Limited Joint Research Articles

Role of joint interactions in upper limb joint movements: a disability simulation study using wearable inertial sensors for 3D motion capture

BackgroundRestriction of movement at a joint due to disease or dysfunction can alter the range of motion (ROM) at other joints due to joint interactions. In this paper, we quantify the extent to which joint restrictions impact upper limb joint movements by conducting a disability simulation study that used wearable inertial sensors for three-dimensional (3D) motion capture.MethodsWe employed the Wearable Inertial Sensors for Exergames (WISE) system for assessing the ROM at the shoulder (flexion–extension, abduction–adduction, and internal–external rotation), elbow (flexion–extension), and forearm (pronation-supination). We recruited 20 healthy individuals to first perform instructed shoulder, elbow, and forearm movements without any external restrictions, and then perform the same movements with restriction braces placed to limit movement at the shoulder, elbow, and forearm, separately, to simulate disability. To quantify the extent to which a restriction at a non-instructed joint affected movement at an instructed joint, we computed average percentage reduction in ROM in the restricted versus unrestricted conditions. Moreover, we performed analysis of variance and post hoc Tukey tests (q statistic) to determine the statistical significance (p < 0.05 denoted using *) of the differences in ROM of an instructed joint in the unrestricted versus restricted conditions.ResultsRestricting movement at the shoulder led to a large reduction in the average ROM for elbow flexion–extension (21.93%, q = 9.34*) and restricting elbow movement significantly reduced the average ROM for shoulder flexion–extension (17.77%, q = 8.05*), shoulder abduction–adduction (19.80%, q = 7.60*), and forearm pronation-supination (14.04%, q = 4.96*). Finally, restricting the forearm significantly reduced the average ROM for shoulder internal–external rotation (16.71%, q = 3.81*) and elbow flexion–extension (10.01%, q = 4.27*).ConclusionsJoint interactions across non-instructed joints can reduce the ROM of instructed movements. Assessment of ROM in the real-world using 3D motion capture, for example using the WISE system, can aid in understanding movement limitations, informing interventions, and monitoring progress with rehabilitation.

Pemberian Terapi Latihan dan Edukasi dalam Upaya Meningkatkan Kemampuan Aktivitas Fungsional pada Lansia dengan Osteoarthritis Knee di Puskesmas Rampal Celaket

Osteoarthritis is a joint disorder that develops degeneratively due to chronic inflammation in the joint. Symptoms involve the gradual breakdown of cartilage, osteophyte formation, and changes in the synovial membrane. Osteoarthritis sufferers often experience a decrease in daily activities. In particular, Knee Osteoarthritis is the most common type of Osteoarthritis that causes joint pain and limitation of motion in the knee, characterized by damage to the joint cartilage and Diarthrodial structures. In order for people to prevent Osteoarthritis Knee, it is important to identify the risk factors that can lead to the condition. With this understanding, it is hoped that people can avoid the risk factors as part of prevention efforts. By distributing leaflets and conducting Knee Osteoarthritis examinations and daily activity evaluations on patients, the results showed an increase in functional activity in the elderly after undergoing routine exercise therapy. In conclusion, through this counseling activity, increasing public awareness, especially among the elderly, about the importance of preventing Osteoarthritis Knee. Continuous preventive and curative efforts are needed to reduce the incidence rate of Osteoarthritis Knee in the community.

The Spondylocarpotarsal Synostosis Syndrome Case with Ventricular Septal Defect Caused by a Homozygous Frameshift Variation in FLNB

AbstractSpondylocarpotarsal synostosis syndrome (SCT) (OMIM: 272460), an autosomal recessive disorder, is characterized by block vertebrae, carpal–tarsal synostosis, and disproportionate short stature. The clinical features of SCT include dysmorphic facial traits, cleft palate, hypoplastic tooth enamel, brachydactyly, clinodactyly, limited joint movement, and mixed hearing loss. SCT is associated with biallelic nonsense and frameshift pathogenic variants in the FLNB gene. An 8-year-old patient was referred with suspected skeletal dysplasia. The patient presented with short stature, scoliosis, carpal–tarsal synostosis, and ventricular septal defect (VSD). Clinical exome sequence analysis revealed a homozygous frameshift variation in the FLNB gene (c.219_222dup p.Met75Profs*17). No other pathogenic variations in genes related to VSD were found. This study aims to discuss novel clinical findings related to the genotype–phenotype association. To the best of our knowledge, this is the first reported case of SCT with VSD.

