Linear Position Control Research Articles

Discrete time stability of augmented Lagrangian formalism based underactuated inverse dynamics control method

Stability problems of robotic systems arise sometimes suddenly, seemingly for no reason. The digital time sampling is often the main cause of these instabilities. Discrete models, which are capable of the prediction of stability, are available for low-degree-of-freedom template models of linear position and force control. However, for the inverse dynamics control of underactuated systems, the literature has a lack of generally applicable results related to the effect of time discretization. Several control approaches are available in the literature out of which a widely used one, the augmented Lagrangian formalism and its stability properties are analysed in this work. Theoretical stability properties are obtained for a generally usable, linear, underactuated, two-degree-of-freedom constrained template model. The actuator dynamics, the finite difference approximation of the feedback velocity and the filtering of the feedback data are considered in the model. These phenomena strongly affects the stability properties. The theoretically obtained stability maps are experimentally validated on an underactuated crane-like indoor robot. The position and orientation accuracy of the robot were assessed: the absolute position error was below 30 mm and the orientation error was below 3°.

Multivariable Linear Position Control Based on Active Disturbance Rejection for Two Linear Slides Coupled to a Mass

Active Disturbance Rejection Control (ADRC) is a promising approach that has emerged to deal with uncertainties, which has received many practical applications in motion controls. This paper presents a multivariable controller for active disturbance rejection (ADR) based on an extended state linear observer for tracking the linear position trajectory of a mass moved by two linear slides, each one driven by a DC motor. The linear extended state observer is used to estimate the endogenous and exogenous disturbances of the system, which are assumed to be unknown, but bounded. Therefore, the feedback system prevents each actuator from operating at different forward speeds, and thus a synchronization between the two actuators is achieved by moving the common mass smoothly. The simulation and the experimental results show the effectiveness and robustness of the controller proposal when moving the mass with both actuators.

Analytical substantiation of the system of automatic control of mode and technological parame-ters of the separating system of the machine for onion harvesting

Analytical studies have been carried out on the development and justification of an automatic control system for the regime and technological parameters of the separating system of an onion harvesting machine, a block diagram and an algorithm for a linear position control system, as well as a design scheme for the formation of a control algorithm, have been developed. A mathematical model of the control object for regulating the depth of the mode parameters of the separating system, the condition for ideal tracking of the trajectory of the point of movement of the moving parts of the drive mechanisms of the links of the master device and the rods of the actuating actuators of the automatic system of the separating system are determined.

An Accelerated Error Convergence Design Criterion and Implementation of Lebesgue-p Norm ILC Control Topology for Linear Position Control Systems

Traditional and typical iterative learning control algorithm shows that the convergence rate of error is very low for a class of regular linear systems. A fast iterative learning control algorithm is designed to deal with this problem in this paper. The algorithm is based on the traditional P-type iterative learning control law, which increases the composition of adjacent two overlapping quantities, the tracking error of previous cycle difference signals, and the current error difference. Using convolution to promote Young inequalities proved strictly that, in terms of Lebesgue-p norm, when the number of iterations tends to infinity, the tracking error converges to zero in the system and presents the convergence condition of the algorithm. Compared with the traditional P-type iterative learning control algorithm, the proposed algorithm improves convergence speed and evades the defect using the norm metric’s tracking error. Finally, the validation of the effectiveness of the proposed algorithm is further proved by simulation results.

Adaptive position control of a cart moved by a DC motor using integral controller tuned by Jaya optimization with Balloon effect

This study suggests an adaptive linear position control of a car moved by an armature-controlled DC motor. In this study, Jaya optimization algorithm supported by Balloon effect (BE) is used to tune the parameters of the controller of the car position. BE is introduced to improve response of the classical Jaya algorithm in face of the external disturbance and system parameters changes. In the suggested technique, an objective function (OF) of the modified Jaya depends on the updated values of the controller gains and identified value of the motor open loop transfer function. System with the suggested controller has been evaluated in case of step load disturbance and motor parameters changes. Simulation and experimental results supported that suggested adaptive controller using modified Jaya improved the total system performance at moments of load disturbance and uncertainties of system parameters.

