Stiffness Design for a Spatial Three Degrees of Freedom Serial Compliant Manipulator Based on Impact Configuration Decomposition

2012 ◽  
Vol 5 (1) ◽  
Author(s):  
Dongming Gan ◽  
Nikos G. Tsagarakis ◽  
Jian S. Dai ◽  
Darwin G. Caldwell ◽  
Lakmal Seneviratne
Keyword(s):  
Degrees Of Freedom ◽  
General Procedure ◽  
Joint Torque ◽  
End Effector ◽  
Joint Torques ◽  
Serial Manipulators ◽  
Stiffness Design ◽  
Compliant Joint ◽  
The Impact ◽  
Three Degrees Of Freedom

This paper proposes a method of stiffness design for a spatial Three Degrees of Freedom (3DOF) serial compliant manipulator with the objective of protecting the compliant joint actuators when the manipulator comes up against impact. System dynamic equations of serial compliant manipulators integrated with an impact model are linearized to identify the maximum joint torques in the impact. Based on this, a general procedure is given in which maximum joint torques are calculated with different directions of end-effector velocity and impact normal in the manipulator workspace based on a given magnitude of end-effector velocity. By tuning the stiffness for each compliant joint to ensure the maximum joint torque does not exceed the maximum value of the actuator, candidate stiffness values are obtained to make the compliant actuators safe in all cases. The theory and procedure are then applied to the spatial 3DOF serial compliant manipulator of which the impact configuration is decomposed into a 2DOF planar serial manipulator and a 1DOF manipulator with a 2DOF link based on the linearized impact-dynamic model. Candidate stiffness of the 3DOF serial compliant manipulator is obtained by combining analysis of the 2DOF and 1DOF manipulators. The method introduced in this paper can be used for both planar and spatial compliant serial manipulators.

Stiffness Design for Compliant Manipulators Based on Dynamics Analysis of the Impact Configuration

2011 ◽  
Author(s):  
Dongming Gan ◽  
Nikos G. Tsagarakis ◽  
Jian S. Dai ◽  
Darwin G. Caldwell
Keyword(s):  
Joint Stiffness ◽  
Joint Torque ◽  
Dynamics Analysis ◽  
End Effector ◽  
Joint Torques ◽  
Maximum Value ◽  
Stiffness Design ◽  
Compliant Joint ◽  
Compliant Actuators ◽  
The Impact

This paper presents a study on setting the joint stiffness for compliant robots in order to protect the actuators when the arm comes up against impact. System dynamic equations of compliant manipulators integrated with impact model are linearized to identify the maximum joint torques in the impact. Based on this, different directions of end-effector velocity and impact normal in different configurations in the robot workspace are calculated based on a given magnitude of end-effector velocity. By tuning the stiffness for each compliant joint to ensure the joint torque does not exceed the maximum value of the actuator, candidate stiffness values are obtained to make the compliant actuators safe in all cases when the robot end-effector moves with a velocity within the fixed magnitude value used in the calculation. The theory and procedure are firstly laid and demonstrated in a 1-DOF planar manipulator, then the work is applied to a 2-DOF compliant manipulator and the candidate stiffness is obtained based on the method.

scholarly journals Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

2017 ◽  
Vol 31 (9) ◽  
pp. 814-826 ◽  
Author(s):  
Natalia Sánchez ◽  
Ana Maria Acosta ◽  
Roberto Lopez-Rosado ◽  
Arno H. A. Stienen ◽  
Julius P. A. Dewald
Keyword(s):  
Lower Extremity ◽  
Degrees Of Freedom ◽  
Joint Torque ◽  
Motor Impairments ◽  
Lower Extremity Weakness ◽  
Joint Torques ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Hip Extension ◽  
Flexion And Extension

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture.