Point-based Models: A Unified Approach for Geometric Constraint Analysis of Planar N-Bar Mechanisms with Rotary, Sliding, and Rolling Joints

Abstract Kinematic simulation of planar n-bar mechanisms has been an intense topic of study for several decades now. However, a large majority of efforts have focused on position analysis of such mechanisms with limited links and joint types. This paper presents a novel, unified approach to analysis of geometric constraints of planar n-bar mechanisms with revolute joint (R-joint), prismatic joint (P-joint), and rolling joint. This work is motivated by a need to create and program a system of constraint equations, which deal with different types of joints in a unified way. A key feature of this work is that the rolling joint constraints are represented by four-point models, which enables us to use the well-established undirected graph rigidity analysis algorithms. As a result, mechanisms with an arbitrary combination of revolute-, prismatic-joints, and wheel/gear/wheel-belt chains without any limitations on their actuation, can be analyzed and simulated efficiently for potential implementation in an interactive computer software and large-scale data generation.

A joint acceleration planning method for inverse kinematics of manipulator based on second-order system with variable impedance

The paper presents an angular acceleration planning method for joint space of manipulator to achieve real-time tracking tasks under joint constraint. To improve the performance of the algorithm and ensure the joint limit, the proposed method establishes a Second-order System with Variable Impedance (SSVI). The Second-order System is introduced in the joint space through the joint angular acceleration in second derivative of kinematics. The impedance parameters vary with different states of joint and the variable impedance produced virtual repulsive force to ensure that the joint motions are within the specified ranges when they are close to limits. The damping impedance contained in the system can improve convergence speed and suppress system oscillation and vibration caused by factors such as the visual noise. Simulation and experiment results verify that the method is effective and has faster convergence speed and more smooth motion compared with other methods.

Transforming rehabilitation: A narrative review on reversible knee flexor contracture assistive devices

Abstract: Joint contracture, marked by restricted joint movement due to connective tissue and muscle shortening, is a common complication in chronic musculoskeletal conditions such as osteoarthritis, osteonecrosis, rheumatoid arthritis, healed septic joint, and postsurgical complications. This limitation adversely impacts joint mobility and flexibility, increasing the likelihood of physical constraints. Contractures elevate the risk of impaired self-care, limited physical mobility, and hindered social activities, emphasizing the critical need to manage such contractures. The study aims to find the most appropriate, effective, user-friendly mechanical device to treat reversible knee flexor contracture. Method of a literature review was conducted utilizing PubMed, Google Scholar, and the physiotherapy evidence database (PEDro) up to April 2023. The inclusion criteria comprised studies related to flexion contracture (FC), written in English languages were included. The literature searched using the terms “flexion contracture, hamstring contracture, knee flexor contracture, burn contracture, knee joint hypomobility, and devices for flexion contracture.” Result after applying the selection criteria, the initial screening of literature gives 35,400 results on Google Scholar, PubMed, and PEDro. Subsequently, 128 articles underwent screening based on abstract and full-text availability in the English language. Following this, seven articles were selected and thoroughly reviewed, which included randomized control trials, systematic reviews, and exploratory studies. The study concluded the use of conventional physiotherapy interventions, coupled with assistive devices, diminishes the burden on physiotherapists and provides effective improvements to patients with FCs.

