Ideal Trajectory Research Articles

Trajectory tracking control of two-joint underwater manipulator in ocean-wave environment

In this study, a dynamic model of a two-joint manipulator used in underwater robots considering the influence of ocean waves was derived based on the Lagrange principle and Newton–Euler method. The Morison equation was employed to calculate the inertial force and water resistance of ocean waves acting on the manipulator. The ocean force terms in the new model vary with time, which makes trajectory tracking control more complicated than in models used in land and still-water environments. The ideal trajectory of the manipulator was tracked using proportional-derivative (PD) control and sliding mode control (SMC). The PD control proved weak in trajectory tracking, whereas the sliding mode control could quickly and accurately track the ideal trajectory. Three reaching laws were compared, and variable exponential reaching law 2 was the most suitable for trajectory tracking. To test the sliding mode control ability, an experiment was conducted in an ocean-wave environment with varying ocean wave heights, wave frequencies, and water depths. In addition, variations in input torque were observed. It was also found that the input torque required in an ocean-wave environment was higher than that required in land and still-water environments.

Neuroendoscopic transventricular transchoroidal approach for access to the posterior zone of the third ventricle or pineal region.

The endoscopic transventricular transchoroidal approach facilitates entry into the posterior part of the third ventricle, allowing a visualization field from the foramen of Monro to the pineal region through this anatomical corridor. Combined surgery to treat the target lesion and possible endoscopic third ventriculostomy (ETV) can be performed through a single burr hole. A detailed description of this surgical technique is given, and a series of cases from our center is presented. This retrospective study included patients with lesions in the pineal region or posterior zone of the third ventricle who underwent surgery between 2004 and 2022 in our center for tumor biopsy or endoscopic cyst fenestration. In nine cases, the transchoroidal approach was performed. Demographic and clinical variables were collected: sex, age at diagnosis, clinical presentation, characteristics of the lesion, pathological diagnosis, characteristics of the procedure, complications, subsequent treatments, evolution, follow-up time, and degree of success of the endoscopic procedure. The mean and range of the quantitative variables and frequency of the qualitative variables were analyzed, together with the statistical significance (p < 0.05). Surgical planning was carried out by performing a preoperative MRI, calculating the ideal entry point and trajectory for each case. The preoperative planning of the surgical technique is described in detail. Of our sample, 55.6% were women, with a mean age of 35years (7-78). The most common clinical presentation was intracranial hypertension (55.6%), with or without a focus. Eight patients presented hydrocephalus at diagnosis. The most frequent procedure was endoscopic biopsy with ETV (66.7%). The pathological diagnosis varied widely. Procedure-related complications included one case of self-limited bleeding of the choroidal fissure at its opening and one intraventricular hemorrhage due to tumor bleeding in the postoperative period. Non-procedure-related complications comprised two ETV failures and one case of systemic infection, while late complications included one case of disease progression and one case of radionecrosis. Four patients died, one due to poor neurological evolution after post-surgical tumor bleeding and three due to causes unrelated to the procedure. The rest of the patients had a favorable evolution and were asymptomatic or stable. The transchoroidal approach through a single burr hole is a feasible and safe option for access to the posterior part of the third ventricle. Proper planning of each case is necessary to avoid complications.

National Strategic Development Project in Environmental Law: Economic Growth or Reduction in Public Participation

Public participation is fundamental aspect in environmental decision making though environmental impact assessment. Government in developing country, such as Indonesia tends to use constitutional law as a legitimation for development without consider the rights of people in the society. Purpose the article is analysing the implementation of public participation in national strategic development project. The article uses normative method to check regulation coherency. Comparative approach also uses to find problems in environmental decision making that is related to national strategic development project and conceptual approach as well to make an ideal trajectory for a model law. Result finds that information and access to participate have a major role on how government do a project for development. In conclusion, public participation in environmental decision making is important because it contains access to information, access to participate, and access to justice for creating democratic and establish genuine public participation.

