Closed-loop Control Function Research Articles

Research on Educational Robot System Based on Vision Processing.

Aimed at the poor recognition effect of current educational robots on objects with complex shapes and colors and the single design of related experiments, this paper proposes a robot teaching instrument. The robot adopts a servo motor with an encoder, a drive, and a variety of sensors to realize a motor current loop, speed loop, position loop, and closed-loop control functions. Three experimental schemes were designed: a PID adjustment experiment, a robot obstacle avoidance and object-grasping program writing experiment, and a complex object recognition experiment based on cascade classifiers. The robot is conducive to improving students' self-initiative ability, deepening their understanding of PID closed-loop control, multi-sensor fusion, and deep learning knowledge. It can improve students' programming ability, enabling them to effectively combine theory and practice, as well as to comprehensively apply professional knowledge.

Minimisation of Failure Transients in a Fail-Safe Electro-Mechanical Actuator Employed for the Flap Movables of a High-Speed Helicopter-Plane

The work deals with the model-based characterization of the failure transients of a fail-safe rotary EMA developed by Umbragroup (Italy) for the flap movables of the RACER helicopter-plane by Airbus Helicopters (France). Since the reference application requires quasi-static position-tracking with high disturbance-rejection capability, the attention is focused on control hardover faults which determine an actuator runaway from the commanded setpoint. To perform the study, a high-fidelity nonlinear model of the EMA is developed from physical first principles and the main features of health-monitoring and closed-loop control functions (integrating the conventional nested loops architecture with a deformation feedback loop enhancing the actuator stiffness) are presented. The EMA model is then validated with experiments by identifying its parameters by ad-hoc tests. Simulation results are finally proposed to characterize the failure transients in worst case scenarios by highlighting the importance of using a specifically designed back-electromotive damper circuitry into the EMA power electronics to limit the position deviation after the fault detection.

Wind turbine wake position detection and rotor speed-based wake steering validation in a wind tunnel wake simulator

Wind farm control has demonstrated power production improvements using yaw-based wake steering compared to individual turbine optimization. However, slower yaw actuation rates in response to rapid inflow changes lend to impracticality of yaw-based steering, as it causes time-varying downstream rotor–wake overlap, power production fluctuation, and consequent reduction. Therefore, closed-loop wake control is required to mitigate wake deflection uncertainty. To respond to rapid inflow variations, rotor speed actuated is investigated here. Furthermore, wake position information is required as feedback for closed-loop control function. For field-installed turbines, nacelle-based Light detection and ranging (LIDAR) is expected to provide this information. So far, LIDAR-derived wake position has been determined through model-based field reconstruction of scattered LIDAR data. However, this requires sophisticated, economically prohibitive LIDARs. To incorporate inexpensive, two-beam LIDAR for wake detection, a tip vortex-based approach was developed and is also presented here. These contributions can be considered as intermediate steps toward realization of a novel closed-loop wake control.

Closed-Loop Control of Earth Observation Satellites

Low-altitude satellite orbits, while enabling high-resolution imagery of the Earth surface, have limited coverage properties. This disadvantage of the remote sensing satellites can be offset by the low-thrust electric propulsion capability, which permits to combine high-resolution with short revisit times. The purpose of this work is to present a simple closed-loop control function that allows the direct control of the orbit, making the spacecraft to pass over prescribed sites on the terrestrial surface without the need of precomputed reference trajectories. The simplicity of application contributes to the autonomy of the remote sensing satellites. The performance of the new control algorithm is illustrated by representative numerical simulation results.