Energy-Aware Hierarchical Control of Joint Velocities

Nowadays, robots are applied in dynamic environments. For a robust operation, the motion planning module must consider other tasks besides reaching a specified pose: (self) collision avoidance, joint limit avoidance, keeping an advantageous configuration, etc. Each task demands different joint control commands, which may counteract each other. We present a hierarchical control that, depending on the robot and environment state, determines online a suitable priority among those tasks. Thereby, the control command of a lower-prioritized task never hinders the control command of a higher-prioritized task. We ensure smooth control signals also during priority rearrangement. Our hierarchical control computes reference joint velocities. However, the underlying concepts of hierarchical control differ when using joint accelerations or joint torques as control signals instead. So, as a further contribution, we provide a comprehensive discussion on how joint velocity control, joint acceleration control, and joint torque control differ in hierarchical task control. We validate our formulation in an experiment on hardware.

EMSA-IK: a real-time evolutionary multi-objective semi-analytical inverse kinematics algorithm for redundant manipulators

Purpose This paper aims to propose a real-time evolutionary multi-objective semi-analytical inverse kinematics (IK) algorithm (EMSA-IK) for solving the multi-objective IK of redundant manipulators. Design/methodology/approach Within EMSA-IK, the parameterization method is applied to reduce the number of optimization variables of the evolutionary algorithm and calculate semi-analytical solutions that meet high target pose accuracy. The original evolutionary algorithm is improved with the proposed adaptive search sub-space strategy so that the improved evolutionary algorithm can be used to efficiently perform global search within the parametric joint space to obtain the global optimal parametric joint angles that satisfy multi-objective constraints. Findings Ablation experiments show the effectiveness of the improved strategy used for evolutionary algorithms. Comparative experiments on different manipulators demonstrate the advantages of EMSA-IK in terms of generalizability and balancing multiple objectives, for example, motion continuity, joint limits and obstacle avoidance. Real-world experiments further validate the effectiveness of the proposed algorithm for real-time application. Originality/value The semi-analytical IK solution that simultaneously satisfies high target pose accuracy and multi-objective constraints can be obtained in real time. Compared to existing semi-analytical IK algorithms, the proposed algorithm achieves obstacle avoidance for the first time. The proposed algorithm demonstrates superior generalizability, applicable to not only redundant manipulators with revolute joints but also those with prismatic joints.

Efficacy of tissue-bone homeostasis manipulation on the gait and knee function for the patients with knee osteoarthritis: a randomized controlled trial.

Knee osteoarthritis (KOA) was characterized by pain and limited joint function, which seriously affected the quality of life of patients. The vast majority of KOA was closely related to degeneration of the patellofemoral joint and abnormal patellar movement trajectory. Tissue-bone homeostasis manipulation (TBHM) could correct abnormal patellar movement trajectory on the basis of loosening soft tissue. However, there was little strong evidence to verify its efficacy on the patients with KOA. The study objective was to explore the efficacy of the TBHM on gait and knee function in the patients with KOA. Sixty KOA patients were randomly assigned to either the joint mobilization (n = 30) or TBHM (n = 30) group. The joint mobilization group received joint mobilization, while the TBHM group received TBHM. For two groups, the patients participated in 30min rehabilitation sessions thrice per week for 12weeks. The primary outcome was biomechanical gait outcomes during walking, including step length, step velocity, double support, knee range of motion (ROM), and knee adduction moment (KAM). The secondary outcomes were the Western Ontario and McMaster Index (WOMAC) and 36-Item short- form health survey (SF-36), which reflected improvements in knee function and quality of life, respectively. At baseline and 12weeks, evaluations were conducted and compared between groups. After a 12-week intervention, significant group differences were observed in KAM (p = 0.018), WOMAC-Pain (p = 0.043) and WOMAC-Stiffness (p = 0.026). A noteworthy finding was the presence of a significant interaction effect between group and time specifically observed in step velocity during gait (p = 0.046), WOMAC-Function (p = 0.013) and SF-36 (p = 0.027). Further analysis revealed a significant difference in step velocity (p = 0.034), WOMAC-Function (p = 0.025) and SF-36 (p = 0.042) during post-assessment between the two groups. Moreover, a significant time effect was observed across all outcomes of the two groups (p < 0.05). The TBHM intervention has better improved the gait, knee function, and quality of life in the patients with KOA. ITMCTR, ITMCTR2200005507. Registered 06/01/2022, http://itmctr.ccebtcm.org.cn/zh-CN/Home/ProjectView?pid=09cdadad-0aef-41ee-81bd-a8dceb63f7f5 .