Visual Navigation and Obstacle Avoidance Control for Agricultural Robots via LiDAR and Camera

Obstacle avoidance control and navigation in unstructured agricultural environments are key to the safe operation of autonomous robots, especially for agricultural machinery, where cost and stability should be taken into account. In this paper, we designed a navigation and obstacle avoidance system for agricultural robots based on LiDAR and a vision camera. The improved clustering algorithm is used to quickly and accurately analyze the obstacle information collected by LiDAR in real time. Also, the convex hull algorithm is combined with the rotating calipers algorithm to obtain the maximum diameter of the convex polygon of the clustered data. Obstacle avoidance paths and course control methods are developed based on the danger zones of obstacles. Moreover, by performing color space analysis and feature analysis on the complex orchard environment images, the optimal H-component of HSV color space is selected to obtain the ideal vision-guided trajectory images based on mean filtering and corrosion treatment. Finally, the proposed algorithm is integrated into the Three-Wheeled Mobile Differential Robot (TWMDR) platform to carry out obstacle avoidance experiments, and the results show the effectiveness and robustness of the proposed algorithm. The research conclusion can achieve satisfactory results in precise obstacle avoidance and intelligent navigation control of agricultural robots.

Optimal tracking control of the coal mining face fluid supply system via adaptive dynamic programming

Emulsion pump station is widely used to provide power for full-mechanized coal mining face equipment. With the development of the mining technique of longwall face and the extensive use of large mining height and high working resistance of the hydraulic support, the fluid supply pressure is more unstable and the pressure impact is increasingly intensified. The intelligent control of the emulsion pump station is the key to the development of the stable fluid supply technology at the working face. This paper develops a new on-line adaptive learning technique to improve the response speed of pumping station based on the optimal control algorithm of adaptive dynamic programming (ADP). The state space model of the working face fluid supply system in the process of no-load column lifting of hydraulic support is first established using the flow relationship, and the effectiveness of the proposed control algorithm is then verified by simulation validation. Moreover, combined with a certain fluid supply system of a fully mechanized caving face in Shandong Energy Xinwen Group XinJulong Co., Ltd, a technical scheme of adaptive stable fluid supply is verified in engineering practice. The results indicate that the fluid supply system using the proposed control algorithm has a favorable tracking effect on the ideal trajectory, and the tracking error can converge to near zero. The output pressure of the fluid supply system using the stable fluid supply technology is more stable, and the practical effect is good, which meets the demand of stable fluid supply in the mining face.

A Novel Communication Pathway Metric Evaluation using Throughput and Energy Improvements over Wireless Sensor Networks

Lifetime connectivity and low power consumption are two requirements for WSNs. Additionally, increasing WSN commercialization, application monitoring for higher QoS. Maintaining the improvement of the wireless sensor networks effectiveness requires the establishment of the energy-efficient and consistent connection. In order to increase the efficiency of routing algorithms in latest technology assisted WSNs, a novel method is developed. The gadgets with the lowest power consumption are carefully selected for the appropriate use and carefully managed. The goal of this research is to develop low-power routing algorithms for use in WSNs. Numerous sectors, including the military, the medical profession, surveillance of observing, public transportation sectors etc., can benefit from wireless sensor networks deployed with a large number of mobile nodes in a communications system. To examine data from nodes that are freely moving about the zone, we developed and simulated a wireless network system based on the Distributed Internet of Things. The proposed method of Intelligent Route Metric Analyzer (IRMA) improves upon the efficiency of the standard algorithm with regards to energy consumption. In addition, the ground wireless sensing design's ideal trajectory is identified using a realistic tempering approach. In the end, this concept is compared to similar ones like AODV and the findings reveal that it performs better with regard to of energy consumption, delay and other important metrics. According to the paper we analyzed, the primary objective was to devise a routing method that would sustain network operation for as long as feasible by decreasing the energy needed for different operations at each individual sensor node while keeping the total energy consumption of the nodes constant over their lifetimes. Finally, the study makes a contribution to the ongoing discussion of the difficulties in developing a routing protocol for WSN, taking into account the interdependency of different network factors. Median throughput, median network latency, and standardized route load are only few of the efficiency metrics addressed in this article.

