Position Control Scheme Research Articles

Lack of Proprioceptive Strategy Modulation Leads to At-Risk Biomechanics for Anterior Cruciate Ligament in Healthy Athletes.

Anterior cruciate ligament (ACL) injuries are frequent in handball, and altered sensory integration may contribute to increased injury risk. Recent evidence showed that proprioceptive postural control strategies differ among athletes. The aim of this study was to evaluate the relationship between proprioceptive strategy and biomechanics during side-cutting maneuvers. A total of 47 handball players performed anticipated and unanticipated cutting tasks. Their postural proprioceptive strategy was then characterized according to the perturbation of the center of pressure displacement generated by the muscle vibration on a firm and foam surface. Individuals able to reweight proprioception from ankle to lumbar signals according to the stability of the support were defined as flexible. Conversely, athletes maintaining an ankle-steered strategy on foam surface were characterized as rigid. Statistical parametric mapping analysis was used to compare pelvic and lower limb side-cutting kinematics, kinetics, and EMG activity from seven muscles 200 ms before and after initial contact (IC) using a two-way ANOVA (group-condition). Twenty athletes (11 females and 9 males, 18.5 yr) were characterized as flexible and 20 athletes (12 females and 8 males, 18.9 yr) as rigid. No interaction between condition and proprioceptive profile was observed. More ipsilateral pelvic tilt before IC and lower vastus lateralis (VL) activity immediately after IC was observed during CUT ant . When comparing proprioceptive strategy, rigid individuals exhibited less preactivity of the semitendinosus ( P < 0.001) and higher VL activity ( P = 0.032). Conversely, rigid showed higher gluteus medius preactivity ( P < 0.05) and higher VL activity 100 ms after IC ( P < 0.001). Ankle was also more internally rotated before and during the stance phase ( P < 0.05) among rigid athletes. Rigid handball players exhibited at-risk determinants for anterior cruciate ligament injuries during side-cutting maneuvers.

Postural balance disorders in sarcopenia based on surface electromyography

BackgroundSarcopenia is an intrinsic factor that leads to balance disorders and falls in older adults. However, the characterization of sarcopenia-related postural balance deficits remains unclear. AimsThis study aimed to explore the balance performance and postural control strategy in older adults with sarcopenia during static stance tasks using force platforms and surface electromyography. MethodsOlder adults with right-sided dominance were recruited, including 27 adults with sarcopenia and 27 healthy counterparts. Postural sway was measured with eyes open/closed on rigid/compliant surfaces. The time- and frequency-domain indexes of bilateral lower extremity muscle activity were simultaneously recorded. ResultsThe postural sway and activity of multiple lower extremity muscles in the sarcopenia group were increased (P < 0.05). The amplitude contribution ratio of the right tibialis anterior muscle (larger in sarcopenia), co-contraction ratio of right ankle dorsiflexion (smaller in sarcopenia), and mean power frequency and median frequency of the left gluteus maximus muscle (smaller in sarcopenia) had main effects of grouping (P < 0.001, η2p = 0.06–0.10). All of them had discrimination for sarcopenia (area under the curve = 0.639–0.657, P < 0.001) and were correlated with balance function measurement in sarcopenia (|rs| = 0.22–0.44, P < 0.05). ConclusionThe results of this study suggest that older adults with sarcopenia have decreased balance function and increased cost of electrophysiology. They were found to prefer the postural strategy of dominant ankle dorsiflexion and demonstrated overactivity of the dominant tibialis anterior muscles and fatigue vulnerability of the nondominant gluteus maximus. Improvements in these postural features may have balance benefits.

Investigating the Effect of Addition of Cervical Proprioceptive Training to Conventional Physiotherapy on Visual, Vestibular and Proprioceptive Dependency of Postural Control in Patients with Chronic Non-Specific Neck Pain: A Randomized Controlled Clinical Trial.

