Damping Control Law Research Articles

Research on Compliance Control of Electro-Hydraulic Loading Experimental System

This article discusses the challenges in preventing workpiece damage due to impacts in electro-hydraulic loading systems, especially in unknown environments. We propose an innovative compliance control strategy, synergizing a series elastic actuator with impedance control to significantly mitigate impact forces between the mechanism and test workpieces. The controller consists of two loops: an internal loop and an outer loop. The internal loop integrates a position loop utilizing a radial basis function observer within a backstepping control framework, effectively countering the nonlinear dynamics of hydraulic actuators and ensuring precise trajectory tracking. The outer loop advances traditional impedance control by adaptively modifying the damping coefficient, resulting in a straightforward and easily implementable damping control law. For the unknown environment parameters, our system employs a parameter estimation law to estimate the unknown environmental stiffness and position parameters. The effectiveness of this strategy has been verified through comparative simulation with traditional impedance control, indicating that the proposed method can not only effectively reduce contact shock in unknown environments, improve response speed, and reduce overshoot, but also improve steady-state accuracy. We provided a feasible control scheme for similar systems to ensure precise and safe operation.

Comfort-oriented Combined Damping and Stiffness Control of a Multichamber Suspension

This paper deals with the comfort-oriented control of a multichamber suspension. Multichamber suspensions are composed of a semiactive damper and a pneumatic spring with an auxiliary volume reservoir, which can be attached or detached from the main chamber by means of an electronically controllable valve. This architecture allows for both damping and stiffness regulation of the suspension, and is the only commercially available architecture to ever allow for stiffness control. Aim of the paper is the development of a combined damping and stiffness control law which is able to outperform the state-of-the-art Skyhook damping control, still ensuring easiness and implementability on a real-time platform. As a result, numerical simulations show a comfort improvement of up to 18% over class-B irregular roads with respect to the benchmark performance.

Improving the comfort of truck drivers by using controlled cab suspension shock absorbers

The research addresses the issue of creating a methodology for selecting the damping control law in nonlinear suspension systems and determining the characteristics of controlled shock absorbers in the cab suspensions. The study object is the shock-absorbing support device of the truck cab suspension system. By mathematical modeling of the car dynamics, it is proved the effectiveness of the cab suspension system with controlled shock absorbers and its operability according to the criterion of the possibility of implementing a controlled shock support device in the form of a technical device. Keywords controlled shock absorbers, cab suspension, smoothness running, driver comfort, shock support device

Tip Tracking Control of a Linear-Motor-Driven Flexible Manipulator with Controllable Damping

Abstract In this paper, a linear-motor-driven flexible robotic manipulator with controllable damping is presented. The dynamic model of the flexible manipulator with magnetorheolog-ical(MR) dampers is established through analyzing the force constraint of controllable MR damping and the rigid-flexible coupling dynamics of entire system via Lagrange method and assumed mode method. A controller for the flexible manipulator with MR dampers is developed to realize the dual targets of vibration suppression and accurate tip tracking for the flexible manipulator. The controller integrated output redefine adaptive robust control based on the system dynamics with damping control law according to motion state of the flexible system. Simulation results verifies the effectiveness of the proposed control method.

Introduction of damping, synchronizing and inertial effects using controlled power injection devices

This paper presents a theoretical study of damping, synchronizing and inertial control laws, implemented using controllable power injection devices like HVDC, FACTS or renewable-energy/storage systems which have power-electronic grid interfaces. The approach is to use a simplified dynamical model of a power system to arrive at generalized results regarding the effect of the strategies on the electro-mechanical dynamics of the system. These results are not dependent on the size, network topology and operating condition of the power system. This paper presents a differential-algebraic formulation and generalized eigenvalue analysis to facilitate a unified study of the effects of the control laws on the electro-mechanical modes. The damping, synchronizing and inertial control laws can themselves be extended to include the possibility of mutual-damping, synchronizing and inertial effects when multiple devices are present. The control laws are not only simple and intuitive, but also are found to have a predictable and generally beneficial impact on the electro-mechanical dynamics of the grid, even when detailed models are considered.

