Position Step Response Research Articles

Systems identification of servomechanism parameters using jellyfish, particle swarm and constraint optimization

In this paper, DC servomechanism parameters were identified offline using Jellyfish, particle swarm and constraint optimization techniques in a MATLAB simulation environment with experimental data. Specifically, the unknown parameters of the servomechanism were identified using a two-step approach. Initially, the first-order transfer function of the servomechanism which is characterized by a DC gain and time constant was determined analytically using the experimental open-loop speed step response of the servo motor. Next, by iterative minimization of a fitness score derived from the root mean squared error between the experimental and simulated position response of the servomechanism of an equivalent state-space model structure, the servomechanism parameters were identified. The simulated angular position step response of the servomechanism with the particle swarm, Jellyfish and constraint optimization algorithm, showed excellent agreement with the experimental data in descending order and was consistent with the fitness score of 1.9035, 0.0083, and 0.00706 respectively.

Research on profiling tracking control optimization of orchard sprayer based on the phenotypic characteristics of tree crown

The performance of the profiling tracking control system was one of the important factors affecting the spray deposition and drift characteristics of the profiling variable spray. This paper proposed a dynamic threshold function to improve the CMAC-PID control algorithm to improve the real-time response speed and robustness of profiling tracking control system. The optimal parameters of dynamic threshold function was determined through a response surface experiment and optimal calculation. The continuous profiling tracking experiment results for outdoor tree canopy within 0–2.5 s showed that, compared with the CMAC-PID control algorithm, when the improved CMAC-PID control algorithm adopted by the profiling control system, the rise time was respectively shortened by 71.5%, 66.1% and 67.3%, the adjustment time was respectively shortened by 67.6%, 57.6% and 50.0%, and the overshoot was respectively 0.658%, 0.552% and 3.46% for the profiling angle position step response of the profiling mechanism module A_up, B and A_down. The continuous profiling tracking experiment results for outdoor tree canopy within 2.5–11.5 s showed that, compared with the CMAC-PID control algorithm, when the improved CMAC-PID control algorithm was adopted by the profiling control system, the profiling tracking response curves and the profiling target angle curves were closer to coincidence, and the average error of profiling tracking has been reduced by 35.9%, 57.4% and 38.1% respectively for the profiling mechanism module A_up, B and A_down. It showed that the profiling control system using the improved CMAC-PID algorithm had better response speed and profiling tracking performance.

Dynamic Electromechanical Model and Position Controller Design of a New High-Precision Self-Bearing Linear Actuator

Direct drive tubular linear actuators (TLAs) may be used in various applications that require fast movements and high-precision positioning, e.g., pick-and-place robots. This article presents the analysis, dynamic electromechanical model derivation, controller design, and system operation of a TLA with integrated magnetic bearings (MBs). Furthermore, the actuator operation is verified with extensive measurements on the prototype, which include axial position step response, standard deviation of the steady-state positions and mover tilting control. Compared with any conventional TLA, which may perform only linear motion, the mover tilting control is possible due to integrated MBs. This gives the new actuator a great advantage in high-precision positioning systems, since any thermal expansions of the parallel kinematics may be compensated.

Development and Precise Positioning Control of a Novel Linear Motor

A Novel Two-Phase Brushless Tubular Linear Motor And Its Precise Positioning Control System Are Presented In This Paper. The Magnetic Field Distribution In The Air Gap Of The Linear Motor Is Trapezoidal With Optimization By Halbach Magnet Array, And An Ironless Structure Is Adopted To Eliminate Force Ripples. A Simple And Practical Controller Called Active Disturbance Rejection Controller Is Used To Implement Positioning Control Of The Linear Motor Prototype, Which Is Affected By Parameter Uncertainties And Friction. Simulation And Experimental Results Show That The Position Step Response Is Smooth And Micrometer Positioning Accuracy Is Achieved Without Significant Overshoot Or Oscillation. It Can Be Concluded That The Proposed Linear Motor Is Suitable For Smooth And Precise Linear Motion Applications.

Adaptive PI control strategy for flat permanent magnet linear synchronous motor vibration suppression

Due to low damping ratio, flat permanent magnet linear synchronous motor’s vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of K p and T i on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor’s motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature-axis current under typical load. Adaptive PI control strategy can effectively suppress the flat permanent magnet linear synchronous motor’s vibration without affecting the motor’s performance.

Forced dynamics control of PMSM drives with torsion oscillations

PurposeThe purpose of this paper is to discuss the design and verification of a new control algorithm for the drive with permanent magnet synchronous motor (PMSM) and flexible coupling based on “Forced dynamics control”. Control laws are derived and tested for the rotor and load angle control and achieve non‐oscillatory position step response with a specified settling time.Design/methodology/approach“Forced dynamics control” is a new control technique based on feedback linearization which forces rotor or load position to follow demanded position with prescribed closed‐loop dynamics. The proposed control structure is developed in two steps: first, the feedback linearisation is applied to the rotor speed and then similar technique is used for position control loop.FindingsThe proposed controller is of the cascade structure, comprising an inner speed control loop, respecting vector control principles and outer position control loop designed to control the rotor or load angle, respectively. Estimates of load torques acting on the motor and load side as inputs of control algorithms are produced in observers and used to compensate disturbances offering a certain degree of robustness. Preliminary experiments confirm that proposed system follows the ideal closed‐loop dynamics with moderate accuracy.Research limitations/implicationsThe focus is on experimental verification of the position control of flexible PMSM drive with two position sensors and moderate precision, where the oscillations due to hardware setup, achieved sampling frequency and corresponding observers adjustment are limited up to 50 rad s−1.Practical implicationsThe designed control structure can substantially improve control performance of industrial plants subjects to torsion oscillations.Originality/valueExperimental results of a novel control structure for the PMSM drives with torsion oscillations are sufficiently promising and confirmed that the rotor and load angle responses follow the prescribed ones fairly closely.

空気圧シリンダの鉛直方向位置および力の同時制御

Recently, pneumatic cylinders and DC servo-motors have be c ome the most favorite actuators utilized as Z axis (vertical axis) actuators of industrial robots. When a robot performs such works as assembly, polishing and deburring, position, together with force of an end-effector or a tool connected to the Z axis must be controlled. Although a linear motion mechanism driven by a DC servo-motor and a ball-screw can provide an excellent positioning accuracy, it is not satisfactory in allowing wide change of force. On the other hand, a pneumatic cylinder has inherently good controllability as to force because of compressibility of air, but it is inadequate for positioning. In order to achieve accurate p ositioning and force c ontrol, together with simultaneous position and force control of a cylinder for the Z axis actuator, a pneumatic servo-system composed of a cylinder installed vertically, double electro-pneumatic proportional control valves, and sensor feedback equipment has been developed. Optimal control methods with and without an integral compensator and micro-computer con trol have been applied to the system. Optimal feedback coefficients derived from Riccati's equation expressed in a digital data system are chosen so as to minimize settling time without overshoot in the step response of position and force of the piston, respectively. Two types of simultaneous position and force control methods are proposed. Experiments show that the integral type optimal control can provide satisfactory results in positioning as well as in force control. Furthermore, one of the simultaneous position and force control methods?a method which gradually diminishes feedback gains in the final stage of the control-gives excellent results.