scholarly journals Compliance analysis and lightweight design of a two-degree-of-freedom rotating head

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401983573
Author(s):  
Manxin Wang ◽  
Haitao Liu ◽  
Hutian Feng
Keyword(s):  
Lightweight Design ◽  
Degree Of Freedom ◽  
Established Method ◽  
End Effector ◽  
Adjustment Mechanism ◽  
Operation Conditions ◽  
Hybrid Manipulator ◽  
Deflection Analysis ◽  
Compliance Matrices ◽  
Two Degree Of Freedom

This article presents an approach for the compliance analysis and lightweight design of a two-degree-of-freedom rotating head by considering both gravity and joint/link compliances, which provides a comprehensive understanding on the posture adjustment mechanism of five-degree-of-freedom hybrid manipulator. A kinetostatic analysis is carried out to consider both externally applied wrench imposed upon the end-effector and gravity of all movable components. Then, a deflection analysis integrating both joint and link compliances and formulation of component compliance matrices are completed by using a semi-analytical approach. Finally, the lightweight design of two-degree-of-freedom rotating head is realized by considering the deflection constraints. This approach enables to effectively evaluate the deflections of end-effector caused by both payload and gravity under given operation conditions. Moreover, the established method provides reliable guidelines for the design of two-degree-of-freedom rotating head with superior static rigidities and dynamic behaviors.

Force Capabilities of Two-Degree-of-Freedom Serial Robots Equipped With Passive Isotropic Force Limiters

2015 ◽  
Author(s):  
Meiying Zhang ◽  
Thierry Laliberté ◽  
Clément Gosselin
Keyword(s):  
Human Robot Interaction ◽  
Contact Forces ◽  
Degree Of Freedom ◽  
Practical Implementation ◽  
Robot Interaction ◽  
End Effector ◽  
Serial Robots ◽  
Serial Robot ◽  
Maximum Contact ◽  
Two Degree Of Freedom

This paper proposes the use of passive force and torque limiting devices to bound the maximum forces that can be applied at the end-effector or along the links of a robot, thereby ensuring the safety of human-robot interaction. Planar isotropic force limiting modules are proposed and used to analyze the force capabilities of a two-degree-of-freedom planar serial robot. The force capabilities at the end-effector are first analyzed. It is shown that, using isotropic force limiting modules, the performance to safety index remains excellent for all configurations of the robot. The maximum contact forces along the links of the robot are then analyzed. Force and torque limiters are distributed along the structure of the robot in order to ensure that the forces applied at any point of contact along the links are bounded. A power analysis is then presented in order to support the results. Finally, examples of mechanical designs of force/torque limiters are shown to illustrate a possible practical implementation of the concept.

Seven-Position Synthesis of a Spatial Eight-Bar Linkage by Constraining a TRS Serial Chain

2009 ◽  
Author(s):  
Gim Song Soh ◽  
J. Michael McCarthy
Keyword(s):  
Degree Of Freedom ◽  
Upper Arm ◽  
End Effector ◽  
Serial Chain ◽  
Position Synthesis ◽  
Two Degree Of Freedom ◽  
Puma Robot

In this paper, we use seven-position synthesis to add four TS constraints to a TRS serial chain robot and obtain a two degree-of-freedom spatial eight-bar linkage. The TRS chain is an elbow manipulator, similar to a PUMA robot. We synthesize a TS dyad to connect the base of the robot to its forearm, and then we synthesize three TS dyads that connect the upper arm of the robot to its end-effector. The result is a two degree-of-freedom spatial eight-bar linkage that moves through seven prescribed positions. It consists of a TRST loop supporting a 3TS-RS platform, which we denote as a TS-TRS-3TS spatial linkage. We formulate and solve the design equations for the TS dyads, and analyze the resulting eight-bar linkage. An example demonstrates our results.

Reactionless Two-Degree-of-Freedom Planar Parallel Mechanism With Variable Payload

2009 ◽  
Author(s):  
Alexandre Lecours ◽  
Cle´ment Gosselin
Keyword(s):  
Dynamic Simulation ◽  
Parallel Mechanism ◽  
Reaction Force ◽  
Simulation Software ◽  
Degree Of Freedom ◽  
Dynamic Balancing ◽  
End Effector ◽  
Planar Mechanism ◽  
Two Degree Of Freedom ◽  
Arbitrary Trajectory

A reactionless mechanism is one which does not exert any reaction force or moment on its base at all times, for any arbitrary trajectory of the mechanism. This paper addresses the static and dynamic balancing of a two-degree-of-freedom parallel planar mechanism (five-bar mechanism). A simple and effective adaptive balancing method is presented that allows the mechanism to maintain the reactionless condition for a range of payloads. Important proofs concerning the balancing of five-bar mechanisms are also presented. The design of a real mechanism where parallelogram linkages are used to produce pure translations at the end-effector is also presented. Finally, using dynamic simulation software, it is shown that the mechanism is reactionless for arbitrarily chosen trajectories and for a variety of payloads.

