Extensible Rods Research Articles

Design and Verification of Piano Playing Assisted Hand Exoskeleton Robot.

Finger technique is a crucial aspect of piano learning, and hand exoskeleton mechanisms effectively assist novice piano players in maintaining correct finger technique consistently. Addressing current issues with exoskeleton robots, such as the inability to provide continuous correction of finger technique and their considerable weight, a novel hand exoskeleton robot has been developed to enhance finger technique through continuous correction and reduced weight. Initial data are gathered using finger joint angle sensors to analyze movements during piano playing, focusing on the trajectory and angular velocity of key strikes. This analysis informs the design of a 6-bar double-closed-loop mechanism with an end equivalent sliding pair, using analytical methods to establish the relationship between motor extension and input rod rotation. Simulation studies assess the exoskeleton's motion space and dynamics, confirming its capability to meet structural and functional demands for accurate key striking. Prototype testing validates the exoskeleton's ability to maintain correct finger positioning and mimic natural strike speeds, thus improving playing technique while ensuring comfort and safety.

Analysis of heating defects in extension rods of extra-high voltage direct current overhead transmission lines

This paper studies the overheating defect of an extension rod in a ± 800 kV extra-high voltage direct current overhead transmission line, and proposes various factors that affect the overheating of the extension rod. Establish an equivalent model of an extra high voltage DC transmission line based on equipotential point and line parameter analysis, and calculate the model parameters. The proposed model can also be applied to ultra-high voltage DC overhead transmission lines such as ± 500 kV, and has strong universality. Simulation experiments show that if the equivalent resistance value of the split wire side is reduced by 0.01Ω, the power loss on the extension tie rod can be increased to 380.951 W; if the equivalent resistance value of the jumper side is increased by 0.01Ω, the power loss on the extension tie rod can be increased to 273.41 W. Combined with theoretical analysis and simulation verification, it is concluded that the main factor affecting the overheating of the extension rod is the change in the resistance value on the jumper side caused by the increase in contact resistance. A systematic troubleshooting plan for related defect problems is proposed, which has important reference and guidance significance for such line fault problems.

Comparative study of different extendable intramedullary rods combined with surgery in the treatment of congenital pseudarthrosis of the tibia

BackgroundWhen using traditional extensible intramedullary rods to treat congenital pseudarthrosis of the tibia (CPT), there were cases of re-fracture and internal fixation fracture. Therefore, the authors propose a research hypothesis that a thicker distal extensible intramedullary rod can better protect the tibia and reduce the incidence of refracturePurposeTo investigate the clinical efficacy of new and traditional extensible intramedullary rods in the treatment of CPT in childrenMethodsFrom January 2017 to December 2021, the clinical data of 49 children with CPT who were treated with traditional extensible intramedullary rod combined surgery (group A) and new extensible intramedullary rod combined surgery (group B) in our hospital were collected. Inclusive criteria: ① Crawford type IV CPT children; ② The operation was performed by the same team. Exclusion criteria: patients with multiple tibial angulation. During follow-up, the initial healing, proximal tibial valgus, tibial length, ankle valgus, refracture and intramedullary rod displacement of CPT children in the two groups were evaluatedResultsIt was a retrospective investigation. In group A, 26 cases met the inclusion criteria, 24 cases achieved primary healing, with an primary healing rate of 92%, including 1 case of nonunion due to osteomyelitis complications after surgery, and 1 case of delayed healing, with an average healing time of 4.7 ± 0.8 months. 17 cases (68%) had unequal tibia length, with an average difference of 1.6 ± 0.8 cm. Ankle valgus occurred in 10 cases (40%) with an average of 14.4°±4.8°; Proximal tibial valgus occurred in 6 cases (24%) with an average of 7 °± 1.8 °. 20 cases (80%) had tip of the rod migration.10 cases (40%) had re-fracture; The average follow-up time was 2.4 ± 0.4 years. In group B, 22 patients achieved primary healing, and the primary healing rate was 95%, including 1 case with delayed healing. The average healing time was 4.7 ± 1.7months. 14 cases (61%) had unequal tibia length, with an average difference of 1 ± 0.5 cm. Ankle valgus occurred in 4 cases (17%) with an average of 12.3 °±4.9°; The proximal tibia valgus occurred in 9 cases (39%), with an average of 7.7 °±2.5 °. 14 cases (61%) had new type of intramedullary rod displacement. 3 cases (13%) had re-fracture; The average follow-up time was 2.3 ± 0.6yearsConclusionCompared with the traditional extended intramedullary rod combined operation, the new type of extended intramedullary rod combined operation has a lower incidence of re-fracture after CPT, but it still needs to be verified by large sample and multi-center research