DYNAMIC PROPERTIES OF THE ELECTROMECHANICAL SYSTEM DAMPED BY AN IMPACT ELEMENT WITH SOFT STOPS

2014 ◽  
Vol 06 (02) ◽  
pp. 1450016 ◽  
Author(s):  
MAREK LAMPART ◽  
JAROSLAV ZAPOMĚL
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Electric Circuit ◽  
Response Characteristic ◽  
Electromechanical System ◽  
Frequency Response Characteristic ◽  
Impact Element ◽  
The Impact ◽  
The Mathematical Model ◽  
Three Degrees Of Freedom

The main aim of this paper is to focus on analysis of the dynamic properties of the electromechanical system with an impact element. This model is constructed with three degrees of freedom in the mechanical oscillating part, two translational and one rotational, and is completed with an electric circuit. The mathematical model of the system is represented by three mutually coupled second-order ordinary differential equations. Here, the most important nonlinearities are: stiffness of the support spring elements and internal impacts. Several important results were obtained by means of computational simulations. The impacts considerably increase the number of resonance peaks of the frequency response characteristic. Character of the system motion strongly depends on the width of clearances between the impact body and the rotor frame and changes from simple periodic to close to chaotic or to periodic with a large number of ultraharmonic components. For a suitably chosen system parameters, a significant damping effect of the impact element was observed.

A new parallel wrist using only revolute pairs: the 3-RUU wrist

Robotica ◽  
2001 ◽  
Vol 19 (3) ◽  
pp. 305-309 ◽  
Author(s):  
Raffaele Di Gregorio
Keyword(s):  
Explicit Form ◽  
Kinematic Analysis ◽  
Degrees Of Freedom ◽  
Geometric Errors ◽  
End Effector ◽  
Singular Configurations ◽  
Overconstrained Mechanisms ◽  
Three Degrees Of Freedom

Only one parallel wrist with three equal legs containing just revolute pairs has been already presented in the literature. This parallel wrist is overconstrained, i.e., it involves three degrees of freedom required to orientate the end effector by using repetitions of constraints. The overconstrained mechanisms have the drawback of jamming or undergoing high internal loads when geometric errors occur. This paper presents a new parallel wrist, named 3-RUU wrist. The 3-RUU wrist is not overconstrained. It has three equal legs just involving revolute pairs and actuators adjacent to the frame and uses an architecture (3-RUU) already employed to obtain manipulators that make the end effector translate. The 3-RUU wrist kinematic analysis is addressed. This analysis shows that the new parallel wrist can reach singular configurations (translation singularities) in which the spherical constraint between end effector and frame fails. The singularity condition that makes finding all the 3-RUU wrist singular configurations possible is written in explicit form and geometrically interpreted.

scholarly journals THE FORMATION OF PROFESSIONAL TALENT IN DETERMINATION WITH SEMANTIC ATTITUDE TO INNOVATIONS UNDER THE INFLUENCE OF VARIOUS DEGREES OF FREEDOM IN ACTIVITY

2020 ◽  
Vol 17 (4) ◽  
pp. 91-101
Author(s):  
T.N. Soboleva ◽  
Keyword(s):  
Empirical Data ◽  
Degrees Of Freedom ◽  
The Other ◽  
Psychological Analysis ◽  
Other Hand ◽  
Professional Talent ◽  
The One ◽  
The Impact ◽  
Three Degrees Of Freedom

The article is devoted to the poorly studied problem of the formation of talent in the conditions of different degrees of freedom in activity and the impact on that formation of a person’s conservative and innovative semantic attitudes towards the introduction of new equipment. The main objective of the study is to describe how the conditions of different degrees of freedom in the activity are refracted with internal conditions, which are conservative and innovative semantic attitudes and various talent structures. The study was conducted on a sample of 54 qualified railway drivers using a specialized simulator which allows to simulate three degrees of freedom in the activity. The psychological analysis of the activity revealed seven abilities ensuring the implementation of the activity. Based on empirical data, the article shows that low, medium and high degrees of freedom in activity are manifested in different degrees of productivity. Conservative and innovative semantic attitudes to the introduction of new equipment do not have a significant effect on the productivity of the activity in the conditions of different degrees of freedom. Along with this, depending on the conservative and innovative semantic attitudes, different structures of talent in terms of composition and degree of integration under the conditions of different degrees of freedom in the activity are formed. On the one hand, conservative and innovative semantic attitudes act as internal determinants; on the other hand, low, medium and high degrees of freedom in the activity act as external determinants of the formation of various talent structures.

