Purpose:The aim of this study was to summarize the evidence regarding whether pain reduction in individuals with chronic non-specific low back pain(CNSLBP)following conservative interventions is related to correspondi...Purpose:The aim of this study was to summarize the evidence regarding whether pain reduction in individuals with chronic non-specific low back pain(CNSLBP)following conservative interventions is related to corresponding improvements in balance control.Methods:Randomized controlled trials were identified from 5 databases(MEDLINE,Cochrane Library,Embase,Web of Science,and PsycINFO).Two reviewers independently screened and identified relevant studies that investigated the effects of non-surgical or non-pharmacological CNSLBP treatments on both pain intensity and balance control.Meta-regression analyses were performed to establish the associations between post-treatment changes in these 2 variables.Results:Thirty one studies involving 1280 participants with CNSLBP were included.Moderate-quality evidence suggested that pain reduction was associated with and explained 34%-45%of decreases in body sway,as measured by center-of-pressure(CoP)area and CoP velocity with eyes open.However,no significant association was observed between pain reduction and CoP area or velocity in anteroposterior/mediolateral directions.Similarly,there was no significant association between pain reduction and CoP distance or radius.Low-quality evidence indicated that pain relief explained a 15%improvement in one-leg stance with eyes open but not in the eyes-closed condition.Additionally,very low-quality evidence suggested that pain relief explained a 44%decrease in the static anteroposterior stability index with eyes closed but not in the eyes-open,mediolateral,or overall conditions.Furthermore,low-quality evidence indicated that reduced pain was associated with and accounted for 25%-43%of the improved composite and posteromedial scores of the star-excursion balance test,rather than the anterior and posterolateral scores.Conclusion:Depending on the type of balance assessment,pain relief following conservative interventions may slightly to moderately enhance balance control in individuals with CNSLBP.Clinicians should pay close attention to the balance control in patients with CNSLBP,particularly among older adults.展开更多
The cascaded H-bridge(CHB)multilevel inverter has become one of the most widely used PV inverter topologies due to its high voltage processing capability and high quality output power.Grid-connected PV system due to e...The cascaded H-bridge(CHB)multilevel inverter has become one of the most widely used PV inverter topologies due to its high voltage processing capability and high quality output power.Grid-connected PV system due to external conditions such as PV panel shading,PV component damage,can lead to PV output power imbalance,triggering the system over-modulation phenomenon,which in turn leads to grid-connected current waveform distortion.To this end,an improved power balance control strategy is proposed in this paper.Firstly,according to the different modulation ratios of each H-bridge module,a suitable harmonic injection method is used to keep the peak value of the modulating waveform always at 1;then an inverse triangular trapezoidal waveform is injected to optimize the modulating waveform,which further improves the output voltage waveform,reduces the THD value of the grid-connected currents,and maintains the stability of power inside the CHB system.Purpose.Simulation verifies the effectiveness and feasibility of this power balance control strategy.展开更多
It is well known that balance control is affected by aging,neurological and orthopedic conditions.Poor balance control during gait and postural maintenance are associated with disability,falls and increased mortality....It is well known that balance control is affected by aging,neurological and orthopedic conditions.Poor balance control during gait and postural maintenance are associated with disability,falls and increased mortality.Gait initiation-the transient period between the quiet standing posture and steady state walking-is a functional task that is classically used in the literature to investigate how the central nervous system(CNS)controls balance during a whole-body movement involving change in the base of support dimensions and center of mass progression.Understanding how the CNS in able-bodied subjects exerts this control during such a challenging task is a prerequisite to identifying motor disorders in populations with specific impairments of the postural system.It may also provide clinicians with objective measures to assess the efficiency of rehabilitation programs and better target interventions according to individual impairments.The present review thus proposes a state-of-the-art analysis on:(1)the balance control mechanisms in play during gait initiation in able bodied subjects and in the case of some frail populations;and(2)the biomechanical parameters used in the literature to quantify dynamic stability during gait initiation.Balance control mechanisms reviewed in this article included anticipatory postural adjustments,stance leg stiffness,foot placement,lateral ankle strategy,swing foot strike pattern and vertical center of mass braking.Based on this review,the following viewpoints were put forward:(1)dynamic stability during gait initiation may share a principle of homeostatic regulation similar to most physiological variables,where separate mechanisms need to be coordinated to ensure stabilization of vital variables,and consequently;and(2)rehabilitation interventions which focus on separate or isolated components of posture,balance,or gait may limit the effectiveness of current clinical practices.展开更多
This study mainly concerns a motion model and the main control algorithm of two-wheel self-balancing vehicle models.Details of the critical parameters fetching and output value of two-wheel self-balancing vehicle mode...This study mainly concerns a motion model and the main control algorithm of two-wheel self-balancing vehicle models.Details of the critical parameters fetching and output value of two-wheel self-balancing vehicle models are introduced,including those concerning balance control,speed control and direction control.An improved cascade coupling control scheme is proposed for two-wheel vehicles,based on a proportional-integral-derivative(PID)control algorithm.Moreover,a thorough comparison between a classic control system and the improved system is provided,and all aspects thereof are analyzed.It is determined that the control performance of the two-wheel self-balancing vehicle system based on the PID control algorithm is reliable,enabling the vehicle body to maintain balance while moving smoothly along a road at a fast average speed with better practical per-formance.展开更多
