Analysis of Kinematics and Design of Structure Parameters for a Bionic Parallel Leg

2014 ◽  
Vol 20 ◽  
pp. 23-33 ◽  
Author(s):  
Bing Yan Cui ◽  
Li Wen Chen
Keyword(s):  
Structural Parameters ◽  
Structure Parameters ◽  
Parallel Mechanisms ◽  
Kinematics Analysis ◽  
Transmission Performance ◽  
Compact Structure ◽  
Evaluation Indexes ◽  
Performance Indexes ◽  
Performance Atlas ◽  
Moving Platform

This paper proposed a novel bionic walking leg which has three branches of 6-DOF, using 3-UPS parallel mechanism as the prototype, it has good advantage of compact structure and strong bearing capacity. Kinematics research of mechanism is very important, the dynamic analysis and the design are based on kinematics analysis. And the kinematics performance of the bionic walking leg is analyzed and the structure parameters are optimized. First, the kinematics transmission equation of the bionic walking leg is established, and using the norm theory the kinematics performance evaluation indexes are defined, and kinematics characteristics are analyzed. Then, application space model theory the structure parameters of the bionic walking leg are designed, and using of the Monte Carlo parameters selecting method based on the global kinematics performance atlas, the optimal structural parameters are given. Analysis results show that kinematics transmission performance indexes display the symmetric distribution of the bionic walking leg, the static platform radius is 120mm, moving platform radius is 50mm, and the height of the static platform and moving platform initial posture is 700mm. Finally, using the optimal structural size parameters, the virtual prototype of the bionic walking leg is designed. So,it has very important significances of theory and engineering to study and open out parallel mechanisms as the leg mechanisms of bionic walking legs.

A serial of novel four degrees of freedom parallel mechanisms with large rotational workspace

Robotica ◽  
2014 ◽  
Vol 34 (4) ◽  
pp. 764-776 ◽  
Author(s):  
Sheng Guo ◽  
Wei Ye ◽  
Haibo Qu ◽  
Dan Zhang ◽  
Yuefa Fang
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Planetary Gear ◽  
Gear Train ◽  
Parallel Mechanisms ◽  
Kinematics Analysis ◽  
Kinematic Chains ◽  
Moving Platform ◽  
Partition Method

SUMMARYIn this paper, a class of novel four Degrees of Freedom (DOF) non-overconstrained parallel mechanisms with large rotational workspace is presented based on screw theory. First, the conflict between the number of independent constraints applied on the moving platform and the number of kinematic limbs for 4-DOF non-overconstrained parallel mechanism is identified. To solve this conflict, the platform partition method is introduced, and two secondary platforms are employed in each of the parallel mechanisms. Then, the motion requirements of the secondary platforms are analyzed and all the possible kinematic chains are enumerated. The geometrical assembly conditions of all possible secondary limbs are analyzed and some typical non-overconstrained parallel mechanisms are generated. In each of the parallel mechanisms, a planetary gear train is used to connect both of the secondary platforms. The large rotational workspace of the moving platform is obtained due to the relative motion of the two secondary platforms. Finally, the kinematics analysis of a typical parallel mechanism is conducted.

Statics Analysis and Design of the 6-DOF Lower Limb Bionic Leg

2016 ◽  
Vol 26 ◽  
pp. 1-12 ◽  
Author(s):  
Li Wen Chen ◽  
Bing Yan Cui ◽  
Zhi Jun Wang ◽  
Ling Chao Meng ◽  
Zhan Xian Li
Keyword(s):  
Performance Evaluation ◽  
Carrying Capacity ◽  
Lower Limb ◽  
Evaluation Index ◽  
Structure Parameters ◽  
Transmission Performance ◽  
Analysis And Design ◽  
Static Performance ◽  
Performance Evaluation Index ◽  
Moving Platform