Dynamic Trajectory Planning for a Three Degrees-of-Freedom Cable-Driven Parallel Robot Using Quintic B-Splines

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Sen Qian ◽  
Kunlong Bao ◽  
Bin Zi ◽  
W. D. Zhu
Keyword(s):  
Trajectory Planning ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Planning Method ◽  
End Effector ◽  
B Spline ◽  
B Splines ◽  
Pick And Place ◽  
Two Factors ◽  
Three Degrees Of Freedom

Abstract This paper presents a new trajectory planning method based on the improved quintic B-splines curves for a three degrees-of-freedom (3-DOF) cable-driven parallel robot (CDPR). First, the conditions of positive cables’ tension are expressed in terms of the position and acceleration constraints of the end-effector. Then, an improved B-spline curve is introduced, which is employed for generating a pick-and-place path by interpolating a set of given via-points. Meanwhile, by expressing the position and acceleration of the end-effector in terms of the first and second derivatives of the improved B-spline, the cable tension constraints are described in the form of B-spline parameters. According to the properties of the defined pick-and-place path, the proposed motion profile is dominated by two factors: the time taken for the end-effector to pass through all the via-points and the ratio between the nodes of B-spline. The two factors are determined through multi-objective optimization based on the efficiency coefficient method. Finally, experimental results on a 3-DOF CDPR show that the improved B-spline exhibits overall superior behavior in terms of velocity, acceleration, and cables force compared with the traditional B-spline. The validity of the proposed trajectory planning method is proved through the experiments.

Kinematic and Kinetic Constraints on Arm, Trunk, and Leg Segments in Target-Reaching Movements

2005 ◽  
Vol 93 (1) ◽  
pp. 352-364 ◽  
Author(s):  
James S. Thomas ◽  
Daniel M. Corcos ◽  
Ziaul Hasan
Keyword(s):  
Degrees Of Freedom ◽  
Neural Control ◽  
Time Course ◽  
Sagittal Plane ◽  
Principal Component ◽  
Joint Torque ◽  
Trunk Flexion ◽  
Joint Torques ◽  
Joint Task ◽  
Task Conditions

We studied target reaching tasks involving not only the arms but also the trunk and legs, which necessitated some trunk flexion. Such tasks can be successfully completed using an infinite number of combinations of segment motions due to the inherent kinematic redundancy with the excessive degrees of freedom (DOFs). Sagittal plane motions of six segments (shank, thigh, pelvis, trunk, humerus, and forearm) and dynamic torques of six joints (ankle, knee, hip, lumbar, shoulder, and elbow) were analyzed separately by principal component (PC) analyses to determine if there was a commonality among the shapes of the respective waveforms. Additionally, PC analyses were used to probe for constraining relationships among the 1) relative magnitudes of segment excursions and 2) the peak-to-peak dynamic joint torques. In summary, at the kinematic level, the tasks are simplified by the use of a single common waveform for all segment excursions with 89.9% variance accounted for (VAF), but with less fixed relationships among the relative scaling of the magnitude of segment excursions (62.2% VAF). However, at the kinetic level, the time course of the dynamic joint torques are not well captured by a single waveform (72.7% VAF), but the tasks are simplified by relatively fixed relationships among the scaling of dynamic joint torque magnitudes across task conditions (94.7% VAF). Taken together, these results indicate that, while the effective DOFs in a multi-joint task are reduced differently at the kinematic and kinetic levels, they both contribute to simplifying the neural control of these tasks.

scholarly journals Cobot with Prismatic Compliant Joint Intended for Doppler Sonography

Robotics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 14 ◽  
Author(s):  
Juan Sandoval ◽  
Med Amine Laribi ◽  
Saïd Zeghloul ◽  
Marc Arsicault ◽  
Jean-Michel Guilhem
Keyword(s):  
Musculoskeletal Disorder ◽  
Doppler Sonography ◽  
Impact Force ◽  
Variable Stiffness ◽  
Safety Performance ◽  
End Effector ◽  
Force Criterion ◽  
Compliant Joint ◽  
The Impact ◽  
Collaborative Robot