Impact of Anterior and Posterior Vault Distraction Osteogenesis (A-PVDO) and 3D-Printed Positioning/Shaping Templates in Apert Syndrome: A Case Series Study.

This study seeks to examine the impact of anterior and posterior vault distraction osteogenesis (A-PVDO) in conjunction with 3D-printed positioning and shaping templates for the management of Apert syndrome. From January 2018 to February 2022, a retrospective analysis was conducted on 6 cases of Apert syndrome employing fronto-orbital 3D-printed positioning and molding templates. The cranium underwent surgical modification in accordance with the template's configuration and was affixed with absorbable plates. Subsequently, distraction devices were applied, encompassing both anterior and posterior craniotomies. The evaluation encompassed clinical outcomes, complications (including cerebrospinal fluid leakage and infection), safety, and the feasibility of the distraction osteogenesis procedure. Six patients diagnosed with Apert syndrome underwent treatment involving the integration of fronto-orbital 3D-printed positioning and shaping templates in conjunction with anterior and posterior cranial distraction osteoplasty. Follow-up durations ranged from 18 to 32 months (average: 22mo). No instances of fronto-orbital retraction, cerebrospinal fluid leakage, or intracranial infection were noted during the follow-up period. The sole reported complication entailed an infection at the extension rod site in 1 case. All patients conveyed satisfaction with the treatment outcomes. The application of 3D-printed positioning and shaping templates in tandem with anterior and posterior cranial distraction osteogenesis demonstrates efficacy in addressing Apert syndrome. Notably, significant enhancements in head shape and orbit were observed, and the incidence of postoperative complications such as cerebrospinal fluid leakage and infection remained minimal. Moreover, long-term follow-up affirmed stability.

Comparison of two different intramedullary rods combined with Ilizarov external fixation and wrapped autologous iliac bone grafting for the treatment of congenital tibial pseudarthrosis in children

