Acceleration Feedback Research Articles

Feedback of Efficient Shock Acceleration on Magnetic-field Structure Inside Young Type Ia Supernova Remnants

Using an effective adiabatic index γ eff to mimic the feedback of efficient shock acceleration, we simulate the temporal evolution of a young type Ia supernova remnant (SNR) with two different background magnetic field (BMF) topologies: a uniform and a turbulent BMF. The density distribution and magnetic-field characteristics of our benchmark SNR are studied with two-dimensional cylindrical magnetohydrodynamic simulations. When γ eff is considered, we find that: (1) the two-shock structure shrinks and the downstream magnetic-field orientation is dominated by the Rayleigh–Taylor instability structures; (2) there exists more quasi-radial magnetic fields inside the shocked region; and (3) inside the intershock region, both the quasi-radial magnetic energy density and the total magnetic energy density are enhanced: in the radial direction, with γ eff = 1.1, they are amplified about 10–26 times more than those with γ eff = 5/3. While in the angular direction, the total magnetic energy densities could be amplified about 350 times more than those with γ eff = 5/3, and there are more grid cells within the intershock region where the magnetic energy density is amplified by a factor greater than 100.

Construction and Experimental Research of Active Vibration Control System of Voice Coil Motor with Integral Acceleration Feedback

Abstract The skyhook control technology is widely used in active vibration isolation and has proven effective. However, the absolute speed sensor used in the skyhook control technology is easily affected by external factors and may be easily damaged. There are few application scenarios for the skyhook control technology. To overcome this limitation, a brand-new approach is proposed for the design of an isolator that involves a voice coil motor (VCM) and an accelerometer. First of all, the proposed structure is introduced, and the dynamic model is established to achieve an analytical solution. Then, an integral acceleration feedback (IAF) algorithm is introduced and simulations are carried out. Finally, a prototype is constructed to verify its vibration isolation performance. From the experimental results, it can be concluded that the proposed active vibration control system (AVCS) can effectively reduce the peak value near the natural frequency, with a peak value reduction of 14.77 dB. Compared with the simulation results, the peak change rate at 12.5 Hz is 3.92%. AVCS with IAF can be applied to more application scenarios with a similar isolation effect to skyhook control technology.

Active feedback control on acoustic radiation of metastructure shell with low-frequency and broadband characteristics

Due to the tunable characteristics of elastic waves, the vibroacoustic coupling behavior of a mechanical metastructure is a hot topic of underwater vehicles. In this work, a metastructure shell with active feedback control is presented and fabricated. The dynamic effective density and sound pressure level are derived to find the influences of acceleration and displacement feedback control. Different from a single cylinder, a double cylinder structure has both in-phase and anti-phase modes. Numerical results are obtained by Fourier transform and harmonic series expansion. With the introduction of an active feedback control system, the reduction of acoustic radiation shows low-frequency and broadband characteristics. In addition, finite element simulation is applied to support numerical results and present vibroacoustic characteristics. Finally, an experiment is performed in the anechoic chamber to illustrate the quiet metastructure shell, which can be applied to new designs of underwater vehicles.

Integral reinforcement learning-based angular acceleration autopilot for high dynamic flight vehicles

During the synthesis of acceleration autopilots for high dynamic flight vehicles (HDFV), autopilots with feedback of angular acceleration (AFAA) have become more perspective with stringent requirements on response speed and high maneuverability, compared with autopilots with feedback of angular rate (AFAR). Integral reinforcement learning (IRL) method has now proved to be an effective technique for adaptive optimal control of partially unknown nonlinear systems. In this paper, a novel data-driven IRL algorithm with “actor–critic” structure is proposed for HDFV utilizing AFAA. As an advanced model-free approach, “actor–critic” based IRL algorithm learns optimal behaviors by observing the real-time responses from the environment under the action of nonoptimal control policies. Instead of solving algebraic Riccati equation directly, the control policy updates online via the solution of proposed IRL Bellman equation with sensed quantities. Numerical simulation is carried out to validate the effectiveness of proposed online IRL-based angular acceleration autopilot for HDFVs. Besides, the tracking performance under different wave commands, the robustness against parameter uncertainties and the noise attenuation capacity between classical optimal tracking approach and proposed IRL method are analyzed for AFAR and AFAA, respectively. Simulation results show that, angular acceleration autopilot with proposed integral RL algorithm possesses better tracking performance against various disturbances.