Performance enhancement of hybrid hydraulic excavator using multiple hydro-pneumatic accumulators

In this article, the heavy earth moving machinery like hydraulic excavator used in the construction and mining industries has been taken into consideration. Most of the heavy earth moving machineries used in these industries are mobile with engine as the main source of power. The work deals with two different hydraulic circuits: first the proposed one and second the conventional one, and both are studied at laboratory scale, which resembles the circuit of the hydraulic excavator. In the hydraulic circuit, out of the three hydraulic linear actuators, two are connected with hydro-pneumatic accumulators and one hydro-motor is also taken into consideration, which resembles the boom, arm, bucket and swing motor, respectively. The idea behind the proposed circuit is to store substantial potential energy during downward movement of the two linear actuators in the accumulators, which resembles the boom and arm cylinder of the excavator. The stored energy is used for upward motion of the two actuators without utilizing any energy from the main pump. For the devised strategy, MATLAB/Simulink environment has been utilized for developing the simulation model and the same has been validated with the experimental data with reasonable accuracy. The effect of accumulator volume and pre-charge pressure has been studied for optimization of the accumulator size on the validated simulation model. This concept helps in saving 14.06% energy than its conventional counterpart which does not have the energy storage elements. The linear position control of the boom and the arm actuator in the proposed circuit have been accomplished using proportional–integral–derivative control and pressure-compensated proportional flow control valve and have been achieved with reasonably accuracy.

Position control of an electro-hydrostatic asymmetric actuator operating in all quadrants

Pump-controlled actuators generally use single-rod cylinders in order to provide high output forces and reduce the installation space. According to the working principle of such systems, there are four possible circuit configurations, corresponding to four operational quadrants. This paper presents the design and experimental validation of a robust, fixed-gain, linear position controller for a newly developed single-rod pump-controlled actuator, i.e., electro-hydrostatic actuator (EHA) that operates in all quadrants. The actuator operates under different loading, being subjected to an alternating resistive-assistive load force. The controller has been built upon the quantitative feedback theory (QFT), and is designed to satisfy tracking, stability and disturbance rejection specifications, considering a wide range of parametric uncertainties. The ability of the proposed controller to maintain the actuator position within acceptable response envelopes, has been examined with the aid of an instrumented John Deere JD-48 backhoe. The experimental results show that oscillations in position responses are not observed during quadrant switch up to a load mass of 367 kg.

BLDC technology and its application in weapon system launching platform

In this paper Brushless DC (BLDC) Technology and its Application in Articulation of Weapon System Launching Platform using Electromechanical Servo Drive is presented. The angular position or linear position of a system can be controlled by rotation or articulation in elevation and azimuth plane. In linear position control angular rotation of the BLDC motor is converted into linear motion by using Electromechanical Actuator to articulate in desired direction. For articulation of a weapon system launching platform, Electromechanical Servo Drives are used. Due to inherent properties of BLDC Technology BLDC Motors and Drives are profoundly used in military and strategic weapon system applications. In this paper, BLDC Motor and Electromechanical Servo Drive System, operating principle, modeling, characteristics and its application in various weapon system programs are discussed.Keywords: BLDC Motor, Electromechanical Servo Drive, Positioning, Articulation, Weapon system launching platform

Analysis of Linear Feedback Position Control in Presence of Presliding Friction

Analysis of Linear Feedback Position Control in Presence of Presliding Friction

Practical Implementation of Novel Robust Position Control Scheme for Synchronous Reluctance Motor

A variable structure robust position controller is presented for a three-phase synchronous reluctance motor. Linear control and variable structure control and pulse-width modulation generation are combined. These provide robust, fast, and accurate position control without the penalty of high chattering. Schemes, including conventional sliding-mode control and the proposed scheme, are tested under parameter variations, and sudden perturbations are applied to the system at a specific time, then compared. This scheme uses both advantages of traditional variable structure control methods and linear methods. The disadvantages of each method, such as chattering and parameter sensitivity, are minimized. Results demonstrate that the proposed technique preserves the classical linear position control merits, while both the steady-state and transient behavior are significantly improved in terms of robustness, accuracy, and low ripple. The results also prove that the position reference command is perfectly tracked in spite of motor parameter uncertainties and load torque disturbance in control of the system that uses the new schemes.

Development of a Parallel Actuation Approach for MR-Compatible Robotics

In recent years, the use of robotics to augment MRI diagnostic and interventional procedures has increased significantly. However, the demanding MRI environment precludes the use of most common actuation approaches. Alternative actuation concepts have been proposed but these solutions do not lend themselves to linear control structures. We present a new actuation method, using the motion of parallel ultrasonic motors combined through a differential mechanism, to address these limitations. Specifically, the approach eliminates the nonlinear velocity dead band and velocity reversal time delay characteristic of MR-compatible ultrasonic actuators. A prototype of this device is constructed and evaluated. Results demonstrate the viability of the proposed approach for linear position control and telerobotic applications.

