Kinematic Performance Research Articles

Tailoring Upper-Limb Robot-Aided Orthopedic Rehabilitation on Patients' Psychophysiological State.

Physical therapy keeps exploiting more and more the capabilities of the robot of adapting the treatments to patients' needs. This paper aims at presenting a psychophysiological-aware control strategy for upper limb robot-aided orthopedic rehabilitation. The main features are the capability of i) generating point-to-point trajectories inside an adaptable workspace, ii) providing assistance in guiding the patients' limbs in accomplishing the assigned task allowing them to freely move with a certain degree of spatial and temporal autonomy and iii) tuning the control parameters according to the patients' kinematics performance and psychophysiological state. The implemented control strategy is validated in a real clinical setting on eight orthopedic patients undergoing twenty daily robot-aided rehabilitation sessions. The psychophysiological-aware control strategy evidenced a positive impact on the enrolled participants since they are effectively conducted in a calmer condition with respect to the patients who did not receive the psychophysiological adaptation. Moreover, clinical performance indicators suggest that the proposed tailored control strategy improves motor functions.

On Forward Kinematics of a 3SPR Parallel Manipulator

This letter presents a new numerical method to solve the forward kinematics (FK) of a parallel manipulator with a three-limb spherical-prismatic-revolute (3SPR) structure. Unlike the existing numerical approaches that require the manipulator’s Jacobian matrix and its inverse at each iteration, the proposed algorithm requires much less complex computations to estimate the FK parameters. A cost function is introduced that measures the difference between actual FK values and its estimates. At each iteration, the problem is handled in two steps. First, the estimates of the platform orientation from the heave estimates are obtained. Then, the heave estimates are updated along the gradient direction of the proposed cost function. To evaluate the performance of the proposed algorithm, we compare results with those of a Jacobian-based (JB) approach for a 3SPR parallel manipulator.

On the Discrete Implementation of the Filtered Inverse Method for Serial Robots

In this paper, the filtered inverse algorithm for dynamic inversion of matrices is revisited and additional analysis regarding its discrete implementation and related gain limitations are presented. The method is used to provide a solution to the inverse kinematics of a serial redundant robot manipulator with 7-DoF for both position and orientation control. The theoretical results obtained and the performance of the discrete method are validated on a relevant robotics simulation environment that also incorporates visual perception components, such as an eye-in-hand camera and artificial markers.

Unsupervised Learning-based Analytical Inverse Kinematics for High-redundancy Mobile Manipulators

Redundant manipulators are of interest to the robotics community because they can perform additional tasks beyond the primary ones. Coupling them with a mobile platform increases the number of degrees of freedom (DOF) and allows them to perform more complex tasks in a larger workspace. However, the increase in the number of DOFs significantly complicates the establishment of the inverse kinematic model. Indeed, several joint configurations can be associated with a given end-effector (EE) pose. In this paper, we parameterize some joints of the mobile manipulator (MM) to transform it into a non-redundant counterpart by clustering its workspace and configuration space. Thus, conventional methods can be applied to derive the IK of the resulting non-redundant counterpart. A series of simulations validate the proposed approach.

STRUCTURAL SYNTHESIS OF SERIAL SPHERICAL MANIPULATORS

Serial manipulators are a serial of links connected by joints. The manipulator is called serial, because the drives of this manipulator are arranged in series, one after the other. Most often, the drives of the sequential manipulator are located on jointes or are coordinated with the joint. All links, the base, as well as the executive link, make up the kinematic chain of the manipulator. Serial manipulators have a large working area, it is much larger than the working area of parallel manipulators, which allows them to work with large parts, which undoubtedly increases the area in which the manipulator is capable of working. Mass-produced robots typically have six joints because at least six degrees of freedom are required to place a controlled object in an arbitrary position and orientation in the robot's workspace. The inverse kinematics of sequential manipulators with six rotary joints and with three consecutive intersecting joints can be solved in closed form, i.e. analytically This result had a huge impact on the design of industrial robots. This section provides a unified work for the calculation of the mobility and constraints in a general over constraint spherical manipulators based on spherical serial manipulator plus the different spherical structural groups with two, three and four classes. The results of the section can be considered by knowledges of structural groups with general constraint three constructed to the serial spherical manipulator with 3DoF. The 3DoF serial spherical manipulators represent as a series of 1DoF revolute joints with the axises intersecting in the center of sphere. Three illustrative examples showcasing the method are presented.

