Continuous sliding mode control for the translational oscillator with a rotating actuator system

The stabilization and disturbance rejection of the translational oscillator with a rotating actuator (TORA) are considered in this paper. To deal with the control issues, a novel continuous sliding mode control method is designed for the TORA system. Compared with existing sliding mode control methods for the TORA system, the proposed method here is continuous. Specifically, first, a global diffeomorphism is introduced for the model of the TORA system. Then, an elaborate sliding manifold is constructed, and a continuous sliding mode control scheme is developed to ensure the convergence of the sliding manifold. Furthermore, rigorous theoretical analysis is given. Finally, simulation tests are carried out, and the obtained simulation results demonstrate that the proposed method exhibits superior stabilization control performance and strong robustness.

Neural network-based adaptive sliding mode control for underactuated dual overhead cranes suffering from matched and unmatched disturbances

To improve transportation capacity, dual overhead crane systems (DOCSs) are playing an increasingly important role in the transportation of large/heavy cargos and containers. Unfortunately, when trying to deal with the control problem, current methods fail to fully consider such factors as external disturbances, input dead zones, parameter uncertainties, and other unmodeled dynamics that DOCSs usually suffer from. As a result, dramatic degradation is caused in the control performance, which badly hinders the practical applications of DOCSs. Motivated by this fact, this paper designs a neural network-based adaptive sliding mode control (SMC) method for DOCS to solve the aforementioned issues, which achieves satisfactory control performance for both actuated and underactuated state variables, even in the presence of matched and mismatched disturbances. The asymptotic stability of the desired equilibrium point is proved with rigorous Lyapunov-based analysis. Finally, extensive hardware experimental results are collected to verify the efficiency and robustness of the proposed method.

Static Postural Control Deficits in Adults with Myotonic Dystrophy Type 1, Steinert Disease

Background: Myotonic dystrophy type 1 (DM1) is characterized by progressive and predominantly distal muscle atrophy and myotonia. Gait and balance impairments, resulting in falls, are frequently reported in this population. However, the extent to which individuals with DM1 rely more on a specific sensory system for balance than asymptomatic individuals (AI) is unknown. Objective: Evaluate postural control performance in individuals with DM1 and its dependence on vision compared to AI. Methods: 20 participants with DM1, divided into two groups based on their diagnosis, i.e. adult and congenital phenotype, and 12 AI participants were recruited. Quiet standing postural control was assessed in two visual conditions: eyes-open and eyes-closed. The outcomes measures were center of pressure (CoP) mean velocity, CoP range of displacement in anteroposterior and mediolateral axis, and the 95% confidence ellipse’s surface. Friedman and Kruskal-Wallis analysis of variance were used to compare outcomes between conditions and groups, respectively. Results: Significant group effect and condition effect were observed on postural control performance. No significant difference was observed between the two DM1 groups. The significant differences observed between the AI group and the two DM1 groups in the eyes-open condition were also observed in the eyes-closed condition. Conclusions: The result revealed poorer postural control performance in people with DM1 compared to AI. The DM1 group also showed similar decrease in performance than AI in eyes-closed condition, suggesting no excessive visual dependency.

The Impact of Pain on Functionality, Postural Control and Fall Risk in Woman Aged 45 to 64 Years Old

Background: Ageing in women is associated with chronic degenerative pain leading to a functional decrease and therefore increase fall risk. It is therefore essential to detect early functional decreases in the presence of pain related to osteoarthritis. Objective: This cross-sectional study aimed to assess the impact of pain on functionality, postural control and fall risk in women aged between 45 to 64 years old. Methods: Twenty-one (21) women aged 45 to 64 were evaluated by clinical and functional measures such as a pain questionnaire (Lequesne Index), functional tests (Stair Step Test, 5 times sit-to-stand, 6MWD, Timed-up and Go) and postural performance (under force platform). Women were classified into 2 groups from the Lequesne Pain Index (PI): low pain (score ≤ 9) and strong pain (score ≥ 10) for subsequent comparisons on functionality (physical and postural control performance). Results: A significant impact was observed between the pain index (strong PI) and 3 of the 4 functional tests carried out including Stair Step Test (p = 0.001; g = 1.44), walking distance (p = 0.003; g = 1.31) and Timed-up and Go (p = 0.04; g = −0.93). The group with a strong PI score reported further poor postural control under force platform compared to the weak pain group. Conclusion: Pain and severity based on the PI index negatively modulate physical and postural control performance in women aged 45 to 64 years old.

Sliding-mode variable structure control for complex automatic systems: a survey

<abstract> <p>Automatic systems (ASs) can automatically control the work of controlled objects without unattended participation. They have been extensively used in industry, agriculture, automobiles, robots and other fields in recent years. However, the performance of the controller cannot meet the work requirements under complex environmental conditions. Therefore, improving the control performance is one of the difficult problems that automated systems should solve. Sliding-mode variable structure control has the advantages of fast response, insensitivity to uncertainty and interference and easy implementation; thus, it has been extensively used in the field of complex control systems. This article analyses and explains the research status of motors, microgrids, switched systems, aviation guidance, robots, mechanical systems, automobiles and unmanned aerial vehicles (UAVs) and prospects for the application of sliding-mode variable structure control in complex ASs.</p> </abstract>