Objective: To compare the initial clinical efficacy of extensible intramedullary rod fixation and Williams intramedullary rod fixation combined with Ilizarov external fixation and wrapped autologous iliac bone grafting in the treatment of congenital tibial pseudarthrosis in children. Methods: A retrospective analysis was conducted on the clinical data of 60 children with Crawford Ⅳtype congenital pseudarthrosis of the tibia treated with combined surgery at the Orthopedics Department of Hunan Children's Hospital from January 2013 to December 2020.According to different internal fixation methods,patients were divided into the extensible intramedullary rod group (30 cases) and the Williams intramedullary rod group (30 cases). There were 12 males and 18 females in the extendable intramedullary rod group, aged (33.6±6.3) months (range: 18 to 44 months), while there were 10 males and 20 females in the Williams intramedullary rod group, aged (47.8±8.6) months (range: 36 to 66 months). The anteroposterior and lateral views of tibia and fibula and the full length anteroposterior film of both lower limbs were examined to compare the clinical treatment effects of the two groups at 1-,3-,6-,9-, and 12-month after surgery. Independent sample t-test, χ2 test or Fisher exact test was used for inter group comparison. Results: Both groups of children underwent surgery successfully, with postoperative follow-up time greater than 2 years. The extensible intramedullary rod group was followed up for (49.5±6.4) months, while the Williams intramedullary rod group was followed up for (53.7±10.5) months. The initial bone healing time between the broken ends of the tibial pseudarthrosis was (5.1±0.8) months in the extensible intramedullary rod group and (5.0±0.6) months in the Williams intramedullary rod group. There was no statistically significant difference between the two groups (t=0.584, P=0.562). The initial postoperative bone healing rate of the extensible intramedullary rod group was 93.3% (28/30), while that of the Williams intramedullary rod group was 96.7% (29/30). There was no statistically significant difference between the groups (χ2=0.351 P=0.554).The postoperative fracture rate of the extensible intramedullary rod group was 20.0% (6/30), while that of the Williams intramedullary rod group was 16.7% (5/30);Six cases (20.0%) in the extensible intramedullary rod group had unequal limb lengths in both lower limbs after surgery, with a limb length difference of (2.5±1.4)cm (range: 1.5 to 5.2 cm). Eight cases (26.7%) in the Williams intramedullary rod group had a limb length difference of (2.8±1.4)cm (range: 1.8 to 6.0 cm);After surgery, there were 4 (13.3%) cases of proximal tibial valgus deformity in the extensible intramedullary rod group, with an valgus angle range of (12.5±4.9)° (range: 7 °to 18°), and 3 (10.0%) cases in the Williams intramedullary rod group, with an valgus angle of (15.0±6.0)° (range: 9°to 21°). There were 2 (6.7%) cases of ankle valgus deformity in the extensible intramedullary rod group, with an valgus angle of (11.5±4.9)° (range: 8 °to 15°), and 4 (13.3%) cases in the Williams intramedullary rod group, with an valgus angle of (14.8±6.2)° (range: 6 °to 20°). The postoperative activities of the knee and ankle joints in the extensible intramedullary rod group were normal and unrestricted, with 4 cases of extensible intramedullary rod displacement.In the Williams intramedullary rod group, there were 30 cases of postoperative ankle joint stiffness and no displacement of the fixation position of the intramedullary rod.There was no statistically significant difference in postoperative complications between the two groups of children (all P>0.05). Conclusions: The use of both extensible intramedullary rods and Williams intramedullary rods in the combined surgery for congenital tibial pseudarthrosis in children can achieve effective internal fixation results. The initial postoperative bone healing rate is high, and there is no difference in the incidence of postoperative complications between groups. Both internal fixation methods have their own advantages and disadvantages, and suitable internal fixation methods can be selected based on the characteristics of the patient.

Value of personalized osteotomy in primary total knee arthroplasty for severe varus knee osteoarthritis

To explore application value and efficacy of personalized osteotomy in primary total knee arthroplasty (TKA) for severe varus knee osteoarthritis. From June 2018 to January 2020, 36 patients (49 knees) with severe varus knee osteoarthritis were treated, including 15 males (21 knees) and 21 females (28 knees), aged from 59 to 82 years old with an average of (67.6 ± 6.5) years old;the course of disease ranged from 9.5 to 20.5 years with an average of (15.0 ± 5.0) years;11 patients (15 knees) with Kellgren-Lawrence grade Ⅲ and 25 patients (34 knees) with grade Ⅳ according to Kellgren-Lawrence grading. According to AORI clsssification of tibial bone defects, 8 patients (15 knees) were typeⅠTa and 16 patients (18 knees) were typeⅡ T2a. All patients' femor-tibial angle (FTA) was above 15°, and received primary TKA with personalized osteotomy. Thirty-three patients (45 knees) were treated with posterior-stabilized (PS) prostheses, 13 patients (15 knees) with PS prostheses combined with a metal pad and extension rod on the tibial side, and 3 patients (4 knees) with legacy constrained condylar knee (LCCK) prostheses. FTA, posterior condylar angle (PCA), medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) before and after operation at 1 month were measured and compared by using picture archiving and communication systems (PACS). Recovery of lower limbs before and after operation at 12 months was evaluated by American Knee Society Score(KSS), and complications were observed and recorded. All 36 patients (49 knees) were followed up from 15 to 40 months with an average of (23.46±7.65) months. FTA, MPTA were corrected from preoperative (18.65±4.28)° and (83.75±3.65)° to postoperative (2.35±1.46)° and (88.85±2.25)° at 1 month, respectively (P<0.001). PCA was decreased from (2.42±2.16)° before operation to (1.65±1.35)° at 1 month after operation, LDFA improved from (89.56 ± 3.55)° before operation to (91.63±3.38)° at 1 month after operation (P<0.05). KSS increased from (67.58±24.16) before opertion to(171.31±15.24) at 12 months after operation, 14 patients (19 knees) got excellent result, 19 (26 knees) good, and 3 (4 knees) fair. Personalized osteotomy is helpful for recovery of axial alignment of lower limbs and correct placement of prosthesis, could effectively relieve pain of knee joint, recover knee joint function.