Functional evaluation of optimal index finger proximal interphalangeal joint fusion angle using a simulated joint arthrodesis

This study aims at qualitatively and quantitatively evaluating the effects of simulated index finger proximal interphalangeal (PIP) joint fusion angles on hand kinematic function and performance. Although arthrodesis of the index finger PIP joint is an effective medical procedure that produces a durable, pain-free, and stable joint, it permanently immobilizes the joint. Twenty healthy subjects performed basic functional hand activities with the index finger PIP joint unconstrained (UC) and constrained to selected angles under surveillance of a motion capture system. Our results indicate differences in perceived difficulty, time performance, and the functional ROM of the hand joints when the index finger PIP joint is UC and constrained to 0, 20, and 40 degrees of flexion. The mean total perceived difficulty scores for all 6 tasks were higher for the PIP at 0 degrees than for the UC condition (p < 0.001) and for the PIP at 40 degrees (p = 0.048). The functional ROM presented a smaller total number of hand joints affected by the PIP at 20 degrees (25 in total) than the PIP at 0 (31 in total) and 40 (27 in total) degrees during execution of all 6 tasks tested. Therefore, the decision on the appropriate index finger PIP angle for arthrodesis may be between 20 and 40 degrees, as globally for all 6 tasks tested, 0 degrees exhibited the worst results regarding perceived difficulty, performance time, and number of joints with affected ROM. Selecting the appropriate angle for arthrodesis should consider a more complete set of functional activities.

Methods of workspace generation for parallel kinematic manipulators

This paper presents the geometric, discretization and Monte Carlo method to generate the workspace for Parallel Kinematic Manipulators (PKMs). The geometric method does not require the solution to the inverse kinematics as opposed to the Monte Carlo and discretization methods. Each method possesses advantages and drawbacks concerning accuracy, time and ease of implementation. A case study concerning constant orientation workspace of a planar 3RRR PKM showed that the most efficient and accurate method was the geometric method but it also possessed the most limitations. The discretization and Monte Carlo methods produced the workspace with an accuracy of 92.49% and 95.67% respectively.

The implementation of an optical computer mouse as a low-cost displacement sensor

The accurate measurement of distance, position or displacement is a requirement in many robotics projects. This paper presents the investigation of a HP M-UAE96 optical mouse as a low-cost displacement sensor. Various resolutions were obtained on a Windows operating system in conjunction with MATLAB®. The Arduino IDE was used with a linear actuator module to accurately produce predetermined linear movements. The most suitable resolution was found to be 0.2 mm/pixel and was implemented on a parallel kinematic manipulator in a case study. Surface contact and length of measurement were significant factors that influenced measurement accuracy.

A Spatial Parallel Kinematic Manipulator with Nested Kinematic Chains and High Rotational Range

A Spatial Parallel Kinematic Manipulator with Nested Kinematic Chains and High Rotational Range

The Kinematics Performance of Self-Propelled Full Freedom Filament in Wakes of Flow around Cylinder

The Kinematics Performance of Self-Propelled Full Freedom Filament in Wakes of Flow around Cylinder

