Velocity Loop Research Articles

Statement of Problem of Pareto Frontier Management and Its Solution in the Analysis and Synthesis of Optimal Systems

The article research concerns the multi-criteria optimization (MCO), which assumes that operation quality criteria of the system are independent and specifies a way to improve values of these criteria. Mutual contradiction of some criteria is a major problem in MCO. One of the most important areas of research is to obtain the so-called Pareto - optimal options. The subject of research is Pareto front, also called the Pareto frontier. The article discusses front classifications by its geometric representation for the case of two-criterion task. It presents a mathematical description of the front characteristics using the gradients and their projections. A review of current domestic and foreign literature has revealed that the aim of works in constructing the Pareto frontier is to conduct research in conditions of uncertainty, in the stochastic statement, with no restrictions. A topology both in two- and in three-dimensional case is under consideration. The targets of modern applications are multi-agent systems and groups of players in differential games. However, all considered works have no task to provide an active management of the front. The objective of this article is to discuss the research problem the Pareto frontier in a new production, namely, with the active co-developers of the systems and (or) the decision makers (DM) in the management of the Pareto frontier. It notes that such formulation differs from the traditionally accepted approach based on the analysis of already existing solutions. The article discusses three ways to describe a quality of the object management system. The first way is to use the direct quality criteria for the model of a closed system as the vibrational level of the General form. The second one is to study a specific two-loop system of an aircraft control using the angular velocity and normal acceleration loops. The third is the use of the integrated quality criteria. In all three cases, the selected criteria are mutually contradictory and it is possible to use them for description in the Pareto frontier terms. Techniques for the active influence on the Pareto frontier have allowed us to define parameters not only of the system regulators, but the control object itself, which permit changing the front position. The article analyses the impact of these parameters on the angles of the front, calculated, using the second derivative of the criterion, by the first dJ2/dJ1. It notes that derivatives may act as an assessment of the balance of compromises. The work reveals that for a General form model the change in natural frequency (time constant) has inversely proportional impact on the tilt of Pareto frontier, i.e. the smaller the time constant, the steeper is front, i.e. it is possible to control the front tilt through changing the time constant. Thus, reducing the time constant leads to the left-hand shift of the Pareto frontier. As to the two-loop system, it shows that the increasing gain module of the angular velocity sensor causes compression of the Pareto frontier in overshoot and stretching time of the transition process. Here, a tilt of the Pareto frontier slightly changes. The increasing module of the sensor linear acceleration gain causes the left-hand shift of the Pareto frontier with simultaneously increasing angle of the front tilt, i.e. its sensitivity increases. The computations of the corresponding Pareto ranks showed that for two-loop system, each of the individual ranks corresponds to the variation of the coefficient of linear acceleration sensor at different gain values of the angular velocity sensor, and if the latter is modulo limited from below, it is necessary to move to the next Pareto rank. Found that the change of dynamic coefficient related to the efficiency of the elevator control has the greatest effect. Using the integral criteria gives the same effect. The influence of other factors on the Pareto frontier is insignificant for direct quality indicators. It is, however, far more effective for the integral criteria. For the latter, as noted, there is an equilibrium point on the graph of the derivatives. Taking into consideration the rather complex functions of integral parameters, the article presents the approximating dependences obtained and notes the usefulness of applying this approach to more extensive scope of research without additional modeling. Thus, the article offers a new formulation as applied to the study of the Pareto frontier, namely, active control of the front by changing the parameters of the controllers and the object properties and shows a particular implementation of the synthesis of control systems for aircrafts.

A PD path-tracking controller plus inner velocity loops for a wheeled mobile robot

In this paper, we present a controller to solve the path-tracking task in a wheeled mobile robot. We show that a linear PD controller, driven by the tracking error, can be used to generate the desired profiles to be tracked by the motor velocities by means of two linear inner proportional-integral loops. We formally prove that an ultimate bound exists which can be rendered small by a suitable selection of the controller gains. This is the first time that such a result is presented in the literature when considering, simultaneously, both the kinematic and the dynamic models of the wheeled mobile robot.

