Position Servo Control Research Articles

Position servo controller design and implementation using low cost eddy current sensor for single axis active magnetic bearing

Eddy-current sensors are the most commonly used position sensors in a magnetic bearing application. Most commercial eddy current sensor outputs analog voltage of 0–2 V or 0–5 V in their measurement range. Such eddy current sensors are quite expensive and are in the price range of $2500 (USD). This paper presents a design of a $20 (USD) low-cost eddy current sensor capable of resolving displacements of 7 micron which is suitable for high-speed position control in active magnetic bearings. A novel method of directly converting the time period of the square wave signal from the eddy current sensor output for digital servo position feedback is employed in this design. This paper presents a scheme to implement digital position servo control algorithm on Texas Instruments C2000 real-time microcontroller to control the position of magnetically levitated object by controlling the magnetic actuator’s coil current. The magnetic actuators are electromagnetic coils that generate the magnetic force in the bearing.

Tip-position/velocity Tracking Control of Manipulator for Hull Derusting and Spray Painting based on Active Disturbance Rejection Control

During sandblasting and spray painting for hull, the tracking performance of the end-effector of manipulator to the outer surface of the hull in uniform velocity is seriously affected by uncertainty of the electrohydraulic actuator and deflection of the manipulator. To effectively improve the tracking performance of the tip-position/velocity, a novel tracking control strategy is proposed, which is based on active disturbance rejection control (ADRC) with extended state observer (ESO) and setting position feedforward control with deflection compensation. First, to reduce tracking error caused by the deflection, the reference positions of two cylinders driving telescopic and luffing motion are calculated with consideration of the deflection influence according to manipulator geometry. And then, ADRC technique is adopted to design the position servo controller of the luffing/telescopic cylinder with the help of the estimate for the uncertainty of the electro-hydraulic system by the ESO. The stability of the whole closed-loop system and the convergence of tracking error are guaranteed theoretically, simultaneously, simulation carried out in Matlab/Simulink environment with physical parameters of a real system demonstrates the effectiveness and superiority of the proposed control strategy compared with existing control schemes. Furthermore, the experimental result is given to show the feasibility and availability of the control method.

Friction-resilient position control for machine tools—Adaptive and sliding-mode methods compared

Robust trajectory tracking and increasing demand for high-accuracy tool positioning have motivated research in advanced control design for machine tools. State-of-the-art industry solutions employ cascades of Proportional (P) and Proportional–Integral (PI) controllers for closed-loop servo control of position and velocity of the machine axes. Although these schemes provide the required positioning accuracy in nominal conditions, performance deteriorates with increased friction and wear of the machine. With conventional control, re-tuning is necessary during the lifetime if specified accuracy shall be maintained. This paper investigates whether nonlinear and adaptive controllers can cope with typical levels of friction increase without loss of performance. It evaluates the performance of a state-of-art industry solution with that obtainable with adaptive and sliding mode positioning controls. The main finding is that an adaptive backstepping control is resilient to unknown and increasing friction at realistic levels of wear, where the P-PI control fall short with respect to accuracy. A single-axis test rig with adjustable friction is used to assess the performance of different controllers.

The Research on Characteristics of Hydraulic Support Advancing Control System in Coal Mining Face

This paper researches the electro hydraulic control system of two-column shield hydraulic supports, takes the hydraulic support base advancing loop as the position servo control system, and studies its dynamic characteristics. It establishes the power amplifier, position sensor, hydraulic cylinder and loading mathematical model of the position servo control system, determines the model parameters of the advancing control system according to the shield hydraulic support used in the 1315 working face of GuoTun coal mine, and derives the opening loop transfer function of the valve controlled advancing cylinder. This paper also analyzes the stability of the control system of the advancing loop with the modern design method, and verifies the stability of the electro-hydraulic control system loop according to the simulation curve and the stability. By comparing with the valve core displacement and system flow curve while the system opening or closing, this paper explains the application effect of servo control system. It provides a new research idea and method for the study of the overall stability and effectively reduces the failure rate of electro-hydraulic control system of the hydraulic support. It also plays practical significance and value to improve the mining efficiency of the coal mining face.

Modeling and PWM Control of Electro-Pneumatic Actuator for Missile Applications.