Active vibration control in robotic grinding using six-axis acceleration feedback

Industrial robots endure severe vibrations in the grinding process due to factors such as joint flexibility, low damping, and contact force fluctuations. Additionally, the motion control of the robot primarily relies on feedback signals from the motor-side encoders, while lacking motion state feedback from the load side. This exacerbates the robot vibrations, severely compromising the surface quality of the workpieces. To address this problem, an active damping control method for robotic grinding using six-axis acceleration feedback is proposed. This method realizes a simple, reliable, and efficient active vibration control without altering the robot body. A multi-sensor fusion Cartesian space six-axis accelerometer is designed and integrated into the robot end effector, achieving accurate feedback on the robot load side vibration state. The strategy of six-axis acceleration decoupling and principle of the vibration suppression with the acceleration feedback are explained. Compared with conventional sensing schemes, this reduces joint acceleration approximation errors and end vibrations. The robotic grinding experiments are carried out on aeronautic structural parts. Extensive case studies demonstrate that the proposed approach can effectively control the vibration caused by joint flexibility in the robot grinding process, and greatly improve the surface quality of workpieces. This method has great potential application in vibration suppression during robotic grinding and polishing.

Simulation of transient response of PID controller in an automated electro-pneumatic system using a single-acting cylinder in a clinical ventilator

Patients with COVID-19 are not eligible for any therapy. Patients who have had respiratory failure and are unable to provide oxygen via noninvasive means obtain supportive care in ICUs. Since the onset of the outbreak, every sick COVID-19 patient has received oxygen via a mechanical ventilator. This study describes and simulates the transient stability of systems in an automated pressure regulator utilizing a single-acting cylinder in a clinical ventilator. These components include horizontal controllers, control devices, connecting tubes, and PID for electro-pneumatic control. Increased system stability and nonlinearity in electro-pneumatic actuator systems are accomplished by the implementation of PID. The redesigned PID control architecture was enhanced with alternative acceleration feedback through the close loop with an integral control method to get the system stable. This introduces the standard value N from the outside vicious circle and applies a form control law to integrate all reference control supply through into the gadget. Even as proportional gain (Kp) gets increased, the controller output would increase proportionately while maintaining the exact degree of accuracy. A derivative term boosts the ability of the Kd regulator to "detect" malfunctions. The integral term of the Ki controller minimizes its set point distortion. The system was updated to make it feasible for transferrable knowledge and competencies by incorporating real industrial components. The completed fluid control system was simulated through FluidSIM, which is frequently helpful for educational purposes.

Thrust Microstepping via Acceleration Feedback in Quadrotor Control for Aerial Grasping of Dynamic Payload

Thrust Microstepping via Acceleration Feedback in Quadrotor Control for Aerial Grasping of Dynamic Payload

Quantifying the performance enhancement facilitated by fractional-order implementation of classical control strategies for nanopositioning

For most nanopositioning systems, maximizing positioning bandwidth to accurately track periodic and aperiodic reference signals is the primary performance goal. Closed-loop control schemes are employed to overcome the inherent performance limitations such as mechanical resonance, hysteresis and creep. Most reported control schemes are integer-order and combine both damping and tracking actions. In this work, fractional-order controllers from the positive position feedback family namely: the Fractional-Order Integral Resonant Control (FOIRC), the Fractional-Order Positive Position Feedback (FOPPF) controller, the Fractional-Order Positive Velocity and Position Feedback (FOPVPF) controller and the Fractional-Order Positive, Acceleration, Velocity and Position Feedback (FOPAVPF) controller are designed and analysed. Compared with their classical integer-order implementation, the fractional-order damping and tracking controllers furnish additional design (tuning) parameters, facilitating superior closed-loop bandwidth and tracking accuracy. Detailed simulated experiments are performed on recorded frequency-response data to validate the efficacy, stability and robustness of the proposed control schemes. The results show that the fractional-order versions deliver the best overall performance.