A new modulation approach was presented for the control of neutral-point （NP） voltage variation in the three-level NP-clamped voltage source inverter, and the average NP current model was established based on vector...A new modulation approach was presented for the control of neutral-point （NP） voltage variation in the three-level NP-clamped voltage source inverter, and the average NP current model was established based on vector diagram partition. Thus, theory base was built for balancing control of NP potential. Theoretical analysis and experimental results indicate that the proposed method for NP balancing control vector synthe- sizing concept based can make the average NP current zero, and do not influence NP potential within every sample period. The effectiveness of proposed research approach was verified by simulative and experimental results.展开更多
Partial pressure, system vibration and asymmetric system dynamic performance exit in asymmetric cylinder controller by symmetric valve hydraulic system. To solve this problem in the force control system, model referen...Partial pressure, system vibration and asymmetric system dynamic performance exit in asymmetric cylinder controller by symmetric valve hydraulic system. To solve this problem in the force control system, model reference adaptive controller is designed using equilibrium point stability theory and output error equation polynomial. The reference model is selected in such a way that it meets the system dynamic performance. Hardware configuration of asymmetric cylinder controlled by asymmetric valve hydraulic system is replaced by intelligent control algorithm, thus the cost is lowered and easy to application. Simulation results demonstrate that the proposed adaptive control sheme has good adaptive ability and well solves asymmetric dynamic performance problem. The designed adaptive controller is fairly robust to load disturbance and system parameter variation.展开更多
Concussion,or mild traumatic brain injury,incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom.The purpose of this review is to provide an overview of the linear and non-lin...Concussion,or mild traumatic brain injury,incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom.The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control.The current acute evaluation for concussion utilizes the subjective balance error scoring system(BESS) to assess postural control.While the sensitivity of the overall test battery is high,the sensitivity of the BESS is unacceptably low and,with repeat administration,is unable to accurately identify recovery.Sophisticated measures of postural control,utilizing traditional linear assessments,have identified impairments in postural control well beyond BESS recovery.Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion.Recently,the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy(Ap En).Ap En,most commonly in the medial-lateral plane,has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values;unfortunately these studies have not gone beyond the acute phase of recovery.One study has identified lingering deficits in postural control,utilizing Shannon and Renyi entropy metrics,which persist at least through clinical recovery and return to participation.Finally,limited evidence from two studies suggest that individuals with a previous history of a single concussion,even months or years prior,may display altered Ap En metrics.Overall,non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.展开更多
A new control algorithm is presented for digitally controlled dc-dc converters to achieve a fast response under a successive load-change.Under the steady-state condition,the tight voltage regulation is processed by th...A new control algorithm is presented for digitally controlled dc-dc converters to achieve a fast response under a successive load-change.Under the steady-state condition,the tight voltage regulation is processed by the conventional digital PID compensator.If the load disturbance is significant,the controller switches to an optimal control scheme.With the integration of the capacitor current,the proposed algorithm predicts the optimal switch over time based on the charge balance control,and the minimal voltage derivation and recovery time are thus achieved when the load current has a successive load-change.The method for calculating the optimal switch over time is described,and the implementation of the proposed algorithm with a digital controller is treated in detail.Furthermore,the simulation and experiment results are provided to validate the effectiveness of the approaches.展开更多
A biped walking robot should be able to keep balance even in the presence of disturbing forces. This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method...A biped walking robot should be able to keep balance even in the presence of disturbing forces. This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method. The called ＂step strategy＂ can be modeled by means of the reaction null space method that introduced earlier to tackle dynamic interaction problems of free-floating robots, or moving base robots in general. 6-DOF biped robot model simulations are used to confirm the validity.展开更多
This paper discusses about balancing control of unicycle robot.Unicycle robot consists of pitch which acts like inverted pendulum and roll which acts like reaction wheel pendulum.The robot which does not have actuator...This paper discusses about balancing control of unicycle robot.Unicycle robot consists of pitch which acts like inverted pendulum and roll which acts like reaction wheel pendulum.The robot which does not have actuator located in yaw axis is made to derive the simple dynamics.Lagrange equation is applied to deriving dynamic equations.Obtained dynamic equations are used to design the sliding mode control.State variables of the designed control are pitch angle and roll angle.Sliding mode control has chattering problem,which is eliminated by using the sigmoid function as switching function.Finally the control performance and eliminated chattering problem is verified by simulation.展开更多