Linear Electric Machines, Drives, and MAGLEVs Handbook (Boldea, I.; 2013) [Book News

The author of this book presents a new handbook devoted to a wide family of linear electric machines (LEMs), which realize the conversion of electrical energy to linear motion mechanical energy, or vice versa, based on electromagnetic forces. The fast development of industrial LEMs has been observed since 1960, thanks to the development of power electronic converters used for linear position, speed, and force control. The book is based mainly on more than 40 years of the author?s experiences and recent contributions to the topic worldwide.

SUBOPTIMAL NONLINEAR CONTROL OF PACKAGING MACHINERY DRIVE

This paper deals with the procedure of synthesis of a nonlinear position controller for the «feeder» of packaging mechanism. The mathematical model of «feeder» drive with regard to the restriction on the control output of external PLC. Linearization of nonlinear characteristic by the «secants» method is implemented and selected functional quality that defines the minimal time of transients is selected. Quality functional in the form of a quadratic functional with a variable weighting factor is presented. To find the suboptimal control law, the method of dynamic programming method using the concept of an invariant «immersion» is used. In this case, the original nonlinear problem is decomposed into several linear optimal control problems. The problem of synthesis of the position controller «in the small» and «in the large» is solved; the analytical expressions for the control actions are obtained. As a result of the synthesis of the nonlinear control law, containing linear and cubic components of the state variables is obtained. The dynamic characteristics of the «feeder» drive with the standard linear position control, as well as synthetic nonlinear control method of digital simulation are presented.

Design and validation of a novel Cartesian biomechanical testing system with coordinated 6DOF real-time load control: application to the lumbar spine (L1–S, L4–L5)

Robotic methods applied to in-vitro biomechanical testing potentially offer more comprehensive evaluations however, standard position control algorithms make real-time load control problematic. This paper describes and evaluates a novel custom developed Cartesian force controlled biomechanical testing system with coordinated 6 degree of freedom (DOF) real-time load control.A custom developed 6-DOF serial manipulator with cascaded force over position control algorithms was designed, assembled, and programmed. Dial gauge tests assessed accuracy of custom linear axes. Standard test input and tuning procedures refined control performance. Two single motion segment units (L4–L5) and lumbar (L1–S) spine segments were tested under continuous pure moment application in flexion–extension, left–right lateral bending and axial rotation to 8Nm under full 6-DOF load control. Mean load control tracking errors between commanded and experimental loads were computed. Global spinal ranges of motion were compared to previously published values for standard non-robotic protocols.Individual linear and rotational axis position control accuracies were equal to or less than 6.35μm and 0.0167° respectively. Pilot pure bending tests demonstrated stable load control performance, as well as load rates, rotational velocities, and ranges of motion comparable to those for standard non-robotic in-vitro tests. Tracking errors for zero commanded forces and all moment controlled axes were less than 0.81±0.68N and 0.18±0.19Nm over all tests, respectively.The Cartesian based system simplified control application and demonstrated robust position and load control that was not limited to single axis or zero commanded loads. In addition to emulating standard biomechanical tests, the novel Cartesian force controlled testing system developed is a promising tool for biomechanical assessments with coordinated dynamic load application and coupled motion response in 6DOF.

Model-based position control of shape memory alloy actuators

Shape-memory-alloys (SMAs) are easy to integrate into mechanical structures and capable of handling high specific workloads. Therefore, SMAs possess an outstanding potential to serve as positioning devices in various applications. We present here the multi-domain modelling of an electrically heated SMA wire which includes changes of electrical parameters in conjunction to mechanical parameters. Due to the correlation between electrical resistance and mechanical stroke, it was possible to implement a resistance-based position control without the necessity of an external positioning sensor. In order to design a linear position controller by common rules, the highly complex and non-linear model was simplified. Controller development yielded a PID algorithm that was implemented on a rapid prototyping system as part of an SMA wire test bench. The models accuracy was verified by various measurements with different wires and multiple loads. Based on that, it was possible to design an actuator which utilises a flexible socket instead of fixed mountings.

Global PID position control of PM stepper motors and PM synchronous motors

This article is concerned with position control of permanent magnet (PM) stepper motors and PM synchronous motors. We present, for the first time, some stability proofs which explain, under mild assumptions, why the most common control strategy used in commercial drives works well in practice. We stress that this successful control strategy has been used until now only on the basis of linear approximations. As in most commercial drives, we consider the design of a linear PID position controller intended for the mechanical subsystem and some inner electric current loops driven by linear proportional controllers which are introduced to cope with the electrical subsystem.