The Electro-Pneumatic Actuators (EPAs) using ON/OFF type solenoid valves are very popular in aerospace applications due to their robustness, simplicity, high Torque/Weight ratio, fast speed of response, etc. This paper deals with the modeling, simulation, plant characterization, design of a Pulse Width Modulation (PWM) Controller and model validation of an EPA used in missile applications. The EPA used in this work consists of 3-way, 2-position, ON-OFF type solenoid valves. A non-linear mathematical model of the EPA has been developed and implemented in the MATLAB/SIMULINK environment to carry out the simulation studies. The plant model is characterized in the experiment using Frequency Response Analysis (FRA). A Single Sided Pulse Width Modulation (SSPWM) Controller with phase lead-lag compensators and a proportional gain has been designed for the closed loop position control of the missile fin servo. The model is validated by comparing the experimental closed loop time responses with the simulation.

Control of Pneumatic Position Servo with LuGre Model-based Friction Compensation

Control of Pneumatic Position Servo with LuGre Model-based Friction Compensation

Position feedback dynamic surface control for pneumatic actuator position servo system

ABSTRACTPneumatic servo system is widely utilized in many industries, which has huge potential to replace hydraulic and electromechanical system due to its low-cost, high power quality ratio and quick response. There have been considerable control methods proposed to complete pneumatic position servo control. However, these methods still have some inevitable problems which remain to be settled. In this paper, a position feedback dynamic surface control is applied to the pneumatic system based on our pneumatic actuator model in order to provide a new idea for pneumatic position control. Considering model uncertainties, external force disturbance and noise interference, a modified dynamic surface controller is developed to overcome their negative effects. Besides, the stability of the pneumatic system with the modified controller is proved by Lyapunov's stability theorem. Moreover, the results of simulation and pneumatic experiment also verify that the dynamic surface controller is more advantageous than the traditional PID controller in pneumatic position servo control.

Design of a climbing robot platform with protection device

In this article, a new wall-climbing robot platform with protection devices for city inspection is developed. After an overall structural introduction, the main protection devices of the robot are described in detail, including the support frame, the Ethylene Vinyl Acetate (EVA) shell, and the airbag. The support frame plays the roles of chassis and protection framework, so integrative and lightweight design is required. The EVA shell covers the support frame, and it protects the robot from overturn falling down from the wall. The airbag is designed both for sealing and protection. The mechanical model of the airbag is established based on the engineering thermodynamics theory and is used for force analysis when robot falls down on the ground. In addition, two-level distributed control system is designed to achieve the control of fan speed, straight moving, differential steering, position servo, and video transmission. To verify the feasibility of the climbing robot, many experiments are conducted, that is, experiments of movement, load capacity, adaptability to the wall surfaces, endurance, camera, sensor, and antithrow. The results show that the actual working performance of the climbing robot is favorable, thus providing a train of thought and inspiration for the antithrow design of climbing robot.

Intelligent tracking control of a PMLSM using self‐evolving probabilistic fuzzy neural network

This study presents a self-evolving probabilistic fuzzy (PF) neural network with asymmetric membership function (SPFNN-AMF) controller for the position servo control of a permanent magnet linear synchronous motor (PMLSM) servo drive system. In the beginning, the dynamic model for the PMLSM is analysed on the basis of field-oriented control. Subsequently, an SPFNN-AMF control system, which integrates the advantages of self-evolving NN, PF logic system, and AMF, is proposed to handle vagueness, randomness, and time-varying uncertainties of the PMLSM servo drive system during the control process. For the SPFNN-AMF, the proposed learning algorithm consists of the structure learning and parameter learning in which the former is used to grow and prune the fuzzy rules automatically, whereas the latter is utilised to train the network parameters dynamically. Finally, detailed experimental results of two position commands tracking at different operation conditions demonstrate the validity and robustness of the proposed SPFNN-AMF for controlling the PMLSM servo drive system.