While cervical proprioception deficit has been suggested as a contributing factor to clinical consequences of chronic non-specific neck pain (CNSNP), the effect of addressing such impairments on postural control strategies has remained unexplored. The aim of this study was to compare the response of the postural control system to alteration of sensory afferents in CNSNP with asymptomatic individuals. Furthermore, we examined whether proprioceptive training would yield superior outcomes to routine physiotherapy for improvement of postural control, pain and disability. Center of pressure (CoP) variables of sixty CNSNP patients equally distributed in any of the proprioception-specific or conventional physiotherapy groups and 30 asymptomatic participants were evaluated under four standing conditions:1) normal, 2) foam, 3) cervical extension/eyes open and 4) cervical extension/eyes closed standing. CoP anteroposterior range and anteroposterior and mediolateral velocity in patients were significantly higher than the control group under condition 2 (P<0.05). Patients also demonstrated lower anteroposterior lyapunov exponent under conditions 2 and 4 (P<0.05). Both interventions significantly decreased anteroposterior range and anteroposterior velocity(P<0.05). Anteroposterior lyapunov exponent also increased under condition 2 (P<0.05).. After the interventions, CoP anteroposterior range and anteroposterior velocity were significantly lower in the proprioceptive exercise group than the conventional physiotherapy group (P<0.05). Anteroposterior lyapunov exponent was also significantly higher in the proprioceptive exercise group (P<0.05).This while there was no significant difference between these patients and control group participants in any of the CoP variables after intervention. Our results rejected the hypothesis that impaired neck proprioception in the presence of CNSNP is compensated by overweighting other sources of sensory afferent information. The findings also revealed that while proprioceptive exercises successfully returned postural strategies of CNSNP patients to those in asymptomatic participants, they do not add to clinical recovery of these patients.

Temporal changes in postural control strategy through single-leg stance practice with active restriction of knee movement.

[Purpose] This study aimed to examine and verify temporal changes in lower limb joint action after 2 weeks of single-leg stance training under active restriction of knee movement. [Participants and Methods] The participants included 28 healthy adult females (mean age, 19.6 ± 1.0 years). A stabile meter was used to measure the center of pressure sway as an index of ankle joint action. In addition, a triaxial accelerometer was used to measure pelvic and knee sways as indices of hip and knee joint actions, respectively. We established two experimental groups: an active-restriction group and an unrestricted group. Measurements of lower limb joint actions were recorded thrice during single-leg stance exercises during the first session of practice, the third session 1 week later, and the sixth session 2 weeks later. [Results] Both groups exhibited shorter total trajectory lengths in sessions three and six than in the first session. The active restriction group showed less knee sway in later sessions, whereas the unrestricted group showed reduced pelvic sway in the third session. [Conclusion] Single-leg stance exercises with active restriction of knee movement may alter the strategy of lower limb joint action.

Predictor-Based Neural Attitude Control of A Quadrotor With Disturbances

An attitude control issue is concerned for a quadrotor with external disturbances in this paper. For unknown system dynamics, predictor-based neural networks (NNs) are introduced, where prediction errors, angular velocities, are constructed, instead of tracking errors, for updating NNs' weights. This replacement reduces the occurrence of high-frequency oscillations in NNs' approximation. With this improved NNs, a predictorbased NN disturbance observer is then developed for compensation for external disturbances and NNs' approximation errors, and a normalization learning technique is employed for reduction of the number of learning parameters. A predictor-based neural attitude control strategy is proposed for a quadrotor with external disturbances. Furthermore, measurement noise are taken into account in our predictor-based neural attitude control strategy. The Lyapunov-based stability analysis shows that all closed-loop signals in the designed attitude system are semiglobally bounded. A numerical simulation and a hardware-in-loop experiment as well as outdoor flight verify the effectiveness of the proposed anti-disturbance attitude control strategy.