Effectiveness of resistance training of masticatory muscles for patients with temporomandibular disorders: protocol for a systematic review

IntroductionTemporomandibular disorders (TMDs) are musculoskeletal disorders characterised by jaw pain and typically temporomandibular joint limitations. Resistance training (RT) has been shown to be effective at reducing pain and improving function...

Effects of physical and psychological multimorbidity on the risk of dementia: multinational prospective cohorts and a meta-analysis

BackgroundPrevious studies only considered the impact of a single physical or psychological disorder on dementia. Our study investigated the association of physical and psychological multimorbidity with dementia among older adults using two multinational prospective cohorts to supplement the limited joint evidence.MethodsWe utilized the Health and Retirement Study (HRS 2012 to 2018) in the United States (US) and the Survey of Health, Ageing and Retirement in Europe (SHARE 2012 to 2018). Physical disorder was defined as any one of seven self-reported physician-diagnosed conditions. Psychological disorder was assessed using the 8-item Center for Epidemiologic Research Depression (CES-D) scale or the EURO-D. Dementia was determined through a combination of self-reported physician diagnosis of dementia or Alzheimer’s disease, or the 27-point HRS cognitive scale. Competing risk models were utilized to estimate the hazard ratios (HRs) and 95% confidence intervals (95% CI). DerSimonian-Laird random-effects meta-analyses were conducted to obtain pooled estimates.ResultsThe prevalence of physical and psychological multimorbidity was 17.29% (1027/5939) in continental Europe and 15.52% (1326/8543) in the US. The incidence of dementia was 6.21 per 1000 person-years in continental Europe and 8.27 per 1000 person-years in the US, respectively. It was highest among participants with physical and psychological multimorbidity in continental Europe (10.46 per 1000 person-years) and the US (14.82 per 1000 person-years), compared with the other three groups. In the univariate model, participants who reported physical and psychological multimorbidity had a higher risk of dementia compared with those who reported no physical and psychological disorders in continental Europe (HR = 2.59; 95% CI: 1.55, 4.33) and the US (HR = 4.11; 95% CI: 2.44, 6.94). After adjusting all covariates, the risk of dementia among participants who reported physical and psychological multimorbidity increased by 86% in continental Europe (aHR = 1.86; 95% CI: 1.08, 3.21) and by 176% in the US (aHR = 2.76; 95% CI: 1.61, 4.72), respectively. After pooling the outcomes, the risk of dementia among participants who reported physical and psychological multimorbidity increased by 115% (aHR = 2.15; 95% CI: 1.27, 3.03).ConclusionsPhysical and psychological multimorbidity was prevalent among older adults in the US and continental Europe. Given the consistent associations with dementia, it is imperative to increase awareness of the links and recognize the limitations of single-disorder care. Specific attention should be given to providing care coordination.

Bi-stochastically normalized graph Laplacian: convergence to manifold Laplacian and robustness to outlier noise.

Bi-stochastic normalization provides an alternative normalization of graph Laplacians in graph-based data analysis and can be computed efficiently by Sinkhorn-Knopp (SK) iterations. This paper proves the convergence of bi-stochastically normalized graph Laplacian to manifold (weighted-)Laplacian with rates, when [Formula: see text] data points are i.i.d. sampled from a general [Formula: see text]-dimensional manifold embedded in a possibly high-dimensional space. Under certain joint limit of [Formula: see text] and kernel bandwidth [Formula: see text], the point-wise convergence rate of the graph Laplacian operator (under 2-norm) is proved to be [Formula: see text] at finite large [Formula: see text] up to log factors, achieved at the scaling of [Formula: see text]. When the manifold data are corrupted by outlier noise, we theoretically prove the graph Laplacian point-wise consistency which matches the rate for clean manifold data plus an additional term proportional to the boundedness of the inner-products of the noise vectors among themselves and with data vectors. Motivated by our analysis, which suggests that not exact bi-stochastic normalization but an approximate one will achieve the same consistency rate, we propose an approximate and constrained matrix scaling problem that can be solved by SK iterations with early termination. Numerical experiments support our theoretical results and show the robustness of bi-stochastically normalized graph Laplacian to high-dimensional outlier noise.