Force Capabilities of Two-Degree-of-Freedom Serial Robots Equipped With Passive Isotropic Force Limiters

2016 ◽  
Vol 8 (5) ◽  
Author(s):  
Meiying Zhang ◽  
Thierry Laliberté ◽  
Clément Gosselin
Keyword(s):  
Human Robot Interaction ◽  
Contact Forces ◽  
Degree Of Freedom ◽  
Practical Implementation ◽  
Robot Interaction ◽  
End Effector ◽  
Serial Robots ◽  
Serial Robot ◽  
Maximum Contact ◽  
Two Degree Of Freedom

This paper proposes the use of passive force and torque limiting devices to bound the maximum forces that can be applied at the end-effector or along the links of a robot, thereby ensuring the safety of human–robot interaction. Planar isotropic force limiting modules are proposed and used to analyze the force capabilities of a two-degree-of-freedom (2DOF) planar serial robot. The force capabilities at the end-effector are first analyzed. It is shown that, using isotropic force limiting modules, the performance to safety index remains excellent for all configurations of the robot. The maximum contact forces along the links of the robot are then analyzed. Force and torque limiters are distributed along the structure of the robot in order to ensure that the forces applied at any point of contact along the links are bounded. A power analysis is then presented in order to support the results. Finally, examples of mechanical designs of force/torque limiters are shown to illustrate a possible practical implementation of the concept.

Analytical Computation of the Actuator and Cartesian Workspace Boundaries for a Planar 2-Degree-of-Freedom Translational Tensegrity Mechanism

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Samuel Chen ◽  
Marc Arsenault
Keyword(s):  
Translational Motion ◽  
Inverse Kinematic ◽  
Degree Of Freedom ◽  
End Effector ◽  
Optimal Mechanism ◽  
High Acceleration ◽  
Pick And Place ◽  
Actuation Scheme ◽  
Two Degree Of Freedom ◽  
Robotic Applications

Tensegrity mechanisms are interesting candidates for high-acceleration robotic applications since their use of cables allows for a reduction in the weight and inertia of their mobile parts. In this work, a planar two-degree-of-freedom translational tensegrity mechanism that could be used for pick and place applications is introduced. The mechanism uses a strategic actuation scheme to generate the translational motion as well as to ensure that the cables remain taut at all times. Analytical solutions to the direct and inverse kinematic problems are developed, and the mechanism’s workspace boundaries are computed in both the actuator and Cartesian spaces. The influence of the mechanism’s geometry on the size and shape of the Cartesian workspace are then studied. Based on workspace size only, it is found that the optimal mechanism geometry corresponds to a relatively large ratio between the length of the struts and the width of the base and end-effector.

scholarly journals Simulation and Optimisation of a Two Degree of Freedom, Planar, Parallel Manipulator

2021 ◽  
Author(s):  
◽  
Ben Haughey
Keyword(s):  
Genetic Algorithm ◽  
Simulation Model ◽  
Cycle Time ◽  
Parallel Manipulator ◽  
Robotic Manipulators ◽  
Degree Of Freedom ◽  
End Effector ◽  
Planar Parallel Manipulator ◽  
Pick And Place ◽  
Two Degree Of Freedom

<p>Development in pick-and-place robotic manipulators continues to grow as factory processes are streamlined. One configuration of these manipulators is the two degree of freedom, planar, parallel manipulator (2DOFPPM). A machine building company, RML Engineering Ltd., wishes to develop custom robotic manipulators that are optimised for individual pick-and-place applications. This thesis develops several tools to assist in the design process. The 2DOFPPM’s structure lends itself to fast and accurate translations in a single plane. However, the performance of the 2DOFPPM is highly dependent on its dimensions. The kinematics of the 2DOFPPM are explored and used to examine the reachable workspace of the manipulator. This method of analysis also gives insight into the relative speed and accuracy of the manipulator’s end-effector in the workspace. A simulation model of the 2DOFPPM has been developed in Matlab’s® SimMechanics®. This allows the detailed analysis of the manipulator’s dynamics. In order to provide meaningful input into the simulation model, a cubic spline trajectory planner is created. The algorithm uses an iterative approach of minimising the time between knots along the path, while ensuring the kinematic and dynamic limits of the motors and end-effector are abided by. The resulting trajectory can be considered near-minimum in terms of its cycle-time. The dimensions of the 2DOFPPM have a large effect on the performance of the manipulator. Four major dimensions are analysed to see the effect each has on the cycle-time over a standardised path. The dimensions are the proximal and distal arms, spacing of the motors and the height of the manipulator above the workspace. The solution space of all feasible combinations of these dimensions is produced revealing cycle-times with a large degree of variation over the same path. Several optimisation algorithms are applied to finding the manipulator configuration with the fastest cycle-time. A random restart hill-climber, stochastic hill-climber, simulated annealing and a genetic algorithm are developed. After each algorithm’s parameters are tuned, the genetic algorithm is shown to outperform the other techniques.</p>