Experimental study on stand-alone assistive suspension system to reduce load on small robot manipulating heavy payload

This paper presents a single degree of freedom suspension system to assist small six degree of freedom robots manipulating heavy payload. The goal of the system is to reduce the load applied to the last link of a robot manipulating a payload that is heavier than the robot’s specified allowable load capacity. An assistive suspension system was implemented to realize vertical-only motion of the robot. A mathematical model was derived, and a proportional-integral-derivative controller with an inner velocity loop was designed. Variable parameters in the model such as friction coefficients were identified in an experiment on the voltage input and velocity output. To determine how much the assistive system reduces the load on the robot, the system was connected to the robot using an interface attached with magnets and a force sensor was fixed to the last link of the robot. In the experiment, the cable tension was measured and controlled to satisfy the design preference for the assistive system to be stand-alone, rather than relying on force sensor on the robot. The experiment was performed using various control gains under different conditions, such as the periods of input motion and payload weight. The results showed that the system could reduce 3.8 and 6.0 kg payloads on the robot to 50% and 40%, respectively.

Doppler-derived intracoronary physiology indices predict the occurrence of microvascular injury and microvascular perfusion deficits after angiographically successful primary percutaneous coronary intervention.

A total of 40% to 50% of patients with ST-segment-elevation myocardial infarction develop microvascular injury (MVI) despite angiographically successful primary percutaneous coronary intervention (PCI). We investigated whether hyperemic microvascular resistance (HMR) immediately after angiographically successful PCI predicts MVI at cardiovascular magnetic resonance and reduced myocardial blood flow at positron emission tomography (PET). Sixty patients with ST-segment-elevation myocardial infarction were included in this prospective study. Immediately after successful PCI, intracoronary pressure-flow measurements were performed and analyzed off-line to calculate HMR and indices derived from the pressure-velocity loops, including pressure at zero flow. Cardiovascular magnetic resonance and H2 (15)O PET imaging were performed 4 to 6 days after PCI. Using cardiovascular magnetic resonance, MVI was defined as a subendocardial recess of myocardium with low signal intensity within a gadolinium-enhanced area. Myocardial perfusion was quantified using H2 (15)O PET. Reference HMR values were obtained in 16 stable patients undergoing coronary angiography. Complete data sets were available in 48 patients of which 24 developed MVI. Adequate pressure-velocity loops were obtained in 29 patients. HMR in the culprit artery in patients with MVI was significantly higher than in patients without MVI (MVI, 3.33±1.50 mm Hg/cm per second versus no MVI, 2.41±1.26 mm Hg/cm per second; P=0.03). MVI was associated with higher pressure at zero flow (45.68±13.16 versus 32.01±14.98 mm Hg; P=0.015). Multivariable analysis showed HMR to independently predict MVI (P=0.04). The optimal cutoff value for HMR was 2.5 mm Hg/cm per second. High HMR was associated with decreased myocardial blood flow on PET (myocardial perfusion reserve <2.0, 3.18±1.42 mm Hg/cm per second versus myocardial perfusion reserve ≥2.0, 2.24±1.19 mm Hg/cm per second; P=0.04). Doppler-flow-derived physiological indices of coronary resistance (HMR) and extravascular compression (pressure at zero flow) obtained immediately after successful primary PCI predict MVI and decreased PET myocardial blood flow. http://www.trialregister.nl. Unique identifier: NTR3164.

On the stability and accuracy of high stiffness rendering in non-backdrivable actuators through series elasticity