Promising clinical effect of arthroscopic autologous iliac bone grafting with suture anchor binding fixation for recurrent anterior shoulder instability.

To evaluate the clinical efficacy of arthroscopic autologous iliac bone grafting with suture anchor binding fixation combined with a Bankart repair for recurrent anterior shoulder dislocation with a significant anterior glenoid defect. Patients with recurrent anterior shoulder dislocation with an anterior glenoid defect area greater than 20% admitted to our department from March 2019 to March 2022 were prospectively enrolled. Arthroscopic autologous iliac bone grafting with suture anchor binding fixation combined with a Bankart repair was performed. Computed tomography (CT) images were captured preoperatively, immediately after surgery, and at 3, 6, and 12 months postoperatively to evaluate the glenoid defect area, graft area, and graft healing. Shoulder function was assessed using the Instability Severity Index, Oxford Shoulder Instability, and Rowe scores recorded preoperatively and at the final follow-up. The shoulder range of motion, shoulder stability test, surgery-related complications, subluxation/dislocation, and revision surgery were also evaluated. A total of 32 patients were included in the study, with an average follow-up time of 18.3 ± 6.3 months, when the graft healing rate was shown to be 100%. The area ratio of the graft to the glenoid was 37.6% ± 10.5% (range, 23.5%-44.1%) determined by an enface-view three-dimensional CT performed immediately after surgery, and 29.2 ± 8.2% (range, 19.6%-38.7%) at 12 months postoperatively. At the final follow-up, the glenoid defect had improved from 28.7 ± 6.4% (range, 20.5%-40.6%) before surgery to -10.2 ± 4.7% (range, -13.8% to 6.1%). The preoperative Rowe and Oxford scores were 56.4 ± 8.5 and 34.7 ± 7.1 respectively, which improved to 94.3 ± 6.7 and 15.3 ± 3.2 at the final follow-up (p < .001). All patients had no limited shoulder joint activity, no re-dislocation or revision surgery, and no neurovascular injury. For recurrent anterior shoulder dislocation with an anterior glenoid defect area greater than 20%, arthroscopic autologous iliac bone grafting with suture anchor fixation combined with a Bankart repair produced a promising clinical effect. A significant shoulder function score was achieved, as was a 100% bone healing rate and ideal glenoid reconstruction without major complications. Thus, this technique may be considered an alternative to the classic Latarjet approach to treat recurrent anterior shoulder dislocation with an anterior glenoid defect area greater than 20%. IV.

Control barrier function based visual servoing for Mobile Manipulator Systems under functional limitations

This paper proposes a new control strategy for Mobile Manipulator Systems (MMSs) that integrates image-based visual servoing (IBVS) to address operational limitations and safety constraints. The proposed approach based on the concept of control barrier functions (CBFs), provides a solution to address various operational challenges including visibility constraints, manipulator joint limits, predefined system velocity bounds, and system dynamic uncertainties. The proposed control strategy is a two-tiered structure, wherein the first level, a CBF-IBVS controller calculates control commands, taking into account the Field of View (FoV) constraints. By leveraging null space techniques, these commands are transposed to the joint-level configuration of the MMS, while considering system operational limits. Subsequently, in the second level, a CBF velocity controller employed for the entire MMS undertakes the tracking of the commands at the joint level, ensuring compliance with the predefined system’s velocity limitations as well as the safety of the whole combined system dynamics. The proposed control strategy offers superior transient and steady-state responses and heightened resilience to disturbances and modeling uncertainties. Furthermore, due to its low computational complexity, it can be easily implemented on an onboard computing system, facilitating real-time operation. The proposed strategy’s effectiveness is illustrated via simulation outcomes, which reveal enhanced performance and system safety compared to conventional IBVS methods. The results indicate that the proposed approach is effective in addressing the challenging operational limitations and safety constraints of mobile manipulator systems, making it suitable for practical applications.