Magnetorheologically Damped Compliant Foot for Legged Robotic Application

This paper presents an innovative solution for bounce reduction between a robotic leg and the ground by means of a semi-active compliant foot. The aim of this work is to enhance the controllability and the balance of a legged robot by improving the traction between the foot tip and the ground. The compliant foot is custom-designed for quadruped walking robots and it consists of a linear spring and a magnetorheological (MR) damper. By utilizing magnetorheological technology in the damper element, the damping coefficient of the compliant foot can be altered across a wide range without any additional moving parts. The content of this paper is twofold. In the first part the design, a prototype and a model of the semi-active compliant foot are presented, and the performance of the magnetorheological damper is experimentally studied in quasi-static and dynamic cases. Based on the quasi-static measurements, the damping force can be controlled in a range from 15 N to 310 N. From the frequency response measurements, it can be shown that the controllable damping force has a bandwidth higher than 100 Hz. The second part of this paper presents an online stiffness identification algorithm and a mathematical model of the robotic leg. A critical damping control law is proposed and implemented in order to demonstrate the effectiveness of the device that makes use of smart materials. Further on, drop tests have been carried out to assess the performance of the proposed control law in terms of bounce reduction and settling time. The results demonstrate that by real-time control of the damping force 98% bounce reduction with settling time of 170 ms can be achieved.

Development and field tests of a damping controller to mitigate electromechanical oscillations on large diesel generating units

This paper presents the development and field tests of a digital damping controller designed to mitigate intra-plant electromechanical oscillations via the speed governor system of fast acting units. The controller performance is assessed on an 18-MVA diesel generating unit, at Santana Power Plant (Amapá State, Amazon Region at Northern Brazil). In order to design the damping control law, a set of parametric ARX models representing the plant dynamics at several load conditions, are previously identified from data collected on field tests. The damping controller gains are calculated by using the identified ARX models parameters as inputs to a discrete-time pole-placement design method (pole-shifting) and then embedded on a DSP based microcontroller digital system, for field tests assessment. The digital damping controller modulates the diesel engine inlet valve position according to the observed oscillation on the measured electric power, using a PWM device, which is specially developed to this application. The experimental results shown the good performance of the developed controller on damping efficiently the electromechanical oscillations observed between generating units at Santana Power Plant.

Dynamical behaviour of a controlled vibro-impact system

In this paper, we give a controlled two-degree-of-freedom (TDOF) vibro-impact system based on the damping control law, and then investigate the dynamical behaviour of this system. According to numerical simulation, we find that this control scheme can suppress chaos to periodic orbit successfully. Furthermore, the feasibility and the robustness of the controller are confirmed, separately. We also find that this scheme cannot only suppress chaos, but also generate chaos in this system.

Controlling bifurcation and chaos of a plastic impact oscillator

A two-degree-of-freedom plastic impact oscillator is considered. Based on the analysis of sticking and non-sticking impact motions of the system, we introduce a three-dimensional impact Poincaré map with dynamical variables defined at the impact instants. The plastic impacts complicate the dynamic responses of the impact oscillator considerably. Consequently, the piecewise property and singularity are found to exist in the three-dimensional map. The piecewise property is caused by the transitions of free flight and sticking motions of two masses immediately after impact, and the singularity of the map is generated via the grazing contact of two masses and the instability of their corresponding periodic motions. The nonlinear dynamics of the plastic impact oscillator is analyzed by using the Poincaré map. The simulated results show that the dynamic behavior of this system is very complex under parameter variation, varying from different types of sticking or non-sticking periodic motions to chaos. Suppressing bifurcation and chaotic-impact motions is studied by using an external driving force, delay feedback and damping control law. The effectiveness of these methods is demonstrated by the presentation of examples of suppressing bifurcations and chaos for the plastic impact oscillator.

