Positive Acceleration Feedback Research Articles

Controlling self-excited vibration of a nonlinear beam by nonlinear resonant velocity feedback with time-delay

In this paper, the efficacy of velocity feedback based nonlinear resonant controller is proposed to control the free and forced self-excited vibration of a nonlinear beam. The velocity signal obtained from the sensor is fed through a second-order filter and the nonlinear function of the derivative of the filter variable is used to obtain the control force. The resulting control system being a band-pass one, is believed to be superior to other resonant control schemes like Positive Position Feedback (PPF) control and Acceleration Feedback Control (AFC). To the best of the authors’ knowledge, it is the first attempt to explore the efficacy of resonant nonlinear velocity feedback controller for mitigating self-excited vibration. Analytical results are obtained using multiple time-scale method, are validated with the data obtained from direct numerical simulation carried out in Matlab Simulink model. Analytical results of the uncontrolled system show the periodic, quasi-periodic as well as chaotic behavior. It is observed that the proposed controller can reduce the amplitude of vibration by a significant level near primary resonance. Moreover, the Hopf bifurcations are eliminated by the control action. It is also observed that the proposed controller can reduce the amplitude of the chaotic oscillation significantly. The effect of the actuation delay in the feedback loop is also explored. It is observed that the effect of time delay is detrimental to system performance.

Bandwidth enhancement in damping control for piezoelectric nanopositioning stages with load uncertainty: Design and implementation

High bandwidth and fast tracking of desired trajectories are eagerly required in various applications that use piezoelectric nanopositioning stages, especially in atomic force microscopes where the vibration stemming from lightly damped modes of stages is a challenging control problem. In this study, a bandwidth-enhanced positive acceleration, velocity, and position feedback damping controller is presented to achieve the tracking bandwidth exceeding the first resonant frequency through using a novel pole-shift method. The stability of the positive feedback damped loop is examined by a mixed passivity, small-gain approach, and Nyquist theorem framework. Also, in conjunction with a proportional–integral tracking controller, robust stability is addressed for load uncertainties. Experimental application to a piezoelectric nanopositioning stage demonstrates that a closed-loop bandwidth of 282.5 Hz is achieved, which exceeds the dominating resonance of the stage at 210 Hz. The achieved bandwidth is 1.35 times larger than the dominating resonance, which is a competitive result among most existing damping control approaches. Comparative tracking results verify the effectiveness of the proposed control scheme on the suppression of low-frequency hysteresis and tracking performance of high-speed triangular waves under load variations.

Building Vibration Control by Active Mass Damper With Delayed Acceleration Feedback: Multi-Objective Optimal Design and Experimental Validation

The building structural vibration control by an active mass damper (AMD) with delayed acceleration feedback is studied. The control is designed with a multi-objective optimal approach. The stable region in a parameter space of the control gain and time delay is obtained by using the method of stability switch and the numerical code of NDDEBIFTOOL. The control objectives include the setting time, total power consumption, peak time, and the maximum power. The multi-objective optimization problem (MOP) for the control design is solved with the simple cell mapping (SCM) method. The Pareto set and Pareto front are found to consist of two clusters. The first cluster has negative feedback gains, i.e., the positive acceleration feedback. We have shown that a proper time delay can enhance the vibration suppression with controls from the first cluster. The second cluster has positive feedback gains and is located in the region which is sensitive to time delay. A small time delay will deteriorate the control performance in this cluster. Numerical simulations and experiments are carried out to demonstrate the analytical findings.

Positive acceleration, velocity and position feedback based damping control approach for piezo-actuated nanopositioning stages

This paper proposes a new damping control approach with positive acceleration, velocity and position feedback (PAVPF) scheme for piezo-actuated nanopositioning stages to implement high-bandwidth operation. To achieve this objective, the intrinsic hysteresis nonlinearity of the piezoelectric actuator is firstly handled by a feedforward compensator with a modified Prandtl–Ishlinskii model. Afterwards, the PAVPF controller with the pole-placement method is implemented to suppress the lightly damped resonant mode of the hysteresis compensated system. With the PAVPF controller, the poles of the damped system in a third-model can be placed to arbitrary positions with an analytical method. Finally, for accurately tracking a predefined trajectory, a high-gain proportional-integral (PI) controller is designed, which could deal with the disturbance and the unmodeled dynamics. For verifying the proposed PAVPF-based control approach, comparative experiments with positive velocity and position feedback controller and with PI controller are conducted on a piezo-actuated nanopositioning stage. Experimental results demonstrate that the developed control approach with PAVPF controller is effective on damping control and improves the control bandwidth of the conventional PI controller from 111 Hz to 766 Hz, which leads to the significant increase of the tracking speed.

Impedance control of series elastic actuators: Passivity and acceleration-based control

Series elastic joints allow force and impedance controllers to be implemented on high torque and high power density motors. Several impedance controllers have been proposed whose stability is usually analyzed by means of passivity-based tools such as the Z-width characterization. This paper proposes an overview of existing impedance control solutions for series elastic joints and derives the passivity characterizations that are still missing in the literature, thus providing a complete and coherent overview of the existing solutions. Within this overview, we highlight the advantages of impedance control based on positive acceleration feedback showing improved stability robustness and impedance accuracy with respect to existing solutions. These advantages are theoretically motivated (considering ideal conditions) and experimentally validated.