New probe of non-Gaussianities with primordial black hole induced gravitational waves

We propose a new probe of primordial non-Gaussianities (NGs) through the observation of gravitational waves (GWs) induced by ultra-light (MPBH<109g) primordial black holes (PBHs). Interestingly enough, the existence of primordial NG can leave imprints on the clustering properties of PBHs and the spectral shape of induced GW signals. Focusing on a scale-dependent local-type NG, we identify a distinct double-peaked GW energy spectrum that, contingent upon MPBH and the abundance of PBHs at the time of formation, denoted as ΩPBH,f, may fall into the frequency bands of upcoming GW observatories, including LISA, ET, SKA, and BBO. Thus, such a signal can serve as a novel portal for probing primordial NGs. Intriguingly, combining BBN bounds on the GW amplitude, we find for the first time the joint limit on the product of the effective non-linearity parameter for the primordial tri-spectrum, denoted by τ¯NL, and the primordial curvature perturbation power spectrum PR(k), which reads as τ¯NLPR(k)<4×10−20ΩPBH,f−17/9(MPBH104g)−17/9.

EFFECTIVENESS OF PASSIVE STRETCHING IN TREATING JUVENILE IDIOPATHIC RHEUMATOID ARTHRITIS- A CASE STUDY

Background:Rheumatoid Arthritis (RA) a systemic autoimmune disease characterized by inflammatory arthritis and extra-articular involvement. It is a chronic inflammatory disease that mostly affects the synovial joints.A diverse subset of idiopathic inflammatory arthritis that affects children under 16 and lasts for six weeks or more is known as juvenile idiopathic arthritis (JIA). Methodology:A 15-year-old female had juvenile idiopathic arthritis with medical treatment, there was no reduction of pain and led to difficulties in her ADL with restricted joint mobility and reduced ROM. Whereas she was evaluated and treated with specific physiotherapeutic measures for eight months period seven days in a week with specific stretching exercises. Result:The significant difference were reported from the pre and post test values of pain and also functional improvement with regards to kartz index Conclusion: Passive stretching, when implemented as part of a comprehensive physiotherapeutic approach, can effectively alleviate the symptoms and improve the quality of life.

Shoulder Joint Range of Motion Related to Dementia

Introduction: Dementia is caused by various diseases, including Alzheimer’s disease dementia (ADD) and dementia with Lewy bodies (DLB). We often encounter patients with dementia who have limited shoulder joint range of motion (ROM), especially those with behavioral and psychological symptoms of dementia (BPSD). But the relationship between the diseases of dementia and restricted shoulder joint ROM is currently unclear. Methods: We examined cognitive function and shoulder joint ROM in 234 new outpatients at 7 memory clinics in Japan. We assessed cognitive function using the Mini-Mental State Examination (MMSE) and Revised Hasegawa Dementia Scale (HDS-R) and BPSD using the Neuropsychiatric Inventory Questionnaire (NPI-Q). Patients were categorized by dementia diagnosis (ADD, DLB, other dementia, and control). Right, left, and total shoulder joint ROM was assessed using validated the Japanese Orthopaedic Association (JOA) score. Results: We found significant associations of lower right, left, and total shoulder joint ROM scores with male sex, advanced age, higher NPI-Q score, lower HDS-R, and MMSE scores. Little difference was found between right and left shoulder joint ROM scores. Restricted shoulder joint ROM was related to serial 7, verbal frequency domain scores on the HDS-R and repeat score on the MMSE. It was also related to the hallucinations, irritability/lability and nighttime disturbances scores on the NPI-Q. Furthermore, the dementia groups, especially the DLB group, showed worse shoulder joint ROM than the control group. Conclusions: Dementia was significantly related to restricted shoulder joint ROM. Maintaining communication and social interaction may help maintain shoulder joint ROM.

