Proportional Control Strategy Research Articles

Force myography controlled multifunctional hand prosthesis for upper-limb amputees

Existing myoelectric prostheses can provide solutions to amputees for performing activities of daily livings. However, there are several issues with these prostheses (1) performance are affected mainly by sweat, electrode shift, motion artifact, interference, etc. (2) are expensive (3) have complex control schemes.This paper presents an affordable hand prosthesis solution for transradial amputees, which uses force myography (FMG) as a control signal in place of electromyography (EMG) signal. A novel FMG sensor was designed to detect mechanical muscle contractions from the residual forearm of amputees. Two distinct control strategies were formulated for translating the FMG signals from the sensor to the control commands for driving custom-made prosthetic hands.Prosthetic hand prototype 1 with a proportional control scheme was developed and verified on five amputees. Subjects wearing the hand were able to grasp various objects using their intent of muscular contractions.Fuzzy logic based classification scheme with an offline success rate above 97 % was established for identifying six different hand gestures from only single-channel FMG data. Further, the system, along with the threshold control, was implemented for the developed hand prototype 2 to obtain six distinct grip patterns. The real-time testing of hand on thirteen subjects (five amputees and eight intact) showed a success percentage above 95 % in performing dexterous grasping operations.As compared to the presently available hands, the hand prototype 2 displayed comparable features at such a low-cost price. However, with limited functionality, hand prototype 1 is an affordable, practical, intuitive, and faster version of the prosthetic hand.

Robust Simultaneous and Proportional Myoelectric Control Scheme for Individuals with Transradial Amputations.

Commercial myoelectric prostheses need to be accurate and clinically viable to be successful. This study proposed a simultaneous and proportional control scheme with frequency division technique (SPEC-FDT) to address limitations in current myoelectric prosthesis control, specifically to address non-stationaries such as contraction level variations and unintended activations. Twenty able-bodied participants (14 males and 6 females, age 23.4 ± 3.0) and four individuals with transradial amputations performed wrist movements (flexion/extension, rotations and combined movements) in two degrees-of freedom virtual tasks. The SPEC-FDT had a completion rate (CR)>90% for both control and clinical participants which was significantly higher than the conventional technique (CR=68%). Our results showed that SPEC-FDT is highly accurate for both able-bodied and clinical participants and provides a robust myoelectric control scheme allowing for increased prosthetic hand functions.

Analysis of motor unit activities during multiple motor tasks by real-time EMG decomposition: perspective for myoelectric control.

Surface electromyography (EMG) decomposition techniques have been applied for human-machine interfacing by decoding neural information, while most of decomposition approaches work offline. Here, we apply an online decomposition scheme to decode motor unit activities during three motor tasks, and measure the recognition accuracy of motor type and activation level using the decomposition results. High-density surface EMG signal were recorded from forearm muscles of six able-bodied subjects. The EMG signals were decomposed into motor unit spike trains (MUST) with a sliding window of 100 ms. The computation complexity had time consumption < 50 ms in each window. Most identified motor units discharged during only one motor task. On average, over 5 MUSTs were identified for each motion and the recognition accuracy based on motor unit activities was > 99%. The discharge rate of motor units was highly correlated with the activation level of each motion with an average correlation coefficient of 0.94 ± 0.04. These results indicate the feasibility of an online, multi-motion, and proportional control scheme based on neural decoding in a non-invasive way.

