Deviation Of Position Research Articles

The effect of spill change on reliable absolute dosimetry in a synchrotron proton spot scanning system.

Absolute dosimetry measurement is an integral part of Treatment Planning System (TPS) commissioning and it involves measuring the integrated absorbed dose to water for all energies in a pencil beam scanning delivery system. During the commissioning of Singapore's first proton therapy center, a uniform scanned field with an Advanced Markus chamber method was employed for this measurement, and a large dose fluctuation of at least 5% was observed for 10% of the energy layers during repeated measurements. This study aims to understand the root cause of this fluctuation by relating the actual delivered spot information in the log file with the charge measurement by the ion chambers. A dedicated pencil beam dose algorithm was developed, taking into account the log file parameters, to calculate the dose for a single energy layer in a homogeneous water phantom. Three energies, 70.2, 182.7, and 228.7 MeV were used in this study, with the 182.7 MeV energy exhibiting large dose fluctuation. The dose fluctuation was investigated as a function of detector's sizes (pinpoint 3D, Advanced Markus, PTW 34070, and PTW 34089) and water depth (2, 6, and 20cm). Twelve ion chambers measurements were performed for each chamber and depth. The comparison of the theoretically predicted integrated dose and the charge measurement served as a validation of the algorithm. About 5.9% and 9.6% dose fluctuation were observed in Advanced Markus and pinpoint 3D measurements at 2cm depth for 182.7 MeV, while fluctuation of 1.6% and 1.1% were observed in Advanced Markus with 228.7 and 70.2 MeV at similar depth. Fluctuation of less than 0.1% was observed for PTW34070 and PTW 34089 for all energies. The fluctuation was found to diminish with larger spot size at 20cm depth to 1.3% for 182.7 MeV. The theoretical and measured charge comparison showed a high linear correlation of for all datasets, indicating the fluctuation originated from the delivered spot characteristics. The cause of fluctuation was identified to be due to the spill change occurring close to the detector, and since the spot positional deviation profiles were different between two spills, this resulted in local hot spots between columns of spots. The actual position of spill change varies randomly during measurement, which led to a random occurrence of hot spot within the detector's sensitive volume and a fluctuating dose measurement. This is the first report of a dose fluctuation greater than 5% in absolute dosimetry measurement with a uniform scanned field and the cause of the fluctuation has been conclusively determined. It is important to choose the MU and scanning pattern carefully to avoid spill change happening when the spot delivery is near the detector.

Longitudinal and Lateral Control Strategies for Automatic Lane Change to Avoid Collision in Vehicle High-Speed Driving.

The vehicle particle model was built to compare and analyze the effectiveness of three different collision avoidance methods. The results show that during vehicle high-speed emergency collision avoidance, lane change collision avoidance requires a smaller longitudinal distance than braking collision avoidance and is closer to that with a combination of lane change and braking collision avoidance. Based on the above, a double-layer control strategy is proposed to avoid collision when vehicles change lanes at high speed. The quintic polynomial is chosen as the reference path after comparing and analyzing three polynomial reference trajectories. The multiobjective optimized model predictive control is used to track the lateral displacement, and the optimization objective is to minimize the lateral position deviation, yaw rate tracking deviation, and control increment. The lower longitudinal speed tracking control strategy is to control the vehicle drive system and brake system to track the expected speed. Finally, the lane changing conditions and other speed conditions of the vehicle at 120 km/h are verified. The results show that the control strategy can track the longitudinal and lateral trajectories well and achieve effective lane change and collision avoidance.

A Novel Approach of 3D Based Pattern Making Block by Analyzing Positional Deviation of Draping and Drafting Method

As 3D-based pattern making and onscreen fit evaluation is the neoteric way of garment production which allows constructing 2D (drafting) and 3D (draping) based pattern making simultaneously. This study approaches to evaluate the deviation of major checkpoints of the upper body which have been made of conventional pattern-making methods and proposes a new Block for the Female Upper Torso. This study is carried out on a physical and virtual mannequin of equal size with identical physical properties and body dimensions. Basic Bodice blocks are developed using “Metric pattern cutting” and “The art of fashion draping” methods for Pattern Drafting and Pattern Draping respectively. Positional deviations of major checkpoints are evaluated through comparative analysis. Logical decisions are made to construct new Pattern Blocks (Back, Front & Sleeve) where both Draping and Drafting methods are justified through physical and virtual fit evaluation where CLO 3D software is used. After fit evaluation by 10 Fashion educators, it is observed that the “Metric pattern cutting” Method poses more ease allowance than “The Art of Fashion Draping'' Method. The other observation of Shoulder Length, Shoulder Slope, Armhole Depth, Neck Girth, Bust Girth, Dart Placement, and Dart intake also deviated. Average values and average positions between these two systems show a better fit to generate a New Block.