Research on Continuous Damping Control Improving Force Isolation of a SDOF Mounting System

In this article, principle for force isolation in a single-degree-of-freedom (SDOF) mounting system is proposed depending on the mechanism of the transmitted force, and a continuous damping control law considering the time constant of the controllable damper is constituted. Excitation force in the form of single frequency, dual frequencies, and bidirectional swept frequencies are chosen in the simulation. With a suitable time constant of the controllable damper, the continuous damping control law ruled SDOF mounting system obtains nearly minimum force transmissibility compared to corresponding passive system and high dynamic performance compared to frequency domain method. The continuous damping control law is suitable for the mounting system with the controllable damper based on smart materials such as magnetorheological (MR) or electrorheological (ER) fluids.

Damping control law for a chaotic impact oscillator

We apply a feedback control technique to suppress chaotic behavior in dissipative mechanical systems by using a small-amplitude damping signal. The control signal is obtained by varying the damping coefficient according to the velocity direction. As an application of this method, we present numerical simulations of an impact oscillator and the required damping law used to achieve the control. Our numerical results show the method effectiveness even for high levels of noisy perturbation.

Enhancement of Feed Drive Dynamics of NC Machine Tools by Actively Controlled Sliding Guideway

In this paper, we propose a simple sliding guideway with a hydraulically operated brake unit, which can control sliding friction force on a feed drive system. The sliding friction force is controlled by the brake force command generated from velocity information of a table and/or a servomotor. The damping control laws of DVFB (Direct velocity feedback) and RVFB (Relative velocity feedback) are analyzed to provide the adequate damping for ballscrew drives. These damping control laws are implemented in the brake force control unit and the dynamic performance of a ballscrew drive is measured. Structural vibration of the ballscrew drive can be successfully controlled by this actively controlled sliding guideway in experiments.

Semi-active damping control of suspension systems for specified operational response mode

A practical and effective semi-active on–off damping control law using semi-active actuators is developed for vibration attenuation of a natural, multi-degree-of-freedom suspension system, when its operational response mode is specified. It does not need the accurate system parameters and semi-active actuator dynamics. It reduces the total vibratory energy of the system including the work done by external disturbances and the maximum energy dissipation direction of the semi-active actuator is tuned to the operational response mode of the structure. The effectiveness of the control law using a single semi-active linear mount is illustrated with a three-degree-of-freedom excavator cabin suspension model.

322 Enhancement of Feed Drive Dynamics of NC Machine Tools by Actively Controlled Sliding Guideway

In this paper, we propose a simple sliding guideway with a hydraulically operated brake unit, which can control sliding friction force on a feed drive system. The sliding friction force is controlled by the brake force command generated from velocity information of a table and/or a servomotor. Several damping control laws are implemented in the brake force control unit. Structural vibration of ballscrew drives can be successfully controlled by this actively controlled sliding guideway in experiments.

A singularly perturbed method for pole assignment control of a flexible manipulator

This paper focuses on using a singularly perturbed approach to derive a vibration damping control law in which a pole assignment feedback method is utilized. The composite control system is characterized by two components which can be computed separately. The one is Cartesian-based PI control which drives the end-effector of a flexible manipulator to track the desired time-based trajectory. The other is pole assignment feedback control which damps out vibrations during and at the end of trajectory tracking. An advantage of this composite control method in real implementation is that it does not require a derivative of the end-effector's position, and the derivatives of signals from the strain gauges. From the characteristics and implementation points of view, it appears to be simple to use. Laboratory experiments were conducted to evaluate the performance of the proposed control method.