Linear regression with frequency division technique for robust simultaneous and proportional myoelectric control during medium and high contraction-level variation

Myoelectric controlled prostheses systems have evolved significantly over the last few decades, however, there remains a need for more robust systems. Clinically, prosthesis control schemes must be robust to various Electromyography (EMG) signal non-stationarities such as unintended activations and contraction level variations to ensure appropriate operation of the prosthesis. This study compared performance measures between two control schemes, linear regression with frequency division technique (LR-FDT) and standard bandpass processing (LR-Bandpass) for two contraction levels (medium and high) to investigate robustness to EMG non-stationarities. Twenty able-bodied control (14 males and 6 females, age 23.4 ± 3.0) and four individuals with trans-radial amputations performed wrist movements (flexion/extension, rotations and combined movements) in two degrees-of-freedom (DOF) virtual tasks. For control participants, LR-FDT had a mean completion rate (CR) of 95.33%, which was significantly higher than LR-Bandpass with a CR of 64.08% (p<0.001). The clinical participants showed a CR>90% using LR-FDT and had an average CR of 69.8% using LR-Bandpass. LR-FDT method performed significantly better in all other performance indices in at least one movement type. There was no significant difference in the performance of LR-FDT between medium and high contraction levels. This study showed that LR-FDT is advantageous in online myoelectric control as it introduces a more accurate, robust and contraction level invariant control scheme for performing prosthetic hand movements. This study is the first to use frequency-based features with a simultaneous and proportional myoelectric control (SPEC) scheme.

Adaptive Proportional Complex Integral Control Strategy of Three-Phase Grid-connected PV Inverter

The performance of conventional controller of three-phase grid-connected inverters possibly deteriorate during grid frequency drift. In this paper, an frequency adaptive proportional complex integral (PCI) controller with frequency locking loop (FLL) was proposed, the FLL was utilized to adjust the resonant frequency of PCI automatically, and the zero current steady error was achieved by PCI controller. The validity of the proposed control scheme was demonstrated through results of simulation and experimental.

Research on Parallel Control Technology of Three-phase Inverter Based on Multiple Proportional Resonance Controller

The parallel operation of multiple inverters can increase the fault tolerance of the system and prevent the occurrence of major accidents. At the same time, it also has strong flexibility, which can reduce the volume and weight of the system and increase the capacity of the system, which is very attractive in the application of uninterruptible power supply. In the inverter parallel system, the circulation will be generated between the inverters due to the existence of the path. Circulation can cause current distortion, reduce system performance, and even damage equipment in severe cases. In order to effectively suppress the generation of circulation, this paper proposes a multiple proportional resonance control strategy for the parallel three-phase inverter system, that is, the voltage outer loop is controlled by PI+PR, and the current inner loop is controlled by PR. Two three-phase inverter parallel systems are built in MATLAB/Simulink simulation environment to compare and analyze the control effect of uncontrolled, traditional PI control and multiple PR control. The simulation results show that the proposed control method has a good suppression effect on the circulation generated in the inverter parallel system, even under the condition of unbalanced load.

Feedback Linearization-Based Perimeter Controllers for Oversaturated Regions

This paper concerns the perimeter control problem in the oversaturated region. The road network system is a nonlinear system. However, the existing achievements in the perimeter control setting are obtained by partially linearizing the system model around the point of interest, which is a local linearization and probably leads to lower traffic performances. To this end, a feedback linearization-based proportional and integral perimeter controller is developed to regulate the overall traffic state towards the desired accumulation state. Theoretical analysis demonstrates that the proposed feedback linearization-based control method can guarantee the exponentially asymptotic convergence of the protected road network state to the desired one. To evaluate the proposed methodology, extensive simulation tests are conducted, in which the proposed controller is compared with the existing proportional and integral control strategy. The results indicate that the proposed feedback linearization-based proportional and integral perimeter controller can: (i) relieve the overall congestion in the urban network; and (ii) enhance the traffic performance in terms of the cumulative throughput and the mean speed.