Design of Parallel-Operated SEPIC Converters Using Coupled Inductor for Load-Sharing

This study discusses the design of a parallel-operated DC-DC single-ended primary-inductor converter (SEPIC) for low-voltage application and current sharing with a constant output voltage. A coupled inductor is used for parallel-connected SEPIC topology. Generally, two separate inductors require different ripple currents, but a coupled inductor has the advantage of using the same ripple current. Furthermore, tightly coupled inductors require only half of the ripple current that separate inductors use. In this proposed work, tightly coupled inductors are used. These produce an output that is more efficient than that from separate inductors. Two SEPICs are also connected in parallel using the coupled inductors with a single common controller. An analog control circuit is designed to generate pulse width modulation (PWM) signals and to fulfill the closed-loop control function. A stable output current-sharing strategy is proposed in this system. An experimental setup is developed for a 18.5 V, 60 W parallel SEPIC (PSEPIC) converter, and the results are verified. Results indicate that the PSEPIC provides good response for the variation of input voltage and sudden change in load.

The influence of the normal strain effect on the control and design optimization of functionally graded plates

A multiobjective design and control optimization problem for functionally graded (FG) plates is presented using a first-order plate theory including the normal strain effect. The aim of the optimization is to minimize the vibrational response and to maximize the buckling loads of FG plates with constraints on the control energy and plate thickness. An integrated approach for the simultaneous design and active control optimization is presented to determine the optimal level of a closed loop control function. Plate thickness and a homogeneity parameter of FG plates are used as design variables. Numerical results for the optimal control force and the total energy of FG plates are presented in various cases of boundary conditions. The influence of the normal strain effect on the accuracy of the obtained results is illustrated. The effectiveness of the present control and design procedures are examined.

Active Control Optimization for Minimizing the Dynamic Response of Functionally Graded Plate

A control optimization problem for functionally graded (FG) plates is presented using a first-order shear deformation plate theory including through-the-thickness normal strain effect. The aim of the optimization is to minimize the vibrational response of FG plate with constraints on the control energy used in the damping process. An active control optimization is presented to determine the optimal level of a closed loop control function. Plate thickness and a homogeneity parameter of FG plates are used as design variables. Numerical results for the optimal control force and the total energy for a simply supported FG plate are given. The influence of through-the-thickness normal strain effect on the accuracy of the obtained results is illustrated. The effectiveness of the present control and design procedure is examined.

Joystick in Closed-loop Control of ROVs with Experimental Results

In standard ROV operations a joystick command console is used for positioning control. The joystick command console controls the propeller speed of each thruster. A thrust allocation may be used for manual control in surge, sway, heave and yaw. Accurate station keeping or high precision moves require a skilled and concentrated pilot. Some ROV tasks, such as station keeping and trajectory tracking, can be automated by a closed-loop positioning control system. However, for tasks such as inspection of an unknown object or complex manipulation work, the desired trajectory is not known in advance, and must be decided by a pilot based on view from ROV cameras or other sensor data. In that case, the pilot should have an easy way of guiding the ROV without spending a lot of effort on the positioning control itself. The low level position control should be automated by a controller that compensates for ROV dynamics and environmental loads. A joystick with closed-loop control functions is proposed in this paper. Joystick inputs will generate desired velocities or positions rather than direct thruster speed commands. The control of desired states is done by a closed-loop positioning system with feedback. The methods for the proposed joystick control modes are described in this paper. Full scale experiments are presented demonstrating the performance of the joystick in closed-loop control.

Bidirectional Communication System for Magnetic Direct Feeding FES

Functional electrical stimulation (FES) is a type of therapy used for paralyzed patients. In FES, the implant direct feeding method is an ideal stimulus method. In this method, small stimulators are implanted in the paralyzed limbs, and magnetic coupling is used to simultaneously power the implants and enable digital communication with the mounted system. To realize this method, we have developed an implant antenna (magnetic connective dual-resonance antenna) that can transmit as well as receive signals and a mounted communication system that is responsible for supplying power and communication from outside the body to the implanted antenna inside of the body. However, to guarantee safe stimulation, this system requires the closed-loop control function. For this purpose, we have proposed a communication protocol that is inexpensive, and a new communication system that supports bidirectional communication. In this paper, we present the new protocol, the composition and mechanisms of the proposed system, and the experimental results that verify the efficiency of this system.