This paper addresses the problem of accuracy and coupled stability of stiffness-controlled series elastic actuators, where the motor is modeled as a non-backdrivable velocity source, and the desired value of virtual stiffness is above the physical stiffness of the compliant element. We first demonstrate that, in the mentioned conditions, no linear outer-loop force control action can be applied on the velocity-sourced motor to passify the system. Relaxing the constraint of passivity, we exhaustively search the control design space defined by parametric force and stiffness controllers, expressed in a general lead-lag form, and define a lead-type stiffness compensator that results in acceptable conditions for both coupled stability and accuracy. We also address the effect of a non-ideality in the velocity control loop, such as limited-bandwidth velocity control, and derive relationships between the value of the inner velocity loop time constant and parameters of the stiffness compensator that provide the best performance in terms of both stability and accuracy of haptic display.We show that the parameters of a simple outer-loop stiffness compensator can be optimized to result in a stable and accurate display of virtual environments with stiffness values in a large range, that also comprises values of virtual stiffness higher than the physical stiffness of the compliant element. A requirement for coupled stability is that the actuator is designed such that the minimum value of inertia connected to the compliant actuator load is higher than a control-defined threshold. Finally, we extensively analyze how the minimum value of interaction mass for coupled stability can be minimized through modulation of the stiffness compensator zeros and poles, considering realistic limitations in the velocity control bandwidth of non-backdrivable motors. Our analysis, validated through both numerical simulations and experiments, opens the possibility for alternative approaches to the design of compliant actuators, whereby rendering of high stiffness is possible if the load mass is always higher than a determined threshold.

Adaptive sliding mode control for re-entry attitude of near space hypersonic vehicle based on backstepping design

Combining sliding mode control method with radial basis function neural network (RBFNN), this paper proposes a robust adaptive control scheme based on backstepping design for re-entry attitude tracking control of near space hypersonic vehicle (NSHV) in the presence of parameter variations and external disturbances. In the attitude angle loop, a robust adaptive virtual control law is designed by using the adaptive method to estimate the unknown upper bound of the compound uncertainties. In the angular velocity loop, an adaptive sliding mode control law is designed to suppress the effect of parameter variations and external disturbances. The main benefit of the sliding mode control is robustness to parameter variations and external disturbances. To further improve the control performance, RBFNNs are introduced to approximate the compound uncertainties in the attitude angle loop and angular velocity loop, respectively. Based on Lyapunov stability theory, the tracking errors are shown to be asymptotically stable. Simulation results show that the proposed control system attains a satisfied control performance and is robust against parameter variations and external disturbances.

Non-Linear PID Controller Parameter Optimization of Vertical Take-Off and Landing Stage for Tilt Rotor Aircraft

Proportion, integration and differential gain of nonlinear PID Controller is nonlinear function of controlling error. This paper performed the non-linear PID controller parameter optimization of vertical take-off and landing stage for tilt rotor aircraft using the genetic algorithm. Dual loop control is used. Inner loop is angular velocity loop. Outer loop is angular position loop. According to the features of stability control of vertical take-off and landing stage of tilt rotor aircraft, system ascend time, steady error, and weighted overshoot are chosen as objective function of optimization. Simulation results show that controller designed by the present method can meet the requirement of control.

Parameter Identification of NC-Axes during Regular Operation of a Machine Tool

Monitoring functions of machine tools are of increasing importance to enhance their productivity. They can also be complemented by several system identification approaches which provide additional information. To utilize these approaches, special requirements, e. g. adequate reactions to variant process excitations during the regular process have to be fulfilled. The paper deals with the identification of velocity loop parameters of numerical controlled (NC) axes on a state of the art machine tool and gives an insight on how to correspond to the given requirements. Mainly, this is done by implementing extending modules, of which the model error estimation is pointed out in particular. Experiments with data for a turning operation show the practicability.

Tuning of Magnetic Properties and GMI Effect of Co-Based Amorphous Microwires by Annealing

We studied the effect of annealing on the giant magnetoimpedance (GMI) effect, magnetic domain wall dynamics, and magnetic properties of amorphous iron (Fe) and cobalt (Co)-based microwires prepared by the Taylor–Ulitovsky technique. We observed that the properties can be tailored by controlling the magnetoelastic anisotropy of CoFeBSiC microwires during wire formation and also controlling the magnetic anisotropy by further heat treatment. A high GMI effect has been observed in the as-prepared Co-based microwires. High domain wall velocity and rectangular hysteresis loops have been observed in additionally heat-treated microwires. We observed increasing of the wall velocity under stress in some annealed samples. We demonstrated that, for certain annealing conditions, we can observe coexistence of the GMI effect and magnetic domain wall propagation in the same sample.