Active tuning of the vibration band gap characteristics of periodic laminated composite metamaterial beams

A novel strategy is proposed to investigate the vibration band-gap and active tuning characteristics of the laminated composite metamaterial beams. The piezoelectric actuator/sensor pairs are periodically placed along the laminated composite beam axis so that the vibration frequency band-gap and active tuning characteristics can be induced. The dynamic equations of the laminated composite metamaterial beams bonded by the piezoelectric actuator/sensor pairs are established based on the Euler–Bernoulli beam theory. The negative proportional feedback control strategy is employed to provide the positive active control stiffness for the piezoelectric actuator/sensor patches. The spectral element method is used to calculate the dynamic responses of the laminated composite metamaterial beams with the periodically placed piezoelectric patches, and the calculation accuracy for the dynamic responses is validated by the finite element method. The results demonstrating the high-performance vibration band-gap properties in the low-frequency ranges can be achieved by properly designing the sizes and the number of the piezoelectric patches. Moreover, the vibration band-gap characteristics, especially the band-gap width and the normalized band-gap width with respect to the considered excitation frequency range, can be significantly changed by tuning the structural parameters of the piezoelectric actuators and sensors. In addition, the cross-ply angle of the laminated composite metamaterial beams has significant influences on the band-gap characteristics and the vibration reduction performance of the laminated composite beam structures.

Development of an Affordable Myoelectric Hand for Transradial Amputees

Upper limb amputations seriously affect a patient's life by restricting their ability in performing various tasks. Prosthetic hands are considered the primary method to reinstate the lost capabilities of such amputees. However, the presently available prosthetic devices are unable to fulfill the requirements of users due to their excessively high cost, limited functionality, heavy weight, unnatural operation, and complexity. This article presents an affordable and simple control-based myoelectric hand for transradial amputees. The hand setup mainly consists of a self-designed surface electromyography (sEMG) sensor, a microcontroller unit and a five-fingered, intrinsically actuated 3D printed hand for dexterous operations. The developed hand was implemented with proportional control scheme and was successfully tested on five amputees (with missing lower forearms) for performing grasping activities of different objects. Further, the closing time and grip force at the fingertips were also determined for the hand to compare its performance with the commercially available hands.

A 67-fsrms Jitter, −130 dBc/Hz In-Band Phase Noise, −256-dB FoM Reference Oversampling Digital PLL With Proportional Path Timing Control

An LC oscillator-based reference oversampling PLL (OSPLL) is proposed in this work. An LC digitally controlled oscillator (DCO) with proportional path gain profile control and DCO tuning pulse timing control scheme is proposed for optimal phase noise. Designed in 28-nm CMOS process, the proposed PLL achieves 67.1-fs RMS-jitter with 5.2-mW power consumption, which translates to −256-dB FoM. The in-band phase noise of the PLL is −130 dBc/Hz at 4-GHz output frequency. The reference spur of the proposed PLL is −78 dBc.

Modelling, identification, implementation and MATLAB simulations of multi-input multi-output proportional integral-plus control strategies for a centrifugal chiller system

The objective of this paper is to investigate a new design and real-time implementation approach of a predictive proportional integral-plus (PIP) closed-loop control strategy for a centrifugal chiller HVAC system. By using the analytical model of the plant, linear discrete-time multi-input multi-output (MIMO) autoregressive moving average exogenous (ARMAX) polynomial models were developed. The structure of developed ARMAX models is straightforward, and they are suitable to capture the complex dynamics of the centrifugal chiller plant. Fundamentally, these identified models use the least-squares estimation (LSE) method to evaluate the polynomials coefficients and model parameters implemented using specific tools provided by MATLAB's system identification toolbox. The new modelling approach is beneficial for simulation purposes to prove the efficiency of the proposed closed-loop control strategy, the tracking performance, and its robustness to possible changes in the load disturbance and noise level of measurement sensors.

Modelling, identification, implementation and MATLAB simulations of multi-input multi-output proportional integral-plus control strategies for a centrifugal chiller system

Modelling, identification, implementation and MATLAB simulations of multi-input multi-output proportional integral-plus control strategies for a centrifugal chiller system

Finite-time nonfragile time-varying proportional retarded synchronization for Markovian Inertial Memristive NNs with reaction–diffusion items

The issue of synchronization for a class of inertial memristive neural networks over a finite-time interval is investigated in this paper. Specifically, reaction–diffusion items and Markovian jump parameters are both considered in the system model, meanwhile, a novel nonfragile time-varying proportional retarded control strategy is proposed. First, a befitting variable substitution is invoked to transform the original second-order differential system into a first-order one so that the corresponding synchronization error system that is represented by a first-order differential form is established. Second, by utilizing the integral inequality technique, reciprocally convex combination approach and free-weighting matrix method, a less conservative synchronization criterion in terms of linear matrix inequalities is obtained. Finally, three simulations are exploited to illustrate the feasibility, practicability and superiority of the designed controller so that the acquired theoretical results are supported.