Experimental investigations and error analysis on 3-PRS parallel kinematic machine

Industrial robots play a predominant role in factory automation particularly in the area of machining like grinding, cutting, milling, drilling, polishing etc. In these applications serial manipulators could not provide rigidity and accuracy. This research focuses on the need for precise angular drilling applications. Generally, special fixtures are used to make angular hole in drilling machines. In this research, the 3-PRS (Prismatic – Revolute – Spherical) parallel mechanism is redesigned to execute angular drilling operations. The moving/mobile platform (MP) of the proposed manipulator is utilized as worktable. The experimental model is fabricated with lead screw and nut pair to obtain precise position of drill tool and to maintain high stiffness. By varying the geometric parameters, the positions of parallel kinematic machine (PKM) are analysed. Moreover, the orientation error and parallelism of the developed PKM are studied in detail using laser torch and height gauge. Further, the PKM positions are simulated through ADAMS software package and the same is compared with the real-time accelerometer values. From the experimental study, the deviations in orientation, parallelism and position of the PKM are found to be minimal and satisfactory.

Persistent effects of mobile phone conversation while driving after disconnect: Physiological evidence and driving performance

Cognitive workload has been known as a key factor in traffic accidents, which can be highly increased by talking on the phone while driving. A wide range of studies around the world investigated the effects of mobile phone conversations on driving performance and traffic accidents. But less noticed is the durability of cognitive effects of mobile phone conversations. This study aimed to determine the effects of different types of mobile phone conversations on physiological response and driving performance during and after the conversation. Heart rate, heart rate variability (physiological response), Standard deviation of lane position (SDLP), and the relative distance between two cars (driving performance) of 34 samples (male and female) in the driving simulator were recorded. In this study, three types of conversations (neutral, cognitive, and arousal) were used. Neutral conversation did not pursue specific purpose questions. Cognitive conversations were simple mathematical problem-solving questions and arousal conversations aimed at arousing participant emotions. Each conversation was used as a secondary task in a condition. The study had three conditions; in each condition the participant drove for 15 min. Each condition consisted of 5 min of driving (Background), 5 min of driving and conversation (dual tasks) and 5 min of driving after conversation to trace the effects of the conversation. Vehicle speed was 110 km/h in each of the three conditions using car-following scenario. The results showed that neutral conversations had no significant effects on physiological response. Though, arousal conversations had significant effects on physiological responsiveness and driving performance during conversations, where it was even more significant after disconnection. Therefore, the content of the conversation determines the amount of cognitive load imposed on the driver. Considering the persistence of cognitive effects caused by conversation, the risk of traffic accidents is still high even after disconnection.

Enhanced Misalignment Estimation of Orbital Angular Momentum Signal Based on Deep Recurrent Neural Networks

This article presents a deep-learning-based approach to quantitatively extract misalignment information in the orbital angular momentum (OAM) radio communication systems. It is shown that the misaligned field exhibits unique sequence-based features for different misalignment information. Consequently, recurrent neural network, as a powerful method to deal with sequential data, is introduced to extract its intrinsic features and estimate the misalignment values. To further reduce the total number of parameters as well as improve the performance, a gated recurrent unit is employed to construct the recurrent layer. As far as we know, this is the first use of deep learning for the estimation of the OAM misalignment information in radio frequency. The setup of the training data and the performance of the proposed model under four different misalignment cases are demonstrated. To further validate the reliability of the proposed models, the trained model is evaluated on the sample carrying 20% Gaussian noise. Further, the effects of the position deviation and the number of samples are also investigated. Besides, the comparison with other methods are presented. It is illustrated that the tailored model can reach the same measurement resolution as the previous literatures while requiring only one-eighth of the sampling points.