A comprehensive predictive strategy was proposed for the neutral-point balancing control of back-to-back three-level converters. The phase currents at both sides and the DC-link capacitor voltages were measured for th...A comprehensive predictive strategy was proposed for the neutral-point balancing control of back-to-back three-level converters. The phase currents at both sides and the DC-link capacitor voltages were measured for the prediction of the neutral-point current. A quality function was found to balance the neutral-point, and a metabolic on-times distribution factor was used as a predicator to minimize the quality function at each switching state. Simulation results show that the proposed method produces smaller ripples in tested signals compared with the established one, namely, 9.15% less in a total harmonic distortion(THD) of line-to-line voltage, 1.08% less in the THD of phase current, and 0.9 V less in the ripple of the neutral-point voltage. The obtained experimental results show that the main harmonics of the line-to-line voltage and the phase current in the proposed method are improved by 10 d B and 6 d B, respectively, and the ripple of neutral-point voltage is halved compared to the established one.展开更多
Objective:To systematically evaluate the intervention effect of virtual reality technology on patients recovering from traumatic brain injury.Methods:The computer retrieved CNKI,VIP,Wan Fang,Embase,The Cochrane Librar...Objective:To systematically evaluate the intervention effect of virtual reality technology on patients recovering from traumatic brain injury.Methods:The computer retrieved CNKI,VIP,Wan Fang,Embase,The Cochrane Library and PubMed database,and collected randomized controlled trials of virtual reality technology combined with routine rehabilitation training and simple routine rehabilitation training on patients recovering from traumatic brain injury.The retrieval period was from the establishment of the database to July 2019.Two researchers independently screened the literature,extracted the data and evaluated the risk of bias in the included studies.RevMan 5.3 software was used for analysis.Results:A total of 7 articles were included.Meta-analysis results showed that virtual reality technology could significantly improve balance function(mean difference(MD)=3.72,95%confidence interval(CI)(2.61,4.83),P<0.001),daily living ability(MD=11.87,95%CI(10.42,13.32),P<0.001),and exercise ability(MD=3.83,95%CI(2.30,5.36),P<0.001).In the aspect of posture control ability,the trajectory motion length,trajectory velocity and peripheral area were improved(standardised mean difference(SMD)=0.80,95%CI(1.19,0.41),P<0.0001),(SMD=0.95,95%CI(1.45,0.45),P=0.0002),(SMD=0.69,95%CI(1.11,0.26),P=0.001).Conclusion:Virtual reality technology can significantly improve the balance function,daily living ability,motor function and postural control ability of patients recovering from cerebral trauma.Limited by the quantity and quality of the included studies,the above conclusions need to be verified by more high-quality studies.展开更多
Modular multilevel converter (MMC) based fault ride through (FRT) control is a promising solution to deal with the pole-to-ground (PTG) fault in high voltage direct current (HVDC) system. However, when MMC switches to...Modular multilevel converter (MMC) based fault ride through (FRT) control is a promising solution to deal with the pole-to-ground (PTG) fault in high voltage direct current (HVDC) system. However, when MMC switches to the FRT control, capacitor voltage imbalance between upper and lower arms will occur, resulting in the deterioration of FRT performance. This letter provides a comprehensive analysis for the imbalance issue from the perspective of fundamental frequency circulating current (FFCC). It is found the imbalance during FRT stage will not expand continuously, but converge to a certain value gradually. The specific imbalance degree is closely associated with the amplitude of FFCC. In order to solve the imbalance issue, an open-loop balancing control is proposed. By introducing a fundamental frequency feedforward item to the inherent circulating current control, the proposed method can not only balance the capacitor voltages, but also minimize the amplitude of FFCC, and consequently the power loss of MMC during FRT process can be reduced. Finally, simulation results of PSCAD/ EMTDC verify the validity of theoretical analysis.展开更多
The modular multilevel matrix converter(M3C)is a potential frequency converter for low-frequency AC transmission.However,capacitor voltage control of high-voltage and largecapacity M3C is more difficult,especially for...The modular multilevel matrix converter(M3C)is a potential frequency converter for low-frequency AC transmission.However,capacitor voltage control of high-voltage and largecapacity M3C is more difficult,especially for voltage balancing between branches.To solve this problem,this paper defines sequence circulating components and theoretically analyzes the influence mechanism of different sequence circulating components on branch capacitor voltage.A fully decoupled branch energy balancing control method based on four groups of sequence circulating components is proposed.This method can control capacitor voltages of nine branches in horizontal,vertical and diagonal directions.Considering influences of both circulating current and voltage,a cross decoupled control is designed to improve control precision.Simulation results are taken from a low-frequency transmission system based on PSCAD/EMTDC,and effectiveness and precision of the proposed branch energy balancing control method are verified in the case of nonuniform parameters and an unbalanced power system.展开更多
The cluster DC voltage balancing control adopting zero-sequence voltage injection is appropriate for the starconnected cascaded H-bridge STATCOM because no zerosequence currents are generated in the three-phase three-...The cluster DC voltage balancing control adopting zero-sequence voltage injection is appropriate for the starconnected cascaded H-bridge STATCOM because no zerosequence currents are generated in the three-phase three-wire system.However,as the zero-sequence voltage is expressed in trigonometric form,traditional control methods involve many complicated operations,such as the square-root,trigonometric operations,and inverse tangent operations.To simplify cluster voltage balancing control,this paper converts the zero-sequence voltage to the dq frame in a DC representation by introducing a virtually orthogonal variable,and the DC components of the zero-sequence voltage in the dq frame are regulated linearly by proportional integral regulators,rather than being calculated from uneven active powers in traditional controls.This removes all complicated operations.Finally,this paper presents simulation and experimental results for a 400 V±7.5 kvar star-connected STATCOM,in balanced and unbalanced scenarios,thereby verifying the effectiveness of the proposed control.展开更多
Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(...Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(SVPWM)is a more popular scheme,but conventional 4L SVPWM cannot achieve the voltage balancing control of DC-link capacitors,is complex to implement,and requires costly computation.A hybrid modulation method with capacitor voltage-balancing control for 4L NPC converters is proposed.The proposed method is achieved using three-level(3L)SVPWM and two-level(2L)carrier-based pulse-width modulation(CPWM)based on the concept of"4L=3L+2L".Thus,it can be easily implemented on a digital chip because the modulation process is nearly identical to that of 3L SVPWM without the more cumbersome 4L SVPWM algorithm.Meanwhile,any proven optimization scheme of 3L SVPWM can be directly applied to the proposed method to further improve performance.Simulation and experimental results for a 4L active NPC converter demonstrate the effectiveness of the proposed method.展开更多
A quadruped robot with a manipulator that combines dynamic motion and manipulation capabilities will greatly expand its application scenarios.However,the addition of the manipulator raises the center of mass of the qu...A quadruped robot with a manipulator that combines dynamic motion and manipulation capabilities will greatly expand its application scenarios.However,the addition of the manipulator raises the center of mass of the quadruped robot,increasing complexity in motion control and posing new challenges for maintaining balance on sloped terrains.To address this,a balance control method based on whole-body synergy is proposed in this study,emphasizing adaptive adjustment of the robot system’s overall balance through effective utilization of the manipulator’s active motion.By establishing a mapping relationship between the manipulator and the robot’s attitude angle under system equilibrium,the desired manipulator motion is guided by real-time estimates of terrain angles during motion,enhancing motion efficiency while ensuring robot balance.Furthermore,to enhance motion tracking accuracy,the optimization of system angular momentum and manipulator manipulability is incorporated into hierarchical optimization tasks,improving manipulator controllability and overall system performance.Simulation and experimental results demonstrate that the quadruped robot with a manipulator exhibits reduced velocity and attitude angle fluctuations,as well as smoother foot-end force dynamics during climbing motions with the addition of manipulator adaptive adjustment.These results validate the effectiveness and superiority of the manipulator-based adaptive adjustment strategy proposed in this paper.展开更多
When humanoid robots attempt to walk on terrain such as shaking platforms,time-varying disturbances are introduced to the support foot.These abrupt changes of inclination angle can cause the robot to lose balance upon...When humanoid robots attempt to walk on terrain such as shaking platforms,time-varying disturbances are introduced to the support foot.These abrupt changes of inclination angle can cause the robot to lose balance upon landing,presenting significant challenges for balance control algorithms.To address this issue,we propose a novel divergent component of motion(DCM)-based time-varying disturbance walking(DCM-TVDW)method.This method allows the robot to walk on rugged surfaces and helps to maintain dynamic balance when subjected to large time-varying disturbances.In the DCM-TVDW control method,we first adjust the robot's center of mass and stride height to adapt to transitions between different terrain types via a variable height stabilization method,and hold these quantities constant as base values.We then combine DCM with the N-step capturability strategy.This combination allows for dynamic balance through multi-step adjustments from the initially unstable region,thereby extending the robots stability boundary.Simulation and experimental results demonstrate that the DCM-TVDW method enables the SJ-Bruce robot to traverse a dynamically shaking platform with an inclination angle of approximately 22°.展开更多
Large-scale renewable energy transmission via thevoltage source converter (VSC) based high-voltage direct current(HVDC) is a crucial development direction for constructing anew-typed power system in China. However, re...Large-scale renewable energy transmission via thevoltage source converter (VSC) based high-voltage direct current(HVDC) is a crucial development direction for constructing anew-typed power system in China. However, renewable energy ischaracterized by volatility, intermittency, and randomness. Whenthe sending-end modular multilevel converter (MMC) cannotadapt to the rapid fluctuations in renewable energy output, itsenergy balance will be disrupted by the active power differencebetween the AC and DC sides, causing issues such as widebandoscillations and exacerbated circulating currents. To solve theproblem mentioned above, a novel energy balance-based controlmethod for MMCs connected to wind farms is proposed in thispaper, enabling the MMC to effectively adapt to fluctuationsin renewable energy output and naturally maintain circulatingcurrent at a relatively low level. Firstly, the evolution principleillustrating topology decomposition and reconfiguration of theMMC is revealed. Secondly, the control method for AC internalvoltage is proposed, which combines the energy balance betweenthe half MMCs and voltage amplitude support. Thirdly, the DCinternal voltage is defined, and its control method is proposedbased on the MMC’s overall energy balance. Then, independentcontrol of each bridge arm is achieved by integrating the energybalance of the bridge arms with both the AC and DC internalvoltages. Finally, an electromagnetic transient simulation modelis built with PSCAD/EMTDC, and the efficacy and practicalityof the proposed method are demonstrated through extensivesimulation experiments.展开更多
基金supported by GP Batteries Industrial Safety Trust Fund(Funding number:R-ZDDR).