Tailoring of magnetic properties and GMI effect of Co-rich amorphous microwires by heat treatment

We studied effect of annealing on Giant magnetoimpedance (GMI) effect and magnetic properties of amorphous Fe and Co-rich microwires. High GMI effect has been observed in as-prepared Co-rich microwires. We observed that changing the annealing conditions we can obtain a great variety of properties in Co-rich microwire. High domain wall (DW) velocity and rectangular hysteresis loops we observed in heat treated Co-rich microwires. We observed increasing of the DW velocity under stress and coexistence of the GMI effect and fast DW propagation in the Co-rich microwires annealed at certain conditions. Fe-rich microwires with similar bulk hysteresis loop do not present considerable GMI effect. We assume that the outer domain shall of the annealed Co-rich microwire exhibiting both fast DW propagation and GMI effect has high circumferential magnetic permeability. Observed fast DW propagation in both kind of microwires is related to the fast magnetization switching within the single domain axially magnetized inner core, i.e. related to the remagnetization process of the inner part of the microwire.

Active Disturbance Rejection Controller Design for Electric Vehicle Traction System

In some low velocity electric vehicle system, Brushless DC motor is used for the main traction motor. However, the low-velocity stability should be guaranteed, especially with the suddenly-changing load, the velocity response should be more quick and the overshoot should be small, all of above can make the vehicle more comfortable. The traction system is controlled by a current loop and a velocity loop, so a new method is proposed, that PI control strategy is in the current loop and the active disturbance rejection controller is in the velocity loop to restrain the bad effect results from suddenly-changing load. This active disturbance rejection controller is composed of a tracking differentiator, an extended state observer, a nonlinear state error feedback controller, and etc. The parameters of the controller are optimally designed, and the simulation results show that this control strategy can effectively restrain the suddenly-changing load and improve the vehicle’s low velocity performance.

Effect of Annealing on Magnetic Properties and Giant Magnetoimpedance Effect of Amorphous Microwires

We report on the magnetic properties and giant magnetoimpedance (GMI) effect of amorphous glass-coated Co-rich microwires in as-prepared and annealed states. The magnetic field and frequency dependences of GMI, magnetic hysteresis loops, and domain wall (DW) dynamics of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">69.2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4.1</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11.8</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13.8</sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.1</sub> microwires produced by the Taylor-Ulitovski technique were investigated systematically. We have shown that these properties can be tailored either by controlling magnetoelastic anisotropy of the as-prepared microwires or by controlling their magnetic anisotropy via proper annealing. While the GMI effect has been achieved in an as-prepared microwire, high DW velocity and rectangular hysteresis loops have been observed in its annealed counterpart.

Application in prestiction friction compensation for angular velocity loop of inertially stabilized platforms

To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms (ISPs) with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experimental results indicate that compared with those of the conventional proportion–integration–differentiation (PID) control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2s to almost 0s, the position error decreased to 86.7% and the peak-to-peak value of position error decreased to 80% after the novel compensation controller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.

Research on High-Quality Dual-Redundancy Aircraft Rudder Servo System Simulation

In order to improve the reliability of aircraft, a high quality dual-redundancy rudder servo system is designed. Dual-redundancy BLDCM and redundancy strategy are applied. A dual-redundancy BLDCM mathematical model is established. Using matlab/simulink, the simulation of motor is given. The control strategy based on position loop, velocity loop and current balance loop is designed. The simulation of dual-redundancy rudder servo system shows that the system has a good dynamic response and high steady-state accuracy. The performance of the servo system is excellent.

Comparative Study of Motion Control Card Based on NI PXIe and cRIO Platform for Three-Axis Turntable

In this paper, the Brushless DC motor (BLDCM) and reducer are used to drive each axis of three-axis turntable. In real-time servo control systems, the position loop parameters are designated by the software CME2, and the frequency band of the middle frame with the specified amplitude can be measured. Then, the drive model is alternated to the velocity loop, and two frequency bands will be got by using the controller of NI PXI-7344 and NI 9514 separately. The reason why the three frequency bands are different can be given by analyzing the data of the three sweep tests. In addition, both advantages and disadvantages of two NI motion controllers are illustrated. Finally, the paper points out the new motion control solutions to improve the performance of the servo system by autonomous intelligent control algorithm.