Stroboscopic Goggles Impair Postural Control in Those With and Without Chronic Ankle Instability: A Critically Appraised Topic

Clinical Scenario: Ankle sprains are highly common and can lead to chronic ankle instability (CAI). Individuals with CAI have a variety of sensorimotor impairments including poor postural control and altered sensory organization strategies. Visual occlusion modalities, if worn during neuromuscular control exercises, may facilitate greater postural control gains and a more appropriate sensory organization strategy. However, a cumulative review of the ability of visual occlusion modalities (e.g., stroboscopic goggles) to impair postural control and thus demonstrate the potential to facilitate greater postural gains has not yet been completed. Clinical Question: Does stroboscopic vision impair postural control in those with and without CAI, and if so, is the impairment comparable between the groups? Summary of Key Findings: Regardless of how postural control was assessed, stroboscopic vision impaired postural control relative to an eyes open (i.e., no goggles) condition. All studies demonstrated that those with and without CAI were impacted equally. Stroboscopic vision resulted in postural control impairments comparable to an eyes closed in some but not all studies. Clinical Bottom Line: Stroboscopic vision impairs postural control in both those with CAI and uninjured controls. Strength of Recommendation: There is moderate-quality evidence (Grade B) that stroboscopic vision impairs postural control in those with CAI and uninjured controls.

A flexible train composition strategy with extra-long trains for high-speed railway corridors with time-varying demand

To accommodate the uneven spatio-temporal distribution of passenger demand and improve the maximum transportation capacity for high-speed railway (HSR) corridors, this study proposes a demand-oriented flexible train composition strategy. The proposed strategy allows flexibility in selecting the number of train composition units (e.g., train carriages) for each train to accommodate the demand variations, where extra-long trains (longer than the length of the train station platform) might be utilized. Under such a strategy, a seat allocation method coupled with a train stopping position control strategy is proposed to avoid the need for cross-carriage walking during passenger boarding or alighting (for those extra-long trains). The train stopping position control strategy specifies the carriages that dock at or extend beyond the station platform, while the seat allocation method allocates seats within each carriage to specific origin-destination pairs. The studied problem can be formulated as an integer nonlinear programming model, where the weighted sum of the HSR operating cost and passenger travel time cost is minimized. The proposed model is then reformulated into an integer linear programming model via a series of linearization techniques. A tailored heuristic algorithm based on the variable neighborhood search (VNS) and GUROBI solver is designed to produce high-quality solutions for large-scale problems. Two numerical examples, i.e., a small example and a real-world Shanghai-Hangzhou HSR line example, are presented to illustrate the effectiveness of the proposed approach. The computation results show that, in comparison to traditional fixed and flexible train composition strategies without extra-long trains, the proposed strategy can significantly reduce the total operating cost and total travel time cost.

EFFECT OF MANIPULATION OF BASE OF SUPPORT ON CENTER OF PRESSURE: COMPARISON OF CHILDREN WITH AND WITHOUT INTELLECTUAL DISABILITY

The postural control (PC) of children with intellectual disabilities (ID) have been extensively studied; however, there is limited information available on the role of PC strategies during manipulated balance conditions. The aim of this study is to investigate the effect of manipulation of the base of support on the center of pressure in the children with and without intellectual disabilities. This study included 34 girls with mild intellectual disabilities and 30 typically developing children of the same sex and age (7-13 years old). The participants as stood as still on a platform and completed four tasks: feet-together on a firm surface, feet-together on a foam surface, tandem stance on a firm surface, and tandem stance on a foam surface. The displacement, sway, amplitude, root mean square (RMS), velocity, and acceleration of the center of pressure (CoP) were calculated. The results indicate significant differences between the two groups in spatial variables of CoP movement (p &lt; 0.05). Moreover, sway and amplitude were found to be sensitive to changes in surface factors (p &lt; 0.05) and all variables to be sensitive to changes in stance position. There was significant interaction of stance*group in CoP velocity (p &lt; 0.05). Based on the results, children with intellectual disabilities demonstrated poorer postural control than the control group, particularly in more demanding PC tasks. However, the quantitative variables of CoP were less impacted by ID characteristics compared to spatial variables. Accordingly, it is suggested that the role of effective balance training on improving postural control strategies in ID children be investigated in future studies.