The Finance Money Crisis and Cryptocurrencies

The speculative financial services sector and the systemic failures of financial globalisation have prompted a growing call for delinking from the hegemony of the US dollar. These systemic failures have been illustrated by financial mismanagement and the financial crisis of 2007-8. This event paints a dire picture of the consequences associated with poor regulation of the financial sector. This study seeks to interpret these events in terms of Gramsci’s Prison Notebooks and his concept of the ‘morbid symptoms of the interregnum’. According to Babic (2020), these occur when a hegemony and its institutions are ‘dying’, thereby hampering their power. This notion also highlights that the future remains murky, despite public calls for change. Gramsci calls this the ‘new that cannot be born’.This study seeks to extend this framework to the current state of the dollar hegemony. The ‘morbid symptoms’ we will examine include the call to delink from the speculative high-risk US economy, the emergence of cryptocurrencies, and the politics surrounding fiat money. Some have argued that the emergence of cryptocurrencies could be the ‘new’. However, this study argues that the negative characteristics associated with cryptocurrencies such as cybersecurity concerns and price volatility create ambiguity about whether cryptocurrency is the ideal trajectory. Therefore, it argues that ambiguity and calls for change qualify our current monetary situation to be classified as a Gramscian interregnum.It also examines the current fiat money discourse by highlighting how the dollar hegemony may be succeeded by another fiat currency. However, it argues that the inflationary shortfalls of fiat money make this a fallible option, thereby perpetuating the ambiguities within the Gramscian interregnum.

Investigating Cerebellar Modulation of Premovement Beta-Band Activity during Motor Adaptation.

Enhancing cerebellar activity influences motor cortical activity and contributes to motor adaptation, though it is unclear which neurophysiological mechanisms contributing to adaptation are influenced by the cerebellum. Pre-movement beta event-related desynchronization (β-ERD), which reflects a release of inhibitory control in the premotor cortex during movement planning, is one mechanism that may be modulated by the cerebellum through cerebellar-premotor connections. We hypothesized that enhancing cerebellar activity with intermittent theta burst stimulation (iTBS) would improve adaptation rates and increase β-ERD during motor adaptation. Thirty-four participants were randomly assigned to an active (A-iTBS) or sham cerebellar iTBS (S-iTBS) group. Participants performed a visuomotor task, using a joystick to move a cursor to targets, prior to receiving A-iTBS or S-iTBS, following which they completed training with a 45° rotation to the cursor movement. Behavioural adaptation was assessed using the angular error of the cursor path relative to the ideal trajectory. The results showed a greater adaptation rate following A-iTBS and an increase in β-ERD, specific to the high β range (20-30 Hz) during motor planning, compared to S-iTBS, indicative of cerebellar modulation of the motor cortical inhibitory control network. The enhanced release of inhibitory activity persisted throughout training, which suggests that the cerebellar influence over the premotor cortex extends beyond adaptation to other stages of motor learning. The results from this study further understanding of cerebellum-motor connections as they relate to acquiring motor skills and may inform future skill training and rehabilitation protocols.

Optimization of a novel drive mechanism approaching the ideal cycle for beta type Stirling engines

Stirling engines are capable in the renewable energy gain and the recovery of waste heat, both of which are important issues today. Existing studies revealed that the piston trajectories convergent to the Stirling cycle provide more power than traditional crank mechanism. In this study, a hypocycloid drive mechanism not used in the literature was optimized on the ideal piston trajectories for beta type Stirling engines. Optimization was realized to improve the isochoric heating and cooling processes as well as the isothermal compression and expansion. The cyclic work was treated as another objective succession. The optimal results taking into account these five objectives were obtained with the gear ratios of 5 and 4 for displacer piston and power piston, respectively. The piston dwells provided the enough objective succession not only for the both isochoric processes but also for the isothermal compression process, while failed in the isothermal expansion. In comparison with crank mechanism, a cyclic work increment of 10% was achieved in the near-ideal piston trajectories, but the maximum increment of 14% eventuated in some out of ideal.