Research on High-Quality Dual-Redundancy Aircraft Rudder Servo System Simulation

In order to improve the reliability of aircraft, a high quality dual-redundancy rudder servo system is designed. Dual-redundancy BLDCM and redundancy strategy are applied. A dual-redundancy BLDCM mathematical model is established. Using matlab/simulink, the simulation of motor is given. The control strategy based on position loop, velocity loop and current balance loop is designed. The simulation of dual-redundancy rudder servo system shows that the system has a good dynamic response and high steady-state accuracy. The performance of the servo system is excellent.

送り駆動系におけるエネルギ収支の評価

Since the energy consumption of production facilities occupies the great portion of the energy consumption in the manufacturing, the energy saving of the production facilities is important. Thus, this study focuses onto the energy consumption of the feed drive system and aims at reduction of its energy consumption. Feed drive systems are widely used for various industrial facilities such as NC machine tools, hence the energy consumption of feed drive systems are directory related with the energy consumption in the manufacturing. In order to achieve the purpose, the energy consumption of the feed drive system is clarified by using the experimental apparatus single axis feed drive system and the energy usages are also estimated by simple mathematical models. The measurement tests are carried out with both of ball-screw and linear motor drives, under several friction characteristics, and several driven mass to investigate the influence of the factors to the energy consumption of the feed drive system. As the results, it is clarified that the energy consumption is influenced by the drive system, friction characteristics of linear guide and velocity loop gain.

Design and Implementation of FFPIV Scheme for Closed Loop Motion Controller

To satisfy the requirements of motion control for industrial machine, a multi-axis motion controller based on DSP is developed in this paper. The motion controller consists of DSP which plays a main role in this design; DPRAM to make sure the rapid and reliable communication with host; FPGA to handle the task of address decoder and receiving feed-back encoder signal; and several peripheral logic circuits. In the part of hardware design, overall structure of motion control system is presented. Then, the Feed-Forward Proportional-Integral-Velocity (FFPIV) scheme which introduces KV in term of velocity loop to achieve the accurate, smooth and real-time response is proposed in the software developing part. The experiment data are carried out to indicate that this motion controller has advantages of superior performance and highly machining precision.

Analysis of Vibration Damping in Machine Tools

The dynamic behavior of a machine tool structure directly influences key metal cutting performance like being able to quickly remove hard workpiece material during roughing or minimize unwanted oscillations during high speed movements in finishing. While structure conception is still funded on designer experience and inventiveness, Finite Element models are very effective in analyzing the conceived structure, allowing its optimization, in term of stiffness increase and/or mass reduction.While today FE models provide a satisfying description of structure distributed stiffness and inertia, machine damping is usually not represented or is approximated as a uniform viscous damping, with no precise reference to the actual dissipation phenomena occurring in the structure. The corresponding incertitude in the estimation of the overall dynamic behavior often strongly limits the possibility of delivering accurate absolute estimations of machine performance. In order to overcome this limitation, this work aims at adding key energy dissipation mechanisms into numerical structural models: the velocity loop of the axis position controller, the frictional forces acting on the axis kinematic chain and guide ways and a distributed modal damping. Experimental tests have been performed on a machine tool axis equipped with tunable roller plus plain friction guide ways. The proposed model shows how different components and phenomena contribute into increasing machine performance, in term of material removal capacity. Given that the resulting models are essentially non-linear, appropriate methodologies are also suggested to integrate the proposed analysis into the usual machine development design cycle.

A Predictive Velocity Observer in Wire Bonder’s Control System

Wire bonder is a typical high speed machine. The motion speed of XY-stage is the key factor of bonding efficiency. However, phase lag elements in the servo system limit the bandwidth and slow down the system’s response. A predictive velocity observer is proposed to compensate for those phase lags. Then, the velocity loop controller can be designed as for a servo system which does not have those phase lags. Loop gains are enlarged and bandwidth is enlarged correspondingly. Then, the motion speed is improved and settling time is decreased. Experiment results verify that the predictive velocity observer provided a significant phase lead and the performance of wire bonder is improved.