Training Postural Balance Control with Pelvic Force Field at the Boundary of Stability.

This study characterizes the effects of a postural training program on balance and muscle control strategies in a virtual reality (VR) environment. The Robotic Upright Stand Trainer (RobUST), which applies perturbative forces on the trunk and assistive forces on the pelvis, was used to deliver perturbation-based balance training (PBT) in a sample of 10 healthy participants. The VR task consisted of catching, aiming, and throwing a ball at a target. All participants received trunk perturbations during the VR task with forces tailored to the participant's maximum tolerance. A subgroup of these participants additionally received assistive forces at the pelvis during training. Postural kinematics were calculated before and after RobUST training, including (i) maximum perturbation force tolerated, (ii) center of pressure (COP) and pelvic excursions, (iii) postural muscle activations (EMG), and (iv) postural control strategies (the ankle and hip strategies). We observed an improvement in the maximum perturbation force and postural stability area in both groups and decreases in muscle activity. The behavior of the two groups differed for perturbations in the posterior direction where the unassisted group moved towards greater use of the hip strategy. In addition, the assisted group changed towards a lower margin of stability and higher pelvic excursion. We show that training with force assistance leads to a reactive balance strategy that permits pelvic excursion but that is efficient at restoring balance from displaced positions while training without assistance leads to reactive balance strategies that restrain pelvic excursion. Patient populations can benefit from a platform that encourages greater use of their range of motion.

Robust adaptive tracking control for dynamic positioning ships subject to dynamic safety constraints and actuator saturation

This paper proposed a novel robust adaptive trajectory tracking control scheme for dynamic positioning (DP) ships subjected to unknown time-varying disturbances, unknown model parameters, dynamic safety constraints, and actuator saturation. The dynamic safety constraints were guaranteed based on the tan-type barrier Lyapunov function (BLF) technique, which ensured the position and velocity of the DP vessel within the given constraints. Moreover, the radial basis function neural network (RBFNN) was adopted to approximate the unknown parameters of the dynamics model, and an adaptive neural disturbance observer (ANDO) was designed to compensate for lumped disturbances. An anti-windup system was developed to handle the actuator saturation effect. By combining the above techniques and back-stepping method, the final control law was presented, and the semi-global asymptotic convergence was achieved via rigorous theoretical analysis and Lyapunov proof. The results of simulations demonstrated the superiority and robustness of this approach in resolving the trajectory tracking challenges of DP ships. Moreover, the proposed control scheme is highly effective in optimizing the trajectory tracking of DP ships, as it takes into account the multiple constraints that may arise during the process, which is a valuable contribution to the field of DP ship trajectory tracking, providing a more comprehensive and effective solution to this complex problem.

Cooperative control for automatic towing operation by multiple DP tugboats with fully unknown model parameters

This paper presents a cooperative consensus control scheme for multiple unmanned dynamic positioning (DP) tugboats to transport an unactuated floating object through cables, aiming to promote the automation and intelligence of marine towing operation. The scheme implements a leader-follower formation strategy among distributed tugboats, maneuvering the object by adjusting the position of the virtual leader in a reasonable manner. To ensure the formation configuration, a cooperative consensus controller is integrated into the feedback controller of each tugboat local DP system. In addition, a customized model parameter-free DP system is proposed to enhance the tracking performance of a single tugboat, addressing the challenges of full unknown model parameters and large cable tension disturbances. The proposed automatic towing control scheme is verified through full-scale nonlinear time domain simulations under variable environmental conditions and formation configurations, demonstrating its effectiveness.