Experimental and analytical studies on eliminating natural frequency splitting of an axisymmetric structure with cyclically symmetric feature groups

This work analytically and experimentally investigates natural frequency splitting behaviors for an axisymmetric stepped plate with circumferentially periodic groups of mass blocks. The simplified mathematical model of a stepped plate is derived using Hamilton's principle. Solving for the natural frequencies with a perturbation approach and Galerkin discretization yields the same closed-form conditions for natural frequency splitting or non-splitting. These closed-form conditions lead to analytical rules that govern splitting or non-splitting of natural frequencies for two different configurations of identical mass blocks in a group. These rules readily extend to other cyclically symmetric periodic structures of similar configurations. Simulations and experiments with a test rig show splitting or non-splitting of natural frequencies for the two configurations agrees with the analytical rules. Both the analytical and experimental results show the weight of mass blocks has no influence on the splitting or non-splitting of natural frequencies, but larger weight leads to larger differences between split natural frequencies. These tests also demonstrate the validity of these natural frequency splitting elimination rules for significant mode contamination. An experimental evaluation of the natural frequency splitting behaviors with respect to mass block weight and angular position deviations gives that the splitting of natural frequencies is insensitive to these deviations, but the non-splitting can be sensitive (i.e., natural frequencies that do not split without these deviations can split). This study provides guidelines for eliminating or reducing natural frequency splitting for cyclically symmetric systems like gyroscopes.

Exploring the centre of mass properties of LG-like galaxies

ABSTRACT From high resolution cosmological simulations of the Local Group in a realistic environment, namely HESTIA simulations, we study the position and kinematic deviations that may arise between the disc of a Milky Way (or Andromeda)-like galaxy and its halo. We focus on the three-dimensional analysis of the centres of mass (COM). The study presents two parts. We first consider individual particles to track down the nature and amplitude of the physical deviations of the COM with respect to the distance from the disc centre. Dark matter dominates the behaviour of the COM of all particles at all distances. But the total COM is also very close to the COM of stars. In the absence of a significant merger, the velocity offsets are marginal (10 km s−1) but the positional shifts can be important compared to the disc characteristics (>10 kpc). In the event of a massive accretion, discrepancies are of the same order as the recent finding for the MW under the Magellanic Clouds influence. In a second part, the accent is put on the study of various populations of subhaloes and satellites. We show that satellites properly represent the entire subhalo population. There exists strong mismatch in phase space between the satellites’ COM and the host disc. Moreover, the results are highly inhomogeneous between the simulations and thus, between the accretion histories. Finally, we point out that these shifts are mainly due to a few of the most massive objects.

Parking Robot Path-Tracking System Based on Discrete PID Algorithm

To improve the space utilization rates of intelligent stereo garages, their key execution equipment—parking robots—must be highly flexible; therefore, the chassis of parking robots use steering wheel systems. However, this design increases the complexity of robot motion control and path-tracking systems. Because of the large sizes of parking robots, large position and angle deviations can lead to derailment events, posing significant risk to users. Thus, in this study, based on the characteristics required for parking robots, a diagonally arranged parking robot with double steering wheels was developed and its kinematic model was established using the velocity–geometry method. For the positioning of the robot in a garage, a fusion positioning algorithm based on quick response (QR) codes and track calculation was used, considering the requirements of real-time response and accuracy. A discrete proportional-integral-derivative (PID) path-tracking algorithm for the synchronous compensation of the position and angle deviations was also devised. Using the Visual C++ platform, a path-tracking system that uses an industrial computer and motion control card was developed. Experiments on the path-tracking capability of the parking robot showed that, using the discrete PID path-tracking algorithm, it can track a planned path well. On Z- and U-type paths, its maximum tracking deviations were reduced by 84.8% and 64.0%, compared with the unused path-tracking system, reaching 10.4 mm and 10.9 mm, respectively. Thus, the tracking accuracy was significantly improved, proving that the developed robot well satisfies the path-tracking requirements of parking robots.