This paper deals with a collaborative robot, i.e., cobot, coupled with a new prismatic compliant joint (PCJ) at its end-effector. The proposed collaborative solution is intended for Doppler sonography to prevent musculoskeletal disorders issues. On one hand, the Doppler sonographer’s postures are investigated based on motion capture use during the arteries examination. This study highlighted that configurations adopted by angiologists lead to the musculoskeletal disorder. On the other hand, the proposed PCJ with variable stiffness gives an intrinsic compliance to the cobot handling the probe. This feature allows preserving the human safety when both human and cobot share a common workspace. The effectiveness of the proposed solution is experimentally validated through a 7-DoF Franka Emika robot virtually coupled with the PCJ, during the execution of a trajectory performed during a Doppler ultrasound exam. The impact force criterion is considered as a safety performance.

A Simple Spring-Loaded Inverted Pendulum (SLIP) Model of a Bio-Inspired Quadrupedal Robot Over Compliant Terrains

2018 ◽  
Author(s):  
Hasti Hayati ◽  
Paul Walker ◽  
Terry Brown ◽  
Paul Kennedy ◽  
David Eager
Keyword(s):  
Degrees Of Freedom ◽  
Inverted Pendulum ◽  
Viscoelastic Behavior ◽  
Slip Model ◽  
Runge Kutta Method ◽  
Synthetic Rubber ◽  
Spring Loaded Inverted Pendulum ◽  
Single Support Phase ◽  
The Impact ◽  
Three Degrees Of Freedom

To study the impact of compliant terrains on the biomechanics of rapid legged movements, a well-known spring loaded inverted pendulum (SLIP) model is deployed. The model is a three-degrees-of-freedom system (3 DOF), inspired by galloping greyhounds competing in a racing condition. A single support phase of hind-leg stance in a galloping gait is taken into consideration due to its primary function in powering the greyhounds locomotion and higher rate of musculoskeletal injuries. To obtain and solve the nonlinear second-order differential equation of motions, the Lagrangian method and MATLABb R2017b (ode45 solver), which is based on the Runge-Kutta method, has been used, respectively. To get the viscoelastic behavior of compliant terrains, a Clegg hammer test was developed and performed five times on each sample. The effective spring and damping coefficients of each sample were then determined from the hysteresis curves. The results showed that galloping on the synthetic rubber requires more muscle force compared with wet sand. However, according to the Clegg hammer test, wet sand had a higher impact force than synthetic rubber which can be a risk factor for bone fracture, particularly hock fracture, in greyhounds. The results reported in this paper are not only useful for identifying optimum terrain properties and injury thresholds of an athletic track, but also can be used to design control methods and shock impedances for legged robots performing on compliant terrains.

DeltaBot: A New Cable-Based Ultra High Speed Robot

2003 ◽  
Author(s):  
Saeed Behzadipour ◽  
Robert Dekker ◽  
Amir Khajepour ◽  
Edmon Chan
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Manufacturing Industry ◽  
Design Procedure ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Manufacturing Cost ◽  
End Effector ◽  
Serial Manipulators

The growing needs for high speed positioning devices in the automated manufacturing industry have been challenged by robotic science for more than two decades. Parallel manipulators have been widely used for this purpose due to their advantage of lower moving inertia over the conventional serial manipulators. Cable actuated parallel robots were introduced in 1980’s to reduce the moving inertia even further. In this work, a new cable-based parallel robot is introduced. For this robot, the cables are used not only to actuate the end-effector but also to apply the necessary kinematic constraints to provide three pure translational degrees of freedom. In order to maintain tension in the cables, a passive air cylinder is used to push the end-effector against the stationary platform. In addition to low moving inertia, the new design benefits from simplicity and low manufacturing cost by eliminating joints from the robot’s mechanism. The design procedure and the results of experiments will be discussed in the following.

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