Robust adaptive control of dynamic positioning ship under thruster faults and unknown disturbances

The robust adaptive anti-disturbance fault-tolerant control strategy for the dynamic positioning (DP) system of ships is built on the disturbance observer, the adaptive fault observer with the vectorial backstepping approach. The disturbance observer is constructed to estimate the first-order Markov disturbances. The adaptive fault observer with the projection algorithm is designed to estimate partial thruster faults. By employing the vectorial backstepping method, the robust adaptive anti-disturbance fault-tolerant control law is developed to simultaneously achieve the disturbance compensation and the partial thruster fault tolerant. It is demonstrated using the Lyapunov functions that the robust adaptive anti-disturbance fault-tolerant controller can maintain the DP of the ship’s position and heading to achieve the desired value, while guaranteeing the global stability of all signals in the DP closed-loop control system. Finally, different cases in the unknown ocean disturbance environment demonstrate the effectiveness of the robust adaptive anti-disturbance fault-tolerant control strategy.

Dynamic postural control in women athletes with and without nonspecific low back pain with high and low pain-related anxiety- A case-control study

BackgroundLow back pain is common among athletes and it has been shown that postural control is altered in the general population with nonspecific low back pain (NSLBP). Psychological factors may also predispose individuals to risk of altered postural control. Dynamic postural control is essential to the performance of athletes. This study aimed to compare the dynamic postural control between women athletes with and without NSLBP with high and low pain-related anxiety.MethodsForty-five female athletes (15 NSLBP with high pain-related anxiety, 15 NSLBP with low pain-related anxiety, and 15 healthy (control)) were included. Pain-related anxiety was assessed using the Pain Anxiety Symptom Scale-20 (PASS-20). Based on the cut-off score of 30 for the total score of PASS-20, NSLBP patients were classified into two groups of low and high pain-related anxiety. Participants performed double-leg vertical drop jump (DVJ) and single-leg vertical jump (SVJ) tests on a Kistler force plate (type 9260AA6, Kistler Instruments Inc, Switzerland). The total root mean square (RMS) of the center of pressure (COP), COP displacement in the anteroposterior (AP), and mediolateral (ML) directions, COP mean velocity, and time to stabilization (TTS) in vertical, AP, and total directions were extracted from COP and ground reaction force data using MATLAB software. One-way Analysis of variance (ANOVA) and Welch’s ANOVA were employed to compare the groups. In case of significant findings, post hoc tests were performed.ResultsThe results showed that during DJV, athletes with high pain-related anxiety had significantly greater TTS in all total, AP, and ML directions than other groups (P < 0.05). Also, the control group showed greater total RMS distance during DJV than either NSLBP group. However, no significant differences in TTS and COP parameters were found between the groups during SVJ (P > 0.05).ConclusionsThe findings suggest that pain-related anxiety may contribute to athletes’ postural control strategies. Therefore, it is important to consider the level of pain-related anxiety during planning postural control exercises for women athletes with NSLBP.

Precision Location-Aware and Intelligent Scheduling System for Monorail Transporters in Mountain Orchards

This study addressed the issue of the real-time monitoring and control of the transporter in a mountain orchard terrain characterized by varying topography, closed canopy, shade, and other environmental factors. This study involved independent research and the development of a series of electric monorail transporters. First, the application requirements of “Where is the monorail transporter?” were examined, and an accurate location-aware method based on high-frequency radio frequency identification (RFID) technology was proposed. In addition, a location-aware hardware system based on STM32 + RFID + LoRa was designed to determine the position of the monorail transporter on a rail. Second, regarding the application requirements of “Where is the monorail transporter going?”, a multimode control gateway system based on Raspberry Pi + LoRa + 5G was designed. An Android mobile terminal can obtain operational information about the transport plane in real time through the gateway system and remotely control its operation. The track-changing branch structure enables multimachine autonomous intelligent avoidance. Based on the experimental results of monorail transporter positioning in mountain orchards under various typical terrains, such as flat surfaces, turning paths, and uphill/downhill slopes, the road section average relative error of the 7ZDGS–250-type monorail transporter was 1.27% when the distance between benchmark positioning tags was set at 10 m on both flat and turning roads, and that of the 7ZDGS–300-type monorail transporter was 1.35% when the distance between benchmark positioning tags was set at 6 m uphill/downhill. The road section relative error of the 7ZDGS–250-type monorail transporter was 21.18%, and that of the 7ZDGS–300-type monorail transporter was 9.96%. In addition, the experimental results of monorail transporter communication control showed that the combination of the multimode control gateway control system and track-changing branch structure can achieve multimachine cooperation and autonomous avoidance function, ensuring that multiple monorail transporters can operate simultaneously without collision. The findings of this study establish the communication link of “monorail transporter-gateway system-control terminal” and form a precise positioning and real-time control scheme applicable to the operating environment of monorail transporters, thereby improving the intelligence and safety of mountain orchard monorail transporters.