Influence of Antenna Element Position Deviation on Radiation Performance of Helical Antenna Array

The electrical performance of the feed array is degraded because of the position deviation of the array elements caused by manufacturing and processing, which cannot meet the high performance feeding requirements of large feed arrays. In this paper, a radiation field model of the helical antenna array considering the position deviation of array elements is proposed to investigate the influence law of position deviation on the electrical performance of the feed array. With the established model, the rectangular planar array and the circular array of the helical antenna with a radiating cup are discussed and the relationship between electrical performance index and position deviation is established by numerical analysis and curve fitting method. The research results show that the position deviation of the antenna array elements will lead to the rise of the sidelobe level, the deviation of the beam pointing, and the increase of the return loss. The valuable simulation results provided by this work can be used in antenna engineering, guiding antenna designers to set optimal parameters when fabricating antennae.

GNSS Signal Quality in Forest Stands for Off-Road Vehicle Navigation

One of the basic possibilities of orientation in forest stands is the use of global navigation satellite systems (GNSS). Today, these systems are used for pedestrian orientation and also for off-road vehicle navigation. This article presents the results of research aimed at measuring the quality of GNSS signal in different types of coniferous and deciduous vegetation for the purpose of optimizing the navigation of off-road vehicles. To determine the structure (density) of the forest stand, tachymetry was chosen as the reference method. The Trimble Geo 7X cm edition device with Tornado for 7X antenna devices using real time VRS (virtual reference station) method was used to measure GNSS signal quality. This article presents the results of recorded numbers of GNSS satellites (GPS, GLONASS, Galileo and BeiDou) during the driving of a terrain vehicle in two different forest locations. Significant presented results include the deviations of vehicle positions determined by GNSS from tachymetrically precisely measured and marked routes along which the vehicle was moving. The authors of the article focused on the accuracy of determining the position of the vehicle using GNNS, as the most commonly used device for off-road vehicle navigation. The measurement results confirmed the assumption that the accuracy of positioning was better in deciduous forest than in coniferous (spruce) or mixed vegetation. This research was purposefully focused on the possibilities of navigation of military vehicles, but the achieved results can also be applied to the navigation of forestry, rescue and other types of off-road vehicles.

An Individual Tree Segmentation Method That Combines LiDAR Data and Spectral Imagery

The dynamic monitoring of forest resources is an integral component of forest resource management and forest eco-system stability maintenance. In recent years, LiDAR (Light Detection and Ranging) has been increasingly utilized in precision forest surveys due to its great penetrating ability and capacity to detect forest vertical structure information. However, the present airborne LiDAR data individual tree segmentation algorithms are not highly adaptable to forest types, particularly in mixed coniferous and broad-leaved forest zones, where the accuracy of individual tree extraction is low, and trees are incorrectly recognized and missed. In order to address these issues, in this study, spectral images and LiDAR data of a red pine conifer–broadleaf mixed forest in the Changbai Mountain Nature Reserve in Jilin Province were chosen, and the normalized point cloud was segmented iteratively using the distance-threshold-based individual tree segmentation method to obtain the initial segmented individual tree vertices. For individual trees with deviations in the initial vertex identification position, and unidentified individual trees, identification anchor points of real tree vertices are added within the canopy of the trees. These identification anchor points have strong position directivity in LiDAR data, which can mark the individual trees whose vertices were misidentified or missed during the initial individual tree segmentation process and identify these two tuples. The tree vertices may be inserted precisely based on the 3D shape of the individual tree point cloud, and the seed-point-based individual tree segmentation method is used to segment the normalized point cloud and finish the extraction of individual trees in red pine mixed conifer forests. The results indicate that, compared to the previous individual tree segmentation approach based on the relative spacing between individual trees, this study enhances the accuracy of individual tree segmentation from 83% to 96%. The extremely high segmentation accuracy indicates that the proposed method can accurately identify individual trees based on remote sensing techniques to segment forest individual trees, can provide a data basis for subsequent individual tree information extraction, and has great potential in practical applications.