A Time-Optimal Continuous Jerk Trajectory Planning Algorithm for Manipulators

In this paper, we propose a new optimal trajectory planning method for the manipulator to optimize its operating efficiency and ensure the smoothness of the motion process. The position sequences in joint space corresponding to a specified trajectory in task space are obtained by using the inverse kinematic algorithm, and the seventh-degree B-spline curve interpolation method is used to construct the joint trajectory with controllable start–stop kinematic parameters, and continuous velocity, acceleration and jerk. The kinematic constraints of the manipulator are transformed into the control point constraints of the B-spline curve, the sequential quadratic programming method is used to solve the optimal motion time node, and then the time-optimal continuous jerk trajectory satisfying the nonlinear kinematic constraints is planned. Simulation results show that the proposed trajectory planning method provides the ideal trajectory for the joint controller, ensuring the manipulator can smoothly track any specified trajectory in the task space in the shortest time.

The Design of a Tracking Controller for Flexible Ball Screw Feed System Based on Integral Sliding Mode Control with a Generalized Extended State Observer

This article proposes a servo control strategy for compensating matched and mismatched perturbations in flexible ball screw feed systems to improve their tracking performance. The perturbations that satisfy or dissatisfy the matching conditions include external disturbances, parameter uncertainties, and unmodeled dynamics. The flexible ball screw feed model includes both a rigid body and first-order axial structural dynamics. A generalized extended state observer is adopted to observe the matched and mismatched perturbations and various state variables of the system, and an improved integral sliding mode controller is proposed that can simultaneously compensate for the perturbations of the system that satisfy and dissatisfy the matching conditions. In addition, vibration compensation is designed for first-order axial vibration of the system to develop a controller that can quickly and accurately track the ideal reference trajectory, suppress system structural vibrations, and be robust to time-varying uncertainties and external disturbances. Finally, the tracking performance, anti-interference performance, and vibration suppression performance of the designed controller are verified via simulation and comparative experiments.

Distributed data-driven iterative learning point-to-point consensus tracking control for unknown nonlinear multi-agent systems

This paper studies the point-to-point consensus tracking problem for a class of nonlinear non-affine multi-agent systems, where the tracking target is a series of some given ideal output points rather than a complete ideal trajectory. For the unknown nonlinear dynamics of every agent, the relationship between its control input and the corresponding output signal at these given points is acquired, then a data-driven model is constructed based on adjacent-agent dynamic linearization technology. Furthermore, by optimizing two performance index functions, we design a novel point-to-point iterative learning tracking control scheme, which not only ensures the consensus tracking results of all agents only utilizing the I/O data of every agent at the given ideal output points, but also makes all agents reach consensus behavior at the rest of the time instants. The effectiveness of our algorithm is confirmed through rigorous theoretical analysis and two experimental simulations.

Digital anatomical study and clinical application of the ideal S2 alar-lliac screw trajectory

BackgroundTo investigate the ideal trajectory for the S2AI screw and to clinically validate its safety feasibility.MethodsThe 3D model was reconstructed from CT data of the pelvis of 30 selected adults, and the 3D coordinate system was established with the first sacral superior endplate as the horizontal plane. A set of cutting planes was made at 3 mm intervals in the coronal plane, and the cross-sectional internal tangent circles were divided in the target area. Using the linear fitting function, the axis of 90 mm length was calculated by the least squares method for each inner tangent circle center. The diameter of the axis is gradually increased until the first contact with the cortex, and the cylindrical model is the ideal screw trajectory. The intersection of the axis and the dorsal cortex is the screw placement point, which is located by Horizon Distance (HD) and Vertical Distance (VD); the diameter of the screw trajectory (d) is the diameter of the cylindrical model; the direction of the screw trajectory is determined by Sagittal Angle (SA) and Transverse Angle (TA). The screw trajectory orientation is determined by Sagittal Angle (SA) and Transverse Angle (TA). Based on the ideal screw trajectory, the 3D printed surgical guide and freehand techniques were used to verify its safety feasibility, respectively.ResultsThe screw placement points [HD (4.7 ± 1.0) mm, VD (19.7 ± 1.9) mm], screw placement directions [SA (31.3°±2.3°), TA (42.4°±2.3°)], and screw dimensions for the ideal screw trajectory of the S2AI were combined for analysis. (L is 90 mm, d is 13.2 ± 1.4 mm). The S2AI screw superiority rate [96.6% (56/58)] and reasonable rate [100%] were higher in the guide group than in the freehand group [90.0% (63/70), 97.1% (68/70)], but the differences were not statistically significant (P > 0.05). Although screws invaded the cortex in both groups, there were no associated adverse events in either group.ConclusionThe S2AI screw-based ideal trajectory placement is a safe, feasible and accurate method of screw placement.