文摘Purpose:The aim of this study was to summarize the evidence regarding whether pain reduction in individuals with chronic non-specific low back pain(CNSLBP)following conservative interventions is related to corresponding improvements in balance control.Methods:Randomized controlled trials were identified from 5 databases(MEDLINE,Cochrane Library,Embase,Web of Science,and PsycINFO).Two reviewers independently screened and identified relevant studies that investigated the effects of non-surgical or non-pharmacological CNSLBP treatments on both pain intensity and balance control.Meta-regression analyses were performed to establish the associations between post-treatment changes in these 2 variables.Results:Thirty one studies involving 1280 participants with CNSLBP were included.Moderate-quality evidence suggested that pain reduction was associated with and explained 34%-45%of decreases in body sway,as measured by center-of-pressure(CoP)area and CoP velocity with eyes open.However,no significant association was observed between pain reduction and CoP area or velocity in anteroposterior/mediolateral directions.Similarly,there was no significant association between pain reduction and CoP distance or radius.Low-quality evidence indicated that pain relief explained a 15%improvement in one-leg stance with eyes open but not in the eyes-closed condition.Additionally,very low-quality evidence suggested that pain relief explained a 44%decrease in the static anteroposterior stability index with eyes closed but not in the eyes-open,mediolateral,or overall conditions.Furthermore,low-quality evidence indicated that reduced pain was associated with and accounted for 25%-43%of the improved composite and posteromedial scores of the star-excursion balance test,rather than the anterior and posterolateral scores.Conclusion:Depending on the type of balance assessment,pain relief following conservative interventions may slightly to moderately enhance balance control in individuals with CNSLBP.Clinicians should pay close attention to the balance control in patients with CNSLBP,particularly among older adults.
基金supported by the National Natural Science Foundation of China,Regional Science Foundation Project,52367009,Study on Bow Net Dynamics Modeling and Coupling Smoothness of High speed AC Rigid Network in the Long Tunnel Section of Sichuan Tibet Railway.
文摘The cascaded H-bridge(CHB)multilevel inverter has become one of the most widely used PV inverter topologies due to its high voltage processing capability and high quality output power.Grid-connected PV system due to external conditions such as PV panel shading,PV component damage,can lead to PV output power imbalance,triggering the system over-modulation phenomenon,which in turn leads to grid-connected current waveform distortion.To this end,an improved power balance control strategy is proposed in this paper.Firstly,according to the different modulation ratios of each H-bridge module,a suitable harmonic injection method is used to keep the peak value of the modulating waveform always at 1;then an inverse triangular trapezoidal waveform is injected to optimize the modulating waveform,which further improves the output voltage waveform,reduces the THD value of the grid-connected currents,and maintains the stability of power inside the CHB system.Purpose.Simulation verifies the effectiveness and feasibility of this power balance control strategy.
文摘It is well known that balance control is affected by aging,neurological and orthopedic conditions.Poor balance control during gait and postural maintenance are associated with disability,falls and increased mortality.Gait initiation-the transient period between the quiet standing posture and steady state walking-is a functional task that is classically used in the literature to investigate how the central nervous system(CNS)controls balance during a whole-body movement involving change in the base of support dimensions and center of mass progression.Understanding how the CNS in able-bodied subjects exerts this control during such a challenging task is a prerequisite to identifying motor disorders in populations with specific impairments of the postural system.It may also provide clinicians with objective measures to assess the efficiency of rehabilitation programs and better target interventions according to individual impairments.The present review thus proposes a state-of-the-art analysis on:(1)the balance control mechanisms in play during gait initiation in able bodied subjects and in the case of some frail populations;and(2)the biomechanical parameters used in the literature to quantify dynamic stability during gait initiation.Balance control mechanisms reviewed in this article included anticipatory postural adjustments,stance leg stiffness,foot placement,lateral ankle strategy,swing foot strike pattern and vertical center of mass braking.Based on this review,the following viewpoints were put forward:(1)dynamic stability during gait initiation may share a principle of homeostatic regulation similar to most physiological variables,where separate mechanisms need to be coordinated to ensure stabilization of vital variables,and consequently;and(2)rehabilitation interventions which focus on separate or isolated components of posture,balance,or gait may limit the effectiveness of current clinical practices.
文摘This study mainly concerns a motion model and the main control algorithm of two-wheel self-balancing vehicle models.Details of the critical parameters fetching and output value of two-wheel self-balancing vehicle models are introduced,including those concerning balance control,speed control and direction control.An improved cascade coupling control scheme is proposed for two-wheel vehicles,based on a proportional-integral-derivative(PID)control algorithm.Moreover,a thorough comparison between a classic control system and the improved system is provided,and all aspects thereof are analyzed.It is determined that the control performance of the two-wheel self-balancing vehicle system based on the PID control algorithm is reliable,enabling the vehicle body to maintain balance while moving smoothly along a road at a fast average speed with better practical per-formance.