Evaluation of root position during orthodontic treatment via multiple intraoral scans with automated registration technology

This study aimed to introduce a method for dynamically monitoring root position with intraoral scans using automated crown registration and root segmentation with artificial intelligence technology and to evaluate its accuracy using a novel semiautomatic root apical distance measurement procedure. The sample consisted of 412 teeth from 16 patients whose intraoral scans and cone-beam computed tomography (CBCT) were obtained before and after treatment. Crowns from intraoral scans and roots segmented from CBCT with artificial intelligence technology before treatment were registered, integrated, and divided into individual teeth. With an automated registration program, the virtual root was constructed by crown registration before and after treatment. The distance deviation of the root position at the apex between the virtual root and the actual root, which served as a control, was measured and decomposed into the distance deviation in the mesiodistal and buccolingual directions. The shell deviation of crown registration between CBCT and oral scan before treatment was 0.19 ± 0.04 mm and 0.22 ± 0.04 mm in the maxilla and mandible, respectively. The apical root position distance deviations were 0.27 ± 0.12 mm in the maxilla and 0.31 ± 0.11 mm in the mandible. There was no significant difference between root position in mesiodistal and buccolingual directions. Applying automated crown registration and root segmentation with artificial intelligence technology in this study improved the accuracy and efficiency of monitoring root position. In addition, the innovative semiautomatic distance measurement procedure can more precisely distinguish the root position discrepancy.

Force constraint-based approach to compute the position and orientation of parts assembled by multiple non-ideal planes

The occurrence of position and orientation deviations (PODs) during the assembly of rigid components, which is caused by non-ideal morphologies on the manufactured surface, directly affects the performance of the mechanical product. Moreover, the generated PODs are influenced by the deformation of the contact points because of the assembly force. Therefore, to control the product performance in the design stage, the PODs should be computed considering both the non-ideal morphologies of the mating surfaces as well as the forces acting on the assembly. However, most existing approaches to POD computation ignore the effects of the assembly force. Moreover, they often focus on assemblies with a single mating plane. To address this problem, a force constraint-based approach is proposed in this study, which considers both the non-ideal morphologies of multiple mating planes and the assembly forces. The principle of force balance is employed to determine whether the assembly is completed. Different tentative positions and orientations are determined according to the strategies of progressively approaching position and orientation, and recursion of degrees of freedom (DOFs). An unbalance indicator was established in this study to determine whether the force balance in the direction of each DOF is satisfied. As long as the force balance of all DOFs to be constrained is achieved, the assembly of parts is considered to be finalised, and the final PODs are acquired. Finally, the PODs of a typical assembly with multi-mating planes and the guiding accuracy of a sliding workbench are computed according to the non-ideal morphologies modelled from the perspective of manufacturing errors, thereby validating the proposed approach.

Experimental dosimetric characterization of proton pencil beam distortion in a perpendicular magnetic field of an in-beam MR scanner.

As it promises more precise and conformal radiation treatments, magnetic resonance imaging-integrated proton therapy (MRiPT) is seen as a next step in image guidance for proton therapy. The Lorentz force, which affects the course of the proton pencil beams, presents a problem for beam delivery in the presence of a magneticfield. To investigate the influence of the 0.32-T perpendicular magnetic field of an MR scanner on the delivery of proton pencil beams inside an MRiPT prototypesystem. An MRiPT prototype comprising of a horizontal pencil beam scanning beam line and an open 0.32-T MR scanner was used to evaluate the impact of the vertical magnetic field on proton beam deflection and dose spot pattern deformation. Three different proton energies (100, 150, and 220 MeV) and two spot map sizes (15 × 15 and 30 × 20 cm2 ) at four locations along the beam path without and with magnetic field were measured. Pencil-beam dose spots were measured using EBT3 films and a 2D scintillation detector. To study the magnetic field effects, a 2D Gaussian fit was applied to each individual dose spot to determine the central position , minimum and maximum lateral standard deviation ( and ), orientation (θ), and the eccentricity (ε). The dose spots were subjected to three simultaneous effects: (a) lateral horizontal beam deflection, (b) asymmetric trapezoidal deformation of the dose spot pattern, and (c) deformation and rotation of individual dose spots. The strongest effects were observed at a proton energy of 100 MeV with a horizontal beam deflection of 14-186 mm along the beam path. Within the central imaging field of the MR scanner, the maximum relative dose spot size decreased by up to 3.66%, while increased by a maximum of 2.15%. The largest decrease and increase in the eccentricity of the dose spots were 0.08 and 0.02, respectively. The spot orientation θ was rotated by a maximum of 5.39°. At the higher proton energies, the same effects were still seen, although to a lesserdegree. The effect of an MRiPT prototype's magnetic field on the proton beam path, dose spot pattern, and dose spot form has been measured for the first time. The findings show that the impact of the MF must be appropriately recognized in a future MRiPT treatment planning system. The results emphasize the need for additional research (e.g., effect of magnetic field on proton beams with range shifters and impact of MR imaging sequences) before MRiPT applications can be employed to treat patients.