Integrated Control of Thermally Induced Vibration and Quasi-Static Deformation of Space Truss

Dynamic vibration and quasi-static deformation will occur simultaneously for flexible space structures subjected to sudden thermal loads. In this paper, the integrated controller based on modified positive position feedback (PPF) compensator is proposed as an innovative controller for active deformation reduction in flexible space trusses. The controller uses the concept of positive acceleration feedback combined with integral position feedback to provide effective vibration suppression of multiple modes and compensator of quasi-static deformation. To solve the problem of placement optimization for both sensors and actuators, the discrete glowworm swarm optimization (GSO) algorithm based on genic binary coding is suggested. A cantilevered truss is taken as an example for numerically evaluating the performance of the controller for thermally induced deformation control. Numerical results demonstrate that the discrete GSO algorithm is feasible in solving the combinatorial optimization problem. And the proposed controller is significantly effective in controlling both steady-state deformation and transient vibration.

Active vibration suppression through positive acceleration feedback on a building-like structure: An experimental study

This work deals with the structural and dynamic analysis of a building-like structure consisting of a three-story building with one active vibration absorber. The base of the structure is perturbed using an electromagnetic shaker, which provides forces with a wide range of excitation frequencies, including some resonance frequencies of the structure. One beam-column of the structure is coupled with a PZT stack actuator to reduce the vibrations. The overall mechanical structure is modeled using Euler–Lagrange methodology and validated using experimental modal analysis and Fine Element Method (FEM) techniques. The active control laws are synthesized to actively attenuate the vibration system response via the PZT stack actuator, caused by excitation forces acting on the base of the structure. The control scheme is obtained using Positive Acceleration Feedback (PAF) and Multiple Positive Acceleration Feedback (MPAF) to improve the closed-loop system response. Some experimental results are included to illustrate the overall system performance.

Control of an Industrial Robot using Acceleration Feedback

A controller using acceleration feedback has been applied to a flexible robot for which the position and velocity of the load are not measured. It is shown that acceleration feedback allows an exact tracking of the motor position, irrespective of the non-linear flexibilities of the axes and of the measurement disturbances. This easy-to-tune algorithm whose main control parameters are the modal masses of the motor and load part, and only consists of a positive acceleration feedback plus a PD controller, has been validated on an industrial robot with orthogonal axes.

Intelligent Material and Fluid Systems. Development of Velocity and Displacement Sensor for Vibration Control.

This study is concerned with the development of a new type of sensor for vibration control. This sensor belongs to the class of seismo-type. The main features of this sensor compactness, robust against shock and also to measure velocity and displacement simultaneously under the low frequency range. Until now, in order to measure the absolute displacement under low frequencies, the conventional sensor has to be made with its low natural frequency. To realize low natural frequency, sensor must have large mass with soft spring. That is to say, these sensors are big and weak against shock. To solve these problem, the proposed sensor uses positive displacement and negative acceleration feedback for reducing its natural frequency actively. Therefore, it is possible to construct a sensor with light mass and hard spring for realizing the requirement.

Force regulation and contact transition control

In this article, a new sensor-referenced control method using positive acceleration feedback together with a switching control strategy is developed for robot impact control and force regulation. The robot dynamic model is feedback-linearized and decoupled for the free-motion mode, the phase-transition mode, and the constrained-motion mode. Considering the detection of the impact as an event, the event-driven switching control strategy is used to deal with the inadvertent loss of contact of the robotic manipulator. Bouncing can be eliminated after finite switches. A stable transition can be achieved with a nonzero impact velocity; large impact forces can be avoided and the output force can be regulated after contact is established. Stability analysis based on the Lyapunov-like method is given for the proposed system. The scheme was implemented and tested on a 6 DOF PUMA 560 robot arm.

Force and Contact Transition Control via Nonlinear Feedback and Event-based Planning

In this paper, a new sensor-referenced control method using positive acceleration feedback together with a switching control strategy is developed for robot impact control and force regulation. The robot dynamic model is feedback linearized and decoupled for the free motion mode, and the phase transition mode, as well as the constrained motion mode. Stable contact can be made with a nonzero impact velocity and large impact forces can be avoided. Consider the detection of the impact as an event. The event driven switching control strategy is used to deal with the inadvertent loss of contact of the robotic manipulator. Bouncing can be eliminated after finite switches. A stable transition can be achieved and the output force can be regulated after contact is established. Stability analysis based on the Liapunov-like method is given for the proposed system. The scheme was implemented and tested on a 6 DOF PUMA 560 robot arm.

Feedback Control Stability Analysis of Linear Slider Mechanism.

Mechanical control can be made stable by taking into consideration mechanical resonance frequency and antiresonance frequency. A mechanical structure has different characteristics at each location at which force is applied and measuring location. The characteristics are different due to resonance frequency and antiresonance frequency. Antiresonance frequencies are determined by zero amplitude of dynamic behavior. Furthermore, their frequencies affect the control stability. This paper presents a method to distinguish between control stability and instability of the linear slider mechanism. In this method, control stability is distinguished to calculate the damping value of a multi-degree-of-freedom mechanism with control. Control algorithms are applied to positive acceleration feedback control and negative velocity feedback control.