Robust delayed resonator with acceleration feedback — design by double root assignment and experimental validation

A combination of analytical and numerical time-delay system spectrum-shaping tools are applied to the design of the robust delayed resonator with an acceleration feedback. First, the delayed resonator model is turned into a dimension-less form with the objective to generalize the derived results. The main theoretical result is then provided as a complete parameterization of the proposed resonator feedback with two delay terms to assign a pair of roots with multiplicity two on the imaginary axis. In the frequency domain, the double roots are projected to widen the stopband in the active absorber frequency response, which increases its robustness in vibration suppression. On the other hand, they have a destabilizing effect on the overall system dynamics. The stabilization is subsequently performed by an additional controller via spectral optimization. The design is thoroughly validated by both simulations and experiments where the results are compared with the classical delayed resonator with lumped delay acceleration feedback.

Active vibration isolation by emulating the inerter through relative acceleration feedback

This study focuses on the realisation of a small-scale inerter by relative acceleration feedback and its use to isolate vibration. Two accelerometers attached to the two mechanical terminals of an electrodynamic force actuator are used to obtain the relative acceleration signal. This signal is then amplified by a constant gain and fed back to the two electrical terminals of the electrodynamic actuator as a voltage command. This sensor-actuator system is coupled to a two Degree-Of-Freedom (DOF) mechanical oscillator to study the feedback loop’s stability and the maximum achievable inertance effect. A fully coupled simulation model including the dynamics of the two inertial accelerometers and the electrodynamic actuator is developed. It is shown that, because of the active control system emulating an inerter, an antiresonance appears in the transfer admittance function of the two DOF mechanical system. Therefore, significant vibration isolation effect can be achieved in the narrow frequency band around the antiresonance. The antiresonance frequency is easily tuned by adjusting the feedback gain. The synthetized inertance is a complex frequency dependent function, which is predominantly real-valued in the frequency range between 5 and 1600 Hz. It is shown that it does not depend on the mechanical system properties, but only on the properties of the transducers used and the signal conditioning in the feedback loop. As a result, this frequency range can be adjusted according to a particular application.

On Practical Implementations of Connected Vehicles: The Issue of Acceleration Feedback

On Practical Implementations of Connected Vehicles: The Issue of Acceleration Feedback

Compensated acceleration feedback based active disturbance rejection control for launch vehicles

In this paper, the attitude tracking and load relief control problems against wind disturbances and uncertain aerodynamics as well as the engine thrust of launch vehicles are studied. Firstly, a framework of Compensated Acceleration Feedback based Active Disturbance Rejection Control (CAF-ADRC) is established to achieve both desired attitude tracking and load relief performances. In particular, the total disturbance that includes the effects caused by both aero-coefficient perturbations and disturbances is estimated by constructing an Extended State Observer (ESO) to achieve attitude tracking. Furthermore, combined with the normal acceleration due to the engine thrust, the accelerometer measurement is also compensated to enhance the load relief effect. Secondly, the quantitative analysis of ESO and the entire closed-loop system are studied. It can be concluded that the desired attitude tracking and load relief performances can be achieved simultaneously under the proposed approach. Besides, tuning laws of the proposed approach are systematically given, which are divided into ESO, Proportional Derivative (PD) and Compensated Acceleration Feedback (CAF) modules. Moreover, the performances under CAF-ADRC approach can be better than those under CAF based PD (CAF-PD) approach by tuning load relief gain. Finally, the approach presented is applied to a typical control problem of launch vehicles with wind disturbances and parameter uncertainties.