Operation characteristics of soil blasting vibration test device under vibration load

To improve the accuracy of vibration velocity monitoring during blasting in soil layers, this paper provides a method and device for data correction by combining finite element software and actual engineering test data. Based on the length of the test pedestal exposed to the surface of the geotechnical body, the finite element structural model corresponding to each length of the test pedestal is established. Moreover, a predetermined external excitation load is applied outside the finite element model and the correction function of the vibration data is obtained by analysis of the stress and vibration data. The device solves the problem of low accuracy of vibration velocity measurement in soil and establishes a correction method for measurement data. The results show the following: (1) With the propagation of blasting seismic waves, the maximum stress values of the test device appear in the footwall position, the middle of the extension rod, and the bottom position in that order. (2) At the end of the test, there is an obvious phenomenon of speed amplification at the top of the test device. (3) As the length of the test device exposed to the ground increases, the particle peak vibration velocity (PPV) of the test device varies exponentially with the PPV of the ground and the range of variation of the vibration velocity in the X-direction is the largest.

Retrospective evaluation of pre-surgical electroretinography results in a mixed-breed canine population presented for cataract removal surgery.

Electroretinography (ERG) is used prior to cataract removal surgery to assess retinal function. We aimed to replicate and improve upon previous studies by performing a full ECVO protocol and by examining the retina post-surgery in all patients. One hundred twenty-seven eyes from 67 dogs were included in the study. A full ECVO protocol electroretinography, which includes extensive rod and cone analysis, was performed on all dogs presenting for cataract surgery. Our main findings were that amplitudes, but not implicit times of rod responses decreased with advanced cataracts. Amplitudes of the single flash rod and rod flicker responses were significantly lower in eyes with mature cataracts, and the former also decreased in hypermature cataracts. Cone flicker amplitude responses were also significantly lower in eyes with mature and hypermature cataracts. However, mixed single flash rod-cone and cone responses, with the exception of the mixed rod-cone a-wave amplitude in eyes with hypermature cataracts, were unaffected by cataract stage. The b-wave amplitude of the scotopic, mixed rod-cone, and photopic cone responses were affected by age and decreased by an average of 2.9, 7.5, and 1.5μV/year, retrospectively (p < 0.01). Lower ERG amplitudes in canine cataract patients may result from aging or the presence of advanced cataracts and may not indicate the presence of retinal disease.

Analysis of clinical and radiological outcomes of long tibial stemmed total knee arthroplasty in knee osteoarthritis complicated by tibial stress fracture

ObjectiveKnee arthritis associated with tibial stress fractures represents an uncommon and difficult clinical scenario to treat. The use of long, fluted tibial extension rods has been vital in the management of such cases owing to immediate fracture stability and single-stage surgery without the need to open the fracture site. This study investigates clinical and radiological outcomes following total knee arthroplasty using a tibial extension stem in cases of knee osteoarthritis with tibial stress fracture.MethodsFrom February 2015 to December 2020, 17 patients who had total knee arthroplasty implanted with a long stemmed tibial component were included in the study. Patient data were analyzed for knee range of motion, deformities, Knee Society score, knee function score, and time to fracture union in the pre- and postoperative periods.ResultsThe mean follow-up duration was 22.7 ± 11.68 months (range 12–60 months), and mean time to fracture healing was 10.23 ± 2.81 weeks (range 8–20 weeks). The preoperative mean fixed flexion deformity improved from 8.53 ± 3.43° to a mean of 0.29°, and knee flexion improved from 79.4 ± 13.90° to 125.29 ± 8.74° on postoperative assessment. The Knee Society score improved from a mean preoperative score of 18.94 ± 5.55 (range 8–28) to 89.41 ± 7.5 (range 74–102, p value < 0.001). Similarly, the knee function score improved significantly from a mean preoperative score of 15.5 ± 4.48 (range 8–26) to a mean of 85 ± 6.09 (range 72–94, p value < 0.001).ConclusionTotal knee arthroplasty using long tibial extenders has been an effective and safe surgical option for patients with advanced osteoarthritis with tibial stress fractures.