Point-actuated feedback control of multidimensional interfaces

AbstractWe consider the application of feedback control strategies with point actuators to multidimensional evolving interfaces in order to stabilize desired states. We take a Kuramoto–Sivashinsky equation as a test case; this equation arises in the study of thin liquid films, exhibiting a wide range of dynamics in different parameter regimes, including unbounded growth and full spatiotemporal chaos. The controls correspond physically to mass-flux actuators located in the substrate on which the liquid film lies. In the case of partial state observability, we utilize a proportional control strategy where forcing at a point depends only on the local observation. We find that point-actuated controls may inhibit unbounded growth of a solution, if the actuators are sufficient in number and in strength, and can exponentially stabilize the desired state. We investigate actuator arrangements, and find that the equidistant case is the most favourable for control performance, with a large drop in effectiveness for poorly arranged actuators. Proportional controls are also used to synchronize two chaotic solutions. When the interface is fully observable, we construct model-based controls using the linearization of the governing equation. These improve on proportional controls and are applied to stabilize non-trivial steady and travelling wave solutions.

Development of a generalized proportional integral control strategy for level control in a coupled tank system

This work presents the analysis and design of a generalized proportional integral control strategy for a level control in a coupled tank system, such analysis is made under the active disturbance rejection. The principle objective is to show the advantages of the control strategy generalized proportional integral as to signals tracking and disturbance rejection, compared to conventional control techniques such as the proportional integral derivative control. To validate the process, the modeling of the system was carried out and with this model simulations were carried out under nominal conditions, applying the two control strategies. It was found that the generalized proportional integral control presented a better performance since it achieves a lower mean squared error percentage than the proportional integral derivative control, even in the presence of disturbances.

Sliding Mode Control Scheme for a CLLC Resonant Converter

In this paper, a comprehensive sliding mode control (SMC) loop design for a CLLC resonant converter is proposed. The major objectives of the proposed SMC are to improve the converter dynamics and to achieve a tight output voltage regulation with respect to any parameter variations and external disturbances. The sliding surface coefficients are selected to ensure both large- and small-signal stability for the robustness of the converter under different operating conditions. Furthermore, system dynamic performances considering the error dynamics and overshoots are investigated. To validate the proposed algorithm, a hardware prototype of a bi-directional CLLC resonant converter for plug-in electric vehicle applications is developed and tested up to 1 kW, and the effectiveness of the proposed control solution is verified by the load transients and start-up tests. At a 100% step-change in load power, the SMC achieves 1 ms settling time, which is approximately 0.9 ms faster than the conventional proportional integral control strategy.

Neural-network-enhanced torque estimation control of a soft wearable exoskeleton for elbow assistance

Soft wearable exoskeletons are a new approach for the applications of power assistance and rehabilitation training. In the present work, a neural-network-enhanced torque estimation controller (NNETEC) is proposed for a soft wearable elbow assistance exoskeleton with compliant tendon-sheath actuator. A comprehensive overview for the major components of the soft exoskeleton is introduced. The locations of anchor points are optimized via the maximum-stiffness principle. The NNETEC strategy is developed by fusing the feedback signals from surface electromyography (sEMG) sensors, inertial measurement units, force sensors, and motor encoder. It consists of a joint torque estimation module to identify the elbow torque of wearer based on Kalman filter, a neural-network adjustment module to recognize human motion intention, and a proportional-integral-derivative controller with hybrid position/torque feedbacks. Further experimental investigations are carried out by five volunteers to validate the effectiveness of the proposed soft elbow exoskeleton and control strategy. The results of the dumbbell-lifting experiments with various weights and frequencies demonstrate that, when compared with the proportional control strategy and the sEMG-based assistive control strategy without neural-network adjustment, the developed NNETEC method can achieve higher power assistance efficiency.