Neural prosthesis control restores near-normative neuromechanics in standing postural control.

Current lower-limb prostheses do not provide active assistance in postural control tasks to maintain the user's balance, particularly in situations of perturbation. In this study, we aimed to address this missing function by enabling neural control of robotic lower-limb prostheses. Specifically, electromyographic (EMG) signals (amplified neural control signals) recorded from antagonistic residual ankle muscles were used to drive a robotic prosthetic ankle directly and continuously. Participants with transtibial amputation were recruited and trained in using the EMG-driven robotic ankle. We studied how using the EMG-controlled ankle affected the participants' anticipatory and compensatory postural control strategies and stability under expected perturbations compared with using their daily passive devices. We investigated the similarity of neuromuscular coordination (by analyzing motor modules) of the participants, using either device in a postural sway task, to that of able-bodied controls. Results showed that, compared with their passive prosthesis, the EMG-controlled prosthesis enabled participants to use near-normative postural control strategies, as evidenced by improved between-limb symmetry in intact-prosthetic center-of-pressure and joint angle excursions. Participants substantially improved postural stability, as evidenced by a reduction in steps or falls using the EMG-controlled prosthetic ankle. Furthermore, after relearning to use residual ankle muscles to drive the robotic ankle in postural control, nearly all participants' motor module structure shifted toward that observed in individuals without limb amputations. Here, we have demonstrated the potential benefit of direct EMG control of robotic lower limb prostheses to restore normative postural control strategies (both neural and biomechanical) toward enhancing standing postural stability in amputee users.

Strong fixed-time dynamic inverse adaptive LQR integrated control strategy for dynamic positioning of ship

To ensure compositive capacities for dynamic positioning ship, a dynamic inverse adaptive linear quadratic regulator (DI-ALQR) control strategy is proposed for dynamic positioning ship based on strong fixed-time prescribed performance function (SFPPF) and cascaded fixed-time extended state observer (CFESO). Firstly, a high-fidelity four degree of freedom ship motion model including roll motion is constructed, and an inverse system of the ship is proposed to realize decoupling of variables and pseudo linearization of control systems. Next, the SFPPF is employed to ensure prescribed performance with predefined convergence. The DI-ALQR control strategy is presented to achieve integrated control of position, roll and heading of ship considering the balance between energy consumption and control accuracy. Simulation results and analysis prove that the proposed control strategy makes the position, roll and heading of ship reach in predefined-time and maintain the desired values, which ensures prescribed performance.

Flexible performance‐based adaptive fault‐tolerant attitude tracking control for input‐constrained satellite

SummaryUnder the actuator saturation and fault, the satellite attitude often violates the prescribed performance function, leading to the satellite attitude's instability. Therefore, the adaptive attitude tracking control problem for the satellite simultaneously considering the finite time‐based prescribed performance, the actuator saturation and the actuator fault is studied in this article. A modification performance function‐based control scheme is designed, which can avoid violating the designed modified performance functions when the actuator saturation occurs due to the actuator fault. A novel fault tolerant auxiliary system is developed, which is used to generate modification signals for adjusting the prescribed performance function. Consequently, the boundedness of all the closed‐loop signal under the designed control scheme is proved via Lyapunov function method. Finally, the feasibility of the designed satellite attitude control scheme is verified by a simulation example.