Study and numerical analysis of Von Mises stress of a new tumor-type distal femoral prosthesis comprising a peek composite reinforced with carbon fibers: finite element analysis

Research on carbon-fiber-reinforced polyetheretherketone (CF-PEEK/CFR-PEEK) as a bone tumor joint prosthesis remains limited. Herein we numerically determine the feasibility of CF-PEEK material containing 30% Wt carbon fiber (CF30-PEEK) as a material for the dual-action tumor-type distal femoral prosthesis. Use CT scan method to build a complete finite element model of the knee joint. Simulate the resection of the distal femoral tumor, and then reconstruct it with the dual-action tumor-type distal femoral prosthesis. The femoral condyle and extension rod components were simulated with cobalt chromium molybdenum (CoCrMo), PEEK and CF30-PEEK materials respectively. When simulating the standing state, a vertical stress of 700 N is applied to the femoral head. When simulating the squatting state, a vertical stress of 2800 N is applied to the femoral head. The displacement and rotation angle of each node of the distal tibia are fully restrained in three directions (X-axis, Y-axis, Z-axis). We examined the stress magnitude, stress distribution, and stability of the prosthesis and each of its components by means of finite element analysis (FE analysis). The FE analysis results show: after replacing the distal femur and the extension rod with CF30-PEEK material, the stress is still evenly distributed, and the average stress is significantly reduced. In addition, the stability is similar to CoCrMo material. Therefore, CF30-PEEK is an appropriate material for this type of prosthesis.

BRISTLED PIPE ROBOT WITH ADJUSTABLE BRISTLES

The bristled pipe robot moving in the pipe on the principle of friction difference is intended for locomotion in the pipe using the friction difference between the bristles and the pipe's inner wall. The robot consists of an electromagnetic linear actuator, on the frame of which the rear bristle block is attached and on its extension rod, the front bristle block is placed. The bristle blocks contain three bristle carriers and clamps. The bristles are the contact elements between the robot and the pipe's inner wall. The geometry of the bristles can be adjusted using the adjusting elements. The bristles are mounted on the robot so that the span of their free ends is greater than the inner diameter of the pipe, thus creating the desired normal and frictional force between the pipe wall and the bristle ends. The bristles are mounted at a mounting angle concerning the robot axis, thus creating a difference in friction between the pipe wall and the bristles as they move back and forth, resulting in a forward movement of the robot.

Non‐material finite element rod model for the lateral run‐off in a two‐pulley belt drive

AbstractA novel mixed Eulerian‐Lagrangian rod finite element formulation based on the theory of unshearable, extensible rods is presented. Geometric imperfections (natural curvature) are introduced to investigate and predict the phenomenon of lateral run‐off in the benchmark problem of a two‐pulley belt drive. The concise description of normal and tangential contact between pulleys and belt contributes to the efficient computation of transient solutions. In resemblance of belt shear theory, it relies on the notion of a thin intermediate layer that connects the belt and the pulleys elastically. Various practically relevant transient solutions are validated against corresponding shell finite element computations available in the literature.

Trunnionosis in total knee arthroplasty: an unusual case report in revision knee arthroplasty

Background: Trunnionosis has been described as an emerging cause of failure in total hip arthroplasty. However, its role in total knee arthroplasty failure is poorly described. Case Report: A case of catastrophic failure of revision total knee arthroplasty at 7 years due to trunnionosis at the femoral extension rod morse-taper junction is described. The possible mechanism of failure is discussed based on a comprehensive finite element analysis. Conclusions: The limitations of modularity and trunnionosis must be understood, as many patients have been receiving modular total knee arthroplasty at younger ages.

Classical Kapitsa’s problem of stability of an inverted pendulum and some generalizations

The classical Kapitsa’s problem of stability of an inverted pendulum subjected to vertical vibration of the support and some generalizations are investigated. The asymptotic method of two-scale expansions allows one to determine the level of vibrations that stabilizes the vertical position of the rod. The cases of inextensible and extensible rod are studied, and a benchmark of results is carried out. An attraction basin of the stable vertical position of the rod is found. Both harmonic and random stationary vibrations of the support are considered, too. Stability and attraction basin of the vertical position for a flexible rod are studied in detail. A single-mode approximation is used for the approximate solution to the nonlinear problem of stability of a flexible rod.