In order to improve ability of walking and crossing the barriers , increase the carrying capacity, and enhance its popularity and adaptability, a novel lower limb bionic leg is presented based on 3-UPS parallel mechanism, which has the characteristics of movement flexible and strong adaptability. It is very important analysis to statics of lower limb bionic leg. Firstly, statics equation of the lower limb bionic leg of driving force and output force is established based on virtual work principle. Secondly, static performance evaluation index is defined and the evaluation index distribution map is drawn. The relationship between the structure parameters and the static performance evaluation indexes is analyzed, obtained the influence of structure parameters on the static performance evaluation index, and a set of reasonable structural parameters is selected. The circum-radius of moving platform is 50mm, the circum-radius of the static platform is 150mm, the moving platform angle and static platform angle are equal to 60°, the lower limb bionic leg has the best load carrying capacity. Thirdly, the lower limb bionic leg is designed based on statics analysis and structure parameters optimization. Analysis results show that the lower limb bionic leg has good static transmission performance at the initial position, and the static transmission performance decreases with increasing turning workspace. The static transmission performance decreases with z axle displacement increasing. The analysis results laid a foundation for further analysis and research of the lower limb bionic leg.

scholarly journals A New Method for Type Synthesis of 2R1T and 2T1R 3-DOF Redundant Actuated Parallel Mechanisms with Closed Loop Units

2020 ◽  
Vol 33 (1) ◽  
Author(s):  
Yongquan Li ◽  
Yang Zhang ◽  
Lijie Zhang
Keyword(s):  
Closed Loop ◽  
Screw Theory ◽  
Line Graph ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Allocation Criteria ◽  
Grassmann Line Geometry ◽  
Moving Platform ◽  
Atlas Method

Abstract The current type synthesis of the redundant actuated parallel mechanisms is adding active-actuated kinematic branches on the basis of the traditional parallel mechanisms, or using screw theory to perform multiple getting intersection and union to complete type synthesis. The number of redundant parallel mechanisms obtained by these two methods is limited. In this paper, based on Grassmann line geometry and Atlas method, a novel and effective method for type synthesis of redundant actuated parallel mechanisms (PMs) with closed-loop units is proposed. Firstly, the degree of freedom (DOF) and constraint line graph of the moving platform are determined successively, and redundant lines are added in constraint line graph to obtain the redundant constraint line graph and their equivalent line graph, and a branch constraint allocation scheme is formulated based on the allocation criteria. Secondly, a scheme is selected and redundant lines are added in the branch chains DOF graph to construct the redundant actuated branch chains with closed-loop units. Finally, the branch chains that meet the requirements of branch chains configuration criteria and F&C (degree of freedom & constraint) line graph are assembled. In this paper, two types of 2 rotational and 1 translational (2R1T) redundant actuated parallel mechanisms and one type of 2 translational and 1 rotational (2T1R) redundant actuated parallel mechanisms with few branches and closed-loop units were taken as examples, and 238, 92 and 15 new configurations were synthesized. All the mechanisms contain closed-loop units, and the mechanisms and the actuators both have good symmetry. Therefore, all the mechanisms have excellent comprehensive performance, in which the two rotational DOFs of the moving platform of 2R1T redundant actuated parallel mechanism can be independently controlled. The instantaneous analysis shows that all mechanisms are not instantaneous, which proves the feasibility and practicability of the method.

scholarly journals A Novel Method for the Micro-Clearance Measurement of a Precision Spherical Joint Based on a Spherical Differential Capacitive Sensor

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3366 ◽  
Author(s):  
Wen Wang ◽  
He Yang ◽  
Min Zhang ◽  
Zhanfeng Chen ◽  
Guang Shi ◽  
...  
Keyword(s):  
Capacitive Sensor ◽  
Differential Capacitance ◽  
Industrial Robots ◽  
Parallel Mechanisms ◽  
Spherical Joint ◽  
Compact Structure ◽  
Spacing Variation ◽  
Novel Method ◽  
The Mathematical Model ◽  
Fringe Effect

A spherical joint is a commonly used mechanical hinge with the advantages of compact structure and good flexibility, and it becomes a key component in many types of equipment, such as parallel mechanisms, industrial robots, and automobiles. Real-time detection of a precision spherical joint clearance is of great significance in analyzing the motion errors of mechanical systems and improving the transmission accuracy. This paper presents a novel method for the micro-clearance measurement with a spherical differential capacitive sensor (SDCS). First, the structure and layout of the spherical capacitive plates were designed according to the measuring principle of capacitive sensors with spacing variation. Then, the mathematical model for the spatial eccentric displacements of the ball and the differential capacitance was established. In addition, equipotential guard rings were used to attenuate the fringe effect on the measurement accuracy. Finally, a simulation with Ansoft Maxwell software was carried out to calculate the capacitance values of the spherical capacitors at different eccentric displacements. Simulation results indicated that the proposed method based on SDCS was feasible and effective for the micro-clearance measurement of the precision spherical joints with small eccentricity.