Model-Free Adaptive Positioning Control of the Bidirectional Stick-Slip Piezoelectric Actuator with Coupled Asymmetric Flexure-Hinge Mechanisms.

A model-free adaptive positioning control strategy for piezoelectric stick-slip actuators (PSSAs) with uncertain disturbance is proposed. The designed controller consists of a data-driven self-learning feedforward controller and a model-free adaptive feedback controller with a radial basis function neural network (RBFNN)-based observer. Unlike the traditional model-based control methods, the model-free adaptive control (MFAC) strategy avoids the complicated modeling process. First, the nonlinear system of the PSSA is dynamically linearized into a data model. Then, the model-free adaptive feedback controller based on a data model is designed to avoid the complicated modeling process and enhance the robustness of the control system. Simultaneously, the data-driven self-learning feedforward controller is improved to realize the high-precision control performance. Additionally, the convergence of the tracking error and the boundedness of the control output signal are proved. Finally, the experimentally obtained results illustrate the advantages and effectiveness of the developed control methodology on the bidirectional stick-slip piezoelectric actuator with coupled asymmetric flexure-hinge mechanisms. The positioning error through the proposed controller reaches 30 nm under the low-frequency condition and 200 nm under the high-frequency condition when the target position is set to 100 μm. In addition, the target position can be accurately tracked in less than 0.5 s in the presence of a 100 Hz frequency.

Adaptive Position Control Strategy of SRM-Based EMA System for Precision Position Tracking

The electromechanical actuator (EMA) driven by switched reluctance motor (SRM) is promising to be used in the steering vane control system on the landing craft air cushion (LCAC) hovercraft due to its reduced maintenance costs and increased control flexibility. However, the system parameter uncertainty, the unknown load disturbance, and the large torque ripple of SRM make it challenging to achieve high position control precision. To improve the position control accuracy of the SRM-based EMA system, an adaptive position control strategy is proposed in this paper. Firstly, an adaptive fast terminal sliding mode controller (AFTSMC) is designed to address the issues of model parameter estimation and load disturbance rejection, which improves the dynamic response performance of the SRM-based EMA system. Secondly, a current-limited direct torque controller (CL-DTC) is proposed to track the reference torque calculated by AFTSMC with lower torque ripple and to limit the excessive currents of SRM at the same time, which helps further enhance the position control precision and prevent the SRM-based EMA from overheating. Finally, the proposed position control strategy is tested and compared with other three position controllers based on simulations and experiments. The results demonstrate the effectiveness and superiority of the proposed position control strategy.

Visual Perception and Convolutional Neural Network-Based Robotic Autonomous Lung Ultrasound Scanning Localization System.

Under the situation of severe COVID-19 epidemic, lung ultrasound (LUS) has been proved to be an effective and convenient method to diagnose and evaluate the extent of respiratory disease. However, the traditional clinical ultrasound (US) scanning requires doctors not only to be in close contact with patients but also to have rich experience. In order to alleviate the shortage of medical resources and reduce the work stress and risk of infection for doctors, we propose a visual perception and convolutional neural network (CNN)-based robotic autonomous LUS scanning localization system to realize scanned target recognition, probe pose solution and movement, and the acquisition of US images. The LUS scanned targets are identified through the target segmentation and localization algorithm based on the improved CNN, which is using the depth camera to collect the image information; furthermore, the method based on multiscale compensation normal vector is used to solve the attitude of the probe; finally, a position control strategy based on force feedback is designed to optimize the position and attitude of the probe, which can not only obtain high-quality US images but also ensure the safety of patients and the system. The results of human LUS scanning experiment verify the accuracy and feasibility of the system. The positioning accuracy of the scanned targets is 15.63 ± 0.18 mm, and the distance accuracy and rotation angle accuracy of the probe position calculation are 6.38 ± 0.25 mm and 8.60° ±2.29° , respectively. More importantly, the obtained high-quality US images can clearly capture the main pathological features of the lung. The system is expected to be applied in clinical practice.