A New Algorithm for the Determination of the Workspace of Complex Planar Kinematic Chains

1995 ◽  
Author(s):  
Pascal Lê-Huu ◽  
Clément M. Gosselin
Keyword(s):  
Numerical Solution ◽  
Inverse Kinematics ◽  
Degree Of Freedom ◽  
Topological Graph ◽  
Kinematic Chains ◽  
Cartesian Space ◽  
Hybrid Manipulator ◽  
Three Degree Of Freedom ◽  
Two Degree Of Freedom

Abstract A new algorithm for the determination of the workspace of complex planar kinematic chains is presented in this paper. This algorithm is completely general since it can deal with any kind of topological graph and any set of parameters defined in a convention of notation. It uses the numerical solution of the inverse kinematics and is based on a wavefront expansion in the Cartesian space. Three examples are presented here, and lead to a dexterity mapping for two two-degree-of-freedom multi-loop manipulators and a three-degree-of-freedom hybrid manipulator.

A 7R-Based, Two Degrees of Freedom Robomech

2000 ◽  
Author(s):  
Ahmad A. Smaili
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Architecture ◽  
Degree Of Freedom ◽  
Robot Arm ◽  
End Effector ◽  
Kinematic Constraints ◽  
Two Degrees Of Freedom ◽  
Synthesis Procedure ◽  
Two Degree Of Freedom

Abstract A robomech is a crossbreed of a mechanism and a robot arm. It has a parallel architecture equipped with more than one end effector to accomplish tasks that require the coordination of many functions. Robomechs with multi degrees of freedom that are based on the 4R and 5R chains have found their way into the literature. This article presents a new, two-degree of freedom robomech whose architecture is based on the 7R chain. The robomech is capable of performing two-function tasks. The features, kinematic constraints, and synthesis procedure of the robomech are outlined and an application example is given.

Two-Degree-of-Freedom Decoupled Nonredundant Cable-Loop-Driven Parallel Mechanism

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Hanwei Liu ◽  
Clément Gosselin ◽  
Thierry Laliberté
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
The Other ◽  
End Effector ◽  
Two Degrees Of Freedom ◽  
Actuation Redundancy ◽  
Rigid Link ◽  
Force Closure ◽  
Two Degree Of Freedom

A novel two-degree-of-freedom (DOF) cable-loop slider-driven parallel mechanism is introduced in this paper. The novelty of the mechanism lies in the fact that no passive rigid-link mechanism or springs are needed to support the end-effector (only cables are connected to the end-effector) while at the same time there is no actuation redundancy in the mechanism. Sliders located on the edges of the workspace are used and actuation redundancy is eliminated while providing force closure everywhere in the workspace. It is shown that the two degrees of freedom of the mechanism are decoupled and only two actuators are needed to control the motion. There are two cable loops for each direction of motion: one acts as the actuating loop while the other is the constraint loop. Due to the simple geometric design, the kinematic and static equations of the mechanism are very compact. The stiffness of the mechanism is also analyzed in the paper. It can be observed that the mechanism's stiffness is much higher than the stiffness of the cables. The proposed mechanism's workspace is essentially equal to its footprint and there are no singularities.

On the Force Capabilities of Two-Degree-of-Freedom Planar Parallel Mechanisms Equipped With Torque Limiters

2013 ◽  
Author(s):  
Wei Chen ◽  
Clément Gosselin
Keyword(s):  
Jacobian Matrix ◽  
Degree Of Freedom ◽  
Joint Torque ◽  
Design Stage ◽  
Parallel Mechanisms ◽  
Human Beings ◽  
Safety Index ◽  
End Effector ◽  
Two Degree Of Freedom ◽  
Insight Into

Safety is the most important issue that should be considered when designing collaborative robots that are intended to physically interact with humans. This paper investigates the force capabilities of two-degree-of-freedom planar parallel mechanisms that are equipped with torque limiters (safety clutches). Joint torque limiting devices are used in these mechanisms in order to limit the forces that the robot can apply to its environment. Such devices aim at ensuring the safety of the human beings interacting with the robot. However, because the torque-limiting devices are mounted at the joints of the robot, the end-effector force capabilities induced by these devices are dependent on the pose (Jacobian matrix) of the robot. Therefore, the characteristics of the torque limiting devices must be determined at the design stage in order to ensure safety and maximize effectiveness in all possible poses of the robot. Two types of planar two-degree-of-freedom parallel mechanisms are considered in this paper. Their architecture is first described. Then, the force capabilities are studied based on the Jacobian matrices. The maximum force that can be applied at the end-effector for given torque limits (safety index) is determined together with the maximum isotropic force (effectiveness) that can be produced. The ratio between these two forces, referred to as the force efficiency, can be considered as a performance index. Finally, some numerical results are proposed which can provide insight into the design of cooperation robots based on parallel architectures.

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