WRENCH-CLOSURE WORKSPACE OF SIX-DOF PARALLEL MECHANISMS DRIVEN BY 7 CABLES

2005 ◽  
Vol 29 (4) ◽  
pp. 541-552 ◽  
Author(s):  
Marc Gouttefarde ◽  
Clément M. Gosselin
Keyword(s):  
Cross Sections ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Six Dof ◽  
Moving Platform ◽  
Six Degree Of Freedom

The wrench-closure workspace (WCW) of six-degree-of-freedom (DOF) parallel cable-driven mechanisms is defined as the set of poses of the moving platform of the mechanism for which any external wrench can be balanced by tension forces in the cables. This workspace is fundamental in order to analyze and design parallel cable-driven mechanisms. This paper deals with the class of six-DOF mechanisms driven by seven cables. Two theorems, which provide efficient means to test whether a given pose of the moving platform belongs to the WCW, are proposed. One of these two theorems reveals the nature of the boundary of the constant-orientation cross sections of the WCW. Moreover, some of the possible applications of these theorems are discussed and illustrated.

scholarly journals Reconfiguration Analysis of a 3-DOF Parallel Mechanism

Robotics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 66
Author(s):  
Maurizio Ruggiu ◽  
Xianwen Kong
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Operation Mode ◽  
Parallel Mechanisms ◽  
Universal Joint ◽  
Kinematic Chains ◽  
Constraint Equations ◽  
The Third ◽  
Equilateral Triangles ◽  
Moving Platform

This paper deals with the reconfiguration analysis of a 3-DOF (degrees-of-freedom) parallel manipulator (PM) which belongs to the cylindrical parallel mechanisms family. The PM is composed of a base and a moving platform shaped as equilateral triangles connected by three serial kinematic chains (legs). Two legs are composed of two universal (U) joints connected by a prismatic (P) joint. The third leg is composed of a revolute (R) joint connected to the base, a prismatic joint and universal joint in sequence. A set of constraint equations of the 1-RPU−2-UPU PM is derived and solved in terms of the Euler parameter quaternion (a.k.a. Euler-Rodrigues quaternion) representing the orientation of the moving platform and of the Cartesian coordinates of the reference point on the moving platform. It is found that the PM may undergo either the 3-DOF PPR or the 3-DOF planar operation mode only when the base and the moving platform are identical. The transition configuration between the operation modes is also identified.

Task-Based Knee Rehabilitation With Assist-as-Needed Control Strategy and Recovery Tracking System

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Yimesker Yihun ◽  
Visharath Adhikari ◽  
Amirhossein Majidirad ◽  
Jaydip Desai
Keyword(s):  
Motion Capture ◽  
Control Strategy ◽  
Structural Parameters ◽  
Tracking System ◽  
Three Dimensional ◽  
Parallel Mechanisms ◽  
Emg Signal ◽  
Knee Rehabilitation ◽  
Synthesis Procedure ◽  
Serial Chains

Abstract This research aims to design and implement a novel task-based knee rehabilitation strategy through kinematic synthesis, assist-as-needed control strategy, and recovery tracking system. Experimental kinematic data collected through motion capture system are utilized as an input to the mechanism synthesis procedure. Parallel mechanisms with single degree-of-freedom are considered to generate the complex three-dimensional (3D) motions of the lower leg. An exact workspace synthesis approach is utilized, in which the implicit description of the workspace is made to be a function of the structural parameters of the serial chains of the parallel mechanism, making it easy to relate those parameters to the desired trajectory from the motion capture. The synthesis procedure resulted an exoskeleton which can guide the complex motion of the human knee without the need of mimicking the joint by the exoskeleton counterpart. This can potentially reduce the improper alignment problems arising due to the constantly varying axis of rotation of human joint, which is often very difficult to predict. An assist-as-needed control and recovery tracking strategy is outlined based on an electromyography (EMG) signals and force sensing resistors (FSRs) mounted on the user and exoskeleton, respectively. The EMG signal is captured from the user leg and FSRs are applied at the attachment area of the exoskeleton and the leg, this helps to get the amount of force applied by the exoskeleton to the leg as well as for the recovery tracking. The assist-as-needed controller eliminates the need of constant supervision, and hence saves time and reduces cost of the rehabilitation process. Similarly, the real-time progress tracking system will motivate and actively engage users

scholarly journals Research on three-stage amplified compliant mechanism-based piezo-driven microgripper