DSP Based Series-Parallel Connected Two Full-Bridge DC-DC Converter with Interleaving Output Current Sharing

Input-series-output-parallel (ISOP) connected DC-DC converters enable low voltage rating switches to be used in high voltage input applications. In this paper, a DSP is adopted to generate digital phase-shifted PWM signals and to fulfill the closed-loop control function for ISOP connected two full-bridge DC-DC converters. Moreover, a stable output current sharing control strategy is proposed for the system, with which equal sharing of the input voltage and the load current can be achieved without any input voltage control loops. Based on small signal analysis with the state space average method, a loop gain design with the proposed scheme is made. Compared with the conventional IVS scheme, the proposed strategy leads to simplification of the output voltage regulator design and better static and dynamic responses. The effectiveness of the proposed control strategy is verified by the simulation and experimental results of an ISOP system made up of two full-bridge DC-DC converters.

A Fabry–Pérot electro-optic sensing system using a drive-current-tuned wavelength laser diode

A Fabry-Pérot enhanced electro-optic sensing system that utilizes a drive-current-tuned wavelength laser diode is presented. An electro-optic prober made of LiNbO(3) crystal with an asymmetric Fabry-Pérot cavity is used in this system. To lock the wavelength of the laser diode at resonant condition, a closed-loop power control scheme is proposed. Experiment results show that the system can keep the electro-optic prober at high sensitivity for a long working time when the closed-loop control function is on. If this function is off, the sensitivity may be fluctuated and only one-third of the best level in the worst case.

マシニングセンタ型ナノ加工・計測システムの開発に関する研究

A small precision nanomachining and measurement system was developed with a targeted machining resolution on the order of scales ranging from submicrons to several nanometers. The system was comprised of two machining functions, scratch machining and milling, and one measurement function. The scratch machining function was based on a frictional force microscope mechanism with a closed-loop numerical control (NC) to control the depth of the cut. A stiff cantilever was used for the scratch-machining function to permit nanomachining of hard and brittle materials such as silicon. The milling function used an original miniature tool that had a very small diamond mounted on it that permitted micromachining. The measurement function incorporated into this system used the same mechanism as the scratch-machining function, and provided a degree of precision almost equal to that of atomic force microscopy. After constructing this system, we performed various machining tests with it to confirm that the integrated NC closed-loop control function performed correctly.

Sensory applications in cars

Today’s motor vehicles are equipped with a multitude of sensors. These components convert physical input variables into electrical signals that are needed by the engine management's electronic control unit and by the safety and convenience systems for open and closed-loop control functions. This article by Infineon Technologies AG, Munich, provides an overview of the areas of application for micromechanical pressure sensors in cars, and it discusses future requirements and trends.

Structural and control optimization for maximum thermal buckling and minimum dynamic response of composite laminated plates

A multiobjective optimization problem is presented to determine the optimal layer thickness and optimal closed loop control function for a symmetric cross-ply laminate subjected to thermomechanical loadings. The optimization procedure aims to maximize the critical combination of the applied edges load and temperature levels and to minimize the laminate dynamic response subject to constraints on the thickness and control energy. The objective of the optimization problem is formulated based on a consistent first-order shear deformation theory without introducing a shear correction factor. The dynamic response is measured as the sum of the total elastic energy of the laminate and a penalty term involving a closed loop control force. Laipunov–Bellman theory is used to obtain solutions for the controlled deflections and optimal control force. The layer thickness is taken as a design variable, and is presented as a function of the number of layers. A numerical study is made for simply supported symmetric laminates with an odd number of layers to show the advantages of the present control optimization. The study indicates that the present control optimization is active with most laminates cases for all values of aspect ratio, number of layers, orthotropy ratio, thermal expansions ratio and thickness ratio.

