greatly improved the sensitivity direction without swerve on the plane through the analysis of the acceleration signal processing and controlling the velocity composition of three omnidirectional wheel rounds of synthesis of all to realize the intelligent walking stick of the whole direction and intellectuality of the walking aids. The motion mechanism of crutch using omnidirectional wheel structure and using ATmega 16 microcontroller to establish low-level control system. The crutch can move in any n of free movement. The kinematics analysis shows the design feasibility. In the manual and automatic control experiments, it can meet designer quarrymen’s and achieve design function.