A framework of gravity field online modeling and trajectory optimization in asteroid soft-landing mission scenarios

Focused on asteroid soft-landing mission scenario, this paper investigates the methods of online gravity field modeling and trajectory optimization. Since the gravity field near asteroids and its surface topography are irregular, accurate asteroid soft-landing can be a challenging problem to solve, especially in the case of limited gravity data. With an actual asteroid soft-landing mission in mind, this study constructs a dataset based on the gravity field data collected in the limited area through which a soft-landing probe passed, and conducts online modeling of the asteroid inhomogeneous gravity field at the same time, using a transfer learning deep neural network (TL-DNN). To achieve fuel optimization and an accurate landing, a fast trajectory optimization method based on Bezier shape approach is implemented to achieve fast online robust re-trajectory optimization. Numerical simulation results show that the adopted TL-DNN can quickly reconstruct the gravitational field near the asteroid online, based only on the limited gravity data collected by the probe. Compared with the situation without online gravity field reconstruction and multiple online trajectory optimization, the proposed online gravity field modeling and re-trajectory optimization method can reduce the final position and velocity error between the multi-planned ideal optimal trajectory and the actual trajectory from 2396.367 m and 3.870 m/s to 14.152 m and 0.075 m/s, respectively. In other words, the soft-landing accuracy is improved by about two orders of magnitude.

A New Technology Using Mixed Reality Surgical Navigation with the Unlocking Closed Reduction Technique Frame to Assist Pelvic Fracture Reduction and Fixation: Technical Note.

Pelvic ring disruption (PRD) is a serious trauma associated with high mortality and disability rates. Poor reduction can lead to complications such as pelvic deformity and delayed fracture healing. Here, we introduce a new technology using mixed reality surgical navigation (MRSN) with an unlocking closed reduction technique (UCRT) frame to assist pelvic fracture reduction and fixation. Thirty patients with PRD were enrolled in this study. All of the patients underwent preoperative CT scans, with the pelvis and tracker segmented into three-dimensional models. Under MRSN guidance, auxiliary reduction screws were inserted to grasp the pelvic bone. An ideal trajectory for closed reduction was planned, and suitable CS screws were used for stable fixation after good reduction. Operation time, fluoroscopy frequency, and both Matta and Majeed scores were analyzed. The mean follow-up period was 10.8 months (7.5, 12.25 months) (range 6-24 months). The average duration of operation was 212.5 min (187.5, 272.8 min) (range 133-562 min), and the average reduction time was 23.0 min (15.0, 42.5 min) (range 10-70). The average fluoroscopy frequency was 34.0 times (31.5, 52.5 times) (range 23-68 times). One hundred and fifty screws were successfully inserted on the first attempt. All the fractures healed well with no complications. Excellent reduction quality (Matta score ≤4 mm) was achieved in 29/30 cases, and good reduction quality (Matta score between 4 and 10 mm) was achieved in 1/30 cases. All patients achieved bone healing after an average of 4.0 months (3.5, 5.9 months) (range 3-6), as well as good function recovery with an average Majeed score of 91.0 (87.8, 95.0) (range 71-100). The MRSN technique described improved reduction accuracy and radiation exposure without considerable extension of operation time.