2020 ◽  
Vol 12 (3) ◽  
pp. 168781402091147 ◽  
Author(s):  
Xiaodong Chen ◽  
Zilong Deng ◽  
Siya Hu ◽  
Xingjun Gao ◽  
Jinhai Gao
Keyword(s):  
Amplification Factor ◽  
Compliant Mechanism ◽  
Structural Parameters ◽  
Maximum Output ◽  
Driving Voltage ◽  
Element Analysis ◽  
Compact Structure ◽  
Output Displacement ◽  
Amplification Ratio ◽  
Input Variables

The microgripper based on the principle of lever amplification is easy to realize; however, the theoretical amplification factor is limited by the space size and the structure is not compact enough. The microgripper based on the triangular amplification principle has a compact structure and high amplification factor, but it is not conducive to miniaturization design. Considering compactness, parallel clamping, high magnification, and miniaturization design, a three-stage amplifier consisting of a semi-rhombic amplifier and lever amplifiers is designed. To begin with, the theoretical amplification ratio and the relationship between input variables and output variables are calculated by energy method. Furthermore, the finite element analysis software is used to optimize the structural parameters and analyze the performance of the model. Lastly, the experimental verification is carried out. At 150 V of driving voltage, the maximum output displacement was 530mm, and the actual magnification was 24 times. Microparts can be gripped in parallel and stably, which confirms the validity of the design.

scholarly journals Forward kinematic analysis of a 3-RRRS mechanism with subordinate driving variables using a computer-aided geometric method

2019 ◽  
Vol 16 (4) ◽  
pp. 172988141987066
Author(s):  
Liangwen Wang ◽  
Tuanhui Wang ◽  
Fannian Meng ◽  
Wenliao Du ◽  
Caidong Wang ◽  
...  
Keyword(s):  
Analytical Method ◽  
Kinematic Analysis ◽  
Visual Basic ◽  
Geometric Method ◽  
Kinematics Analysis ◽  
Kinematic Chains ◽  
Computer Aided ◽  
Parameterized Model ◽  
Moving Platform ◽  
Analysis System

The 3-RRRS mechanism (RRRS refers to kinematic pairs of a branched chain consisting of three R pairs (Rotational pairs) and one S pair (Spherical pair), successively) is used between a moving platform and a static platform, through which six-dimensional motion of the moving platform relative to the static platform can be achieved. Selecting six independently drivable joints from nine active joints makes it problematic to deal analytically with the kinematics of the 3-RRRS mechanism. In this article, a novel computer-aided geometric method for kinematic analysis is developed. This method can automatically detect the independently drivable joints for arbitrary kinematic chains. This method can be easily implemented compared to the analytical method of the forward kinematics. Based on the constraint relationship of the 3-RRRS mechanism, a general 3-RRRS mechanism digital model is built in the SolidWorks Application Program Interface embedded Visual Basic environment, in which the platform sizes and active driving angles are driven by the parameterized model, to make the moving platform move to the corresponding pose. After the pose of the moving platform is confirmed, the coordinate system is built in a preliminary sketch. The parameters are measured by the SolidWorks measuring functions, and the pose of the moving platform is obtained by combining homogeneous matrices. Using the computer-aided geometric method, the detailed kinematics formula is not required. The accuracy and efficiency of the computer-aided geometric method were assessed with some examples of kinematic analysis for the 3-RRRS mechanism. The results showed that the proposed method obtained competitive precision and calculation time to the analytical method and is beneficial as a convenient solving process. By using Visual Basic programming, a reachable poses analysis of the mechanism can be merged into the kinematics analysis system of the computer-aided geometric method. The computer-aided geometric method could be widely applied to kinematics analysis of mechanisms.

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