Convergent validity of video-based observer rating of drowsiness, against subjective, behavioral, and physiological measures.

Driver drowsiness is a widely recognized cause of motor vehicle accidents. Therefore, a reduction in drowsy driving crashes is required. Many studies evaluating the crash risk of drowsy driving and developing drowsiness detection systems, have used observer rating of drowsiness (ORD) as a reference standard (i.e. ground truth) of drowsiness. ORD is a method of human raters evaluating the levels of driver drowsiness, by visually observing a driver. Despite the widespread use of ORD, concerns remain regarding its convergent validity, which is supported by the relationship between ORD and other drowsiness measures. The objective of the present study was to validate video-based ORD, by examining correlations between ORD levels and other drowsiness measures. Seventeen participants performed eight sessions of a simulated driving task, verbally responding to Karolinska sleepiness scale (KSS), while infra-red face video, lateral position of the participant's car, eye closure, electrooculography (EOG), and electroencephalography (EEG) were recorded. Three experienced raters evaluated the ORD levels by observing facial videos. The results showed significant positive correlations between the ORD levels and all other drowsiness measures (i.e., KSS, standard deviation of the lateral position of the car, percentage of time occupied by slow eye movement calculated from EOG, EEG alpha power, and EEG theta power). The results support the convergent validity of video-based ORD as a measure of driver drowsiness. This suggests that ORD might be suitable as a ground truth for drowsiness.

Versatile end effector for laparoscopic robotic scrub nurse

PurposeIntegrating robotic scrub nurses in the operating room has the potential to help overcome staff shortages and limited use of available operating capacities in hospitals. Existing approaches of robotic scrub nurses are mainly focused on open surgical procedures, neglecting laparoscopic procedures. Laparoscopic interventions offer great potential for the context-sensitive integration of robotic systems due to possible standardization. However, the first step is to ensure the safe manipulation of laparoscopic instruments.MethodsA robotic platform with a universal gripper system was designed to pick up and place laparoscopic as well as da Vinci^{circledR } instruments in an efficient workflow. The robustness of the gripper system was studied using a test protocol, which included a force absorption test to determine the operational safety limits of the design and a grip test to determine the system performance.ResultsThe test protocol shows results regarding force and torque absorption capabilities of the end effector, which are essential when transferring an instrument to the surgeon to enable a robust handover. The grip tests show that the laparoscopic instruments can be safely picked up, manipulated and returned independent of unexpected positional deviations. The gripper system also enables the manipulation of da Vinci^{circledR } instruments, opening the door for robot–robot interaction.ConclusionOur evaluation tests have shown that our robotic scrub nurse with the universal gripper system can safely and robustly manipulate laparoscopic and da Vinci^{circledR } instruments. The system design will continue with the integration of context-sensitive capabilities.

Robust Shape-Distortion Prediction for a Wire-Driven Hyper-Redundant Manipulator With Engaging Rolling Joints

In Minimally Invasive Surgery (MIS), wire-driven hyper-redundant manipulators are widely used because of their flexibility, dexterity, and miniaturization. However, due to their limited structural stiffness, wire-elongation and unwanted distortion in the shape may occur during payload handling. For example, the surgical payload at the end-effector can distort an endoscope and cause positional deviation of the end-effector. In this paper, an endoscopic manipulator with robust Engaging Rolling Joints (ERJs) is proposed, where each ERJ is deployed with a pair of Auxiliary Super-elastic Ribbons (ASRs). Based on the design, we also developed a prediction model for shape-distortion, which is able to numerically predict the shape of the manipulator under payload applied to the end-effector. Experiments were conducted to verify that the ERJ and the ASR can better reject unwanted disturbances in shape prediction. The test results showed that the predicted distorted shape is in good agreement with the actual shape; the average prediction errors for the distal angle and position deflections were measured at 8.63% and 7.71%, respectively. We believe that the presented technique will help to improve the performance of the rolling joint manipulator by compensating the predicted shape-distortion.