SEMI-ACTIVE DAMPING CONTROL OF SUSPENSION SYSTEMS FOR SPECIFIED OPERATIONAL RESPONSE MODE

Abstract A practical and effective semi-active on–off damping control law using semi-active actuators is developed for vibration attenuation of a natural, multi-degree-of-freedom suspension system, when its operational response mode is specified. It does not need the accurate system parameters and semi-active actuator dynamics. It reduces the total vibratory energy of the system including the work done by external disturbances and the maximum energy dissipation direction of the semi-active actuator is tuned to the operational response mode of the structure. The effectiveness of the control law using a single semi-active linear mount is illustrated with a three-degree-of-freedom excavator cabin suspension model.

Damage Detection and Vibration Control in Smart Plates: Towards Multifunctional Smart Structures

This paper demonstrates the concept of sensitivity enhancing control (SEC) to aid in damage detection in smart structures through both experimental and simulation evaluation. Methods of implementing state estimate feedback using point measurements of strain along the structure are described, and an initial proof-of-concept laboratory experiment demonstrating enhancement of modal frequency shifts due to tip mass damage in a cantilevered beam is reported. Simulation results focus on applying state feedback control to finite-element models of a cantilevered structure with slot, through-surface crack, or surface crack damage. The simulation analysis ascertains the ability to enhance sensitivity of modal frequency shifts due to realistic damage cases that are difficult to evaluate experimentally. The simulation also ascertains the potential for using the same sensors and actuators for implementing both sensitivity enhancing control laws and vibration damping control laws that are insensitive to damage. In the control model with which SEC laws are designed, damage consists of simple reductions in thickness over a small area of the structure. Finite-element models to which control laws are applied are developed using commercial software (ABAQUS TM ) that more accurately models stiffness damage by releasing element connections or by using line spring elements to model fatigue cracks. Experimental results show that enhancement in sensitivity of modal frequencies to damage can be achieved using a single piezoceramic actuator and multiple piezoelectric strain sensors along the beam. Simulation results indicate that feedback control laws can be designed for either sensitivity enhancement or vibration suppression using identical hardware, providing for multifunctional smart structures. In addition, analysis demonstrates that commercial finite-element software is useful for model-based simulation of damaged controlled structures.

Linear and non-linear skyhook damping control laws for active railway suspensions

This paper presents and compares different control strategies for applying “skyhook” damping control laws in active suspension systems for railway vehicles. It first examines a number of linear approaches for filtering the absolute velocity signal in order to optimise the trade-off between the random and deterministic track input requirements, and then what can be achieved using non-linear methods based upon Kalman-filters is explored. The principles that are developed are general and can be applied to both vertical and lateral secondary suspensions, although the paper concentrates upon the vertical direction and quantifies the performance achievable for a particular combination of track characteristics.

Closed-loop vibration control of flexible space shuttle manipulator

This paper develops a new approach to dynamic modelling and closed-loop vibration damping control of a Hermes type multi-link flexible manipulator for two-dimensional vibratory motion of the vehicle/manipulator system in the pitch plane. The flexible links are modelled by replacing them by rigid members and fictitious rotational springs at the servo motor joints to give a dynamically equivalent system. Linear equations of motion are derived by Lagrangian formulation for small motions relative to an arbitrary baseline configuration and eigenvalue analysis shows that mode shapes and frequencies are relatively insensitive to the angle between the two main manipulator arms. Closed-loop modal control is then performed by velocity feedback from the active servo joints to the shoulder joint and a simple, stable damping control law is derived for the non-collocated sensor-actuator system. The emphasis is on a simplified approach which facilitates physical interpretation of vehicle/manipulator dynamics and control, and which can be used to verify more comprehensive multibody computer codes.

Active vibration control with model correction on a flexible laboratory grid structure

This paper presents experimental and computational comparisons of three active damping control laws applied to a complex laboratory structure. Two reduced structural models were used with one model being corrected on the basis of measured mode shapes and frequencies. Three control laws were investigated, a time-invariant linear quadratic regulator with state estimation and two direct rate feedback control laws. Experimental results for all designs were obtained with digital implementation. It was found that model correction improved the agreement between analytical and experimental results. The best agreement was obtained with the simplest direct rate feedback control.