Supraspinal Activation Induced by Visual Kinesthetic Illusion Modulates Spinal Excitability.

Repetitive passive movement (RPM) enhances reciprocal inhibition. RPM is more effective when performed rapidly and at wide joint angles. However, patients with limited joint range of motion may not receive the most effective RPM. Therefore, having an alternative method for performing RPM in patients who cannot perform actual exercise due to limited joint motion is necessary. This study investigated the effects of RPM on spinal excitability using a visual kinesthetic illusion. Participants included 17 healthy adults (7 women). Measurements were taken before, during, and immediately after the intervention. We established two intervention conditions: the control condition, in which participants focused their attention forward, and the illusion condition, in which participants watched a video about RPM. F-waves from the tibialis anterior and soleus muscles were measured, and F-wave persistence and F/M amplitude ratios were analyzed. Under the illusion condition, compared with the preintervention condition, the F/M amplitude ratio of the tibialis anterior increased by approximately 44% during the intervention (p < 0.05), whereas the F-wave persistence of the soleus decreased by approximately 23% from the immediate start of the intervention (p < 0.05). This study suggests that a visual kinesthetic illusion can increase the spinal excitability of the tibialis anterior, whereas reciprocal inhibition can decrease the spinal excitability of the soleus.

Human-redundant robot interaction and redundancy utilization based on three-dimensional force sensor

To make full use of redundant characteristics, the inverse kinematics algorithm based on augmented Jacobian matrix with the goal of avoiding joint limit and obstacle is adopted. Then, admittance control system is established for human-robot interaction, and force control is converted into motion control of robot. Through the expansion of Jacobian matrix, the model of joint limit avoidance is established. Regarding obstacle avoidance in human-robot interaction process, the potential function gradient is calculated and augmented Jacobian matrix is formed. Thus, comprehensive control model of human-robot interaction and obstacle avoidance is established. When the external force is applied, the robot can move smoothly along the human hand. The robot's motion process is smooth and compliant. At the same time, when performing task of avoiding joint limit, the values of the joint angle are within the set range. The average angle margin of the four joints is over 60 %. So the goal of avoiding the joint limit is achieved. When adding obstacle avoidance in the interaction control, the difference value between the minimum distance and safe distance is always positive. The safety margin of the distance is over 20 %. So the robot does not contact with the obstacle. So human-robot interaction and redundancy utilization can be realized simultaneously.

Reconciling Tracking Error Volatility and Value-at-Risk in Active Portfolio Management: A New Frontier

AbstractThis article introduces the Risk Balancing Frontier (RBF), a new portfolio boundary in the absolute risk-total return space: the RBF arises when two risk indicators, the Tracking Error Volatility (TEV) and the Value-at-Risk (VaR), are both constrained not to exceed pre-set maximum values. By focusing on the trade-off between the joint restrictions on the two risk indicators, this frontier is the set of all portfolios characterized by the minimum VaR attainable for each TEV level. First, the RBF is defined analytically and its mathematical properties are discussed: we show its connection with the Constrained Tracking Error Volatility Frontier (Jorion in Financ Anal J, 59(5):70–82, 2003. https://doi.org/10.2469/faj.v59.n5.2565) and the Constrained Value-at-Risk Frontier (Alexander and Baptista in J Econ Dyn Control, 32(3):779–820, 2008. https://doi.org/10.1016/j.jedc.2007.03.005) frontiers. Next, we explore computational issues implied with its construction, and we develop a fast and accurate algorithm to this aim. Finally, we perform an empirical example and consider its relevance in the context of applied finance: we show that the RBF provides a useful tool to investigate and solve potential agency problems.