High performance assembly of complex structural parts in special environments – research on space manipulator assisted module docking method

PurposeCompared with the robotic manipulation in structured environment, high performance assembly of complex parts in extreme special environment is facing great challenges because of the uncertainty in the environment, and the decline of the control accuracy of the robot and the sensor accuracy. The assembly and construction of the space station is a typical case. An important step in the construction of the space station is the module positioning and docking with the auxiliary of the space manipulator. The operation of the manipulator is faced with many problems, such as low sensing information accuracy, large end position deviation and the requirement of weak impact in the docking process. The purpose of this paper is to design a docking method at the strategy level to effectively solve the problems that may be faced in the docking process.Design/methodology/approachInspired by the research of robotic high-precision compliant assembly, this paper introduces the concept of Attractive Region in Environment (ARIE) into the space manipulator–assisted module docking. The contact configuration space of the docking mechanism and the existence of ARIE are systematically analyzed. The docking strategy based on ARIE framework is proposed, in which the impedance control is used to ensure the weak impact during the docking process.FindingsFor the androgynous peripheral spacecraft docking mechanism, a large range of attractive region exists in the high-dimensional contact configuration space. The docking strategy based on ARIE framework can be designed according to the geometric characteristics of the constraint region and the structural characteristics of the docking mechanism. The virtual models and the simulation environment are established, and the effectiveness of the proposed method is preliminarily verified.Originality/valueBased on the research results of robotic precision compliant manipulation, in this paper, the theory of ARIE is first systematically applied to the analysis of spacecraft docking problem and the design of docking scheme. The effectiveness of the proposed docking method is preliminarily verified for the requirements of large position tolerance and weak impact. The research results will provide theoretical support and technical reference for the assembly and construction of space station and other space manipulator operations.

An adaptive control method for the covers on the south roof of Chinese solar greenhouses: A case study of insulation blankets

The Chinese solar greenhouse (CSG) enables farming activities in colder conditions and extends the harvest time. It is a crucial component of Chinese agricultural facilities. Rolling/unrolling the cover on the south roof is critical for modifying the greenhouse environment and improving the production efficiency of CSGs. However, since the structure of CSGs is constantly being updated, the existing winding equipment is inadequate because it causes deformation of covers. This study used as insulation blankets an example to proposed an adaptive control method of the rolling cover of CSGs. Deformation and force analysis showed that the fundamental reason for the deformation of the insulation blanket and the winding mechanism was the uneven load distribution in the length direction. A segmented winding mechanism and multi-motor scheme were used to reduce the deformation of the insulation blanket. A fuzzy proportional–integral–derivative (PID) control algorithm was developed to adjust the speed of the slave motors adaptively to roll/unroll the insulation blanket. The simulation results showed that the shorter winding mechanism resulted in lower torsional deformation. Experiments using a scale model demonstrated that the proposed double-motor scheme and fuzzy PID control method provided good performance for rolling/unrolling the insulation blanket. The double-motor scheme can significantly improve the operation efficiency of rolling insulation blankets. The running time of the double-motor scheme was 12.81% lower than that of the single-motor scheme, the average absolute position deviation was 41.95% lower, and the average absolute standard deviation was 44.51% lower. The proposed fuzzy PID control strategies enable the closed-loop control of the deceleration motor and the adjustment of the displacement deviation to reduce the deformation of the insulation blanket according to the feedback received from the slave motor. Unlike the conventional PID control, the fuzzy PID control automatically adjusts the system parameters to eliminate the system error. The control accuracy and stability of the fuzzy PID method have reached a good level, and the applicability is better than that of the conventional PID method. In the scale model experiments, the average position deviation remained within ±1 mm, and the average standard deviation was 1.32 mm. The proposed adaptive control method for the cover on the south roof of CSGs is highly suitable for practical applications. The study also provides application examples and theoretical references for the automation of rolling covers in greenhouses worldwide.