Corner smoothing for CNC machining of linear tool path: A review

Computer numerical control (CNC) machine tools are widely used in various industrial fields ranging from aerospace, automotive, ship building, and the die/mould to manufacture products. However, tool paths of most CNC machine tools are composed of a series of linear motion commands (G01), which will inevitably cause the discontinuity in curvature and feedrate at the junctions between adjacent linear tool path segments, deteriorating the surface quality with unfavorable marks and decreasing the machining efficiency. To solve this problem for obtaining the steady and continuous motions of machine tools, the local corners have to be smoothed. Generally, the existing corner smoothing methods can be classified as the global smoothing and the local corner smoothing, where the specially designed transition curves or the directly planned motion of machine tools are adopted to generate the geometrically corner-free tool path. Moreover, some new methods that focus on developing different transition or rounding strategies are also developed for further improving the kinematics performance of machine tools. In this paper, the recent advances and researches on corner smoothing methods are reviewed from different categories, and the conclusions, remaining challenges and future directions in corner smoothing are also presented.

INFLUÊNCIAS DA GINÁSTICA NA COMPOSIÇÃO CORPORAL E NA FUNÇÃO CARDIOPULMONAR DE ATLETAS

ABSTRACT Introduction: Aerobics is a recreational, ornamental, rhythmic, and expressive sport. It is widely used in physical education in colleges and universities because it is also believed that this sport benefits the cardiopulmonary function and the body composition of the practitioners. Objective: Study the influences of aerobic gymnastics on body composition and cardiopulmonary function in its practitioners. Methods: 40 college students volunteered for the research sample. The living conditions and learning level of the subjects were the same. The students were divided into two groups for research. There was no significant difference between the groups comparing the volunteers’ age, height, and weight. The high-load group performed exercises with a maximum heart rate of 220, while the low-load group performed the same protocol under a maximum heart rate of 195 beats per minute. The intervention took place over 40 and 60 minutes of exercise, respectively, for eight weeks. The POLAR monitor was used to check the kinematic performance of the athletes. The data were processed statistically. Results: Aerobic gymnastics influenced the body composition of college students with significant differences in bust circumference, waist, hip, thigh, and skinfold thickness (P&lt;0.05). The athletes' heart rate, pulmonary ventilation, and diastolic pressure increased significantly after aerobic gymnastics. The study showed that the resting heart rate of the volunteers decreased significantly after exercise, and their lung function returned to normal (P&lt;0.05). Conclusion: Aerobic exercise can improve the body composition, physiology, and cardiopulmonary function of its practitioners, and its greater encouragement in colleges and universities is recommended. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

TOPOLOGICAL STRUCTURE OPTIMIZATION AND KINEMATIC PERFORMANCE IMPROVEMENT OF 3-RRR PLANAR PARALLEL MANIPULATOR

The typical 3-RRR planar parallel manipulator with two translations and one rotation has extensive applications such as plane location and motion transfer. But it suffers two disadvantages. One is its analytical direct kinematics is difficult to be got and another is not input-output motion decoupled. This paper focuses on its topological structure optimization and resulting kinematic performance improvementt. First, the coupling degree of this manipulator is calculated being k=1. Second, based on structure coupling-reducing principle, its coupling-reduced manipulator with zero coupling degree is designed, which not only leads to be easy to get its analytic direct kinematic solutions, but also makes input-output motion partially decoupled. Moreover, based on workspace and singularity of this coupling-reduced manipulator, comprehensive comparison of two manipulators before and after coupling-reducing showed that the main performances of structure coupling-reduced manipulator are superior than that of the typical mechanism. The work shows that structure coupling-reducing is effective method for optimization of topology structure.

Kinematic modeling and analysis of transmission mechanism with joint clearance for flapping wing micro aerial vehicle

A theoretical model is built to reveal the effect of the joint clearance on the kinematic performance of the transmission mechanism of a flapping wing micro aerial vehicle (FWMAV). Massless link approach is used to model the joint clearance and the reciprocal screw is introduced to solve the kinematic model. Finite element method simulations are also performed to validate the model. The kinematic model reveals that the inertia force of the transmission mechanism contributes little to the flapping motion whereas the sign of the resultant moment of aerodynamic drag and wing inertia force plays decisive role. Besides, the joint clearance can either increase or decrease the flapping angle of the wing during a flapping period and it will significantly affect the flapping amplitude while involves little in the mean flapping angle. The effects of the positions of the joint with clearance and its magnitude on the flapping motion are also revealed.