Efficacy of a class of resonant nonlinear controllers of fractional-order for adaptive vibration control—Analysis, simulations and experiments

The efficacy of different class of resonant controllers has been successfully established for active vibration control. This class of controllers utilize a second-order filter fed back with the structural response (displacement, velocity or acceleration) and the control signal is synthesized as the linear/nonlinear function of the filter response. However, the performance of the controller largely depends on the tuning of the filter frequency to the structural natural frequency. Thus, for structural systems where the natural frequency and the excitation frequency are uncertain, one requires to tune the filter frequency adaptively. The present paper introduces two computationally efficient, fractional-order nonlinear adaptive resonant controllers with acceleration feedback for vibration control. The control signal is synthesized as the linear/nonlinear function of the filter variable and its fractional order derivative. Two parameters, namely the filter frequency and the control gain, are adaptively varied to control the phase and amplitude of the control signal, respectively. The objective of frequency adaptation is to maintain the phase of the control signal in the quadrature of the system displacement/acceleration. Theoretical analysis of the system is performed by the method of multiple scales under the assumption of slowly varying parameters. The results are verified by both numerical simulations and experiments. The theoretical and experimental results demonstrate the robustness of the proposed adaptive control against uncertainties in excitation force and system parameters. It is comprehensively shown that the fractional-order control is superior to the integer-order control already studied in previous works. Moreover, the effect of feedback time-delay is also studied, and it is shown that the fraction-order control can offset the detrimental effects of time-delay on the frequency response of the system.

Hybrid impedance and admittance control for optimal robot–environment interaction

AbstractCompliant interaction between robots and the environment is crucial for completing contact-rich tasks. However, obtaining and implementing optimal interaction behavior in complex unknown environments remains a challenge. This article develops a hybrid impedance and admittance control (HIAC) scheme for robots subjected to the second-order unknown environment. To obtain the second-order target impedance model that represents the optimal interaction behavior without the accurate environment dynamics and acceleration feedback, an impedance adaptation method with virtual inertia is proposed. Since impedance control and admittance control have complementary structures and result in unsatisfactory performance in a wide range of environmental stiffness due to their fixed causality, a hybrid system framework suitable for the second-order environment is proposed to generate a series of intermediate controllers which interpolate between the responses of impedance and admittance controls by using a switching controller and adjusting its switching duty cycle. In addition, the optimal intermediate controller is selected using a mapping of the optimal duty cycle to provide the optimal implementation performance for the target impedance model. The proposed HIAC scheme can achieve the desired interaction and impedance implementation performance while ensuring system stability. Simulation and experimental studies are performed to verify the effectiveness of our scheme with a 2-DOF manipulator and a 7-DOF Franka EMIKA panda robot, respectively.

Hybrid vibration absorber for self-induced vibration suppression: exact analytical formulation for acceleration feedback control

Hybrid vibration absorbers (HVAs) are an effective solution for vibration mitigation. They combine the passive vibration absorption mechanism of tuned mass dampers (TMDs) with feedback-controlled actuators, similar to active mass dampers. This enables them to overcome the performance of both systems in terms of vibration mitigation effectiveness and energy consumption, respectively. This study evaluates the vibration suppression capabilities of an HVA against self-excited oscillations. A single-degree-of-freedom host system encompassing a negative damping term is considered. First, the possibility of enhancing the stability properties of an optimally tuned TMD through a feedback controller is evaluated. The analysis shows that this approach cannot improve the absorber’s performance. Subsequently, simultaneous optimization of all the HVA parameters is considered. Our results reveal that this approach significantly enhances the system’s performance. All analysis is carried out analytically without resorting to approximations. Finally, the absorber is numerically applied to suppress friction-induced vibrations and galloping instabilities.

Calibration of Viscous Damping–Stiffness Control Force in Active and Semi-Active Tuned Mass Dampers for Reduction of Harmonic Vibrations

Tuned mass dampers (TMDs) are commonly used to mitigate vibrations in civil structures. There is a growing demand for new solutions that offer similar effectiveness as TMDs but with reduced mass. In this context, this paper investigates active (ATMD) and semi-active (STMD) tuned mass dampers with relative displacement and velocity feedback. The control force of the ATMD is assumed to be the sum of viscous damping and either positive or negative stiffness forces. This control force is calibrated for a specific parameter K such that the effectiveness of the ATMD in reducing harmonic vibrations matches that of the TMD with K times larger mass. The optimal calibration is derived based on the mathematical reformulation of an existing optimal acceleration feedback control algorithm. The control approach for the ATMD is then applied to the STMD. Subsequently, the sub-optimal STMD is analyzed, with a focus on its limitations arising from the clipping of active forces. Finally, the paper presents a calibration of the STMD using a numerical optimization method. It is demonstrated that the maximum achievable performance of the numerically optimized STMD matches that of the TMD with three times larger mass.