FPGA-realization of a self-tuning PID controller for X–Y table with RBF neural network identification

Based on field programmable gate array (FPGA) technology, a realization of a servo/motion control system with the self-tuning PID controller for X–Y table is presented in this work. Firstly, to cope with the system and external load uncertainly, a Radial Basis Function Neural Network (RBF NN) is applied to identify the dynamic model of the X-axis table and Y-axis table and to provide the information to adjust the PID controller gains. Then, the design of an FPGA-based motion control IC for X–Y table using the aforementioned controller is described. The motion controller IC includes two modules. The first module, which performs two PMSM’s position servo controllers for X–Y table, is implemented by hardware in FPGA. The position servo controller adopts self-tuning PID controller with RBF NN identification. The second module, which runs the motion trajectory planning for X–Y table, is implemented by software in Nios II processor. As the result, the hardware/software co-design technology can make the motion controller of X–Y table more compact, robust, flexible, and less cost.

Design of the output sliding mode controller for MI non‐linear perturbed systems

An output sliding mode controller for a class of multi-input non-linear systems with non-linear mismatched perturbations is proposed by using the Lyapunov stability theorem to solve the regulation problems. An auxiliary dynamic equation is used to estimate unknown states and to depress non-linear perturbations in the control system. Design variables embedded in the auxiliary equation are utilised in the novel sliding surface so that asymptotic stability of controlled system can be achieved when the system is in the sliding mode. Finally, the feasibility of the proposed methodology is demonstrated in two examples, including a servo position control system.

Adaptive backstepping control for permanent magnet linear synchronous motor servo drive

This paper presents a position servo control approach for a permanent magnet linear synchronous motor. The non-linear motor dynamics is expressed in the backstepping control scheme on which a recursive designing procedure is carried out. Based on the desired motion trajectory, the magnetic thrust force is first calculated and then treated as the control objective for the next subsystems. The command voltages to stabilise the whole system are established concerning the electric properties of the magnetic windings. To overcome the impacts of system uncertainties, an adaptive neural network is exploited to estimate the uncertainty and provide necessary compensation in the control effort. Based on the Lyapunov functional analysis, the adaptive laws for online tuning the parameters of the neural networks are derived so that the precision of position servo control can be improved. Compared with the conventional current regulated control scheme, this investigation introduces a voltage-controlled pulse-width modulation with a complete theoretic base, including the mechanical and electrical dynamics. The effectiveness of the proposed approach is verified by the experimental results and a comparison study with a recent work developed in the robust fuzzy PI control scheme.

Research Progress in Electro-Hydraulic Position Servo Controller

The electro-hydraulic position servo control system is a typical complex nonlinear system. It is difficult in achieving the control which has high quality performance.To overcome the effects of non-linearity, parameter uncertainty, external disturbances and load changes, the design of controller is particularly critical. This paper summarizes the controllers which are applied widely: PID controller, fuzzy controller, neural network controller and hybrid controller. Additionally, the paper analyses their performances. At the same time, this paper also points out the prospects of the controllers.

A compound control strategy combining velocity compensation with ADRC of electro-hydraulic position servo control system

In order to enhance the anti-jamming ability of electro-hydraulic position servo control system at the same time improve the control precision of the system, a compound control strategy that combines velocity compensation with Active Disturbance Rejection Controller (ADRC) is proposed, and the working principle of the compound control strategy is given. ADRC controller is designed, and the extended state observer is used for observing internal parameters uncertainties and external disturbances, so that the disturbances of the system are suppressed effectively. Velocity compensation controller is designed and the compensation model is derived to further improve the positioning accuracy of the system and to achieve the velocity compensation without disturbance. The compound control strategy is verified by the simulation and experiment respectively, and the simulation and experimental results show that the electro-hydraulic position servo control system with ADRC controller can effectively inhibit the external disturbances, the precise positioning control is realized after introducing the velocity compensation controller, and verify that the compound control strategy is effective.

Development of 6-DOF Transportation Vibration Platform

A kind of design of 6-DOF transportation vibration platform was introduced. Based on the principle of Space Mechanism, the kinematics model of 6-DOF transportation vibration platform was described and the design of position servo-control system was presented. With a motion simulation experimental, the comparison results of Output/Input data in different directions were obtained. The results show that the vibration data are reproduced very well on the platform within the main frequency range in six directions.