Improvement of a testing apparatus for dynamometry: procedures for penetrometry and influence of strain rate to quantify the tensile strength of soil aggregates

Soil penetration resistance (PR) and the tensile strength of aggregates (TS) are commonly used to characterize the physical and structural conditions of agricultural soils. This study aimed to assess the functionality of a dynamometry apparatus by linear speed and position control automation of its mobile base to measure PR and TS. The proposed equipment was used for PR measurement in undisturbed samples of a clayey "Nitossolo Vermelho eutroférrico" (Kandiudalfic Eutrudox) under rubber trees sampled in two positions (within and between rows). These samples were also used to measure the volumetric soil water content and bulk density, and determine the soil resistance to penetration curve (SRPC). The TS was measured in a sandy loam "Latossolo Vermelho distrófico" (LVd) - Typic Haplustox - and in a very clayey "Nitossolo Vermelho distroférrico" (NVdf) - Typic Paleudalf - under different uses: LVd under "annual crops" and "native forest", NVdf under "annual crops" and "eucalyptus plantation" (> 30 years old). To measure TS, different strain rates were applied using two dynamometry testing devices: a reference machine (0.03 mm s-1), which has been widely used in other studies, and the proposed equipment (1.55 mm s-1). The determination coefficient values of the SRPC were high (R² > 0.9), regardless of the sampling position. Mean TS values in LVd and NVdf obtained with the proposed equipment did not differ (p > 0.05) from those of the reference testing apparatus, regardless of land use and soil type. Results indicate that PR and TS can be measured faster and accurately by the proposed procedure.

Implementation of Feedback Error Learning for Position Control System of Linear Slider

This paper considers implementation of feedback error learning (FEL) for linear slider position control. The effect of modelling error of the slider is compensated by FEL. In algorithm of FEL, parameters of feedforward controller are updated so that output signals of a feedback controller can become small. It leads to improvement of tracking performance. On the other hand, when conventional FEL algorithm is implemented for control of a linear slider, parameters of the feedforward controller tend to converge slowly. In industrial scenes, it is desirable to shorten learning time in order to reduce cost of setting up manufacturing devices. Furthermore, when the learning time is long, guide rails of the slider become worn. It is shown that convergence speed is improved by tuning free parameters of the feedforward controller. Due to further improvement of the convergence, by using prefilter and free parameters of feedforward controller, some parameters of an inverse system are obtained a priori and utilized for learning. Command with mixed frequency is selected in order to identify accurate inverse system of plant. Simulation results are presented to show the effectiveness of proposed method.

Nanoprecision MEMS Capacitive Sensor for Linear and Rotational Positioning

This paper presents a microelectromechanical systems (MEMS) capacitive position sensor for nanopositioning applications in Probe storage systems. The objective of the sensor system design is to develop a high-precision <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position sensor with a minimum sensor area and a large range of movements at high speed. To achieve this, first, a simple sensor noise model scalable with a sensor area was developed, in which all the parasitic capacitances are taken into account. Furthermore, a signal-processing solution was developed to compensate for the nonlinearities caused by rotational disturbances and, at the same time, to generate a rotational position signal for active rotation-control purposes. A MEMS capacitive sensor prototype was constructed with the design of a 13-mum pitch, a 300-mum peak-to-peak linear stroke, and a 3.46-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sensor area at a 3-mum gap. The measured sensor noise was 0.2 nm 1sigma, which corresponds to 12 mudeg 1sigma for the fabricated prototype sensor, at 25-kHz bandwidth. Furthermore, the signal linearity was significantly enhanced by the proposed sensor signal processing, with a measured sensor signal nonlinearity of 0.78% for an 80-mum peak-to-peak stroke at 200 Hz. Finally, the capacitive sensor-based dynamic closed-loop <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position control of an electromagnetic scanner was successfully demonstrated.

Development and control of a prototype permanent-magnet DC linear motor

Most advanced manufacturing processes require precise linear-position control for material transfer, packaging and assembly. To achieve precise linear motion, most of these high-performance manufacturing machines use rotary motors and rotary-to-linear couplers. Although this method is widely used, it has the disadvantages of low accuracy, complex mechanical adjustments, high cost and low reliability. A prototype permanent-magnet DC linear motor that is used as a direct-linear drive for position-control applications is described. Experimental investigation of the motion system indicates that the constructed prototype has response with good accuracy.