Variable Admittance Control in Sliding Mode for Robust Physical Human–Robot Interaction

Intuitive and comfortable physical human–robot interaction (pHRI) can be realized by changing impedance/admittance parameters corresponding to human interaction. However, this dynamic adjustment may result in drastically changed system dynamics, which usually give rise to system instability. We introduce a power envelope regulation strategy designed to constrain the variability of admittance parameters, thereby ensuring system passivity and mitigating the risk of instability. Then, sliding mode control (SMC) is employed to yield stable and robust performance. A new sliding surface is proposed based on feedback linearization, which shows improved tracking performance and stability compared to a conventional sliding surface. The effectiveness of the proposed sliding surface and associated control is theoretically validated. Notably, our modified sliding surface works universally, regardless of the order of the desired admittance equation. The trade-off between system chattering and robustness is effectively managed using a variable–boundary approach, which dynamically adjusts system constraints to optimize performance. In addition, a control algorithm combining acceleration feedback and sliding mode is proposed, showing improved robustness and tracking accuracy performance compared with applying the proposed SMC algorithm exclusively. The efficacy of these methodologies is substantiated through numerical simulations and empirical experiments.

Seismic Behavior Assessment of RC Buildings Controlled by Passive and Active Techniques

In this paper, a numerical study was carried out on the effectiveness of the active earthquake control method in improving the earthquake response of RC buildings. High damping rubber bearing design was made according to the criteria of the Uniform Building Code. Three different types of isolators were obtained geometrically. Passive earthquake control of the building was provided by placing these isolators under the columns. For active earthquake control of the building, controller design was realized by integrating it into the FE transient analysis in ANSYS. The active earthquake control design was studied using a force-based and displacement-based controller with acceleration and displacement feedback. The linear dynamic earthquake analysis in the time history of all three states of the building (un-controlled, passive, and active-controlled) was made using the acceleration record of the Seferihisar (İzmir) earthquake. When the results are examined, it is seen that the active earthquake control method provides almost all of the positive behavior expected from the passive earthquake control method. In addition, it eliminates some of the disadvantages of the passive earthquake control method.

Evaluation and Comparison of SEA Torque Controllers in a Unified Framework

Series elastic actuators (SEA) with their inherent compliance offer a safe torque source for robots that are interacting with various environments, including humans. These applications have high requirements for the SEA torque controllers, both in the torque response as well as interaction behavior with its environment. To differentiate state of the art torque controllers, this work introduces a unifying theoretical and experimental framework that compares controllers based on their torque transfer behavior, their apparent impedance behavior, and especially the passivity of the apparent impedance (i.e., their interaction stability) as well as their sensitivity to sensor noise. We compare classical SEA control approaches such as cascaded PID controllers and full state feedback controllers with advanced controllers using disturbance observers, acceleration feedback and adaptation rules. Simulations and experiments demonstrate the trade-off between stable interactions, high bandwidths and low noise levels. Based on these trade-offs, an application-specific controller can be designed and tuned, based on desired interaction with the respective environment.

Stability compensation of an admittance-controlled cartesian robot considering physical interaction with a human operator

In human-machine systems, admittance control is widely used for controlling robots. However, the problem with this method is that the stability can be impacted by the stiffness of the machine and the human operator. In order to minimize the oscillation issue that is caused by insufficient structure stiffness, this study used compensation methods, specifically feed-forward and acceleration feedback. Simulation results show that both compensation methods can expand the stability region of the system. Nevertheless, feedback compensation is more appropriate than feed-forward when taking into account uncertainties in the structure parameters of the system. Even when the system is not perfectly implemented, feedback compensation can keep the system stable, whereas feed-forward compensation causes a significantly reduced stability region. From the experiment, it is also confirmed that the feedback system has an advantage over the feed-forward system, and this simple feedback using an accelerometer can compensate for the insufficient stiffness of the robot structure and greatly enhance the stability of the human-machine system.