HDAC inhibition ameliorates cone survival in retinitis pigmentosa mice

Cone photoreceptor cell death in inherited retinal diseases, such as Retinitis Pigmentosa (RP), leads to the loss of high acuity and color vision and, ultimately to blindness. In RP, a vast number of mutations perturb the structure and function of rod photoreceptors, while cones remain initially unaffected. Extensive rod loss in advanced stages of the disease triggers cone death by a mechanism that is still largely unknown. Here, we show that secondary cone cell death in animal models for RP is associated with increased activity of histone deacetylates (HDACs). A single intravitreal injection of an HDAC inhibitor at late stages of the disease, when the majority of rods have already degenerated, was sufficient to delay cone death and support long-term cone survival in two mouse models for RP, affected by mutations in the phosphodiesterase 6b gene. Moreover, the surviving cones remained light-sensitive, leading to an improvement in visual function. RNA-seq analysis of protected cones demonstrated that HDAC inhibition initiated multi-level protection via regulation of different pro-survival pathways, including MAPK, PI3K-Akt, and autophagy. This study suggests a unique opportunity for targeted pharmacological protection of secondary dying cones by HDAC inhibition and creates hope to maintain vision in RP patients even in advanced disease stages.

Modeling flexoelectricity in soft dielectrics at finite deformation

This paper develops the equilibrium equations describing the flexoelectric effect in soft dielectrics under large deformations. Previous works have developed related theories using a flexoelectric coupling tensor of mixed material–spatial character. Here, we formulate the model in terms of a flexoelectric tensor completely defined in the material frame, with the same symmetries of the small-strain flexocoupling tensor and leading naturally to objective flexoelectric polarization fields. The energy potential and equilibrium equations are first expressed in terms of deformation and polarization, and then rewritten in terms of deformation and electric potential, yielding an unconstrained system of fourth order partial differential equations (PDE). We further develop a theory of geometrically nonlinear extensible flexoelectric rods under open and closed circuit conditions, with which we examine analytically cantilever bending and buckling under mechanical and electrical actuation. Besides being a simple and explicit model pertinent to slender structures, this rod theory also allows us to test our general theory and its numerical implementation using B-splines. This numerical implementation is robust as it handles the electromechanical instabilities in soft flexoelectric materials.

Improved filtering and normalizing of Measurement-While-Drilling (MWD) data in tunnel excavation

Measurement-While-Drilling (MWD) data are complex because of the drilling process and drilling system. Swift and accurate normalization and filtration processes are required if MWD data are to be used for rock mass characterization. The current method for MWD data filtration does not consider all the effects of the drilling process, e.g., collaring or extension rod coupling. This paper presents a new method for MWD data filtration and normalization. The new method filters the operational parameters and normalizes the data on a stepwise algorithm, including production factors (collaring drill hole and rod extension coupling) and rock drill settings. It shows reliable results for the normalization and filtration of MWD data gathered for drill hole collaring and coupled extension drill rods at grout holes and for different rock drills.

A numerical method for inextensible elastic filaments in viscous fluids

The deformations of flagella are important in the motility of single- and multi-flagellated bacteria. Existing numerical methods have treated flagella as extensible filaments with a large extensional modulus, resulting in a stiff numerical problem and long simulation times. However, flagella are nearly inextensible, so to avoid large extensional stiffness, we introduce inextensible elastic rod models with hydrodynamics treated by a surface distribution of regularized Stokeslets. We benchmark this new model against previously described models of extensible elastic rods with hydrodynamics treated by a centerline distribution of regularized Stokeslets and rotlets, as well as a surface distribution of regularized Stokeslets. We compare the accuracy of the inextensible model with the extensible models and illustrate for which ratios of stretching/bending stiffness (which depend on the diameter of filament) the inextensible model is accurate and more efficient. We show that our inextensible approach can be markedly more efficient than the extensible models for many biological filaments. We also compare the accuracy of the centerline distribution of the Stokeslets and rotlets to the more accurate surface distribution of Stokeslets for modeling fluid-structure interactions of filaments.