Kinematic performance of micro-mobility vehicles during braking: experimental analysis and comparison between e-kick scooters and bikes

According to the Italian legislation, e-kick scooters and bikes are considered a single category of vehicles and can travel on the same infrastructures with the same rules; however, their kinematic behavior is very different.The adoption of a bike as a vehicle for covering short distances i.e., within 5 km is widely known both at the kinematic level and for its use by users. Conversely, e-kick scooters are "unknown" vehicles both for their kinematic characteristics and for their use by users. A handful of studies have shown how the behavior of e-kick scooters and bikes is very different; however, there are not many studies that analyze the different kinematic behavior of e-kick scooters and bikes. This study presents an experimental analysis that evaluates braking behavior by comparing e-kick scooters and traditional bikes according to several vehicle speeds.These analyzes help build a probabilistic mathematical model for estimating the stopping space of e-kick scooters and bikes. The availability of this model is crucial for the design of safe intersections between cycle paths and roads intended for motor vehicle traffic. Moreover, this model may reveal insights that could challenge the recent European regulations that equated e-kick scooters as bikes.

Multi-Objective Optimization of 1T2R Parallel Mechanisms Without Fixed Orientation Center and Axis Under the Influence of Parameter Perturbation

To track moving targets and signals in space, multiple characteristics as large orientational workspace and excellent kinematic performance are required for the satellite antenna driving mechanism. Due to variable orientational center and axes, the 3-RSR mechanism is capable of 1T2R with continuous workspace and becomes a promising solution for the satellite antenna driving mechanism. Influenced by the topological structure characteristics as none fixed orientation center and axes, the performances of 3-RSR mechanism are significantly impacted by the parameter perturbation. According to the differential mapping between finite screw and instantaneous screw, the structure, kinematics, performance, and optimization are unified under the FIS theory. To be applied for the satellite antenna driving mechanism, this paper carries out the multi-objective optimization of 3-RSR mechanism under the influence of parameter perturbation based on the FIS theory. Firstly, the orientational workspace is obtained by finite screw and the instantaneous motion description of the mechanism is derived through calculation principle of FIS theory. Secondly, the orientational workspace and kinematics indices of the mechanism are proposed towards the actual requirements of the satellite antenna driving, and the relationship with the parameters is established. The discrete operation becomes extremely complex owing to parameter perturbation, and the RSMs (response surface model) of indices without considering and considering parameter perturbation are modeled. The multi-objectives optimization of 3-RSR mechanism influenced by parameter perturbation is carried out and its Pareto frontier is obtained. Finally, a point preferred strategy is proposed and the optimum value of the parameter from Pareto frontier is selected.

Copebot: Underwater Soft Robot with Copepod-Like Locomotion.

It has been a great challenge to develop robots that are able to perform complex movement patterns with high speed and, simultaneously, high accuracy. Copepods are animals found in freshwater and saltwater habitats that can have extremely fast escape responses when a predator is sensed by performing explosive curved jumps. In this study, we present a design and build prototypes of a combustion-driven underwater soft robot, the "copebot," which, similar to copepods, is able to accurately reach nearby predefined locations in space within a single curved jump. Because of an improved thrust force transmission unit, causing a large initial acceleration peak (850 body length·s-2), the copebot is eight times faster than previous combustion-driven underwater soft robots, while able to perform a complete 360° rotation during the jump. Thrusts generated by the copebot are tested to quantitatively determine the actuation performance, and parametric studies are conducted to investigate the sensitivity of the kinematic performance of the copebot to the input parameters. We demonstrate the utility of our design by building a prototype that rapidly jumps out of the water, accurately lands on its feet on a small platform, wirelessly transmits data, and jumps back into the water. Our copebot design opens the way toward high-performance biomimetic robots for multifunctional applications.