文摘A new modulation approach was presented for the control of neutral-point （NP） voltage variation in the three-level NP-clamped voltage source inverter, and the average NP current model was established based on vector diagram partition. Thus, theory base was built for balancing control of NP potential. Theoretical analysis and experimental results indicate that the proposed method for NP balancing control vector synthe- sizing concept based can make the average NP current zero, and do not influence NP potential within every sample period. The effectiveness of proposed research approach was verified by simulative and experimental results.
文摘Partial pressure, system vibration and asymmetric system dynamic performance exit in asymmetric cylinder controller by symmetric valve hydraulic system. To solve this problem in the force control system, model reference adaptive controller is designed using equilibrium point stability theory and output error equation polynomial. The reference model is selected in such a way that it meets the system dynamic performance. Hardware configuration of asymmetric cylinder controlled by asymmetric valve hydraulic system is replaced by intelligent control algorithm, thus the cost is lowered and easy to application. Simulation results demonstrate that the proposed adaptive control sheme has good adaptive ability and well solves asymmetric dynamic performance problem. The designed adaptive controller is fairly robust to load disturbance and system parameter variation.
文摘Concussion,or mild traumatic brain injury,incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom.The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control.The current acute evaluation for concussion utilizes the subjective balance error scoring system(BESS) to assess postural control.While the sensitivity of the overall test battery is high,the sensitivity of the BESS is unacceptably low and,with repeat administration,is unable to accurately identify recovery.Sophisticated measures of postural control,utilizing traditional linear assessments,have identified impairments in postural control well beyond BESS recovery.Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion.Recently,the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy(Ap En).Ap En,most commonly in the medial-lateral plane,has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values;unfortunately these studies have not gone beyond the acute phase of recovery.One study has identified lingering deficits in postural control,utilizing Shannon and Renyi entropy metrics,which persist at least through clinical recovery and return to participation.Finally,limited evidence from two studies suggest that individuals with a previous history of a single concussion,even months or years prior,may display altered Ap En metrics.Overall,non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.
基金Supported by the National Natural Science Foundation of China(51207001)the Anhui Provincial Natural Science Foundation(1308085ME66)
文摘A new control algorithm is presented for digitally controlled dc-dc converters to achieve a fast response under a successive load-change.Under the steady-state condition,the tight voltage regulation is processed by the conventional digital PID compensator.If the load disturbance is significant,the controller switches to an optimal control scheme.With the integration of the capacitor current,the proposed algorithm predicts the optimal switch over time based on the charge balance control,and the minimal voltage derivation and recovery time are thus achieved when the load current has a successive load-change.The method for calculating the optimal switch over time is described,and the implementation of the proposed algorithm with a digital controller is treated in detail.Furthermore,the simulation and experiment results are provided to validate the effectiveness of the approaches.
基金supported by the National Natural Science Foundation of China (No.50675016)the Science and Technology Innovation Fund for the Doctor (No.48030)
文摘A biped walking robot should be able to keep balance even in the presence of disturbing forces. This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method. The called ＂step strategy＂ can be modeled by means of the reaction null space method that introduced earlier to tackle dynamic interaction problems of free-floating robots, or moving base robots in general. 6-DOF biped robot model simulations are used to confirm the validity.
基金The MKE(The Ministry of Knowledge Economy),Korea,under the ITRC(Infor mation Technology Research Center)support program supervised by the NIPA(National IT Industry Promotion Agency)(NIPA-2012-H0301-12-2006)the MKE,Korea,under the Human Resources Development Programfor Specialized Environment Navigation/Localization Technology Research Center support program supervised by the NIPA(NIPA-2012-H1502-12-1002)
文摘This paper discusses about balancing control of unicycle robot.Unicycle robot consists of pitch which acts like inverted pendulum and roll which acts like reaction wheel pendulum.The robot which does not have actuator located in yaw axis is made to derive the simple dynamics.Lagrange equation is applied to deriving dynamic equations.Obtained dynamic equations are used to design the sliding mode control.State variables of the designed control are pitch angle and roll angle.Sliding mode control has chattering problem,which is eliminated by using the sigmoid function as switching function.Finally the control performance and eliminated chattering problem is verified by simulation.
基金Project(61074018)supported by the National Natural Science Foundation of ChinaProject(2012kfjj06)supported by Hunan Province Key Laboratory of Smart Grids Operation and Control(Changsha University of Science and Technology),China
文摘A comprehensive predictive strategy was proposed for the neutral-point balancing control of back-to-back three-level converters. The phase currents at both sides and the DC-link capacitor voltages were measured for the prediction of the neutral-point current. A quality function was found to balance the neutral-point, and a metabolic on-times distribution factor was used as a predicator to minimize the quality function at each switching state. Simulation results show that the proposed method produces smaller ripples in tested signals compared with the established one, namely, 9.15% less in a total harmonic distortion(THD) of line-to-line voltage, 1.08% less in the THD of phase current, and 0.9 V less in the ripple of the neutral-point voltage. The obtained experimental results show that the main harmonics of the line-to-line voltage and the phase current in the proposed method are improved by 10 d B and 6 d B, respectively, and the ripple of neutral-point voltage is halved compared to the established one.