A compact-sized surface EMG sensor for myoelectric hand prosthesis.

Myoelectric prosthesis requires a sensor that can reliably capture surface electromyography (sEMG) signal from amputees for its controlled operation. The main problems with the presently available EMG devices are their extremely high cost, large response time, noise susceptibility, less amplitude sensitivity, and larger size. This paper proposes a compact and affordable EMG sensor for the prosthetic application. The sensor consists of an electrode interface, signal conditioning unit, and power supply unit all encased in a single package. The performance of dry electrodes employed in the skin interface was compared with the conventional Ag/AgCl electrodes, and the results were found satisfactory. The envelope detection technique in the sensor based on the tuned RC parameters enables the generation of smooth, faster, and repeatable EMG envelope irrespective of signal strength and subject variability. The output performance of the developed sensor was compared with commercial EMG sensor regarding signal-to-noise ratio, sensitivity, and response time. To perform this, EMG data with both devices were recorded for 10 subjects (3 amputees and 7 healthy subjects). The results showed 1.4 times greater SNR values and 45% higher sensitivity of the developed sensor than the commercial EMG sensor. Also, the proposed sensor was 57% faster than the commercial sensor in producing the output response. The sEMG sensor was further tested on amputees to control the operation of a self-designed 3D printed prosthetic hand. With proportional control scheme, the myoelectric hand setup was able to provide quicker and delicate grasping of objects as per the strength of the EMG signal.

A Comparative Study of Different Capacitor Voltage Control Design Strategies for Z-Source Inverter

The Z-source inverter (ZSI) is a prominent single-stage power conversion topology compared to traditional voltage source inverter (VSI)/ current source inverter (CSI). It adds the additional buck–boost capability to input voltage with improved reliability. However, the non-minimum phase (NMP) behavior is the major disadvantage of ZSI due to the existence of the right half plane (RHP) zero in the converter transfer functions. The existences of RHP zero destabilize the wideband feedback loops, which imply high gain instability and introduce the constraints on controller design. This paper presents different types of controllers and its design to maintain the required capacitor voltage with better transient response for non-minimum phase ZSI. Different tuning algorithms have been considered for both proportional–integral (PI), and integral–proportional (IP) control schemes. Also, the unified control algorithm has been implemented with both simple boost pulse width modulation (SBPWM) and a modified space vector pulse width modulation (MSVPWM) schemes to obtain the required capacitor voltage. The converter performance is comprehensively analyzed for different controllers and observations are tabulated. The complete analysis has been carried out using the MATLAB/Simulink environment for the proposed models.

Design and Control of Unidirectional DC–DC Modular Multilevel Converter for Offshore DC Collection Point: Theoretical Analysis and Experimental Validation

This paper presents the design and control of an advanced unidirectional dc–dc modular multilevel converter (MMC), which enables the integration of off-shore windfarms with the high-voltage direct current (HVdc) transmission system. The proposed converter consists of a single-phase MMC inverter, coupled with series-connected rectifier modules through a medium frequency transformer of multiple secondary windings. The modularity feature of the proposed converter enables scalability for different voltage levels. In addition to the galvanic isolation, the transformer also provides stepping gain to the output voltage. The proposed converter shows superior performance in terms of efficiency, losses, and devices utilization, when compared with the most competitive unidirectional cascaded dc–dc converters such as input series output series and input parallel output series. Furthermore, unlike the conventional d-q control method, which involves multiple transformations, this paper employs a simple proportional resonant control strategy that directly acts on the ac output of the MMC, under the stationary reference frame. The analytical design along with the simulation and experimentally validated results, confirmed the excellent performance of the proposed converter.