Analysis of a three-extensible-rod tracker based on 3-RPS parallel manipulator for space large deployable paraboloid structure with power and communication integration

The combination of a solar array and a communication antenna can reduce the entire mass, physical size, and cost in space applications. Currently, related studies mainly focus on the combination of the two structures on one flat plate structure (FPS). Compared with the FPS, a paraboloid structure has lower surface density and higher conversion efficiency. Therefore, the novel design of a space large deployable paraboloid structure with power and communication integration (SSPCI) is proposed for spacecraft on a sun synchronous earth orbit. A novel three-extensible-rod (TER) tracker is studied in detail for the SSPCI to track the sun for power in the sunshine region or turn to face the ground station for communication in the earth's shadow region. The proposed TER tracker includes three extensible rods, where one end of each rod is connected to the base platform by a rotary joint, and the other end is connected to the mobile platform by a smart compound joint as a substitute for a spherical joint; this is known in the literature as a 3-RPS parallel mechanism. In contrast to existing serial mechanisms, it provides a simple and lightweight structure, high structural stiffness, low inertia, and more accurate positioning and pointing of the mobile platform. Meanwhile, the linear extensible rods used in the TER tracker help to reduce energy consumption, and do not require the use of large and heavy speed reducers. A kinematic model of the TER tracker is also established. Based on this kinematic model, a dynamic model is then derived by using Newton–Euler formulation. The motion trajectory of the TER tracker is planned for the SSPCI to track the sun or turn to face the ground station. By setting related parameters, the workspace and pointing accuracy of the TER tracker are analyzed and found to be satisfactory for the SSPCI, and the motion process of tracking the sun or turning to face the ground station is simulated to test the theoretical analysis. The driving force and consumed energy of the TER tracker are obtained; the results shows that the TER tracker is able to drive the SSPCI to track the sun or turn to face the ground station with the aforementioned advantages and small energy consumption. By using finite element analysis, the SSPCI supported by the TER tracker is found to have satisfactory structural performance at different orientations in a zero gravity state. Meanwhile, the TER tracker has a satisfactory operation life and can adapt well to the space thermal environment. Finally, preliminary sun tracking experiments on the TER tracker are performed on the ground successfully, indirectly proving its feasibility of the TER tracker from the mechanism principle and control mode in space applications.

A novel ultralight dish system based on a three-extensible-rod solar tracker

The use of dish systems is among the most potential methods for solar power collection. However, the popularization of the application of traditional dish systems has been impeded because they are heavy, structurally complex, and costly. Accordingly, a novel ultralight dish system is proposed; it consists of a cable mesh reflector, an ultralight thermoelectric conversion device, and a three-extensible-rod (TER) solar tracker. Compared with previous reflectors consisting of rigid solid panels, the reflector of the proposed dish system (PDS) adopts an ultralight rigid–flexible combined structure based on a space cable mesh reflector antenna. The lightweight thermoelectric conversion device of the PDS is reasonably considered. Thereafter, a TER solar tracker (specifically, 3-RPS) is mainly selected and designed for the PDS. Through an inverse kinematic analysis of the tracker, a sun-tracking control strategy of height variation is employed to reduce the number of sections in each extensible rod from three to two and to decrease total energy consumption. Meanwhile, a compound joint consisting of hook and rotary joints is substituted for the spherical joint of the solar tracker to overcome its inadequate rotational range and facilitate fabrication. By setting the PDS to an extreme orientation and subjecting it to wind and gravitational loads, its structural parameters are further determined through analysis and optimization. Although the surface density of the PDS is only approximately 1 kg/m2, the system performs satisfactorily even when subjected to loads. The dynamic model of the PDS is established by the Newton–Euler formulation. The power requirement of the PDS is determined through the dynamic analysis; it is found that during winter solstice, its maximum power is only 0.024 W, and the daily energy consumption is only 210.05 J. Finally, sun-tracking experiments on the TER solar tracker are performed to verify the theoretical and simulation analysis results; the sun-tracking accuracy is estimated to be within ±0.7°, which satisfies the PDS requirement although the machining precision of its components is not high.