Human-robot interaction for extraction of robotic disassembly information

ABSTRACT Disassembly of end-of-use products is critical to the economic feasibility of circular feedstock, reusing, recycling and remanufacturing loops. High-volume disassembly operations are constrained by disassembly complexity and product variability. The capability to buffer against timing, quantity and quality uncertainties of end-of-use products impacts the efficiency and profitability of demanufacturing systems. To achieve a competitive operation in the manufacturing life-cycle, disassembly systems need automated lines, however, the unpredictability of core supply challenges automation adaptability. Disassembly robot trajectories that are programmed manually or controlled by vision systems can be time intensive and subject to variability in lighting conditions and image recognition models. Alternatively, this paper presents a novel human-robot disassembly framework to systematically extract and generate robot trajectories derived from human-collaborative robot (cobot) disassembly. The collaborative training station proposed classifies trajectory segments and then adjusts trajectories to station-specific robots in a high-volume disassembly line. Virtual and physical collaborative disassembly case studies are presented and discussed. Results demonstrate the effectiveness of the disassembly data extraction method but indicate a disparity between the expected and ideal disassembly trajectories due to variability from human handling, which is further discussed in this paper.

Characteristics and evaluation of C1 posterior arch variation for transpedicular screw placement between patients with and without basilar invagination.

C1 transpedicular screw (C1TS) placement provided satisfactory pullout resistance and 3D stability, but its application might be limited in patients with basilar invagination (BI) due to the high incidences of the atlas anomaly and vertebral artery (VA) variation. However, no study has explored the classifications of C1 posterior arch variations and investigated their indications and ideal insertion trajectories for C1TS in BI. To investigate the bony and surrounding arterial characteristics of the atlas, classify posterior arch variations, identify indications for C1TS, evaluate ideal insertion trajectories for C1TS in BI patients without atlas occipitalization (AO), and compare them with those without BI and AO as control. A total of 130 non-AO patients with and without BI (52 patients and 78 patients, respectively) from two medical centers were included at a 1:1.5 ratio. The posterior arch variations were assessed using a modified C1 morphological classification. Comparisons regarding the bony and surrounding arterial characteristics, morphological classification distributions, and ideal insertion trajectories between BI and control groups were performed. The subgroup analyses based on different morphological classifications were also conducted. In addition, the factors possibly affecting the insertion parameters were investigated using multiple linear regression analyses. The BI group was associated with significantly smaller lateral mass height and width, sagittal length of posterior arch, pedicle height, vertical height of posterior arch, and distance between VA and VA groove (VAG) than control group. Four types of posterior arch variations with indications for different screw placement techniques were classified; Classifications I and II were suitable for C1TS. The BI cohort showed a significantly lower rate of Classification I than the control cohort. In the BI group, the subgroup of Classification I had significantly larger distance between the insertion point (IP) and inferior aspect of the posterior arch. In addition, it had the narrowest width along ideal screw trajectory, but a significantly more lateral ideal mediolateral angle than the subgroup of Classification II. Multiple linear regression indicated that the cephalad angle was significantly associated with the diagnosis of BI (B = 3.708, P < 0.001) and sagittal diameter of C1 (B = 3.417, P = 0.027); the ideal mediolateral angle was significantly associated with BMI (B = 0.264, P = 0.031), sagittal diameter of C1 (B = - 4.559, P = 0.002), and pedicle height (B = - 2.317, P < 0.001); the distance between the IP and inferior aspects of posterior arch was significantly associated with age (B = - 0.002, P = 0.035), BMI (B = - 0.007, P = 0.028), sagittal length of posterior arch (B = - 0.187, P = 0.032), pedicle height (B = - 0.392, P < 0.001), and middle and lower parts of posterior arch (B = 0.862, P < 0.001). The incidence of posterior arch variation in BI patients without AO was remarkably higher than that in control patients. The insertion parameters of posterior screws were different between the morphological classification types in BI and control groups. The distance between VA V3 segments and VAG in BI cohort was substantially smaller than that in control cohort. Preoperative individual 3D computed tomography (CT), CT angiography and intraoperative navigation are recommended for BI patients receiving posterior screw placement.