文摘Objective:To systematically evaluate the intervention effect of virtual reality technology on patients recovering from traumatic brain injury.Methods:The computer retrieved CNKI,VIP,Wan Fang,Embase,The Cochrane Library and PubMed database,and collected randomized controlled trials of virtual reality technology combined with routine rehabilitation training and simple routine rehabilitation training on patients recovering from traumatic brain injury.The retrieval period was from the establishment of the database to July 2019.Two researchers independently screened the literature,extracted the data and evaluated the risk of bias in the included studies.RevMan 5.3 software was used for analysis.Results:A total of 7 articles were included.Meta-analysis results showed that virtual reality technology could significantly improve balance function(mean difference(MD)=3.72,95%confidence interval(CI)(2.61,4.83),P<0.001),daily living ability(MD=11.87,95%CI(10.42,13.32),P<0.001),and exercise ability(MD=3.83,95%CI(2.30,5.36),P<0.001).In the aspect of posture control ability,the trajectory motion length,trajectory velocity and peripheral area were improved(standardised mean difference(SMD)=0.80,95%CI(1.19,0.41),P<0.0001),(SMD=0.95,95%CI(1.45,0.45),P=0.0002),(SMD=0.69,95%CI(1.11,0.26),P=0.001).Conclusion:Virtual reality technology can significantly improve the balance function,daily living ability,motor function and postural control ability of patients recovering from cerebral trauma.Limited by the quantity and quality of the included studies,the above conclusions need to be verified by more high-quality studies.
基金supported by Zhejiang Province Natural Science Foundation of China under Grant LQ22E070002Shandong Province Natural Science Foundation of China under Grant ZR2020QE215.
文摘Modular multilevel converter (MMC) based fault ride through (FRT) control is a promising solution to deal with the pole-to-ground (PTG) fault in high voltage direct current (HVDC) system. However, when MMC switches to the FRT control, capacitor voltage imbalance between upper and lower arms will occur, resulting in the deterioration of FRT performance. This letter provides a comprehensive analysis for the imbalance issue from the perspective of fundamental frequency circulating current (FFCC). It is found the imbalance during FRT stage will not expand continuously, but converge to a certain value gradually. The specific imbalance degree is closely associated with the amplitude of FFCC. In order to solve the imbalance issue, an open-loop balancing control is proposed. By introducing a fundamental frequency feedforward item to the inherent circulating current control, the proposed method can not only balance the capacitor voltages, but also minimize the amplitude of FFCC, and consequently the power loss of MMC during FRT process can be reduced. Finally, simulation results of PSCAD/ EMTDC verify the validity of theoretical analysis.
基金supported by National Key R&D Program of China(No.2021YFB2401100).
文摘The modular multilevel matrix converter(M3C)is a potential frequency converter for low-frequency AC transmission.However,capacitor voltage control of high-voltage and largecapacity M3C is more difficult,especially for voltage balancing between branches.To solve this problem,this paper defines sequence circulating components and theoretically analyzes the influence mechanism of different sequence circulating components on branch capacitor voltage.A fully decoupled branch energy balancing control method based on four groups of sequence circulating components is proposed.This method can control capacitor voltages of nine branches in horizontal,vertical and diagonal directions.Considering influences of both circulating current and voltage,a cross decoupled control is designed to improve control precision.Simulation results are taken from a low-frequency transmission system based on PSCAD/EMTDC,and effectiveness and precision of the proposed branch energy balancing control method are verified in the case of nonuniform parameters and an unbalanced power system.
基金supported by National Key R&D Program of China(No.2021YFB2401100)the Science and Technology Project of State Grid Corporation of China(No.5211DS22002C).
文摘The cluster DC voltage balancing control adopting zero-sequence voltage injection is appropriate for the starconnected cascaded H-bridge STATCOM because no zerosequence currents are generated in the three-phase three-wire system.However,as the zero-sequence voltage is expressed in trigonometric form,traditional control methods involve many complicated operations,such as the square-root,trigonometric operations,and inverse tangent operations.To simplify cluster voltage balancing control,this paper converts the zero-sequence voltage to the dq frame in a DC representation by introducing a virtually orthogonal variable,and the DC components of the zero-sequence voltage in the dq frame are regulated linearly by proportional integral regulators,rather than being calculated from uneven active powers in traditional controls.This removes all complicated operations.Finally,this paper presents simulation and experimental results for a 400 V±7.5 kvar star-connected STATCOM,in balanced and unbalanced scenarios,thereby verifying the effectiveness of the proposed control.