Performance and maintenance requirements of active control systems

Vehicle designers are continually looking for methods to improve in-cabin noise vibration and harshness (NVH). Active control systems offer a variety of techniques for low-frequency NVH control. Active systems allow the designer to trade between the factors of NVH performance, weight, package space, and cost. Examples of systems are active interior sound control and active-mounts/active-vibration control. The performance of these systems directly impacts the sound and vibration field, to which the operator and passengers are exposed. The system stability and robustness must be monitored and maintained at all times. The focus of this paper will be on active interior systems, highlighting performance and diagnostics. The closed loop control functions found in most active systems present unique opportunities for system maintenance and diagnostics. Several methods for component diagnostics will be discussed. Also, the diagnostic advantages of stand-alone and integrated active systems will be considered.

Managing power system security and optimization

PEPCO's new EMS provides unique security and optimization strategies for generation, transmission, and distribution systems via a coordinated suite of real-time closed-loop control functions. The authors discuss the security functions real-time sequence, control hierarchy, optimisation control objectives, contingency-condition optimisation, emergency mode operation, underground transmission network control objectives, radial load bus voltage control objectives, control sequencing, and control execution.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low Cost Digital Controller for PWM Converter

The design of a compact control system for a sinusoidal PWM transistor inverter is presented. The hardware of the control system consists of 16-bit microcontroller with a few additional components. The PWM signales are generated in a digital way. In addition to generation of the PWM signals, the microcontroller performs closed loop control functions. Both sampling frequency and PWM carrier frequency can be adjusted by software, according to the requirments from the digital controller and the power transistors used in converter. The sampling frequency is up to several KHz, and the carrier frequency from less than 1 KHz to 46 KHz. Interaction with an operator or an on-line supervisory computer is provided through a serial communication, digital port or analog input lines. Simulation and experimental test results from an implementation of the control system on a high power IGBT inverter are given.

Present SLAC Accelerator Computer Control System Features

The current functional organization and state of software development of the computer control system of the Stanford Linear Accelerator is described. Included is a discussion of the distribution of functions throughout the system, the local controller features, and currently implemented features of the touch panel portion of the system. The functional use of our triplex of PDP11-34 computers sharing common memory is described. Also included is a description of the use of pseudopanel tables as data tables for closed loop control functions.

Bevatron Guide Field Control

The Bevatron guide field power supply has been under computer control for one year. This facility allows operational parameters to be programmed at operator request in order to provide the desired field profiles commensurate with the current experimental program. With a requirement of one part in fifteen thousand accuracy for resonant extraction, the digital system has been enlarged until a realtime closed-loop control function meet this specification. A one gauss window for entry into flat-zones is now maintained, while a relative flatness tolerance of ±1/ 2 gauss is held during the typical 2-sec. flatzone. This paper includes the structure of a new data-acquisition system with emphasis upon the use of a fast magnetic-core memory to gather blocks of data, as well as to hold the necessary digital threshold values to be arithmetically compared with the results of the data gathering facility. Also covered, is the implementation of the system in the detection and ultimate reduction of incipient fault conditions within the guide field power supply.

An approximate minimal time closed-loop controller for processes with bounded control amplitudes and rates

This paper presents a method for designing an approximate minimal time closed-loop controller for linear systems with bounded control amplitudes and rates. The method is based on obtaining an approximate functional expression (explicitly in terms of the state variables) that describes the minimal time isochrones of the system. This expression is obtained by a series of least-squares fits to the computed system states on the various isochrones. The computation of the system states on the isochrones and the determination of the approximate expressions are achieved off-line. For on-line operation, it is only required to store a limited number of coefficients of the approximate expressions, and to compute the closed-loop control function by some algebraic manipulation. Consequently, the on-line computer storage requirement as well as the on-line computation requirement is relatively small. Thus, the method is feasible for high-order practical systems. To evaluate its usefulness in applications, the scheme is used to design a fourth-order Ranger Block III Attitude Control System. The results are compared to those obtained by applying the minimal time open-loop control.