A phase plane H∞ controller for distributed drive electric vehicles with stability enhancement based on tire road friction coefficient estimation

An H∞ control strategy based on the phase plane method (phase plane H∞ controller) tracking two degrees of freedom (DOF) ideal vehicle trajectory scheme is designed for distributed drive electric vehicles with stability enhancement. Firstly, an Extended Kalman Filter (EKF) tire road friction coefficient estimation method based on Keras neural network is presented to accurately and efficiently identify the tire road friction coefficient, taking into account the huge influence of the tire road friction coefficient on vehicle equilibrium point and stability region. Secondly, the phase plane method is applied to provide a dynamic stability boundary for the switching control strategy of direct yaw moment for different tire road friction coefficients; Furthermore, based on the dynamic stability boundary, the weighted phase stability is applied to achieve more realistic stability evaluation criteria, and the fuzzy control strategy is adopted to carry out the feedback regulator of the target side slip angle and yaw rate on the purpose of limiting its maximum value max ( β) and max ( ωr). Then the torque of the four-wheel was optimized by the quadratic programming method. Finally, the presented method is verified and the results indicate that: (1) the phase plane H∞ control has the advantage in terms of stability and maneuvering performance. More importantly, under a low tire road friction coefficient, the amplitude of the side slip angle is decreased by 26.52% over the H∞; (2) the designed EKF based on Keras neural network parameter correction has a quick and accurate performance in identifying the tire road friction coefficient, and the steady-state error does not exceed 3.25%.

Anatomic trajectory for iliac screw placement adapts better to the morphological features of the pelvis of each individual than the S2 alar iliac screw: a radiological study

PurposeThe iliac fixation (IF) through the S2 ala permits the minimization of implant prominence and tissue dissection. An alternative to this technique is the anatomic iliac screw fixation (AI), which considers the perpendicular axis to the narrowest width of the ileum and the width of the screw. The morphological accuracy of the iliac screw insertion of two low profile iliac fixation (IF) techniques is investigated in this study.MethodsTwenty-nine patients operated on via low profile IF technique were divided into two groups, those treated using 28 screws with the starting point at S2, and those treated with 30 AI entry point. Radiological parameters (Tsv-angle, Sag-Angle, Max-length, sacral-distance, iliac-width, S2-midline, skin-distance, iliac-wing, and PSIS distance) and clinical outcomes (early and clinic complications) were evaluated by two blinded expert radiologists, and the results were compared in both groups with the real trajectory of the screws placed.ResultsDifferences between ideal and real trajectories were observed in 6 of the 9 evaluated parameters in the S2AI group. In the AI group, these trajectories were similar, except for TSV-Angle, Max-length, Iliac-width, and distance to iliac-wing parameters. Moreover, compared with S2AI, AI provided better adaptation to the pelvic morphology in all parameters, except for sagittal plane angulation, skin distance, and iliac width.ConclusionsAI ensures the advantages of low profile pelvic fixation like S2AI, with a starting point in line with S1 pedicle anchors and low implant prominence, and moreover adapts better to the morphological features of the pelvis of each individual.

Robust approximate constraint following control for SCARA robots system with uncertainty and experimental validation

In the context of mechanical systems characterized by nonlinearity, uncertainty, and unknown external disturbances, this paper presents a novel and practical robust control algorithm based on the Udwadia–Kalaba (UK) equation that incorporates the ideal system trajectory as a servo constraint. Firstly, the constraint force of the system under servo constraints can be written in analytic form, which is the first part of the proposed control algorithm. The remaining parts deal with the initial condition incompatibility and the uncertainty within the system, respectively. Secondly, it is proved that the controlled system with uniform boundedness (UB) and uniform ultimate boundedness (UUB) by using the Lyapunov method. Finally, based on the SCARA robot platform, numerical simulations and experiments are performed using the rapid control prototype CSPACE. The results indicate that the proposed robust control method provides excellent dynamic performance under the constraints of the ideal trajectory. The effectiveness and practicality of the control method are further demonstrated.