基金Supported in part by the Guangdong Innovative Program on New Power System Technology under Grant 1688483408285in part by the National Natural Science Foundation of China under Grant 52207221in part by Wuhan Science and Technology Project under Grant 2023010201010071.
文摘Capacitor voltage imbalance in four-level(4L)neutral-point clamped(NPC)converters is a direct factor hindering their application.In particular,when they are applied in motor drives,space vector pulse-width modulation(SVPWM)is a more popular scheme,but conventional 4L SVPWM cannot achieve the voltage balancing control of DC-link capacitors,is complex to implement,and requires costly computation.A hybrid modulation method with capacitor voltage-balancing control for 4L NPC converters is proposed.The proposed method is achieved using three-level(3L)SVPWM and two-level(2L)carrier-based pulse-width modulation(CPWM)based on the concept of"4L=3L+2L".Thus,it can be easily implemented on a digital chip because the modulation process is nearly identical to that of 3L SVPWM without the more cumbersome 4L SVPWM algorithm.Meanwhile,any proven optimization scheme of 3L SVPWM can be directly applied to the proposed method to further improve performance.Simulation and experimental results for a 4L active NPC converter demonstrate the effectiveness of the proposed method.
基金supported by the Gansu Youth Science and Technology Fund(24JRRA189).
文摘A quadruped robot with a manipulator that combines dynamic motion and manipulation capabilities will greatly expand its application scenarios.However,the addition of the manipulator raises the center of mass of the quadruped robot,increasing complexity in motion control and posing new challenges for maintaining balance on sloped terrains.To address this,a balance control method based on whole-body synergy is proposed in this study,emphasizing adaptive adjustment of the robot system’s overall balance through effective utilization of the manipulator’s active motion.By establishing a mapping relationship between the manipulator and the robot’s attitude angle under system equilibrium,the desired manipulator motion is guided by real-time estimates of terrain angles during motion,enhancing motion efficiency while ensuring robot balance.Furthermore,to enhance motion tracking accuracy,the optimization of system angular momentum and manipulator manipulability is incorporated into hierarchical optimization tasks,improving manipulator controllability and overall system performance.Simulation and experimental results demonstrate that the quadruped robot with a manipulator exhibits reduced velocity and attitude angle fluctuations,as well as smoother foot-end force dynamics during climbing motions with the addition of manipulator adaptive adjustment.These results validate the effectiveness and superiority of the manipulator-based adaptive adjustment strategy proposed in this paper.
基金supported by Jiangsu Provincial Science and Technology Department Program Special Funds(Basic Research on Frontier Leading Technologies)Project(Grant No.BK20232031)。
文摘When humanoid robots attempt to walk on terrain such as shaking platforms,time-varying disturbances are introduced to the support foot.These abrupt changes of inclination angle can cause the robot to lose balance upon landing,presenting significant challenges for balance control algorithms.To address this issue,we propose a novel divergent component of motion(DCM)-based time-varying disturbance walking(DCM-TVDW)method.This method allows the robot to walk on rugged surfaces and helps to maintain dynamic balance when subjected to large time-varying disturbances.In the DCM-TVDW control method,we first adjust the robot's center of mass and stride height to adapt to transitions between different terrain types via a variable height stabilization method,and hold these quantities constant as base values.We then combine DCM with the N-step capturability strategy.This combination allows for dynamic balance through multi-step adjustments from the initially unstable region,thereby extending the robots stability boundary.Simulation and experimental results demonstrate that the DCM-TVDW method enables the SJ-Bruce robot to traverse a dynamically shaking platform with an inclination angle of approximately 22°.
基金supported by the National NaturalScience Foundation of China (No. 52277075), and Postgraduate ScientificResearch Innovation Project of Changsha University of Science & Technology(No. CSLGCX23062).
文摘Large-scale renewable energy transmission via thevoltage source converter (VSC) based high-voltage direct current(HVDC) is a crucial development direction for constructing anew-typed power system in China. However, renewable energy ischaracterized by volatility, intermittency, and randomness. Whenthe sending-end modular multilevel converter (MMC) cannotadapt to the rapid fluctuations in renewable energy output, itsenergy balance will be disrupted by the active power differencebetween the AC and DC sides, causing issues such as widebandoscillations and exacerbated circulating currents. To solve theproblem mentioned above, a novel energy balance-based controlmethod for MMCs connected to wind farms is proposed in thispaper, enabling the MMC to effectively adapt to fluctuationsin renewable energy output and naturally maintain circulatingcurrent at a relatively low level. Firstly, the evolution principleillustrating topology decomposition and reconfiguration of theMMC is revealed. Secondly, the control method for AC internalvoltage is proposed, which combines the energy balance betweenthe half MMCs and voltage amplitude support. Thirdly, the DCinternal voltage is defined, and its control method is proposedbased on the MMC’s overall energy balance. Then, independentcontrol of each bridge arm is achieved by integrating the energybalance of the bridge arms with both the AC and DC internalvoltages. Finally, an electromagnetic transient simulation modelis built with PSCAD/EMTDC, and the efficacy and practicalityof the proposed method are demonstrated through extensivesimulation experiments.