A comprehensive evaluation framework for kinematic performance of parallel mechanisms based on joint transmissibility and multi-attribute decision making methods

The evaluation of kinematic transmission performance is one of the key elements of mechanism analysis and the foundation of optimal design, where performance indices related to motion and force transmission provide evaluation criteria for parallel mechanisms. The paper will focus on the two significant and challenging aspects of performance evaluation of parallel mechanisms: (1) presenting the generalized angle to evaluate the joint transmissibility and (2) establishing a systematic and complete multi-index comprehensive evaluation method (MICEM). Utilizing the transmission vector involving the transmissibility of all inputs and outputs, the general approaches to establishing multiple indices are further proposed to reveal performance presentations limited by a single index. Combing multiple indices and multi-attribute decision making (MADM) methods, the procedures including determining reasonable weights of the indices, screening appropriate indices, and aggregating those indices into a composite index are further developed to address the comprehensive evaluation problem. Moreover, the results of the comprehensive evaluation for a 3-RUU parallel mechanism verify the effectiveness and rationality of the new method. This work can also provide references for evaluation analysis and optimal design of different performance.

Overlap classification-based and kinematically coordinated corner rounding using double asymmetrical transitions for five-axis short-segmented tool path

For traditional corner rounding methods that adopt a pair of symmetrical and asymmetrical transition curves to round the corners in tool tip position and tool orientation, there are still two critical issues remain unsolved. One is the overlaps between adjacent transition curves have to be eliminated specifically to avoid the excessive approximation of the transition curves to the corners, the other is the asynchronous motions between tool tip position and tool orientation on the transition curves need to be addressed in addition to achieving smoothness at the junctions between transition curves and linear segments. For solving these two issues, this paper proposes the overlap classification-based and kinematically coordinated double asymmetrical transitions to round the corners. In this method, the overlaps between adjacent transition curves in tool tip position and tool orientation are first classified. Then, parameter synchronization is derived analytically and a targeted overlap elimination strategy is also proposed, so that the transition lengths without forcing the transition curves over-approach the corners are determined. Furthermore, to alleviate the asynchronous motions, the kinematics coordination between tool tip position and tool orientation is introduced, which is utilized to further evaluate the transition lengths to improve the kinematics performance of rotary axes. Finally, the computer simulations and machining experiment both demonstrate that our method can improve the feedrate and achieve the low acceleration and jerk of rotary axes indeed.

Parameter Optimization of Large-Size High-Speed Cam-Linkage Mechanism for Kinematic Performance

The cam-linkage mechanism is a typical transmission mechanism in mechanical science and is widely used in various automated production equipment. However, conventional modeling methods mainly focus on the design and dimensional synthesis of the cam-linkage mechanism in the slow-speed scenario. The influence of component dimensions is not taken into consideration. As a result, the model accuracy dramatically falls when analyzing large-size cam-linkage mechanisms, especially in high-speed environments. The kinematic aspects of cam design have been investigated, but there are few studies discussing the motion characteristic and accuracy analysis models of the large-size cam-linkage mechanism under high-speed scenarios. To handle such issues, this paper proposes a parameter optimization methodology for the design analysis of the large-size high-speed cam-linkage mechanism considering kinematic performance. Firstly, the mathematical model of the cam five-bar mechanism is presented. The cam curve and motion parameters are solved forward with linkage length and output speed. Then, a particle swarm-based multi-objective optimization method is developed to find the optimal structure parameters and output speed curve to minimize cam pressure angle and roller acceleration and maximize linkage mechanism drive angle. A Monte Carlo-based framework is put forward for the reliability and sensitivity analysis of kinematic accuracy. Finally, a transverse device of a sanitary product production line is provided to demonstrate the applicability of the proposed method. With the parameter optimization, the productivity of the transverse device is doubled, from 600 pieces per minute (PPM) to 1200 PPM.