Design of the Hydraulic System of Lead Plate Coiling Machine

This paper mainly introduces the process of lead electrolysis, the structure and working principle of lead plate coiling machine and Its’ parts, coiling machine components. First of all, rewind section hydraulic system adopts a return to the oil throttle speed control, it is stable and can bear a certain change load, can overcome the stage before the tension fluctuation of the impaction to the rotation speed of hydraulic motor. Secondly, speed and tension control system adopt electro-hydraulic servo valve and proportional relief valve are respectively to the drum speed and output torque control,it has high precision and accurate in speed and tension control. contact coiling section use electro hydraulic servo position control system with close loop control to improve the accuracy of position control. Finally, calculate parameters of each working section of hydraulic control system , verify the hydraulic component model and the rationality of the hydraulic circuit.

Research on PID Control of Electro-Hydraulic Position Servo Control System Based on SDO Optimization

Abstract. This article introduces the electro-hydraulic position servo control system, establishes its mathematical model and simulates with Simulink, then add PID module, use the empirical method to tune proportional, integral and differential parameters, it is found that adjustment is tedious, and performance improvement is limited. Then use the SDO tools for automatic optimization of PID control parameters, obtained a better simulation results. This tuning method is simple, easy to use, and with good results.

An FPGA-based parallel architecture for on-line parameter estimation using the RLS identification algorithm

A parallel architecture for an on-line implementation of the recursive least squares (RLS) identification algorithm on a field programmable gate array (FPGA) is presented. The main shortcoming of this algorithm for on-line applications is its computational complexity. The matrix computation to update error covariance consumes most of the time. To improve the processing speed of the RLS architecture, a multi-stage matrix multiplication (MMM) algorithm was developed. In addition, a trace technique was used to reduce the computational burden on the proposed architecture. High throughput was achieved by employing a pipelined design. The scope of the architecture was explored by estimating the parameters of a servo position control system. No vendor dependent modules were used in this design. The RLS algorithm was mapped to a Xilinx FPGA Virtex-5 device. The entire architecture operates at a maximum frequency of 339.156MHz. Compared to earlier work, the hardware utilization was substantially reduced. An application-specific integrated circuit (ASIC) design was implemented in 180nm technology with the Cadence RTL compiler.

Adaptive Wavelet Neural Network Backstepping Sliding Mode Tracking Control for PMSM Drive System

This paper presents a wavelet neural network backstepping sliding mode controller (WNNBSSM) for permanent-magnet synchronous motor (PMSM) position servo control system. Backstepping sliding mode (BSSM) is utilized to guarantee favorable tracking performance and stability of the whole system, meanwhile, wavelet neural network (WNN) is used for approximating nonlinear uncertainties. The designed controller combined the merits of the backstepping sliding mode control with robust characteristics and the WNN owning the capability of artificial neural networks for online learning and the capability of wavelet decomposition for identification. An observed error compensator is developed to compensate the estimated error of the WNN and the adaptive law is derived according to Lyapunov theorem. The effectiveness of the proposed controller is investigated in simulation under different operating conditions. The simulation results demonstrate the proposed WNNBSSM controller can provide precise tracking performance and robust characteristics despite unknown parameter uncertainties and load disturbance. Moreover, an implemental wavemaker system is established to verify the effectiveness of the proposed control algorithm.

A simple nonlinear PD controller for integrating processes

Many industrial processes are found to be integrating in nature, for which widely used Ziegler–Nichols tuned PID controllers usually fail to provide satisfactory performance due to excessive overshoot with large settling time. Although, IMC (Internal Model Control) based PID controllers are capable to reduce the overshoot, but little improvement is found in the load disturbance response. Here, we propose an auto-tuning proportional-derivative controller (APD) where a nonlinear gain updating factor α continuously adjusts the proportional and derivative gains to achieve an overall improved performance during set point change as well as load disturbance. The value of α is obtained by a simple relation based on the instantaneous values of normalized error (eN) and change of error (ΔeN) of the controlled variable. Performance of the proposed nonlinear PD controller (APD) is tested and compared with other PD and PID tuning rules for pure integrating plus delay (IPD) and first-order integrating plus delay (FOIPD) processes. Effectiveness of the proposed scheme is verified on a laboratory scale servo position control system.